Student Study Guide for Understanding Earth

Prévia do material em texto

Student Study Guide 
for 
Grotzinger, Jordan, Press, and Siever' 
UNDERSTANDING EARTH 
Fifth Edition 
Peter L. Kresan 
University of Arizona, Tucson (retired) 
Reed Mencke, Ph.D. 
University of Arizona, Tucson (retired) 
IS 
W. H. Freeman and Company 
New York 
CHAPTER 1 
Brief Preview of the Study Guide 
for Understanding Earth 
We know from personal exper ience that s tudying geology can be very rewarding . Geology al lows you to look at the Earth around you and unders tand how it c ame to look the way it does . Geology offers scientifically sound explanat ions for geo-
logic disasters such as ear thquakes and volcanoes . We also know that master ing the ideas of 
geology can be chal lenging. The main goal of this Study Guide is to he lp you mee t that chal-
lenge. We think you will f ind the organizat ion of this guide both practical and helpful. Success 
in geology revolves around lecture, as do the study aids in this guide . Specific geology study 
strategies are woven throughout the guide, including how to take great notes and h o w to pre-
pare for exams . Study aids are laid out step by step (see the flow chart on page 3) so you know 
what to do before lecture, during lecture, after lecture, and dur ing e x a m preparat ion. A final 
appendix , H o w to Study Geology, br ings all these aids together into a short course on effec-
tive study strategies. Here ' s how to use these mater ia ls . 
Before Lecture: Preview 
T h e key to taking good notes is to arrive in class with an overview of what will be covered 
a l ready in mind . Tha t way you will a l ready know wha t geologica l p rocesses will be 
exp la ined and wha t key ques t ions the lec ture wil l answer . In lec ture you can actively l is-
ten for answers to those quest ions . Lis tening actively with specific quest ions in mind is guar-
anteed to result in unders tanding more of what is said and including more of the key points 
in your notes . 
The method you use to gain an overview is called Chapter Preview. To m a k e preview-
ing easier for you, we begin each chapter of the Study Guide with the three or four key ques -
t ions the chapter (and its corresponding lecture) will cover. Brief answers des igned to help 
you start thinking about the material are supplied as well. Working with these quest ions and 
answers ahead of t ime will br ing you to lecture ready to listen and take good notes. 
1 
Contents 
Part I: How to Study Geology 
1 Brief Preview of the Study Guide 1 
2 Meet the Authors 4 
3 How to Be Successful in Geology 9 
Part II: Chapter-by-Chapter Study Resources 
1 The Earth Sys tem 19 
2 Plate Tectonics: The Unifying Theory 26 
3 Earth Materials: Minera ls and Rocks 35 
4 Igneous Rocks: Sol ids from Melts 50 
5 Sedimentation: Rocks Formed by Surface Processes 64 
6 Metamorphism: Modificat ion of Rocks by Temperature and Pressure 74 
7 Deformation: Modificat ion of Rocks by Folding and Fracturing 84 
8 Clocks in Rocks : T iming the Geologic Record 94 
9 Early History of the Terrestrial Planets 106 
10 Evolution of the Cont inents 113 
11 Geobiology: Life Interacts with the Earth 124 
12 Volcanoes 133 
13 Earthquakes 144 
14 Exploring Earth 's Interior 155 
15 The Climate Sys tem 166 
16 Weathering, Eros ion, and Mass Wast ing: Interface Between Cl imate and Tectonics 
17 The Hydrologic Cyc le and Groundwate r 191 
18 Stream Transport from Mounta ins to Oceans 201 
19 Winds and Deserts 211 
20 Coastl ines and Ocean Basins 217 
21 Glaciers: The Work of Ice 226 
22 Landscapes : Tectonic and Cl imate Interaction 234 
23 The Human Impact on Earth's Environment 244 
Appendix A: Eight-Day Study Plan 253 
Appendix B: Final Exam Prep 255 
Answers to Practice Exercises and Review Questions 257 
During Lecture: Take an Excellent Set of Notes 
With the basic quest ions in mind, you have a head start on taking good notes. But note tak-
ing is a skill, and as is true with jus t about everything else in life, you get better with pract ice. 
We provide a Note-Taking Checklist: specific actions you can take to get more of the content 
into your notes in a usable form. For many chapters we provide addit ional note- taking tips 
that are specific to the chapter, for example , suggest ions about what to listen for or figures 
you need to review carefully before a part icular lecture. 
After Lecture 
After each lecture we suggest that you schedule two separate sessions: a brief note review and 
improvement session and an Intensive Study Sess ion (lasting at least an hour) dur ing which 
you achieve mastery of the lecture 's content . 
Have y o u c h e c k e d y o u r notes? Note taking is not confined jus t to lecture. Notes can almost 
a lways be improved after lecture. Good students know this and take the t ime after lecture to 
revise their notes . These s tudents also pull addit ional points on every m i d t e r m as their "pay-
check." Specific suggestions in every chapter of the Study Guide will help you improve your 
lecture notes. Often these suggestions focus on adding visual material from the text or sum-
mariz ing what was covered in a form that will be easy to remember . 
In tensive S t u d y S e s s i o n . T h e pu rpose of the intensive study sess ion i s to mas te r the 
mater ia l taught in lec ture . Learn ing and cogni t ive psycho logy teaches us that r ead ing pas -
sively is an inefficient way to learn. You learn best if you spend your study t ime answer ing 
ques t ions . With this method you read port ions of the text as you need them to f ind answers 
to ques t ions . I t ' s a lot l ike the way we learn a new software p a c k a g e on the computer . We 
may not read the software manua l first. Instead we load a p r o g r a m and start us ing it. T h e n 
we go to the manua l (or onl ine help) w h e n we need to f ind out i f we can do s o m e t h i n g wi th 
the p rog ram, or to see how to do it. App ly ing this to the tex tbook, you will learn geo logy 
mos t efficiently by work ing backward from ques t ions , and for each chap te r we sugges t 
ques t ions you can use this way. And often we sugges t o ther gu id ing ques t ions from 
Understanding Earth or the Web site. S imply stated: Do answer ques t ions , d o n ' t " just 
read." You will learn and r e m e m b e r more sc ience m u c h faster. 
Exam Prep 
Doing well on col lege exams is most ly about organization. Effective study requires a sys-
tematic , orderly review. Mos t of your review t ime (about 70 percent) should be spent answer-
ing review quest ions . For each chapter of the text the Study Guide includes a C h a p t e r 
S u m m a r y , Practice Exercises, Review Quest ions, and Web activities. Us ing these features 
is the fastest way to learn and the best way to r emember the information you have learned. 
Study tips for preparing for midterm and final exams, helpful hints that will improve your test-
taking skills on mult iple-choice tests, and information on how to use your personal learning 
style to your advantage dur ing exams may also be found in this section. 
CHAPTER 2 
Meet the Authors of Understanding 
Earth: How to Use Your 
Geology Textbook 
As you begin your study of geology, first take a minute or two to get acquainted with your text. First of all, why do you think i t was wri t ten? Here is what your text authors have to say about why they wrote the book: 
Geology fascinates and excites us. We wrote Unders tanding Earth to help you dis-
cover for yourselves how interesting geology is in its own right and how important 
an understanding of geology has become for making decisions of public policy. What 
can we do to protect people and property from natural disasters such as volcanoes, 
earthquakes, and landslides? How can we use the resources of Earth—coal and oil, 
minerals, water, and air—in ways thatminimize damage to the environment? In the 
end, understanding Earth helps us understand how to preserve life on Earth. 
They add that people tend to enjoy what they do well . They des igned their text to help you do 
well in your geology course . Many aids to learning are built into the text. Le t ' s spend a minu te 
or two talking about these aids and how you can use them. 
Clues and Tools: "What's Important?" 
One of the toughest things about taking an introductory course is that you typical ly have very 
little knowledge of the subject matter. Not only do you have a lot to learn, but you have a lot 
to learn about how to learn it. W h e r e should you focus your at tent ion? W h a t skills and con-
cepts should receive the bulk of your study energy? Aids to help you see wha t material is 
important are built into every page of Understanding Earth. But you have to know where to 
look for these aids and how to use them. Here is a short list of learning aids in your text and 
a few prel iminary thoughts about how to maximize their usefulness. 
4 
Meet the Authors of Understanding Earth: How to Use Your Geology Textbook 5 
/ C h a p t e r Out l ine T h e authors begin each chapter with an out l ine of wha t will be 
covered . To use this tool you need to look actively for c lues . Look at the out l ine for 
Chap te r 1. Each i tem in the out l ine is a c lue to wha t will be covered in the chapter. Try 
turning each i tem in the out l ine into a quest ion. E x a m p l e : Ask yourself, " W h a t is the 
scientific m e t h o d ? " as you read that section. Pay part icular at tention to material in 
the out l ine you f ind intr iguing, surpr is ing, or puzzl ing in any way. Use your surprise 
or puzz lemen t to motivate yoursel f when you read that section. E x a m p l e : Cons ide r 
the i tem "Ear th as a Sys tem of Interact ing Componen t s . " Here there are two poss ibi l -
it ies. You may be puzzled about wha t componen t s the authors are referring to . In that 
case, activate your curiosity. F r ame your surprise in a quest ion such as " W h a t in the 
wor ld are the authors ta lking a b o u t ? " or " W h a t are Ear th ' s interact ing c o m p o n e n t s ? " 
Read wi th the ques t ion in mind . 
/ Chapter S u m m a r y At the end of each chapter a brief summary emphas izes the most 
important ideas of the chapter. This is a very useful resource when you are s tudying for 
an exam. 
Time Saver Tip 
Before reading a chapter of the text, read the Chapter Summary first , referring as 
you do so to the Chapte r Out l ine . The outl ine and summary will provide an overview, 
or organizer, that will greatly accelerate your reading and understanding of material. 
Hint: Also use the Chapter Preview quest ions in this Study Guide . These quest ions are 
specially devised to help you focus on the mos t important material . 
/ Key Terms within the text are printed in bold. You can speed up your reading time by being 
vigilant for key terms. When you see a boldfaced term you know it is the most important 
concept in that paragraph. Focus on understanding the concept. 
/ Photographs Geo logy is a very visual science. Pictures in the text are essential . Use 
them as a "virtual f ield t r ip" to help you learn what part icular rocks and formations look 
like. Perhaps you have heard of or even visited some of the photo sites. E x a m p l e : See 
Figure 1.4 in Chapte r 1. Pay part icular attention to the photographs that are paired with 
schemat ic f igures or d iagrams and refer to them as you read. 
Study Tip 
Having a t ough t ime get t ing yourse l f s tarted in a s tudy sess ion? Use the art to 
motivate you . Start a chap te r s tudy session by scann ing the images and cap t ions 
to f ind mater ia l that interests you . Begin your read ing with this mater ia l . Th i s 
approach works l ike s tar t ing a fire. You genera te a small spark of interest and then 
fan it by b r ing ing in new mater ia l . 
/ Figures (Flowcharts ) F igures are even more important than photographs . F lowchar ts 
such as the rock cycle in Figure 3.26 present key concepts . Pay careful attention to the 
arrows in flow mode ls and ask yourself what drives the process and what products are 
formed. If you are a visual learner, you may even want to study the figures and sketches 
before you start to read. Then read text on an as-needed basis, to clarify the figure. 
/ Figure Stories In geology the story of a part icular feature or area is often instructive. 
In each chapter of Understanding Earth, you will find a "figure story," an illustrated 
vignette that explains an important geologic process or principle. Figure stories contain 
Meet the Authors of Understanding Earth: How to Use Your Geology Textbook 5 
/ C h a p t e r Out l ine T h e authors begin each chapter wi th an out l ine of wha t will be 
covered . To use this tool you need to look actively for c lues . Look at the out l ine for 
Chap te r 1. Each i tem in the out l ine is a c lue to wha t will be covered in the chapter. Try 
turning each i tem in the out l ine into a quest ion. E x a m p l e : Ask yourself, " W h a t is the 
scientific m e t h o d ? " as you read that section. Pay part icular at tention to mater ial in 
the out l ine you find intr iguing, surpr is ing, or puzzl ing in any way. Use your surprise 
or puzz lement to mot ivate yourself when you read that section. E x a m p l e : Cons ide r 
the i tem "Ear th as a Sys t em of Interact ing Componen t s . " Here there are two possibi l -
ities. You may be puzz led about what componen t s the authors are referring to. In that 
case , act ivate your curiosity. F rame your surprise in a quest ion such as " W h a t in the 
world are the authors talking a b o u t ? " or " W h a t are Ea r th ' s interact ing c o m p o n e n t s ? " 
Read wi th the ques t ion in mind . 
/ Chapter S u m m a r y At the end of each chapter a brief summary emphas izes the mos t 
important ideas of the chapter. This is a very useful resource when you are s tudying for 
an exam. 
Time Saver Tip 
Before reading a chapter of the text, read the Chapter S u m m a r y first, referring as 
you do so to the Chapte r Out l ine . The outl ine and summary will provide an overview, 
or organizer, that will greatly accelerate your reading and understanding of material. 
Hint: Also use the Chapter Preview ques t ions in this Study Guide . These quest ions are 
specially devised to he lp you focus on the most important material . 
/ Key Terms within the text are printed in bold. You can speed up your reading time by being 
vigilant for key terms. When you see a boldfaced term you know it is the most important 
concept in that paragraph. Focus on understanding the concept. 
/ Photographs Geology is a very visual science. Pictures in the text are essential . Use 
them as a "vir tual f ield t r ip" to help you learn what part icular rocks and formations look 
like. Perhaps you have heard of or even visited some of the photo sites. E x a m p l e : See 
Figure 1.4 in Chapte r 1. Pay part icular attention to the photographs that are paired with 
schemat ic figures or d iagrams and refer to them as you read. 
Study Tip 
Having a t ough t ime get t ing yourse l f s tarted in a s tudy sess ion? Use the art to 
mot iva te you . Start a chap te r s tudy sess ion by scann ing the images and cap t ions 
to f ind mater ia l that interests you . Begin your read ing with this mater ia l . Th i s 
approach works l ike s tar t ing a fire. You genera te a small spark of interest and then 
fan i t by b r ing ing in new mater ia l . 
/ F igures (Flowcharts ) Figures are even more important than photographs . Flowchar ts 
such as the rock cycle in Figure 3.26 present key concepts . Pay careful attention to the 
arrows in flow mode ls and ask yourself what drives the process and what products are 
formed. If you area visual learner, you may even want to study the figures and sketches 
before you start to read. Then read text on an as-needed basis , to clarify the figure. 
Figure Stories In geology the story of a particular feature or area is often instructive. 
In each chapter of Understanding Earth, you will find a "figure story," an illustrated 
vignette that explains an important geologic process or principle. Figure stories contain 
some data, affording you the opportunity to see how geologis ts interpreted the data and 
the kind of thinking they did to reach a conclusion. 
W h e n reading figure stories ask yourself how the story il lustrates and develops 
what was said in the text. Try to understand the story, then test yourself by summar iz -
ing (out loud if you are an auditory learner) what you learned. Kinesthet ic learners may 
find the figure stories particularly helpful because each provides a real-life example , 
s imilar to a lab or field experience. Visual learners will apprecia te how the carefully 
chosen il lustrations clarify the text. 
/ Color is used in the figures to provide you with clues about how each process works 
and what is involved. Look at Key Figure 1.11 in Chapter 1. W h a t color is used to 
descr ibe processes that utilize heat? W h a t color depicts wate r? Coo l ing? Such cues can 
support learning at a subliminal level of awareness , part icularly if you are a visual 
l ea rner—so be sure to pay close attention to the colors in the f igures! 
/ Clues to rock texture are also cleverly built into the text. Look at F igure 3.23 on page 
64. The igneous rock is shown in shades of black with lots of dots and specks of vary-
ing size. This makes sense given that igneous rock is classified on the basis of the size 
of its crystals . 
W h y are sediments and sedimentary rock depicted as horizontal str ipes? Because 
sediments are formed of earthy materials like sand and mud , and they are originally laid 
down in horizontal sheets and layers. W h y is metamorphic rock depicted with a series 
of distorted and folded bars? Because metamorphic rock is created when other k inds of 
rock are subjected to high pressures and temperatures that may distort the rock into 
folds and its crystals into wavy, foliated bands . Thus the figure speaks to us about what 
the rock looks like as well as the processes that produce it. Pay close attention to these 
and other visual learning clues. 
Questions and Exercises to Help You Learn 
/ Exercises (end of chapter) 
/ Thought Quest ions (end of chapter) 
Psycho log i s t s have f i rmly es tabl ished the impor t ance of act ively learning by ask ing our-
selves ques t ions about the new informat ion we are a t t empt ing to learn and then seeking the 
answers to these ques t ions . W h e n we formula te inquir ies before we start r ead ing new ma t e -
rial , we tend to read in a more act ive m a n n e r s ince we are read ing in search of specific 
answers . This is far more efficient than t ry ing to read about the informat ion you are 
a t t empt ing to learn in a pass ive m a n n e r (passive reading is okay for m a g a z i n e s such as 
Sports Illustrated but not for a col lege sc ience tex tbook) . Th ink of the end-of -chap te r s u m -
mar ies and review ques t ions as your own personal tutor. W h a t does a good tutor d o ? She or 
he asks you ques t ions to get you th inking about the mater ia l . L ike a good tutor, the q u e s -
t ions at the end of each chapter c lue you in to wha t is impor tan t and encourage you to real ly 
mas te r the mater ia l . 
You can use both the Exercises and Thought Quest ions at the end of each chapter of 
Understanding Earth in three different ways . First, use them to preview the chapter. Sk im 
quickly to get an overview of what you will be expected to know after you have read the chap-
ter. Second, seek out answers . Active learning works better than passively reading the text. So 
organize your study t ime around finding an answer to one or more exercises or ques t ions 
using your text as you would a reference book. Third, use the quest ions to review for exams . 
Quiz yourself by trying to answer the quest ions wi thout using the text as your reference. Go 
back to your annotated text to check the accuracy of your answers . The best way to learn from 
a text is to use it as a reference to answer quest ions . 
Meet the Authors of Understanding Earth: How to Use Your Geology Textbook 7 
Text-Marking Strategy for Understanding Earth 
You can m a k e the 30 percent of your s tudy t ime you spend reading the text even more effi-
cient by skillful text mark ing . Mark ing your text as you read is a vital part of learning the 
material and m a y be part icular ly impor tan t if you are a kinesthet ic learner. The act ion of 
marking wil l aid your kinesthet ic memory . If you are a visual learner, you will tend to 
r emember marked sect ions dur ing exams . G o o d mark ing involves both th inking and plan-
ning. First, you think about what is important . Then you plan for e x a m review, dec id ing 
which of the mark ing techniques in the fol lowing table will best he lp you when you return 
to the chapter dur ing exam review. Only then should you mark. T h e authors have a l ready 
marked key t e r m s in bo ld let ters. You will want to add under l ines , numbers , and annota t ions 
in the margin. He re are some brief sugges t ions for how and when to use each kind of mark . 
Useful markings for geology Text-marking tips 
Underl in ing 
Underl ine impor tant points . 1. 
Underl ine to highl ight the key ideas . 
Do pay attention to the key t erms that 
are in boldfaced type in the text. 
2. 
3. 
S u m m a r i z i n g 1. 
Write a brief summary s ta tement of key geology 
processes in your own words in the text margin. 
Use these annota t ions to facilitate exam review. 
3. 
4 . 
Read before you mark. To avoid overusing underlining, set your 
pencil down on the table as you begin to read a paragraph. 
D o n ' t let yourself pick up the penci l until you have read the 
entire paragraph. Stop and think. Then underl ine what you 
consider to be the key point(s) . 
Be selective. Under l ine brief but meaningful phrases or 
key words that will tr igger your memory . Mark jus t enough 
so that you can review without rereading the paragraph. 
Use different color mark ings if i t helps you remember . 
Use your own words . Putt ing ideas into your own words is a 
powerful learning strategy. 
Be neat. This takes t ime. But i t will pay off later w h e n 
you review because your annotat ion will be legible and easily 
read. 
Organize your annotat ions into categories . Grouping ideas into 
categories or bulleted lists makes them easier to remember . 
Use annotat ions during exam review. Avoid rereading the text 
word for word. This will save you a lot of t ime. 
Annotat ing Circled n u m b e r s in the margin indicate sequences , such as the 
processes of the rock cycle. 
Question mark? Put a question mark in the margin to remind 
yourself to ask your instructor about a point you do not understand. 
Asterisks *** Use asterisks to mark ideas of special importance. 
Use asterisks sparingly. Save them for the two or three most vital 
ideas in the entire chapter. 
TQ (test quest ion) Use TQ to mark material in the chapter that 
you know will be covered on the exam. This will remind you to 
pay part icular attention to these i tems. 
Mark ing the text will aid kinesthetic learning. Good text mark ing will aid visual m e m o r y — 
so use caut ion when marking up your text. Mark carefully and selectively. If you mess up the 
text with excessive and illegible markings , you may interfere with some of the good m e m o r y 
aids that are built into the careful design of the text. Remember , a wel l -marked text will m a k e 
e x a m reviewfar more efficient because the marks will focus y o u r a t tent ion on the key ma t e -
rial you need to find and review. If you are worr ied about the impact of marking on your text-
book ' s resale value, be sure to ask your bookstore . Many bookstores have policies that 
encourage effective text marking. 
TRY THIS NOW! 
1. Try underl ining. Choose a section you consider to be important , key material . Read 
the passage several t imes until you are sure you unders tand it. Then mark the passage 
fol lowing the direct ions in the table. 
2. Summar ize a geological process . Choose a section that contains a geological process 
that you think is important enough to be covered on the next exam. Annota te the 
process in the margin in a manne r that will help you r e m e m b e r it. Use the direct ions 
in the table as a guidel ine. 
3. Try some annotat ing. W h e r e would circled numbers be helpful in this chapter? 
Put them in. W h a t material do you need to discuss with your instructor? Mark wi th a 
quest ion mark. 
4. Figure out what is the most important idea in the entire chapter. Put three asterisks 
(***) and a TQ beside that section to insure you master i t before the exam. 
CHAPTER 3 
How to Be Successful in Geology 
(and Just About Any Other 
Challenging Course) 
Academic success is largely a matter of strategy. If you manage your t ime well and study strategically (rather than haphazardly) , you will be successful. In this chapter we discuss successful s tudying strategies for your geology course . T h e best way to use 
this chapter is to read each strategy and then try i t out. We r e c o m m e n d reading one section of 
this chapter each day at the beginning of a new semester. Try the strategy in that section before 
reading further. Fol lowing are the success strategies that will be covered in this int roduct ion: 
• Learning style 
• Chapter preview 
• Note taking 
• Note review 
• E x a m preparat ion 
M a n y other learning strategies and hints about learning specific mater ial are provided 
throughout this Study Guide . Look for them and try out as many of the strategies as poss ible . 
Learn ing strategically initially takes an investment of t ime, but you will find that i t is an 
investment that pays off. S tudying strategies m a k e you more efficient so that you can learn 
more in less t ime. M o r e important , you get more enjoyment out of your learning because you 
know exactly what you are doing. 
Customize Each Strategy to Your Learning Style 
Each of us learns differently. Successful people in any activity tend to be those w h o find a 
way to express their own unique talents in the activity. M o s t of us worry too m u c h about 
9 
10 PARTI C H A P T E R 3 
compet ing . We would do better to seek a way of using our best skills and talents. It is our 
individuali ty that makes us stand out from the pack and b e c o m e a leader. I t is our individu-
ality that leads us to be successful academical ly. We r e c o m m e n d that you spend some t ime 
thinking about your individual style, your s trengths as a learner, and how you prefer to learn. 
He re ' s a s imple beginning . W h i c h m o d e of learning do you prefer to use and use bes t? 
• Visual Learning Visual learners learn by seeing. They often have a good m e m o r y for 
pictures and even words of text. 
• Auditory Learning Audi tory learners learn by l istening. They are good listeners and 
r e m e m b e r best by jus t l istening. 
• Kinesthetic Learning Kinesthetic learners learn by moving. They learn and r emember 
best when they get to practice an activity. 
TRY THIS NOW! 
Put a 1 in the box next to the mode of learning you prefer most strongly, a 2 for your next 
strongest mode , and a 3 beside the mode you think you use least well and least prefer to 
use. Hint: Usually, the mode we prefer is the one we use best. If you are not sure which 
mode you prefer, try taking the Learning Style Inventory online at the University of Arizona 
Learning Center Web site: www.ulc.arizona.edu (click on Self-Assessment) . 
Throughout the Study Guide we will make suggest ions about how part icular strategies might 
work best for those w h o prefer one of the aforement ioned learning styles. 
Make Geology Lecture a High-Priority Activity 
This is step 1 in any strategic approach to course success . Your geology course centers on lec-
ture. Geology is a very content- intensive subject. There ' s so much to learn that instructors 
have to make some difficult decisions about what to cover. Somet imes the faculty in a geol-
ogy department try to address this problem by mapping out required content, perhaps even cre-
ating a core syllabus for instructors to follow. Even then instructors can and do manage to cre-
ate very different courses. In our conversations with other instructors we have been quite 
impressed with the degree to which teaching approaches differ. Two geology instructors may 
use the same text and perhaps even the same basic lecture outl ine yet still teach two very dif-
ferent courses with very different exam questions. Therefore , a t tending lecture is fundamenta l 
to success . Mos t students w h o fail geology do so because they fail to at tend lecture. Just 
at tending will put you far ahead of those w h o fail. 
However , jus t at tending is not enough to ensure that you get an A in geology. Research 
shows that few of us have the attention span to listen actively and take good notes for an entire 
hour. The average note taker gets most of the main points during the first 10 minutes of the 
lecture. Then attention wanders , confusion sets in, and less and less of wha t is said gets into 
the notes . Indeed, most students absorb less than 15 percent of the points that are covered in 
the final 10 minutes of the lecture. This is doubly unfortunate s ince, inevitably, the lecture 
gets to the heart of the topic and the material you will certainly be tested on toward the end. 
W h a t you actual ly do in lecture is fundamenta l to success in geology. You need to be a 
strategist . You need to target your approach to your geo logy cour se on ge t t ing the mos t pos -
s ible out of lec ture . T h a t is our bes t adv ice and we have a d h e r e d to i t r igo rous ly in 
How to Be Successful in Geology (and Just About Any Other Challenging Course) 11 
cons t ruc t ing this gu ide . T h e ent i re S tudy G u i d e i s o rganized a round lecture . Every chapter 
begins wi th wha t you do before lecture for that par t icular chap te r topic . Next c o m e s a sec-
tion wi th t ips on wha t to do during lecture; after that, a checkl i s t to he lp you improve your 
notes after lecture; and finally, lots of exerc ises and review ques t ions to he lp you wi th exam 
prep before y o u r mid te rm. 
In this chapter we present general strategies you can use every day of your course to 
ensure success—al l organized around lecture. 
Before Lecture 
Strategy: Preview the chapter before going 
to the lecture 
To preview a chapter, use the Chapter Preview quest ions. These quest ions are provided at the 
beginning of each chapter of the Study Guide . Read each quest ion, then skim the chapter to 
find the relevant material . Feel free to annotate the brief answers provided for each quest ion. 
The idea is to go to lecture with a general idea of the answers to the quest ions in mind. 
W h y preview? Introductory courses can be difficult. There are lots of new terms, new ideas, 
and new skills during a first-semester geology course. But which ideas are " impor tant"? How 
do you focus your effort in this new and seemingly strange terrain? 
Picture a house under construction. Imagine that the contractor was very careless 
and neglected to construct whole sections of the frame. Finishing the areas lack-
ing a frame would be impossible. Youcan't tack siding onto thin air! This 
metaphor describes your geology lecture. You are the contractor. You need to 
arrive at class with an overview of the lecture already in mind. You have already 
identified what geological processes will be explained and what key questions the 
lecture will answer. Going to class without a frame of key questions is like build-
ing a house with no supporting structure. You will have nothing on which to hang 
the lecturer's main points (information). Without the main points, the details are 
meaningless. As the lecture progresses you are likely to feel increasingly confused 
and bored. By the time the lecturer gets to the most important material, you may 
be completely lost. 
Where do you get the overview? The answer is surprisingly s imple. Just spend a few minutes 
before lecture previewing the chapter that will be covered. Previewing is the method by which 
you generate and mas ter a f ramework for l istening. Here ' s how to do it. 
Step 1. R e a d the prev iew quest ions . You will f ind Chapter Preview ques t ions 
at the beginning of each chapter of the Study Guide . 
Step 2. S k i m the text chapter for answers . Quickly f ind and read only the mate-
rial in Understanding Earth you need to understand and answer the questions. 
Don ' t bog down in details. Don ' t try for complete understanding. Don ' t read the 
whole chapter. Your goal is to a gain just a general understanding of each ques-
tion. Do use the brief answers provided in the Study Guide to cue your reading. 
Step 3 . M e m o r i z e the quest ions a n d brief answers . You may f ind that you 
need to add a few notes to the brief answer. Annota te the answers jus t enough 
to ensure that the answers make sense to you. Annota te in a way that will ensure 
that you memor i ze the quest ions . 
12 PART I C H A P T E R 3 
Before you go to lecture, be sure to spend some t ime previewing. You will find that as little 
as 10 to 15 minutes of t ime spent previewing can make a big difference in how much you under-
stand of the lecture. With the key points already in mind, you can focus in lecture on under-
standing the details. This, in turn, will help ensure you get an excellent set of notes. 
TRY THIS NOW! 
Move immediate ly to the chapter that will be covered in your next lecture. Preview the 
chapter. Then return here to read the next strategy. 
During Lecture 
Strategy: Note-Taking Checklist 
Your basic goal dur ing lecture is to take good notes. The notes should answer the C h a p t e r 
Preview quest ions in depth. To avoid gett ing lost in detai ls , keep the big picture in mind . 
Have a copy of the Chapter Preview quest ions in front of you. Better yet, deve lop pre l imi-
nary answers to the quest ions and commi t them to m e m o r y before the lecture. 
A n o t h e r way to keep the big p ic ture in mind is to b r ing a copy of the key f igure or 
f lowchar t to lec ture to refer to . In many chap te r s we sugges t w h i c h f igure you shou ld have 
handy. 
Dur ing some classes the lecturer may show rock formations and may pass around speci-
men rocks . You will get more out of these demonst ra t ions if you sit c lose to the front of the 
r o o m where you can see the sample rocks as the lecturer discusses them. R e m e m b e r to focus 
on clues the lecturer provides for recognizing a part icular sample in the field. Focus in par-
ticular on the texture of samples and learn to recognize differences, for e x a m p l e , the f ine 
texture of a volcanic rock and the coarse texture of a plutonic rock. 
As you listen to lecture, identify quest ions you need to ask to unders tand the mater ial . 
Try to formulate at least one good quest ion you can ask dur ing every lecture. 
The most important task dur ing lecture is, of course , taking a good set of notes . No te tak-
ing is not easy. It is a skill that improves with practice. Here are a few tips that will he lp you. 
Note-Taking Checklist 
• Organize your notes in a three-ring binder so that you can easily reorganize them. 
• Leave space in your notes for important visual material (f lowcharts, s imple sketches , 
compar ison charts) . To make this easy, employ a double-co lumn or double -page 
note- taking format. Take notes on the r ight-hand page or co lumn. Save the facing 
left page as a "sketch page." 
• Sit near the front of the r o o m — n o t to be a teacher ' s pet but s imply so that you can 
hear and see better! 
• Date each day ' s notes so that you can find material later. 
How to Be Successful in Geology (and Just About Any Other Challenging Course) 
• Take notes in a format that makes the main topics and concepts easy to identify. 
S o m e students accompl i sh this by taking notes in outl ine format. But many other 
approaches are poss ible . Visual learners m a y find i t helpful to highlight main points 
(after class) in color. Another good approach would be to use the quest ions we 
provide in the Chapter Prev iew as heads . You can add them during class or dur ing 
your after-class review session. 
• Keep the preview quest ions in front of you during lecture. Be sure to leave class 
wi th a good answer to each of the preview quest ions . 
• M a r k areas where you need to do fol low-up work wi th your text, instructor, or tutor 
wi th a ques t ion mark in the margin. 
• Indicate poss ible test quest ions by wri t ing TQ (test quest ion) in the left margin 
w h e r e you can easily see it. 
• Wr i te ass ignments in the left co lumn where you can easily find them. After class 
enter the due date in your personal p lanner or calendar. 
TRY THIS NOW! 
Take the note- taking checkl is t with you to your next lecture. Try to follow all the 
suggest ions . After lecture review your notes and check off each point that you actually 
fol lowed. Then return here to read the next strategy. 
Hint: Pho tocopy the checkl is t and use i t for every lecture until all the strategies b e c o m e 
habi ts . Used this way, the checkl is t b e c o m e s a visual record of your progress as a skillful 
note taker. 
After Lecture 
Review Your Notes Immediately 
Good note taking cont inues after the lecture is over. Right after lecture, whi le the mater ial is 
fresh in your mind , is the perfect t ime to review your notes . Review to be sure you unders tood 
the key points and wrote them down in a form that will be easy to review later. 
D o n ' t pos tpone this activity. The best t ime is r ight after lecture before you go to your next 
class or activity. Learn ing experts tell us that mos t of us will forget 80 percent of wha t we 
heard in a lecture by the fol lowing day. On the other hand, if you review right after the lec-
ture, there will have been no interruptions. M u c h of what was said will still be in your short-
term memory . If you missed something , you can probably r e m e m b e r i t and put i t into your 
notes. T h e basic idea of reviewing your notes is to fill in wha t you missed and to add helpful 
visual mater ia l f rom the text. Use the following checklist as a guide. 
Check Your Notes: Have you. . . 
• writ ten legible notes? (Rewri te them if you need to!) 
• identified the important points clearly? (You should have headings in your notes for 
each of the quest ions in the Chapter Preview.) 
• filled in the holes (miss ing mater ia l ) whi le the lecture was still fresh in your short-
term m e m o r y ? 
• marked areas where you don ' t r emember what was said for a fol low-up session with 
your instructor, tutor or study partner? 
• indicated possible test quest ions (TQ) in the marg in? 
• added addit ional visual material? 
• reworked notes into a form that is efficient for your learning style? 
• created a brief big picture overview of this lecture (using a sketch or written outl ine)? 
TRY THIS NOW! 
After the next lecture,review your notes and improve them using the points in the checklist 
as a guide. Check off each point as you complete it. Then return here to read the next 
strategy. Hint: Consider photocopying the checklist so that you can use it repeatedly. 
Intensive Study Session 
Ask yourself questions as you study. Then answer them. 
You should schedule at least one hour after each lecture for intensive study. This can 
occur anyt ime before the next lecture. (Short- term memory is no longer a p rob lem since you 
have comple ted a note review and have good notes.) 
W h y do you need an intensive study session? Think about the house/construct ion exam-
ple that we ment ioned earlier. You need frames before you can add the siding, so you construct 
a frame of quest ions before each lecture. During lecture, you add the s id ing—the answers to 
the quest ions. After lecture, master the ideas and details during an intensive study session. 
Now you have constructed the first story. But this geology course is a skyscraper with 23 
floors (one for each chapter) . Each chapter supports those above it. If you d o n ' t comple te ly 
master a chapter, the next will be more difficult. 
Mas te ry is not gained by jus t reading the text. Mastery occurs as the result of asking 
yourself quest ions and answer ing them. To help you we provide Pract ice Exerc ises and 
Review Quest ions for every chapter of the text. This interactive learning material is specifi-
cally designed to help you master the key concepts of each chapter. T h e greater the number 
How to Be Successful in Geology (and Just About Any Other Challenging Course) 
of these exercises and quest ions you can work into your intensive study sessions early in the 
course, the easier subsequent chapters will be . Plan to spend the majority of your study t ime 
(70 percent) on these exercises and quest ions . 
Use your text as a reference. Read it as needed to answer quest ions and master material . 
When you read, read efficiently. Read with purpose and read to find answers to quest ions . 
Hint: To use your text effectively you must know it like the back of your hand. Carefully read 
Part I, Chapte r 2, H o w to Use Understanding Earth in this guide. 
TRY THIS NOW! 
Each chapter of the Study Gu ide contains a section titled Intensive Study Sess ion. 
Turn now to the chapter you are currently working on and try out its Intensive S tudy 
Session mater ial . Do enough to get a feeling for how Intensive Study Sess ion 
works. Then return here and read the next section. 
Exam Prep 
Materials in this section are mos t useful during your preparat ion for mid te rm and final exam-
inations. For opt imal per formance , mid te rm preparat ion should begin about eight days before 
the exam (see the E ight -Day Study Plan in Appendix A) . The basic idea is a systematic 
review of mater ial divided into short study sessions. 
Tips for Preparing for Geology Exams 
• Use the clues your instructor has provided in lecture about what is important. Even when 
a depar tment agrees on a c o m m o n core of material (a very rare occurrence), each 
instructor carves out a course that is unique, has a particular character or flavor, and has 
distinct areas of emphasis . Your instructor is the ult imate guide on what is important. 
• Be sure you k n o w the format of the exam. Mult iple choice? True- fa l se? Essay? 
Thought p rob lems? 
• Review your notes marked TQ (test quest ion) . 
• Ask your instructor if e x a m s are available from the previous semester. Review them 
to check the format of ques t ions , see what areas of content are stressed, and find out 
what types of p rob lem solving are included. D o n ' t m a k e the mis take of assuming 
that the same quest ions will be asked this semester. 
• Be sure to at tend review sessions if they are offered. 
• If you have tutors , preceptors , supplementa l instruction leaders, or other peer helpers 
w h o have taken the class , ask for their suggest ions about prepar ing for the exam. 
• O n c e you are clear about the nature of the exam, begin your review. Conduc t review 
in an orderly, systematic manner that focuses on all the important material . T h e Eight-
D a y Study P lan (Append ix A) is a good mode l for an orderly review. 
Test Taking 
In every col lege exam, a number of students know the mater ial yet fail the test because they 
get anxious , panic , and freeze up. We have found over the years that the best way to ove rcome 
or avoid test anxiety is by coming to the test well prepared and confident and by work ing 
strategically on the test. E x a m prep will not be a p roblem if you use the mater ia ls provided 
for this purpose in this Study Guide . In this section, we will suggest strategies to try out dur-
ing your exam. You may want to return to this section a day or so before your exam. 
Test-Taking Tips for Different Learning Styles 
Visual Learners 
• Use writ ten direct ions. 
• W h e n you get stuck on an i tem, close your eyes and picture f lowcharts , pictures , 
f ield exper iences , or text. 
Auditory Learners 
• Pay attention to verbal direct ions. 
• Repea t writ ten direct ions quietly to yourself (moving your lips should be enough) . 
• If you get stuck, r e m e m b e r the lecturer 's voice cover ing this section. 
Kinesthet ic Learners 
• W h e n you get stuck, move in your chair or tap your foot to tr igger your memory . 
• Feel yourself doing a lab procedure . 
• Sketch a flowchart to unlock the memory of a process . 
Many exams are in mult iple-choice format. Here are some tips to max imize your per-
formance on mult iple-choice quest ions . 
Test-Taking Tips for Multiple-Choice Exams 
10 . A n s w e r the quest ions you k n o w first. Flag i tems where you get s tuck and c o m e 
back to them later. Often you will f ind the answer you are looking for e m b e d d e d in 
another, easier quest ion. 
9. Try to a n s w e r the i tem without looking at the opt ions . Then check to see i f your 
answer matches any of the opt ions. 
8. El iminate the opt ions . Treat each alternative answer as a t rue- fa lse i tem. If "false," 
e l iminate it. 
7. Use c o m m o n sense. Reasoning is more reliable than memory . 
6. Under l ine key w o r d s in the s tem. This is a good strategy w h e n you are stuck. 
I t may help you focus on what quest ion is really being asked. 
5. If two alternatives look similar, i t is likely that one of t hem is correct . 
4. A n s w e r all quest ions . Unless points are being subtracted for wrong answers (rare), 
i t pays to guess when you ' r e not sure. Research indicates that the i tem with the most 
words in the middle of the list is often the correct i tem. But be caut ious . Your professor 
may have read the research, too! 
How to Be Successful in Geology (and Just About Any Other Challenging Course) 
3. Do not c h a n g e answers . Particularly when you are guessing, your f i rs t guess is often 
correct. C h a n g e answers only when you have a clear reason for doing so. 
2. If the first i tem is correct , check the last. If i t says "all (or none) of the above," you 
obviously need to read the other alternatives carefully. Miss ing an "all of the above" i tem 
is one of the most c o m m o n errors on a mult iple-choice exam. It is easy to read carelessly 
when you are anxious . 
1 . R E A D T H E D I R E C T I O N S B E F O R E Y O U B E G I N ! 
Final Exam Week 
At the end of each semester, in one or two weeks , you take an exam in each and every course . 
Most of the exams are comprehens ive finals that cover the entire semester. Deal ing with finals 
week successfully is a major chal lenge. Here are some tips that will ensure that you do your 
best work dur ing f inal week . 
Tips for Surviving Finals Week 
Be organized and systemat ic . Use the Final E xa m Prep Worksheet (Appendix B) 
to help you get organized for finals. Use the Eight -Day Study Plan (Appendix A) 
for every course where the final exam will be an important factor in determining 
your grade. 
Stick to priorit ies . Say no to dis tract ions. 
Build in m o m e n t s of re laxat ion. Take regular short breaks , exercise, and get enough 
sleep. 
Be confident. By now you have built up a good set of study habits . You are a 
competent learner. 
Organizing for f inal exams can be quite a chal lenge. As with any big project, spending 
organizing t ime up front will pay big dividends. Modify the suggest ions in the Final E x a m 
Prep Worksheet to f i t your personal situation and needs . 
We wish you success! 
CHAPTER 1 
The Earth System 
• H o w was Earth 's size first measured and what is Earth 's topographic relief? 
Brief answer : Eratosthenes measured the c i rcumference of the Ear th somet ime around 
250 B.C. F igure 1.2 shows how. Key Figure 1.3 shows Ear th ' s topography with respect 
to sea level. The sense of scale provided by Key Figure 1.3 is very important . 
• W h a t is Earth 's internal s tructure and compos i t ion? 
Brief answer: The crust, mantle, and core are the major concentric layers within the 
Earth. These layers and their subdivisions are thought to represent changes in 
composit ion and in physical state (solid versus liquid). Preview Figures 1.5, 1.7, and 
Key Figures 1.8 and 1.11. 
• W h a t are the m a j o r c o m p o n e n t s of the Earth Sys tem? 
Brief answer: Earth System Figure 1.10 illustrates Earth as a sys tem of interact ing 
componen t s , including the a tmosphere , hydrosphere , b iosphere , and interior. 
• W h a t were s o m e key events in the history of the Earth? 
Brief answer: Figure 1.13 presents the highl ights . Focus on the connect ions be tween 
geologic and life history. 
During Lecture 
This will be your very first lecture for this course. Get off to a good start. Arrive 10 minutes early. 
Find the best seat in the house: close to the front of the room, where you can hear the lecture and 
see the slides. This section is referred to by some as the "A section." Quite apt, since there really 
is a correlation between where you sit in a lecture hall and the grade you are likely to receive. 
Test this out. Try sitting in different locations the first week. Notice where it is easiest to con-
centrate and where it is most difficult. In many lecture halls the back row is the worst place to be. 
It is the location chosen by students who arrive late and leave early. It may even be noisy. Always 
feel free to change locations if your view is impeded by projection equipment or if you can ' t hear 
because of the whispered conversations of other students. Talk to your instructor if you need to. 
Okay, you have good seat. Wha t can you do while you wait for lecture to begin? 
• Mot ivate yourself to want to listen to this lecture. Open your text to Chapte r 
1. T h u m b through the chapter. Take a good look at the photos and figures. 
Look for topics that interest you. Chapter 1 is loaded with visual material that 
should make i t easy to f ind subjects of interest. Ask yourself wha t you would 
like to know about this chapter. Wha t would you ask your teacher if this were 
a one-on-one tutorial? Finally, try to think of some exper ience you have had 
that relates to this chapter. M a y b e you visited a p lanetar ium or read a catchy 
version of the formation of the universe like Cosmic Comics by Italo Calv ino . 
Or m a y b e you saw a volcano on your last vacation. Actively look for exper i -
ences to hook your interest and to connect you personal ly with course infor-
mat ion. Notice that the more you look at the chapter and the more you let 
yourself think about the pictures, the more your interest bui lds . Five minu tes 
should be enough to get your "motivat ional eng ine" turned on and h u m m i n g . 
• Prepare your mind for learning. Master football players w a r m up by running, 
stretching, and passing the football. Master learners warm up by focusing their 
attention on what will be covered during lecture. Spend a minute or two look-
ing over the Chapter Preview quest ions. Try to anticipate how these quest ions 
will be answered in lecture. If you have t ime, read the Chapter S u m m a r y for 
Chapter 1. W h e n you preview, the goal is not to learn the material but merely 
to formulate quest ions that you expect to be answered during the lecture. With 
quest ions in mind you are ready to take notes. 
Learning Tip 
Do a learning warm-up before every lecture. Arrive 10 minutes early. Ant ic ipate 
quest ions that will be answered in lecture. 
The Earth System 21 
Check Your Notes: Have you. . . . 
• added a s imple sketch or two to clarify the key points? Hint: Try sketching your 
personal version of how convect ion drives plate tectonics based on Figure 1.11. M a k e 
i t s imple—someth ing you wil l easily picture and remember . 
• written a brief (one-paragraph) summary of the mos t important concept you learned 
from this lecture? Feel free to use your notes and figures in your text as needed. 
Reviewing preview quest ions may help . 
You will spend some of your s tudy t ime reading Understanding Earth, part icularly sect ions 
of the text that are emphas ized in lecture. The text is loaded with tools and clues to help you 
learn. You will find our suggest ions about how to take advantage of these learning aids in Part 
I , Chapter 2, Mee t Your Authors , in this Study Guide . 
Web Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Check out the Web site to get an idea of the study aids that are available there. You will find 
Concept Review, Web Review Quest ions , Graded Quizzing, Online Review Exercises, and 
Flashcards (to help you learn new terms). The Chapter 2 Onl ine Review Exercise: Identify the 
Plate Boundaries is a good review of plate tectonics; use it for both Chapter 1 and Chapter 2. 
Exam Prep 
Materials in this section are most useful dur ing preparat ion for exams. The Chapter S u m -
mary and the Pract ice Exerc ises and Rev iew Quest ions should simplify your chapter 
review. Read the Chapter S u m m a r y to begin your session. It provides a helpful overview 
that should refresh your memory. 
Next, work on the Pract ice Exercises and Review Quest ions . Comple te the exercises 
and questions jus t as you would an exam, to see how well you have mastered this chapter. 
After you answer the ques t ions , score them. Finally, and most important , review each ques-
tion you missed. Identify and correct the misconcept ion(s) that resulted in your answer ing the 
question incorrectly. 
Chapter Summary 
How do geologists study Earth? 
• Field and lab observations, experiments, and the human creative process help 
geoscientists formulate hypotheses (models) for how the Earth works and its his-
tory. A "hypothes is" is a tentative explanation that can help focus attention on 
The man who is afraid of asking is ashamed of learning. 
— D A N I S H PROVERB 
After Lecture 
Review Notes 
The perfect t ime to review your notes is r ight after the lecture whi le the material is still fresh 
in your mind. Review to be sure you observed all the key points and wrote them down in a 
form that will be readable later. As you review, you can polish your notes by adding useful 
visual material and a summary . 
22 PART II C H A P T E R 1 
plausible features and relationships of a working model . If a hypothesis is even-
tually confirmed by a large body of data, it may be elevated to a "theory." 
Theories are abandoned when subsequent investigations show them to be false. 
Confidence grows in theories that withstand repeated tests and are able to pre-
dict the results of new experiments and computer models . 
Howwas Earth's size first measured and what is 
Earth's topographic relief? 
• F igure 1.2 illustrates how Eratosthenes measured Ear th ' s s ize. 
• Ear th ' s topography is measured with respect to sea level. The lowest point in 
the Pacific Ocean is actually deeper than Moun t Everes t rises above sea level; 
see Key Figure 1.3. 
What is Earth's internal structure and composition? 
• Ear th ' s interior consis ts of concentr ic layers dis t inguished by differences in 
composi t ion and physical state (solid versus l iquid) and associated changes 
in density. 
• Ear th ' s crust (continental and ocean) is composed of low-densi ty silicate 
rocks, which are rich in a luminum and potass ium. Refer to Figure 1.7. The 
crust essentially floats on the mant le , like an iceberg floats in water. 
• The mant le is composed of silicate rocks of h igher densi ty than the crust and 
contains more magnes ium and iron. The M o h o is the boundary be tween the 
crust and mant le . 
• The core is thought to be metal l ic , composed mostly of iron and nickel . 
• Seismic waves allow geoscientists to detect the presences of a liquid outer core 
and an inner solid core . Changes ( jumps) in density be tween Ear th ' s major lay-
ers are caused by changes in their chemical composi t ion and can be s tudied 
using seismic waves. 
What are the major components of the Earth system? 
• The major componen t s of the Earth system are c l imate , plate tectonics , and the 
geodynamo . 
• The c l imate system is driven by heat from our Sun and is influenced by the 
hydrosphere , the cryosphere , the b iosphere , and the l i thosphere. 
• The plate tectonic system is primari ly driven by Ear th ' s internal heat, which 
escapes through the convect ion of material in Ear th ' s solid mant le . Tectonic 
plates consist of the l i thosphere, which includes the continental and oceanic 
crust, and the rigid, uppermost mant le . 
• The g e o d y n a m o system involves interactions in the outer core that p roduce 
Ear th ' s magnet ic field. 
• Ear th ' s magnet ic field reverses in polarity (the north and south poles flip) at 
irregular intervals. 
What were some key events in the history of the Earth? 
• Earth formed 4.5 billion years ago . 
• Earliest life forms are found in rocks about 3.5 mill ion years old. 
The Earth System 23 
Practice Exercise 
Answers and explanat ions are provided at the end of the Study Guide . 
Earth's topography 
A. Where is the highest point on Earth relative to sea level? 
B. Where is the lowest topographic point on Ear th? 
C. Relative to sea level, how m u c h lower is the lowest point compared to the highest 
point? 
D. Wha t is the total topographic relief on the Ear th? 
Hint: Refer to page 4 and Key Figure 1.3. 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. What purpose does a scientific hypothesis serve? 
A. It represents a widely accepted explanat ion. 
B. It provides an opportuni ty for feedback and testing. 
C. It serves little purpose as part of the scientific method. 
D. It typically results in unan imous agreement be tween scientists. 
2. Of the following s ta tements about the scientific method, which one is t rue? 
A. A hypothesis that has wi ths tood many scientific tests is called a theory. 
B. The ou tcome of scientific exper iments cannot be predicted by a hypothesis . 
C. For a hypothesis to be accepted, it must be agreed on by more than one scientist. 
D. After a theory is proven to be true, it may not be discarded. 
Hint: Figure 1.1 is an excellent overview of the scientific method. 
3. How did Eratos thenes measure the c i rcumference of Ear th? 
A. He measured the t ime it takes for a sailing ship to appear fully on the horizon. 
B. He measured the difference in the angle of sunlight hitting the Earth at the s u m m e r 
solstice at two different places in Egypt . 
C. He used data logged by Co lumbus . 
D. He measured the change in the posit ion of stars at night at two different p laces in 
Egypt . 
• By 2.7 bill ion years ago, photosynthesis by early plant life produced increasing 
levels of oxygen in Ear th ' s a tmosphere . 
• Only one-half billion years ago animals appeared, diversifying rapidly in an 
explosion of evolution. 
• Life history is marked by periodic mass extinctions. Abou t 65 mill ion years 
ago, d inosaurs were killed off in an extinction event that was caused by a large 
bolide impact . 
• Our species (Homo sapiens) arrived 200 ,000 years a g o — a tiny fraction of the 
4.5-bil l ion-year history of the Earth. 
4. The principle of uniformitarianism can be summar ized by which s ta tement? 
A. The Ear th ' s surface and life change very slowly over t ime. 
B. H u m a n activity has a small but significant effect on the Earth . 
C. The present is the key to the past. 
D. The Earth system is all parts of our planet and their interact ions. 
5. Which of the following internal layers of the Earth is the most mass ive? 
A. crust C. mant le 
B. inner core D. outer core 
Hint: Refer to Figure 1.5. 
6. The crust is 
A. thickest in the cont inents . 
B. thickest in the oceans . 
C. about the same thickness in both the cont inents and oceans . 
D. of a complete ly unknown thickness . 
Hint: Refer to Figure 1.7. 
7. Which of the following e lements is more abundant in the Ear th ' s crust compared to the 
Earth as a whole? 
A. iron C. nickel 
B. magnes ium D. silicon 
Hint: Refer to Key Figure 1.8. 
8 . W h y do geoscientists think tectonic plates move across the Ear th ' s surface? 
A. Centrifugal force of Ear th ' s rotation spins plates across the Ear th ' s surface. 
B. Volcanic eruptions on the seafloor push tectonic plates apart. 
C. Tidal forces drive plate mot ion. 
D. Movemen t of the plates is a result of convect ion in the mant le . 
9. The Ear th ' s magnet ic f ield is caused by 
A. the permanent magne t i sm of the Ear th ' s solid inner core. 
B. the flow of molten iron in the inner core. 
C. the geogdynamo, created by convection in the outer liquid core, and electrical currents . 
D. solar radiation bombard ing the Earth. 
10. Ear th ' s magnet ic poles 
A. reverse at irregular intervals. 
B. consist of four poles. 
C. are generated by a permanent ly magnet ized inner core . 
D. are very stable and do not change . 
The Earth System 25 
11. Convect ion transfers heat (see Key Figure 1.11) by the physical circulation of hot and 
cold matter. H o w does i t work? 
A. Hea ted mat ter rises under the force of buoyancy because it is less dense. 
B. Hot mat ter within the mant le sinks because i t is denser. 
C. Cold matter rises under the force of buoyancy because it is less dense . 
D. Meteor b o m b a r d m e n t acts to stir up the mant le and drive convection. 
12. When did b io logy ' s Big Bang (evolutionary explosion) occur? 
A. about 65 mill ion years ago 
B. about 540 mill ion years ago 
C. about 2200 mil l ion years ago 
D. about 3500 mill ion years ago 
Plate Tectonics: The Unifying Theory 27 
Before Lecture 
This is a part icularly important chapter. Plate tectonics is the major concept that guides mod-
ern geology. Before you attend lecture be sure to spend some t ime previewing the chapter. 
Previewing will greatly increase your unders tanding of the lecture (see the Chapter Preview 
in Part I , Chapter 3, How to Be Successful in Geology) . For an efficient preview use the fol-
lowing quest ions. 
Chapter Preview 
This chapter contains extraordinari ly helpful f igures and photos . The goal is to learn 
how the cont inents and ocean plates can float about the Earth. Focus your Chapter 2 
study time on examin ing the fascinating figures and photos of some of Ear th ' s most 
amazing features. 
• What is the theory of plate tectonics?Brief answer: The theory of plate tectonics descr ibes the movement of l i thospheric 
plates and the forces acting be tween them. It also explains the distribution of many 
large-scale features that result from movemen t s at plate boundar ies : mounta in chains , 
earthquakes, volcanoes , topography of the seafloor, and distr ibution of rock 
assemblages and fossils. Refer to Figure 2 .5 , Ear th ' s l i thosphere is m a d e of moving 
plates, on page 24. 
• What are s o m e of the geologic characterist ics of plate boundar ies? 
Brief answer: Volcanoes and ear thquake activity are concentrated along plate 
boundaries . W h e r e divergent plate boundar ies are exposed on land, subsiding basins 
and volcanism are typical . Mounta in chains form along convergent and transform 
plate boundar ies . I t is impor tant to visualize each major type of plate boundary and 
their locat ions on Earth . Use the following f igures in the text to do so: F igures 2 .5 , 
2.6, 2.7, and 2.8 for divergent plate boundar ies ; Figures 2.5 and 2.6 for convergent 
plate boundar ies ; and Figures 2 .5 , 2.6, and 2.9 for a t ransform boundary. If you have 
seen or lived near the San Andreas , a volcano, or a rift valley, like the Rio Grande in 
New Mexico , start with the actual feature. 
• H o w can the age of the seafloor be de termined? 
Brief answer: A pivotal discovery in the history of plate tectonics was the determination 
of the age of the seafloor us ing magnet ic anomal ies . Figure 2.10 shows how the age 
was determined. 
• H o w is the his tory of plate m o v e m e n t reconstructed? 
Brief answer: Transform boundar ies indicate the direct ions of relative plate movement , 
and seafloor i sochrons reveal the posi t ions of divergent boundar ies in earlier t imes . 
Refer to Figures 2.11 and 2.12. 
• W h a t drives plate tectonics? 
Brief answer: Ear th ' s internal heat creates convect ive currents (flow of rock material 
from hotter to cooler areas) in the mant le . Convect ion, the force of gravity, and the 
existence of an as thenosphere are all important factors in any explanat ion of plate 
movement . Review Key Figure 1.11 to see how convect ion works . 
Vital Information from Other Chapters 
Review Key Figure 1.11 in Chapter 1 to remind yourself how convection drives plate tectonics. 
CHAPTER 2 
Plate Tectonics: 
The Unifying Theory 
From time to time in the history of science, a fundamental concept appears 
that unifies a field of study by pulling together diverse theories and 
explaining a large body of observations. Such a concept in physics is the 
theory of relativity; in chemistry, the nature of the chemical bond; 
in biology, DNA; in astronomy, the Big Bang; and in geology, plate tectonics. 
—UNDERSTANDING EARTH, FRANK PRESS AND RAYMOND SIEVER 
Plate Tectonics: The Unifying Theory 29 
Intensive Study Session 
Set priorities for s tudying this chapter. There is a lot to do , probably more than you will have 
time for in one intensive study session. Set priorities and always do the important things first. 
• Instructor. Pay part icular attention to any exercises r e c o m m e n d e d by your 
instructor dur ing lecture and a lways answer them first . Your instructor is also 
your best resource if you are wonder ing which material is mos t important . 
• Practice Exercises and Review Quest ions . Use the Study Guide Pract ice 
Exercises and Review Ques t ions . Be sure to do Exercise 1 because it involves 
the key information you need to learn in this chapter. 
• Text. Work on your responses to Exercises 2, 4, and 5 and Thought Quest ions 
1, 3, and 6 at the end of Chapte r 2 in the textbook. 
• Web Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Complete the Concept Sel f -Checker and Web Review Quest ions . Pay partic-
ular at tention to the explanat ions of the answers . 
Exam Prep 
Materials in this section are most useful dur ing your preparat ion for exams. The Chapter 
Summary and the Pract ice Exerc ises and Rev iew Quest ions should simplify your chapter 
review. Read the Chapter S u m m a r y to begin your session. It provides a helpful overview 
that should refresh your memory . 
Next, work on the Pract ice Exercises and Review Quest ions . Comple te the exercises 
and questions jus t as you would an exam, to see how well you have mastered this chapter. 
After you answer the ques t ions , score them. Finally, and most important , review each ques-
tion you missed. Identify and correct the misconcept ion(s) that resulted in your answer ing the 
question incorrectly. 
Chapter Summary 
What is the theory of plate tectonics? 
• For over the last century some geologists have argued for the concept of conti-
nental drift because of the j igsaw-puzzle fit of the coasts on both sides of the 
Atlantic, the geological similarities in rock ages and trends in geologic structures 
on opposite sides of the Atlantic, fossil evidence suggesting that continents were 
jo ined at one t ime, and the distribution of glacial deposits as well as other paleo-
climatic evidence. 
There are two important caveats here . First, you need to budget your t ime. Focus 
on very important material , such as the figures we suggested in the preview quest ions . 
You don ' t have t ime to redo all the ar twork in Understanding Earth. Second, the art in 
the text is especial ly well done . It includes many details you cannot easily execute 
in your notes. Also the capt ions in the text are very helpful, so when you are working 
on sketches be sure to refer to the text figure and caption. 
Get off to a good start. Try this idea for Chapter 2 and observe how it works for 
you. Modify it to fit your learning style. 
Web Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Identify the Earth's Plates and Identify the Plate Boundaries are Interactive Exercises wor th 
comple t ing before the f irst lecture on this topic. 
During Lecture 
One goal for the lecture should be to leave the class with good answers to the preview quest ions. 
• To avoid gett ing lost in details, keep the big picture in mind. Chapte r 2 tells 
the story of plate tectonics: Earth 's moving plates, how the plates move, and the 
geological features associated with converging and diverging plate boundar ies . 
Plate tectonics underl ies and explains much about modern geology. In that 
sense, this chapter provides a preview of your entire geology course . 
• Focus on understanding Figure 2.6. It will be helpful to have this figure handy 
during lecture. Annotate the text figures with comments made by your instructor. 
• If you haven ' t already done so, read the discussion of note taking in Part I, 
Chapter 3 , How to Be Successful in Geology. Hint: You can use the Note -
Taking Checkl is t before you go to lecture as a one-minute reminder of wha t 
to do to improve your note- taking skills. After lecture, use it as a quali ty check. 
After Lecture 
Review Notes 
The perfect t ime to review your notes is right after lecture. The following checkl is t conta ins 
both general review tips and specific suggest ions for this chapter. 
Check Your Notes: Have you. . . 
• marked areas where you don ' t r e m e m b e r what was said? Do you need a fol low-up 
session with your instructor, tutor, or study par tner to get what you missed? 
• added visual mater ia l? Example : For the lecture on Chap te r 2, i t is very impor tant 
to dist inguish the difference be tween diverging and converging plates (Figure 2.6). 
You could insert a visual cue about this distinction into your notes . For example , 
the s implest possible representat ion of Figure 2.6 would be two ar rows pointed away 
from each other. You also want to r e m e m b e r that divergence can cause bo th r idges 
and valleys. You could draw a r idge (zigzag lines) and a valley(dropping plates) 
be tween your arrows 
Study Tip: Learn by drawing 
Sketching simplified versions of figures in your notes is a helpful way to learn and 
remember . Visual learners will r emember material best after they look at and study 
a figure. Visual learners learn more if they enrich their notes with visual cues . 
For kinesthetic learners m e m o r y is activated by the act of d rawing , so you learn as 
you look and draw. As you take notes, be sure to leave r o o m so that you can insert 
material later. T h e ul t imate goal is notes you can study from. 
Plate Tectonics: The Unifying Theory 31 
typical ly form a long convergent and t ransform pla te boundar ies . W h e r e 
divergent p la te boundar i e s are exposed on land, subs id ing bas ins and vol-
can i sm are typica l . 
How can the age of the seafloor be determined? 
• The age and relative plate velocity are inferred from changes in the paleo-
magnet ic proper t ies of the ocean floor. 
• Various o ther m e t h o d s are now used to measu re the rate and direct ion of 
plate m o v e m e n t s . Rela t ive pla te speeds in mi l l imeters per year are shown in 
F igure 2 .5 . 
How is the history of plate movement reconstructed? 
• Seafloor i sochrons provide the basis for reconstruct ing plate mot ions for about 
the last 200 mil l ion years . 
• Distinct assemblages of rocks character ize each type of plate boundary. Using 
diagnostic rock assemblages embedded in continents and paleoenvironmenta l 
data recorded by fossils and sedimentary rocks , geologis ts have been able to 
reconstruct ancient plate tectonic events and plate configurat ions. 
What is the engine that drives plate tectonics? 
• Driven by Ear th ' s internal heat, convect ion within the mantle , coupled with the 
force of gravity and the exis tence of a soft zone , called the as thenosphere , are 
important factors in models for how plate tectonics works . 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Characteristics of active tectonic plate boundaries 
Complete the table by filling in the blank spaces and boxes . 
Convergent 
Divergent See Figures 2.5 and 2.9. Transform 
See Figures 2.5, Ocean / Ocean / See Figures2.5, 
Characteristics 2.6, 2.7, and 2.8. Ocean Continental Collision 2.6, and 2.9. 
Examples Japanese islands Himalayas and 
Mar inas Trench Tibetan Plateau 
Aleutian Trench 
Topography oceanic ridge, trench, 
rift valley, island arc 
ocean basins, 
ocean floor features 
offset by transforms, 
seamounts 
offset of creek 
beds and other 
topographic 
features that 
cross the fault 
Volcanism present not 
characteristic 
• In the last half of the twent ie th century the major e lements of the plate tec-
tonic theory were formulated. Start ing in the 1940s, ocean floor mapp ing 
began to reveal major geologic features on the ocean floor. Then the ma tch 
be tween magnet ic anomaly pat terns on the seafloor with the pa leomagne t i c 
t ime scale revealed that the ocean floor had a young geologic age and was 
systemat ical ly o lder away from the oceanic r idge sys tems . T h e concep ts of 
seafloor spreading, subduct ion, and t ransform faulting evolved from these 
and other observat ions . 
• According to the theory of plate tectonics, the Earth 's lithosphere is broken into 
over a dozen moving plates. The plates slide over a hot and weak asthenosphere, 
and the continents, embedded in some of the moving plates, are carried along. 
The assembly breakup of Pangaea (see Figure 2.12) provides a dramatic example 
of how the movement of plates creates geography and geological features such as 
the Himalaya Mountains and even changes climate as land masses travel about. 
(Note Antarctica's location during the late Proterozoic. Would Antarctica have 
been covered with ice at that t ime? What would its climate have been like?) 
What are some of the geologic characteristics of plate boundaries? 
• The re are three major types of boundar ies be tween l i thospher ic p la tes : diver-
gent boundar ies , where pla tes move apart ; convergen t bounda r i e s , whe re 
pla tes m o v e toge ther and one plate often subducts benea th the other ; and 
transform boundaries, where plates slide past each other. Volcanoes, ear thquakes 
and mountains are concentrated along the active plate boundaries . Moun ta ins 
30 PART II C H A P T E R 2 
Exercise 2: Construct a conceptual flowchart or 
diagram illustrating how plate tectonics works 
Construct a conceptual flowchart or d iagram that illustrates modern ideas on how plate tec-
tonics works . Include thorough capt ions or a written descript ion of how it works . Be sure the 
roles p layed by the following important factors are addressed. 
• Ear th ' s internal heat • density differences 
• convect ion • l i thosphere 
• as thenosphere • the push and pull of gravity 
• divergent and convergent boundar ies 
Hints: Refer to pages 1 2 - 1 3 and 37^17 in the text. This is a complex task. 
Break it down into pieces . First, make a sketch for each factor on separate pieces 
of paper. Then ask yourself where (in which Ear th layer) each process operates 
and arrange your sketches accordingly. Finally, try to combine all this material 
into a single chart. 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. The mos t important process in building the ocean floor is 
A. volcanism. C. ear thquake activity. 
B. subduct ion. D. magnet ic reversal . 
2. The younges t ocean crust is located 
A. a long the oceanic r idges. C. around hot spots . 
B. in the oceanic t renches . D. on the abyssal seafloor. 
3. Rates of seafloor spreading today are in 
A. mil l imeters per year. C. meters per year. 
B. cent imeters per year. D. ki lometers per year. 
Hint: Refer to Figure 2 .5 . 
4. Along a transform plate boundary, the two plates 
A. move apart to create a widening rift valley. 
B. are being consumed by subduct ion. 
C. are being forced together to produce a mounta in system. 
D. move horizontally past each other. 
5. The is an example of a divergent plate margin . 
A. East African Rift C. Himalayas 
B. Japan Trench D. San Andreas fault 
6. All the following features mark plate boundar ies except 
A. the Red Sea. C. the Hawai ian Islands. 
B. the San Andreas fault. D. Iceland. 
Hint: Refer to Figure 2.5. 
7. Which of the following features is not associated with a type of active plate bounda ry? 
A. Atlantic coast of North Amer ica C. Gulf of California 
B. nor thwestern North Amer ica D. Himalayas 
8. The name given to the supercontinent that broke up in the Early Jurassic (195 M a ) was 
A. India. C. Laurasia . 
B. Atlantis . D. Pangaea. 
Hint: Refer to Figure 2 .13 . 
Plate Tectonics: The Unifying Theory 33 
9. Mid-ocean r idges , according to the plate tectonic theory, are 
A. p laces where oceanic crust is consumed . 
B. pul l-apart zones where new oceanic crust is produced. 
C. locat ions of plate convergence. 
D. t ransform faults. 
10. The are an example of a coll ision zone be tween two 
pieces of cont inental crust r iding on converging l i thospheric plates. 
A. H ima laya Mounta ins C. Aleut ian Is lands in Alaska 
B. is lands of Japan D. Andes Mounta ins in South Amer i ca 
11. At which type of plate boundar ies are volcanoes least likely to form? 
A. divergent boundar ies C. t ransform boundar ies 
B. convergent boundar ies D. hot spots 
12. Dur ing the early Triassic (237 Ma) , 
A. India col l ided with Asia to form the Himalayan Mounta ins . 
B. the supercont inent Rodin ia formed. 
C. the supercont inent Pangaea was most ly assembled. 
D. the Atlant ic Ocean had already begun to open. 
Hint: Refer to Figure 2 .13 . 
13. South Amer i ca lay closest tothe South Pole during the 
A. late Proterozoic (650 Ma) . C. late Jurassic (152 Ma) . 
B. last 65 mill ion years . D. early Devonian (390 Ma) . 
Hint: Refer to Figure 2 .13 . 
14. The significance of the magnet ic anomaly pat terns discovered in associat ion with the 
seafloor was that the anomaly pat terns 
A. could be matched with the magnet ic reversal chronology to establish an es t imated 
age for the seafloor. 
B. provided evidence for mant le convect ion, a driving mechan i sm for plate tectonics. 
C. a l lowed geomagnet i s t s to reconstruct the supercont inent Rodinia . 
D. represented absolute proof that the seafloor was spreading apart . 
Hint: Refer to Figure 2.10. 
15. The oldest rocks on the seafloor are about 
A. 20 mil l ion years old. C. 500 mill ion years old. 
B. 200 mill ion years old. D. 1 bill ion years old. 
Hint: Refer to Figure 2.12. 
16. T h e oceanic crust 
A. b e c o m e s progressively younger away from the oceanic r idges. 
B. b e c o m e s progressively older away from the oceanic r idges. 
C. is the s ame age virtually everywhere . 
D. ranges in age from Jurassic to Precambr ian . 
17. Volcanic island arcs like the Japanese islands are associated with 
A. convergent boundar ies . C. t ransform boundar ies . 
B. divergent boundar ies . D. a chain of hot spots . 
Hint: Refer to Figure 2.6. 
18. Rift valleys are associated with 
A. convergent boundar ies . C. t ransform boundar ies . 
B. divergent boundar ies . D. active continental margins . 
Hint: Refer to Figure 2.6. 
34 PART II C H A P T E R 2 
19. With what tectonic activity is a rift valley usually associa ted? 
A. subduct ion C. continental rupture 
B. movemen t on a transform fault D. cont inental coll is ion 
20. Magnet ic anomal ies in the seafloor are caused by 
A. magnet ic reversals recorded by lavas erupted at oceanic spreading centers . 
B. changes in the a tomic structure of minerals in response to changing ocean depth. 
C. the me tamorph i sm of deep-sea sediments . 
D. the heating up of subducting oceanic lithosphere as it plunges deeper into the mantle . 
Hint: Review pages 13 -14 and Figure 2.10. 
2 1 . W h e r e do the plate-driving forces originate? 
A. Tectonic plates are passively dragged by convect ion currents . 
B. Gravity pulls and/or pushes old, cold, heavy l i thosphere. 
C. Injection of m a g m a from the mant le pushes the l i thosphere apart. 
D. Ear thquakes cause the plates to move . 
22 . Ear th ' s l i thosphere can be character ized as 
A. having an average thickness of about 100 km. 
B. including the crust and upper mant le . 
C. being solid and above the as thenosphere . 
D. all of the above. 
CHAPTER 3 
Earth Materials: 
Minerals and Rocks 
Before Lecture 
Chapter Preview 
• W h a t is a mineral? 
Brief answer: A naturally occurring inorganic, crystal l ine solid. 
• H o w are rocks related to minera ls? 
Brief answer: Minerals are the building blocks of rocks . Study Figure 3.21 (p. 35) . 
• H o w do a t o m s combine to form the crystal s tructure of minera l s? 
Brief answer: How atoms combine (chemically bond) depends on the electronic charge 
on their ion, the size of the ion, and the degree to which the bond is ionic or covalent. 
• W h a t is the a tomic structure of minerals? 
Hint: See Figures 3.3 (halite), 3.8 (graphite and d iamond) , 3.9 (silicates), 3.10 
(calcite), and 3.15 (mica) . 
• W h a t are the m a j o r rock-forming minera l s and their physical propert ies? 
Brief answer: The major minerals are silicates, carbonates, oxides, sulfides, and sulfates. 
Diagnostic properties include hardness, cleavage, luster, color, density, and the shape of 
the crystal. 
• W h a t determines the propert ies of rocks? 
Brief answer : Mineral content and texture. 
• W h a t are the three types of rocks and h o w are they formed? 
Brief answer: Igneous , sedimentary, and metamorph ic rocks . 
• H o w do the three types of rocks interact with each other via plate tectonics , 
the c l imate sys tem, and the rock cycle? 
Brief answer: Refer to Figures 3.22, 3 .23, 3.25, and 3.26. 
• W h a t is an ore minera l? 
Brief answer: Mineral deposi ts b e c o m e ore deposi ts when they are rich and valuable 
enough to mine economical ly . 
• H o w do ore deposi ts of meta l -bear ing minera l s form? 
Brief answer: Many metal ore deposi ts are formed by magmat ic and hydro thermal 
processes that are closely l inked to modern and ancient plate tectonic boundar ies . 
Refer to Figure 3.28. 
Previewing Tips 
Tip 1 
To preview a chapter quickly, focus on the figures. It is often poss ible to get a good 
overview jus t by examining the f igures and capt ions . Note that preview ques t ions often 
refer you to specific figures. As little as 5 or 10 minutes previewing the figures before 
lecture will improve the quality of your note taking. 
Tip 2 
The more material a chapter contains the more important it b e c o m e s to chunk 
material into a schema that is meaningful to you and is s imple enough to remember . 
Example : Think of Chapte r 3 as answer ing three simple ques t ions : (1) W h a t is a 
minera l? (2) H o w is a mineral related to a rock? (3) H o w do the three k inds of rocks 
interact with each other in the system called the rock cycle? If you can r e m e m b e r those 
three quest ions and use them to tie the details of the chapter together, you are likely 
to f ind that the chapter suddenly seems much simpler and that the material seems much 
easier to remember . Hint: Read the section on Previewing in Chapte r 3 of Part I of 
this Study Guide . 
Earth Materials: Minerals and Rocks 37 
Minerals are the alphabet and rocks are the words. 
— T O M DILLEY 
Vital Information from Other Chapters 
• R e v i e w Figure 1.8 (the relative abundance of e lements in the whole Earth 
compared to that of e lements in Ear th ' s crust) on page 9 of the textbook. 
• Plate tectonic processes drive the formation of igneous and metamorphic rocks 
plus the burial sediments . It will be particularly useful to review Chapter 2, espe-
cially the text and figures regarding converging and diverging plate boundaries. 
During Lecture 
Do a learning warm-up . Arr ive early. Look for pictures in the text that catch your interest. 
Look over the preview quest ions and keep them handy for easy reference. 
Your bas ic goal dur ing lecture is to take good notes. The notes should contain in-depth 
answers to the preview quest ions . To avoid gett ing lost in details, keep the "big p ic ture" in 
mind. Chapte r 3 explains how rocks are built out of minerals and how minerals are built out 
of a toms. 
Keep in mind the typical geologic condi t ions needed for the formation of the three major 
rock types . This is nicely summar ized in Figure 3.22. Open your book to this figure and put 
a bookmark there. You w o n ' t have t ime during lecture. 
The lecturer may show slides of mineral crystals and may pass around specimens of par-
ticular minerals and rocks . You will get more out of the samples if you sit c lose to the front 
of the room where you can see the samples as they are discussed. R e m e m b e r to focus on clues 
the lecturer provides for recogniz ing a part icular sample in the field. As you listen, try to for-
mulate at least one good quest ion you can ask dur ing the lecture. 
The important thing is not to stop questioning. 
— A L B E R T EINSTEIN 
Lecture Tip: Rock texture 
The lecturer may show or pass around samples of the three types of rocks to help 
you learn how they differ. Pay part icular at tention to the crystal or grain size (texture) 
and to the presence or absence of layering, fossils, and pat terns produced by the 
alignment of minera ls . You will have a better chance of seeing the samples if you sit 
at the front of theroom. 
After Lecture 
Review Notes 
Right after lecture whi le the material is fresh in your mind is the perfect t ime to review your 
notes. Review to be sure you unders tand all the key points and wrote them down in a form 
that will be readable later. O n e good check is that your notes should provide detailed answers 
Earth Materials: Minerals and Rocks 39 
Everything you do in life is worth infinite care and infinite effort. 
— J . D . M C D O N A L D 
Here are a few suggestions for how you might do an intensive study session for this chapter. 
• Review Quest ions . Start your study session by determining how much you 
already know. Try answer ing the Study Guide Review Quest ions . Not ice that 
you can check the answers to these quest ions at the end of the Study Guide . 
Often we provide some addit ional information with an answer. The Rev iew 
Quest ions are a great way to start s tudying because trying to answer them will 
help you focus on what you need to work on. Afterward you can go back and 
read the text concern ing any points you missed. 
• Practice Exercises . Immedia te ly before the Rev iew Quest ions you will find 
Practice Exercises . These exercises a lways focus on some key material that 
you will learn best by an interactive approach that requires you to think. For 
Chapter 3 the exercises deal with unders tanding how the structure of a minera l 
determines its physical propert ies . 
• Text. Work on Exercises 5 and 12 at the end of the chapter. Also work on 
Thought Quest ions 4, 8, 11 (see Figure 3.26), and 13. 
• Web Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
A lot of the fun of geology has to do with figuring out the hows and whys of 
interesting and beautiful natural phenomena . Go online and explore how the 
wondrous blue color of the Hope Diamond is related to its atomic structure and 
composit ion by doing the Geology in Pract ice exercises. The Rock Cycle 
Review Online Review Exercise provides an excellent tour through the rock 
cycle and how it works in the context of plate tectonics. Other useful study aids 
on the Web site: 
• Flashcards to help you learn new terms 
• An online Chemistry Review containing an interactive periodic table of the 
elements 
• Addit ional Chapter Review quest ions 
Obviously you don ' t have t ime to do all these things for every chapter. The idea is to try out 
some of the tools and then decide which will be most helpful given your personal learning style. 
"Crys ta l " c o m e s f rom the G r e e k word krustallos, wh ich m e a n s ice. I s i c e — w a t e r 
ice—a minera l? H in t : A s k yourse l f if ice has the three p roper t i e s of a minera l . (1) Is ice 
naturally occur r ing? (2) D o e s it have a sol id c rys ta l l ine s t ruc ture? (3) D o e s it have a def-
inite chemical c o m p o s i t i o n ? (See p a g e 45 in the t ex tbook . ) 
Exam Prep 
Materials in this sect ion are mos t useful du r ing your p repara t ion for m i d t e r m and final 
examinations. The Chapter S u m m a r y and the Pract ice Exercises and Rev iew Quest ions 
should simplify your chapter review. Read the Chapter S u m m a r y to begin your session. I t 
provides a helpful overview that should refresh your memory . 
to all the Chapter Preview quest ions . The following checklist contains both general review 
tips and specific suggest ions for this chapter. 
Check Your Notes: Have you. . . 
• added a compar ison chart to help you sort out the key differences be tween the three 
rock types? (See the example . ) 
• added simplified sketches of key text figures? Trying to simplify a figure is often the 
best way of s tudying it, since you get involved in the important details . Example : 
Draw a simplified version of Figure 3.22 that will help you r e m e m b e r the difference 
in texture (crystal size) be tween intrusive and extrusive igneous rocks . 
Differences Between the Three Rock Types 
Igneous Sedimentary Metamorphic 
Source of materials Mel t ing of rocks in 
crust and mant le 
Weather ing and ero- High tempera tures 
sion of rocks exposed and pressures in 
at the surface deep crust and upper 
mant le , breaks from 
faulting or impact 
Rock-forming process Crystall ization 
(solidification of 
melt) 
Sedimentat ion, burial, Shear ing and recrys-
and lithification tall izing in the solid 
(compact ion and state 
cementa t ion) 
Refer to Figure 3.22 for the three different types of rock. 
Intensive Study Session 
Study Tip: Intensive study session 
T h e process of learning geology is similar to the procedure for bui lding a house . 
Before each lecture, construct a frame of quest ions . Dur ing lecture, attach details and 
ideas to the frame. After lecture, master the ideas dur ing an intensive study session. By 
learning about plate tectonics you have laid a good foundation, but geology is a 
skyscraper with 23 floors (one for each chapter) . Each floor (chapter) supports the one 
above it. If you don ' t complete ly master this chapter, the next one will be more difficult. 
Schedule about an hour after each lecture for intensive study. Devote this t ime to 
master ing key concepts . Mastery is not gained by jus t reading the text. Mastery occurs 
as the result of asking yourself quest ions and answer ing them. T h e Pract ice Exerc ises 
and Rev iew Quest ions are designed to help you reach mastery quickly. T h e more of 
these exercises and quest ions you can work into your study schedule early in the course , 
the easier subsequent chapters will be . 
40 PART II C H A P T E R 3 
Next , work on the Pract ice Exerc ises and Rev iew Ques t ions . To de te rmine how well 
you have mastered this chapter, comple te the exercises and ques t ions jus t as you would a 
mid te rm. After you answer the ques t ions , score them. Finally, review each ques t ion you 
missed . Identify and correct the misconcept ion(s ) that resul ted in your answer ing the ques -
tion incorrectly. 
Chapter Summary 
What are minerals? 
• Minera ls are naturally occurr ing inorganic solids with a specific crystal s truc-
ture and chemical composi t ion . 
How do atoms combine to form the crystal structure of minerals? 
• Minera ls form when a toms or ions chemical ly bond in an orderly, three-
dimensional geometr ic a r ray—a crystal structure. The character of the chemi -
cal bond can be ionic, covalent, or metal l ic . Ionic bonds are the dominan t type 
of chemical bonds in mineral structures. 
What is the atomic structure of minerals? 
• The a tomic structure is de termined by how the a toms or ions pack together to 
form a crystal l ine solid. The packing of a toms depends on their size and the 
characterist ics of chemical bonds be tween the a toms. 
Conceptual flowchart illustrating the factors 
that influence the physical properties of minerals 
Composition 
Temperature 
Pressure 
Crystal structure — 
the way atoms are packed together 
+ 
Type of chemical b o n d s -
ionic vs. covalent bonds 
Physical 
properties of 
minerals: 
Crystal shape 
Hardness 
Cleavage 
Color 
Electrical 
Optical 
What are the major rock-forming minerals and what 
are their physical properties? 
• The strength of the chemical bonds and the crystal l ine structure 
determines many of the physical proper t ies of minerals , such as 
hardness and cleavage. 
• Silicate minerals are the most abundant class of minera ls in the 
Ear th ' s crust and mant le . 
Isolated and chain silicates—olivine, pyroxene, and hornblende 
Sheet s i l ica tes—micas and clay minerals 
F ramework si l icates—feldspar and quartz 
• Other common mineral classes include carbonates, oxides, sul-
fates, sulfides, hal ides , and native metals . 
Why study minerals? 
• The composi t ion of rocks can be deduced from the composi tion 
of its minerals . 
• The environment in which the rock formed can be inferred 
because most minerals are stable under only certain condi t ions 
of temperature and pressure. 
Earth Materials: Minerals and Rocks 41 
• For fun and profit. Gems tones are t reasured for their beauty, color, and rarity. 
Many minerals are used in industrial processes and manufactur ing. 
What determines the properties of rocks? 
• The propert ies and names of rocks are determined by mineral content (the 
kinds and propor t ions of minerals that m a k e up rocks) and texture (the size, 
shapes, and spatial a r rangement of a rock ' s crystals or grains) . 
What are the three types of rocks, and how 
are they formed? 
• There are three major rock types . Igneous rocks solidify from mol ten l iquid 
(magma) . Crys ta l s ize wi th in i gneous rocks i s largely de t e rmined by the 
cool ing rate of the m a g m a body. Sed imen ta ry rocks are m a d e of s ed imen t s 
fo rmed f rom the w e a t h e r i n g a n d e r o s i o n o f any p r e e x i s t i n g r o c k . 
Depos i t ion , bur ia l , and l i thif ication ( compac t ion and cemen ta t i on ) t rans-
form loose s ed imen t s into sed imen ta ry rocks . M e t a m o r p h i c rocks are p ro -
duced by a l tera t ion in the solid state of any preex is t ing rock by h igh p res -
sures and t empe ra tu r e s , wh ich resul t in a c h a n g e in tex ture , minera l 
compos i t ion , o r chemica l compos i t i on . 
What is the association of different rock types with plate 
tectonics, the climate system, and the rock cycle? 
• The rock cycle is the result of interactions be tween plate tectonic and cl imate 
systems. 
The s chema t i c of the rock cyc le p resen ted in F igure 3.26 shows h o w 
the three major rock types are strongly associated with plate tectonic and cli-
matic sett ings. You may want to check out the onl ine review exercise on the 
rock cycle. 
What is an ore mineral? 
• Mineral deposi ts are considered ore deposi ts when they are rich and valuable 
enough to be mined economical ly . 
• Hydrothermal , metamorphic , chemical , and mechanical weather ing and sedi-
mentary processes can enrich metal-bear ing minerals to form economica l 
deposits . 
How do ore deposits of metal-bearing minerals form? 
• Many metal ore deposi ts are formed by magmat ic and hydrothermal processes, 
which are closely linked to both modern and ancient plate boundaries . 
Knowledge of how mineral deposits form and the association of mineral deposits 
and plate boundaries has greatly facilitated the discovery of new deposits. 
Earth Materials: Minerals and Rocks 43 
Silicate structure B 
Basic crystal structure 
E x a m p l e mineral 
Cleavage (Fill in the box with one of the 
cleavage symbols given in the key.) 
Silicate structure C 
Basic crystal s tructure 
E x a m p l e mineral 
Cleavage (Fill in the box with one of the 
cleavage symbols given in the key.) 
Exercise 2: Major mineral classes 
Fill in the blank with the n a m e of the mineral class to which each mineral be longs . The com-
mon classes of minerals include silicates, carbonates, sulfates, sulfides, oxides, native elements, 
and halides. Hint: Refer to Figure 3.9 and page 53 in the textbook. 
1. hornblende silicate 13. graphite 
Hint: an amphibole 
2. spinel 14. py r i t e . 
3. clay minerals 
4. calcite 
5. gypsum 
6. quartz_ 
15. muscovi te 
Hint: a mica 
16. anhydri te 
17. enstati te 
Hint: a pyroxene 
18. pyrite 
7. d iamond 19. sapphi re . 
8. dolomite 
9. plagioclase 
Hint: a feldspar 
10. ruby 
11. halite 
12. hemati te 
20. or thoclase . 
Hint: typically a tan- to-pink feldspar 
2 1 . silver . 
22 . albite 
Hint: typically a whi te feldspar 
2 3 . olivine . 
24. biotite . 
Hint: a black mica 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Crystal structures of some common silicate minerals 
Three crystal structures of silicate minerals are il lustrated here . T h e il lustration provides a 
b i rd ' s -eye view of a plane of a toms within the crystal structure of the mineral . The tr iangles, 
represent ing silica tetrahedra, are equivalent to the blue pyramids in Figure 3.9. 
• Wri te the name for each major silicate structure (single chain, double chain, 
sheet, framework, or isolated tetrahedra) . 
• Give an example of a mineral with that crystal structure. 
• Using the symbols given in the Cleavage Symbol Key below, character ize the 
cleavage propert ies for minerals with this crystal structure. 
Hint: Refer to Figure 3.9 and pages 6 0 - 6 6 . 
Geology Puns 
W h y did the geologist skip the minera logy luncheon? 
She d idn ' t have any apatite. 
The geology teacher asks a student if he can name the felsic mineral wi th crystal faces, 
conchoidal fracture, and a hardness of 7 on the M o h s ' scale. 
"Of quartz I can," says the student. 
T h e geologis t is at the eye doctor, being fitted for a new pair of glasses . " D o you ever 
see doub le?" asks the doctor. 
"Only when I look through calcite samples in lab," says the geologist . 
Exercise 3: Identifying minerals by their physical properties 
Give the name for each of the mineral samples descr ibed. 
Hint: Refer to figures and text in Chapter 3, Appendix 3 and to various links to minerals 
and gems provided on the Web site http:/ /www.whfreeman.com/understandingearth5e. 
Mineral Sample A 
This mineral is colorless and has a silvery shine. It separates into thin sheets or flakes 
that can bend without breaking. It is within a rock that contains large crystals of quar tz 
and feldspar. Hint: This mineral is named after M o s c o w where i t was c o m m o n l y used 
as a substitute for window glass. 
Mineral name: 
Mineral Sample B 
This mineral sample is pale yellow and occurs as a vein within a rock fracture. Many small 
cubic crystals of this mineral were exposed in the vein when the rock broke apart along the 
fracture. The powdered form (streak) of the mineral is black and has a sulfurlike smell . It 
is a c o m m o n metal sulfide ore mineral . 
Hint: A c o m m o n n a m e for this mineral is "fool 's gold." 
Mineral name: 
Mineral Sample C 
This mineral is on display at a mineral exhibit ion both as a mineral spec imen and cut 
and polished in pieces of jewelry. It consists of beautiful concentr ic bands of various 
shades of green. A knife blade can easily powder its surface but my fingernail cannot 
scratch it. Acid reacts with the mineral , especial ly if powdered . The spec imen was 
labeled as coming from a copper mine in Bisbee, Arizona. 
Hint: The mineral is a copper carbonate . 
Mineral name: 
Mineral Sample D 
This tan-to-pink sample occurs as many 5- to 7-cent imeter crystals surrounded by 
flakes of mica and grains of whi te- to-c lear quar tz . The tan- to-p ink crysta ls are pr i s -
ma t i c—rec tangu la r or box shaped. It has a hardness be tween that of a knife b lade and 
that of a steel file. 
Hint : I t i s one of the m o s t c o m m o n mine ra l s in the E a r t h ' s con t i nen t a l crus t . A 
s e m i p r e c i o u s variety, cal led moons tone , is used in jewelry . Refer to Figure 3 .21 . 
Mineral name : 
Earth Materials: Minerals and Rocks 45 
Mineral Sample E 
Exhibit ing excellent c leavage in three directions, this mineral breaks into beautiful 
rhombohedra l -shaped pieces . Samples vary in color from clear to whi te to tan. A finger-
nail does not scratch the surface, but a knife blade easily powders the surface. Weak 
acid readily reacts with the surface of the mineral . 
Hint: Mar ine organisms typically p roduce this mineral from seawater to generate their 
skele tons—seashel ls . Refer to Figure 3.16. 
Mineral name: 
Mineral SampleF 
This sample was found as a series of thin layers with other layers of mud and silt. My 
fingernail can easily scratch its surface and form a whi te powder. Water dissolves the 
powder, but the sample does not react with acid. Samples c o m m o n l y exhibit a splintery 
aspect but do not separate into individual f ibers , such as asbestos does . The sample eas-
ily breaks (cleaves) a long one plane but does not form the thin sheets typical of mica. 
Hint: This mineral is a major const i tuent of plaster of Paris and wal lboard used in 
buildings and houses . Refer to Table 3.2. 
Mineral name: 
Exercise 4: Rock cycle review 
Information and figures in Chapters 2 and 4 will be helpful references for this exercise. 
Also refer to Figure 3.26. 
A. What are the three plate tectonic settings for the generat ion of m a g m a ? 
hotspots, like Hawaii 
B. Given the two types of igneous rocks , intrusive and extrusive, fi l l in the table with their 
characteristic cool ing rates (fast vs. slow) and textures (fine grained vs. coarse grained). 
Types of igneous rocks Cooling rates Textures 
Extrusive 
Intrusive 
C. Rock and mineral particles are t ransported and laid down as sediments by what natural 
agents of t ransport? 
Hint: Three different agents of t ransport are shown in Figure 3.24. 
D. Wha t are the two ways loose sediments are converted into solid sedimentary rock? 
E. W h a t are the two main types of sediments , and what are they m a d e of? 
Type of sediment What is it made of? 
Hint: Refer to page 65 in the textbook. 
F. W h a t are the four major condi t ions that result in metamorphic rocks? 
Hint: Refer to Figure 3.25 
G. Are metamorphic rocks formed by mel t ing? A n s w e r yes or no. 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. The bonds be tween Na and CI in halite are strongly ionic. In ion form, CI has seven 
electrons in its outer shell and Na has one. After these two e lements bond, CI has 
electrons in its outer shell and Na has electrons in its outer shell. 
A. six, two C. one , seven 
B. four, four D. eight, e ight 
Hint: Refer to Figure 3.4. 
2. and are examples of minerals with identical chemical compos i t ions but 
different crystal structures. 
A. Calci te , dolomite 
B. Hemat i te , magnet i te 
C. Pyri te , gypsum 
D. Graphi te , d iamond 
3. The term geologists use for a naturally occurr ing aggregate of minera ls is 
A. e lement . C. compound . 
B. rock. D. crystal . 
4. W h e n a substance is made of a toms that are arranged in a fixed, orderly, and repeat ing 
pattern, it is said to be 
A. amorphous . C. crystal l ine. 
B. glassy. D. liquid. 
5. Which of the following statements is N O T true of minera ls? 
A. They are crystal l ine. 
B. They possess a definite chemical composi t ion . 
C. They are naturally occurring. 
D. They are organic . 
48 PART II C H A P T E R 3 
16. C h e m i c a l bond ing a long c leavage p lanes wi th in the c rys ta l s t ruc ture of a mine ra l 
typica l ly 
Hint: Refer to the section in the textbook titled Cleavage. 
17. Iron and magnes ium ions are similar in size and both have a +2 charge . Therefore we 
would expect iron and magnes ium to 
A. bond easily. 
B. share electrons. 
C. form minerals with different crystal structures. 
D. substi tute for each other within the crystal s tructure of minera ls . 
Hint: Refer to Figures 3.3 and 3.4 and the section in the textbook titled How Do 
Minerals Form? 
18. The chemical bonds be tween carbon a toms within d iamond are predominant ly 
A. covalent. C. metall ic . 
B. ionic. D. nuclear. 
19. W h i c h of the following rocks forms from molten material cool ing and solidifying with-
in the Ear th ' s crust? 
A. volcanic C. sedimentary 
B. plutonic D. me tamorph ic 
20. Mol ten rock within the Ear th ' s crust is called 
A. silica. C. magma . 
B. lava. D. mica. 
2 1 . Coarse-gra ined igneous rocks, such as granite, are exposed today at the Ear th ' s surface 
due to 
A. uplift and erosion. 
B. quickly cooled lavas erupt ing from ancient volcanoes . 
C. silicate minerals precipitated from rainwater. 
D. all of the above. 
22. Lithification is the process that converts sediments into solid rock by 
A. cool ing and crystall ization. 
B. pressure cooking. 
C. subduct ion. 
D. cementat ion and compact ion . 
2 3 . Bedding (layering) is a major identifying characterist ic of 
A. sedimentary rocks . C. intrusive rocks . 
B. metamorphic rocks . D. none of the above. 
24. Contact me tamorph i sm 
A. occurs in areas of very high temperature and pressure, like subduct ion zones . 
B. extends over very large areas. 
C. is characterist ic of continental collision zones . 
D. occurs in areas where m a g m a intrudes and me tamorphoses ne ighbor ing rock. 
Hint: Refer to Figure 3.25. 
25 . In the rock cycle, weather ing 
A. creates sediments . C. creates mounta ins . 
B. results in burial and lithification. D. can cause me tamorph i sm. 
26 . In the rock cycle, mounta ins typically form as a result of 
A. weather ing and erosion. C. sedimenta t ion pil ing up rock. 
B. metamorph ism. D. subduct ion and cont inents coll iding. 
Hint: Refer to Figure 3.26. 
A. is more covalent. 
B. is more ionic. 
C. is more magnet ic . 
D. involves electron sharing be tween a toms. 
Eai Earth Materials: Minerals and Rocks 47 
6. Which of the fol lowing objects is N O T a mineral? 
A. native copper C. d iamond 
B. glass D. water ice 
7. The most c o m m o n mineral group on Earth is 
A. carbonates . C. oxides . 
B. silicates. D. halides. 
H i n t : Refer to F igure 1.8 and page 8. 
8. The structure of feldspars, such as or thoclase and plagioclase, consists of 
A. double chains of silica tetrahedra. 
B. a three-dimensional f ramework of silica tetrahedra. 
C. single chains of silica tetrahedra. 
D. isolated silica tetrahedra. 
9. Micas are known for their tendency to split into thin sheets; their silicate c rys t a l : 
ture is 
A. isolated silica tetrahedra. 
B. chains of silica te trahedra. 
C. sheets of silica tetrahedra. 
D. a f ramework ar rangement of silica tetrahedra. 
10. Which of the fol lowing does N O T belong to the carbonate class of minerals? 
A. calcite C. dolomite 
B. anhydri te D. aragonite 
11. Which of the following minerals has a sheet silicate s tructure? 
A. clay minerals C. amphibole 
B. feldspar D. graphite 
12. Amphiboles and pyroxenes are mineral groups that belong to the class of mil 
called 
A. chain silicates. 
B. f ramework sil icates. 
C. sulfide minerals . 
D. sheet silicates. 
13. Which of the fol lowing s ta tements is N O T true of quartz and calcite? 
A. Calcite has excellent c leavage; quartz has poor to no cleavage. 
B. Quar tz is a carbonate mineral . 
C. Both are often color less . 
D. Quartz has a hardness of about 7 and calcite a hardness of about 3. 
14. The characterist ic of certain minerals to break along planes of weakness is called 
A. crystal symmetry . C. hardness . 
B. cleavage. D. luster. 
15. Graphite and d iamond are two very different minerals . W h y are the physical prop-
erties of graphite and d iamond so different even though they are both made from 
pure carbon? 
A. The chemical bonds be tween the carbon a toms and their crystal structures are 
significantly different. 
B. Graphi te has strikingly different physical propert ies from d iamond because 
of impuri t ies within its crystal structure, whereas d iamond is pure carbon. 
C. Actually, graphi te and d iamond are not minerals because they are m a d e from 
carbon and all mat ter made from carbon is organic. Their physical propert ies 
are different because they were produced by very different living organisms. 
D. N o n e of the above.H i n t : Refer to F igure Story 3.11 (a and b). 
Earth Materials: Minerals and Rocks 49 
Study Tip: Construct a Simplified Rock Cycle 
Figure 3.26 packs much information into one page and provides an overview of how 
rock types are l inked to Ear th ' s plate tectonic and c l imate systems. As a review for an 
exam, construct your own rock cycle flowchart. Keep it relatively s imple and focus 
on presenting the following information: 
• Major rock types 
• One or two important diagnost ic characterist ics of each rock type 
• Process(es) that t ransform a rock into another rock type 
Use sketches, words , phrases , or bulleted lists to descr ibe each componen t (each major 
rock type) and connect ing pa thways (processes that t ransform rocks into another type) . 
If you are a visual learner, concentra te on drawing s imple il lustrations that 
characterize how each rock type forms and how it is l inked to other rock types . If you 
learn better from reading or l istening, then use arrows and descr ibe the major e lements 
of the rock cycle in words and read it out loud. 
CHAPTER 4 
Igneous Rocks: 
Solids from Melts 
5 0 
Igneous Rocks: Solids from Melts 51 
Before Lecture 
Before you go to lecture, spend some t ime previewing Chapter 4. We have m a d e i t easier by 
identifying the five key quest ions on igneous rocks for you (see Chapter Preview) . These 
questions const i tute the f ramework for unders tanding this chapter. Working with the Chapter 
Preview quest ions before lecture and commit t ing them to m e m o r y should help you under-
stand the lecture better and take excellent notes. Need a refresher on previewing? See Chapter 
3 of Part I, How to Be Successful in Geology, in this Study Guide . 
Chapter Preview 
• How are igneous rocks classified? 
Brief answer: Compos i t ion and texture (cooling history). Preview Figures 4 . 1 , 4 . 3 , 
and 4.4 and Tables 4.1 and 4.2. Hint: Table 4.2 summar izes the crucial information, 
but you will need to look at the figures in order to unders tand it. 
• How and where do m a g m a s form? 
Hint: Table 4.3 and Figure 4.11 in the textbook provide an overview. 
• How does magmat ic differentiation account for the great variety of igneous rocks? 
Hint: Figure 4.5 tells the classic differentiation story. Figure 4.6 adds important details. 
• What are the forms of intrusive and extrusive igneous rocks? 
Hint: Figures 4.7 and 4 .10 show the basic intrusive and extrusive igneous rock bodies . 
• How do igneous rocks relate to plate tectonics? 
Brief answer: M a g m a s tend to form at divergent and convergent plate boundar ies and 
hot spots. Hint: Refer to Figures 4 . 1 1 , 4 .13 , and 4 .14 and the Activity, Rock 
Composi t ion, and Types of M a g m a s section of Chapter 4 for more details. 
Preview of magma types in relation to plate tectonic settings 
Plate tectonic setting (examples) Magma type (example rock type) 
Spreading centers 
• oceanic r idge (Mid-Atlant ic Ridge) 
• continental rift (East African Rift) 
Subduction zones 
• oceanic island arc (Japan) 
• continental volcanic arc (Cascade Range , 
Mt. St. Helens , M o u n t Rainier, and Andes 
in South Amer ica ) 
Note: Not much volcanism occurs in 
association with coll ision plate boundar ies . 
Intraplate mant le p l u m e s ("hot spots") 
• oceanic hot spots (Hawai i ) 
• continental hot spots (Yellowstone) 
• mafic (basalt) 
• mafic to felsic (s i l ic ic)—more variable 
because some continental crust may melt . 
• mafic to in termediate 
• mafic to felsic (s i l ic ic)—more variable 
because continental crust may melt . 
• mafic (basalt) 
• mafic to felsic (s i l ic ic)—more variable 
because continental crust is melted. 
Vital Information from Other Chapters 
Review Figures 3.22 and 3 .23. 
Web Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Review the Rock Cycle Review in Chapter 3 on the Web site. Pay part icular at tention to infor-
mat ion on melting, magmas, cooling, and igneous rocks. 
During Lecture 
A lot of important visual material will be covered in this lecture. Be sure you preview the 
chapter before lecture. Because the material is somewhat technical , you will want to take 
notes in as organized a manner as possible. Fol lowing are some ideas you m a y find helpful. 
• Big picture for Chapter 4. To avoid getting lost in details, keep the big picture 
in mind throughout the lecture. 
Chapter 5 explains how plate tectonics drives the formation of magma and 
how igneous rocks of varying composition and texture are produced at partic-
ular plate locations. For example, fine, textured volcanic rock of basaltic 
composition is produced at a diverging ocean plate (see Figure 4.13). 
• Key figures for lecture. This chapter introduces many new words and con-
cepts to learn. I t may be helpful to bookmark one or two of the mos t impor-
tant textbook figures you previewed before coming to lecture. F igure 4 .3 will 
help you with igneous rock classification. Figures 3.26, 4 . 1 1 , 4 .13 , and 4 .14 
summar ize where and how m a g m a s are formed. 
• You will also be developing a new skill: identifying igneous rocks . Often lec-
turers use slides or rock samples to help you learn this skill. The fol lowing tip 
and chart tool will help you master this skill efficiently. 
Note-Taking Tip: How to take notes on rock samples 
During lecture the instructor may show slides of igneous rock formations and m a y pass 
around specimens of igneous rocks . The spec imens will be easier to see if you sit c lose 
to the front of the room. For the instructor, each sample tells a story. You can b e c o m e 
proficient at reading rock stories, too. It jus t takes pract ice and a little organizat ion. For 
igneous rocks , a chart like the following example will he lp you organize what you see 
and hear. T h e chart focuses on the two things you need to pay the most at tention to: 
texture (whether or not you can see crystals) and composition (the likely mineral content 
of this rock) . If the instructor tells an interesting story about the rock, make a note or 
two; stories help us r emember details we might o therwise forget. 
W h a t to do . Before the lecture on igneous rocks , make a chart like the one that 
follows on a full sheet of notebook paper. Leave plenty of room for notes about each 
sample . Try to put something in every co lumn for every rock sample . If you miss a 
co lumn or were unable to see some of the minerals in the rock, be sure to talk to the 
instructor right after lecture (while your m e m o r y is fresh and the rock sample is handy) 
and f i l l in wha t you need to comple te the chart. Hint: Th is idea is also going to be 
useful in subsequent chapters on sedimentary and metamorphic rocks . 
Igneous Rocks: Solids from Melts 53 
Example: Rock sample-note taking chart 
(Set up on one full page of your notebook.) 
Texture clues 
(coarse, 
Rock name fine, etc.) 
Composition 
clues (mineral 
clues, color, 
dark/light, etc.) 
Story about the 
rock to help you 
remember it Other notes 
(Example) 
Granite 
Coarse I could m a k e out crystals 
of black hornblende , 
whi te and pink feldspars, 
" C a m e from [you n a m e 
it] Mounta in near our 
campus . I s l ipped and 
fell jus t before I found 
this sample ." Stories 
will help you r e m e m b e r 
information. 
Crystals were clearly 
visible in the slide. 
Crystals were most ly 
feldspar and muscovi te 
mica! W h a t I thought was 
hornb lende turned out to 
be biotite. I tried to scratch 
the rock with a penny; no 
luck, mus t be kind of hard 
(above 3 on the M o h s ' 
scale) . Minera l s in grani te 
average greater than 5 on 
the M o h s ' scale. Too bad 
I d idn ' t br ing my bowie 
knife to class . 
and thin, shiny sheetsof mica in a light gray 
matr ix (quartz). 
Sample 1 
Sample 2 and so on 
After Lecture 
Review Notes 
Chapter 4 is a bit technical, so it will be particularly important to rework and improve your 
notes after lecture. 
Check Your Notes: Have you. . . 
• used the five preview quest ions as section headings for your notes? You should have 
sections dealing with (1) classification, (2) m a g m a formation, (3) m a g m a differentiation, 
(4) igneous s t ructures , and (5) plate tectonics and igneous rock formation. 
54 PART II C H A P T E R 4 
• added exercise material from this guide to your notes? A great place to begin is to 
comple te Exercise 1 (see Pract ice Exercises) . Exerc ise 1 will help you unders tand 
what is perhaps the single most fundamental idea about igneous rock, namely 
rock texture. If you do the exercise sketches on no tebook paper, you can clip them 
somewhere near the beginning of your notes on igneous rocks for future review. 
• added visual material to your notes? Key figures to consider adding are Figure 4.4, 
classification model of igneous rocks ; Figure 4 .5 , fractional crystal l ization which 
explains the composi t ion of a basalt ic intrusion; Figure 4 .7 , basic extrusive and 
intrusive igneous structures; and Figure 4 . 1 1 , plate tectonics and m a g m a formation. 
Remember , the idea is to draw simplified versions that emphas ize the features 
d iscussed in lecture. 
• included a brief summary of this chapter? Wri t ing a brief summary of the essence 
of a chapter is a good way to help focus on what is important and avoid get t ing 
bogged down in less essential details. 
Intensive Study Session 
You learn geology much as you would build a house . Before each lecture, construct a frame 
of quest ions . Dur ing lecture, attach details and ideas to the frame. After lecture mas ter the 
ideas during an intensive study session. N o w you have constructed the first few stories. But 
geology is a skyscraper with 23 floors (one for each chapter) . Each chapter supports the one 
above it. If you don ' t complete ly master this chapter, the next will be more difficult. 
• Test your unders tanding of rock texture and other important concepts 
identified in the Chapter Preview. There are some great features built into 
this chapter that you can use to learn. One good example is Figure 4 .2 . Read 
the section Texture at the beginning of the chapter. You will learn how James 
Hutton deduced the nature of igneous rock by assessing three lines of ev idence 
(clues 1-3). Then look at Figure 4.2. You can have an exper ience of d iscov-
ery not unlike Hut ton ' s . Study Figures 4 . 1 , 4 .2 , and 4.3 until you think you 
unders tand texture. Then do Exercise 1 and really master interpret ing rock tex-
tures. M o v e on through the chapter, paying part icular attention to Figures 4 . 3 , 
4 . 4 , 4 . 5 , 4 . 7 , and 4 . 1 1 . 
• Pract ice Exercises and Review Quest ions Next use the Study Guide 
Pract ice Exercises and Review Quest ions in the Study Guide . Be sure to do 
Exercise 1. It involves the key information you need to learn in this chapter. 
• W e b Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Comple te the online exercises Bowen's Reaction Series Review and Igneous 
Rock Review. F lashcards will help you learn new terms. Try your hand at being 
a field geologist by doing the exercises in Geo logy in Pract ice , an excellent 
review of basic information on igneous rocks . 
Exam Prep 
Materia ls in this section are mos t useful during your preparat ion for exams . The following 
Chapter S u m m a r y and the Pract ice Exercises and Rev iew Ques t ions should simplify your 
chapter review. Read the Chapter S u m m a r y first. It provides a helpful overview that should 
refresh your memory. 
Next, work on the Pract ice Exercises and Review Quest ions . Comple te the exercises and 
questions just as you would an exam, to see how well you have mastered this chapter. After 
you answer the quest ions, score them. Finally, and most important, review each quest ion you 
missed. Identify and correct the misconcept ion(s) that resulted in your incorrect answer. 
Chapter Summary 
How are igneous rocks classified? 
• Igneous rocks can be divided into two broad textural classes: (1) coarsely crys-
talline rocks , which are intrusive (plutonic) and therefore cooled slowly, and 
(2) finely crystal l ine rocks , which are extrusive (volcanic) and cooled rapidly. 
Within each of these broad textual classes, the rocks are subdivided according 
to their composi t ion. General composi t ional classes of igneous rocks are felsic, 
intermediate, mafic, and ultramafic, with decreasing silica and increasing iron 
and magnes ium content . 
How and where do magmas form? 
• The lower crust and the upper mant le are typical places where physical condi-
tions induce rock to melt . High temperatures , a reduct ion in pressure , and the 
presence of water all cause mel t ing. Compos i t ion is also a factor in the melt-
ing temperature of rocks . 
How to melt a rock—the generation of magma 
• Increase the tempera ture . 
Not all minera ls melt at the same temperature (refer to Figure 4 .5) . The 
mineral composi t ion of the rock affects the mel t ing temperature . Felsic rocks 
Igneous Rocks: Solids from Melts 55 
with higher silica content mel t at lower temperatures than do mafic rocks , 
which contain less silica and more iron and magnes ium. 
• Lower the confining pressure . 
A reduct ion in pressure can induce a hot rock to melt . A reduct ion in con-
fining pressure on the hot upper mant le is thought to genera te the basal t ic m a g -
mas that intrude into the oceanic r idge system to form ocean crust (refer to 
Figure 4.13) . 
• Add water. 
The presence of water in a rock can lower its mel t ing tempera ture by up 
to a few hundred degrees. Water released from rocks subducting into the mant le 
a long convergent plate boundar ies may be an important factor in m a g m a gen-
eration, especially at the convergent plate boundar ies (refer to F igure 4 .14) . 
How does magmatic differentiation account for 
the great variety of igneous rocks? 
• T h e r e is an a m a z i n g var ie ty of i g n e o u s rocks on Ear th . T w o p r o c e s s e s h e l p 
to exp la in h o w the c o m p o s i t i o n o f i g n e o u s r o c k s can be so va r i ab le . T h e y 
are par t ia l me l t i ng and f ract ional c rys ta l l i za t ion (refer to F igu re s 4 .5 
and 4 .6 ) . 
• The B o w e n ' s react ion series in Figure 4.5 is a f lowchart descr ibing how the 
very general bulk composi t ion of a m a g m a can change as the m a g m a solidi-
fies or as a rock mel ts . 
What are the forms of intrusive and extrusive igneous rocks? 
• N a m e s are given to igneous rock bodies based on their size and shape. F igure 
4.7 summar izes the c o m m o n igneous rock bodies , such as batholi th, pluton, 
dike, and sill. 
How do igneous rocks relate to plate tectonics? 
• Mid-ocean ridges and subduct ion zones are the major sites of magmat i c activ-
ity (refer to Figures 4 . 1 1 , 4 .13 , and 4.14) . 
56 PART II C H A P T E R 4 
Igneous Rocks: Solids from Melts 57 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Igneous rock textures 
In each of the four boxes , sketch the igneous rock texture that is consistent with the origin of 
the rock as descr ibed above each box . Fill in the blank with the appropriate texture term from 
the list. Table 4 .2 , p lus Figures 3.23 and 4 .3 , will be helpful. 
Texture t erms 
Fine grained (aphanit ic) 
Intermediate grain s izes—visual grains but not very coarse grained 
Coarse grained (phaneri t ic) 
Mixture of coarse and fine grains (porphyri t ic) 
A. Draw the textureof an igneous rock from a 
pluton solidified at depth within the crust. 
B. Draw the texture of an igneous rock from a 
shallow magma body, like a dike or sill. 
phaneritic 
N a m e of texture 
C. Draw the texture of a lava erupted from a 
magma chamber after some minerals had 
begun to crystallize. 
N a m e of texture 
D. Draw the texture of a lava flow that erupted 
before the m a g m a chamber underwen t 
any crystall ization. 
N a m e of texture N a m e of texture 
Figure 4 .4 . Classification model of igneous rocks. 
The vertical axis measures the mineral composition of 
a given rock as a percentage of its volume. The hori-
zontal axis is a scale of silica content by weight. Thus, 
if you know by chemical analysis that a coarsely tex-
tured rock sample is about 70 percent silica, you 
could determine that its composition is about 6 per-
cent amphibole, 3 percent biotite, 5 percent mus-
covite, 14 percent plagioclase feldspar, 22 percent 
quartz, and 50 percent orthoclase feldspar. Your rock 
would be a granite. Although rhyolite has the same 
mineral composition, its fine texture would eliminate it. 
58 PART I I C H A P T E R 4 
Exercise 2: Distribution of igneous rocks within the Earth 
Comple te the table with terms from the lists that follow the table. Refer to Table 4.2 and 
Figure 4.4 in your textbook. S o m e answers are provided. Note that the Ear th ' s core is not 
included in this table because it is thought to be composed most ly of iron and nickel , not sil-
icate minerals . 
Major layer Example General General 
in the Earth igneous rock compositional group chemical composition 
Cont inenta l crust Granite 
(For cont inental crust, there 
are two appropr ia te answers . ) 
Intermediate 
O c e a n crust 
Mant l e Less Si, Na, K 
More Fe, Mg, Ca 
Example igneous rocks General composit ional group 
granite/rhyolite ultramafic 
basalt/gabbro felsic 
andesite/diorite intermediate 
peridotite mafic 
granodiorite/dacit 
Igneous Rocks: Solids from Melts 59 
Exercise 3: Predicting the change in composition 
in crystallizing magma 
Sandstone 
Basalt 
Mostly sodium-rich 
plagioclase feldspar; 
no olivine 
Calcium-rich plagiocla 
feldspar and pyroxene 
no olivine 
Olivine 
Basalt 
Sandstone 
A basaltic m a g m a intruded be tween sandstone layers to form the sill. As the m a g m a cooled in 
place, fractions of the crystals that formed settled into layers—it underwent fractional crystal-
lization. Using Figures 4.4 and 4 .5 , and Table 4.2, predict how the silica and iron content of 
the Palisades sill changes . Indicate whether the silica and iron content increase, decrease, or 
stay the same in each layer of the sill. Explain the reason(s) for your answers . 
Predict how the silica and iron content of the mafic Pal isades sill changes as the m a g m a cools . 
Circle the correct answer. 
A. Olivine -> Pyroxene Calc ium-r ich plagioclase feldspar and pyroxene with no olivine 
1. Silica content: increased / decreased / stay the same 
2. Iron content: increased / decreased / stay the same 
Explanation: 
B. Calcium-rich plagioclase -> sodium-r ich plagioclase feldspar and no olivine 
1. Silica content: increased / decreased / stay the same 
2. Iron content: increased / decreased / stay the same 
Explanation: 
Exercise 4: Sequence of mineral crystallization in a solidifying magma 
Circle the answers that correct ly comple te the following statements . 
A. The a tomic (crystal) s tructure of the earliest formed silicate minerals in a m a g m a 
tend to be M O R E / L E S S complex than the crystall ine structures of minerals formed 
during later stages in the solidification of the magma . 
B. Dur ing the solidification of a m a g m a , the minerals with the highest silica content 
will crystal l ize F I R S T / LAST. 
C. In the last s tages of solidification of a m a g m a , the remaining silicate melt will con-
tain M O R E / L E S S silica than the original melt . 
Hint: You do not need to know the bulk composi t ion (mafic, in termediate , felsic) of the 
magma to answer these quest ions . Refer to Figures 4.4 and 4.5 and Table 4 .2 . 
Exercise 5: Partial melting and magma composition 
Circle the answers that correctly comple te the following s ta tements . 
Compared to the bulk composi t ion of the rock, the minerals with the lower mel t ing tempera-
ture are 
A. H I G H E R / L O W E R in the B o w e n ' s reaction series. 
B. D E P L E T E D / E N R I C H E D in M g , Fe , and Ca. 
C. D E P L E T E D / E N R I C H E D in Si, Na, K. 
Hint: Refer to Figure 4 .5 . 
Exercise 6: Predicting the composition of magma 
generated in subduction zones 
Circle the answer for each statement that correctly completes the following sentence: Compared 
to the basalt ic ocean crust, the m a g m a generated by partial mel t ing of the subduct ing slab of 
ocean crust will 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. Igneous rock names are based on 
A. texture and composi t ion . 
B. f ine grain and coarse grain. 
C. intrusive and extrusive. 
D. where the m a g m a chamber erupts . 
2. W h a t rock has the same mineralogy as granite but a fine-grained texture? 
A. andesi te C. obsidian 
B. basalt D. rhyoli te 
Hint: Refer to Table 4.2. 
3. Which of the following rocks contains the most sil ica? 
A. basal t C. f issure erupt ions 
B. rhyolit D. dacite 
A 
B. 
C. 
D 
have M O R E / L E S S silica, 
have M O R E / L E S S iron and magnes ium, 
have M O R E / L E S S sodium and potass ium, 
b e M O R E / L E S S mafic. 
Igneous Rocks: Solids from Melts 61 
4. Which of the following pairs of intrusive and extrusive rocks are made from the same 
minerals—i.e . , have the same chemical compos i t ion? 
5. In the field or in hand-s ized spec imens , intrusive and extrusive igneous rocks are dis-
t inguished by which character is t ic? 
A. composi t ion 
B. color 
C. porphyri t ic versus nonporphyri t ic texture 
D. grain size 
6. Which of the fol lowing iron-rich minerals is most c o m m o n in basal t? 
A. pyroxene C. muscovi te 
B. quartz D. Na-plagioclase 
7. Granite is m a d e up mainly of 
A. quartz, or thoclase (K-feldspar) , and Na-plagioclase . 
B. quartz, Ca-plagioclase , Na-plagioclase , and amphibole . 
C. quartz, pyroxene , and muscovi te . 
D. quartz, or thoclase (K-feldspar) , Ca-plagioclase , and olivine. 
Hint: Refer to Table 4.1 and Figure 4.4. 
8. An igneous rock m a d e of a mixture of both coarse- and fine-grained minerals is called 
porphyrit ic and is formed by 
A. rapid cool ing followed by a period of slow cool ing. 
B. slow cool ing fol lowed by a period of rapid cool ing. 
C. very slow cool ing of a water-rich ma gma . 
D. very rapid cool ing in the presence of water. 
9. Only iron and magnes ium-r ich minerals are found in which of the following lists of 
minerals? 
A. pyroxene, hornblende , K-feldspar, bioti te 
B. plagioclase, biotite, pyroxene , clay 
C. quartz, muscovi te , bioti te, p lagioclase 
D. biotite, pyroxene , olivine, hornblende 
10. Fol lowing B o w e n ' s react ion series, the later, lower- temperature fractions of liquid 
m a g m a b e c o m e progressively 
A. depleted in silica. 
B. enr iched in silica. 
C. enriched in magnes ium. 
D. depleted in potass ium. 
Hint: Refer to Figure 4 .5 . 
11. Which of the following minerals are the earliest h ighes t - temperature minerals to crys-
tallize in B o w e n ' s React ion Series? 
A. quartz and feldspar 
B. plagioclase and amphibo le 
C. plagioclase and olivine 
D. chert and mica 
12. The formation of granit ic batholi ths occurs 
A. within the ocean crust. 
B. within the continental crust . 
C. a long spreading centers in the ocean. 
D. underhot spots . 
A. gabbro and basalt 
B. diorite and basalt 
C. f issure erupt ions 
D. gabbro and rhyolite 
13. Consider ing the following minerals , which pairs would you predict wou ld N O T be 
found together in the same igneous rock? 
A. K-feldspar and bioti te 
B. Na-plagioclase and muscovi te 
C. quartz and Na-plagioclase 
D. quartz and olivine 
Hint: Refer to Figures 4.4 and 4 .5 . 
14. How would you dist inguish a lava flow from a sill exposed at the Ear th ' s surface? 
A. Sills tend to be coarser grained than lava flows because they cool slower. 
B. The chemical composi t ions of the lava flow and the sill (that is, the minera ls pres-
ent) would be very different. 
C. Sills tend to be finer grained because of s lower rates of crystal l izat ion. 
D. Lava flows are coarser grained because of very rapid rates of cool ing. 
15. T h e rock type of most bathol i ths found in the continental crust is 
A. gabbro . C. granite. 
B. obsidian. D. basalt . 
16. H o w does a rising m a g m a make space for itself as i t moves through the solid crust? 
A. by breaking off large b locks of rock that sink into the m a g m a chamber 
B. by wedging open the overlying rock 
C. by mel t ing surrounding rocks 
D. by all these processes 
17. T h e source for most mafic m a g m a s is thought to be 
A. partial mel t ing of felsic and intermediate rocks in the upper cont inental crust. 
B. partial mel t ing of ultramafic rocks within the upper mant le . 
C. mel t ing of preexist ing granites and sediments . 
D. the mol ten core of the Earth . 
18. If lava flows on the slopes of a volcano are derived from one large m a g m a chamber, 
which crystall izes slowly and feeds eruptions over a period of many thousands of years, 
how would you predict the gross composi t ion of the lava would change as the lava flows 
b e c o m e younger? 
A. Younger lava flows would b e c o m e progressively enr iched in iron and more mafic. 
B. Younger lava flows would b e c o m e progressively enr iched in silica and more felsic. 
C. Lava flows would be the same composi t ion since they all c ame from the same 
m a g m a chamber . 
D. Lava flows would alternate in composi t ion . 
Hint: Use B o w e n ' s react ion series in Figure 4.5 and review the tex tbook section 
Magmatic Differentiation. 
19. The product ion of basal t can be achieved by the partial mel t ing of 
A. gabbro . 
B. ultramafic rocks . 
C. a mixture of gabbro and oceanic sediments . 
D. rhyoli te . 
Hint: Refer to Figures 4.11 and 4 .13 . 
20. Andes i tes—inte rmedia te m a g m a s — a r e typically associated with 
A. divergent plate margins , like the mid-oceanic r idges . 
B. fractures in the crust that allow magmas from the upper mant le to rise to the surface. 
C. hot spots, like Hawai i . 
D. convergent plate margins , like the western edge of South A m e r i c a — t h e Andes . 
2 1 . An ophioli te suite contains the following combinat ion of rocks : 
A. granite, gneiss , sandstone, l imestone, and shale. 
B. deep sea sediments , pil low basal ts , gabbro, and peridot i tes . 
C. dikes, sills, and plutons of peridoti tes . 
D. plutonic rocks and surrounding sediments characterist ic of a m a g m a chamber . 
22. Which flowchart character izes the magmat ic processes that occurr at spreading centers? 
A. peridotite -> decompress ion melt ing -* basalt 
B. ophiolite -* f luid-induced mel t ing -* basalt 
C. deep ocean sediments -*• f luid-induced melt ing -> andesi tes 
D. basalt decompress ion mel t ing peridoti te 
23. Which of the following hypotheses for the origin of granite is N O T reasonable? 
A. mixing of m a g m a s with different composi t ions 
B. decompress ion mel t ing within a m a g m a p lume 
C. partial melt ing 
D. melting of sedimentary and metamorphic rocks 
24. Which set of condi t ions will result in basalt melt ing at the lowest tempera ture? 
A. dry basalt at low pressure 
B. dry basalt at high pressure 
C. wet basalt at low pressure 
D. wet basalt at high pressure 
Igneous Rocks: Solids from Melts 63 
CHAPTER 5 
Sedimentation: 
Rocks Formed by Surface Processes 
Sedimentation: Rocks Formed by Surface Processes 
• How does plate tectonics relate to sed imentary rock? 
Brief answer: Envi ronments of deposi t ion, composi t ion , and texture of sediments , as 
well as the shape and depth of sedimentary basins , are influenced by plate tectonics. 
Refer to Figure 5.4. 
• What is the re lat ionship between sed iments and environments on the 
Earth's surface? 
Hint: Refer to F igure 5.5 and Table 5.2. 
• What are the m a j o r types of sed iments a n d sed imentary rocks? 
Brief answer: siliciclastic (sandstone) versus chemica l (evaporites) and biochemical 
(limestone). Study Tables 5.3 and 5.4, and Figures 5.5, 5.12, and 5.16. 
Vital Information from Other Chapters 
Review Figure 3.24 and preview pages 3 7 2 - 3 8 1 in Chapter 16. 
During Lecture 
Note-Taking Tip: Some features to watch for in 
sedimentary rock samples and formations 
In this lecture you will be introduced to a variety of sedimentary rocks , formations, 
and sedimentary envi ronments . Since they will probably be new to you, i t is smart to 
prepare. Spend a few minutes of your preview t ime becoming familiar with the mos t 
important sedimentary rock features: 
• Bedding and other sedimentary structures: pages 1 1 1 - 1 1 3 
• Bedding sequences (strat igraphy): Figure 5.11 on page 114 
• Grain size: Figures 5.3 and 5.15 and Table 5.3 
• Mineral content and major groups of sandstones: Figure 5.16 on page 118 
• Chemical and b iochemica l sedimentary rocks: Figure 5.17 
• Fossils: Figure 5.18 
One goal for lecture should be to leave the r o o m with good answers to the preview quest ions . 
To avoid getting lost in the details, keep the big picture in mind: Chapter 5 tells the story of 
how sedimentary rocks are created by the processes of the rock cycle. It may be helpful to have 
Figure 5.1 with you so that you can refer to it dur ing lecture. 
Note-Taking Tip: Use abbreviations to speed up your note taking 
bed -+ bedding lith -+ lithification 
carb -» carbonate sed -» sediment or sedimentary 
clast -> clastic sed r -> sedimentary rock 
chem -+ chemica l carb sed -*• carbonate sediment 
biochem -+ b iochemica l sed base -*• sedimentary basin 
env -» envi ronment sed env -* sedimentary envi ronment 
After Lecture 
Review Notes 
Right after lecture, while the material is fresh in your mind, is the perfect t ime to review your 
notes. Review to be sure you unders tood all the key points and wrote them down in a form 
that will be readable later. 
Check Your Notes: Have you. . . 
• included the chapter overview? Figure 5.1 is the "big picture." Cons ider adding 
your own version, including the six sedimentary rock-forming steps. 
• developed a chart like the one in Exercise 1 to help you learn the sedimentary 
envi ronments? 
Intensive Study Session: Focus on chunking the 
information into a solid overview 
In earlier chapters we have used the metaphor of building a house for s tudying geology. 
Chunking is a menta l process that will help you construct a good frame. The idea is to group 
the important information. Later you hang details on this f ramework of basic information. 
If you have somet imes wondered how some of your professors can rattle off tons of com-
plicated material without even looking at their lecture notes , chunking (see box) provides an 
explanat ion. Over the years they have chunked (connected) more and more bits of informa-
tion about geology. Chapter 5 provides a great opportuni ty for you to develop your memory 
efficiency. Use the clues and aids in the box to group the details of sedimentary rocks into a 
format that is easy to remember . 
Memory and Learning Tip: Chunking 
I t ' s easier to re m e m b e r a three-i tem list than a 30-i tem list. If you have 30 things to 
remember , the first thing you need to do is to divide the long list into a small number of 
shorter lists. Group similar i tems together, n a m e the groups , and then associate the i tems 
in each list with the group to which i t be longs . Instead of trying to r e m e m b e r 30 things, 
you have reduced your task to r emember ing a much smaller number . 
E x a m p l e : F igure 5.5 illustrates the different s ed imentary env ironments on Earth. 
Note that while 11 sedimentary environments are discussed, they are organized into three 
general kinds of environments : continental , shorel ine, and mar ine . You are likely to 
r emember the information bet ter if you chunk i t into the three categories ra ther than 
trying to absorb the details of all eleven examples . The authors of Understanding Earth 
must agree. Not ice that they have organized the information to help you think in te rms of 
just three general categories (continental, shoreline, marine) for sedimentary environments . 
No te also the color coding. W h y did the authors choose part icular colors for each 
environment . Use these clues to study more effectively and improve your retention of 
the information. 
Sedimentation: Rocks Formed by Surface Processes 
First, overview the processes involved in forming sedimentary rocks . Study Figure 5.1 
and commit the six steps in the figure to memory . 
Next, work on Figure 5.5 on text page 109, which illustrates c o m m o n sedimentary envi-
ronments on Earth. Note that a l though 11 sedimentary envi ronments are discussed, they are 
organized into jus t three kinds of envi ronments . For now focus most of your attention on 
understanding the three and don ' t get lost in the details of all 11. 
Move on to diagenet ic processes on pages 114-116 . Figure 5.12 provides a great visual 
overview. It chunks lots of information. Here ' s a little m e m o r y trick: You can recall all the 
information in this figure story by r emember ing jus t two words : process and sediments. 
Here's how it works . First, notice that Steps 1-5 describe the three s imple processes (pres-
sure, compact ion, and cementa t ion) that are a part of d iagenesis . Next look at Step 6. Observe 
how pressure t ransforms different sediments into different kinds of rocks with very different 
textures. There are four sediments (mud, sand, gravel, and organic matter) . So you have two 
short lists to r emember : the list of three processes and the list of four sediments . If you can 
remember the sediments (mud, sand, gravel, organic matter) you can easily guess the rock 
that each turns into. So you can commi t the entire table to m e m o r y by memor iz ing a very 
short two-word list: processes (3) and sediments (4). You should be able to r emember the rest 
of the table by associat ion. Try it! 
Move on to classification on page 116. Sedimentary rock classification involves many, 
many details. Not ice , however, that you can reduce all these details to two basic categories: 
(1) clastic sedimentary rocks (Table 5.3 and Figure 5.15) and (2) chemical /b iochemical sedi-
mentary rocks (Table 5.4 and Figure 5.17). Hint: If you are a visual or kinesthetic learner, it 
may help to work up your own simplified version of these tables. 
If you want to test your knowledge of the chapter, the following materials can be used for 
self-testing and applying your new knowledge to some very interesting geologic problems. 
• Practice Exercises and Review Questions. At the very least do Exercise 1. It 
gets to the key information you need to learn in this chapter. 
• Text. Read Earth Issues on page 124. Study it to learn more about the formation 
of coral reefs. This is a mus t if you like to scuba dive! A n s w e r Exercises 1, 2, 
and 5. Also work on Thought Quest ions 3, 5, 7, 10, and 12 (refer to pages 
3 7 3 - 3 8 0 in Chapte r 16). W h e n you visit the Grand Canyon in Arizona, you 
will be able to unders tand the geology better and impress your traveling part-
ners after comple t ing these exercises and quest ions . 
• Web Site Study Resources 
http :/ /ww w. whfreeman .com/ unders tandingear th5e 
In the Geology in Pract ice exercises on the Web site, you can try your hand 
at identifying and reconstruct ing the interesting story told by sedimentary 
rocks. Identifying Sedimentary Environments, Common Sedimentary Environ-
ments, and Depositional Environments are Web site exercises that will also pro-
vide you an opportunity to pract ice using information and skills highl ighted in 
this chapter. 
Exam Prep 
Materials in this section are most useful during your preparat ion for quizzes and exams . The 
Chapter S u m m a r y and the Practice Exercises and Review Quest ions should simplify your 
chapter review. Read the Chapter S u m m a r y to begin your session. It provides a helpful 
overview that should refresh your memory. 
68 PART II C H A P T E R 5 
Chapter Summary 
What are the major processes in the formation of sedimentary rocks? 
• Weather ing and erosion produce the clastic particles and dissolved ions that 
compose sediment . Water, wind, and ice transport the sediment to where i t is 
deposi ted. Burial and diagenesis harden sediments into sedimentary rocks . 
Refer to Figure 5 .1 . 
How does plate tectonics relate to sedimentary rock? 
• Sedimentary environments , the composi t ion and texture of sediments , and the 
geometry of the basins in which sediments accumula te are all related to plate 
tectonic sett ings. For example , the formation of a new ocean basin by rifting 
along a divergent plate boundary creates a rift basin and ul t imately a stable 
continental margin and ocean basin. Refer to Figure 5.4. 
What is the relationship between sediments and 
environments on the Earth's surface? 
• Sedimentary envi ronments are often grouped into three general locat ions: on 
the cont inents , near the shorel ine, and in the ocean. 
• F a c t o r s that influence the sediments in these envi ronments include (1) kind 
and amount of water, (2) topography, and (3) biological activity. 
• Sedimentary structures and fossils provide information about the agent of trans-
port (water, wind, or ice) and the environment of deposit ion for the sediment . 
What are the major types of sediments and sedimentary rocks? 
• The two major types of sediments are siliciclastic and chemica l /b iochemica l . 
Siliciclastic (also known as clastic) sediments are formed from rock part icles 
and mineral fragments. Chemica l and biochemical sediments or iginate from 
the ions dissolved in water. Chemical and biochemical reactions precipitate these 
dissolved ions from solution. 
• Classification and the n a m e of clastic sediments and sedimentary rocks (con-
glomerate , sandstone, shale) are based primarily on the size of the grains within 
the rock. The classification and n a m e of chemical and biochemical sediments 
(evaporites, l imestones , and dolostone) in sedimentary rocks are based pr ima-
rily on their composi t ion. 
How is sediment transformed into hard rock? 
• Burial and diagenesis t ransform loose sediments into hard rock. Burial pro-
motes this transformation because buried sediments are exposed to increasingly 
higher pressures and temperatures . Diagenesis involves many physical and 
chemica l p rocesses . For e x a m p l e , cemen ta t ion i s an impor t an t chemica l 
Next , work on the Pract ice Exercises and Rev iew Quest ions . Comple t e the exercises 
and quest ions jus t as you would an exam, to see how well you have mastered this chapter. 
After you answer the quest ions, score them. Finally, and mos t important , review each ques-
tion you missed . Identify and correct the misconcep t ion(s ) that resul ted in your answering 
the quest ion incorrectly. 
70 PART11 C H A P T E R 5 
Exercise 3: Clastic and chemical sediments and sedimentary rocks 
Given the descriptive s ta tements in co lumn 1, fill in co lumns 2 and 3 of the table with the 
appropria te sediment types and rock types from the list of c o m m o n sediment types and sedi-
mentary rocks . 
Sediment types Sed imentary rocks 
biochemical . arkose dolos tone l imestone sandstone 
clastic chert evaporite peat shale 
chemical conglomera te g raywacke phosphor i te si l tstone 
Descriptive statement Sediment type Sedimentary rock example 
C o m p o s e d largely of rock fragments 
Precipi ta ted in the envi ronment of deposi t ion 
Important source of coal 
Often formed by diagenesis chemical dolostone and phosphorite 
Formed from abundant skeleton fragments 
of mar ine or lake organisms, such as coral , 
seashel ls , and foraminifers 
Produced by physical weather ing 
Produced from rapidly eroding granit ic and 
gneissic terrains in an arid or semi-arid c l imate 
Sedimentation: Rocks Formed by Surface Processes 69 
diagenetic change in which minerals are precipi tated in the open spaces within 
clastic sediments , forming cements that b ind the sediments together. 
• Figure 5.12 summar izes how diagenetic processes p roduce changes in co mp o -
sition and texture. 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Common sedimentary environments 
Using Figures 5.1 and 5.5 as a guide, fill in co lumn 2 in the following table with the clastic 
or chemical sediment (e.g., sand, silt, mud, salts, carbonate , peat) that best match the envi-
ronments of deposi t ion. 
Environment of deposition Sediment deposited 
Alpine or glacial river channel 
Dunes in a desert 
Flood plain along a broad meander bend 
River delta along a mar ine shorel ine 
Continental shelf 
Deep sea adjacent to a continental shelf 
Shoreline sand dunes 
Tidal flats 
Organic reef 
Exercise 2: Grain sizes for clastic sedimentary rocks 
Using the terms for sediments and rocks listed in Table 5.3, fill in the blanks in columns 3 and 
4 with the appropriate names of the sediments and rocks that match the typical particle size of 
the common object. A few answers have been filled in as a reference. 
Grain size Common object 
Coarse 
Fine 
football or bus 
p lum or l ime 
pea or bean 
coarse-ground pepper or salt 
fine-ground pepper or salt 
ta lcum powder or baby powder 
Sediment Rock type 
boulder gravel 
conglomerate 
sandstone 
Sedimentation: Rocks Formed by Surface Processes 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. Which of the fol lowing rock groups includes only clastic sedimentary rocks? 
A. dolomite , gypsum, and l imestone 
B. cherts , sandstone, and shale 
C. dolomite , coal , and l imes tone 
D. shale, sandstone, and conglomera te 
2 . Which sequence of rock n a m e s has the correct a r r angemen t in order of decreas ing 
part icle d i ame te r s? 
A. conglomera te , shale, sandstone 
B. shale, si l tstone, sandstone 
C. sedimentary breccia , shale, sandstone, c laystone 
D. conglomera te , sandstone, c laystone 
3. The grains in a sandstone may include 
A. rock fragments . 
B. quartz . 
C. feldspar. 
D. all of the above. 
4. Sedimentary rocks are produced through which of the following sequences of events? 
A. erosion, weather ing , t ransportat ion, deposi t ion, burial , and diagenesis 
B. weather ing, erosion, t ransportat ion, burial , d iagenesis , and deposi t ion 
C. erosion, weather ing , deposi t ion, t ransportat ion, and cementa t ion 
D. weather ing, erosion, t ransportat ion, deposi t ion, burial, and diagenesis 
5. Dolomite is the pr imary mineral found in dolos tone. It is formed by 
A. foraminifera extracting minerals from seawater. 
B. diagenetic alteration of calcite. 
C. direct precipitat ion in lake water. 
D. coral reef exposure to direct sunlight. 
Test-Taking Tip for Multiple-Choice Exams 
When taking a multiple-choice test, treat each alternative answer as a true-false quest ion. 
Rule out any alternative that is false. For example in Quest ion 4, A and C are false 
because erosion mus t follow weather ing. B is false because deposi t ion mus t preceed 
burial and diagenesis . Therefore , D mus t be the correct answer. 
6. What are the two mos t important diagenet ic processes that t ransform loose sediments 
into hard sedimentary rocks? 
A. compact ion, cementa t ion 
B. transportat ion, burial 
C. erosion, t ransportat ion 
D. uplift, erosion 
72 PART II C H A P T E R 5 
7. W h a t are t w o chemica l or b iochemica l sed imentary rocks fo rmed by the diagenetic 
p rocess? 
A. dolostone, phosphor i te 
B. l imestone, chert 
C. sandstone, l imestone 
D. sil tstone, g raywacke 
8. W h e r e are most sediments deposi ted? 
A. on the continental shelf and adjacent ocean floor 
B. in lakes 
C. a long s t reams 
D. in deserts 
9. In which of the following materials would you least expect to find cross-bedding? 
A. sand dunes 
B. delta sediment 
C. river bar deposi ts 
D. evapori tes 
10. The most widespread envi ronment of deposi t ion for carbonates in the world today is 
A. the deep sea, e.g., the Arctic Ocean . 
B. the tidal flat environment , e.g., the Mississippi Delta. 
C. in river channels . 
D. a warm, shal low-water mar ine environment , e.g., the Florida Keys. 
11 . A sandstone m a d e of pure quartz grains is likely to be deposi ted 
A. a long the shore of a continent. 
B. in the deep sea. 
C. in river channels . 
D. a long the edges of a coral reef and atolls. 
Hint: Refer to Figure 5.16. 
12. Chemica l weather ing is mos t dominant in 
A. warm, dry c l imates . 
B. warm, wet c l imates . 
C. cool , dry cl imates . 
D. cool , wet cl imates . 
E. at the shorel ine. 
13. The coast of Alaska is known for its high mounta inous relief, active volcanoes , and gla-
ciers that reach to the sea. W h a t types of sediments would you expect to be commonly 
deposi ted offshore from this landscape? 
A. arkose 
B. carbonate sand 
C. quartz sand 
D. g raywacke 
Hint: Refer to Figure 5.16 and the text that p recedes it. 
—~ 14. W h e n a granite is subject to intense chemical weather ing , i t is mos t l ikely to result in a 
JL B sediment composed of 
Review Chapte r 16, A. feldspar and clay. 
Weather ing , Eros ion, and B. quar tz and ca lc ium carbonate . 
M a s s Wast ing. C. quartz and clay. 
D. quartz and feldspar. 
Figure 5.14. The relative abundance of the major 
sedimentary rock types. In comparison with these types, all 
other sedimentary rock types—including evaporates, cherts, 
and other chemical rocks—exist in only minor amounts. 
15. Feldspar is the most abundant silicate mineral in the crust of the Earth; the most com-
mon sedimentary rock is 
A. sandstone. 
B. conglomera te . 
C. l imestone. 
D. shale. 
16. A coarse sandstone with asymmetr ical r ipples and small-scale cross-bedding is exposed 
in a cliff be tween layers of siltstone above and gravels below. Wha t is the envi ronment 
of deposit ion for the coarse sandstone layer? 
A. beach 
B. river channel 
C. lake 
D. offshore. 
H i n t : Refer to F igure 5 .11 . 
17. Reefs and atolls are built by coral and algae 
A. on subsiding oceanic volcanoes and continental margins . 
B. on islands in the middle of lakes. 
C. in the deep ocean floor and later uplifted to sealevel. 
D. where dolos tone is t ransformed to l imestone. 
18. As seawater evaporates , precipitat ion of soluble salts occurs in which order? 
A. halite, carbonates , calc ium sulfate 
B. calcium sulfate, halite, carbonates 
C. iron oxide, quartz , peat 
D. carbonates , ca lc ium sulfate, halite 
19. Mechanisms by whichplate tectonic processes p roduce sedimentary basins are 
A. rifting, thermal sag, and flexure of the l i thosphere. 
B. heating and compress ion of the crust. 
C. weather ing and erosion. 
D. diagenesis and turbation. 
Sedimentation: Rocks Formed by Surface Processes 73 
CHAPTER 6 
Metamorphism: 
Modification of Rocks by 
Temperature and Pressure 
Metamorphism: Modification of Rocks by Temperature and Pressure 75 
Chapter Preview 
• What causes m e t a m o r p h i s m ? 
Brief answer: Metamorph i sm—al te ra t ion of preexist ing rocks in the solid s t a t e— 
is caused by increases in pressure and temperature and by reaction with chemical 
components introduced by migrat ing fluids. See Figure 6 .1 . 
• What are the var ious k inds of m e t a m o r p h i s m ? 
Brief answer: Regional and contact me tamorph i sm are the mos t c o m m o n . See Figure 
6.3 and Figure Story 6.4. 
• What are the chief types of m e t a m o r p h i c rocks? 
Brief answer: Metamorph ic rocks fall into two major textural classes called foliated 
with minerals oriented in some preferred direction such as the grain in wood and 
nonfoliated with no preferred mineral orientat ion. See Table 6 . 1 . 
• How is m e t a m o r p h i s m l inked to plate tectonics? 
Hint: Refer to Figure 6 .3 . 
Vital Information from Other Chapters 
Review the sections Metamorph ic Rocks and The Rock Cycle . These sections are short and 
well worth your review. 
During Lecture 
Keeping up with a fast-speaking lecturer can be a chal lenge. 
• Take as many notes as you can. 
• Don ' t s top wri t ing w h e n you b e c o m e confused and you want to ponde r a 
concept. You can do that later. 
• If you miss something, leave a space so that you can fill it in later. 
Note-Taking Tip: Use abbreviations to speed up your note taking 
met rock -> metamorphic rock 
sed rock -» sedimentary rock 
si -+ slate or slaty 
si cleave -> slaty c leavage 
shl -> shale 
shst -> schist 
fol ->• foliated 
unfol -> unfoliated 
gran -> granular 
reg m -> regional me tamorph i sm 
con m -* contact me tamorph i sm 
Feel free to make up your own abbreviations. The important thing is to develop shorthand 
that is meaningful to you, while being quick, easy to use, and easy to remember. 
Before Lecture 
76 PART II C H A P T E R 6 
Intensive Study Session 
We r e c o m m e n d giving the highest priority to activities that involve answer ing questions. 
Answer ing quest ions whi le using your text and lecture notes as reference material is far more 
efficient than rereading chapters or glancing over notes. As a lways , you have three sources 
from which to choose quest ions . 
• Pract ice Exercises and Review Quest ions . Use the Pract ice Exercises and 
Review Quest ions at the end of this Study Guide chapter. Exercise 1 will help 
you sort out the kinds of rock discussed in this chapter. N o w that you have 
studied the three rock types in detail , i t 's t ime to integrate the information. 
Exercise 2 will help you rise above the details and gain an overview by com-
par ing igneous, sedimentary, and metamorphic rocks . 
• Text. For this chapter, the most important figures are Figure 6.1 (pressure and 
temperature), Figure 6.3 (types of metamorphism), and Figure 6.10 (plate tecton-
ics). The most important table is Table 6.1 (classification). Complete Exercises 1, 
6, 8, and 9 and Thought Questions 5, 6, 8, and 10 at the end of the chapter. 
• W e b Site Onl ine Rev iew Exercises and Study Tools 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Comple te the G r a d e d Onl ine Quiz and W e b Rev iew Quest ions . Pay part ic-
ular at tention to the explanat ions for the hints and answers . F lashcards will 
he lp you learn new terms. T h e Geo logy in Pract ice exercises provide an 
opportunity to pract ice identifying metamorphic rocks and reviewing geologic 
settings in which they occur. Comple te the Onl ine Rev iew Exercises What 
happens where? Metamorphism and plate tectonics, Create a metamorphic 
rock, and Before and after: Metamorphic rocks to review and reinforce what 
you have learned in the text. 
After Lecture 
Review Notes 
Review your notes right after lecture whi le material is fresh in your mind . Here is some 
me tamorph ic rock mater ial to add to your notes . 
Check Your Notes: Have you. . . 
• added key figures to focus your at tent ion? The most important figures are Figure 6.1 
(pressure and temperature) , Figure 6.3 (types of me tamorph i sm) , Figure 6.4 
(foliation). Table 6.1 (classification) is the most important table. 
• added helpful sketches? Suggest ion for Chapter 6: Metamorph ic rocks are classified 
in part by texture. Draw simple sketches of textures (slaty c leavage, phyll i te , schist, 
gneiss) to help you r emember the grades of me tamorph i sm. Close study of the photo 
a t the beginning of the chapter and Figure 6.4 will he lp you see how to do this. 
• added a summary of the graphs? Chapter 6 contains some important information in 
graphic form. Review P-T Figures 6.2, 6.7, 6.8, 6.9, and 6.10. No te that all show 
different grades of me tamorph i sm result ing from increasing pressure and temperature. 
Can you summar ize all these figures on a single page of your notes? W h a t does your 
summary sketch tell you about the formation of metamorphic rocks? 
• created a brief big picture overview of this lecture (a sketch or writ ten out l ine)? 
Sugges t ion for Chap te r 6: F igure 6.3 is key to unders tanding the tectonic sett ings 
that drive metamorph ism. Sketch a simplified version that clearly shows six geologic 
settings for me tamorph i sm. Wri te a capt ion for this figure in your own words . 
the three most common types of metamorphism within the Earth 's crust. Other 
types of metamorphism are low-grade, high-grade, and shock metamorphism. 
Vhat are the chief types of metamorphic rocks? 
• Metamorph ic rocks fall into two major textural c lasses: foliated (displaying a 
preferred orientation of minerals , analogous to the grain in wood) and the non-
foliated. The composi t ion of the parent rock and the g rade of metamorphism 
are the most important factors controlling the mineralogy of metamorphic rock. 
Metamorph i sm usually causes little to no change in the bulk composi t ion of 
rock. The kinds of minerals and their orientation do change . Minera l a ssem-
blages within me tamorph ic rocks are used by geoscientists as a guide to the 
original composition of the parent rock and the condit ions dur ing me tamor -
phism. Refer to 6.7. 
• Minera l assemblages in metamorphic rocks provide a basis for reconstruct ing 
the condi t ions that caused metamorph i sm and unders tanding more about the 
associated geologic setting. Figure 6.8 and Table 6.2 summarize major minerals 
of metamorphic facies. Figures 6.7, 6.9, and 6.10 illustrate how geologists 
study and interpret metamorphic rocks and reconstruct the condi t ions that 
formed them. 
tHow is metamorphism linked to plate tectonics? 
• Regional and high-pressure me tamorph i sm occur at convergent plate bound-
aries. Refer to Figures 6.4 and 6.10. 
• Seafloor me tamorph i sm occurs at spreading centers . 
• Contact me tamorph i sm occurs in a variety of plate tectonic sett ings where 
m a g m a bodies are generated. 
The important thing is not to stop questioning. 
— A L B E R T E I N S T E I N 
Figure 6 .8 . Changes in the mineral composition of mafic rocks, metamorphosed under conditions 
ranging from low grade to high grade. 
78 PART II C H A P T E R 6 
Exam Prep 
Materials in this section are most useful dur ing your preparat ion for exams . The Chapter 
Summary and the Pract ice Exercises and Review Quest ions should simplify your chapter 
review. Read the Chapter S u m m a r y to begin your session. It providesa helpful overview that 
should refresh your memory. 
Next, work on the Pract ice Exercises and Review Quest ions . Comple te the exercises 
and questions jus t as you would an exam, to see how well you have mastered this chapter. 
After you answer the quest ions score them. Finally, and most important , review each quest ion 
that you missed. Identify and correct the misconcept ion(s) that resulted in your answer ing the 
question incorrectly. 
Chapter Summary 
What causes metamorphism? 
• Metamorphism is the alteration in the solid state of preexist ing rocks , includ-
ing older metamorphic rocks . Increases in temperature and pressure and reac-
tions with chemical -bear ing fluids cause metamorph ism. Metamorph i sm typi-
cally involves a rear rangement (recrystall ization) of the chemical componen t s 
within the parent rock. Rear rangement of componen t s within minerals is facil-
itated by (1) h igher temperatures that increase ion mobil i ty in the solid state; 
(2) higher confining pressure that compac ts the rock; (3) directed pressure 
associated with tectonic activity that can cause the rock to shear (smear) , 
which orients mineral grains and generates a foliation; and (4) chemical reac-
tions with migrat ing fluids may remove or add materials and induce the 
growth of new minerals . 
What are the various kinds of metamorphism? 
• An overview of six types of metamorphism is provided in Figure 6.3. Regional 
metamorphism (associated with convergent plate boundaries), contact metamor-
phism (caused by the heat from an intruding body of magma) , and seafloor meta-
morphism (caused by seawater percolating at mid-ocean spreading centers) are 
Figure 6 .2 . Temperatures, pressures, and 
depths at which low- and high-grade meta-
morphic rocks form. The dark band shows 
common rates at which temperature and 
pressure increase with depth over much of 
the continents. 
Metamorph ism: Mod i f i ca t ion o f R o c k s by Temperature and Pressure 77 
Metamorphism: Modification of Rocks by Temperature and Pressure 79 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Classification of metamorphic rocks by texture 
Complete the table by filling in the blank spaces. 
Texture 
Parent rock Metamorphic rock (foliated/granoblastic) 
shale foliated 
quartz-rich sandstone 
granulite 
granite 
limestone 
homfels 
amphibolites and greenstones 
migmatite 
Study Tip: Putting it all together 
Now you have been int roduced to all three major rock types, igneous , sedimentary, and 
metamorphic. This is a good t ime to assemble what you have learned into a compar i son 
chart. A chart is an excellent way to ensure that you r e m e m b e r details about these rock 
types. Exercise 2 will help you do this. 
Exercise 2: Comparing igneous, sedimentary, and metamorphic rocks 
Complete the table by fill ing in the b lank spaces . N o t e that there m a y be m o r e than one 
reasonable answer for s o m e b l anks . 
Major mineral 
composition Texture 
Rock type 
(igneous, sedimentary, 
metamorphic) 
Rock name 
(granite, sandstone, 
marble) 
calcium carbonate nonfoliated 
quartz, K and Na feldspar, 
mica, and amphibole 
phaneritic 
clay fine-grained clastic 
(continued) 
80 PART II C H A P T E R 6 
Major mineral 
composition Texture 
Rock type 
(igneous, sedimentary, 
metamorphic) 
Rock name 
(granite, sandstone, 
marble) 
pyroxene , ca lc ium feldspar, 
and ol ivine 
basalt 
quartz monfoliated 
pebbles and cobbles of a 
variety of rock types 
f ragments of seashells and 
fine m u d 
sedimentary 
quartz , muscovi te , chlori te, 
and garnet 
metamorphic schist 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1 . W h e n existing rocks undergo metamorph i sm, they b e c o m e changed by 
A. the weather ing process at or near the surface. 
B. color and hardness . 
C. mel t ing and crystal l ization from the melt . 
D. the applicat ion of heat and pressure. 
2. Metamorphic rocks exposed at the surface are mainly products of processes acting on rocks 
A. near the Ear th ' s surface. 
B. at depths ranging from the upper to lower crust. 
C. within the mant le . 
D. within the center of continents . 
3 . General ly there are two types of metamorphic rocks: 
A. regional and contact . 
B. foliated and granoblast ic . 
C. compac ted and cemented . 
D. clastic and porphyri t ic . 
4 . Foliated metamorphic rocks typically occur in associat ion with regional me tamorph i sm 
because the 
A. orientation of rocks involved in regional me tamorph i sm favors the deve lopment of 
foliation. 
B. rock is softened by heat and squeezed by compress ive forces. 
C. parent rock is the correct type to produce foliation. 
D. pressure is very low, which al lows foliation to develop. 
Hint: Refer to Figure 6.4. 
5. Foliation develops 
A. perpendicular to compress ive forces. 
B. parallel to compress ive forces. 
C. due to high water content . 
D. due to low temperatures and pressures . 
Metamorphism: Modification of Rocks by Temperature and Pressure 81 
6. Some metamorphic rocks are distinguishable from igneous and sedimentary rocks because 
their const i tuent grains 
A. interlock, forming a cont inuous mosa ic . 
B. have qui te different chemical composi t ions . 
C. tend to be l ined up in a preferred direction. 
D. are rounded and cemented together. 
7. Chemical compos i t ions of me tamorph ic rocks are de termined by the 
A. pressures to which they have been subjected. 
B. effects of both tempera ture and pressure . 
C. tempera ture to which they have been raised. 
D. composi t ion of the original rocks and fluids that percolate through the rock during 
me tamorph i sm. 
8. Metamorphism affects 
A. only older igneous rock. 
B. any younger igneous and metamorph ic rock. 
C. only older sedimentary rock. 
D. any older igneous , sedimentary, or metamorphic rocks . 
9. Which me tamorph ic sequence correctly shows increasing grain size? 
A. schist -» gneiss ->• phylli te -> slate 
B. slate -> phyll i te ->• schist -> gneiss 
C. gneiss -> phyllite-"- slate -> schist 
D. phylli te -> slate ->• gneiss -> schist 
10. Starting with the lowest t empera ture zone , which series of index minerals is character-
istic of increasing metamorph ic grade? 
A. chlorite, bioti te, garnet , si l l imanite 
B. garnet, chlori te , bioti te, kyani te 
C. biotite, garnet , chlori te , s i l l imanite 
D. chlori te, bioti te, s i l l imanite, kyani te , garnet 
Hint: Refer to F igure 6.7. 
11. On the M o o n , the major cause of me tamorph i sm is 
A. burial. 
B. subduct ion. 
C. meteor impacts . 
D. very cold tempera tures . 
12. Of the me tamorph ic rocks listed, which one is formed at the highest tempera ture? 
A. slate 
B. schist 
C. phyll i te 
D. gneiss 
Hint: Refer to Figure 6.7. 
13. The difference be tween a gneiss and a granite is that the gneiss 
A. has a different bulk chemica l composi t ion . 
B. shows a distinct foliation. 
C. has a different mineral composi t ion . 
D. is general ly less coarse grained. 
14. Schist and slate are dis t inguishable in that 
A. schist is fine grained, whereas slate is coarse grained. 
B. schist is foliated, whereas slate is not foliated. 
C. slate is fine grained, whereas schist is coarse grained. 
D. slate is foliated, whereas schist is not foliated. 
82 PART II C H A P T E R 6 
15. Regional me tamorph i sm is found in associat ion with 
A. lava flows. 
B. hot springs. 
C. very low pressures. 
D. subduct ion zones and cores of mounta in ranges . 
16. If gneiss or another metamorphic rock is heated to a degree that it begins to melt , 
A. the quartz, K-feldspar, and Na-r ich plagioclase wouldstart to mel t f i rs t . 
B. N a - C a plagioclase, biotite, and minerals (such as garnet) would mel t f irst , leaving a 
res idue rich in felsic minerals . 
C. all the minerals in the rock would start to mel t at essential ly the same temperature 
to form a m a g m a of the same composi t ion of the gneiss . 
D. the ferromagnesian minerals would start to mel t f i rst . 
H i n t : Refer to Figure 4 .5 . 
17. As m a g m a intrudes into a host or country rock (the preexis t ing rock that is in contact 
with the intrusion), it is t ransformed into a new rock. W h a t is this process cal led? 
A. regional me tamorph i sm C. recrystal l ization 
B. contact me tamorph i sm D. schistosity format ion 
18. In the Web Geology in P r a c t i c e exercise, Gravels to Metaconglomerate, oval quartz peb-
bles apparently become converted into cigar-shaped features within a metaconglomerate. 
How would you explain the transformation? 
A. The cigar-shaped features formed as larger quartz pebbles were tumbled in a stream 
channel before me tamorph i sm. 
B. As the oval quartz pebbles b e c a m e exposed to elevated tempera tures , they softened 
and stretched out in response to directed pressure . S o m e of the quar tz may have also 
recrystal l ized along direct ions perpendicular to the directed pressure . 
C. Quar tz is an index mineral for h igh-grade me tamorph i sm associated wi th burial of 
sedimentary rocks . Therefore, this conglomera te must have been uplifted from near 
the bo t tom of the crust. 
D. The conglomerate melted and the large cigar-shaped features are large quartz crystals. 
H i n t : The bo t tom of Figure 4.5 provides an important c lue to the tempera ture at which 
minerals begin to melt and solidify (crystall ize). 
19. You are on a summer backpacking trip in Alaska with friends and find an outcrop of mica 
schist with large garnet porphyroblasts , like the sample shown in Figure 6.6. Your friends 
quickly scramble to collect some garnet crystals. They then ask you about the conditions 
under which the beautiful garnet crystals formed. W h a t is your response to their query? 
A. Garnet-bear ing schists are formed from iron-rich m a g m a s that solidify underground. 
B. Garnet is an index mineral for low-temperature and low-pressure metamorph ism asso-
ciated with meteor impact craters. So we must be within an ancient impact crater. 
C. Garnet commonly occurs in mica schists and is an index mineral for intermediate- to 
h igh-grade metamorph i sm, associated with regional me tamorph i sm. This rock may 
have at one t ime been in the roots of a huge mounta in . 
D. Garnets occur only in eclogites. Therefore, this rock must have begun at the base of 
the crust and been exposed by extensive uplift and erosion occurring in this region. 
20. Whi le s tudying some metamorphic rock samples for an undergraduate research project, 
you discover evidence that the rocks were exposed to h igh-grade me tamorph ic condi-
t ions. Fur ther study reveals that the garnets within the rock show a history of prograde 
fol lowed by re t rograde P-T paths . You check the f ie ld notes from the geologis t w h o col-
lected the samples and are not surprised to find ment ion of ophiol i tes in the region 
(refer to Figures 4 .12 and 6.9). You conclude from this information that me tamorph ic 
rocks formed when 
A. cont inents coll ided. 
B. m a g m a intruded into a volcano associated with a subduct ion zone. 
C. a meteori te hit the Earth. 
D. hydro thermal fluids altered rock in an area with numerous hot springs and geysers . 
Figure 6.10. P-T paths and rock assemblages assoc ia ted with (a) o c e a n - c o n t i n e n t plate 
convergence and (b) c o n t i n e n t - c o n t i n e n t plate convergence. T h e P-T paths differ in i l lustrating the 
lower geothermal grad ients present in subduc t ion zones . Rocks t ranspor ted to similar d e p t h s — 
and p ressures—beneath mounta in bel ts become much hotter at an equivalent dep th . 
Me tamorph i sm: Mod i f i ca t i on o f R o c k s by Temperature and Pressure 8 3 
CHAPTER 7 
Deformation: 
Modification of Rocks by 
Folding and Fracturing 
Figure 7.19. Last stage in the development of a geologic province. Refer to Figure 7.15 (1) 
for a more regional perspective on this type of deformation. 
Before Lecture 
Before you at tend lecture, be sure to spend some t ime previewing the chapter. For an effi-
cient preview, use the Study Guide C h a p t e r P r e v i e w ques t ions as a f ramework for under-
s tanding the chapter. Prev iewing works best i f you do i t j u s t before lecture . Wi th the main 
points in mind , you will unders tand the lecture better. This in turn will resul t in a bet ter and 
m o r e comple te set of notes . 
8 4 
Deformation: Modification of Rocks by Folding and Fracturing 85 
Study Tip 
Rock deformation lectures are particularly visual. Slide material on folds and faults can 
be confusing if you have never seen these geologic features before. So be sure to preview 
the figures before attending lecture. For an overview, start with Figure 7.7. Notice how 
three kinds of force p roduce three kinds of faults if the material is britt le. Wha t happens 
if the material is ducti le or plast ic? 
How much t ime should you devote to previewing? Obviously, more t ime is better than less. 
But even a brief (five- or ten-minute) preview session jus t before lecture will p roduce a result 
that you will not ice . For a refresher on why previewing is so important , see Study Guide , Part 
1, Chapter 3, H o w to Be Successful in Geology. 
Chapter Preview 
• What are geologic m a p s and cross sect ions? 
Brief answer : Geologic maps represent the rock formations exposed at the Ear th ' s 
surface. Geologic cross sect ions are d iagrams showing how the geologis t interprets or 
projects the geology at the surface into the subsurface. Refer to Figure 7.4. 
• How do rocks deform (break or bend)? 
Brief answer: Rocks typically break (fault) when the temperature is low, burial is 
shallow, and the force is applied quickly. Rocks typically bend (fold) when the 
temperature is higher, burial is deeper, and the force is applied over a long period. 
See Figures 7.7 and 7.10. 
• What geologic features are produced w h e n rocks deform? 
Brief answer : Folds , faults, and jo in ts are c o m m o n geologic structures produced when 
rocks are deformed. 
• What do geologic s tructures produced by rock deformat ion tell geologists a bo ut 
the geologic history of a region? 
Brief answer: T h e type(s) of folds, faults, and jo in ts and their spatial orientation 
provide geologis ts wi th clues for decipher ing the kinds of forces affecting a region 
over t ime. See F igure 7.19. 
Vital Information from Other Chapters 
After each lecture you need to thoroughly master the concepts covered before you attend the 
subsequent lecture. T h e ideas of geology are like a stack of boxes . Each new idea rests on all 
ideas (boxes) s tacked benea th it. 
Another look at Chapte r 3 would serve you well . Since there is a strong connect ion 
between deformation and me tamorph i sm, review Figure 6.4 and the section on Plate Tecton-
ics and M e t a m o r p h i s m in Chapter 6. 
Web Site Study Resource 
ht tp: / /www.whfreeman.com/understandingearth5e 
The Online Rev iew Exerc ise Tectonic Forces in Rock Deformation in t roduces you to the 
basic terminology and concepts covered in this chapter. 
86 PART II C H A P T E R 7 
Note-Taking Tip 
Figures of faults and folding can be d rawn very s imply once you unders tand them. 
But until you do, m a k e i t easy on yourself. Photocopy Figures 7.7 and 7.10. Three-hole-
punch them for easy insertion into your three-ring notebook. If they are already in your 
notebook before lecture, you cannot be distracted drawing them during lecture.Education is a voyage in self-discovery. 
— L A U R E N C E M . G O U L D 
After Lecture 
Review Notes 
The perfect t ime to review your notes is r ight after lecture. The fol lowing checkl is t contains 
both general review tips and specific suggest ions for this chapter. 
Check Your Notes: Have you. . . 
( I added visual material? Suggest ion: Test your unders tanding of Chapte r 7 by adding to 
your notes s imple sketches of important geological features such as normal , reverse, 
and thrust faults, and an anticl ine, syncline, asymmetr ic fold, and overturned fold. 
Add capt ions to help you keep things straight. (For example , "Associate the word 
' s ink ' to the V in syncl ine. 'S ink ' is what a syncl ine resembles .") 
• created a brief big picture overview of this lecture (a sketch or writ ten out l ine)? 
Suggest ion: Figure 7.7 is a good one-page summary of brittle rock deformat ion. 
Intensive Study Session 
Because there is a lot to learn in this chapter, be sure to set priorit ies for s tudying. There is 
probably more material than you will have t ime to study in one intensive study session. We 
r e c o m m e n d that you give highest priority to activities that involve answer ing quest ions . 
Answer ing quest ions whi le using your text and lecture notes as reference mater ial is far more 
During Lecture 
One goal for lecture is to leave class with good answers to the preview quest ions . 
• To avoid ge t t ing lost in de ta i l s , keep the b ig p ic tu re in mind . C h a p t e r 7 tel ls 
the s tory of th ree k inds of forces ( compress ive , t ens iona l , and shear ing) and 
h o w geo log is t s find ev idence of these forces in rock s t ruc tures (folds and 
faults) . 
• Deformat ion lectures are part icularly visual . Slide material on folds and faults 
can be confusing if you have never seen these geologic features before. Keep 
Figures 7.7 and 7.10 on hand during lecture. 
Deformation: Modification of Rocks by Folding and Fracturing 
efficient than reading chapters or glancing over notes . As a lways , you have three sources from 
which to choose ques t ions : 
• Pract ice Exerc ises a n d Rev iew Quest ions Be sure to do Exercise 1. It 
involves the key information you need to learn in this chapter. 
• Text. This is a very visual chapter, so focus your attention on unders tanding the 
figures. Mos t of the really essential material for this chapter is in Figures 7.7 
and 7.10, so focus on unders tanding these illustrations first. Answer Exercises 
1, 4, and 5 at the end of the chapter. 
• Web Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Complete the Onl ine Rev iew Quest ions . Pay particular attention to the hints if 
you get bogged down. T h e Geology in Practice exercise Folds, Faults, and 
Other Records of Rock Deformation provides an opportunity for you to practice 
your skills identifying and interpreting classic examples of rock deformation. 
The F lash Cards will help you learn the new terminology. The Onl ine Review 
Exercises Tectonic Forces in Rock Deformation and Types of Folds will help 
you organize your knowledge about the different features of folds and faults. 
Exam Prep 
Materials in this section are mos t useful during your preparat ion for quizzes and exams . T h e 
Chapter S u m m a r y and the Pract ice Exercises and Rev iew Quest ions should simplify your 
chapter review. Read the Chapter S u m m a r y to begin your session. It provides a helpful 
overview that should refresh your memory . 
Next, work on the Pract ice Exerc ises and Rev iew Quest ions . Comple te the exercises 
and questions jus t as you would an exam, to see how well you have mastered this chapter. 
After you answer the ques t ions , score them. Finally, and most important , review each ques-
tion you missed. Identify and correct the misconcept ion(s) that resulted in your answer ing the 
question incorrectly. 
Chapter Summary 
What are geologic maps and cross sections? 
• Geologic maps represent the rock formations exposed at the Ear th 's surface. 
The orientation of rock layers is measured as strike and dip. Refer to Figure 7.3. 
• Geologic cross sect ions are d iagrams showing how the geologis t interprets or 
projects the geology at the surface into the subsurface. Refer to Figure 7.4. 
How do rocks deform (bend and break)? 
• All rocks may bend (ducti le behavior) and break (brittle behavior) in response 
to the application of forces. Laboratory exper iments have revealed that whether 
a rock exhibits ducti le or brittle behavior depends on its composi t ion, temper-
ature, depth of burial (confining pressure) , and the rate with which tectonic 
processes apply force. 
• Ductile behavior is more likely when a rock is sedimentary and exposed to 
higher tempera tures , deeper burial , and slower applicat ion of tectonic forces. 
Brittle behavior is favored w h e n rocks are igneous or h igh-grade metamorphic 
and cooler, closer to the Ear th ' s surface, and exposed to more rapid applica-
tion of tectonic forces. 
88 PART II C H A P T E R 7 
What geologic features are produced when 
rocks deform? 
• Fold ing is a resul t of duct i le deformat ion. F r o m the type of fold and its ori-
entat ion, geologis ts can interpret the or ientat ion of the tec tonic forces and 
character is t ics of the rock layers dur ing deformat ion. 
• Faul t ing and jo in t ing are a result of brittle deformation. Joint ing occurs when 
a rock fractures but there is little movemen t a long the fracture p lanes . Faul ts 
are fractures along which there is appreciable movemen t (offset). T h e type and 
orientat ion of faults and jo in ts provide valuable information about the tectonic 
forces and the characterist ics of the rock layers at the t ime of deformat ion. 
What do geologic structures produced by rock 
deformation tell geologists about the history of a region? 
• T h e type of fold or fault p rovides a means for geologis ts to interpret the type 
of tec tonic force act ing on the rock dur ing deformat ion. Tectonic forces can 
be of three types : compress ive , tensional , and shear ing forces. T h e s e forces 
are active at all three types of plate tectonic boundar ies : compress ive forces 
domina te at convergent boundar ies (where plates coll ide or subduct) ; tens ional 
forces domina te a t divergent boundar ies (where plates are pul led apar t ) ; and 
shear ing forces domina te at t ransform faults (where pla tes slide hor izonta l ly 
past each other) . 
• Geologic structures such as folds, faults, and jo in ts occur on all scales from 
microscop ic to the size of a mounta ins ide . Geologis t s deduce the geo log ic 
history of a region in part by unravel ing the history of deformation, thereby 
reconstruct ing what the rock units looked like before deformat ion. 
• Regional deformational fabrics (the types of faults and folds in evidence) can 
help geologists decipher the plate tectonic history of the region. For example , 
normal faulting suggests that a region is be ing stretched l ike a rubber band by 
tensional forces. Refer to Figures 7 .15, 7.16, 7.17, 7.18, and 7.19. Cons ider 
h o w the geologic c i rcumstances in F igure 7.16 are similar but also somewha t 
different from those depicted in Figure 7.15 (1 Tensional tectonics) . 
Figure 7.16. (b) A rift valley results from tensional forces and normal faulting. 
The African Plate, on which Egypt rides, and the Arabian Plate, bearing Saudi Arabia, 
are drifting apart. The tensional forces have created a rift valley, filled by the Red 
Sea. The diagram shows parallel normal faults bounding the rift valley in the crust 
beneath the sea. 
Defo rmat ion )eformation: Modification of Rocks by Folding and Fracturing 89 
ly Guide . 
at room temperature , it exhibits 
e putty quickly, it will snap into 
moldedinto many shapes. Plus , 
opert ies of Silly Putty with the 
Geologic structure produced 
of force by this style of deformation 
nal 
•essional 
ill of putty is 
•essed by the 
t with the floor. 
hquakes. (Earthquakes are attributed to the elastic 
name the (A) geologic structure 
sional, shearing) responsible for 
)oundary (convergent, divergent, 
iated. 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Silly Putty 
Silly Putty is a popular teaching aid with geologists because , at r o o m tei 
all three deformat ion characterist ics of solids. If you pull on the putty qui 
two pieces. Handled slowly, the putty can be easily bent and molded int 
a ball of it th rown on the floor will bounce . C o m p a r e the propert ies ol 
behavior of rocks by comple t ing the table. 
Behavior of 
Silly Putty Behavior of rock Type of force 
Snaps into pieces tensional 
Bends ductile 
Bounces elastic 
compressional 
The ball of putty 
compressed by h 
impact with thej 
Rocks do exh ib i t e last ic behavior . Mo re on this when we study earthquakes. (E 
properties of r ocks . ) 
Exercise 2: Geologic structures 
For each of the following five illustrations of deformed rocks, name the I 
(normal fault, syncline); (B) type of force (compressional, tensional, she 
producing each geologic structure; and (C) the plate tectonic boundary (i 
or shear) with which the geologic structure is commonly associated. 
A. Geologic structure 
B. Type of force 
C. Commonly associated plate tectonic boundary 
D. Geologic structure 
E. Type of force 
F. Commonly associated plate tectonic boundary 
90 PART II C H A P T E R 7 
Exercise 3: Anticline versus syncline 
A. Briefly descr ibe the diagnost ic differences be tween an anticline and a syncl ine. 
B. Draw a picture of a typical outcrop pattern for a plunging syncline exposed at the surface. 
Refer to F igure 7 .11 . 
G. Geologic structure 
H. Type of force . 
I . C o m m o n l y associated plate tectonic boundary 
J. Geologic structure 
K. Type of force . 
L . C o m m o n l y associated plate tectonic boundary 
M. Geologic structure 
N. Type of force 
O. C o m m o n l y associated plate tectonic boundary 
Defo rmat ion : Mod i f i ca t i on o f R o c k s by F o l d i n g and F rac tu r ing 91 
92 PART II C H A P T E R 7 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. A rock that breaks suddenly in response to the applicat ion of forces is 
A. elastic. 
B . plastic. 
C. brittle. 
D. ducti le. 
2 . T h e two measurements that define the orientation of an exposed rock layer are 
A. strike and dip. 
B. strike and slip. 
C. slip and dip. 
D. fold axis and tilt. 
3. The sense of mot ion along the San Andreas fault in California is 
A. left lateral strike slip. 
B. r ight lateral strike slip. 
C. dip slip. 
D. thrust. 
4. As tensional forces are applied to a cont inental region, the result ing geologic feature 
will be a(n) 
A. anticl ine. 
B. rift valley. 
C. thrust fault. 
D . dome . 
Hint: Refer to Figures 7.7 and 7.15. 
5. W h e n no offset can be detected along a fracture in a rock, the fracture is called a 
A. stress plane. 
B . jo int . 
C. fault. 
D. rupture . 
6. W h i c h of the following condi t ions p romotes ducti le deformat ion of rocks? 
A. old igneous rocks within the interior of a cont inent 
B. rocks deforming at a relatively low temperature 
C. stress building up rapidly to a very high level 
D. rocks subjected to high confining pressures and tempera tures 
7. W h e n deformed, which of the following rocks is more likely to fracture britt lely instead 
of flow ducti lely? 
A. basal t 
B. shale 
C. pure l imestone 
D. muddy sandstone 
8. As mol ten rock cools near or at the surface, i t can develop shr inkage fractures that 
extend vertically down into the rock body. These cr isscrossing, regularly pat terned frac-
tures create long thin rods of rock we call 
A. shr inkage pal isades. 
B. tension faults. 
C. co lumnar jo in ts . 
D. e longate jo in ts . 
Hint: Refer to the photo at the beginning of Chapter 4. 
Deformation: Modification of Rocks by Folding and Fracturing 
9. W h i c h of the fol lowing geologic structures is caused by tensional forces? 
A. thrust fault 
B. reverse fault 
C. anticl ine 
D. normal fault 
10. Thrust faults c o m m o n l y form 
A. around hot spots. 
B. where cont inents are col l iding. 
C. where cont inents are pull ing apart. 
D. a long a t ransform fault. 
11. The direct ion of dip is defined by a line 
A. at r ight angles to the strike line. 
B. nor th of the strike line. 
C. parallel to the strike line. 
D. parallel to p lunge . 
Hint: Refer to F igure 7 .3 . 
12. F r o m an airplane you not ice that the outcrops of tilted layers of rock m a k e a distinct 
z igzag pat tern across a plain. You reasonably conc lude that the 
A. area has been cut by numerous normal faults. 
B. layers are folded into a series of p lunging folds. 
C. layers are folded into a series of nonplunging folds. 
D. layers have been tilted so that all the layers dip in the same direction. 
Hint: Refer to F igures 7 .11 . 
CHAPTER 8 
Clocks in Rocks: 
Timing the Geologic Record 
Clocks in Rocks: Timing the Geologic Record 95 
Before Lecture 
Time-Management Tip: 
Something is always better than nothing 
How much t ime should you devote to previewing? Obviously, the more time, the better. 
However, even a brief (five or ten minutes) preview session jus t before lecture will 
produce not iceable results . Arrive ten minutes early for lecture. Use the t ime to preview 
the chapter for the day ' s lecture. Even if you have only a minute or two you can read the 
preview quest ions and brief answers and gain a rough idea of what the chapter is about. 
The t ime jus t before lecture is precious , because whatever you preview will remain in 
short-term m e m o r y and help you unders tand lecture. 
Chapter Preview 
• H o w can the relative ages of rocks be determined from rock outcrops? 
Brief answer : The principles of superposi t ion, fossils, and cross-cutt ing relat ionships 
provide a basis for establ ishing the relative age of a sequence of rocks at an outcrop. 
For example , in Figure 8.4 and Eai th Issues 8 .1 . the younges t sedimentary rock layers 
are on top and the oldest are at the bot tom. And in Figure 8.10, m a g m a intrusions 
and a fault are younger than the rock they cut through. 
• H o w can the relative ages of rock outcrops at two or m o r e locat ions be 
determined? 
Brief answer : Strat igraphic and fossil succession, plus radiometr ic dates of rock units, 
provide a basis for establ ishing how rock outcrops at different localities may be 
related to each other (correlate), even if they are hundreds or thousands of miles apart. 
See Figure 8.5. 
• W h a t is the Geolog ic T i m e Scale and how is it cal ibrated? 
Brief answer : The Geologic T ime Scale is the internationally accepted reference 
for Ear th ' s geologic history. Using relative and absolute dat ing methods , geologis ts 
have cal ibrated (divided) Ear th ' s history into four eons : Hadean , Archean, Proterozoic , 
and Phanerozoic . Because more evidence is available for the most recent eon, the 
Phranerozoic , i t has been possible to divide it more finely into eras, per iods , and 
epochs. See Figures 8.10 and 8.14. 
• How are the Geolog ic T i m e Scale and geochronological methods , like radiometr ic 
dating, appl ied to geologic problems? 
Brief answer: We unders tand Ear th ' s history to the degree to which we can place the 
record of geologic events in t ime. The Geologic Time Scale is the accepted standard 
for how geologic t ime is subdivided.Vital Information from Other Chapters 
Review Figure 1.13 (the r ibbon of geologic t ime from the formation of the solar sys tem to 
present). Review the text section The R o c k Cycle : Interact ions be tween Plate Tectonic and 
Climate Sys tems in Chapte r 3. Reread the Atomic Structure of A t o m s section in Chapter 3 
before reading about radiometr ic dat ing methods . Also preview Figure 9.10 on page 198. 
Time is simply nature's way of keeping everything 
from happening at once. 
— G R A F F I T I ON A WALL 
During Lecture 
Here ' s an overview that should help you take good notes for this lecture. 
• Big Picture. The big picture for this lecture is the entire Geologic T ime Scale! 
Geologic t ime is wondrous ly huge . It is so expansive that at first it seems 
incomprehens ib le . The lecturer will descr ibe the 4.5-bi l l ion-year expanse of 
geologic t ime and m a y use examples and exercises des igned to he lp you grasp 
geologic t ime. 
• N e w Terms. I t is difficult to talk about the Geologic T ime Scale wi thout refer-
ring to its t ime intervals. So you m a y feel barraged with new te rms: epochs , 
per iods, eras , eons , Holocene , Ple is tocene, Pl iocene. To avoid gett ing lost, 
keep a copy of Figures 8.11 and 8.14 at hand. Refer to Figure 8.14 to check 
te rms as needed. Note how different-sized chunks of t ime are used for differ-
ent eons : huge chunks (eons) are used for events early in Ear th ' s history w h e n 
there is less geological evidence for wha t happened , and smaller chunks 
(epochs) are used for intervals of t ime closer to the present . Because m o r e evi-
dence is available for the mos t recent eon, the Phanerozoic , i t has been divided 
more finely into eras, per iods, and epochs . See Figure 8.14. 
• Success ion of Geologic Events . You will work through how the relative ages 
of rocks are determined. By the end of lecture you will be able to use two basic 
principles (superposi t ion and cross-cutt ing) to de termine the relative age of a 
sequence of rocks such as that shown in F igure 8.10. 
• Abso lute Dating. Carbon-14 has a short half-life. It works for dat ing younger 
samples of t issue at tached to bone , charcoal , and w o o d because these mater i -
als all conta in carbon. Other isotopes (uran ium-238, po tass ium-40 , rub id ium-
87) have m u c h longer half-lives and are used to date rocks that are geologi -
cally older. Table 8.1 shows how half-life is related to the effective dat ing 
range of each method . 
After Lecture 
Review Notes 
The perfect t ime to review your notes is r ight after lecture. T h e following checkl is t contains 
both general review tips and specific suggest ions for this chapter. 
Check Your Notes: Have you. . . 
• shown clearly how superposit ion and cross-cutt ing features can be used to sequence 
rock units and geologic events? Hint: A s imple sketch is the best way to show this, 
shown clearly the characterist ics of (1) an unconformity and (2) an angular 
unconformi ty? Check Figures 8.6, 8.7, and 8.8 against your notes. Add sketches to 
your notes if you need to. 
Clocks in Rocks: Timing the Geologic Record 97 
Intensive Study Session 
The two big tasks for this s tudy session are to master the skill of dat ing outcrops using the 
principles of superposi t ion and cross cutt ing and to learn the Geologic T ime Scale. 
Begin your work on outcrops with Study Guide Exercise 1. The other exercises and the 
review quest ions will al low you to test your skills further. Refer to your notes and relevant 
text figures to help you. 
We are like the butterflies who flutter 
for a day and think it is forever, 
— C A R L SA GA N 
Unless you happen to have spent your s u m m e r work ing on an archeology dig , tossing a round 
terms like Pa leocene , E o c e n e , and Ol igocene , the epochs of the Cenozo ic m a y look like a 
steep m e m o r y curve . Here are four different strategies for learning the Geologic T ime Scale . 
1. M a r k e r events are s imply interest ing things that happened: animals or plants that 
evolved, creatures that domina ted the Earth, large extinction events. Look at Figure 
8.11. Select some marker events you already know about. E x a m p l e : Can you guess one 
of the per iods dur ing which dinosaurs were dominan t? The movie Jurassic Park has 
made this an easy quest ion to answer. W h e n did complex life begin? Find some other 
marker events of part icular interest to you. You may find yourself surprised at how early 
some events occurred. Marke r events will help you r e m e m b e r the Geologic T ime Scale. 
Try Exerc ise 3. 
2. Logical c h u n k s . Group the information into short lists you can remember . Study the 
groupings of the t ime scale with Figures 8.11 and 8.14 in front of you. Learn it as a 
series of short lists. Unders tand the following logic. 
• E o n s (Figure 8.14) are the biggest t ime chunks . There are only four (Hadean, 
Archean, Proterozoic , Phanerozoic) to remember . Only the mos t recent (Phanerozoic 
eon) is broken down further. Hadean sound like Hades (hell), not a bad descript ion of 
the young planet wi th its mol ten surface and asteroids crashing into it. 
• Eras (Figure 8.11) are next biggest . You have to learn eras only for the Phanerozoic 
eon. Tha t ' s because geological evidence is too l imited to justify the division of ear-
lier eons . There are only three Phanerozoic eras to r emember : Old Life, Midd le Life 
and New Life. Th ink of them that way first ; you can tack on the Greek stems later. 
• Periods (Figure 8.11) are next. Al l three eras of the Phanerozoic eon are further 
divided into per iods . No periods for earlier eons : not enough evidence. 
• Epochs are the smallest divisions of geologic t ime. You have to learn epochs only for 
the mos t recent era (Cenozoic , or New Life). All epochs of the Cenozoic end in 
-cene (for "Cenozo ic" ) . 
Now that you unders tand the divisions, return to Figure 8.14, which clarifies how they all fi t 
together and adds the absolute dates that have been de termined by reading the radiometr ic 
rock clocks. 
3. W o r d S tems . Word stems are clues to meaning . Greek and Latin s tems are used a great 
deal by scientists. You can look them up in any good dictionary. A few helpful stems for 
the Geologic T ime Scale follow. , 
Eras 
Paleo- = Greek: "o ld" 
Meso- = Greek: "midd le " 
Ceno- = Greek: " n e w " 
-zoic = Greek: " l i fe" 
Epochs : D o n ' t worry about the middle epochs for now. Just r e m e m b e r the first and last 
ones . 
Paleo - Greek: "o ld" 
Pleisto = Greek: "much ." R e m e m b e r that there was much ice in the Pleis tocene. 
Holo = Greek: "recent." Remember that the Holocene is the present or most recent epoch. 
Note that all epochs of the Cenozoic epoch end in -cene. 
4. M n e m o n i c (catch phrase) . W h e n there are long lists of unfamil iar te rms to learn (such 
as the epochs of the Cenozoic) , many learners find mak ing catch phrases helpful. Try 
this . Do Exerc ise 4 , Geologic T ime Scale mnemon ic . 
W e b Site Onl ine Rev iew Exercises and Study Tools 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Take the G r a d e d Onl ine Quiz and pay part icular attention to the feedback for answers. 
Flashcards will help you learn new terms. Work with Field Relationships for Relative 
Time Dating and the Geologic Time Scale Review Onl ine Rev iew Exercises . 
No vestige of a beginning, no prospect of an end. 
— J A M E S H U T T O N 
( 1 7 2 6 - 1 7 9 7 ) 
Exam Prep 
Mater ia ls in this section are mos t useful during your preparat ion for examinat ions . The 
Chapter S u m m a r y and Pract ice Exercises and Rev iew Quest ions should simplify your 
chapter review. Read the Chapter S u m m a r y to begin your session. I t provides a helpful 
overview that should refresh your memory.Chapter Summary 
How can the relative ages of rocks be determined 
from rock outcrops? 
• The principles of superposi t ion and cross-cut t ing relat ionships provide a basis 
for establ ishing the relative age of a sequence of rocks at an outcrop. Us ing 
these two principles , geologists can order (determine what happened first, sec-
ond, third, and so on) the geologic events represented by the rocks and geo-
logic features in rock outcrops . The principle of original horizontal i ty for sed-
imentary layers provides a starting point for identifying sequences of 
sedimentary rocks affected by tectonic forces after they were deposi ted. 
How can the relative ages of rock outcrops at two 
or more locations be determined? 
• To reconstruct the geologic history of the Earth, geologists need to correlate 
the geologic events represented by rocks at one locality with the geologic 
events represented by rocks at other localit ies. The stratigraphic and fossil suc-
cession and the radiometr ic dates of rock units show how rock outcrops at dif-
ferent locali t ies may be related to each other, even if they are hundres or thou-
sands of mi les apart . 
What is the Geologic Time Scale and how is it calibrated? 
• The Geologic T ime Scale is the internationally accepted reference for the 
sequence of events represented by Ear th ' s rock record. Geologis ts constructed 
i t over about the last 200 years using mainly fossils, superposi t ion, and cross-
cutt ing re la t ionships to establish the relative ages of thousands of rock out-
crops around the world. In about the last 60 years , the Geologic T ime Scale 
has been cal ibrated us ing radiometr ic me thods derived from the discovery of 
radioact ive isotopes by physicis ts in the early part of the twentieth century. 
• The G e o l o g i c T i m e Sca le , l ike the theory of p la te t ec ton ics or any o ther sci -
entific t heo ry or too l , i s a lways open to the cha l l enge of new ev idence . B u t 
i t i s i m p o r t a n t to unde r s t and that the Geo log i c T i m e Sca le is rooted deep ly 
not j u s t in geo logy but in phys i c s , chemis t ry , b io logy , and pa leon to logy . I t 
is o n e of s c i ence ' s grea t founda t ions , a concep t that i f ser iously cha l l enged 
by ha rd e v i d e n c e (it has not been ) w o u l d force reappra i sa l of m a n y disc i -
pl ines of sol id w o r k i n g sc ience . Fo r i t to be w r o n g , m u c h of geo logy wou ld 
have to be w r o n g , and subs tant ia l a reas of phys ics wou ld have to be w r o n g , 
and mos t of b iology and paleontology would have to be wrong . An error of this 
magni tude is very unlikely. Thus (for most practical purposes) the Geologic 
Time Scale is a s sumed as fact by virtually all scientists and scientifically lit-
erate people . 
How are the Geologic Time Scale and geochronological 
methods like radiometric dating applied to geologic problems? 
• We unders tand Ear th ' s history to the degree to which we can place the record 
of geologic events in t ime. The Geologic T ime Scale is the accepted s tandard 
for how geologic t ime is subdivided. Ear th Issues 8.1 provides an example . 
Figure 8.12. The radioactive decay of 
rubidium to strontium. 
Clocks in Rocks: Timing the Geologic Record 99 
Using this information, unit 1 is 
a. older than uni t 12 but younger than unit 11 . 
b. younger than uni t 12 but older than unit 11 . 
c. older than unit 11 but younger than unit 12. 
2 . Expla in the logic you used to answer quest ion E - l . 
Exercise 2: Ordering geologic events 
In the illustration, a geologic outcrop reveals three layers of sedimentary rocks , one fault, and 
a single igneous dike intrusion. 
A. Order the sequence of geologic events from younges t to oldest. 
Clocks in Rocks: Timing the Geologic Record 1 01 
Youngest 
Oldest 
B. Briefly describe the geologic history represented by the rock sequence. 
Exercise 3: Marker events for the Geologic Time Scale 
A. Enter each event in the list in the appropria te eon box in the table. W h e n there is more 
than one event in a box , order them so that the oldest is at the bo t tom and the younges t 
is at the top. 
Significant (Marker ) Events in Earth History 
Dinosaur extinction Major phase of continent formation completed 
Earliest evidence of life Moon forms 
End of heavy bombardment of the Earth First nucleus-bearing cells develop 
Evolutionary Big Bang Oxygen buildup in atmosphere 
Humans evolve 
B. Fill in the names of eras, periods, and epochs in the correct sequence from oldest at the bot-
tom to youngest at the top. Refer to both Figures 1.13 and 8.11 to complete this exercise. 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Determining the succession of geologic events 
The fo l lowing b lock d i ag ram i l lustrates the geo logy of an a rea in Argen t ina . Answer the 
ques t ions regard ing the geologica l his tory of this area. Ci rc le the cor rec t answer when a j 
cho ice is p rovided . 
1 0 0 PART II C H A P T E R 8 
Unit 2 contains clasts of units 3 through 10. 
Unit 5 contains clasts of units 6 through 10. 
Units 5 through 10 are baked along their contacts with unit 11 . 
Units 1, 2 , 8 , % and 11 are baked along their contacts with dike 12. 
A . W h i c h unit i s the younges t rock i n this area? 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 
B . W h i c h unit i s the oldest rock i n this area? 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 
C. 1. Is uni t 3 older than unit 12? Yes No Not poss ible to know 
2. Expla in the logic you used to answer quest ion C - l . 
D. 1. Is unit 1 younger than unit 11 ? Yes No Not poss ible to k n o w 
2. Explain the logic you used to answer quest ion D - l . 
E. 1. In an at tempt to further work out the geologic age relat ionships in this area, samples 
of units 1, 11 , and 12 ( igneous rocks) were collected for radiometr ic dating. The 
resulting counts of radioactive parent a toms and daughter a toms are listed in the table. 
Rock unit N o . Parent a toms N o . Daughte r a toms 
1 500 500 
11 250 750 
12 750 250 
Eon 
Phanerozo ic 
Humans evolve 
Proterozoic 
First nucleus-bearing cells 
develop 
A r c h e o n 
H a d e a n 
Earth accretion begins 
Era Period 
Quaternary 
Tertiary 
Mesozoic 
Jurassic 
Pennsylvanian 
Ordovician 
Epoch 
Holocene 
Pleistocene 
Nothing lives long but the earth and the mountain. 
— C H A R L E S B A L L A R D 
Exercise 4: Geologic Time Scale mnemonic 
Construct a mnemonic device for remembering the Geologic Time Scale names . The first letter 
of each word must match the first letter of the corresponding period or epoch in the proper order. 
You may use your native language, but be careful not to mix up the words when you do so. 
Examples (refer to Figures 8.11 and 8.14 for the Geologic T ime Scale) : 
Per iods of the Geologic T ime Scale 
Chronically Overworked Student Decks Monotonous Physics Professor To 
Justify Contradictory Test Questions. 
Epochs of the Cenozoic : 
Please Eat Our Mushroom Pot Pie Hot. 
Now invent your own mnemonic to help you r e m e m b e r the Geologic T ime Scale. 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. The pr inciple of superposi t ion holds that for any unfolded series of sedimentary layers, 
A. overlying strata extend over a b roader area than the layers benea th them. 
B. the layer at the top of the pile is a lways younger than the layers benea th it. 
C. sediments generally accumulate in the vertical sands tone-sha le - l imes tone sequence. 
D. the layer at the top of the pile is a lways older than those benea th it. 
2. F r o m younges t to oldest, the correct sequence of eras dividing the Phanerozoic eon is 
A. Paleozoic, Cenozo ic , Mesozo ic . C. Mesozo ic , Paleozoic , Cenozoic . 
B . Mesozo ic , Cenozo ic , Paleozoic . D. Cenozoic , Mesozo ic , Paleozoic . 
3. The epochs of the Tertiary per iod progress from oldest to younges t in which sequence? 
A. Eocene , Ol igocene , Paleocene , Miocene , Pl iocene 
B. Pa leocene , Eocene , Ol igocene , Miocene , Pl iocene 
C. Pa leocene , Eocene , Miocene , Pl iocene, Ol igocene 
D. Pa leocene , Eocene , Ol igocene , Miocene , Pl iocene, Pleis tocene 
4. F r o m oldest to younges t , the correct order of per iods for the Paleozoic era is 
A. Cambr ian , Ordovic ian , Devonian , Silurian, Mississ ippian, Permian , Pennsylvanian. 
B. Cambr ian , Ordovic ian , Silurian, Devonian , Mississ ippian, Pennsylvanian, Permian . 
C. Cambr ian , Silurian, Ordovic ian , Pennsylvanian, Miss iss ippian, Devonian , Permian . 
D. none of the above. 
5. Sandstone and shale rock layers immedia te ly be low and above an angular unconformity 
imply a his tory of 
A. erosion, deposi t ion, and deformation erosion. 
B. erosion, deformation, deposi t ion, and erosion. 
C. deformat ion, erosion, deposi t ion, and deformation. 
D. deposi t ion, deformation, erosion, and deposi t ion. 
H i n t : Refer to F igure 8.8. 
6. F rom the d iagram, one can infer age l imits for rock layer 3 of 
A. be tween 34 and 60 mil l ion years . 
B . be tween 30 and 60 mil l ion years . 
C. less than 20 mil l ion years . 
D. more than 60 mil l ion years . 
C l o c k s i n R o c k s : T i m i n g the G e o l o g i c R e c o r d 1 03 
7. Wha t m a k e s the isotopes of a given e lement different from each other? 
A. their a tomic number s 
B. their number of e lectrons 
C. their n u m b e r of neutrons 
D. their n u m b e r of protons 
8. Natural ly occurr ing that decay(s) into other mater ia ls at known 
rates can be used to es t imate the actual age of a rock. 
A. organic mat ter C. radioact ive e lements 
B. minerals D. silicon 
9. T h e Phanerozoic t ime is divided into three intervals: (1) the interval of old life, (2) the 
interval of middle life, and (3) the interval of modern life. These intervals correspond 
(from oldest to younges t ) to the 
A. Archean , Mesozoic , and Paleozoic . 
B. Paleozoic , Precambrian , and Proterozoic . 
C. Precambr ian , Cambr ian , and Neocambr ian . 
D. Paleozoic , Mesozo ic , and Cenozoic . 
10. W h i c h radiometr ic dat ing method would be mos t effective in de termining the age of 
charcoal at an archeological site? 
A. rub id ium-s t ron t ium C. u r a n i u m - l e a d 
B. rad iocarbon D. po t a s s ium-a rgon 
H i n t : Refer to Table 8.1 in your textbook. 
11 . Only geological ly young mater ia ls can be dated using radioact ive C-14 isotopes 
because 
A. the decay rate varies widely over t ime. 
B. they have a very short half-life. 
C. within decades all the C-14 is decayed away. 
D. they are a very rare isotope. 
12. If the half-life of some radioactive e lement is 1 bil l ion years and a mass of rock origi-
nally conta ined 1000 a toms of the radioactive e lement , how many a toms of the radioac-
tive e lement would be left after 3 bil l ion years had passed? 
A. 500 a toms C. 125 a toms 
B. 250 a toms D. no radioactive a toms 
13. Smal l p ieces of charcoal from an ancient ruin yield a ca rbon-14 date of 3000 years . This 
age best represents the approximate interval of t ime that has e lapsed since 
A. a fire burned the wood. C. h u m a n s cut the wood. 
B. h u m a n s inhabited the ruin. D. the w o o d died. 
14. Radiometric dates have been attached to the Geologic Time Scale by the determination of 
radiometr ic ages of 
A. igneous rocks younger and older than sedimentary formations. 
B. shales. 
C. fossil skeletons. 
D. me tamorphosed sediments . 
15. For the mos t part, radiometr ic dates for rocks represent only the last t ime the rock 
A. crystall ized from a m a g m a or C. b e c a m e cemented , 
was metamorphosed . D. was deposi ted. 
B . was eroded. 
16. O n e me thod that geologists use to study buried sediments and unconformit ies is 
A. seismic stratigraphy. C. deposi t ional stratigraphy. 
B. radiometr ic stratigraphy. D. metamorphic stratigraphy. 
H i n t : Refer to F igure 8.15. 
17. If a rock is heated by me tamorph i sm and the daughter a toms generated by the decay of 
the radioact ive parent a toms migra te out of a mineral that is subsequent ly radiometri-
cally dated, the date will be the actual age. 
A. younger than C. the same as 
B. older than D. none of the above 
1 04 PART II CHAPTER 8 
18. W h i c h sample of basal t in the d iagram is likely to yield the most accurate K/Ar radio-
metr ic date? 
Clocks in Rocks: Timing the Geologic Record 1 05 
A. A B . B C. C 
19. A layer of cong lomera te contains cobbles of an igneous rock. O n e of the cobbles was 
dated radiometr ical ly at 35 mil l ion years old. F r o m this radiometr ic age, the cong lom-
erate layer can be inferred to be 
A. more than 35 mil l ion years old. C. 35 mil l ion years old. 
B. less than 35 mil l ion years old. D. none of the above. 
20. In the i l lustration, wha t is the mos t recent geological event depic ted? 
A. erupt ion of the lava 
B. faulting 
C. intrusion of the pluton 
D. deposi t ion of shales, sandstones and l imestones 
21. Pieces of charcoal were found in a paleosoi l layer cover ing an ancient fire pit with stone 
tools including ar rowheads and axes. T h e charcoal was radiometr ical ly dated us ing car-
bon-14 and yie lded an age of approximate ly 10,500 years . W h a t can you infer about the 
age of the archeological site? 
A. The archeological site is about 10,500 years old. 
B. The archeological site is younger than 10,500 years . 
C. The archeological site is older than 10,500 years . 
D. The age of the archeological site is unresolved but m a y be older than 10,500 years . 
CHAPTER 9 
Early History of the 
Terrestrial Planets 
Before Lecture 
Chapter Preview 
• H o w did our solar sys tem form? 
Brief answer: It accreted from gas and dust about 4.5 billion years ago. 
Figure 9.2 shows this process beautifully. Look it over before lecture. 
• H o w did the Earth form and change over t ime? 
Brief answer: The Ear th ' s core, mantle , crust, oceans , and a tmosphere evolved as the 
interior of the planet heated up, melted, and differentiated. S tudy Figures 9.5 and 9.6. 
1 0 6 
Early History of the Terrestrial Planets 1 07 
After Lecture 
The perfect t ime to review your notes is r ight after lecture, whi le the material is still fresh in 
your mind. Review to be sure you noted all the key points and wrote them down in a form that 
will be readable later. As you review, you can also add useful visual mater ial and a summary. 
Check Your Notes: Have you. . . 
• annotated your notes for focused learning? Usual ly the most efficient way to do this 
is by (1) under l in ing or highl ight ing key points and (2) adding headings or key 
words in the margin (you do set up your notes with a left-hand margin, don ' t you?) . 
Hint: Preview quest ions m a k e great headings . 
For addit ional ideas about annotat ing notes go to the following link: 
ht tp: / /www.csbsju.edu/academicadvis ing/help/ lec-note .htm 
• added a s imple sketch or two to clarify the key points? 
• written a brief (one-paragraph) summary of the most important concept you learned 
from this lecture? Feel free to use your notes and the figures in your text as needed. 
Reviewing preview quest ions may help . 
Intensive Study Session 
For this chapter the mos t efficient study approach is to start with the two pract ice exercises. 
Practice Exercise 1 will help you mas ter the basics of planet formation. Then turn to Practice 
Exercise 2. W h e n we are learning about a new subject, we all have a tendency to focus on the 
"what"(what we know) rather than the " h o w " (how do we know it)—the supporting evidence. 
Yet to carry out an intelligent conversation and write a good response to a discussion question 
in homework or on an exam, we need to be able to explain the evidence for our statements and 
observations. The observation that there is water on Mars begs for a detailed explanation. How 
do we know there is water on Mars? Before the next lecture, rough out an answer to Practice 
Exercise 2 (also refer to Exercise 6 at the end of Chapter 9 in the textbook). As questions arise 
about how a line of evidence serves to support the presence of water on Mars , write the ques-
tions down and ask the instructor about them via e-mail or during the next class meeting. 
• W h a t are s o m e m a j o r events in the history of our solar sys tem? 
Brief answer: The age of the solar sys tem as determined from meteori tes is about 
4.56 billion years . The major planets formed within about 10 million years, and they 
differentiated into a c o r e - m a n t l e - c r u s t layering in less than 100 mill ion years . The 
Moon formed from a giant impact at about 4.5 Ga. Minerals as old as 4.4 billion years 
have survived in the Ear th ' s crust. 
• W h a t do p lanetary surfaces tell us about their age? 
Brief answer: Samples from the surface of the M o o n have been dated by isotopic 
methods . The age of other planetary surfaces is est imated from the density of 
impact craters . 
• What have we learned from recent planetary probes? 
Brief answer: Venus is the only planet other than Earth that has active tectonics 
controlled by global convect ion of its mant le . Water is present on Mar s only as ice at 
its poles and in the shal low subsurface. In the past, water may have been present as 
a liquid on the Mar ian surface. 
108 PART II C H A P T E R 9 
Web Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Check out the study aids available on the Web site. You will find Concept Self-Checker, Web 
Rev iew Quest ions , Graded Onl ine Quiz , Onl ine Rev iew Exercises , and Flashcards (to 
help you learn new terms) . The Onl ine Rev iew Exercise Mars Field Trip provides an oppor-
tunity for you to explore some of the geologic features on Mars . You will learn how the sur-
face features present today tell planetary geologists about condi t ions and processes that have 
shaped Mars during its history. 
Exam Prep 
Materia ls in this section are mos t useful during your preparat ion for exams. The Chapter 
S u m m a r y and Pract ice Exercises and Review Quest ions should simplify your chapter 
review. Begin your review with the Chapter Summary . It provides a helpful overview that 
should refresh your memory. 
Next , work on the Pract ice Exercises and Rev iew Quest ions . Comple te the exercises 
and quest ions jus t as you would an exam, to see how you have mastered this chapter. After 
you answer the quest ions, score them. Finally, and mos t important , review each question you 
missed. Identify and correct the misconcept ion(s) that resulted in your answering the ques-
tion incorrectly. 
Chapter Summary 
How did our solar system form? 
• Our solar system probably formed when a c loud of interstellar gas and dust 
condensed about 4.5 billion years ago. The planets vary in chemica l composi-
tion in accordance with their dis tance from the Sun and with their size. 
How did the Earth form and change over time? 
• Ear th probably grew by accretion of coll iding chunks of matter. Very early 
after the Earth formed, i t is thought that our M o o n formed from material 
ejected from the Earth by the impact of a giant meteori te . 
• Heat generated from the Moon-forming impact and the decay of radioactive 
e lements probably caused much of the Earth to melt . Mel t ing a l lowed iron and 
other dense matter to sink toward the Ear th ' s center and form the core . Lower 
density (lighter) matter floated upward to form the mant le and crust. Release 
of t rapped gases (mostly water) from within the Earth gave rise to the oceans 
and an early a tmosphere . In this way, the Earth was t ransformed into a differ-
entiated planet with chemical ly distinct zones : an iron core; a mant le of mostly 
magnes ium, iron, silicon, and oxygen; and a crust rich in oxygen, silicon, alu-
minum, ca lc ium, potass ium, sodium, and radioactive e lements . 
• As the Ear th cooled, an outer relatively rigid shell called the l i thosphere 
formed on top of a hotter and softer as thenosphere . Volatiles t rapped within the 
mant le escaped through volcanoes to form Ear th ' s a tmosphere and oceans. 
Life evolved and developed the capabil i ty of extracting carbon dioxide out of 
surface environments and releasing oxygen as a by-product of photosynthesis . 
Refer to Chapter 11 . 
The interaction of major components of Earth 's system continues to this day. 
What are some major events in the history of our solar system? 
• T h e age of the solar system as determined from meteori tes is about 4 .56 bil-
lion years . The major planets formed within about 10 mil l ion years , and they 
differentiated into a c o r e - m a n t l e - c r u s t layering in less than 100 mil l ion years . 
The M o o n fo rmed f rom a giant impac t a t about 4.5 Ga. Mine ra l s as old as 
4.4 bi l l ion years have survived in the Ear th ' s crust. Refer to Figure 9.10. 
What do planetary surfaces tell us about their age? 
• Samples from the surface of the M o o n have been dated by isotopic methods . 
The age of other planetary surfaces is es t imated from superposi t ion and the 
density of impact craters. 
What have we learned from recent planetary probes? 
• Venus is the only planet other than Ear th that has active tectonics control led by 
global convect ion of its mant le . Refer to Figure 9.15. 
• Water is present on Mar s only as ice at its poles and in the shal low subsurface. 
In the past, water m a y have been present as a l iquid on the Mar ian surface. 
• The Cass in i -Huygens p robe found that Saturn ' s r ings extended hundreds of 
ki lometers f rom the planet and were m a d e up of bil l ions of particles of ice and 
rock—part ic les ranging in size from grains of sand to houses . 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide. 
Exercise 1: The evolving early Earth 
Fill in the b lanks in the fol lowing flowchart , which character izes a popular hypothesis for the 
early history of the Ear th after the Sun and planets had formed (refer to parallel f lowchart) . 
Early History of the Terrestrial Planets 1 09 
1 1 0 PART II C H A P T E R 9 
Exercise 2: Evidence of water on Mars 
Discuss four lines of evidence revealed by recent Mar ian probes of water (past and present) 
on Mars . 
H i n t : Start by mak ing a list of lines of evidence ment ioned in this chapter. P ick the four 
that you unders tand the best and then discuss how each supports the presence of water on 
Mars , bo th in the past and at present. 
Figure 9 .26 . St rat igraphy exposed a long the flank of Endurance Crater, (a) T h e record can be read 
in the ou tc rop and dep ic ted as an interpretive drawing that shows each s tage in the h is tory of the 
environment, (b) T h e vert ical success ion of layers in this ou tc rop preserves an excel lent record of 
ear ly Mart ian envi ronments. 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. Dur ing the formation of our solar sys tem, what was the process that caused dust and 
condens ing mater ial to accrete into p lanetes imals? 
A. nuclear fusion 
B. rapid spin of the protosun 
C. heat ing of gases 
D. gravitat ional attraction and mater ial coll is ions 
2. A major source of internal heat in the Ear th today is 
A. ocean tides. 
B. radioactivity. 
C.solar energy. 
D. volcanoes . 
Test-Taking Tip 
When taking a test, be alert to i tems that give away the answers to other i tems. 
E x a m p l e : Quest ion 12 provides a hint for answer ing quest ion 3. 
3. Which of the fol lowing processes is thought to be responsible for the formation of the 
present Ear th ' s a tmosphere? 
A. chemica l b reakdown of minerals 
B. capture of oxygen and ni t rogen from space 
C. both degass ing of Ear th ' s interior and l iberation of oxygen by photosynthesis 
D. degass ing of Ear th ' s interior 
4. From radiometr ic dates of lunar rock samples and meteori tes , how old is the Ear th esti-
mated to be? 
A. 45 mil l ion years old 
B. 4.5 bil l ion years old 
C. 10 bil l ion years old 
D. 100 bil l ion years old 
5. Geochemis ts have de te rmined that differences in the distr ibution of chemica l e lements 
in the present Ear th ' s crust, mant le , and co re—in contrast to the distribution of chemi -
cal e lements in the initial solar n e b u l a — m a y be due in part to 
A. inhomogenei t ies within the initial interstellar dust cloud. 
B. early mel t ing and differentiation of materials of varying density. 
C. cosmic ray b o m b a r d m e n t over 4.5 bill ion years . 
D. nuclear synthesis within our Sun. 
6. Why do geoscient is ts think tectonic plates move across the Ear th ' s surface? 
A. Centrifugal force of Ear th ' s rotation spins plates across the Ear th ' s surface. 
B. Volcanic erupt ions on the seafloor push tectonic plates apart. 
C. Tidal forces drive plate mot ion. 
D. M o v e m e n t of the plates is the surface manifestat ion of convect ion in the mant le . 
H i n t : Refer to F igure 9 .15. 
7. Within our solar sys tem, one big difference be tween the inner and outer p l a n e t s — 
besides size and posi t ion relative to the Sun—is their 
A. density. 
B. color. 
C. rate of formation. 
D. t ime of formation. 
Figure 9 .6 . Early volcanic activity 
contributed enormous amounts 
of water vapor, carbon dioxide, and 
other gases to the atmosphere 
and oceans, and it contributed 
solid materials to the continents. 
Photosynthesis by microorganisms 
removed carbon dioxide and added 
oxygen to the primitive atmosphere. 
Hydrogen, because it is light, 
escaped into space. 
Early History of the Terrestrial Planets 111 
8. Ear th ' s M o o n is thought to have formed by 
A. capture of a large planetary object traveling past Ear th . 
B. accret ion, jus t like the planets . 
C. material ejected from Earth by volcanic eruptions. 
D. the impact of a Mars-s ized object on Ear th very early in Ear th ' s history. 
9. The nebular origin of our solar system is character ized as 
A. a proven fact. 
B. a theory. 
C. a hypothesis . 
D. pure guesswork. 
10. B o m b a r d m e n t from space m a y be disastrous for life, but i t is also an essential process 
in the history of a planet . W h y ? 
A. B o m b a r d m e n t is how a planet grows, and residual heat from impacts may help to 
create a dynamic planet. 
B. The oceans and a tmosphere formed on Ear th as a result of bombardmen t . 
C. Impacts drive plate tectonics. 
D. Impacts keep planets from gett ing too big. 
11 . The impact ing object that caused the extinction of the d inosaurs 65 mil l ion years ago is 
es t imated to have had a radius of about 
A. 100 meters . 
B. 1 kilometer. 
C. 10 ki lometers . 
D. 100 ki lometers . 
H i n t : Refer to Table 9.2. 
12. O x y g e n released into Ear th ' s a tmosphere by photosynthes is is vital for our existence 
not only because we need i t to breathe but also because 
A. it is essential for all life on Earth. 
B. i t combines with free hydrogen gas in our a tmosphere to p roduce water. 
C. life would not have evolved wi thout oxygen. 
D. i t forms an ozone layer in the upper a tmosphere that protects us from UV radiation. 
It is in the stars. 
The stars above us, govern our condition. 
— W . S H A K E S P E A R E 
King Lear, I V , i i i 
112 PART II C H A P T E R 9 
Figure 10.1. Major tectonic features 
of North America: Canadian Shield; 
interior platform; Cordilleran orogenic 
belt; Colorado Plateau; Appalachian 
fold belt; coastal plain. 
CHAPTER 10 
Evolution of the Continents 
Evolution of the Continents 115 
Vital Information from Other Chapters 
To unders tand the evolut ion of the cont inents , you will need to draw on diverse information 
from m a n y chapters . W h i l e working on Chapte r 10, Evolut ion of the Cont inents , keep the fol-
lowing concepts in mind and review them as m u c h you need to. 
Plate Tectonics 
Divergent boundar ies (Figure 2.6) 
Convergent boundar ies (Figure 2.6) 
The forces that drive plate tectonics (Figure 1.11 and pages 3 7 ^ - 0 ) 
Igneous R o c k s 
M a g m a differentiation (Figures 4.5 and 4.11 and pages 8 5 - 8 7 in text) 
Format ion of igneous rocks at divergent and convergent plate boundar ies 
(Figures 4 .13 and 4 .14 and pages 9 2 - 9 7 ) 
Rock Deformat ion 
Folding and faulting (Figures 7.7) 
Thrust faulting (Figure 7.17) 
Folding (Figure 7.10) 
Appalachian Fold belt (Figure 7.18) 
Deve lopment of a fictitious geologic province (Figure 7.19) 
During Lecture 
One goal for lecture should be good answers to the preview questions. 
• To avoid gett ing lost in the detai ls , keep the big picture in mind. Chapter 10 
examines the geologic history of the cont inents . 
• Make a copy of Figure 10.18, the Wilson cycle, and have it handy during lecture. 
After Lecture 
Review Notes 
The perfect t ime to review your notes is r ight after lecture. The following checklist contains 
both general review tips and specific suggest ions for this chapter. 
Check Your Notes: Have you. . . 
• added notes or sketches of material from previous chapters that you need to 
understand your class notes? This is a good idea for this chapter because the chapter 
draws heavi ly on previous mater ial . Hint: Refer to the Study Guide section Vital 
Information from O t h e r Chapters . There you will f ind a helpful list of material you 
may want to review or inc lude as you rework your notes . 
• created a brief big picture overview of this lecture? Hint: T h e Wi l son cycle provides a 
useful overview of this chapter. Refer to F igure 10.18 and consider adding sketches 
and text from that figure to your notes . 
Intensive Study Session 
Set priorities for s tudying this chapter. Try to give highest priority to activities that involve 
answering ques t ions . We r e c o m m e n d the following strategy for learning this chapter. 
• Preview the fol lowing Figures: 10 .1 , 10.4, 10.8, 10 .11 , 10.12, 10.13, 10.15, 
10.16, 10.18, 10.20, and 10.24. You will need to unders tand these figures to 
answer the Rev iew Quest ions . 
1 1 4 PART II C H A P T E R 10 
Chapter Preview 
• W h a t are the major geologic features of North Amer ica? 
Brief answer: Review Figure 10.1 . Pay part icular attention to the location and charac-
teristics of the active tectonic belt in western North Amer ica and the relatively stable 
cont inent of the ancient orogenic belts, platform, and shield. Look for patterns in age 
and location. 
• H o w do cont inents grow? 
Brief answer: The silica-rich, iron-poor rocks in continents are produced mostly in 
subduction zones by magmatic differentiation and metamorphism of silica-rich sedi-
ments. Once produced, the continental rocks are difficult to subduct and recycle into the 
mantle because they are more buoyant than mantle material. Rifting and transform 
faulting typically break continents into small pieces while terrane accretion and continent 
collisions assemble pieces into larger continents. Refer to Figures 10.11 and 10.12. 
• H o w does orogeny modify cont inents? 
Brief answer: Much as a styrofoam float resists being dragged under water, silica-rich,low-density continental crust is more buoyant than the mantle, and therefore continents 
resist being subducted. Instead, continental crust is damaged (deformed) and piles up 
(thickens) at convergent plate boundaries . Intense folding, faulting, detachment, and 
thrust transport of sedimentary wedges and the formation of huge granitic batholiths 
thicken the overriding continental l i thosphere. These processes can deform continental 
crust hundreds of ki lometers from the convergence zone. Thicker continental crust 
tends to stand higher. 
• W h a t is epe irogeny? 
Brief answer: Gradual downward and upward movements of broad regions of the crust, 
without significant folding or faulting, involves a set of processes called epierogeny. 
Heat, loading and unloading, and flow within the mant le may all cause epierogeny. 
• W h a t is the Wi lson cycle? 
Brief answer: The Wilson cycle character izes the sequence of events in the opening 
and closing of an ocean basin. A new ocean basin forms when a cont inent is rifted 
apart. As an ocean basin closes due to subduct ion of its ocean l i thosphere, continents 
grow. A few t imes in Ear th ' s history, the c losure of a series of ocean basins resulted 
in the formation of a supercontinent , like Pangaea in the early Permian . Refer to 
Figures 10.17 and 10.18. 
• H o w have the Archean cratons survived bil l ions of years of plate tectonics? 
Brief answer: L ike giant sailboats, cont inents have cratonic keels that stabilize the 
raft of continental l i thosphere against the effects of convective currents in the mantle 
and plate tectonic processes . It is hypothesized that the keels consis ted of somewhat 
less dense mantle rocks that are about the same age as the Archean crust above 
them. Refer to Figure 10.24. 
Study Tip 
W h e n confronted with new scientific terminology, somet imes the dict ionary can help. 
For example , if you look up the terms epeirogeny and orogeny you will find the 
fol lowing origins for the roots of these te rms: 
epe i rogeny—Gk. epeiros, cont inent 
o rogeny—Gk. oros, mounta in 
Before Lecture 
Before you attend lecture, be sure to spend some t ime previewing the chapter. For an efficient 
preview, use the following quest ions . 
116 PART II C H A P T E R 10 
• Comple te Pract ice Exercises 1 and 2. These exercises will help you r e m e m -
ber the mos t important ideas in this chapter. 
• Work in some review time as you study the evolution of the continents. 
Reviewing is always a good idea, and it is especially important for this chapter 
because it draws on so many ideas in previous chapters. Refer to Vital Informa-
tion from Other Chapters for a list of helpful figures to review. 
• Answer the Review Quest ions. Try answering each question to check your 
understanding of the lecture. Check your answers as you go, but try to answer 
the quest ions before you look at the answers. Pay attention to the test-taking tips 
we provide. They will help you do better on your midterm. 
• Somet ime before your exam, answer all the exercises at the end of the chap-
ter. They require short answers and won ' t take long if you know the material. A 
helpful animation, Accretion of a Buoyant Fragment of a Continent, is provided 
on the Web site for Exercises 5 and 6 at the end of Chapter 10 in the textbook. 
• W e b Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Comple t e the Concept Se l f -Checker and Onl ine Rev iew Quest ions . Pay par-
ticular attention to the explanat ions for the answers . The Geo logy in Pract ice 
Exercises address the quest ion " D o cont inents float on the man t l e?" F lash-
cards will help you learn the new terminology in this chapter. 
Exam Prep 
Mater ia ls in this section are mos t useful dur ing your preparat ion for quizzes and exams. The 
Chapter S u m m a r y and the Practice Exercises and Review Quest ions should simplify chap-
ter review. Begin your session with the Chapter S u m m a r y . I t provides a helpful overview 
that should refresh your memory . 
Next , work on the Pract ice Exerc ises and Rev iew Quest ions . Comple t e the exercises 
and quest ions jus t as you would for an exam, to see how well you have mas te red this chap-
ter. After you answer the quest ions , score them. Finally, and mos t important , review each 
quest ion you missed. Identify and correct the misconcept ion(s) that resul ted in your answer-
ing the quest ion incorrectly. 
Chapter Summary 
What are the major geologic features of North America? 
• Figure 10.1 shows the major tectonic features, including the Canadian Shield, 
interior platform, Cordi l lera and Appalachian mounta in bel ts , coastal plain, 
and continental shelves. 
• Figure 10.3 shows the sedimentary basins and d o m e s of Nor th Amer ica . 
• The Appalachian fold belt and western Cordi l lera mounta in bel t are character-
ized in Figures 10.4, 10.5, and 10.11. 
How do continents grow? 
• M a g m a t i c differentiation. M a g m a s generated in subduct ion zones tend to be 
more silica-rich because (1) crastal material , like sediments , can be incorpo-
rated into the melt and (2) part ial mel t ing and crystal settling differentiate the 
iron-rich and silica-rich materials . 
Evolution of the Continents 1 1 7 
• Cont inental accretion. Plate motions accrete buoyant (silica rich) rocks to con-
tinental margins by (1) transfer of fragments from a subducting plate to a conti-
nental plate, (2) closure of marginal basins to add thickened island-arc crust to 
the continent , (3) lateral transport via strike-slip faulting along continental mar-
gins, and (4) suturing of two continental margins during their collision. Refer 
to Figures 10.11, 10.12, 10.15, 10.17, and 10.18 for illustrations and examples . 
What are epeirogeny and orogeny? 
• Epe i rogeney refers to s imple up-and-down movement s wi thout significant 
folding and faulting. Proposed mechan i sms for vertical crustal movement s are 
(1) isostatic adjustments caused by loading or unloading of the crust via accu-
mulat ion and mel t ing of glacial ice and (2) heat ing or cool ing the crust in asso-
ciation with continental rifting or a hot spot. Refer to Figure 10.20. 
• Orogeny usual ly resul ts from pla te convergence and is charac ter ized by 
sever de format ion inc lud ing extens ive fault ing and folding. E x a m p l e s of 
o rogeny inc lude the Appa lach ian and Rocky M o u n t a i n s of the Uni ted Sta tes . 
Bu t the m o s t spec tacu la r e x a m p l e on the p lanet i s the A l p i n e - H i m a l a y a n 
bel t . Refer to F igures 10.15 and 10.16 and the related sect ion of text descr ib-
ing the format ion of the H i m a l a y a s . 
How does orogeny modify continents? 
• Like a styrofoam float, the buoyant continental crust resists being dragged under 
water; silica-rich, low-density continental crust is more buoyant than the mantle, 
and therefore continents resist being subducted. Instead, continental crust is 
damaged (deformed) and piles up (thickens) at convergent plate boundaries . 
• Intense folding, faulting, de tachment and thrust t ransport of sedimentary 
wedges and the format ion of huge granitic bathol i ths thicken the overriding 
cont inental l i thosphere. 
• These processes can deform continental crust hundreds of ki lometers from the 
convergence zone. Thicker continental crust tends to stand higher. 
What is the Wilson cycle? 
• The Wilson cycle, n a m e d after J. Tuzo Wilson, is a f lowchart that summar izes 
the general sequence of events in the evolution of continental crust. Refer to 
Figure 10.18. 
• The cycle begins when the edges of continental cratons are rifted during the 
breakup of a supercontinent such as Pangaea. Rifting creates a new ocean basin 
with passive margins that collect ocean sediment. Eventually convergence 
begins,creating an active margin, with accompanying subduction, mounta in 
building, and terrain accretion. 
• From t ime to t ime dur ing Ear th ' s history, plate convergence produced super-
continents like Rod ina and Pangaea. 
How have the Archean cratons survived billions of 
years of plate tectonics? 
• The formation of silica-rich continental crust goes back at least 4.0 billion years. 
• Cratons (older and more stable parts of the continents) have keels that, like the 
hull of a sailboat, extend into the mant le . 
Evolution of the Continents 1 1 9 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Evolution of the Continents 
Comple te the sentences in the f lowchart with words from the list. Refer to Figures 10.12, 
10.15, and 10.18. 
accretion and collision intrusion of m a g m a s subducts 
continental plate m a g m a t i s m thick 
erosion ocean basin thrust faulting 
folding passive margin 
hot stable craton 
1 1 8 PART II C H A P T E R 10 
• Cratonic keels appear to consist of somewhat lower density rock, cal led peri-
dotite, that is depleted of heavier const i tuents , such as the e lement iron and the 
mineral garnet. 
• Keels appear to form at about the same t ime as the cont inental crust above it. 
• I t is hypothes ized that the cold, strong, mant le keel more than 200 km thick 
helps to preserve the cratons from disrupt ion by mant le convect ion and plate 
tectonic processes . 
Refer to F igure 10.24 . 
Nothing lives long but the earth and the mountain. 
— C H A R L E S B A L L A R D 
1 2 0 PART II C H A P T E R 10 
Exercise 2: Ocean crust versus continental crust 
Using information in Chapters 2, 4, and 10, complete the table. 
Characteristics Ocean crust Continental crust 
Compos i t i on 
Rock type(s) 
Dens i ty 
Thickness 
A g e 
Topographic 
features 
Structure /Archi tecture 
Orig in 
3.0 g/cm3 
10 km 
Abyssal floor 
Ridge with axial rift 
Trenches 
Seamounts 
Hot-spot island chains 
Plateaus 
A model for the structure of the ocean 
crust is the ophiolite suite: deep-sea 
sediments, basaltic pillow lavas and dikes, 
and gabbro. (Note: Peridotites are part of 
the mantle lithosphere, not the ocean crust.) 
Very heterogeneous—can contain any rock, 
but granitic and gneissic with a cover of 
sediments are dominant. 
2.7 g/cm3 
The ages of continental crust span 
4 billion years. 
The architecture of the continents is 
complex. It consists of preexisting cratons, 
accreted microplates, island arcs, volcanic 
arcs, suture zones, ophiolite suites, and 
belts representing ancient orogenic zones. 
Sediments cover basement rock in the 
interior platform of the continent. 
Orogenic processes and accretion of pre-
existing crustal blocks along convergent 
plate boundaries 
Review Questions 
A n s w e r s and explanat ions are provided at the end of the Study Guide . 
1. T h e massive, interior regions of cont inents that have been stable for extensive per iods 
of t ime are called 
A. mounta ins . C. cratons. 
B . pla teaus . D. plains . 
2. Intense deformation and accretion of continental crust occurs at 
A. convergent plate margins . C. hot spots. 
B. t ransform margins . D. divergent plate margins . 
3. W h i c h of the following features is not associated with o rogeny? 
A. thrust faulting C. passive cont inental margin 
B. intrusion of p lu tons D. me tamorph i sm 
4. The oldest rocks found on the continents are about 
A. 200 mil l ion years old. C. 4 bill ion years old. 
B. 1 bil l ion years old. D. 4.5 bill ion years old. 
Hint: Refer to Figures 10.8 and 10.22. 
Evolution of the Continents 1 2 
Test-Taking Tips for Multiple-Choice Exams* 
10. A n s w e r the quest ions you k n o w first. Mark i tems where you get stuck. C o m e 
back to harder quest ions later. Often you will find the answer you are looking for 
embedded in another, easier quest ion. 
9. First try to answer the i tem without looking at the opt ions . 
8. El iminate the dis tracters . Treat each alternative as a t rue-fa lse i tem. If "False ," 
el iminate it. 
7. Use c o m m o n sense . Reasoning is more reliable than memory. 
6. Underl ine key words in the s tem. This pract ice can be helpful when you are stuck. 
I t may he lp you focus on what quest ion is really being asked. 
5. If two al ternat ives look similar, it is likely that one of them is correct . 
4. Answer all quest ions . Unless points are being subtracted for wrong answers (rare), 
i t pays to guess when you ' re not sure. Research indicates that i tems with the most 
words in the midd le of the list are often the correct i tems. But be caut ious. Your 
professor m a y have read the research too! 
3. Do not change answers . Particularly when you are guessing, your f i rs t guess is 
often correct . C h a n g e answers only when you have a clear reason for doing so. 
2. If the first i tem is correct , check the last. If i t says "al l (or none) of the above," 
you obviously need to read the other alternatives carefully. Miss ing an "all of the 
above" i tem is one of the mos t c o m m o n errors on a mult iple-choice exam. It is 
easy to read carelessly w h e n you are anxious . 
1 . R E A D T H E D I R E C T I O N S B E F O R E Y O U B E G I N ! 
* For optimal exam performance, review and use the Final Exam Prep Worksheet (Appendix B). The idea is to 
organize a systematic review of material divided into short study sessions. 
5. W h i c h of the fol lowing processes produces continental growth? 
A. suturing of marg ins dur ing a continental coll ision 
B. transfer of crust dur ing subduct ion 
C. transfer of crust dur ing strike-slip faulting 
D. all the above 
6. The Wilson cycle is 
A. a mode l for the evolut ion of landscapes . 
B. the sequence of events for the differentiation of magmas . 
C. the cycle of tectonic events related to continental evolution. 
D. a h igh-per formance mounta in bike developed in the Appalachian Mounta ins . 
7. M u c h of the crust within the Cordi l lera of western North Amer i ca 
over the last 200 mill ion years . 
A. accreted C. subsided 
B. e roded D. subducted 
Hint: Refer to F igures 10.11 and 10.12. 
8. Cratonic and other cont inental interior rocks are typically 
those rocks found at active continental margins . 
A. m u c h younger than C. younger than 
B. older than D. the same age as 
Hint: Refer to F igure 10.8. 
9. Interior cont inental shields, or cratons, are traversed by ancient orogenic belts, but 
younger orogenic belts are different from ancient orogenic bel ts because 
A. their sediments have been subjected to extensive regional me tamorph i sm. 
B. the crust is m u c h thinner and cooler. 
C. they consist of hotter and thicker crust. 
D. they consist a lmost entirely of volcanic rocks . 
10. A large port ion of the Cordi l leran orogenic belt m a y consist of 
A. accreted terranes. C. ophioli te suites. 
B. hot-spot volcanism. D. an ancient craton. 
Hint: Refer to Figure 10 .11 . 
11. Orogeny is taking place today 
A. a long the east coast of Nor th Amer ica . 
B. a long the wes t coast of South Amer ica . 
C. in the center of North Amer ica . 
D. in the Canadian Shield. 
12. W h i c h of the following s ta tements about orogenic systems is N O T valid? 
A. Orogeny is initiated by rifting as extension begins to open up a new ocean basin. 
B. Orogeny is initiated by subduction and the evolution of an active convergent margin. 
C. Large vo lumes of granite are intruded during orogenies . 
D. Folding and thrusting of preexist ing rocks contr ibutes to crustal th ickening in the 
orogen. 
13. The were produced by convergent plate boundary 
processes , including collision, during the Paleozoic . 
A. Cascade Mounta ins of nor thwesternNor th Amer i ca 
B. Rocky Mounta ins of Colorado 
C. Appalachian Mounta ins along the eastern margin of Nor th A m e r i c a 
D. Cordi l lera of western North , Central , and South Amer i ca 
Hint: Refer to Figures 10.4 and 10.17. 
14. T h e Cordi l leran orogeny was initiated by format ion of 
A. a continental rift in western North Amer ica . 
B. a subduct ion zone and convergent plate boundary along the western edge of North 
Amer ica . 
C. an impact of a comet-s ize object in the Pacific Ocean adjacent to the wes tern edge 
of Nor th Amer ica . 
D. a l ine of mant le or hot spots, which causes doming and rifting th roughout western 
Nor th Amer ica . 
15. T h e western Cordi l lera of Nor th Amer i ca is topographical ly h igher than the Appalachi-
ans mainly because 
A. orogeny occurred more recently in the Cordil lera, so the crust is thicker. 
B. granite batholi ths were intruded in the Cordi l leran belt. 
C. the Appalachians eroded faster because they consist mostly of soft, sedimentary rocks. 
D. the Appalachians never reach the elevation of the Cordi l lera because coll is ions do 
not generate h igh mounta ins . 
16. Your ass ignment as a geologist is to m a p out ancient orogenic zones in wha t is now the 
stable interior of a continent. Recent epeirogenic uplift has resulted in good exposures of 
the ancient basement rocks . W h i c h of the following features would N O T be evidence 
of an ancient orogenic zone? 
A. intensely deformed sedimentary rocks 
B. lava flows and thick layers of volcanic tuff 
C. many granitic p lutons that are all about the same radiometr ic age 
D. widespread and relatively thick accumula t ions of coral-r ich l imes tone , sandstones, 
and shales 
Evolution of the Continents 1 23 
17. W h y are the Sierra Nevada Mounta ins so much higher than the cont inental surfaces 
west and east of t hem? 
A. The crust is proably thicker and/or hotter beneath the Sierra Nevada . 
B. The crust beneath the Sierra Nevada is very thin and hot. 
C. The crust beneath the Sierra Nevada is probably denser than that to the east and west. 
D. The Sierra Nevadas are most probably part of an ancient spreading center that is no 
longer active. 
18. Mounta ins are both the source and product of sediments because 
A. mos t sediments are subducted with the ocean l i thosphere and thereby contr ibute to 
subduct ion zone magmat i sm. 
B. mos t sediments shed off mounta ins end up on the margin of a cont inent and are 
eventually accreted to the edge of continental crust by orogenic processes associated 
with convergent plate margins . 
C. the melting of sediments results in mafic igneous rocks characteristic of continental crust. 
D. mos t sediments end up on the deep ocean floor where they sit for bi l l ions of years . 
19. In the context of plate tectonics, a reasonable sequence of events for an orogenic "cycle" is 
A. hot spots -> subduct ion -> rifting -»• orogeny. 
B. rifting -»• passive margin ->• subduct ion -> orogeny -» uplift. 
C. rifting -> coll ision ->• subsidence ->• erosion -+ uplift. 
D. t ransform faulting -> uplift -*• vo lcanism -• orogeny. 
Hint: Refer to Figure 10.18. 
20. The Ear th ' s oldest continental crust can be found 
A. in active orogenic zones . C. in cont inental shield regions . 
B. on the ocean floor. D. a long the margins of the cont inents . 
2 1 . The growth of cont inents occurs a t 
A. hot spots . C. rift zones . 
B. subduct ion zones . D. t ransform faults. 
22. W h e r e on Earth could you go today to find an orogenic system with strong similarities 
to the Cordil lera of North Amer ica? The study of this active orogenic system would pro-
vide you with a better understanding of the geologic history of western North Amer ica . 
A. Andes C. Appalach ians 
B. Himalayas D. East Africa Rift 
2 3 . Epei rogeny is associated with 
A. subduct ion zones where convergence causes rapid vertical uplift. 
B. stable interior platforms within continents where isostatic adjustments result in grad-
ual uplift or subsidence. 
C. cont inental coll is ions where the highest mounta ins form. 
D. the Wilson cycle for the evolution of cont inents . 
Hint: Refer to Figure 10.20. 
24. Continental cratons seem relatively immune from deformation by plate tectonic processes 
because 
A. of deep , strong, mant le keels beneath them. 
B. they are always located at the center of the continent far from active plate boundaries . 
C. the cont inental crust is very strong. 
D. they are covered with sediments . 
Hint: Refer to Figure 10.24. 
25. A modern example of how crust can be transported laterally along a continental margin is the 
A. amalgamat ion of the southwestern C. Appa lach ian orogeny. 
Pacific is lands. D. San Andreas strike-slip fault. 
B . mid-Atlant ic Ridge . 
Hint: Refer to Figure 10.6. 
1 2 6 PART II C H A P T E R 11 
During Lecture 
This lecture is likely to cover a series of processes . Listen carefully and try to get the key 
inputs and outputs of each process into your notes . 
Note-Taking Tip 
Copy Figure 11.13 and paste it at the beginning of your Chapter 11 lecture notes. Refer 
to i t to help you stay oriented in geological t ime. D o n ' t get bogged down with specific 
dates of events. W h e n we are talking about a bill ion years , a difference of a few million 
years isn ' t worth worrying about. Instead, think in term of landmarks, and try to place them 
in the correct order. For example , single-celled life occurred a long t ime before mult i-
celled life. Oxygen had to be present before mult icel led life occurred. All ext inct ions are 
in the last 500 mill ion years . 
After Lecture 
Review Notes 
The perfect t ime to review your notes is r ight after lecture. The fol lowing checkl is t contains 
both general review tips and specific suggest ions for this chapter. 
Check Your Notes: Have you. . . 
• added visual mater ial? Suggest ion: Test your unders tanding of Chapte r 11 by adding 
simplified sketches of the important metabol ic processes and Ear th /organism cycles in 
this chapter. H i n t : See Figures 11.5 and 11 .11 . 
• labeled the inputs and outputs of specific processes that were d iscussed? If not , you 
need to look them up in the text. 
• indicated events in geological t ime in an order you can m a k e sense of? Refer to 
Figure 11.13. 
• created a brief big picture overview of the lecture (using a sketch or wri t ten out l ine)? 
Vital Information from Other Chapters 
After each lecture, you need to thoroughly master the concepts covered before you attend the 
subsequent lecture. The ideas of geology are like a stack of boxes . Each new idea rests on all 
ideas (boxes) stacked beneath it. 
T h e r e is a good deal of geo log ica l t i m e mate r ia l in this chap te r in the sec t ion Geologic 
Even t s in Ea r th ' s His tory. Rev iew F igu re 11.13 in the con tex t of F igu res 11 .13 , 8 .11 , and 
8.14; refer to F igu res 8.11 and 8.14 in C h a p t e r 8 , C l o c k s in R o c k s : T i m i n g the Geologic 
Reco rd . T h e s e three figures s u p p l e m e n t each other. I t i s vi tal tha t you under s t and the 
m e t h o d of r ad iomet r i c da t ing that has suppl ied the da tes for the r ibbon of t i m e (review 
Table 8.1 and the sec t ion I so top ic Da t ing M e t h o d s (pages 1 8 2 - 1 8 3 ) . For a tmosphe r i c dat-
ing and c l ima te work , different m e t h o d s are requi red . Rev iew C l o c k i n g the C l ima te Sys-
t e m on p a g e 186. Rev iew pages 1 4 - 1 6 in C h a p t e r 1 . Rev iew C h a p t e r 9 , Ear ly His tory of 
the Terres t r ia l P lane t s . Pages 1 9 4 - 1 9 5 and 2 0 3 - 2 0 4 are par t icu lar ly impor tan t . 
Geobiology: Life Interacts with the Earth 1 27 
Carefully rework your notes for this lecture with great attention to processes . For each processdiscussed, i t may be helpful to m a k e a s imple f lowchart specifying the input, the process , and 
the output. 
Process 
Input -» Output 
For cycles such as the sulfur cycle (Figure 11.11), it may help you to reduce the figure to a very 
simple version that will help you remember the essential b iosphere part of the cycle e lements . 
Decomposer microorganisms digest decaying animal/plant matter -» hydrogen 
sulfide + iron in the soil —» iron pyri te 
Be sure to add the figure number (in this case Figure 11.11) so that you can review the process 
in its entirety. 
Intensive Study Session 
Because there is a lot to learn in this chapter, be sure to set priorities for s tudying. Qui te likely, 
there is more material than you will have t ime to study in one intensive study session. We rec-
ommend that you give highest priority to activities that involve answer ing quest ions . Answer -
ing questions whi le us ing your text and lecture notes as reference material is far more effi-
cient than reading chapters or glancing over notes. As always, you have three sources from 
which to choose ques t ions . 
• Text. Work out prel iminary answers to Exercises 1, 2, 3, 5, 6, 7, and 10 at the 
end of the tex tbook chapter. Read each quest ion. Then try to answer it. Finally, 
check your answer against the text. Check your answers with your fellow stu-
dents, teaching assistant, and instructor. 
• Practice Exerc ises and Rev iew Quest ions . Learn by testing yourself on the 
processes covered in this chapter. Comple te the Review Quest ions , referring 
freely to the text and recommended figures. Practice Exercise 1 will be a great 
help in sorting out some of the most important ways the biosphere interacts with 
important geological processes. Start there. 
• Web Site S tudy Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Exam Prep 
Materials in this section are most useful during preparat ion for quizzes and exams . T h e C h a p -
ter Summary and Pract ice Exercises and Rev iew Quest ions should simplify your chapter 
review. Read the Chapter S u m m a r y to begin your session. It provides a helpful overview 
that should refresh your memory . 
Next work on the Pract ice Exercises and Rev iew Quest ions . Comple te the exercises 
and questions jus t as you would an exam, to see how well you have mastered the chapter. 
After you answer the ques t ions , score them. Finally, and most important of all, review each 
question that you missed . Identify and correct the misconcept ion(s) that resulted in your 
answering the quest ion incorrectly. 
Chapter Summary 
What is the biosphere? 
• T h e E a r t h ' s b i o s p h e r e i s the par t of our p lane t that con ta ins all its l iv ing 
o rgan i sms . I t i nc ludes all the p lan ts and a n i m a l s as we l l as w h o l e k i n g -
doms of near ly inv is ib le m i c r o o r g a n i s m s such as fungi and bac te r i a tha t 
128 PART II C H A P T E R 11 
What is metabolism and how does metabolism 
affect the Earth? 
• Organ i sms can be subdivided into producers (autotrophs) or consumers (het-
erotrophs) according to the way they obtain their food. Auto t rophs m a k e their 
own food using sources of energy and nutrients. Hetero t rophs feed directly or 
indirectly on autotrophs. 
• M e t a b o l i s m is the process that all o rgan i sms use to conver t inputs (energy 
and nutr ients) to outputs (s tored energy as ca rbohydra tes or fat and was te 
p roduc ts ) . For example , a pho tosyn the t i c p lant uses sunl ight , ca rbon d iox ide , 
and water to p roduce ca rbohydra tes and oxygen gas as a byproduc t . Refer to 
Table 11.2. 
• As their metabol ic processes operate , organisms cont inuously exchange 
energy and mat ter wi th their environment . B iochemica l cycles are pa thways 
that descr ibe this exchange or flow. Important b iochemica l cycles inc lude the 
carbon cycle (Figure 11.4 and Table 11.2), the phospha te cycle (Figure 11.5), 
and the sulfur cycle (Figure 11.11). 
How important are microbes? 
• Single-cel led organisms including bacteria, some fungi and algae, and pro to-
zoa are known as microbes . W h e r e there is water, there are mic robes . 
• Mic robes are the mos t abundant and diverse group of organisms on Earth . 
• Mic robes were the first organisms to inhabit the Earth, and all other organisms 
are descended from them. Refer to Figure 11.6. 
• Ext remophi les are microbes that live in envi ronments that wou ld kill other 
organisms. Refer to Table 11.3. 
• Mic robes play a critical role in many geologic processes , such as minera l 
precipitat ion, minera l dissolution, and the flow of important e lements through 
Ear th ' s crust. 
How did life originate, and what signs do we 
have of life on the young Earth? 
• Geoscient is ts cont inue to explore the mechan i sms for how life or iginated on 
the primit ive Earth . Laboratory exper iments , like those by Stanley Mil ler (Fig-
ure 11.14), and studies of meteori tes (Figure 11.24), the fossil record (Figure 
11.15), rock chemistry, and modern organisms (Figure 11.16) are all filling in 
pieces of this puzzle . 
• The fossil record tells us that microbes originated first on Ear th and that they 
evolved into all mult icel led organisms. We can find fossil microbes in rocks 
3.5 bil l ion years old. 
are a s t ronomica l l y m o r e n u m e r o u s than h u m a n s o r t he c rea tu res tha t m a k e 
up our v i s ib le wor ld . S o m e m i c r o o r g a n i s m l ive in the m o s t e x t r e m e env i -
r o n m e n t s on Ear th . 
• Because the b iosphere intersects with the l i thosphere, hydrosphere , and a tmos-
phere , i t can influence or even control basic geologic and cl imatic processes . 
Geobio logy is the study of the interact ion of these b iosphere organisms with 
the Earth. 
Where did the oxygen in Earth's atmosphere originate? 
• Ear th ' s a tmosphere is thought to have been oxygenated by cyanobacter ia that 
gave off oxygen gas as a byproduc t of photosynthesis . The fossils and the 
occurrences of banded iron formations and red beds in the geologic record 
provide ev idence for important mileposts in the history of interactions be tween 
life and environment . 
• An oxygen-r ich surface environment set the stage for the evolution of Eukarya , 
including all mult icel lular animals . 
What is the difference between radiation and extinction? 
• A radiat ion is the relatively rapid development of new types of organisms that 
derive from a c o m m o n ancestor. In contrast , ext inct ion occurs when groups of 
organisms are no longer able to adapt to changing environmental condi t ions 
or compete with a superior group of organisms. Refer to Figure 11 .21. 
• The Cambr ian explosion, which marks the origination of all major animal 
groups, is an example of a radiation. Refer to Figure 11.19. 
• When many groups of organisms b e c o m e extinct at the same t ime it is called 
a mass extinction. Refer to Figure 11 .21 , Ear th Issues 11 .1 , Figure 9.18, and 
Table 9.2. 
How do we search for life on other planets? 
• The presence of l iquid water over long periods of t ime (hundreds of mil l ions 
of years) is cons idered to be a prerequisi te for life. 
• On a planet too close to its star water will boil and b e c o m e a gas, wh ich can 
be lost to space over t ime. On a planet too far from its star, water will freeze 
into a solid. For every star, there is a habi table zone, marked by the distance 
away from the star to the point where water is stable as a liquid. If a planet is 
within the habi table zone , there is a chance that life might have originated 
there. Refer to F igure 11.25. 
Geobiology: Life Interacts with the Earth 1 29 
Figure 11 .25. S tars have habi table zones where life on an orb i t ing planet cou ld exist i f thetemperature were not 
too warm (too c lose to the star) or too co ld ( too far away from the s tar ) . T h e width of the zone is the d is tance 
over which water won ' t boil away or freeze. 
1 3 0 PART II C H A P T E R 11 
Extinction is a difficult concept to grasp. It is an eternal concept. It's not 
at all like the killing of individual life forms that can be renewed through 
normal processes of reproduction. Nor is it simply diminishing numbers. 
Nor is it damage that can somehow be remedied or for which some 
substitute can be found. Nor is it something that simply affects our own 
generation. Nor is it something that could be remedied by some super-
natural power. It is rather an absolute and final act for which there is no 
remedy on earth or in heaven. A species once extinct is gone forever. 
— T H O M A S BERRY 
Practice Exercise 
The answer and an explanat ion are provided at the end of the Study Guide . 
Exercise: How organisms and the Earth interact 
Life processes influence weather ing, precipitate minerals , and modify the composition of the 
a t m o s p h e r e and oceans . R e v i e w s o m e w a y s life p roces ses affect the Ear th by filling in 
the table. 
Life's impact Life process(es) Description of the 
on Earth generating the impact interaction and impact 
0 2 i n Ear th ' s 
a tmosphere 
Greenhouse Extraction of carbon from 
effect: Cool ing oceans and atmosphere by 
shell-producing and 
photo synthetic organisms 
Greenhouse Respiration and metabolism 
effect: of anaerobic microbes Refer to 
Warming Table 11.2 and page 246 
in textbook. 
Minera l 
precipi tat ion 
Minera l 
dissolut ion 
"Sulfate-eating " microbes Hydrogen, hydrogen sulfide, and 
methane gases may be produced. 
Geobiology: Life Interacts with the Earth 131 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. Autot rophs are organisms that 
A. m a k e their own food. 
B. get food by feeding directly or indirectly on producers . 
C. are multicellular. 
D. live only in anaerobic (oxygen-free) envi ronments . 
2. Living cells are composed primari ly of the e lements 
A. carbon, hydrogen , oxygen, and nitrogen. 
B. silicon, oxygen , hydrogen, and iron. 
C. carbon, phosphorous , iron, and calc ium. 
D. silicon, ni t rogen, iron, and magnes ium. 
3. Photosynthesis is a metabol ic process that 
A. releases energy, C 0 2 , and water. 
B. stores energy, releases water, and precipitates ca lc ium carbonate . 
C. stores energy as carbohydrates (sugars) and uses C 0 2 , and water. 
D. burns oxygen to create energy and releases water and C 0 2 . 
4. Eukaryot ic cells are 
A. very s imple cells wi thout nuclei . 
B. cells with a more compl ica ted internal structure, including a nucleus. 
C. the earliest life form to appear in the fossil record. 
D. photosynthes iz ing. 
5. The earliest record of eukaryotes occurred during the 
A. Phanerozoic . 
B. Proterozoic . 
C. Late Archean . 
D. Early Archean . 
H i n t : Refer to Figures 8.14 and 11.6, and the section Chemofoss i ls and Eukaryotes in 
Chapter 11 . 
6. Deposit ion of sedimentary banded iron formations correlates with the appearance of 
A. iron-rich basal t ic lavas. 
B. animal life. 
C. coal swamps . 
D. abundant s tromatol i tes . 
H i n t : Refer to the textbook sections Microbia l Mats , Stromatol i tes , and Origin of 
Earth 's Oxygena ted Atmosphere . 
7. Banded iron format ions (BIFs) are 
A. abundant in the Phanerozoic . 
B. precipitated by reacting with ni t rogen. 
C. rare in the Archean . 
D. precipitated by react ing with oxygen. 
8. Stromatolites represent sedimentary structures constructed by 
A. single-celled algae (cyanobacter ia) . 
B. horn corals . 
C. snails. 
D. burrowing tr i lobites. 
9. Extremophi les are microbes that 
A. have a s trong preference for oxygen-r ich environments . 
B. are exclusively Eukaryotes . 
C. precipitate abundant ca lc ium carbonate . 
D. live in envi ronments with h igh salinity, acidity, temperature , or no oxygen. 
10. Living things are able to grow and 
A. eat food. 
B . reproduce. 
C. calculate. 
D. precipitate. 
11 . W h a t do the Murchison meteori te and the Mil ler exper iment have in c o m m o n ? 
A. Both were exposed to ni t rogen gas, a byproduc t of life processes . 
B. Both contained abundant amounts of water. 
C. Both provide evidence for an a tmosphere r ich in oxygen on the primitive Earth. 
D. A m i n o acids, the fundamental building blocks of proteins , are abundant in the mete-
orite and the products produced by the Mil ler exper iment . 
Figure 11.14. This simple experiment design was used to convert ammo-
nia (NH 3 ) , hydrogen ( H 2 ) , water vapor ( H 2 0 ) , and small carbon-bearing 
molecules such as methane ( C H 4 ) into amino acids—a key component of 
living organisms. 
12. The Cambr ian Explos ion is 
A. the greatest mass extinction event in Earth history. 
B. a surprising rapid radiat ion of every major animal g roup . 
C. the first appearance of life on Earth. 
D. the rapid radiat ion of s tromatoli tes across the Ear th ' s surface. 
13. As a planetary scientist s tudying potential ly habi table planets outside our solar system, 
you would get very excited about finding evidence for 
A. a planetary a tmosphere rich in ni t rogen and a m m o n i a gases . 
B. abundant oxygen gas and traces of me thane in a p lanet ' s a tmosphere plus water ice 
on the surface. 
C. an a tmosphere rich in hydrogen and hydrogen sulfide gas . 
D. a surface covered with lava flows and few impact craters. 
1 3 2 PART II C H A P T E R 11 
CHAPTER 12 
Volcanoes 
136 PART II C H A P T E R 12 
Motivation Tip 
Chapter 12 contains material that should be of cons iderable interest to anyone living or 
p lanning to live in the nor thwestern Uni ted States. There is information in this chapter 
that could literally save your life. Also il lustrated are landforms in Hawai i and some of 
our western national parks , for example , M o u n t Rainier, Crater Lake , and Yellowstone. 
Qui te possibly you have visited one of these places and wondered at its beauty. 
Give yourself permission to enjoy this particularly interesting chapter! Begin your 
study session by jus t browsing the artwork in Chapter 12 for ideas that interest you. Start 
reading wherever your interest takes you. Give yourself fifteen or twenty minutes just to 
enjoy the interesting illustrations before you plunge into studying text and doing exercises 
Exam Prep 
Mater ia ls in this section are mos t useful dur ing prepara t ion for quizzes and exams . The 
Chapter S u m m a r y and the Pract ice Exercises and Rev iew Ques t ions should simplify your 
chapter review. Read the Chapter S u m m a r y to begin your session. I t provides a helpful 
overview that should refresh your memory . 
Next work on the Pract ice Exercises and Rev iew Quest ions . Comple t e the exercises 
and quest ions jus t as you would an exam, to see h o w well you have mas te red this chapter. 
After you answer the quest ions , score them. Finally, and mos t impor tant of all, review each 
quest ion that you missed. Identify and correct the misconcept ion(s) that caused you to answer 
the quest ion incorrectly. 
Chapter Summary 
Why does volcanism occur? 
• Volcanism occurs w h e n mol ten rock inside the Earth rises buoyant ly to the 
surface because it is less dense than the surrounding rock. Volcanism is a sur-
face expression of m a g m a generat ion within the Earth . 
Intensive Study Session 
Ready to work? Set priorities for s tudying this chapter. 
• P r a c t i c e Exercises and Rev iew Quest ions . Be sure to do Exerc ise 1 . I t 
involves the key information you need to learn in this chapter. 
• Text. Pay part icular at tention to Figures 12 .1 , 12.11 , 12.12, 12.20, 12.23, and 
12.25. These figures present the mos t important ideas in Chapte r 12. A n s w e r 
Exercises 1 and 5 and Though t Quest ion 1 at the end of the chapter. 
• W e b Site S tudy Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Do the Onl ine Rev iew Exercises W h e r e Do Volcanoes Occur? and Finding 
the Volcanic Hot Spots . 
What are the three major lava types and how do 
they relate to eruptive style and volcanic landforms? 
• Silicate lavas can be classified in three major types—fels ic (rhyolite), inter-
media te (andesi te) , and mafic (basal t )—based on decreasing amoun t of silica 
and increasing amounts of iron and magnes ium. 
• Eruption styles, volcanic deposits, landforms, and potential hazards are strongly 
l inked to the chemica l composi t ion and gas content of the lava (refer to Exer-
cise 1). Because basal t ic lavas are relatively fluid and dry, they typically 
exhibit less explosive erupt ions and erupt as lava flows. Rhyol i te lavas are very 
viscous and usual ly wet . Therefore , they typically erupt very explosively as 
pyroclast ic flows or form domes . 
How is volcanism related to plate tectonics? 
• There is a s trong connect ion be tween major types of volcanism and crustal 
plate boundar ies . Basal t ic lavas occur at divergent plate boundar ies and hot 
spots. T h e ocean crust is created by basalt ic volcanism at the ocean r idge sys-
tem. Basal t is thought to be generated by partial melt ing due to decompress ion 
of the ultramafic upper mant le . Basal t ic , andesit ic , and rhyolitic lavas erupt at 
convergent zones due to f luid-induced mel t ing. The lavas generated along any 
particular convergent zone depend in large part on what type of rocks are being 
subducted and mel ted within the overriding crust. 
How does volcanism interact with human affairs? 
• There are bo th benefits and hazards associated with volcanism. Geothermal 
heat is growing in impor tance for electric energy generat ion. Ear th ' s oceans 
and a tmosphere are thought to have condensed from volcanic degass ing of our 
planet ' s interior. Volcanic dust and gases can impact global c l imate . Volcanic 
eruptions and associated mudf lows can have disastrous impacts on a region 
and its people . Impor tant ore-forming processes occur when hot water circu-
lates through the m a g m a chamber and surrounding rock. 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Lava types—their properties, eruption styles, deposits, 
landforms, association with plate tectonics, and hazards 
Fill in the b lanks wi th the typical character is t ics of each lava type . Keep in mind that differ-
ent lavas exhibi t a range of proper t ies and behaviors . Give the best answer that general ly 
characterizes each lava. S o m e answers have been provided as guidel ines . Bullets mark 
spaces to fill in. 
This table wil l provide you with a very useful study guide for much of Chapte r 12. It 
makes an ideal summary of the chapter that should be very useful when you return to this 
chapter in preparat ion for your mid te rm exam. 
Volcanoes 1 3 7 
1 38 PART II C H A P T E R 12 
Lava types 
Characteristics Basalt (mafic) Andesite (intermediate) Rhyolite (felsic) 
Proper t ies 
erupt ion tempera ture 
silica content 
gas content 
viscosity 
typical flow velocity 
typical flow length 
typical flow thickness 
• 
• 
low, up to a few percent 
low-fluid magma 
0.7 to 30 m/minute 
10 to 160 km 
5 to 15 m 
intermediate 
intermediate 
variable 
intermediate 
9 m/day 
8 km 
30 m 
• 
high (~ 70%) 
high (up to*> 15%) 
• 
less than 9 m/day 
less than 1.5 km 
200 m 
Erupt ion styles typically not very explosive • • 
Deposi t s flood basalt lava flow 
dome 
pyroclastic flow— 
tuff and welded tuff 
obsidian dome 
• 
• 
Landforms 
cinder cone 
small caldera 
composite volcano 
summit crater 
caldera 
cinder cone 
• 
• 
• 
Associa t ion with 
plate tectonics 
hot spots 
• 
• • 
Hazards • 
• 
lava flow 
pyroclastic/ash flow 
explosive blast 
hot gases 
mudflow 
explosive blast 
hot gases 
• 
• 
The longest word in the English language is supposedly 
pneumonoul tramicroscopics i l i covo lcanoconios—a lung disease caused by breathing in 
particles of volcanic matter or a similar fine dust. 
Exercise 2: Volcanoes at plate tectonic boundaries 
Comple te this exercise by filling in the b lanks adjacent to the list of volcanic areas with the 
correct match of magmat ic (plate tectonic) setting and characterist ic m a g m a type. 
Use Figures 12.11, 12.12, 12.19, 12.20, and 12.26 and an atlas as a reference. Chapter 2 
and Web site links provided at ht tp: / /www.whfreeman.com/understandingearth5e will also help 
you. Sample answers are provided. Note that a volcanic area may have hybrid characteristics. 
Volcanoes 1 3 9 
Magmatic 
Volcano or 
volcanic area 
Type of volcano Magma type (plate tectonic) 
(shield, composite, (mafic, intermediate, setting—divergent, 
caldera) felsic) convergent, hot spot 
Hawaii 
Tonga Is lands 
Columbia Plateau 
Santorini (Thera) , Greece 
Mayon, Phi l ippines 
Iceland 
composite intermediate and felsic 
mafic 
convergent/'subduction 
hot spot 
caldera 
divergent and hot spot 
Yellowstone 
Krakatoa, Indones ia 
North Island, N e w Zea land 
Crater Lake , Oregon 
Japan 
Aleutian Is lands, Alaska 
Mariana Is lands 
Kilimanjaro, Africa 
Pinatubo, Phi l ippines 
Katmai, A laska composite and caldera 
Mount Rainier , Washington 
Tambora, Indones ia composite and caldera convergent 
Vesuvius, Italy 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. Lavas are a lmost a lways fine-grained rocks because 
A. the minera ls they are m a d e up of do not form large crystals . 
B. very little water is in the extruded mag ma . 
C. the lava crystal l izes under pressure too low for large crystals to grow. 
D. they cool too rapidly for large crystals to grow. 
2. W h i c h extrusive rocks contain the mos t silica? 
A. andesi te 
B. rhyol i te 
C. granite 
D. basal t 
3 . Dur ing volcanic erupt ions, the mos t c o m m o n gas re leased is 
A. hydrogen . 
B. water. 
C. ni t rogen. 
D. carbon dioxide. 
4. A cloud of superheated s team and hot ash that is p roduced dur ing a volcanic eruption 
and moves rapidly parallel to the ground is called 
5. A good example of shield volcanoes can be found in 
A. northern California, Washington, and Oregon. 
B. the Hawai ian islands. 
C. the Car ibbean islands, such as Mt. Pelee on Mar t in ique . 
D. western South Amer ica . 
6. Compos i t e volcanoes (stratovolcanoes) are composed largely of 
A. basal t lava flows and basalt ic c inders . 
B. pi l low and pahoehoe lava flows. 
C. rhyolitic and intermediate lavas and pyroclast ic flows. 
D. dikes and sills. 
7. Compared to basalt , rhyoli te lava flows are very thick and tend to form domes because 
rhyoli te lava 
A. contains less gas than basalt lava and is therefore more fluid. 
B. is r icher in silica than basalt lava and is therefore less fluid. 
C. cools more quickly than basalt lava. 
D. is less dense than basalt lava. 
8. On a recent three-day hike up a gently sloping mounta in , your friends describe to you 
features they encountered. Frequent ly they crossed lava flows and fissures, and occa-
sionally they had to detour around large cinder cones . F r o m your fr iends ' description, 
you tell t hem they were hiking on a 
A. caldera. C. gabbro pluton. 
B. composi te volcano. D. shield volcano. 
9 . Compos i te volcanoes are c o m m o n l y associated with which tectonicsett ing? 
A. passive continental margins and deep ocean basins 
B. convergent plate boundar ies , such as those of the circum-Pacif ic 
C. ocean spreading centers , such as Iceland 
D. transfer faults, such as the San Andreas fault 
10. Of the following states, which is essentially all volcanic rock? 
A. Alaska C. Oregon 
B. Hawai i D . California 
11 . Typically, explosive volcanic erupt ions are associated wi th 
A. basal t lavas. 
B. shield volcanoes . 
C. m a g m a s that are poor in both silica and dissolved gases . 
D. m a g m a s that are h igh in both silica and dissolved gases . 
12. Shield volcanoes and compos i te volcanoes differ in shape because of 
A. the different composi t ions of their magma . 
B. the part icular part of the ocean that each one forms in. 
C. the lati tude at which each one forms. 
D. factors that are complete ly unknown to us at present. 
H i n t : Refer to Figure 12 .11. 
A. a welded tuff. 
B. a pyroclast ic flow. 
C. volcanic b o m b s . 
D. a cinder flow. 
1 4 0 PART II C H A P T E R 12 
13. Calderas usually form 
A. from mol ten mater ial from the core that comes very near the Ear th ' s surface at a thin 
point in the crust. 
B. after a s team explosion, w h e n m a g m a comes into contact with abundant under-
ground water. 
C. w h e n an eruption literally b lows the top of a volcano off. 
D. after large vo lumes of m a g m a erupt, leaving a void in the m a g m a chamber into 
which the superstructure of a volcano can col lapse. 
H i n t : Refer to F igure 12.12. 
14. Your fr iends have descr ibed to you an e rup t ion that took p lace at an und i sc losed loca-
t ion. T h e lava they descr ibed mere ly f lowed out of a fissure and spread rap id ly over 
a large area. You wou ld in form your fr iends that the rock type be ing formed wou ld be 
m o s t l ikely to be 
A. grani te . C. basalt . 
B. andesi te . D. rhyoli te . 
15. You have been informed that an explosive volcanic erupt ion has taken place at an undis -
c losed locat ion and that a huge nuee ardente (pyroclastic flow) flowed off the s teep-
sided volcano. You could respond that the m a g m a type is l ikely to be 
A. basal t ic . C. ultramafic. 
B. rhyoli t ic . D. gabbroic . 
16. W h e r e are andesi t ic volcanoes located? 
A. whe re diverging plate boundar ies occur 
B. a t t ransform boundar ies 
C. a long the mid-ocean ic r idge crest 
D. a long converging plate boundar ies 
Volcanoes 141 
1 42 PART II C H A P T E R 12 
17. A large resort located on a beautiful lake and known for its hot springs is experiencing 
a drop in business due to publici ty about the recent swarm of small ear thquakes in the 
area. The lake is actually located within a caldera, and beautiful rock towers and spires 
of weathered volcanic tuff are found all a long the edge of the lake. As the director of 
the resort, you ' re concerned about the change in bus iness and the potential risk to your 
guests . W h a t should you do? 
A. You cannot be worr ied because you know a volcano can ' t b low up on you. 
B. You know that ear thquake swarms can be a precursor to volcanic erupt ions and that 
very explosive eruptions have happened at the p lace in the recent geologic past, so 
you decide that the resort should close until the situation is safe. 
C. Adver t ise the resort as the best place to see beautiful basalt lava fountains. 
D. Ear thquakes have occurred occasionally along a nearby known fault, and there have 
been no historic volcanic erupt ions, so you ' r e not concerned. 
18. W h i c h type of lava is mos t likely to erupt at the mid-ocean r idge? Refer to Figure 12.20. 
A. basalt C. rhyoli te 
B. andesi te D. diorite 
19. W h i c h type of lava is most likely to erupt at a hot spot? Refer to F igure 12.20. 
A. basal t C. rhyoli te 
B. andesi te D. diorite. 
20 . W h i c h type of lava is most likely to erupt at a convergent boundary along the edge of a 
cont inental plate, as shown in F igure 12.20? 
A. basal t C. rhyoli te 
B. andesi te D. diorite 
2 1 . W h i c h of the fol lowing volcanic deposi ts can be formed from felsic lava? 
A. pahoehoe C. volcanic d o m e 
B. f lood basal t D. shield volcano 
22. If lava flows of progressively younger ages all erupted from a single large m a g m a cham-
ber, h o w would you expect their composi t ion to have progressively changed? 
A. enr iched in iron as they get younger 
B. enr iched in silica as they get younger 
C. more mafic as they get younger 
D. more fluid as they get younger 
23. W h i c h of the fol lowing s ta tements about mafic rocks is t rue? 
A. Mafic rocks are r icher in silica than felsic rocks . 
B. Mafic rocks crystal l ize at h igher temperatures than felsic rocks . 
C. Mafic rocks are more viscous than felsic rocks . 
D. Mafic rocks tend to be l ighter in color than felsic rocks . 
24. Large volcanoes can potential ly affect global c l imate w h e n they erupt because they 
release 
A. geo thermal heat . 
B. volcanic dust , sulfur, and carbon dioxide gas . 
C. lahars and lava flows. 
D. ni t rogen and argon gases . 
Volcanoes 1 4 3 
CHAPTER 13 
Earthquakes 
Figure 13.12. Earthquakes indicate how tectonic plates interact at their boundaries. 
144 
Before Lecture 
Before you at tend lecture, be sure to spend some t ime previewing the chapter with the fol-
lowing ques t ions . 
Chapter Preview 
• W h a t is an ear thquake? 
Brief answer : an ear thquake is a shaking of the ground caused by seismic waves that 
radiate out from a fault that moves suddenly. Elastic rebound explains why 
ear thquakes occur. Refer to Figure 13.1. 
• W h a t are the three types of se ismic waves? 
Brief answer: P (pr imary/compress ional ) waves , S (secondary/shear) waves , and 
surface waves . Refer to Figure 13.5. 
• W h a t is e a r t h q u a k e m a g n i t u d e and h o w is i t m e a s u r e d ? 
Brief answer : Ear thquake magn i tude is a measure of the size of the ear thquake. 
The Richter magni tude is determined from the ampl i tude of the ground motion. 
The momen t magni tude is closely related to the amoun t of energy radiated by the 
ear thquake. The Mercall i Intensity Scale is a more qualitative measure of the 
d a m a g e done by an ear thquake. 
• W h e r e do m o s t ear thquakes occur? 
Brief answer: Mos t but not all earthquakes occur along active plate tectonic boundaries . 
Refer to F igure 13.12. 
Vital Information from Other Chapters 
A careful review of Chapte r 7, Deformat ion: Modificat ion of Rocks by Folding and Fractur-
ing, will provide you with important prerequisi te information. Chapte r 7 emphas izes brittle 
and plastic styles of rock deformation. Ear thquakes are thought to be the result of the elastic 
behavior of solid rocks , ana logous to the snap-back from a rubber band when it breaks . In par-
ticular, review pages 1 5 4 - 1 6 3 and Figure 7.7. 
Earthquakes 1 4 5 
1 46 PART I I C H A P T E R 13 
Web Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Tectonic Forces in Rock Deformation for Chapter 7 and Create an Earthquake for Chapter 13 
are O n l i n e Review Exerc i ses worth complet ing before the first lecture on earthquakes. 
One goal for lecture should be to leave the r o o m with good answers to the preview questions. 
• To avoid gett ing lost in details, keep the big picture in mind . Chapter 13 tells 
the story of ear thquakes: how ear thquake activity is measured , the seismic 
waves that are generated by ear thquakes , and how ear thquake activity is driven 
by plate tec tonics—the location and characterist ics of ear thquakes is greatly 
influenced by the type of plate boundary. 
• Focus on unders tanding the differences be tween the three kinds of seismic (P, 
S, surface) waves . 
Note-Taking Tip: Mark possibletest items 
As the end of semester approaches , your instructor may ment ion that certain material 
will be covered in the end-of-semester exam. It will be helpful to have a systematic way 
of mark ing such material so that you w o n ' t miss i t when you are s tudying your notes for 
the final. You could tag the material with a s tandard abbreviat ion l ike TQ (test quest ion) . 
I t will obviously save t ime if your TQ mark is very visible. M a r k i t in dark, large print 
and put i t out in the margin where your eye will easily spot i t dur ing review. Format t ing 
t ip: If you have adopted the strategy of leaving a co lumn or the entire left page of your 
no tebook blank for insert ing visual material and special notes to yourself, put TQ tags in 
the b lank column. See the fol lowing example . 
Example of How to Mark Your Notes for Possible Test Items 
Blank column or page for 
visual material, T Q , and other 
additions to your notes Your notes 
During Lecture 
W h a t is an ear thquake? 
T Q 
( F S 13.5) 
F i n a l M a y 10! 
ground shakes 
Seismic wave from a moving fault -*• Ground shakes 
W h a t are the three types of seismic waves? 
P (pr imary) wave 
S (secondary) wave 
surface waves 
Earthquakes 1 4 7 
Intensive Study Session 
Set priori t ies for s tudying this chapter . Give h ighes t pr ior i ty to act ivi t ies that involve 
answering ques t ions . We r e c o m m e n d the fo l lowing strategy for learning this chapter . 
• W h a t is an ear thquake? W h a t causes ear thquakes to occur? Be sure you 
have clear, accurate answers to these quest ions in mind before moving on to 
other mater ial . I t will be m u c h more difficult to unders tand the discussions of 
seismic waves and other ear thquake phenomena that are the major focus of 
Chapter 13 if you are at all fuzzy about ear thquake basics . 
• Test yourself. Comple te Pract ice Exercise 1, Ear thquake focus versus epicen-
ter, and try to answer Review Quest ions 1, 2, 9, and 13 wi thout looking at the 
answers . Then check your answers . Finally, and mos t important , explore the 
text mater ia l suggested for any quest ions you missed or any areas where you 
feel unclear about the concepts . 
• Text. Preview the key figures in the text: Figure 13.1 (elastic rebound theory 
explains ear thquake) , Figure 13.5 (seismic waves) , and Figure 13.6 (determin-
ing the epicenter of an ear thquake) . You have to unders tand these figures to 
comple te the Pract ice Exerc ises and answer the Rev iew Quest ions . S o m e -
t ime before the exam, answer all seven of the exercise quest ions at the end of 
Chapter 13 in the text. These are shor t -answer quest ions and w o n ' t take long 
if you know the mater ial . 
• Pract ice Exerc ises and Rev iew Quest ions . You will get the greatest return on 
your s tudy t ime by work ing on Pract ice Exercises 1 and 2 because they will 
he lp you r e m e m b e r the m o s t impor tan t ideas in the chapter . T h e n try 
After Lecture 
Review Notes 
The perfect t ime to review your notes is r ight after lecture. The following checklist contains 
both general review tips and specific suggest ions for this chapter. 
Check Your Notes: Have you. . . 
• identified the impor tant points clearly? Hint: You should have headers in your notes 
for each of the ques t ions in the Chapter Preview. 
• filled in points that you d idn ' t have t ime to record during lecture? 
C marked possible test quest ions (TQ) in the margin? 
• indicated important figures to study later? 
• added visual mater ia l? Key visual mater ial for Chapter 13 includes Figure Story 13 .1 , 
Elastic Rebound Theory of an Ear thquake , Figure Story 13.5, Seismic Waves, and the 
figure you will deve lop in Pract ice Exercise 1 at the end of this Study Guide chapter. 
You can sketch s imple vers ions of any aspect of these figures that will help you 
r emember the ideas. 
• made a compar i son chart to help you review key ideas? Suggest ion; Comple te 
Practice Exercise 2, Character is t ics of Seismic Waves. Add a copy of this exercise to 
your notes . I t will be extremely useful for reviewing before an exam. 
1 48 PART II C H A P T E R 13 
Exam Prep 
Mater ia ls in this section are mos t useful dur ing preparat ion for quizzes and exams . The Chap-
ter S u m m a r y and the Pract ice Exercises and Review Quest ions should simplify your chapter 
review. Read the Chapter Summary to begin your session. It provides a helpful overview that 
should refresh your memory . 
Next, work on the Pract ice Exercises and Review Quest ions . To determine how well you 
have mastered this chapter, complete the exercises and quest ions jus t as you would a midterm. 
After you answer the quest ions, score them. Finally, review any quest ion you missed. Identify 
and correct the misconcept ion(s) that resulted in your answering the quest ion incorrectly. 
In times of change, learners inherit the earth, while the 
learned find themselves beautifully equipped to deal 
with a world that no longer exists. 
— E R I C HOFFER 
Chapter Summary 
What is an earthquake? 
• An ear thquake is a shaking of the ground caused by seismic waves that 
emanate from a fault that moves suddenly. W h e n the fault moves , the strain 
built up over years of slow deformation by tectonic forces is re leased in a few 
minutes as seismic waves. 
• Elastic rebound theory explains why ear thquakes occur. Over a per iod of t ime, 
the application of stress causes rock to slowly deform (bend) elastically unti l 
i t breaks , and the rock snaps back as the fault moves . This stretching and 
breaking is analogous to stretching a rubber band until i t b reaks and snaps 
back to sting your hand. 
What determines the depth of an earthquake? 
• The focus is a point a long the fault at which the ear thquake initiates. 
• Ear thquakes occur only in brittle rock, which can break and snap back elasti-
cally. At high temperatures and confining pressures found at greater depths , 
rocks are ducti le and do not break to generate ear thquakes . 
answer ing each of the review quest ions to check your unders tanding of the 
lecture. Check your answers as you go, but try to answer the quest ion before 
you look at the answer. 
• W e b Site Study Resources 
http ://w w w. whfreeman.com/unders tandingear th5 e 
C o m p l e t e the C o n c e p t R e v i e w and W e b R e v i e w Q u e s t i o n s . Pay par t icu la r 
a t tent ion to the exp lana t ions for the answer s . F l a s h c a r d s wil l he lp you 
learn new terms. The Onl ine Review Exercises Identify the Factors Contribut-
ing to Earthquakes at Plate Boundaries and Identify Factors Contributing 
to Earthquakes at Convergent Plate Boundaries a re in terac t ive exerc i ses 
wor th do ing . A l so , c o m p l e t e the G e o l o g y in Prac t i ce exerc i ses to learn 
m o r e abou t ea r thquakes . 
• Ear thquakes occur within cold, brit t le subduct ing oceanic l i thosphere to a 
depth of about 700 k m . Below this depth, the rock is too hot and soft to break. 
Where do most earthquakes occur? 
• Mos t but not all ea r thquakes occur a long crust plate boundar ies . Ear thquakes 
at d ivergent p la te boundar ies are usual ly shallow, have lower magni tude , and 
are a consequence of tensional stress. Convergent p la te boundar ies p roduce 
shal low and deep ear thquakes of low to h igh magni tudes and are c o m m o n l y 
caused by compress ive stress. Transform faults p roduce shal low to moder -
ately deep ear thquakes of low to h igh magn i tude , usual ly in response to shear 
stress. Refer to F igure 13.12. 
What governs the type of faulting that occurs in an earthquake? 
• The stress applied to the l i thosphere is largely determined by the type of plate 
boundary. Tensional , compress ional , and shear stressesde termine the type of 
fault. Refer to Figure 13.10. 
What is earthquake magnitude and how is it measured? 
• Ear thquake magn i tude is a measure of the size of the ear thquake. The Richter 
magn i tude is de te rmined from the ampl i tude of the ground motion. The move-
ment magn i tude is closely related to the amoun t of energy radiated by the 
ear thquake . T h e modified Mercal l i intensity scale is a quali tat ive measure of 
the d a m a g e done by an ear thquake. 
What are the three types of seismic waves? 
• There are three major types of seismic waves (Figure 13.5). Two types of waves 
travel through the Ear th 's interior: P (primary/compressional) waves, which 
move through all forms of matter and move the fastest, and S (secondary/shear 
waves) waves, which move through solids only and at about half the speed of P 
waves. The third type, surface waves, need a free surface like the Ear th 's surface 
to ripple across, like waves on the ocean. They move more slowly than the inte-
rior waves but cause most of the destruction associated with earthquakes. 
Earthquakes 14 9 
What causes the destructiveness of earthquakes? 
• The destruct iveness of an ear thquake does not depend on its magni tude alone. 
In addit ion to ground mot ion, the durat ion of the ear thquake, avalanches , fires, 
l iquefaction, t sunamis , proximity to populat ion centers , and the construct ion 
design of bui ldings can all amplify the destruct iveness of an ear thquake. Refer 
to Earth Issues 13.1 . 
What can be done to mitigate the damage of earthquakes? 
• T h e damage caused by ear thquakes can be mit igated by regulat ing the con-
struction design of bui ldings in ear thquake zones ; bol t ing houses to their foun-
dation; securing appl iances and tall furniture to walls and keeping heavy i tems 
at low levels; and having a communi ty plan for deal ing with emergencies gen-
erated by ear thquakes . Geologis ts generate seismic risk maps to aid public 
authori t ies with their evaluations. Refer to Earth Issues 13.2. 
Can scientists predict earthquakes? 
• Scientists can character ize the degree of risk in a region, but they cannot con-
sistently predict ear thquakes . 
Practice Exercises 
Answers and explanat ions are provided at the end of this Study Guide . 
Exercise 1: Earthquake focus versus epicenter 
Label the d iagram by filling in the b lanks with the following terms: fault scarp, earthquake 
focus, fault zone, earthquake epicenter. Use arrows to show the relative mot ion a long the fault 
zone . The star marks the location from which fault movemen t propagated . 
W h a t type of fault is this? 
1 5 0 PART II C H A P T E R 13 
Exercise 2: Characteristics of seismic waves 
Complete the table be low by filling in the b lank boxes . Figure 13.5 and the Seismic Waves 
section of the tex tbook will be helpful. 
Characteristic P (primary) waves S (secondary) waves Surface waves 
Relative speed second fastest 
Motion of mater ia l through rolling/elliptical and 
which wave propagates sideways motions 
Medium through which wave confined to the Earth's 
will propagate surface 
Analogy with c o m m o n S wave propagation is 
wave forms difficult to visualize. It is 
somewhat analogous to the 
way cards in a deck of playing 
cards slide over each other 
as you shuffle the deck. 
Earthquakes 151 
152 PART II C H A P T E R 13 
It often happens that the wave flees the place of its 
creation, while the water does not; like the waves made 
in a field of grain by the wind, where we see the waves 
running across the field, while the grain remains in place. 
— L E O N A R D O D E VINCI 
Exercise 3: Factors that amplify the damage caused by an earthquake 
1. 
2. 
3 . 
4 . 
5. 
Review Questions 
Answers and explanat ions are provided at the end of this Study Guide . 
1. Elast ic rebound theory says that ear thquakes are produced w h e n 
A. rocks deform plastically along a fault to produce anticl ines and syncl ines . 
B. rocks abruptly slip past each other after an extended per iod dur ing which elastic 
deformation is built up in the rocks . 
C. m a g m a within the Earth abruptly begins to flow and elastically deforms the sur-
rounding rocks . 
D. abrupt m o v e m e n t along faults are caused by tidal forces. 
2. The actual rupture point within the crust that results in an ear thquake is called the 
A. t sunami . 
B. focus. 
C. epicenter. 
D. static release. 
3. The order of arrival of seismic waves at a recording station is 
A. P waves , S waves , surface waves . 
B. S waves , surface waves , P waves . 
C. P waves , surface waves , S waves . 
D . s imul taneous . 
4. To locate an ear thquake epicenter, a m i n i m u m of seismic stations is required. 
A. one 
B . two 
C. three 
D. be tween f ive and twelve , depending on the location of the ear thquake 
H i n t : Refer to F igure 13.6. 
Earthquakes 153 
5. The Richter scale for ear thquake magni tude measures the 
A. d a m a g e caused by the ear thquake. 
B. amoun t of energy released by the ear thquake. 
C. amoun t of g round mot ion. 
D. durat ion of the ear thquake. 
6. The ground mot ion generated by a Richter magni tude 8 ear thquake is a factor of 
t imes greater than a Richter 4 ear thquake. 
A. 2 
B. 100 
C. 1000 
D. 10,000 
7. Pr imary seismic waves (P waves) , like sound waves , 
A. travel only through solid mater ial . 
B. travel only through l iquids and gas . 
C. travel through solid, l iquid, and gas . 
D. are the s lowest seismic waves . 
8. Secondary seismic waves (S waves) 
A. travel parallel to P waves (parallel waves) . 
B. travel only through solid mater ial . 
C. travel through solid, l iquid, and gas . 
D. are the fastest seismic waves . 
9. A significant finding that supports the theory of plate tectonics is that most ear thquakes 
occur 
A. r andomly in the midd le of tectonic plates. 
B. at all active tectonic plate boundar ies . 
C. only at tectonic plate boundar ies that move toward each other. 
D. only at tectonic plate boundar ies that slide past each other. 
10. You jus t started a j o b as a county p lanner in Colorado when the Board of Supervisors 
manda tes ear thquake risk assessment . Your first task is to assess the potent ial for a 
major se ismic event in an area that has exper ienced only a few minor ear thquakes . You 
decide to 
A. install a state-of-the-art seismic recording station to moni tor ear thquake activity. 
B. develop a se ismic risk m a p showing the l ikel ihood of an ear thquake based on the 
number that have occurred in the past. 
C. develop an ear thquake protect ion plan with local and state officials. 
D. invest igate the records for t sunamis . 
11. Given four structures all built identically, the one built on would sustain 
the M O S T d a m a g e dur ing an ear thquake when all four are located the same dis tance 
from its epicenter. 
A. a hil lside c o m p o s e d of unfractured granite 
B. a quar tz -cemented sandstone formation 
C. solid unfractured granite bedrock 
D. a water-saturated s t ream delta 
H i n t : Refer to the section How Ear thquakes Cause Their D a m a g e in your textbook. 
12. Your seismograph has jus t recorded an earthquake. You are curious whether the earth-
quake occurred in North Amer ica or somewhere else in the world. Given the arrival t ime 
of 5 minutes for the first P waves and 10 minutes for the first S waves, you determine that 
the approximate distance between you and the earthquake is kilometers. 
A. 100 C. 3000 
B . 1000 D . 7000 
H i n t : Use the graph in Figure 13.6 to m a k e the est imate. 
Bird's-eye view of a fault zone with the first motion data for P waves 
arriving at four seismograph stations during an earthquake. The star 
marks the epicenter. The dashed line is a north-southreference line 
plotted perpendicular to the fault (solid line). 
A. The north side moved east (right) and south side moved wes t (left). 
B. The north side moved west (left) and south side moved east (r ight) . 
C. The north side moved down and south side moved up . 
D. The north side moved up and south side moved down. 
16. W h a t type of fault p roduced the first mot ion shown in quest ion 15? 
Hint: Match the il lustrations in Figure 13.10 and 13.11 to de termine the type of fault. 
13. W h i c h of the following features does N O T character ize a divergent plate boundary? 
A. shal low-focus ear thquakes 
B. basalt erupt ions 
C. deep-focus ear thquakes 
D. a rift valley 
Hint: Refer to Figure 13.12. 
14. Which of the following states has the lowest potential for seismic hazard? 
A. Washington 
B . Utah 
C. Texas 
D. New York 
Hint: Refer to Figure 13.18. 
15. T h e first mot ions of an ear thquake as recorded at four different stations are displayed 
on the strike-slip fault shown below. Us ing this first mot ion data and Figure 13.11, 
de termine the direction of relative mot ion along the fault at the t ime of the earthquake. 
1 54 PART II C H A P T E R 13 
CHAPTER 14 
Exploring Earth's Interior 
(a) The pattern of P-wave paths through Earth's interior (b) S-wave paths through Earth's interior (solid green 
(solid blue lines). The dashed blue lines show the progress lines). The larger S-wave shadow zone extends from 
of wave fronts through the interior at 2-minute intervals. 105° to 180°. Although S waves strike the core, they 
Distances are measured in angular distance from the earthquake cannot travel through its fluid outer region and 
focus. The P-wave shadow zone extends from 105° to 142°. therefore never emerge beyond 105° from the focus. 
P waves cannot reach the surface within this zone because 
of the way they are bent when they enter and leave the core. 
Figure 14 .2 . Earth's core creates P-wave and S-wave shadows. 
-
Before Lecture 
Previewing will greatly increase your unders tanding of the lecture. For an efficient preview 
use the fol lowing quest ions . 
1 5 5 
156 PART II C H A P T E R 14 
Chapter Preview 
• W h a t do seismic waves reveal about the Earth's interior? 
Brief answer: Seismic waves reveal that the Ear th has a concentr ical ly zoned internal 
structure. The felsic crust lies on a denser ultramafic mant le composed mostly of 
peridoti te . The crust and upper mant le m a k e up the rigid l i thosphere. Beneath the 
l i thosphere lies the asthenosphere, the weak layer of the mant le across which the litho-
sphere slides in plate tectonics. T h e l iquid outer core and solid inner core are mostly 
iron. Refer to Figures 1.7 and 14.6. 
• W h a t has se ismic tomography revealed about s tructures in the mant le? 
Tomographic images show how tectonic plates vary from very thin under the 
mid-ocean r idges to very thick under continental cratons. Many features of mantle 
convect ion are also revealed. Refer to F igure 14.9. 
• H o w hot does i t get in Earth 's Interior? 
Refer to F igure 14.8. 
• W h a t does Earth ' s gravity field and isostatic rebound tell us about the interior? 
Brief answer: The observed gravity field is in agreement with the pattern of mantle 
convection inferred from seismic tomography. Measur ing the rate of post-glacial 
isostatic rebound provides information on the viscosity of the mant le and how it affects 
rates of uplift and subsidence of the buoyant l i thosphere. Refer to Ear th Issues 14.1. 
• W h a t does Earth ' s magnet ic field tell us about the fluid outer core? 
Brief answer: The Ear th ' s magnet ic f ie ld is p roduced by convect ive mot ions of 
electrically conduct ing iron-rich fluid in the outer core . 
• W h a t is pa l eomagnet i sm and what is its impor tance? 
Brief answer: The Ear th ' s magnet ic f ie ld flips back and forth over geologic t ime. 
Preserved in some rocks is a record of past changes in the orientat ion of Ear th ' s 
magnet ic f ie ld. Refer to Figure 14.15. 
Vital Information from Other Chapters 
It is very important to review the information on seismic waves presented in the text section 
Studying Earthquakes at the beginning of Chapter 13. Pay particular attention to the section Seis-
mic Waves and Figure 13.5, and be sure you unders tand the distinctions be tween P waves and 
S waves. A quick review of models for mant le convection will also be helpful. The key infor-
mat ion is covered in Figures 1.11, 2.14, and 12.23. Finally, take another look at Figure 2.10, 
which was your f irst exposure to pa leomagnet i sm in the text. 
During Lecture 
One goal for lecture should be to leave the room with good answers to the preview questions. 
• To avoid gett ing lost in details, keep the big picture in mind: Chapte r 14 tells 
the story of the interior of the Earth, its structure and composi t ion , and how 
Ear th ' s interior supplies heat energy to drive geological processes . Key points : 
• Ear th ' s interior is a concentr ical ly zoned structure. 
• Cont inents float on the mant le . 
• Mant le behaves like a v iscous fluid. 
• P and S waves reveal a liquid outer core and a solid inner core. 
• Heat transfer occurs via convection. 
• Ear th ' s magnet ic field is best unders tood as a geodynamo: Convect ive move-
ment (driven by Ear th ' s internal heat) generates an e lec t romagnet ic f ield. 
Exploring Earth's Interior 157 
• Focus on unders tanding Figures 14.2, 14.5, 14.6, and 14.8. If you have looked 
at t hem before coming to lecture, i t will be easy to follow the lecture: You can 
s imply annota te the figures with important new material provided by your 
instructor and under l ine material in the capt ions. 
Note-Taking Tip 
We all have moment s when we don ' t understand a point being made in lecture. When 
momentar i ly confused, cont inue taking notes. Hopefully, the necessary insight will 
come to you. If it does not, the notes you take will provide a clue to what you need to 
investigate further in your text or in a conversation with your instructor. 
After Lecture 
Review Notes 
Check Your Notes: Have you. . . 
• annota ted figures in the text with important material discussed by your instructor? 
Figures 14.2, 14.5, 14.6, and 14.8 are the important figures in Chapter 14. 
• added visual mater ia l? Since this chapter depends heavily on material from 
Chapters 1, 2, and 13, it may be useful to quickly sketch key ideas about P and S 
waves and mant le convection in your notes . See the Vital Information from Other 
Chapters section on Study Guide page 156 for suggested material . 
n added a brief big picture overview of this lecture in your own words? 
Intensive Study Session 
Set priorities for studying this chapter. Give highest priority to activities that involve answering 
questions. We r ecommend the following strategy for learning this chapter. 
• Text. Study figures 14 .2 ,14 .5 ,14 .6 ,14 .8 ,14 .9 ,14 .12 , and 14.15, and Earth Issues 
14.2. You have to unders tand these figures to answer the Rev iew Quest ions . 
S o m e t ime before your next e x a m comple te the text exercises a t the end of 
the chapter . These are shor t -answer quest ions and w o n ' t take long i f you 
k n o w the mater ia l . Not ice that helpful an imat ions are p rov ided on the W e b 
site for some of the chapter exercises . 
• Pract ice Exercises . Comple te Exercises 1 and 2. Working on these exercises 
will he lp you r e m e m b e r the mos t important ideas in the chapter. 
• Rev iew Quest ions . A n s w e r each of the review quest ions to check your under-
s tanding of the lecture. Check your answers as you go, but do try to answer the 
ques t ion before you look at the answer. Not ice the test taking-t ips that are 
in terspersed wi th these quest ions . They aredes igned to help you do better on 
your next exam. 
• W e b Site Study Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Co m ple t e the Concept Se l f -Checker and Onl ine Rev iew Quest ions . Pay par-
t icular at tention to the explanat ions for the answers . Did you know that 
Cleopatra adored peridot, a gemstone from the upper mantle? Check out Geology 
in Pract ice to f ind out more about "Cleopat ra ' s emera lds" (peridot) and the 
compos i t ion of the upper ultramafic mant le . F lashcards will help you review 
the new te rminology in this chapter. 
158 PART II C H A P T E R 14 
Exam Prep 
Materials in this section are most useful during preparation for exams. The Chapter Summary 
and the Pract ice Exercises and Review Quest ions should simplify your chapter review. Read 
the Chapter S u m m a r y to begin your session. It provides a helpful overview that should 
refresh your memory. 
Next , work on the Pract ice Exercises and Rev iew Quest ions . Comple te the exercises 
and questions jus t as you would for an exam, to see how well you have mastered this chapter. 
After you answer the quest ions, score them. Finally, and most important , review each question 
you missed. Identify and correct the misconcept ion(s) that resul ted in your answer ing the 
quest ion incorrectly. 
Chapter Summary 
What do seismic waves reveal about the layering of Earth's 
crust and mantle? 
Figure 14.6. T h e st ructure of the mant le showing the 
S-wave veloci ty to a dep th of 9 0 0 km. C h a n g e s in veloci ty 
mark the s t rong l i thosphere, the weak as thenosphere , 
and two zones in which changes occu r because increasing 
pressure forces a rearrangement of the a toms into denser 
and more c o m p a c t crystal l ine s t ructures. 
Seismic waves reveal that the Ear th has a concentr i -
cally zoned internal structure. Felsic cont inental and 
mafic ocean crusts lie on a denser ultramafic mant le 
consist ing of iron-rich silicates, like peridot i te . Refer 
to Figure 14.6. 
T h e M o h o or M o h o r o v i c i c discontinui ty in se ismic 
wave velocit ies marks the boundary be tween the crust 
and the mant le . Refer to Figures 1.7 and 14.5. 
Ear th ' s tectonic plates are large fragments of the l i tho-
sphere, which includes the crust and the uppermost , 
rigid mant le . Be low the l i thosphere in the upper 
mant le is a weak (soft) zone called the as thenosphere . 
Refer to Figure 14.6. 
Abrupt increases in seismic wave velocit ies coupled 
with laboratory studies on high-pressure minera ls sug-
gest that there are zones at progressively greater depths 
wi th in the man t l e w h e r e the crys ta l s t ruc tures of 
minera ls col lapse (change phase) under the intense 
pressure to form more compac t a tomic structures and 
therefore different minerals . 
What do seismic waves reveal about the 
layering of Earth's core? 
• P -wave and S-wave s h a d o w zones reveal a l iquid 
outer co re and a sol id inner core . Refer to F igu re 
14.2. 
• P -wave veloci t ies in the core , the na tura l abundance 
of i ron in nature , the ex is tence of i r o n - n i c k e l me te -
ori tes , the Ea r th ' s s t rong magne t i c field, and the need 
for a very dense core to accoun t for the overal l mass 
of the Ear th all suppor t an i r o n - n i c k e l compos i t i on 
for the Ea r th ' s core . 
CHAPTER 11 
Geobiology: 
Life Interacts with the Earth 
Geobiology: Life Interacts with the Earth 125 
Before Lecture 
Before you attend lecture be sure to spend some t ime previewing the chapter. For an efficient 
preview use the Chapter Prev iew quest ions, which constitute the framework for understand-
ing the chapter. Previewing works best if you do it jus t before lecture. With the main points in 
mind you will unders tand the lecture better. This in turn will result in good and complete notes. 
Study Tip 
To unders tand this chapter, focus on sys tems and cycles. Study inputs and outputs : 
what goes into and wha t c o m e s out of each process descr ibed. 
How much t ime should you devote to previewing? Obviously, more t ime is better than less. 
But even a brief (five- or ten-minute) preview session jus t before lecture will p roduce a result 
you will notice. For a refresher on why previewing is so important , see Part 1, Chapter 3, How 
to Be Successful in Geology. 
Chapter Preview 
• H o w do organ i sms a n d the Ear th interact? 
Brief answer: Life processes influence weathering, precipitate minerals, and modify the 
composit ion of the atmosphere and oceans. Geobiology is the study of these interactions. 
• W h a t is the b iosphere? 
Brief answer : T h e b iosphere is the part of our planet that contains all l iving 
organisms. I t is character ized by metabol ic processes that influence and even control 
geologic processes . 
• W h a t is metabo l i sm? 
Brief answer : Metabo l i sm is the process that all organisms use to convert inputs into 
outputs . For example , photosynthes is by plants uses three inputs (sunlight, carbon 
dioxide , and water) to p roduce t w o outputs , sugar and oxygen gas. 
• H o w important are microbes? 
Brief answer : Mic robes are the mus t abundant and diverse organisms on Earth . They 
regulate geologic processes such as weather ing of minerals and rocks , precipitat ion of 
certain sedimentary minerals , and product ion of gases such as oxygen and carbon 
dioxide. 
• H o w did life or ig inate , a n d w h a t s igns do we have of life on the young Ear th? 
Brief answer : S imple molecules of methane , ammonia , and water on the pr imit ive 
Earth are thought to have combined to form amino acids, which then combined to 
form prote ins . T h e oldest s igns of life on Ear th are shown in F igure 11.15. 
• W h a t is the difference b e t w e e n radiat ion a n d ext inct ion? 
Brief answer: Radiat ion is the relatively rapid development of new types of organisms. 
W h e n groups of organisms are no longer able to adapt to changing environmental 
condit ions or to compete with a superior group of organisms, they become extinct. 
• C a n life exist on o ther p lanets? 
Brief answer : For every star, there is a habi table zone where water will be stable. 
If a p lanet is within a habi tab le zone , there is a chance that life might have originated 
there. Refer to F igure 11.25. 
1 3 4 PART II C H A P T E R 12 
Chapter Preview 
• W h y does vo lcanism occur? See Figure 12.1 (Study Guide page 133) . 
Volcanism occurs when m a g m a rises buoyant ly to the surface. 
• W h a t are the three major lava types a n d h o w do they relate to erupt ive style and 
volcanic landforms? 
Mafic (basalt) , in termediate (andesi te) , and felsic (rhyolite) lava types produce 
erupt ions that range from relatively gentle basalt ic flows to highly explosive rhyolitic 
erupt ions. See Figure 12 .11 . 
• H o w is vo lcanism related to plate tectonics? 
Volcanism is concentrated at convergent and divergent plate boundar ies and hot spots. 
See Figure 12.20. 
• W h a t are s o m e of the beneficial effects of vo lcanism? 
Volcanic processes create new ocean floor, our oceans and a tmosphere , ore deposits, 
and geothermal energy. 
Vital Information from Other Chapters 
Review the following sections in Chapter 4: How Do Igneous Rocks Differ from One Another? 
and Igneous Activity and Plate Tectonics. 
Previewing Tip 
See the f lowchart H o w to Study Geology on Study Guide page 3 for addi t ional ideas on 
previewing. T h e mos t useful answer to a preview quest ion is one that you will actually 
r e m e m b e r dur ing lecture. Simplify to something you can c o m m i t to memory . 
Preview quest ions are like a fresh, undecora ted Chr i s tmas tree. Dur ing lecture you 
decora te the tree. 
During Lecture 
One goal for lecture should be to leave ther o o m with good answers to the preview questions. 
• Focus on unders tanding how volcanoes work. W h e r e the m a g m a comes from 
(for example , iron-rich ocean crust or silica-rich cont inental crust) has every-
thing to do with the explosiveness of the eruption and the shape of the result-
ing volcanic landform. 
• F o c u s part icularly on unders tanding Figures 12.1 (how a volcano sys tem 
works) and 12.11 (volcanic eruptive styles and landforms) . I t m a y be helpful 
to bookmark these figures and have them handy dur ing lecture for quick ref-
erence . Do annotate text figures wi th c o m m e n t s m a d e by your instructor. 
• Want ideas on taking good notes? If you haven ' t already done so, read the dis-
cuss ion of note taking in Part I , Chapter 3, of the Study Guide . You can use the 
Note-Taking Checkl is t before you go to lecture as a one-minu te reminder of 
wha t to do to improve your note- taking skill. After lecture, use the checkl is t as 
a quali ty check. 
Before Lecture 
Volcanoes 1 3 5 
After Lecture 
Review Notes 
Right after lecture, whi le the material is fresh in your mind, is the perfect t ime to review and 
improve your notes . 
Check Your Notes: Have you. . . 
• clearly identified important points? Example : You should have clear descript ions of 
the three lava types , information about the chemica l composi t ion and explosiveness 
of each type , and legible sketches of each landform discussed dur ing the lecture. 
u added sketches of the landforms associated with each eruptive style? Refer to Figure 
12 .11 . Example : C o m p a r e the slope of a shield volcano with that of a composi te 
volcano by drawing a simplified sketch of each one showing how steep each volcano 
is and the relative area each volcano is likely to cover. No fancy ar twork is needed, 
jus t a s teep inverted V for one and a flattened inverted V for the other. The shield 
volcano would be flattened and spread out and the composi te (stratovolcano) steeper. 
Sketching provides a good check on how well you unders tand the differences. 
• inc luded a sketch of the basic features of a volcanic geosys tem? Use Figure 12.1 
as a reference. 
• inc luded a sketch similar to F igure 12.20 that shows how volcanism relates to 
plate tec tonics? 
• developed a table that summar izes the three lava types in terms of rock composi t ion 
and associated landforms? Comple t ing the table in Pract ice Exercise 1 will give you a 
summary of Chapte r 12. 
Note-Taking Tip: Use abbreviations to speed up your note taking 
ig rock —* igneous rock 
strat —> st ra tovolcano 
c o m p —» compos i t e volcano 
HP -* hot spot 
V -* volcanism or volcano 
sh v -* shield volcano 
B -» basal t 
rhy -* rhyoli te or rhyolitic 
mag —» m a g m a 
Put these abbreviat ions in the margin to d raw your attention to them later. 
TQ (test ques t ion) 
? areas whe re you feel lost or unclear about the material . Use these ? flags as a 
r eminder that you need to follow up via further study or a conference wi th your 
instructor, tutor, or s tudy partner. 
Exploring Earth's Interior 159 
What has seismic tomography revealed about structures 
in the mantle? 
• These CAT scan- l ike images of the Ear th ' s interior reveal how tectonic plates 
vary from very thin under the mid-ocean ridges to very thick under continental 
cratons. Also revealed are features associated with mant le convection, such as 
sinking slabs of l i thosphere and superplumes . Refer to Figure 14.9. 
How hot does it get in Earth's Interior? 
• Within normal continental crust, temperature increases at a rate of 20° to 30° C 
per kilometer. T h e rate of temperature increase slows way down in the mant le 
and core. The mos t rapid change in temperature (steepest geothermal gradient) 
occurs in the outermost layer of our planet. This is not surprising, if you con-
sider how rapidly tempera ture changes from the outside to the inside of a 
kitchen oven door. Refer to Figure 14.8. 
• Seismic and laboratory studies suggest that the temperature in the outer l iquid 
core is h igher than 3000°C, and at the Ear th ' s center the temperature may reach 
6000° to 8000°C. Refer to Figure 14.8. 
What does Earth's gravity and isostatic rebound 
tell us about the interior? 
• Measur ing the rate of postglacial isostatic rebound provides information on 
the viscosi ty of the mant le and how it affects rates of uplift and subsidence of 
the buoyant l i thosphere. Refer to Earth Issues 14 .1 . 
• The observed gravity field is in agreement with the pat tern of mant le convec-
tion inferred from seismic tomography. Ear th Issues 14 .1 . 
What does Earth's magnetic field tell us about the 
fluid outer core? 
• Ea r th ' s magne t i c field bas ica l ly looks l ike a d ipolar bar magne t . Refer to 
F igure 1.12. 
• A g e o d y n a m o explains how Ear th ' s magnet ic field is generated. Rap id con-
vect ion in the mol t en outer core is though t to stir up electr ical cur rents in the 
conduc t ing iron to create the major componen t of the magnet ic f ield. 
• The magnet ic field changes strength, posit ion, and polarity over t ime. There is 
a nondipole componen t . Bo th the dipole and nondipole componen t s exhibi t 
secular variat ions over t ime spans of decades . Reversals in polari ty also occur 
over t ime spans of thousands of years . Refer to Figure 14.15. 
What is paleomagnetism and what is its importance? 
• Preserved in some rocks is a clear record of past changes in the orientat ion of 
Ear th ' s magne t i c f ie ld . T h e chronology of magnet ic f ie ld reversals has been 
worked out so that the direct ion of remnant magnet iza t ion of a rock formation 
is often an indicator of its s trat igraphic age. Refer to Figures 14.14 and 14.15. 
N o t e : The pat tern of magnet ic anomal ies produced by pa leomagnet ic reversals 
recorded by ocean floor rock provided important evidence for seafloor spread-
ing. Refer to F igure 2.10. 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: The Earth's interior layers 
It is important to unders tand Ear th ' s layered composi t ion . Label the Ear th layers in the fol-
lowing figure, taking special note of the information about the composi t ion of each. Refer to 
Figures 1.7, 14.5, and 14.6 and the accompanying text section The Layer ing and Composi-
t ion of the Interior. 
1 6 0 PART II C H A P T E R 14 
Exercise 2: Characteristics of Earth's internal layers 
Comple te the table by filling in the b lanks and comple t ing the sentences . Shaded boxes 
remain blank. Refer to text and figures in Chapters 1, 4, and 14. Key figures inc lude 1.5, 1.7, 
1.8, 4 .2 , 4 . 1 1 , 14.6, and 14.8. 
1 62 PART II C H A P T E R 14 
Exercise 3: Evidence for the asthenosphere and its significance 
A. Briefly discuss one line of evidence support ing the presence of an asthenosphere in 
the upper mant le . 
B. W h a t is the significance of the as thenosphere to plate tectonic theory? 
Hint: Information in both Chapters 2 and 14 will help you comple te this assignment. 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. Ear th ' s core has a radius that is about of the Ear th ' s radius . 
Hint: Refer to Figure 14.5. 
2. T h e thickness of Ear th ' s tectonic plates is 
A. the same on the continents as under the oceans . 
B. at its thinnest under the oceans . 
C. at its thinnest in the cont inents . 
D . complete ly unknown. 
Hint: Refer to Figure 1.7 and 14.6. 
3. The likely composi t ion of the upper mant le is 
A. felsic. C. ul tramafic. 
B. mafic. D. carbon (d iamonds) . 
4. Which of the following consti tutes the rigid, outer layer of Ear th ' s tectonic plates? 
A. as thenosphere C. crust 
B.l i thosphere D. mant le 
5. Cont inental crust has an overall composi t ion corresponding closely to that of 
A. ultramafic. C. felsic to intermediate . 
B. mafic. D. peridoti te . 
6. The l i thosphere is a layer, as opposed to the as thenosphere . 
A. plastic C. weak 
B. fluid D. rigid 
7. The inference that Ear th ' s outer core is l iquid is supported by the observat ion that 
A. P waves do not pass through it. 
B. S waves do not pass through it. 
C. P waves travel more rapidly through it. 
D. S waves travel more slowly through it. 
8. The highest density componen t of the Earth is 
A. the mant le . C. the core . 
B. continental crust. D. the whole Earth. 
9. Ear th ' s north magnet ic pole is located 
A. at the north geographic pole . 
B. in Alaska. 
C. be tween Greenland and Baffin Island. 
D. in China. 
Hint: Refer to Figure 14.10 and an atlas. 
10. The Ear th ' s magnet ic f ield is thought to be generated by 
A. pe rmanen t magne t i sm of minerals within the mant le . 
B. pe rmanen t magne t i sm of the solid iron-rich inner core . 
C. electrical currents generated by movement of the liquid outer core . 
D. electrical currents generated by convect ion in the as thenosphere 
A. 1/8 
B . 1/4 
C. 1/2 
D . 3/4 
Exploring Earth's Interior 1 6 3 
11 . As opposed to the l i thosphere, the as thenosphere is a layer. 
A. brittle C. mol ten 
B . weak D. rigid 
12. Minera l grains in sediments b e c o m e magnet ized by the Ear th ' s magnet ic field when 
A. they are s truck a sharp blow by a meteori te . 
B. i ron-rich minera ls align parallel to the Ear th ' s magnet ic f ie ld . 
C. the Ear th ' s magnet ic f ield reverses itself. 
D. electricity from l ightning strikes passes through the lava beds . 
Hint : Refer to F igure 14.14. 
13. W h i c h layer of the Ear th experiences the most rapid increase in temperature with 
increasing dep th? 
A. l i thosphere C. mant le 
B. as thenosphere D. liquid outer core 
Hint : Refer to F igure 14.8. 
14. On which boundary in the Ear th 's interior does the greatest change in composit ion occur? 
A. l i thosphere -as thenosphere boundary 
B . c ru s t -man t l e boundary 
C. m a n t l e - c o r e boundary 
D. boundary be tween the outer and inner core 
Test-Taking Tips: Test taking and learning style 
Knowing your learning style can help dur ing exams. Cons ider the following. 
Visual Learners 
• If you are a visual learner you probably pay better attention to direct ions that are 
writ ten out (visual) than to spoken direct ions. Rely on writ ten direct ions when they 
are avai lable. If your exam proctor gives the direct ions verbally wi thout a visual you 
mus t compensa te . M a k e yourself listen and d o n ' t hesi tate to ask as many quest ions as 
you need to to get the direct ions straight. 
• W h e n you get s tuck on an i tem, activate your visual memory. Close your eyes and 
picture flow charts , pictures , f ield exper iences or even lines of text. 
Auditory Learners 
• You probably pay better at tention to direct ions that are spoken than to direct ions that 
are wri t ten out. Re ly on spoken direct ions w h e n they are available. If the direct ions 
are on a slide, compensa te ! M a k e yourself read them. 
• Repea t writ ten direct ions quietly to yourself (moving your lips is often enough) . 
• W h e n you get stuck, r e m e m b e r your lecturer 's voice covering this section. 
Kinesthet ic Learners 
• You probably do best wi th direct ions that al low you to work an example . 
Unfortunately, i t is a rare c lass room e x a m that provides examples or samples as part 
of the direct ions . So you will need to m a k e up you own. Take a minu te to translate the 
direct ions into someth ing you can do, or ask the instructor for a sample or example . 
Be sure to interact. R e m e m b e r that you learn by doing. 
There a re a var ie ty of th ings k ines the t i c l ea rners find helpful w h e n they ge t s tuck on a 
test i t em. 
• W h e n you get stuck, m o v e in your chair or tap your foot, to tr igger memory . 
• Feel yourself doing a lab procedure . 
• Sketch a f lowchart to un lock m e m o r y of a process . 
• Stuck on a geology p rob lem? Sketching what is be ing descr ibed (what is "g iven" in 
the p rob lem) may un lock your m e m o r y and get you started. 
1 64 PART II C H A P T E R 14 
15. The crust is typically thickest beneath 
A. h igh mounta in ranges and plateaus on the cont inents . 
B. ocean-spreading centers . 
C. cont inental interiors like the Great Plains in North Amer ica . 
D. passive margins of cont inents where topography is very flat. 
H i n t : Refer to Figure 1.7. 
16. Significant increases in S-wave velocity at about 400 and 650 ki lometers depth are 
explained by 
A. changes in the chemical composi t ion of the mant le . 
B. a col lapse of the crystal structures to more close by packed forms. 
C. changes in the degree of partial melt ing within the mant le . 
D. rapid increases in temperature . 
H i n t : Refer to Figure 14.6. 
17. The Ear th ' s core is inferred to be composed of most ly iron because 
A. iron is naturally very abundant . 
B. mos t meteori tes represent ing the interstellar matter from which the planets formed 
are rich in iron. 
C. iron is very dense , so its presence in the core would account for the Ear th ' s average 
density. 
D. all of the above. 
18. Without any knowledge of what seismic waves tell us about the Ear th ' s interior, why is 
it unreasonable to assume that a large por t ion of the lower mant le is mol ten? 
A. Actually, i t could be molten. We jus t don ' t see evidence for i t because silicate mag-
mas are t rapped within the Earth due to the confining pressures . 
B. Direct measurements show that the temperature at the core /mant le boundary is not 
high enough to mel t the lower mant le . 
C. The magnet ic f ield strength would be greatly reduced if more of the Ear th ' s interior 
was mol ten . 
D. Silicate m a g m a s are less dense and would rise to the surface, so we should observe 
widespread volcanic activity across the Ear th ' s surface. The mol ten iron-rich outer 
core is too dense to r ise. 
19. As rocks exper ience increased pressure with depth, P waves in general will as 
they migra te through them. 
A. travel faster 
B. travel s lower 
C. travel at the same velocity 
D. rapidly die out 
20. W h e n a reversal of the Ear th ' s magnet ic field occurs , 
A. the sense of rotat ion of the Earth is also reversed. 
B. the Earth flips over in its orbit. 
C. the magnet ic polari ty of the Ear th reverses so that the north end of a magnet ic com-
pass needle points toward the south geographic pole . 
D. a lmost all the igneous sedimentary rocks of the ocean floor reverses in magnet iza-
tion to match the new orientation of the magnet ic f ield. 
2 1 . The M o h o , o r M o h o r o v i c i c discontinuity be tween the crust and the mant le , was f i r s t 
detected from 
A. the abrupt decrease in seismic velocit ies as they cross the discontinuity. 
B. the abrupt increase in seismic velocities as they cross the discontinuity. 
C. the S-wave shadow zone through which S waves do not pass . 
D. the observat ion that no ear thquakes occur below the M o h o . 
Exploring Earth's Interior 165 
22. Support ing ev idence for heat transfer by convect ion within the mant le comes from 
A. tomography and Ear th ' s gravity f ie ld . 
B. the bulk densi ty of the Earth. 
C. postglacial isostatic rebound. 
D . Ear th ' s magne t f i e ld . 
23. The "Cre taceous quiet z o n e " is a n a m e for a(n) 
A. per iod w h e n dinosaurs were very sedate. 
B. t ime w h e n plate mot ions s lowed way down. 
C. b reak in volcanic activity on Ear th due to a lack of mant le superplume activity. 
D. especial ly long per iodof normal polari ty of Ear th ' s magnet ic f ie ld. 
H i n t : Refer to F igure 14.15. 
24. The P-wave shadow zone is caused by the way the Ear th ' s core 
A. refracts the se ismic waves . 
B. reflects the se ismic waves . 
C. absorbs the P waves . 
D. b locks the P waves . 
25. As the l i thosphere cools slowly by the conduct ion of heat, i t becomes 
A. less dense and rises. 
B. soft and weak . 
C. denser and r ises . 
D. denser and subsides . 
H i n t : Refer to F igure 14.7. 
26. Ear th 's tectonic plates are located in the 
A. core , where their m o v e m e n t is driven by intense heat and pressure . 
B. mant le , where their movemen t is driven by convection. 
C. l i thosphere , where their movemen t is driven by gravity. 
D. a tmosphere , where their movemen t is driven by the prevail ing westerl ies . 
CHAPTER 15 
The Climate System 
The Climate System 1 6 7 
Chapter Preview 
• W h a t is the c l imate sys tem? 
Brief answer : The major componen t s of the cl imate system are the a tmosphere , 
hydrosphere , l i thosphere, and biosphere . It is important to understand how these 
systems interact with each other via feedback mechan i sms . Refer to Figure 15.1. 
• W h a t is the greenhouse effect? 
Brief answer: Carbon dioxide and other trace a tmospher ic gases are transparent to 
sunlight but absorb heat (infrared radiat ion), which warms Ear th ' s surface 
environments . Refer to Figure 15.7. 
• H o w has Earth 's c l imate changed over t ime? 
Brief answer : T h e largest changes are the 100,000-year glacial cycles. But there are 
also significant short- term cl imate cycles that average 1.000 and 10,000 years . Refer 
to F igure 15.10. There are also r a n d o m cl imate events, like El N ino . Note that we are 
currently living in an except ional t ime, the mos t pro longed stable w a r m period in the 
last 400 ,000 years . 
• W h a t is the carbon cycle? 
Brief answer : Geochemica l cycles trace the flux of Ear th 's e lements like carbon 
from one reservoir to another. The carbon cycle describes the movement of carbon 
be tween four main reservoirs: (1) the a tmosphere ; (2) the global ocean, including 
marine organisms; (3) the land surface, including terrestrial animals , plants , and soils; 
and (4) the deeper l i thosphere. The carbon cycle is part icularly important because of 
its strong link to life processes and cl imate change . Refer to Figure 15.14. 
• How can internal geologic processes cause c l imate change? 
Brief answer : Over the short te rm of a few years , sulfuric acid aerosols and volcanic 
ash ejected from large volcanic erupt ions can absorb solar radiat ion before i t reaches 
the lower a tmosphere and thus decrease global temperatures . Over the long term of 
mill ions of years , plate tectonic movement s can shift cont inents over the poles , 
stabilizing polar ice caps; b lock or open gateways to ocean currents ; and cause uplift, 
which alters weather ing sys tems and rates of chemical weather ing that draw down 
atmospher ic carbon dioxide. 
• Was the twent ie th-century w a r m i n g caused by h u m a n activit ies? 
Brief answer : Global warming of about 0.6°C dur ing the twentieth century correlates 
with the significant rise in a tmospher ic C 0 2 and other greenhouse gases caused by 
fossil-fuel burning, deforestat ion, and other human activities. 
Vital Information from Other Chapters 
Review the section Classification of Chemica l and Biological Sediments and Sedimentary 
Rocks in Chapte r 5 . Also preview pages 5 2 3 - 5 2 8 in Chapter 2 1 , which discuss cl imate 
change dur ing the last series of ice ages . 
The geob io log ica l p rocesses you learned in Chap te r 11 play a significant ro le in the cli-
mate sys tem. C a r b o n is r e m o v e d from the a tmosphe re via the b iochemica l p rocess of 
photosynthesis (F igure 11.4) and re turned to the a tmosphe re via another b iochemica l 
Before Lecture 
Before you attend lecture, spend some t ime previewing the chapter. For an efficient preview, 
use the Chapter Prev iew quest ions . 
168 PART II C H A P T E R 15 
process , an ima l respirat ion. Oxygen makes up 21 percent of Ear th ' s a tmosphere . Oxygen is 
supplied and maintained homeostat ical ly by living organisms via the metabol ic process of 
photosynthes is (see Figure 11.4 and the section Metabo l i sm on pages 2 4 5 - 2 4 6 ) . Microbes, 
such as cyanobacter ia , p roduced Ear th ' s original oxygenated a tmosphere (see the section 
Origin of Ear th ' s Oxygena ted Atmosphere on pages 2 5 7 - 2 5 8 ) . Finally, methane-producing 
microbes contr ibuted the methane supplies that "burped" out of sediments , triggering global 
warming and an extinction event that marks the P a l e o c e n e - E o c e n e boundary . 
As you read Chapter 15, keep in mind that the c l imate sys tem is composed of many sub-
sys tems. Cl imate is a tapestry of complex and fascinating interact ions. 
During Lecture 
• Keep the big picture in mind as you take notes. Chapte r 15 tells the story of 
Ear th ' s c l imate system and how global c l imate results from interactions 
be tween four Ear th system components : a tmosphere , hydrosphere , b iosphere , 
and l i thosphere. H u m a n activities are becoming an increasingly important fac-
tor influencing how Earth sys tems function. Focus on unders tanding the com-
ponents , fluxes, and feedbacks in each system. 
• Because of the social impor tance of global c l imate, there may be opportuni t ies 
for discussion/debate activities. Previewing the chapter will p repare you to 
take part in these activities. 
After Lecture 
Review Notes 
The perfect t ime to review your notes is r ight after lecture. The fol lowing checklist contains 
both general review tips and specific suggest ions for this chapter. 
Check Your Notes: Have you. . . 
• wri t ten a s u m m a r y of wha t is covered in this lec ture? Your s u m m a r y should say 
someth ing significant about how human activit ies change the global env i ronment 
and the potent ia l for global wa rming dur ing your l i fet ime. Sugges t ion : Wr i t e a brief 
pos i t ion paper on a Chap te r 15 issue that conce rns you. Ask yourse l f wha t Ear th 
sys tem informat ion in Chap te r 15 is relevant to the issue . Try to deve lop a position 
that is reasonable and cons is tant wi th exis t ing sc ience . 
• added important visual material to your notes? Suggest ions: Draw overview sketches 
of the cl imate system (Figure 15.1) and the carbon cycle (Figures 15.14 and 15.15). 
To understand how cl imate changes over t ime, pay part icular at tention to the different 
t ime scales (years, decades , centuries , thousands of years) used in Figures 15.10, 
15.16, and 21.25. 
Intensive Study Session 
Set priorities for studying this chapter. Give highest priority to activities that involve answering 
questions. We recommend the following strategy for learning this chapter. 
• Text . Preview the key figures in Chapter 15, Figure 15.7 (the greenhouse effect) 
and Figure 15.14 (the carbon cycle). You have to understand these figures to 
answer the Rev iew Ques t ions . Figures 15.2, 15.3, and 15.11 and Earth Issues 
15.2, 15.13, and 15.16 also contain important information, relevant to Chapters 
15, 2 1 , and 23 . 
The Climate System 1 69 
S o m e t i m e before your exam, answer the exercises at the end of the chapter. 
These are shor t -answer quest ions and w o n ' t take long i f you know the mate-
rial. Focus on Exercises 2, 4, and 7 and Thought Quest ions 2, 4, and 6. 
• Pract ice Exerc ises . Comple te Pract ice Exercises 1 and 2. They will help you 
r e m e m b e r the mos t impor tant ideas in the chapter. 
• Rev iew Quest ions . Try answer ing each of the review quest ions to check your 
unders tanding of the lecture. Check your answers as you go, but do tryto 
answer the quest ion before you look at the answer. 
• W e b Site S tudy Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Co mp le t e the Concept Rev iew and W e b Rev iew Quest ions . Pay part icular 
at tention to the explanat ions for the answers . The Onl ine Rev iew Exercise 
Identify the Parts of the Carbon Cycle will help you inventory major co mp o -
nents of this geochemica l cycle . 
Did you know that i t takes about 2 pounds of coal to p roduce the energy 
for you to copy a m e g a b y t e of mus ic off the Internet and that this re leases 
4 p o u n d s of ca rbon d iox ide into the a tmosphe re? The G e o l o g y in Pract ice 
exercises for Chapte r 15 explore how this is possible . 
Exam Prep 
Materials in this section are mos t useful during your preparat ion for exams. The Chapter 
S u m m a r y and the Pract ice Exercises and Rev iew Quest ions should simplify your chapter 
review. Read the Chapter S u m m a r y to begin your session. I t provides a helpful overview 
that should refresh your memory . 
Next , work on the Pract ice Exerc ises and Rev iew Quest ions . Comple te the exercises 
and quest ions jus t as you would for an exam, to see how well you have mastered this chap-
ter. After you answer the ques t ions , score them. Finally, and most important , review each 
question you missed. Identify and correct the misconcept ion(s) that resulted in your answer-
ing the quest ion incorrectly. 
Chapter Summary 
What is the climate system? 
• Major componen t s of the Ear th ' s c l imate system are the a tmosphere , hydro-
sphere, l i thosphere, and b iosphere . Refer to Figure 15 .1 . 
• Ear th ' s surface would be much colder wi thout the presence of g reenhouse 
gases like water and carbon dioxide in the a tmosphere . 
• Ocean currents play a major role in distributing heat across the Ear th because 
water has a very high capaci ty for storing heat . 
• Topography affects c l imate by influencing the flow of our a tmosphere . 
• Volcanic eruptions affect climate by changing the composit ion of the atmospheric 
gases and by adding dust and haze that increase the albedo of the atmosphere. 
• Various factors may exert a posit ive or negative feedback on the cl imate sys-
tem. In some cases , feedback mechan i sms can act to stabilize Ear th ' s c l imate, 
and in other cases they may destabi l ize i t by amplifying c l imate change . 
What is the greenhouse effect? 
• Carbon d ioxide and other t race a tmospher ic gases act like the glass windows 
in a g reenhouse . They are t ransparent to sunlight but absorb heat (infrared 
radiat ion) , which warms Ear th ' s surface environments . Refer to Figure 15.7. 
How has Earth's climate changed over time? 
• The largest changes are the 100,000-year glacial cycles. 
• The alternation be tween glacial and interglacial ages observed dur ing the 
Pleis tocene epoch is explained best by the Milankovi tch cycles . Refer to Fig-
ures 15.11 and 21 .25 . 
• T h e r e are also significant short- term cl imate cycles that average 1,000 and 
10,000 years . Refer to Figures 15.10 and 15.16, and note the regulari ty of 
these cyc les . N o t e a lso that we are cur ren t ly l iving in the m o s t p ro longed 
stable w a r m period in the last 400 ,000 years . 
• Short- term variations of cl imate are associated with El N ino events and large 
volcanic erupt ions. 
What are geochemical cycles and how can they 
impact climate? 
• Geochemica l cycles t race the flux of Ear th ' s e lements , like carbon, from one 
reservoir to another. 
• Unders tanding the carbon and ca lc ium cycles is important because of their 
s t rong link to life processes , cl imate, and the greenhouse effect. Refer to Fig-
ures 15.13 and 15.14. 
• The release of carbon dioxide by the burning of fossil fuels is having a signif-
icant impact on the flux of carbon from the l i thosphere into the a tmosphere . 
Refer to Figure 15.15. 
What caused the twentieth-century warming? 
• Be tween the end of the nineteenth century and the beginning of the twenty-
first, the mean surface temperature rose by about 0.6°C. Refer to F igure 15.16. 
• F r o m a variety of c l imate indicators, scientists have concluded that c l imate 
during the thousand years that preceded the twentieth century exper ienced an 
irregular but steady global cool ing of about 0.2°C and the m a x i m u m fluctua-
tion in mean temperatures dur ing any one of the nine previous centur ies was 
r e
 probably less than 0.3°C. 
le 
, • C l imate models that include changes in a tmospher ic g reenhouse gases as a 
factor match the global temperature rise and also reproduce the pat tern of tem-
perature change both geographical ly and wi th alti tude in the a tmosphere . 
Figure 15.16. Earth heats up. 
A comparison of Earth's aver-
age annual surface temperature 
with C 0 2 concentrations in the 
atmosphere, showing that the 
recent warming trend corre-
lates with the increase in C 0 2 
caused by human activities 
since the industrial revolution. 
1 70 PART II C H A P T E R 15 
fit is virtually impossible to change one thing in a complex 
system without affecting other parts of the system, often in as yet 
unpredictable ways. 
— A N O N Y M O U S 
How hard to realize that every camp of men or beast has this glorious 
starry firmament for a roof! In such places standing alone on the mountain 
top it is easy to realize that... we all dwell in a house of one room— 
the world with the firmament for its roof—and are sailing the celestial 
spaces without leaving any track. 
— J O H N M U I R , 1 8 9 0 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Conceptual map/Flowchart of a climate factor 
Construct a conceptual map/flowchart characterizing one other factor besides clouds that can 
affect Earth 's cl imate. Also provide a brief written explanation, as in the clouds example illus-
trated. Follow these guidelines. 
• Be sure you u n d e r s t a n d and c lear ly exp la in h o w the factor causes c l ima te to 
change . 
• Include in your f lowchar t poss ib le posi t ive and negat ive feedback sys tems. 
For example , the cool ing effect of low c louds , l ike s torm c louds , will r educe 
evaporat ion rate and m a y have a shor t - term negat ive feedback on addi t ional 
cloud format ion . 
Example: T h e fol lowing conceptual map/f lowchart shows how clouds impact c l imate . 
Climate C h a n g e Factor : C l o u d s 
The Climate System 1 71 
Explanation o f f low c h a r t 
In a simple model, as air temperature increases, more moisture is evaporated and held in 
the atmosphere. This usually leads to more cloud cover. Clouds increase the albedo of the 
atmosphere and may cool the Earth's surface by reducing the amount of sunlight reaching 
the surface. Increasing cloud cover potentially would have a negative effect on global warm-
ing. Clouds may also have a warming effect on the Earth's surface by reducing the loss of 
heat to space during the night. 
Note: How clouds affect climate is still debated. High clouds have been shown to cause 
warming and low clouds cooling at the Earth's surface. There is growing evidence that 
clouds have an overall but not very great net cooling effect. 
1 72 PART II C H A P T E R 15 
Conceptual Map/F lowchar t showing h o w impact s cl imate 
Explanation 
Exercise 2: Release of carbon dioxide from the burning of fossil fuels 
A. Expla in why the release of carbon dioxide from the burning of fossil fuels might lead 
to an increase in c loud cover 
B. Would an increase in c loud cover have a posit ive or negative affect on c l imate? Explain. 
For example , would an increase in cloud cover enhance or reduce the effect of increas-
ing carbon dioxide in the a tmosphere? See pages3 5 3 - 3 5 5 in the tex tbook for examples 
of feedback mechan i sms that can help to ba lance or stabilize the c l imate system. 
The Climate System 1 73 
The balance of evidence suggests a discernible human 
influence on global climate. 
— U N CLIMATE COMMITTEE, I P C C , 1995, p . 4 
Exercise 3: Flow of carbon through Earth's systems and reservoirs 
Carbon dioxide is an important greenhouse gas that can greatly impact Earth 's surface temper-
atures. Because the Earth is a closed system, the carbon cycle and distribution of carbon in the 
various reservoirs is a very important componen t of any model for how climate changes . 
Comple te the table to summar ize the flow of carbon through Ear th ' s systems and reser-
voirs. Flux is the amoun t of energy or mat ter flowing through a given area or reservoir in a 
given t ime. Refer to Figures 15.7, 15.13, 15.14, and 15.15, and the accompanying text in 
Chapter 15. 
Carbon fluxes 
Brief description 
of flux Direction of flux 
Climatic impact/ 
implications 
Photosynthesis 
and precipitat ion 
of carbonates 
Sedimentation 
Carbon is fixed in living 
organisms, which ultimately 
contribute to organic matter in 
sediments, coal, and oil. 
Calcium and carbonate ions 
combine to produce calcium 
carbonate, which can precipitate 
and collect to form limestone or 
help cement other rock particles. 
Carbon flows from the 
atmosphere and oceans into 
rock—the lithosphere. 
Climate cools. 
Carbon dioxide is drawn out 
of the oceans and atmosphere. 
The loss of CO2 from the 
oceans results in a reduction 
of CO2 in the atmosphere. 
Volcanism 
Chemical 
weathering 
Metamorphism 
Human activities: 
Combustion of 
fossil fuels 
C02 in rainwater combines with 
minerals in rock to form calcium 
carbonate. 
Heating, recystallization, and 
decomposition of rocks during 
metamorphism can release large 
amounts of C02 • 
The burning of fossil fuels 
releases large amounts of C02 
into the atmosphere. 
Carbon flows from the 
atmosphere and oceans into 
the crust. 
Carbon flows from the rocks 
(the crust) into the atmosphere 
and oceans. 
Carbon flows from the litho-
sphere (coal, oil, and gas) into 
the oceans and atmosphere. 
Climate cools. 
Carbon is being drawn out of 
surface environments and 
stored in the crust. Uplift of 
high plateaus and mountains 
may enhance this flux. 
Climate warms. 
Increased levels of C02 in 
the atmosphere enhance the 
greenhouse effect, which acts 
to trap heat energy and slow 
down the loss of heat to space. 
Refer to this Web site for the latest information on global warming: 
h t tp : / /www.ngdc .noaa .gov/pa leo/g lobalwarming/home.h tml 
1 74 PART II C H A P T E R 15 
Review Questions 
Answers and explanat ions are provided at the end of this Study Guide . 
1. W h i c h of the following gases is most abundant in the Ear th ' s present atmosphere? 
A. ni t rogen 
B. carbon dioxide 
C. water 
D. oxygen 
2. W h y is carbon dioxide considered a greenhouse gas? 
A. It absorbs heat. 
B. It reflects radioactivity. 
C. I t absorbs UV light. 
D. It reflects sunlight. 
3. Ear th ' s global temperature trend is clearly 
A. upward over the last century. 
B. downward over the last century. 
C. unchanged over the last few decades . 
D. variable, but there has been no overall change . 
Hint: Refer to Figure 15.16. 
4. I t has been suggested that the uplift of the Hima layan mounta ins and the Tibetan plateau 
could have contr ibuted to or even caused a global cool ing. The l ink between the 
Himalayan mounta ins and cl imatic cool ing is probably related to 
A. the coll ision of India with Asia, t r iggering volcanism and increasing the C 0 2 con-
centrat ion in the a tmosphere . 
B. the uplift intensifying the monsoon and associated physical and chemica l weather-
ing, which resulted in a d raw-down of carbon dioxide from the a tmosphere . 
C. the fact that h igh mounta ins generate more c louds, and their a lbedo (reflectivity) 
cools the Ear th ' s surface. 
D. El N ino and the North Atlant ic deep-water current. 
5. W h i c h of the following is N O T associated with El Nino events? 
A. t rade winds s lackening or reversing direction 
B. volcanic activity 
C. change in ocean circulation pat terns 
D. wor ldwide anomalous weather pat terns 
Hint: Refer to Earth Issues 15.2. 
6 . As the oceans become warmer , C 0 2 i s re leased from the oceans into the 
a tmosphere , resul t ing in a effect. 
A. more/posi t ive C. more/negat ive 
B. less/negative D. less/positive 
Hint: I s C 0 2 more or less soluble in warmer water? Refer to Chapte r 20 , Deep-Sea 
Sedimenta t ion, and Figure 20 .24 . 
7. The increase of the average tempera ture on Ear th is l inked to burning fossil fuels 
because the 
A. burning process consumes oxygen . 
B . burning process consumes C 0 2 . 
C . burning process generates C 0 2 . 
D. smoke given off by burning insulates the Earth . 
The Climate System 1 75 
8. T h e surface tempera tures on Venus, Earth, and to a lesser extent Mar s are all wel l above 
what can be expla ined by their dis tance from the Sun. W h a t other factor significantly 
contr ibutes to elevated surface temperatures for these inner planets? 
A. the p resence of g reenhouse gases , like carbon dioxide 
B. interior heat 
C. dust from winds torms and volcanoes , which acts to trap heat 
D. p resence of argon and ni t rogen in the a tmosphere 
9. At present the greatest f lux of carbon dioxide occurs be tween our a tmosphere and 
A. oceans . 
B . volcanoes . 
C. living organisms. 
D . h u m a n s . 
Hint: Refer to F igures 15.14 and 15.15. 
10. W h i c h of the fol lowing contr ibutes the most carbon to the a tmosphere? 
A. h u m a n deforestat ion and agriculture 
B. p lant uptake of carbon 
C. ocean air gas exchange 
D. burn ing of fossil fuel by h u m a n s 
Hint: Refer to Figure 15.15. 
11. M o s t of the mass of the a tmosphere , where weather forms and what commerc ia l je ts fly 
in, is the 
A. t roposphere . 
B . s t ra tosphere. 
C. mesosphe re . 
D . the rmosphere . 
Hint: Refer to F igure 15.2. 
12. 7 5 % of the wor ld ' s fresh water is stored in 
A. lakes . 
B. rivers and s t reams. 
C. caves . 
D. cont inental glaciers and ice sheets . 
13. The rmoha l ine circulat ion refers to 
A. convect ion in the lower a tmosphere . 
B. global oceanic circulat ion driven by differences in tempera ture and salinity (salt 
content ) . 
C. changes in the t rade winds that are thought to cause El Nino events . 
D. a global oceanic current driven by wind. 
Hint: Refer to F igure 15.3. 
14. T h e geochemica l cycle of ca lc ium is l inked to long- term cl imate change by the fact that 
A. weather ing of carbonate rocks removes carbon d ioxide from the a tmosphere and 
l i thosphere. 
B. ca lc ium is precipi ta ted as g y p s u m in evapori te deposi ts . 
C. photosynthes is precipi tates calcium. 
D. hea t re leased by the react ion of ca lc ium with bicarbonate ion warms the surface 
water of the oceans . 
1 78 PART II C H A P T E R 16 
• H o w does chemical weather ing w o r k ? 
Brief answer : Water, oxygen, acids, and physical weather ing facilitate chemical 
weather ing react ions that alter and break down minerals to form new minerals, oxides, 
and salts and release silica. 
• H o w does physical weather ing work? 
Brief answer: Physical weather ing breaks rocks into fragments. Processes that aid 
physical weather ing include chemical weather ing , frost wedging , and the growth 
of plant roots. 
• H o w do soils form as products of weather ing? 
Brief answer: Soils form in rock materials by chemical weather ing . Soil formation 
is influenced by the composi t ion of the rock, stability of the weather ing surface 
( topography), t ime, and most important , c l imate . Life processes and their by-products 
are also important factors in soil formation and soil type. 
• W h a t is mass wast ing? 
Brief answer: Mass wast ing, also called mass movement , is the down-s lope movement 
of rock material . 
• W h y do mass m o v e m e n t s occur? 
Brief answer: The three most important factors enhanc ing the potential for mass 
movement s are the s teepness of the slope, the nature of the rock making up the slope, 
and the water content of the slope material . 
• H o w can d a m a g e from mass m o v e m e n t s be min imized? 
Brief answer: Careful engineer ing and the restriction of land use can minimize the 
hazards associated with mass movements . 
When we try to pick up anything by itself, 
we find it entwined with everything else in the universe. 
— J O H N M U I R 
Learning Warm-Up 
Science and art are synergist ic; that is, each enhances the other. For example , many 
aspects of nature that we consider beautiful are the product of a wea ther ing process . 
Before lecture spend five minutes scanning the text photos for beautiful features 
and effects created by weather ing. As you enjoy the photos , you migh t ask yourself, 
" H o w did weather ing processes create the colors and shapes in this p h o t o ? " 
Vital Information from Other Chapters 
Review the Rock-Forming Minera ls section and Table 3.1 and the Sedimentary Rocks section 
and Figure 3.24 in Chapter 3. 
The composi t ion and internal fabric of rocks significantly influence the rock ' s strength 
and the potential for mass movement . Therefore, a review of the composi t ion and especially of 
the different kinds of fabrics (textures) of igneous, sedimentary, and metamorphic rocks will 
provide you with vital information for unders tanding the different c i rcumstances that cause 
mass movemen t s . Whi le reviewing the basic rock textures descr ibed in Chapters 4, 5, 6, and 
7, ask yourself wha t textures and deformation fabrics might contr ibute to a weaker rock 
and an enhanced potential for mass movement . 
Weathering, Erosion, and Mass Wasting: Interface Between Climate and Tectonics 1 79 
Previewing Tip 
It will be very helpful to work on the Pract ice Exerc ise 2 before going to lecture. 
Comple te the exercise and take i t to class wi th you. Your lecturer will probably show 
slides to he lp you unders tand the different k inds of mass wast ing. You will unders tand 
these differences better if you have worked on them before lecture. 
During Lecture 
As you take notes dur ing this lecture, be sure to get details on how weather ing works . O n e 
goal for lecture should be to leave class wi th good answers to the Chapter Preview quest ions . 
• Focus on unders tanding specific chemica l weather ing processes such as oxi-
dat ion and dissolut ion. Be sure to dist inguish clearly be tween the chemical 
processes (for example , dissolut ion, oxidat ion) and the physical processes (for 
example , frost wedg ing , exfoliation, etc) . 
• Focus on unders tanding Figure 16.12, which shows the two basic soil-forming 
processes , t ranslocat ion and transformation. 
• To avoid gett ing lost in detai ls , keep the big picture in mind. Chapter 16 tells 
the story of wha t causes mass wast ing. Mass wast ing is about classification, 
and your j o b is to unders tand the differences be tween the types of wast ing. Be 
sure to pay close attention to commen t s the lecturer may make about how each 
kind of mass wast ing differs from the others . H i n t : In general these differences 
will be about the steepness of the slope, the kind of rock in the slope being 
moved , and the water content of the s lope material . 
• You m a y not be familiar with the kinds of mass wast ing (rock avalanche, creep, 
earthflows, and so on) . To help you visualize this process , the lecturer may 
show slides of various kinds of mass wast ing. S o m e of the slides may be very 
dramatic (for example , pictures of landslides). Enjoy the drama and excitement! 
• If you comple t ed Pract ice Exerc ise 2 before class , you can refer to it as the 
lecturer talks about the different kinds of mass wast ing. 
After Lecture 
Review Notes 
The perfect t ime to review your notes is r ight after lecture. If you wait even one day mos t 
(80 percent) of wha t you heard will have d isappeared from memory . 
Check Your Notes: Have you. . . 
• clearly identified the important points? Example : You should have clear descriptions of 
each type of chemical and physical weather ing. 
• added visual mater ia l? Chunking mater ial is a good learning strategy. There are a lot 
of chemical and physical weather ing processes in Chapter 16. It may be useful to make 
a list of processes that you can look at as a group all in one place in your notebook. 
Use a two-co lumn format for this list, in which both chemical and physical weather 
processes are listed in one co lumn and details you need to r emember about each 
process are briefly described in a second column to the right. 
• added s imple sketches? Chapter 16 includes lots of mater ial that is best learned by 
visualization. Sketches will help you remember the key aspect of each kind of mass 
wast ing. H i n t : Your sketch need not be artistic to be useful. Sketch only the features 
you need to remember . Example : For a rock avalanche you could draw a steep slope 
(one l ine at 45° angle) with a pile of large b locks at the bo t tom to des ignate large 
masses of broken rock (see F igure 16.19). 
1 8 0 PART II C H A P T E R 16 
• added a compar i son chart that will he lp you mas ter the classification of different 
k inds of mass was t ing? Hint: See Exerc ise 2. 
• created a brief big picture overview of this lecture (using a sketch or written outline) 
showing how weather ing works? Suggest ion for Chap te r 16: Wr i te a brief summary 
of the most important points you have learned from this chapter that might influence 
your choice of future h o m e sites. 
Intensive Study Session 
Set priorit ies for s tudying this chapter. We r e c o m m e n d giving the highest priority to activities 
that involve answer ing quest ions . Pay part icular at tention to any exercises recommended by 
the instructor during lecture and answer those first . The instructor is a lso your best resource 
if you are wonder ing which material is mos t important . 
Answer ing quest ions whi le using your text and lecture notes as reference material is far 
more efficient than rereading chapters or g lancing over notes . As a lways , you have three 
sources from which to choose quest ions . 
• Pract ice Exercises and Review Quest ions . Be sure to do the exercises, as they 
will focus on the key information you need to learn in this chapter—namely, 
how weather ing works , how soils form, factors that enhance the potential for 
mass wast ing, and the classification of mass movements . 
• Text. A n s w e r Exercises 2, 4, 5, and 8. Also comple te Though t Quest ions 1, 2, 
4, 6, 9, and 10. 
• W e b Site S tudy Resources 
ht tp : / /www.whfreeman.com/unders tandingear th5e 
Do the Onl ine Review Exercises Soils, Rock Mass Movements and Unconsoli-
dated Mass Movement. The Geo logy in Pract ice exercises will al low you to 
apply what you learned about weather ing to unders tanding the beautiful for-
mat ions of Bryce Canyon Nat ional Park. There is also a Geo logy in Pract ice 
exercise on assessing potential hazards from mass wast ing. Comple t e the 
G r a d e d Onl ine Quiz and Onl ine Rev iew Quest ions . Pay part icular at tention 
to the explanat ions of the answers . 
The Chapte r 16 Interact ive Exerc ise Mineral Stability on the Web site will help you review 
the susceptibil i ty of c o m m o n minerals to chemical weather ing. Note that the susceptibility of 
c o m m o n silicate minerals to chemicalweather ing is closely related to their silicate crystal 
structure. Quartz , a f ramework silicate, is very stable on the Ear th ' s surface, whereas olivine, 
wi th an isolated silica tetrahedral crystal structure, is very suscept ible to chemica l weather-
ing. Refer to F igure 3.9. 
As you study the many different types of mass movemen t i l lustrated in the figures, assess 
wha t factors are mos t important in caus ing slope instability. R e m e m b e r that the three most 
important factors enhancing the potential for mass movemen t s are the s teepness of the slope, 
the nature of the rock material in the slope, and the water content of the s lope material . 
Man can live without gold, but not without salt. 
— F A L V I U S M A G N U S C A S S I O D O R U S 
A R O M A N P O L I T I C I A N O F T H E F I F T H C E N T U R Y A . D . 
Exam Prep 
Organizat ion is key to successful exam preparat ion. I t begins with note taking and t ime man-
agement . Start thinking now about how to organize your t ime for your next exam. Here are a 
few tips that should make your exam prep more efficient. 
Tips for Preparing for Exams 
• Use the clues the instructor provides in lecture about wha t is important . Even when 
a depar tment agrees on a c o m m o n core of material (rare), each instructor carves out a 
course that is unique and has a part icular character or flavor and distinct areas of 
emphas i s . The instructor is the ult imate guide to the quest ion "Wha t is impor tan t?" 
• Be sure you know the format of the exam. Mult iple choice? True- fa l se? Essay? 
Though t p rob lems? All of the above? 
• Review the notes marked TQ (test quest ion) . 
• Ask the instructor if exams are available from the previous semester. Review them 
to check the format of quest ions , to see what areas of content are stressed, and to see 
what types of p roblem solving are included. D o n ' t make the mistake of assuming that 
the same ques t ions will be asked this semester. 
• Be sure to at tend review sessions if they are offered. At tending a review session will 
raise your exam score. 
• If your class has tutors, preceptors, supplemental instruction leaders, or other peer 
helpers who have taken the class, ask for their suggestions about preparing for the exam. 
• Once you are clear about the nature of the exam, begin your review. Conduct 
the review in an orderly, systematic manner that ensures focused review of all the 
important mater ial . Be sure to take a look at the Eight-Day Study Plan in Appendix A. 
This plan is a great model for productive review. 
Materials in this section are part icularly useful dur ing your preparat ion for quizzes and 
examinations. T h e Chapter S u m m a r y and the Pract ice Exercises and Rev iew Quest ions 
will simplify your chapter review. Read the Chapter S u m m a r y to begin your session. It 
provides a helpful overview that will refresh your memory . 
Next, work on the Pract ice Exercises and Rev iew Quest ions . Comple te the exercises 
and quest ions jus t as you would on an exam, to see how well you have mastered this chapter. 
After you answer the ques t ions , score them. Finally, and most important , review each ques-
tion that you missed . Identify and correct the misconcept ion(s) that resulted in your answer-
ing the ques t ion incorrectly. 
Weathering, Erosion, and Mass Wasting: Interface Between Climate and Tectonics 181 
Figure 16.16. Landslide at Turnagain 
Heights, Anchorage, Alaska, triggered 
by the earthquake of 1964. This is a 
classic example of the role of liquefac-
tion in enhancing the potential for 
mass wasting. 
1 82 PART II C H A P T E R 16 
Chapter Summary 
What is weathering? 
• Physical weathering breaks rock into smaller pieces, and chemical weathering 
alters and dissolves the minerals in the rock. The principal factors that influence 
weathering are the composit ion of the parent rock, topography (stability of the 
land surface), and climate. There is a positive feedback between physical and 
chemical weathering, where one enhances the other if conditions are favorable. 
A good example of this positive feedback is soil formation. As physical and 
chemical weathering proceed to alter a stable surface of rock material, a soil 
forms. The formation of soil promotes weathering by increasing the availability 
of moisture and producing acidic chemical condit ions. Soils also promote the 
growth of plants, which aid both physical and chemical weathering. 
How does chemical weathering work? 
• H o w chemica l weather ing works is well illustrated by three examples . First, 
the chemical weather ing of feldspars, which are the mos t abundant silicate 
mineral in the Ear th ' s crust, i l lustrates how water with the he lp of carbonic 
acid can transform feldspars into clay minerals and dissolve silica and salts 
(cat ions). Refer to Figure 16.4. Second, the reaction of oxygen wi th the iron in 
fe r romagnes ium minerals like pyroxene illustrates oxidat ion. Refer to F igure 
16.5. Third, the reaction of calcite and other carbonate minera ls that m a k e up 
l imestone exemplifies the role naturally acidic water plays in d issolving rock. 
How does physical weathering work? 
• Physical weather ing involves a variety of processes that break rock into frag-
ments . Physical weather ing is p romoted by chemical weather ing , which weak-
ens grain boundar ies within the rock. Physical weather ing also p romotes 
chemical weather ing by increasing the surface area of the broken rock frag-
ments . Frost wedging , mineral crystall ization, and life processes play a major 
role in breaking rock apart. 
How do soils form as products of weathering? 
• Soils are a product of chemical weather ing of rock that has remained in p lace 
for a period of t ime. Soil formation is most affected by cl imate. The compos i -
tion of the parent rock, c l imate, topography, life processes , and t ime are also 
important factors in soil formation. Soil formation involves the t ransformation 
and translocation of materials . Refer to Figure 16.12. Soils , water, and the air 
we breathe are the three mos t basic natural resources . 
What is mass wasting? 
• M a s s movement s (also called mass wast ing) are sl ides, flows, or falls of large 
masses of rock material down slopes when the pull of gravity exceeds the 
strength of the slope mater ia ls . M a s s movement s can be t r iggered by earth-
quakes , absorpt ion of large quanti t ies of water from torrential rainfall, under-
cutt ing by flooding rivers, human activities, or other geologic processes . 
Why do mass movements occur? 
• T h e three mos t impor tan t factors inf luencing the potent ia l for mass m o v e -
ments are the s teepness of the s lope, the na ture of the rock m a k i n g up the 
Weathering, Erosion, and Mass Wasting: Interface Between Climate and Tectonics 1 83 
Table 16.4 Factors That Influence Mass Movements 
Nature of slope Steepness Stability 
material Water content of slope of slope 
U N C O N S O L I D A T E D dry angle of repose high 
Loose sand or sandy silt wet modera te 
Unconsolidated mixture of sand, dry modera te h igh 
silt, soil, and rock fragments wet low 
dry high 
we t steep low 
CONSOLIDATED 
Rock, jo in ted and deformed dry or we t modera te to steep modera te 
Rock, mass ive dry or wet modera te high 
dry or wet steep modera te 
s lope, and the wate r con ten t of the s lope mater ia l . See Table 16.4. A l though 
steep s lopes are p r o n e to mass m o v e m e n t s , s lopes of only a few degrees can 
also fail ca tas t rophica l ly because of these other factors . 
• Slopes become unstable when they become steeper than the angle of repose (the 
max imum slope angle that unconsolidated material will assume). Slopes in con-
solidated material may also become unstablewhen they are oversteepened or 
denuded of vegetation. Erosion by rivers and glaciers and human activities can 
oversteepen slopes and thereby increase the potential for mass movement . 
• The composi t ion , texture, and geologic structure of the slope mater ial is anoth-
er impor tan t factor influencing the potent ial for slope failure. For example , 
rocks with h igh clay content tend to be weak and m a y liquefy. Tilted layers of 
sedimentary or volcanic rocks are more likely to fail a long bedding planes 
when the bedding paral lels the slope. Fai lure of foliated metamorphic rocks is 
more likely to occur parallel to the direct ion of foliation. 
• Water absorbed by the slope mater ial contr ibutes to instabili ty in two ways : (1) 
by lowering internal friction (and thus resis tance to flow) and (2) by lubricat-
ing planes of weakness in the slope. 
How are mass movements classified? 
• Material that makes up the s lope, the way it moves , and the rate of movemen t 
are used to classified mass movemen t s . Refer to Figure 16.17 and the many 
other f igures that il lustrate types of mass movement . 
How can damage from mass movements be minimized? 
• The hazards and d a m a g e associated with mass movement s can be min imized 
by careful geological assessment , engineer ing, and land use policies that 
restrict deve lopment on unstable slopes. Of part icular impor tance is the avoid-
ance of s teepening or undercut t ing slopes and minimiz ing the amoun t of water 
that can infiltrate the slope mater ial . In some areas part icularly prone to mass 
movements , deve lopment m a y have to be restricted. 
Exercise 2: Inventory of the different kinds of mass wasting 
The authors discuss eight different kinds of mass wasting. As an aid to learning the circumstances 
that favor each one, use your textbook to complete the table. Textbook figures and figure captions 
will help you. 
H i n t : You probably haven ' t seen many of these features before, so be sure to examine 
the photos and figures of each type of mass wast ing in your textbook. If you are a visual learn-
er, this activity m a y be vital. Also , to get a kinesthet ic feel for these movemen t s , imagine 
yourself t rying to outrun each movement . Indicate in the space labeled " S p e e d " whether you 
could escape the mass movemen t by walking, running, or mov ing as fast as a speeding auto. 
1 8 4 PART II C H A P T E R 16 
Practice Exercises 
Answers and explanat ions are provided at the end of the Study Guide . 
Exercise 1: Physical and chemical weathering 
A n s w e r the quest ions in the flowchart. 
Weathering, Erosion, and Mass Wasting: Interface Between Climate and Tectonics 1 8 5 
Kind of mass 
wasting 
Composition of slope 
(consolidated vs. unconsolidated 
and wet vs. dry) Characteristics 
Rock avalanche Speed: Running or a speeding auto 
Slope angle: Steep slopes 
Triggering event(s): Earthquakes 
Notes : Occur in mountainous regions where rock 
is weakened by weathering, structural deformation, 
weak bedding, or cleavage planes 
Creep Speed: 
Slope angle: Any angle 
Triggering event(s): None 
Notes : 
Earthflows Speed: 
Slope angle: Any angle 
Triggering event(s): Intense rainfall 
Notes : Fluidlike movement 
Debris flow Speed: 
Slope angle: Any angle 
Triggering event(s): 
Notes : 
Mostly finer rock materials with some 
coarser rock debris with large amounts 
of water 
Speed: 
Slope angle: 
Triggering event(s): Intense rainfall or catastrophic 
melting of ice and snow by a volcanic eruption. 
Notes : Contains large amounts of water 
Debris avalanche Water-saturated soil and rock Speed: 
Slope angle: 
Triggering event(s): 
Notes : 
Slump Speed: Walking 
Slope angle: Any angle 
Triggering event(s): Rainfall 
Notes : 
Surface layers of soil Speed: Walking 
Slope angle: Any angle 
Triggering event(s): 
Notes : Occurs only in cold regions when water in the 
surface layers of the soil alternately freezes and 
thaws; water cannot seep into the ground because 
deeper layers are frozen. 
Exercise 3: Water's role in mass wasting 
Water enhances the potential for mass wast ing in many ways . Us ing your textbook as a guide, 
briefly descr ibe f ive different ways water enhances the potential for mass movemen t s . 
1. 
2. 
3. 
5. 
4. 
A. Discuss three factors that enhance the potent ia l for mass m o v e m e n t at the home-
site in the figure. 
1. 
2. 
2. 
B. Given that the house is already built on this site, briefly discuss two poss ible ways 
of reducing the risk of d a m a g e to the house due to slope failure. 
1. 
1 8 6 PART II C H A P T E R 16 
Weathering, Erosion, and Mass Wasting: Interface Between Climate and Tectonics 1 8 7 
2. 
Review Questions 
Answers and explanat ions are provided at the end of the Study Guide . 
1. Of the fol lowing agents , which is N O T involved in the process of chemical weather ing? 
A. water C. carbon dioxide 
B. oxygen D. ni trogen 
2 . T h e fol lowing products all result from chemical weather ing E X C E P T 
A. feldspar. C. silica in solution. 
B. iron oxides . D. clay minerals . 
3 . W h i c h of the fol lowing minerals does N O T chemical ly weather into a clay minera l? 
A. muscovi te C. pyroxene 
B. K-feldspar D. quartz 
4 . Of the fol lowing materials , which one would make the longest lasting tombstone? 
A. l imes tone 
B. shale 
C. grani te 
D. sands tone cemented with ca lc ium carbonate . 
5. An example of chemica l weather ing is 
A. rusty streaks on a rock wall . 
B. angular b locks of rock rubble in the mounta ins . 
C. potholes in pavement . 
D. rocks wedged apart by tree roots . 
6. A l though water is an important agent of chemical weather ing in its own right, it 
becomes more effective if small amounts of carbonic acid are present. Carbonic acid is 
formed when 
A. carbon from coal beds or from graphi te deposi ts is pulver ized along a fault or frac-
ture and then added to water. 
B. carbon dioxide from the a tmosphere or from organic decomposi t ion is added to 
water. 
C. sulfur from coal-fired power plants is added to water. 
D. water c o m e s in contact with the calcite in a l imestone layer. 
7 . The potent ial for chemical weather ing can be greatly enhanced by physical weather ing 
because phys ica l weather ing increases 
A. the surface area of the rock part icles. 
B. the availability of chemical agents . 
C. dra inage and thereby reduces contact with water. 
D. the size of the rock part icles. 
8. L imes tone and other carbonate rocks weather relatively fast in a cl imate due to 
A. dry / oxidat ion 
B. dry / hydrolysis 
C. we t / physical weather ing reaction 
D. wet / dissolut ion p romoted by carbonic acid 
9. Georgia soil, a long wi th that of other warm, humid regions, is deep red in color. This 
color is due to 
A. iron oxides . C. feldspar. 
B. quar tz . D. clay minerals . 
10. Clay minerals , like kaolinite, are a product of weather ing of minerals 
and are a raw material for . 
A. chemical / silicate / pottery 
B. physical / sulfate / cement 
C. chemical / sulfide / asphalt 
D. physical / carbonate / fertilizers 
Hint: Refer to Figure 16.4. 
11. Which of the following climatic regions experiences the most rapid chemical weathering? 
A. hot, low precipitat ion 
B. extremely cold, low precipitat ion 
C. hot, high precipi tat ion 
D. extremely cold, high precipitat ion 
12. Soil product ion is often descr ibed as a "posit ive feedback" process . W h y ? 
A. Carbon dioxide in ra inwater is used up by organisms, so weather ing of underlying 
rock is impeded. 
B. Rainwater becomes more acidic as i t percolates through the soil, so weathering of 
under lying rock is p romoted . 
C. O n c e a layer of soil is formed, the unde r ly ing rock isp ro tec ted from further 
wea the r ing . 
D. Plant growth reduces the potential for weather ing and therefore of soil development. 
13. Of the following minerals, the one most rapidly altered by chemical weathering would be 
A. mica (sheet silicate), such as bioti te. 
B. amphibole (double chain silicate), such as hornblende . 
C. pyroxene (single chain silicate), such as augite. 
D. isolated silica te trahedra mineral , such as olivine. 
Hint: Refer to Table 16.2. 
14. Acid rain the potential for chemical weather ing. 
A. neutral izes C. increases 
B. does not affect D. decreases 
Hint: Refer to pages 5 6 9 - 5 7 0 in Chapter 23 of the textbook. 
15. W h a t happens chemical ly to the quar tz sand grains in a ca lc i te-cemented sandstone that 
is undergoing modera te chemical weather ing? 
A. They combine with water. 
B . They dissolve. 
C. They oxidize. 
D. Virtually no th ing—they b e c o m e grains of quar tz sand. 
16. Rock material that tends to result in the most fertile soils is weathered. 
A. not at all 
B. very weakly 
C. modera te ly 
D. intensely 
17. Physical and chemica l weather ing in the warm, wet cl imates of the Ear th ' s surface alter 
exposed granite to 
A. quar tz and feldspar sand. 
B. olivine sand. 
C. iron-rich soil. 
D. quartz sand and clay. 
Figure 16.5. The general course of chemical reactions by which an 
iron-rich mineral, such as pyroxene, weathers in the presence of oxygen 
and water. 
1 88 PART II C H A P T E R 16 
A. site A 
B . s i t e B 
C . s i t e C 
D . s i t e D 
20. W h a t force drives mass was t ing? 
A. heat 
B . gravity 
C. friction 
D. convect ion 
2 1 . M a s s wast ing tends to occur when 
A. a s lope b e c o m e s steeper due to undercut t ing by a river or ocean waves . 
B. the mass on a slope decreases by draining water from the ground. 
C. friction is increased by draining water from the ground. 
D. friction is decreased by taking water out of the ground. 
22. Talus consis ts largely of 
A. clay and other very fine rock part icles. 
B. a mixture of powdered rock and ice. 
C. coarse , angular rock fragments . 
D. al ternate layers of sand, silt, and clay. 
23. The angle of repose is the 
A. angle at wh ich rock mater ial is mos t stable. 
B. angle at wh ich lava flows solidify wi thout spreading out. 
C. angle of a s lope that will no longer support large boulders and rock pillars. 
D. m a x i m u m slope at which loose material lies without cascading down. 
18. In the days of the pha raohs of Egyp t , a cher i shed status symbo l was the obel isk, a 
s tone c o l u m n decora ted wi th h ie rog lyphs (des igns carved into the s tone—usua l ly 
sands tone ) . In 1879 the obel i sk of T h o t h m e s III f rom the t emple of Hel iopol i s was 
m o v e d to Cent ra l Pa rk in N e w York City. Wi th in about sixty years the h ie rog lyphs 
w e r e bare ly vis ible on the obel isk, wh i l e its counterpar t still s tanding in E g y p t 
r e m a i n s in near ly perfect condi t ion in the deser t sun after a lmos t 4 ,000 years . W h y 
did the s tone obel i sk de ter iora te so quickly w h e n i t was m o v e d to N e w York Ci ty? 
H i n t : Refer to F igures 16 .1 , 16 .11 , and 23 .18 . 
19. W h i c h hil lside homes i te is the best long- term investment? 
Weathering, Erosion, and Mass Wasting: Interface Between Climate and Tectonics 1 89 
24. An impor tant factor in mass wast ing is the orientation of rock layers, foliation, or joint-
ing. For layered sedimentary and volcanic rocks , which condi t ion is the least stable? 
A. Rock layers are at r ight angles to the slope. 
B. Rock layers are parallel to the slope. 
C. Rock layers are horizontal to the slope. 
D. Rock layers stand vertical. 
Test-Taking Tip 
Time permit t ing, it is somet imes helpful to sketch the alternatives to a test quest ion. 
For example , i f you aren ' t sure about the answer to Review Quest ion 24 , then you could 
sketch rock layers at r ight angles to the s lope, rock layers parallel to the s lope, and so 
on. Sketching can be part icularly useful if you are a kinesthet ic learner, as the action 
of drawing may j o g or unlock your memory when you are stuck. 
25 . W h i c h of the following would be most subject to mass movemen t s (assuming slope and 
c l imate are the same in each case)? 
A. h igh-grade gneiss , with highly contor ted foliation 
B. quar tz -cemented sandstone, with layering perpendicular to the slope 
C. shale, with bedding parallel to the slope 
D. mass ive granite bedrock 
26. Solifluction usually occurs in 
A. cold regions. 
B. very cold regions like Antarct ica. 
C. any area where there is a lot of sunshine. 
D. tropical regions. 
27. Which of the following options is the most effective way to stabilize an active landslide? 
A. pi l ing addit ional rock and soil material on the landsl ide near its top 
B. saturating the landsl ide itself with water 
C. draining the water away from and out of the landsl ide area 
D. cutt ing away the toe (base) of the landsl ide 
28 . Roads through mounta inous regions tend to be unstable and require more maintenance 
if they are built on 
A. bedrock such as granite. 
B. horizontal lava flows. 
C. rock layers that dip perpendicular to the hi l ls lope. 
D. rock layers that dip parallel to the hi l ls lope. 
29 . Your beautifully landscaped house , built on an idyllic Georg ia hil lside site of small, 
irregularly undulat ing knolls and depress ions , with trees tilted at interest ing angles, has 
developed a bad case of broken and shifting foundation. The probable cause for the 
foundation p rob lem is 
A. mel t ing permafrost . 
B. that the house is built on an active earthflow. 
C. mudf low from an active nearby volcano. 
D. root wedging from the trees. 
30. Homeowner s in California whose houses survived recent wildfires are not quite out of 
the woods yet. With the approaching rainy season their next p rob lem will be 
A. increased potential for mudf lows and debris f lows. 
B. accelerated soil erosion. 
C. flash floods. 
D. all of the above. 
1 9 0 PART II C H A P T E R 16 
CHAPTER 17 
The Hydrologic Cycle 
and Groundwater 
Figure 17.2. The hydrologic cycle. 
Before Lecture 
Before you attend lecture, be sure to spend some time previewing the chapter. For an efficient pre-
view use the C h a p t e r P rev iew questions, a framework for understanding the chapter. Previewing 
works best if you do it just before lecture. With the main points in mind, you will understand the 
lecture better and take better notes. 
H o w much t ime should you devote to preview? Obviously, more t ime is bet ter than less. 
But even a brief (five- or ten-minute) preview session jus t before lecture begins will p roduce 
191 
a result you will notice. For a refresher on why previewing is important, see Part I, Chapter 3, j 
H o w to Be Successful in Geology. 
Chapter Preview 
• H o w does water m o v e around and in the Earth? 
Brief answer: The hydrologic cycle is a model for the movement of water on Earth. 
Refer to Figure 17.2. 
• H o w does water m o v e be low the ground surface? 
Brief answer: Porosity and permeabil i ty are the principle factors that control the 
infiltration and How of groundwater . (Skim the textbook section How Water Flows.) 
• W h a t factors govern our use of groundwater resources? 
Brief answer: Water, like soil and air, is a basic natural resource. S o m e of the 
mos t impor tant factors governing our ability to use g roundwater are the depth to 
the g roundwater table, springs and artesian sys tems, the ba lance be tween recharge 
and discharge, Darcy ' s law, and water quality. 
• W h a t geologic processes are affected by groundwater? 
Brief answer: Groundwate r is the geologic agent responsible for caves , karst 
topography, and