Planetary Geology

A Teacher’s Guide with Activities

in Physical and Earth Sciences

National Aeronautics and

Space Administration

Teachers and

Students

Educational Product

Grades 5-college
Planetary Geology—A Teacher’s Guide with

Activities in Physical and Earth Sciences is

available in electronic format through NASA

Spacelink—one of the Agency’s electronic

resources specifically developed for use by the

educational community.

The system may be accessed at the following

address: http://spacelink.nasa.gov
A ctivities in Planetary

Geology for the Physical

and Earth Sciences

Editors

Ronald Greeley and Kelly Bender Robert Pappalardo

Department of Geology Department of Geological Sciences

Arizona State University Brown University

Box 871404 Providence, Rhode Island 02912

Tempe, Arizona 85287-1404

Acknowledgments

This book is the second edition of NASA SP-179, first printed in 1982. It has

been updated to take into account planetary missions that have flown

throughout the solar system since the first edition. Both editions are outgrowths of various short courses in Planetary Geology that have been held

over the last two decades, and from activities developed in the classroom.

Activities in Planetary Geology was developed for the National Aeronautics

and Space Administration with the guidance, support, and cooperation of

many individuals and groups.

NASA Headquarters

Solar System Exploration Division

Office of Planetary Geoscience

Education Office

Production

Photographic Support Graphics Word Processing

Bill Knoche, ASU Sue Selkirk, ASU Carol Rempler, ASU

Daniel Ball, ASU Mary Milligan Byrnece Erwin, ASU

Kelly Bender, ASU
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Ms. Deana Cooper

Highland High School

Gilbert, AZ 85234

Mr. David Nelson

Department of Geology

Arizona State University

Tempe, AZ 85287

Dr. Robert Pappalardo

Department of Geological Sciences

Brown University

Providence, RI 02912

Mr. David Rood

2060 John Dodgen Way

Marietta, GA 30062

Prof. Peter H. Schultz

Department of Geological Sciences

Brown University

Providence, RI 02912

Ms. Kelly Bender

Department of Geology

Arizona State University

Tempe, AZ 85287

Dr. Richard D’Alli

Department of Psychiatry

Duke University Medical Center

Durham, NC 27706

Prof. Ronald Greeley

Department of Geology

Arizona State University

Tempe, AZ 85287

Ms. Lee Ann Henning

Fort Hunt High School

Fort Hunt, VA

Mr. William Johnson

Fairfax High School

3500 Old Lee Highway

Fairfax, VA 22030

Activity Contributors

Geologic Events

Unit 1 Unit 2 Unit 3 Unit 4 Unit 5

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17

Grade Level

K – 4

5 – 8

9 – 12

College

Aerial Photos

Stereo Photos

Impact Cratering

Compar. Cratering

Rainy Day Craters

Coriolis Effect

Storm Systems

Wind Tunnel

Landform Mapping

Mars Geology

Venus Geology

Outer Planet Sats.

Planets in Stereo

Intro. to Mapping

Moon Mapping

Mars Mapping

Form of Activity

Individual Student Activity

Group Student Activity

Instuctor Demonstration

Geologic Events

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Guide to Activity Level
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Table of Contents

Preface

Introduction

Special Note to the Instructor

A Note About Photographs

Unit One: Introduction to Geologic Processes

Exercise One: Geologic Events on Earth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Exercise Two: Geologic Landforms Seen on Aerial Photos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

Exercise Three: Geologic Landforms Seen on Stereoscopic Photos . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Unit Two: Introduction to Impact Cratering

Exercise Four: Impact Cratering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Exercise Five: Comparative Cratering Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .63

Exercise Six: Impact Cratering on a Rainy Day . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75

Unit Three: Introduction to Planetary Atmospheres

Exercise Seven: Coriolis Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87

Exercise Eight: Storm Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93

Exercise Nine: Aeolian Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103

Unit Four: Introduction to Planetary Surfaces

Exercise Ten: Landform Mapping: The Terrestrial Planets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115

Exercise Eleven: Geologic Features of Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127

Exercise Twelve: Geologic Features of Venus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137

Exercise Thirteen: Geologic Features of Outer Planet Satellites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149

Exercise Fourteen: Planets in Stereo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .167

Unit Five: Introduction to Planetary Geologic Mapping

Exercise Fifteen: Introduction to Photogeologic Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183

Exercise Sixteen: Photogeologic Mapping of the Moon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193

Exercise Seventeen: Photogeologic Mapping of Mars . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .215

Appendix

Glossary of Terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225

Planetary Geology Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229

Evaluation Return Card
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Introduction

Many earth science courses include an introduction to the solar system. The challengeof earth science is to understand the natural processes that shape not only our planet, Earth,

but all objects in the solar system. But there are

more compelling arguments for including planetary

science in the classroom. Those arguments, some of

which are outlined below, inspired NASA to conduct short courses in planetology for earth science

teachers at the secondary and college levels. This

book is an outgrowth of these short courses.

The Planetary Perspective

Few processes can be understood in isolation from

other natural phenomena. Planet Earth is no exception. The forces that drive Earth’s evolution and shape

its surface have most likely operated elsewhere in the

solar system. Earth scientists attempt to recognize

those forces on all planets and explain why they are

manifested on our world in ways that seem familiar,

and on other worlds in ways that may not.

Earth scientists are also concerned with earth

materials, the building blocks of this planet. If there is

one illuminating result of space exploration, it is the

emergence of a unifying vision of the birth and

growth of planets. Pictures of the planets sent back by

spacecraft strongly suggest a close relationship

among the inner planets. Rocks and soil brought back

from the Moon bear remarkable similarity to Earth

materials. Even spacecraft pictures of the outer planet

satellites, many of which are planets themselves by

virtue of their size, have astounded scientists with

their exotic, but recognizable surfaces.

The American geologist T. C. Chamberlain

(1843–1928) once wrote that when approaching a

scientific problem, it is important to maintain several working hypotheses. Prior to manned and

unmanned space travel there were only terrestrial

examples of planet-making materials and processes.

It is now possible to devise general theories from a

collection of working hypotheses. The multiple

working hypotheses come from the scenes of

extraterrestrial environments.

A major goal of science is prediction. Once generalized theories are formulated, then experiments are

designed to test the theories through their predictions.

Some experiments that could address the questions of

earth scientists simply cannot be performed on Earth

because of their monumental proportions. What could

be more illustrative, elegant, or challenging than to

consider the other planets as great experiments running under conditions different from those on Earth?

The result is to gain insight into planetary scale problems and to escape the limited Earthbound view of

nature.

Earth scientists are painfully aware that the

processes active on Earth today have wiped clean

much of the record of Earth’s own history. However,

relics and indirect evidence of our own past are

often preserved on other planetary surfaces. A common tactic used by scientists to understand complex

systems is to study simpler, analogous systems.

While the Earth is a complex, turbulent, and delicately balanced system, the other planets may represent stages in the evolution of that system that

have been arrested in their development or ventured down different pathways.

Finally, the study of the Earth and planets on a

grand scale is not without practical benefits. Better

analysis of the atmosphere, sea, and solid crust

proves to be of technological, economic, and cultural value. But meteorologists have observed Earth's

weather since Ben Franklin’s day; what has been

missing is another model, another atmosphere to

study, where the variables are different, but the

dynamics are as definitive. We may have found

those requirements in the atmospheres of Venus,

Mars, and the outer planets.

Apollo 17 was launched December 7, 1972. Here astronaut Harrison Schmitt works with a lunar scoop in the

Moon’s Taurus-Littrow mountains.
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

We are living in a time of revolutionary discoveries in earth science. It is possible that the fundamental work in earth and planetary sciences over the last

three decades will someday be likened to Galileo

turning the first telescope toward the heavens. From

a scientific standpoint, earth science is a special case

of the more general planetary or solar system sciences. This is the motivation to study other

worlds—to learn more about that celestial neighborhood in which we occupy a small, but life-sustaining place.

About This Book

Science education is an integral part of scientific

endeavors. When the National Aeronautics and Space

Administration was created by an act of Congress in

1958, its charter required the agency to “...provide for

the widest practicable and appropriate dissemination

of information concerning its activities and the results

thereof.” Part of that responsibility includes introducing students to the scientific results of planetary exploration. This volume is designed to help meet this goal.

The activities are written either to supplement or to

introduce topics usually encountered in earth science

courses. Consistent with the rationale outlined above,

most activities deal with new concepts in planetary

geology, but, when generalized to include terrestrial

processes, can illustrate broad problems in the earth

sciences. The exercises are not keyed to any particular

text; rather, each addresses concepts as independent

units. The exercises are grouped into five units: 1)

introduction to geologic processes, 2) impact cratering

activities, 3) planetary atmospheres, 4) planetary surfaces, and 5) geologic mapping. Although each exercise is intended to “stand alone,” students will benefit

from having worked some of the prior exercises. For

example, it would be difficult for students to work

exercises in planetary geologic mapping without some

knowledge of geologic processes and planetary surfaces. The suggested introductory exercises are noted

at the beginning of each exercise. Depending on the

level of the student and the context of the exercise, the

sequence of the units is somewhat cumulative.

Depending on the instructor, activities can be

adapted to most levels of instruction by modifying the

questions and adjusting the expectations for answers.

A list of suggested correlations of activities with topics

commonly covered in earth science courses is included for the convenience of the instructor.

Special Note to the Instructor

Each activity includes an introduction with

instructor's notes, a “blank” exercise sheet which

can be copied for classroom use, and an answer key

to the exercise.

This publication is in the public domain and is

not protected by copyright. Permission is not

required for duplication.

It is our hope that this book will be a valuable

resource in teaching the physical, earth, and space sciences. Enclosed is an evaluation card. We would appreciate your returning this card with your comments.

A Note About Photographs

An essential part of Planetary Geology is the use

of spacecraft photographs. Ideally each studentteam should have access to glossy photographic

prints for use during the laboratory exercises.

Photocopies of the pictures in this book (such as

Xerox copies) generally lack sufficient detail to be

useful. Offset printing is slightly better, but again

this process is at least three generations removed

from the original product.

Glossy prints or copy negatives can be obtained

for a nominal cost (in some cases for no charge)

from various sources. Each spacecraft photograph

caption in this book contains the necessary picture

identification numbers to help you in obtaining the

photos. Usually the mission name (Apollo, Viking,

etc.) and frame number is sufficient identification.

Listed below are sources of space photography.

Instructions for ordering photography will be provided upon written request. Be sure to include your

name, title, the fact that the photographs will be

used at a non-profit educational institution, and

specific photograph numbers.

For planetary mission photography, contact:

National Space Science Data Center

Code 633

Goddard Space Flight Center

Greenbelt, MD 20771

For Earth photography, contact:

EROS Data Center

U.S. Geological Survey

Sioux Falls, SD 57198

For photographs indicating Arizona State

University as their source, contact:

Arizona State University

Space Photography Laboratory

Department of Geology

Box 871404

Tempe, AZ 85287
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Of the terrestrial planets, the Earth is the most

complex and diverse. Because we live on this

planet, we have the opportunity to study the

geologic processes that have formed and continue to

shape its surface. The four main geologic processes

that act on the Earth’s surface are volcanism, tectonism, gradation, and impact cratering.

Volcanism is the eruption of molten material onto

the surface. On the terrestrial planets, the molten

material (or magma) is composed of melted rock

and gases. On icy satellites the material is predominantly liquid water or slushy ice, with some fraction

of rocky material. Tectonism involves the movement of rock by folding, fracturing, or faulting.

Earthquakes are a manifestation of tectonism.

Volcanism and tectonism are processes driven by

internal planetary activity. Gradation involves the

erosion, movement, and deposition of surface materials. The major agents of gradation are running

water, ice, gravity, and wind. Gradation is controlled by the surface environment of a planet or

satellite. Factors controlling surface environment

include gravity, temperature, and the presence of an

atmosphere. Material falling from space such as

meteoroids and comets result in impact cratering,

the fourth principal geologic process.

By recognizing the morphologies (shapes) of

landforms produced by each of these four processes, it is possible to begin to unravel the history of a

planetary surface. Planets and satellites have different geologic histories, with each of the processes

playing a part. However, the extent to which any

process has operated on a surface varies from planet to planet. The exercises in this unit are designed

to introduce the student to the landforms produced

by each process. Today, impact cratering (emphasized in Unit Two) is relatively rare in the solar system, but historically it has played a major role in

shaping planetary surfaces and in the formation of

features now seen.

Unit One

Introduction to

Geologic Processes
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Purpose

The objective of this exercise is to show the frequency and distribution of events on Earth resulting from the four major geologic processes. In this

exercise, the student will process and analyze a

geologic data set to produce graphic and written

results. Locating event sites will improve world

geography skills.

Materials

Suggested: magazines and newspapers, glue or

tape, paper, colored pens or pencils, straightedge or

ruler, atlas or world almanac (one atlas per student

group). Substitutions: wall-size world map can substitute for an atlas.

Background

This exercise illustrates the general frequency

and distribution of volcanic, tectonic, gradational,

and impact cratering events. It is important that students have an introduction to these processes

through lectures, videos, or slides before working

the assignment. Volcanic and tectonic events (volcanic eruptions and earthquakes) are typically large

in scale and short in duration. That is, each event

often results in great disruption over a large area,

but last only a short time. However, over long periods of time, these processes can produce large landforms such as mountains, plains, ocean basins and

islands. Impact cratering is of short duration and

the frequency of impacts is very low compared to a

human lifespan. Early in Earth’s history, impact cratering was much more common, but now there are

fewer objects in space to act as impactors. Gradation

occurs at all scales from the erosion of mountain

ranges to the grinding of sand grains in streams.

Gradation on Earth occurs on time scales from seconds to centuries or more.

Teacher Recommendations

Part One of the exercise requires the student to

collect data in the form of pictures and newspaper

articles. This part can be done in several ways: it can

be assigned as a take-home exercise, the instructor

can collect magazines and newspapers to enable

completing the exercise during a single class period,

students can use a library (make photocopies

instead of cutting up papers), or it can be omitted.

Finding pictures that illustrate landforms created by

all four processes can be frustrating. Many magazine advertisments with landscapes as the background will be useful. Make sure only one representation of an individual event is used; for example, a major earthquake will get extensive coverage

by the media—but only one picture of that earthquake's effects should be used. Encourage the students to explain the types of landforms they select

and help them classify the formation processes.

Impact cratering occurs so infrequently that it is

unlikely to be represented in magazines; however,

pictures of the Moon show craters and it is up to the

instructor to decide if such pictures can be used. It is

recommended that the exercise be limited to the

Earth. Suggested modifications of Part One for different grade levels are as follows:

Grades K–4: Eliminate procedure B; use

procedure D and questions

1, 2, 5, and 6 for class discussion.

Work in groups, completing the

exercise in class.

Exercise

One

Geologic Events

on Earth

Instructor Notes

Suggested Correlation of Topics

The Earth, geography, gradation, impact

cratering, earth science introduction,

tectonism, volcanism

2.0 hours each part

(with instructor

modification for grade

level)

Exercise One: Geologic Events on Earth
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Grades 5–8: Retain or eliminate procedure B

at instructor's discretion; modify

procedure D to the writing level

of the students; use questions 5

and 6 for class discussion. Work

in groups, completing the exercise in class.

Grades 9–12: Use exercise with no modifications. Work individually, in

class or as homework.

College: Increase the number of pictures

and articles needed. Have students compile a list of all the

surface features produced by

each process and then apply the

lists to the region in which they

live (i.e., list the volcanic, tectonic, gradational, and any

impact features in the local geographic area). Photos of these

features can be added to the

scrapbook. Work individually,

in class or as homework.

Lengthen the time span of exercise (collect articles over a period of a month or more) as

appropriate.

The second part of the exercise requires the student to analyze a data set and produce a graph of

the results. In addition, the student is required to

use geography skills to plot the location of the

geologic events. To classify the list according to

process, note that earthquakes are tectonic events;

eruptions of ash and lava are volcanic events; landslides, mudslides, avalanches, flooding, hurricanes,

and the formation of sinkholes are gradational

events. The meteorite fall is the only impact event

listed. The locations listed are general, so encourage

the students not to spend too much time in finding

the exact location when plotting the event on the

world map. For example, if the listing is Sumatra,

Indonesia, then anywhere on that island will do.

Question 3, which follows the plotting portion of the

exercise, can be used to lead into a discussion about

plate tectonics after noticing the distribution of

events around the Pacific (the “Ring-of-Fire”). For all

grade levels discussion is suggested following the

exercise.

Suggested modifications of Part Two for different

grade levels are as follows:

Grades K–4: Do procedures A, B, and C

using only the North American

entries. Use questions 1 and 2

for class discussion. Work in

groups completing the exercise

in class. The instructor will

need to teach how to make a

bar graph and help with geographic skills. Instead of the

world map provided, use a U.S.

wall map and mark it with

adhesive dots.

Grades 5–8: Do procedures A, B, and C

using a limited number of

regions from the list. Eliminate

questions 3 and 4. Work in

groups completing the exercise

in class.

Grades 9–12: Use exercise with no modifications. Work individually, in

class or as homework.

College: Expand question 3 by providing students with a map showing the lithospheric plates of

the Earth. Discuss which

processes are found mainly at

plate boundaries, and have students try to explain any exceptions. Work individually, in

class or as homework. If you

have access to the Internet, then

the exercise can be done using

up-to-date events, and can be

used over the course of a month

(the minimum suggested interval) or a year.

Science Standards

■ Earth and Space Science

• Structure of the Earth system

• Earth’s history

• Changes in Earth and sky

• Origin and evolution of the Earth system

■ Physical Science

• Interactions of energy and matter

Mathematics Standards

■ Statistics

■ Measurement

Exercise One: Geologic Events on Earth
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Part One

1. (Answers will vary.) Volcanism, tectonism,

gradation.

2. (Answers will vary.) Impact cratering.

3. (Answers will vary.) Tectonism, gradation,

volcanism.

4. (Answers will vary.) Impact cratering.

5. Answers will vary, but should indicate tectonism and gradation occur more often than volcanism and impact cratering (which is very

rare).

6. a. Answers will vary, however, volcanoes

tends to form large features over a short

period of time.

b. Answers will vary, however, gradation can

level mountains and fill in large bodies of

water over the course of millions of years.

c. Answers will vary. Location of population

centers in relation to known areas of volcanism and tectonism and the ability to

predict activity due to these processes will

control their impact on society (which can

be great over a short time period, or have

no effect during centuries of dormancy).

Large gradational events, such as floods,

can do as much damage to property and

cause as much loss of life as large earthquakes or volcanic eruptions.

Part Two

North America: B. 6 tectonic, 8 gradation,

4 volcanic, 1 impact.

South America: B. 6 tectonic, 4 gradation,

3 volcanic, 0 impact.

Europe: B. 1 tectonic, 1 gradation,

0 volcanic, 0 impact.

Africa: B. 2 tectonic, 1 gradation,

0 volcanic, 0 impact.

Asia: B. 9 tectonic, 6 gradation,

4 volcanic, 0 impact.

Antarctica: B. 1 tectonic, 0 gradation,

0 volcanic, 0 impact.

Australia: B. 6 tectonic, 0 gradation,

1 volcanic, 0 impact.

Atlantic Islands: B. 8 tectonic, 0 gradation, 

0 volcanic, 0 impact.

Pacific Islands: B. 28 tectonic, 3 gradation, 8 volcanic,

0 impact.

Complete data set: B. 67 tectonic, 23 gradation, 20 volcanic,

1 impact.

1. Tectonism.

2. Impact cratering. Not many objects in space act

as meteorites, most burn up in the atmosphere

before impact, many land in the oceans.

3. Volcanism and most tectonic events border the

Pacific Ocean (the “Ring-of-Fire,” related to

plate tectonics). Most tectonic events are related to plate boundaries, but due to the limited

numbers, will appear to be randomly distributed except for those in the Pacific. Gradation

events are randomly located. With only one

event it cannot be determined from the data,

but impact cratering is also random.

4. Gradation. No. On the Earth, water and wind

work to physically and chemically break up the

surface and then move the materials to new

locations for deposition. Lacking wind, water,

and ice, gradation on the Moon occurs by physically breaking up the surface during impacting

events. The surface materials are only transported if they are thrown out by an impacting

event.

Answer Key

Exercise One: Geologic Events on Earth
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Purpose

To learn about the frequency and distribution of

events on Earth that result from geologic processes:

volcanism, tectonism, gradation and impact cratering. In addition, you will learn to recognize the

landforms produced by these processes.

Materials: Part One

Magazines and newspapers; glue or tape; paper.

Introduction

Volcanism is the eruption of melted rock (called

magma) and its associated gases onto the surface of

the Earth. Volcanism commonly produces volcanoes

and volcanic flows. Tectonism involves the movement

of rock by fracturing and faulting, which results in

earthquakes. Gradation involves the erosion, transportation, and deposition of surface materials. On

Earth, water, wind, gravity and ice are the major

agents of gradation. Impact cratering occurs when

material from outside the Earth’s atmosphere (meteoroids, comets) strike the surface.

Procedure

A. Cut out magazine pictures illustrating each of the

four processes: volcanism, tectonism, gradation,

impact cratering. Try to find at least two pictures

showing landforms produced by each process.

B. Go through recent newspapers and collect articles

describing activities related to the four geologic

processes.

C. Put the pictures and articles together in a “scrapbook,” with one process per section (e.g., the volcanic pictures and articles together on a page or

two).

D. Study the pictures and write short descriptions of

the surface features produced by each process.

Name

Exercise

One

Geologic Events

on Earth

Questions

1. For which process(es) was it easiest to find pictures of the resulting landforms?

2. For which process(es) was it most difficult to find pictures of its resulting landforms?

3. Which process(es) was it easy to find articles about in the newspaper?

4. Which process(es) was it difficult to find articles about in the newspaper?

Exercise One: Geologic Events on Earth
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Materials: Part Two

Atlas or World Almanac; colored pens or pencils;

straightedge or ruler

Procedure

A. The list on the following pages documents the

major geologic events recorded on Earth from

August 1992 to July 1993. Fill in the blank to

indicate whether the event is related to volcanism (V), tectonism (T), gradation (G), or impact

cratering (I).

B. Count the total number of events of each type.

Using your straightedge, make a bar chart to

illustrate the results.

C. On the world map provided (Figure 1.1), mark

with a dot the location of each event listed.

Color code each dot by process (red for volcanic, blue for gradation, green for tectonic, and

black for impact events).

Questions

1. Over the given year, which process occurred most frequently?

2. Which process occurred least? List some reasons why you think this process does not happen more often.

3. Examine the world map you completed. Do the events appear to be randomly distributed on Earth?

Describe the distribution of events for each process as illustrated by your map.

4. The Moon has no atmosphere or water. On Earth, which process uses these agents? Can this process

occur on the Moon in the same way it does on Earth? Why or why not?

5. Based on the number of pictures and articles you found for each process, what can you say about the

frequency of activity for each process (how often does each occur)?

6. a. In your opinion, which process has the greatest effect on the surface (in terms of changing the appearance of the surface) over a short time period? 

b. Which has the greatest effect over a long time period (thousands of years or more)?

c. Which process has the greatest effect on society?

Exercise One: Geologic Events on Earth
_____ 09/11/92 earthquake, near Kinshasa, Zaire

_____ 10/12/92 earthquake, Cairo, Egypt

_____ 04/22/93 rains cause flooding in the

Sudan

_____ 10/23/92 earthquake, Caucasus

Mountains, Georgia

_____ 01/27/93 snow avalanche, Ossetia, Russia

_____ 10/17/92 earthquake, northern Colombia

_____ 10/18/92 earthquake, northern Colombia

_____ 11/28/92 earthquake, Pacific Ocean off

coast of Chile

_____ 12/07/92 rain causes mudslide in Llipi,

Bolivia

_____ 01/14/93 Galeras Volcano erupts, southern Colombia

_____ 02/24/93 earthquake, Chile-Argentina

border

_____ 03/11/93 rains cause major avalanche,

Andes Mountains, Peru

_____ 03/29/93 landslide, southern Ecuador

_____ 04/18/93 earthquake, Andes Mountains,

central Peru

_____ 04/20/93 Lascar Volcano erupts lava,

northern Chile

_____ 05/09/93 rains cause landslide, southern

Ecuador

_____ 06/07/93 Galeras Volcano erupts ash,

Colombia

_____ 07/11/93 earthquake, central Chile

9

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

_____ 08/07/92 earthquake, Gulf of Alaska

_____ 08/19/92 Mount Spurr erupts ash near

Anchorage, Alaska

_____ 08/24/92 hurricane Andrew hits Florida,

winds up to 200 mph

_____ 09/01/92 earthquake, near Nicaragua in

the Pacific Ocean

_____ 09/02/92 earthquake, in St. George, Utah

_____ 09/02/92 earthslides destroy homes in St.

George, Utah

_____ 09/16/92 Mount Spurr erupts ash near

Anchorage, Alaska

_____ 09/30/92 earthquake near the Aleutian

Islands, Alaska

_____ 10/09/92 27 lb. meteorite impacts car,

Peekskill, New York

_____ 12/11/92 storm causes flooding in New

Jersey and Long Island

_____ 12/30/92 snow avalanche, Utah

_____ 01/18/93 wet soil causes homes in

California to slip downhill

_____ 03/07/93 sinkhole in Florida destroy part

of a street

_____ 03/24/93 flooding, West Virginia

_____ 05/13/93 earthquake, Gulf of Alaska

_____ 05/15/93 earthquake, southern Mexico

_____ 06/25/93 flooding occurs along the

Mississippi and Missouri Rivers

_____ 07/31/93 Sequam erupts ash and lava,

Aluetian Islands, Alaska

_____ 07/31/93 Veniamin erupts ash and lava,

Alaskan Peninsula, near Aluetians

Major Recorded Geologic Events on Earth, August 1992–July 1993

North America

South America

Europe

Africa

Exercise One: Geologic Events on Earth
_____ 08/28/92 earthquake, north of Ascension

Island in the South Atlantic

_____ 11/21/92 earthquake, South Sandwich

Islands, South Atlantic

_____ 01/10/93 earthquake, South Sandwich

Islands, South Atlantic

_____ 03/09/93 earthquake, South Sandwich

Islands, South Atlantic

_____ 03/10/93 earthquake, South Sandwich

Islands, South Atlantic

_____ 03/20/93 earthquake, South Sandwich

Islands, South Atlantic

_____ 04/05/93 earthquake, South Sandwich

Islands, South Atlantic

_____ 05/02/93 earthquake, South Sandwich

Islands, South Atlantic

_____ 10/23/92 earthquake, Papua New Guinea

_____ 11/01/92 earthquake, Papua New Guinea

_____ 12/18/92 earthquake, Papua New Guinea

_____ 01/13/93 earthquake, Indian Ocean south

of Australia

_____ 03/06/93 earthquake, Solomon Islands,

South Pacific

_____ 03/09/93 earthquake, Macquarie Island,

Indian Ocean

_____ 07/16/93 Manam Volcano erupts ash and

lava, Papua New Guinea

_____ 11/04/92 earthquake, Balleny Islands,

Antarctica 

_____ 08/19/92 earthquake, central Kyrgyzstan

_____ 09/14/92 Indus River floods in Pakistan

_____ 11/06/92 earthquake, Aegean Sea, near

Turkey

_____ 12/08/92 earthquake, Nicobar Islands,

Indian Ocean

_____ 01/15/93 earthquake, Hokkaido, Japan

_____ 01/18/93 snow avalanche, Ankara, Turkey

_____ 01/19/93 earthquake, Sea of Japan

_____ 02/07/93 earthquake, Noto Point, Japan

_____ 02/21/93 snow avalanche, northern Iran

_____ 03/20/93 earthquake, Tibet

_____ 04/22/93 Sheveluch Volcano erupts ash,

Kamchatka Peninsula, Russia

_____ 04/29/93 rains cause mudslides near

Tokyo, Japan

_____ 06/08/93 earthquake, Kamchatka

Peninsula, Russia

_____ 06/23/93 Mount Unzen Volcano erupts,

Japan

_____ 07/04/93 Klyuchevskoy Volcano erupts,

Kamchatka Peninsula, Russia

_____ 07/12/93 earthquake, Japan

_____ 07/14/93 extensive flooding, Punjab,

Pakistan

_____ 07/15/93 Klyuchevskoy Volcano erupts

lava Kamchatka Peninsula, Russia

_____ 07/27/93 extensive flooding, southern

China

10

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Asia

Antarctica

Australia

Atlantic Islands

Exercise One: Geologic Events on Earth
_____ 08/02/92 earthquake, Halmahera,

Indonesia

_____ 08/02/92 earthquake, Flores Sea,

Indonesia

_____ 08/19/92 Mount Pinatubo erupts ash,

Philippines

_____ 08/28/92 rain causes avalanches on

Mount Pinatubo, Philippines

_____ 08/28/92 Mount Pinatubo erupts lava,

forming dome in its crater

_____ 09/11/92 Hurricane Iniki hits Hawaii,

winds up to 160 mph

_____ 09/26/92 earthquake, Halmahera,

Indonesia

_____ 10/11/92 earthquake, Vanatu Islands,

South Pacific

_____ 10/15/92 earthquake, Vanatu Islands,

South Pacific

_____ 10/17/92 earthquake, Vanatu Islands,

South Pacific

_____ 10/22/92 earthquake, Kermadec Islands,

South Pacific

_____ 11/04/92 earthquake, Vanatu Islands,

South Pacific

_____ 11/08/92 earthquake, Fiji Islands, South

Pacific

_____ 12/12/92 earthquake, Flores, Indonesia

_____ 12/20/92 earthquake, Banda Sea, north of

Australia

_____ 12/31/92 earthquake, Kermadec Islands,

South Pacific

_____ 01/04/93 earthquake, Tonga Islands,

South Pacific

_____ 01/20/93 earthquake, Sumatra, Indonesia

_____ 01/20/93 earthquake, Banda Sea, near

Indonesia

_____ 02/02/93 Mount Mayon erupts ash and

lava, Philippines

_____ 02/13/93 earthquake, near Fiji, South

Pacific

_____ 03/01/93 earthquake, Irian Jaya, New

Guinea

_____ 03/01/93 Mount Mayon erupts ash and

hot rock, Philippines

_____ 03/03/93 Mount Mayon erupts ash,

Philippines

_____ 03/03/93 rains on Mount Mayon cause

lahars (hot mudslides), Philippines

_____ 03/06/93 earthquake, Fiji, South Pacific

_____ 03/12/93 earthquake, Fiji, South Pacific

_____ 03/21/93 Mount Mayon erupts ash,

Philippines

_____ 03/21/93 earthquake, Fiji, South Pacific

_____ 03/24/93 Mount Mayon erupts ash,

Philippines

_____ 03/26/93 Mount Mayon erupts ash and

lava, Philippines

_____ 04/17/93 earthquake, Fiji, South Pacific

_____ 04/20/93 earthquake, northeastern

Indonesia

_____ 05/11/93 earthquake, Mindanao,

Philippines

_____ 05/16/93 earthquake, Tonga Islands,

South Pacific

_____ 05/18/93 earthquake, Pacific Ocean, near

the Philippines

_____ 06/06/93 earthquake, Mariana Islands,

North Pacific

_____ 06/18/93 earthquake, Kermadec Islands,

South Pacific

_____ 06/30/93 earthquake, Vanuatu Islands,

South Pacific

(Source: Geochronicle, Earth Magazine 01/93, 03/93,

05/93, 07/93, 09/93, 11/93, 01/94)

11

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Pacific Islands

Exercise One: Geologic Events on Earth
12

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ Figure 1.1 Map of the Earth to be used for plotting locations of geologic events. Use the following scheme: red dots for volcanic, blue dots for gradational, green dots for tectonic, and black dots for impact events.

0° 180°E0° 180°E 165° W

0° 0°

60°S30°S

30°N75°

165

N

° W 75°W 75°E

75°N60°S

Exercise One: Geologic Events on Earth
Purpose

The objective of this exercise is to introduce students to landforms produced by the four major geologic processes using aerial photographs.

Materials

Ruler (metric)

Background

Geologic processes often result in distinctive

landforms or surface features. For example, steep,

conical hills with small summit craters are distinctive as volcanic in origin. Aerial photographs, commonly taken from airplanes, are used to study landforms on Earth. Depending on the camera used and

the height of the airplane, areas shown in the photograph can range in size from a city block to an

entire city. Aerial photographs are either “vertical”

(viewed straight down on terrain from above) or

“oblique” (viewed to the side).

In this exercise, students will study a series of

aerial photographs of different terrains on Earth. In

answering questions about the areas, they will

become acquainted with landforms resulting from

the four major geologic processes. Students should

be introduced to these processes (gradation,

impact cratering, tectonism, and volcanism) before

beginning this exercise. A very brief statement

about the four geologic processes is provided in

the student section. Questions 2 and 6 require

student knowledge of simple trigonometry.

Exercise

Two

Geologic Landforms

Seen on Aerial Photos

Instructor Notes

Suggested Correlation of Topics

Geomorphology, gradation, impact cratering,

tectonism, volcanism, photography

13

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Two: Geologic Landforms

Seen on Aerial Photos

1.5 hours

200 m

N

A
14

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

1. a. The volcano has a circular base and a circular crater. The sides of the cone are gullied 

from erosion. 

b. A road. 

2. a. ~564 m.

b. 30.6°.

3. a. They are somewhat rugged.

b. The source of the lava is probably at the

base of the cinder cone near the road. 

4. a. They are both generally conical in shape,

with a central depression at the top.

b. Mt. Tavurur is much larger, and its crater is

more irregular.

5. The crater is scalloped, suggesting that it has

been reshaped several times by multiple eruptions.

6. x=~446 m, 27.7°.

7. The slopes of a volcano may be affected by the

following: Single versus multiple eruptions,

type of material (ash versus lava), viscosity

(“runnyness”) of the lava (dependent on its

temperature and composition), length of lava

flows, erosion by wind or rain after volcano is

formed.

8. It cuts through the mountains and is expressed

as a depression or trough. The rocks along the

fault were ground together and weakened, so

that they were more easily eroded than the

rocks away from the fault.

9. a. A road would have been cut and separated.

b. There are at least two off-set features

(drainage valleys) along the fault: near the

middle of the photo, and near the bottom of

the photo (harder to see the offset) .

10. Blocks A and C must move apart in the horizontal plane ( ). The area is undergoing

extensional stresses.

11. a. The alluvium is material eroded from the

mountains. 

b. All three erosional agents have acted to

produce materials eroded from the mountains, but water was the main agent.

c. All three agents, but mostly water.

d. It would be eroded by the agents of wind,

water, and gravity. For example, sand dunes

are visible alongside the fans, evidence of

erosion by the wind. 

12. a. It removes material from its banks, and carries material from one place to another. It

deposits material to form sandbars (erosion,

transportation, deposition). 

b. The channels change position with time.

Dry and semi-dry (ponds present) channels

are visible in the foreground of the photo.

13. a. It is roughly circular, with squared sides.

b. The walls are gullied, indicating erosion by

running water. The flat bottom suggests it

has been infilled.

14. About 48 times. (Crater diameter is about

1200 m.)

15. a. Meteor Crater is much wider and the sides

are not as steep. Impact craters excavate

(occur at ground level and dig out below

ground level), volcanic cones and craters

are built up above ground level (positive

relief features). 

b. They have the same circular shape and

have a crater in the center.

16. a. Circular. Somewhat subdued appearance:

the rim appears worn, and not very distinct.

The center of the crater seems to have been

partly filled in with sediment and sand

dunes.

b. Meteor Crater appears to be more distinct

and deeper than Roter Kamm.

17. a. The crater is much wider and not nearly as

high or steep. 

b. They are both very circular and have raised

rims.

18. a. River valley—gradation

b. Graben—tectonism (rivers are flowing into

this graben)

c. Lava flow—volcanism

d. Cinder cone—volcanism

e. Lava flow—volcanism

f. Lava flow in a pre-existing river valley—

gradation, followed by volcanism

Answer Key

Exercise Two: Geologic Landforms

Seen on Aerial Photos
15

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

g. Graben—tectonism (lava flows have

entered parts of this graben)

19. Near letter G, volcanic material flowed into the

pre-existing graben valley in two separate

places. The flow spread out in a fan shape.

20. _3_ River and stream valleys formed 

_5_ dark (black) volcanic materials were

deposited

_4_ medium gray volcanic flows were deposited

_1_ light gray plains formed

_2_ tectonism produced grabens

21. On Earth they have been obliterated by tectonic processes and agents of gradation (wind and

Answer Key, continued

Exercise Two: Geologic Landforms

Seen on Aerial Photos
17

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Questions

Volcanism

1. Examine the cinder cone of Mount Capulin, New Mexico, shown in Figure 2.1. The depression at its summit is referred to as a volcanic crater.

a. Describe the general shape of the cone and the volcanic crater at the top.

b. What is the white spiral line from the base of the cone to the crater rim?

Based on the elevation of Mt. Capulin (334m) and the information provided by the aerial photo, the slope

of the volcano's sides can be calculated. This simple sketch of Mt. Capulin will help.

Purpose

By studying aerial photographs you will learn to

identify different kinds of geologic features, tell

how they differ from one another, and learn the

processes involved in their formation.

Materials

Ruler (metric)

Introduction

The four major geologic processes (gradation,

impact cratering, tectonism, and volcanism) each

produce distinct landforms. A landform can be

identified based on its shape and form, or its

morphology. Volcanism is the eruption of melted

rock (called magma) and its associated gases onto

the surface of the Earth. Volcanism commonly produces volcanoes and volcanic flows. Tectonism

involves the movement of rock by fracturing and

faulting, which results in earthquakes. Gradation

involves the erosion, transportation, and deposition

of surface materials. On Earth, running water, wind,

gravity and ice are the major agents of gradation.

Impact cratering occurs when material from outside

the Earth’s atmosphere (such as meteoroids and

comets) strike the surface. The aerial photographs in

this exercise will help you recognize landforms and

the geological processes that formed them. These

processes act on other planets, where they can generate similar landforms.

Name

x

y

Exercise

Two

Geologic Landforms

Seen on Aerial Photos

Exercise Two: Geologic Landforms

Seen on Aerial Photos
18

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

2. a. Using your ruler and the scale bar on Figure 2.1, determine (in meters) the distance x, measured from

the base of the cone to the edge of the crater at the top of the cone.

b. The height y of the cone is 334m. Use trigonometry to estimate the average slope of the volcano’s

sides.

Examine the lava flow labeled A.

3. a. Does its surface appear rugged or smooth?

b. Trace the flow back to its point of origin. Where is the probable source of the flow?

Study Mt. Tavurur volcano, New Guinea, in Figure 2.2.

4. a. How is the volcano similar to Mt. Capulin?

b. How is it different?

5. Mt. Tavurur has erupted many times during its formation. How does the shape of the summit crater support this statement?

6. As you did for Mt. Capulin, estimate the slope of Mt. Tavurur's flanks. Draw and label a sketch similar to

the one provided for Mt. Capulin. The height of Mt. Tavurur is 225m. Measure length x from the edge of

the volcano at the ocean to the rim of the summit crater.

Exercise Two: Geologic Landforms

Seen on Aerial Photos

Sketch area
19

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Two: Geologic Landforms

Seen on Aerial Photos

7. List some factors that might affect the slope of a volcano.

Tectonism

Southern California is cut by many faults. These are usually visible on aerial photographs as straight or gently curving linear features, often forming distinct divisions between landforms. Examine Figure 2.3, an oblique

view of the San Andreas fault (arrow). A fairly straight valley trends from the bottom toward the top of the

photo. (The dark line to the left of the fault is a canal lined with vegetation.) Over time, the ground to the left

of the fault is moving away from us with respect to the ground to the right of the fault.

8. In what way does the fault affect the morphology of the mountains in this photo?

Tear a piece of paper in half. Place the two halves side by side and draw a line from one piece across onto

the other. Making certain that the edges of the pieces remain in contact, slide the paper on the left away

from you and the paper on the right towards you. This motion illustrates what occurs along the San

Andreas fault and how it affects the features along it. This type of fault is called a strike-slip fault. 

9. a. What would have happened if the line on the paper was actually a road crossing a fault?

b. Are there any features like this in Figure 2.3?

One landform distinctive to tectonism is called a graben (see Figure 2.4). A graben is a valley bounded on both

sides by normal faults. The movement along these faults is vertical, with the central block moving downward

in relation to the sides.

10. For block B to have enough space to move down, what has to occur to blocks A and C in Figure 2.4?

Figure 2.4. Diagram of a graben.

A C B
20

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Gradation

Figure 2.5 is a vertical photo of alluvial fans at Stovepipe Wells, Death Valley, California. These features result

from the build up of alluvium (gravel, sand, and clay) that accumulates at the base of mountain slopes. “Fan”

describes the general shape of the feature.

11. a. What is the source of the alluvium that makes up the fans?

b. Which agents of erosion (wind, water, and/or gravity) might have generated the alluvium?

c. Which agent(s) deposited it?

d. Once deposited, how might the alluvium be further eroded?

Figure 2.6 is a photograph of the Delta River, a braided stream in central Alaska. This river carries melt

water and silt from glaciers to the Pacific Ocean. Rivers of this type are usually shallow. Because they are

laden with sediments, they often deposit the sediments to form sandbars. These sandbars redirect the river

flow, giving the river its branching, braided appearance.

12. a. How is the Delta River an agent of gradation that works to change the surface?

b. Do the individual river channels appear to be permanent, or do they change position with time? How

do you know?

Impact Craters

Examine the photographs of Meteor Crater, an impact crater in Arizona. Figure 2.7 (a) is a vertical aerial photograph, and Figure 2.7 (b) is an oblique view.

13. a. Describe the crater’s general shape.

b. Meteor Crater is one of the best preserved craters in the world. However, it has been eroded somewhat. List some evidence for this.

14. The meteor that impacted here was about 25m across. Measure the diameter of Meteor Crater. How many

times bigger than the meteor is the crater?

15. a. Describe how the morphology of Meteor Crater is different from the volcanic landforms shown in 

Figures 2.1 and 2.2.

Exercise Two: Geologic Landforms

Seen on Aerial Photos
21

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

b. How is it similar?

Examine the view of Roter Kamm impact crater, Namibia, Figure 2.8.

16. a. Describe its morphology?

b. Compared to Meteor Crater, does it look fresh or eroded? Explain.

17. a. How is Roter Kamm crater different from the volcanic landforms of Figures 2.1 and 2.2?

b. How do they look similar?

Synthesis

Different processes produce landforms that are different in morphology. Linear, straight features are generally

tectonic in origin. More sinuous features (such as river valleys) are typically formed by gradational processes.

Volcanism forms flows in irregular patches and cones.

A part of central Arizona is shown in Figure 2.9. Represented here are landforms shaped by three of the four principal geologic processes. For each labeled landform, identify its type and the process that formed it.

18. A. E.

B. F.

C. G.

D.

19. Identify a place in the photograph where a pre-existing graben has affected the morphology of a later volcanic

flow. Sketch what you see, and describe in words what happened. (Use the sketch area on the next page.)

Exercise Two: Geologic Landforms

Seen on Aerial Photos
22

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Two: Geologic Landforms

Seen on Aerial Photos

Sketch area

20. Determine the sequence of events that affected this region. Order the events below from first occurring (1)

to most recent (5).

___ river and stream valleys formed 

___ dark (black) volcanic materials were deposited

___ medium gray volcanic flows were deposited

___ light gray plains formed

___ tectonism produced grabens

21. Large impacting objects such as asteroids have rarely fallen to Earth in the last few million years, but billions

of years ago they were very common. Assuming that throughout the geologic history of Earth, as many

impacts have occurred as on the Moon, then why do we see so few craters on the Earth today, while so many

remain visible on the Moon?
23

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Two: Geologic Landforms

Seen on Aerial Photos

Figure 2.1. Mount Capulin, New Mexico; vertical aerial photograph. (University of Illinois Catalog of Stereogram Aerial

Photographs #105.)

200 m

N

A

AG
24

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ Figure 2.2. Mt. Tavurur. Vertical view of a composite volcano on the eastern Pacific island of New Britain, Papua, New Guinea. (Univ. Of Illinois Catalog of Stereogram Aerial Photographs, #102.)

Exercise Two: Geologic Landforms

Seen on Aerial Photos

200 km

N
25

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Two: Geologic Landforms

Seen on Aerial Photos

Figure 2.3. Oblique aerial view of a part of the San Andreas fault north of Los Angeles. North is to the top right. The

foreground is approximately 3.5 km across. (photograph by Robert E. Wallace, U.S. Geological Survey). 

N
26

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Two: Geologic Landforms

Seen on Aerial Photos

Figure 2.5. Vertical view of alluvial fans near Stovepipe Wells, Death Valley, California. Panamint mountains lie to the

south. North is to the bottom left. (University Of Illinois Catalog of Stereogram Aerial Photographs, #125).

Figure 2.6. The Delta

River, a braided

stream in central

Alaska. North is to

the top. (U.S. Navy

photograph courtesy

of T. L. Péwé, Arizona

State University).

1 km
27

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Two: Geologic Landforms

Seen on Aerial Photos

Figures 2.7.a.,

2.7.b. Meteor

Crater, Arizona: (a)

vertical view, (b)

oblique view. One of

the best preserved

meteor impact

craters in the world,

Meteor Crater was

formed about 20,000

years ago. North is

to the top. (a,

University of Illinois

Catalog of

Stereogram Aerial

Photographs, #5; b,

Photograph courtesy

U.S. Geological

Survey.)

400 M

N

N
28

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Two: Geologic Landforms

Seen on Aerial Photos Figure 2.8. Roter Kamm crater, Namibia. This impact crater is 2.5km across and formed more than one million years ago. North is to the top. (Photograph courtesy Robert Deitz; from Meteoritics, vol. 2, pp. 311-314, 1965.)

500 m

N
29

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Two: Geologic Landforms

Seen on Aerial Photos

Figure 2.9. Mosaic of Landsat frames showing north-central Arizona. North is to the top.

N

A

B

C

D

E

F

G
31

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Purpose

The objective of this exercise is to use stereoscopic

(“three-dimensional”) photographs in understanding

the four major geologic processes (gradation, impact

cratering, tectonism, and volcanism).

Materials

Pocket stereoscope, protractor, ruler, calculator

Background

Before working this exercise, students should be

introduced to the concept of stereoscopic viewing.

Objects appear “three-dimensional,” that is they

show depth, because we view them with each eye

from slightly different perspectives. Stereoscopic

photographs appear three-dimensional because

they consist of two images of the same feature taken

from two different perspectives. When viewed in a

stereoscope, the features appear to have depth. The

stereo images have different degrees of “vertical

exaggeration,” the apparent increase in vertical

relief that results when viewing images obtained

from viewing perspectives separated by a large distance. These ideas are further explained in the student part of this activity.

This exercise uses pairs of stereoscopic photographs that illustrate landforms shaped by the four

principal geologic processes: volcanism, tectonism,

gradation, and impact cratering. Students should be

introduced to these processes through lecture before

working the exercise (see introduction to Unit One).

Parts A through D concentrate on specific examples

of the four geologic processes and generally increase

in difficulty; part E involves synthesis of the preceding parts. Starred (*) questions might be omitted at

the high school level. In some instances, in-depth

material that pertains to specific questions is found in

the instructor answer key. 

It is best for students to work this exercise in pairs or

small groups. If the availability of images or stereoscopes is limited, then students might move among

work stations prearranged by the instructor.

When first trying to view stereo photographs, some

students may become frustrated. Encouragement and

patience are important in getting this exercise started.

It is helpful to have the students place their index fingers on the same object within each photo of the stereo

pair and then adjust the position of the stereoscope

until their fingers appear to overlap. When they

remove their fingers, the stereo effect should become

apparent. However, vision problems may prevent

some students from seeing in stereo at all. These students should not be penalized, but should analyze the

photographs “monoscopically,” while working with

other students who can achieve the stereo effect.

The instructor may wish to explore some additional

demonstrations to illustrate aspects of stereo photography. If a stereo pair is cut along the dividing

line and the left and right images are switched,

inversion occurs; that is, mountains become depressions, and valleys become ridges. If you have a camera (an instant camera is best), you can make your

own stereo pairs. Take two photos of your classroom (or any other object) from positions a few feet

apart. Place the photos side by side under a stereoscope and adjust them until they align and the

stereo effect is seen. The further apart the photos are

taken, the greater the vertical exaggeration.

Exercise

Three

Geologic

Landforms Seen on

Stereoscopic Photos

Instructor Notes

Suggested Correlation of Topics

Gradation, impact cratering, tectonism,

volcanism, photography, scientific tools

2.0 hours

Exercise Two is suggested as an

introductory exercise.

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos
32

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

1. a. Sketch should show steep sides and a relatively flat top. 

b. The crater is roughly circular, but is irregular in detail, with multiple scallops.

c. The scalloped outline reflects craters from

multiple eruptions.

d. Gullies have been carved down its flanks

by runoff of rainfall, waves have eroded

the visible base of the volcano, and the

inlet has cut into volcanic material. 

e. The flanks have been eroded to form deep

parallel gullies. The easily eroded material

is unlikely to be rock but is probably ash. 

f. Rainfall is typically greatest on the windward side of a high-standing volcano. This

is because air cools as it rises up the mountain's flanks, promoting condensation and

precipitation of water. The air is relatively

dry as it passes over the other side of the

volcano.

2. a. Wind blows from the southwest (lower

right). The dunes show slip faces on their

northeast sides. 

b. A dune in the center of the photo will

migrate towards the northeast (the upper

left of the photo).

c. In the lower right, dunes coalesce into linear ridges (called “transverse dunes”).

Crescent shaped (“barchan”) dunes form

toward the center, near a dark area blown

free of dunes. Toward the upper left of the

photo, dunes are U-shaped and convex the

opposite way from the dunes in the lower

right.

d. Sand supply, consistency of wind direction,

wind velocity, and the presence of vegetation all affect dune morphology.

3. a. The sketch should show a tree-like “dendritic” pattern of smaller branches that join

into the main trunk stream.

b. South. The downhill direction is indicated

by the direction small streams flow near

their intersection with the larger one. A

“Y” pattern typically results, with the Y

pointing downstream. 

c. Material is eroded from the rock cliffs of

the waterfall and washed downstream.

Gradually the cliffs will retreat in the

upstream direction, lowering the overall

topography of the region. This process is

termed “headward erosion.”

d. The ridge is becoming more narrow as

debris is washed down the steep slopes to

either side during rains. Some of this material is visible in fans near the bases of the

steep slopes. Eventually the more resistant

material atop the ridge will be eroded

through, and the less resistant material

beneath will erode away relatively rapidly. 

4. a. Gray. The white layers form ridges but the

gray material is eroded out into valleys. In

some locations, white layers have sheltered

and protected the gray material from erosion. No river channels are apparent in the

white material; gullies indicate that the

gray material erodes easily. 

b. SSW c. N65W

d. 35m e. 220m

f. The stereo view reveals that the strata are

probably not curved, but have a constant

strike, and a constant dip to the southsouthwest. As the river cut downward, it

exposed portions of the white layers to the

south that are still buried elsewhere.

Therefore, the apparent curvature in the

monoscopic photo is a geometric consequence of the river having cut into the dipping strata, exposing the white layer at different elevations. 

5. a. About 1200m. b. About 240m. 

c. Large vertical exaggeration (appears as

deep or deeper than wide).

d. The crater shows a raised rim that stands

above the surrounding plain. The rim rises

30 to 60m above the surrounding plain.

e. Sketch should include bowl shape, rim-torim width of about 1200m [6cm] depth of

about 200m [1cm], and raised rim.

f. Similarities: Roughly round shape overall,

steep and gullied interior walls, highest

Answer Key

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos
33

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

along rim, relatively flat along crater bottom.

Differences: volcanic crater is irregular in

outline and shows multiple scallops, sits

atop an edifice; impact crater lies principally

below surrounding plains, has a raised rim,

is round to squared off in shape.

6. a. Steeply tilted. 

b. Roughly north-south strike; eastward dip. 

c. Erosion has destroyed most of a volcanic

plain that once was continuous across the

region. 

d. As is true of most places on Earth, impact

craters have been long since destroyed by

deposition of sediments, by tectonism, by

volcanic flooding, and by gradation.

e. Top to bottom: 2, 1, x, 4, 3

Answer Key

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos
Purpose

By using stereoscopic pairs of aerial photographs,

you will learn to recognize some of the landforms

that result from the four major geologic processes:

volcanism, gradation, tectonism, and impact cratering.

Materials

Stereoscope, protractor, ruler, calculator.

Introduction

Because our eyes are separated by a short distance, we view the world from two slightly different

perspectives simultaneously. This enables us to perceive a scene in three dimensions. In other words,

we are able to perceive the distances to objects and

depth within them. When you look at a photograph,

your eyes see the distance to the flat photo, rather

than the relative distances of objects within the

image. The photo appears flat, even though it is an

image of the three-dimensional world. To perceive

apparent depth in photographs, geologists obtain two

pictures of the same object or region from slightly different perspectives,

as illustrated in

Figure 3.1. When the

images are viewed

simultaneously, one

with each eye, a

“three-dimensional,” or stereoscopic,

effect results.

This perception of

vertical relief in aerial photos can greatly

aid the geologic

interpretation of

landforms in the

image. Most stereoscopic photographs

are obtained from

aircraft. Because

the distance the plane moves between subsequent

photos is much greater than the distance between a

person’s eyes, the apparent vertical relief of the

stereo photos is exaggerated, appearing much

greater than the actual relief. This vertical exaggeration increases the farther apart the photographs

are taken.

Figure 3.2 shows how to set up a pocket stereoscope. Place the stereoscope over a stereo pair with

the seam of the photos in the middle of the stereoscope. Look through the lenses at the two photos, so

that each eye sees just one photo. Pick out a feature

that is visible in both photos, relax your eyes, and

allow your focus to change until the two images

appear to merge. You may need to adjust the position

of your stereoscope slightly as you look through it to

help the photos merge. When they do merge, you

should see a stereoscopic effect. This may take time

and patience. Some of the photographs are stereo

35

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Figure 3.2. Using the pocket stereoscope. The stereoscope is aligned

horizontally and centered along the

seam separating the image pairs. 

Name

Figure 3.1. Stereoscopic photographs are typically

obtained from airplanes. The farther apart two photographs are obtained, the greater the vertical exaggeration of the resulting stereoscopic images.

Exercise

Three

Geologic

Landforms Seen on

Stereoscopic Photos

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos
36

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Questions

Volcanism

1. Figure 3.3 shows a volcano on the island of New Britain, north of Australia. First study the photos

“monoscopically,” without the stereoscope. In the photos, water appears black. The top of the highstanding volcano shows a circular depression termed a summit crater.

a. Sketch how the volcano might look from the ground.

“triplets” with one photograph in the middle and

additional photographs on both the right and left

sides. The stereoscope should be positioned to view

the middle and right photos as one image pair, and

the middle and left photos as another image pair. 

Sketch area

Now position the stereoscope over the left dividing line and view the volcano in stereo. Reposition the

stereoscope over the right seam and view this portion of the volcano in stereo.

b. Observe and describe the shape of the summit crater.

c. Do you think the summit crater formed by a single eruption or from multiple eruptions? Explain.

d. List at least two pieces of evidence that the volcano has been eroded.

e. Do you think the volcano is made of hard rock that is difficult to erode or soft ash that is easy to

erode? Explain.

*f. Why is the volcano more heavily forested on one side than the other?

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos
37

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

Gradation

2. Figure 3.4 shows a portion of White Sands, New Mexico, an area affected by aeolian (wind) processes.

The crescent-shaped features are dunes composed of sand. Most sand dunes have a gentle slope on their

windward side and a steeper slope to the leeward side. High velocity winds blow sand up the windward side to the brink of the dune; sand then slides down the leeward slip face of the dune. 

a. Examine the photographs stereoscopically and identify the slip faces on the dunes. From which direction is the wind blowing?

b. Consider one of the dunes near the center of the photo. Where will its sand go in time?

c. How does the morphology of the sand dunes change across the photo? Use sketches of at least two

dunes to illustrate your answer.

Sketch area

Sketch area
38

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

*d. What factors might affect the dune morphology across the region?

3. Examine Figure 3.5, which shows a system of canyons cut by rivers and streams in northwestern New

Mexico. The gradation is affecting relatively flat-lying sedimentary rocks. 

a. Look at the places where smaller tributary streams join larger rivers. In the space below, make a

sketch of the pattern you see.

Sketch area

b. Which direction does the water flow in the prominent river that crosses the central portion of the

photo?

c. Identify a place in the photograph where you might expect a tall, steep waterfall. How would such a

waterfall aid the process of erosion in this area?

d. Over time, what will happen to the high standing, narrow ridge that separates two east-west trending

valleys in the central portion of the photo?

Tectonism

Most rocks on Earth are laid down in relatively flat layers. Sedimentary rocks (such as those in Figure 3.5) are

laid down over broad areas by wind or water, in layers called strata. Tectonism deforms such rocks in various

ways. Tectonic stresses in the Earth can pull or push on rocks until they break, moving along faults. Broadscale tectonic deformation can also cause originally horizontal rock layers to be tilted.

4. Figure 3.6 shows Lookout Ridge, Alaska, an area affected by tectonic deformation. Notice that the white

and gray sedimentary rocks have been steeply tilted, now standing nearly on their ends.

a. Which rock layers are more easily eroded, the white or the gray? Support your answer.

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos
39

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

b. Examine the broad, steep face that is shown by one of the white layers near the center of the stereo photo.

When rainfall lands on this surface, in which direction would it run down? This is the dip direction of

these tilted rocks.

c. Examine the overall trend of the visible edges of the tilted strata. Use a protractor to measure the direction

of this trend, and report your answer in terms of the number of degrees west of north. (For example,

N20W would mean the trend is 20° west of north.) This is the strike direction of the tilted rocks.

d. Notice the small-scale faults that cut and displace the white and gray strata near the center of the stereo

image. Use the scale bar on the photograph to estimate the amount of displacement along these faults.

e. A greater displacement of strata can also be observed in the southeast corner of the left hand monoscopic

image. Use the scale bar to estimate the amount of displacement there.

*f. In the right hand image, the strata appear to curve as they cross the prominent river that cuts northsouth across the photo. Using information available to you from the stereo scene, explain this apparent curvature.

Impact Cratering

5. Figure 3.7 shows Meteor Crater, Arizona. The impact crater is about 20,000 years old and is one of the

best-preserved impact structures on Earth. In this stereo pair you can see the crater floor, walls, rim, and

remnants of ejecta, material thrown from the crater by the impact. Some ejecta appears as irregular

bright patches around the crater. 

a. Using the scale bar on the photograph, determine the diameter of the crater in meters.

b. Before erosional infilling, an impact crater in Meteor Crater’s size class has a diameter about five

times greater than its depth. Based on this, how deep was Meteor Crater when it formed?

c. Based on the appearance of Meteor Crater in these stereo images, and considering your previous

answers, is the vertical exaggeration of this stereo pair large or small?

d. What do you notice about the elevation of the rim of the crater compared to the elevation of the surrounding plain?
40

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

e. Sketch a non-exaggerated profile across Meteor Crater in the space below. Use a scale of 1cm = 200m.

The present depth of the crater is about 85% of its original depth, due to erosional infilling. Use your

answer from 5.b. to determine the present depth to use for your profile.

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

Sketch area

f. List some similarities and differences in the morphology of Meteor Crater compared to the volcanic

summit crater seen in Figure 3.3.

Synthesis

Planetary surfaces represent combinations of some or all of the four geologic processes. In the following questions, you will synthesize information from the previous questions and photographs.

6. Examine Figure 3.8, which shows the Caballos mountains of southwestern New Mexico. The two nearly featureless “islands” of high standing rock are volcanic in origin. Beneath them are rocks that were laid down

as sedimentary strata. 

a. Examine the strata of Figure 3.8, comparing this scene to Figures 3.5 and 3.6. Are the strata of the

Caballos mountains tilted or flat-lying?

b. Estimate the strike and dip directions of the strata in the region beneath the western “island” of volcanic rock.

c. What is the most likely explanation to account for the isolated islands of volcanic plains?

d. Why are no impact craters visible in this area?
41

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

e. Determine the sequence of events that affected this region by numbering the events below from 1

(first event) to 4 (most recent event). Mark with an “x” the one event that did not occur in this region. 

___ Tectonic forces caused folding and tilting of the rocks.

___ Sedimentary strata were laid down horizontally. 

___ Volcanic plains were faulted and tilted. 

___ Erosion by rivers and streams dissected the region.

___ Volcanic plains were laid down horizontally.
42

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos Figure 3.3. Gazelle Peninsula, island of New Britain, New Guinea. (University of Illinois Catalog of Stereogram Aerial Photographs #107).

200 m

N
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

Figure 3.4. White Sands, Tularosa Basin, New Mexico. North is to the left (University of Illinois Catalog of Stereogram Aerial Photographs #509).

N
44

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

Figure 3.5. Monument Rocks, San Juan County, New Mexico. North is to the left. (University of Illinois Catalog of

Stereogram Aerial Photographs #521).

N 1 km
45

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

Figure 3.6. Lookout Ridge, Alaska. North is to the bottom. (University of Illinois Catalog of Stereogram Aerial Photographs #156).

300 m

N
46

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

Figure 3.7. Meteor Crater, Arizona. North is to the bottom. (University of Illinois Catalog of

Stereogram Aerial Photographs #5).

N 400 m
47

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Exercise Three: Geologic Landforms

Seen on Stereoscopic Photos

Figure 3.8. Sierra Caballos Mountains, New Mexico. North is to the left. (University of Illinois Catalog of

Stereogram Aerial Photographs #138).

N
49

EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

The following activities demonstrate the fundamental principles of impact crater formation.The activities are simulations; true impact or

volcanic events take place under conditions different

from the classroom. Although some aspects of the

simulations do not scale directly, the appearance of

the craters formed in these activities closely approximates natural, full size craters. These laboratory exercises can be used to stimulate discussions of planetary

landscapes, terrestrial craters, and the evolution of

planetary surfaces.

In these experiments, students will study the

craters formed when objects of different masses and

traveling with different velocities strike a target of fine

sand. This activity demonstrates important concepts:

first, there is a relationship between the velocity and

mass of the impactor and the size of the crater formed;

and second, craters can be divided into distinct zones:

floor, wall, rim, ejecta. The “Rainy Day” experiment

illustrates the relation between crater frequency and

relative surface age, as well as demonstrating the

effect of illumination angle on identifying craters.

On Earth, volcanic explosion craters are often

formed when magma rises through water-saturated

rocks and causes a phreatic, or steam explosion.

Volcanic explosion craters from phreatic eruption

often occur on plains away from other obvious volcanoes. Other volcanic eruptions can cause mild explosions, often in a series of events. Some volcanic craters

form by collapse with little or no explosive activity.

Volcanic craters are typically seen either on the summits or on the flanks of volcanoes. Volcanic craters

have also been identified on the Moon, Mars, Venus,

and Io. The exercise comparing these cratering

processes will help the student learn to identify the

differences in the resultant craters.

Unit Two

Introduction to

Impact Cratering
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Purpose

This exercise demonstrates the mechanics of

impact cratering and will show the student impact

crater morphologies. Upon completion of this exercise the student should understand the relationship

between the velocity and mass of the projectile and

the size of the resultant crater. The student should

also be able to identify the morphologic zones of an

impact crater and, in certain cases, be able to deduce

the direction of the incoming projectile.

Materials

Suggested: If performed as an instructor demonstration: one set of the following:

• sand (very fine and dry), tray (e.g., kitty litter

box), dyed sand, slingshot, scale, ruler, lamp,

calculator, safety goggles, drop cloth, fine

screen or flour sifter

• projectiles: 4 different sizes of steel ball bearings; 4 identical ball bearings of one of the intermediate sizes, one each of the three other sizes

(sizes should range from 4mm to 25 mm)

• 3 identical sized objects with different densities (e.g., large ball bearing, marble, balsawood or foam ball, rubber superball)

If performed by students: enough sets of the

above list for all students/groups.

Substitutions: dry tempera paint can be drymixed with sand to make dyed sand (but do not get

this mixture wet!), a thick rubber band can be substituted for a slingshot.

Background

This exercise demonstrates the mechanics of impact

cratering and introduces the concept of kinetic energy

(energy of motion): KE = 1/2 (mv2), where m = mass

and v = velocity. The effects of the velocity, mass, and

size of the impacting projectile on the size of the resultant crater are explored. By the conclusion of the exercise, the student should understand the concept of

kinetic energy, and know that the velocity of the

impactor has the greatest effect on crater size [KE =

1/2 (mv2

)].

Use of a slingshot to fire projectiles is required in

this exercise. It is the instructor’s decision whether this

exercise should be done as a demonstration or by the

student. Students should be supervised carefully at all

times during the firing of the projectiles and everyone

should wear protective goggles. Place the tray on a

sheet of plastic or drop cloth; this will make cleanup

easier. Fill the tray completely with sand, then scrape

the top with the ruler to produce a smooth surface.

The dyed sand is best sprinkled on the surface

through a fine screen, or a flour sifter.

This exercise requires the calculation of kinetic

energies. All of the velocities necessary for these calculations have been provided in the student’s charts.

Calculation of velocity for dropped objects is simple

using the formula:

v = (2ay).5 where v is the velocity, a is the acceleration due to gravity (9.8 m/s2

), and y is the distance

dropped

Calculation of the velocity for objects launched by a

slingshot is a time consuming procedure for values

used in only two entries in the exercise; however, it is

an excellent introduction to the physics of motion and

can be done in a class period before performing this

exercise. The procedure for calibrating the slingshot

and for calculating velocities of objects launched by

the slingshot follows the answer key (where it may be

copied for student use).

Advanced students and upper classes can answer

the optional starred (*) questions, which apply their

observations to more complex situations.

Exercise

Four Impact Cratering

Instructor Notes

Exercise Four: Impact Cratering

2.0 hours

Suggested Correlation of Topics

Craters on planets and satellites, gradation,

impact mechanics, physics
52

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

1. a. The crater.

b. Undisturbed surface layer of sand. 

c. No.

d. Thick and continuous near the crater, thin

and discontinuous far from the crater.

2. Not much, although the ejecta of the 65° impact

may be slightly oblong. 

3. As impact angle decreases toward 10°, ejecta

becomes more oblong pointing downrange.

Ejecta is absent on the uprange side of the

crater.

4. a. Low angle.

b. Entered from the east and bounced off the

surface leaving two craters with an oblong

ejecta pattern.

5. a. The higher the kinetic energy, the larger

the crater.

b. Higher velocities produce larger craters.

c. Larger masses produce larger craters.

d. Larger sizes (of the same density material)

produce larger craters. Mass (density) is the

controlling factor. Size (radius) is not a factor

in the equation for kinetic energy.

Instructor’s note: Impacting objects in space

have different densities. For example, meteorites occur as high density objects (iron

meteorites) or as lower density objects (stony

meteorites). Comets are composed mostly of

water ice and have relatively low density.

Like the foam ball, impacting comets might

not form a crater at all.

e. Velocity of the projectile is most important,

as shown by the kinetic energy equation.

*6. Craters are better preserved on flat terrain. In

rugged areas, craters can be modified by

landslides (mass wasting). 

Answer Key

Velocity

(m/sec)

Mass

(kg) KE (Nm =

kg m2/sec2)

Crater

Diameter

(cm)

Shot 1

Shot 2

Shot 3

Shot 4

1.4

6.3

14*

69*

~0.002

~0.002

~0.002

~0.002

0.00196

0.03969

0.196

4.761

~2

~4

~5

~11

Part B

Velocity

(m/sec)

Mass

(kg) KE (Nm =

kg m2/sec2)

Crater

Diameter

(cm)

Shot 1 (4 mm)

Shot 2 (8 mm)

Shot 3 (18 mm)

Shot 4 (25 mm)

6.3

6.3

6.3

6.3

~0.00034

~0.002

~0.028

~0.067

0.0067473

0.03969

0.55566

1.329615

~2.5

~3.5

~7

~7

Part C

Velocity

(m/sec)

Mass

(kg) KE (Nm =

kg m2/sec2)

Crater

Diameter

(cm)

Shot 1 (steel)

Shot 2 (glass)

Shot 3 (wood)

6.3

6.3

6.3

~0.028

~0.008

~0.002

0.55566

0.15876

0.03969

~7

~6

~3.5

Part D

* velocities are approximate; NM = Newton x meter

Exercise Four: Impact Cratering

Science Standards

■ Earth and Space Science

• Origin and evolution of the Earth system

Mathematics Standards

■ Geometry

■ Computation and Estimation

■ Measurement
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Objective

To determine the initial velocity of a mass that is

propelled by a slingshot.

Background

This procedure applies two physical laws,

Hooke’s Law and the Law of Conservation of

Energy. Hooke’s Law (F=kx) states that the force (F)

applied to an elastic material depends upon how

stiff the material is (k) and how far you pull the elastic material (x). The stiffness of the elastic material

(k) is small if the elastic material is soft, and large if

the elastic material is stiff. The Law of Conservation

of Energy (W = PE = KE) states that there is a relationship between work (W) performed on a system

(the force applied to an object to move it a certain

displacement in the same direction as the force is

acting) and the potential energy (PE, stored energy)

of a system and the kinetic energy (KE, energy of

motion) of the system. The equations for Hooke's

Law, work, and potential energy are derived from a

graph of force versus elongation.

The velocity term that we want to solve for is

found in the kinetic energy portion of the Law of

Conservation of Energy.

KE = 1/2 mv2, where m is the mass of the object

being launched and v is the velocity.

The potential energy of elasticity is a combination

of Hooke's Law and work.

PE = 1/2kx2 where k is the spring constant and x

is the elongation distance of the slingshot—

how far back it is pulled.

Because the Law of Conservation of Energy states

that the potential and kinetic energies of a system

are equal, we can set these equations equal to each

other.

1/2mv2 = 1/2kx2

; solving for v gives:

v = (kx2

/m).5

We will control x (the distance pulled back) and

will measure m (the mass of the object being

launched). But to solve for v (the velocity) we must

first calibrate the slingshot by experimentally solving for the spring constant, k.

Exercise Four: Impact Cratering

Calibrating the Slingshot

Duct Tape

Meterstick

Tape marking point

of equilibrium

Mass a

Meterstick

Tape marking point

of equilibrium Stretched tubing

Mass measurement

F

(N)

Elongation (n)

Points for Graph

(Displacement x, Force y)

Force from conversion of

Mass a
54

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

How to Solve For k

1. Place the slingshot on the edge of a table or

counter so that the elastic band hangs free.

Immobilize the slingshot by placing a large

weight on it or by duct-taping it to the counter.

Rest a meter stick on the floor and tape it along

side the slingshot. Pull down on the elastic tubing of the slingshot until all the slack is taken

out, but do not stretch the tubing. Mark this

point on the meter stick. This is the point of

equilibrium.

2. Place slotted masses in increments of 100, 150

or 500 grams (depending on the stiffness of the

slingshot) in the pocket of the slingshot until it

begins to elongate or stretch past the point of

equilibrium. This initial mass is called the “preload force” and is not counted as a recordable

force in the data table. (On the graph of force

versus elongation, the preload force will

appear as a y-intercept.) Once the slingshot

starts to elongate or stretch, begin recording

the amount of mass you are adding to the

pocket and how far from the point of equilibrium the pocket is displaced. Maximize your

range of data! Keep taking measurements until

you have 7 or 8 data points.

3. Convert the mass from grams into kilograms

and multiply by 9.8 m/s2 to get force in the

unit of Newtons.

example: 150 g (1 kg/1000g) = .150 kg;

.150kg(9.8 m/s2) = 1.47 N

Convert the elongation measurements from

centimeters to meters. Now you are ready to

graph force (in Newtons) versus elongation (in

meters).

4. Graph force (on the y-axis) versus elongation

(on the x-axis). The graph will be a linear function with the slope representing the spring constant, k (in N/m). If you are using a computer

graphing program it will automatically calculate

the slope and y-intercept of the graph. If you are

graphing on graph paper, calculate the slope of

the graph using two data points and the equation: slope = (y2-y1)/(x2-x1)

example: (3,5) (4, 6) slope = (6-5)/(4-3) = 1/1 =

1 N/m, in this case k = 1 N/m

If the graph has a y-intercept, disregard it (it is

simply part of the preload force).

The slope of the line is the value of the spring

constant, k, and can now be used in the velocity

equation above.

Exercise Four: Impact Cratering
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Name

Exercise Four: Impact Cratering

Exercise

Four Impact Cratering

Purpose

To learn about the mechanics of impact cratering

and the concept of kinetic energy; and to recognize

the landforms associated with impact cratering.

Materials

For each student group: Sand, tray, colored sand,

drop cloth, screen or flour sifter, slingshot, safety

goggles(one for each student), triple beam balance,

ruler, lamp, calculator

Projectiles: 4 different sizes of steel ball bearings: 4

identical ball bearings of one of the intermediate sizes,

one each of the three other sizes; 3 identical sized

objects with different densities (large ball bearing,

marble, wood or foam ball, rubber superball)

Introduction

Impact craters are found on nearly all solid surface planets and satellites. Although this exercise

simulates the impact process, it must be noted that

the physical variables do not scale in a simple way

to compare with full-size crater formation. In other

words, this exercise is a good approximation but not

the real thing.

Impact craters form when objects from space,

such as asteroids, impact the surface of a planet or

moon. The size of the crater formed depends on the

amount of kinetic energy possessed by the impacting object. Kinetic energy (energy in motion) is

defined as: KE = 1/2 (mv2

), in which m = mass and

v = velocity.

Weight is related to the mass of an object. During

impact the kinetic energy of the object is transferred

to the target surface.

Safety goggles must be worn whenever the

slingshot is in use!

Procedure and Questions

Part A

Place the tray on the drop cloth. Fill the tray with sand, then smooth the surface by scraping the ruler across

the sand. Sprinkle a very thin layer of the colored sand over the surface (just enough to hide the sand below)

using the flour sifter. Divide the tray (target area) into four square shaped sections, using the ruler to mark

shallow lines in the sand.

In one section produce a crater using the slingshot to launch an intermediate size steel ball bearing straight

down (at 90°, vertical) into the target surface. The slingshot should be held at arms length from sand surface

(70 to 90 cm) facing straight down into the tray. Do not remove the projectiles after launch. Use the space on

the following page to make a sketch of the plan (map) view and of the cross section view of the crater. Be sure

to sketch the pattern of the light-colored sand around the crater. This material is called ejecta. Label the crater

floor, crater wall, crater rim, and ejecta on the sketch.

1. a. Where did the ejecta come from?

b. What would you expect to find beneath the ejecta?
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

c. Would you expect the ejecta to be of equal thickness everywhere?

d. What is the ejecta distribution and thickness in relation to the crater?

In the next section of the target tray, produce a crater using the slingshot to launch a steel ball bearing (the

same size as above) at 65° to the surface. The angle can simply be estimated. The end of the slingshot should

still be 70 to 90 cm from tray. Be certain no one is “down range” in case the projectile ricochets. Sketch the

crater and ejecta in plan view on the space provided below.

Exercise Four: Impact Cratering

Sketch area

Sketch area

2. Is there an obvious difference between the two craters or ejecta patterns?

In the third section of the target tray, produce a crater using the slingshot to launch a steel ball bearing (the

same size as above) at 45° to the surface. Again, estimate the angle. The end of the slingshot should still be 70

to 90 cm from the tray. Be certain no one is “down range” in case the projectile ricochets. Sketch the crater in

plan view on the space provided on the following page. As above, label the parts of the crater.
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Exercise Four: Impact Cratering

In the fourth section of the target tray, produce a crater using the slingshot to launch a steel ball bearing (the same

size as the previous exercise) at about 5 to 10° to the surface. Again, estimate the angle, and make sure not to hit the

rim of the tray. The end of the slingshot should still be 70 to 90 cm from tray. Be sure no one is “down range” in case

the projectile ricochets. Sketch the crater in plan view and cross section on the space provided below.

Sketch area

Sketch area

Examine the sand craters and your sketches.

3. How does ejecta distribution change with impact angle? 

Examine Figure 4.1, a photograph of the lunar crater Messier.

4. a. Was this a high angle or low angle impact?

b. Did the meteoroid which formed Messier impact from the east or west?
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Four: Impact Cratering

Part B

Remove the four steel ball bearings from the sand tray and thoroughly mix the sand and colored sand to produce a uniform mixture. Smooth the target surface with the ruler. The remaining experiments will be performed

without a colored upper layer of sand. Divide the target area into four sections as before.

Produce four craters on the smooth target surface, using the same four identical steel ball bearing as in Part A.

Find the mass of one of the projectiles before launching it and enter the value in the table below. 

• Make the first crater by dropping the projectile from a height of 10 cm above the surface. Measure the diameter of the crater formed and enter the value in the table.

• For the second crater, drop the projectile from a height of 2 meters. Measure the crater diameter and enter it

in the table.

• The third projectile should be launched with the slingshot 70 to 90 cm above the tray and with the rubber

tubing pulled back slightly (extended ~3 cm). Measure the crater diameter and enter it in the table.

• For the last crater, extend the slingshot ~15 cm. The slingshot should still be 70 to 90 cm above tray. Measure

the crater diameter and enter it in the table. 

• Calculate the kinetic energy of each projectile and enter the values in the table.

Velocity

(m/sec)

Mass

(kg) KE (Nm =

kg m2/sec2)

Crater

Diameter

(cm)

Shot 1

Shot 2

Shot 3

Shot 4

1.4

6.3

14*

69*

Part B

* velocities are approximate

Part C

Remove the projectiles and smooth the target surface with the ruler. Divide the target into four sections. Find the

mass of each projectile and enter the values in the table below. Produce four craters by dropping 4 different sized

steel ball bearings from a height of 2 meters above the target surface. Measure the crater diameter produced by each

impact. Enter the projectile mass and resultant crater diameters in the table below. Calculate the kinetic energy of

each projectile and enter the values in the table on the next page.
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Exercise Four: Impact Cratering

Part C

Part D

Remove the projectiles and smooth the target surface with the ruler. Divide the target into three sections. Find

the mass of each projectile and enter the values in the table below. Produce three craters by dropping 3 identical

size, but different mass, projectiles from a height of 2 meters above the target surface. Measure the crater diameter produced by each impact. Enter the projectile mass and resultant crater diameters in the table below. Calculate

the kinetic energy of each projectile and enter the values in the table below.

Velocity

(m/sec)

Mass

(kg) KE (Nm =

kg m2/sec2)

Crater

Diameter

(cm)

Shot 1 (smallest)

Shot 2 (next larger)

Shot 3 (next larger)

Shot 4 (largest)

6.3

6.3

6.3

6.3

Part D

Velocity

(m/sec)

Mass

(kg) KE (Nm =

kg m2/sec2)

Crater

Diameter

(cm)

Shot 1 (steel)

Shot 2 (glass)

Shot 3 (wood)

6.3

6.3

6.3

Examine the results of parts B, C, and D. Use the completed tables to answer the following questions.

5. a. How does kinetic energy of the projectile relate to crater diameter?

b. How does velocity relate to crater size?

c. How does mass relate to crater size?
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

d. How does the size of the projectile relate to crater size?

e. Which is the most important factor controlling the crater size; the size, mass, or velocity of the projectile?

*Part E

Remove all projectiles from the sand tray and smooth the target surface. Divide the sand into two equal

halves. In one half form a ridge of sand about 10 cm high and 15 cm wide, and leave the other half smooth.

Use intermediate size steel ball bearings and form one crater on the side of the ridge. Form another crater on

the flat section, launching it with the slingshot from 70 to 90 cm above the tray. Compare the two craters.

*6. What can you say about crater preservation on rugged terrain versus smooth terrain?

Exercise Four: Impact Cratering
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Exercise Four: Impact Cratering

Figure 4.1. Apollo 15 photograph of lunar craters Messier A and B. The small crosses are camera registration marks.

North is to the upper right corner of the photo. The oblong crater (Messier A) is 11 kilometers in diameter. (Apollo

Metric frame AS152674).

10 km

N
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Exercise Five: Comparative Cratering Processes

Exercise Four is suggested as an

introductory exercise.

Exercise

Five

Comparative

Cratering Processes

Instructor Notes

2.0 hours

Purpose

The objective of this exercise is to learn how different cratering processes produce different surface

features. This exercise will explore three cratering

processes: impact, volcanic explosion, and volcanic

eruption.

Materials

Suggested: For each student group (or single set

if done as instructor demonstration):

■ tray (kitty litter box)

■ very fine dry sand

■ safety goggles (for everyone)

■ marbles

■ slingshot

■ video camera

■ VCR (4-head is best for stop action) and TV

■ black posterboard (2’ x 3’)

■ 3-foot-long narrow diameter flexible plastic

tubing(surgical tubing)

■ bicycle pump

■ thin skinned balloons

■ hose clamp

■ sheet of clear heavy plastic (to protect camera)

Substitutions:

■ instant camera with cable release

■ 3 packs of instant black and white film

■ high intensity strobe light (variable to at least

15 flashes per second)

[Note: strobes can be dangerous to persons

with epilepsy]

■ 2 boxes or stacks of books: one for the camera, one for the strobe

Background

Impact craters are found on nearly all solid surface planets and satellites. However, other geologic

processes, such as volcanic explosions and eruptions, can form craters as well. The differences

between craters formed by impact and explosion

can be very slight. Non-explosive volcanic craters

can usually be distinguished from impact craters by

their irregular shape and the association of volcanic

flows and other volcanic materials. An exception is

that impact craters on Venus often have associated

flows of melted material.

This exercise demonstrates three processes that

can form craters. Because the simulations in this

activity do not scale in size to natural geologic

events, the variations noted by the students may be

very slight.

The use of the slingshot in this exercise can be

dangerous. This exercise can be done as a demonstration to avoid accidents and to expedite its

completion.

Suggested Correlation of Topics

Craters on planets and satellites, gradation,

impact mechanics, physics
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Science Standards

■ Earth and Space Science

• Energy in the Earth system

Mathematics Standards

■ Geometry

Instant Camera Instructions

Instant cameras give the students an opportunity

to have an instant and permanent record of the exercise. Action is “stopped” by use of the strobe light

and students can reshoot if necessary. If using a

instant with an electric eye, set the film speed setting to 75 (even though the film speed is 3000) and

the exposure control on front of the camera to

“Darker.” This permits a longer exposure and a

smaller f/stop (larger lens opening). If the Instant

does not have an electric eye, but has numbered settings, set the number to “6” and flip the exposure

from “I” to “B” before each picture. If the resulting

photographs are too light, increase the number

accordingly. Focus the camera on the target surface

and place the black posterboard and the strobe light

as shown in Figure 5.3. The flash rate on the strobe

should seem like rapid blinks. Too many flashes

during the exposure produces a dispersed cloud;

too few, and the event may be missed entirely. In

using the camera, it is best if you have a cable

release attached to the Instant—this will help eliminate jarring the camera unnecessarily. If the camera

does not accept a cable release, be sure that the camera is on a firm surface; push the button and release

carefully. To get good photos, the film must be

exposed long enough to catch 2 flashes from the

strobe light (about 1/8 second). Start the exposure

just before the marble is fired and stop it right after

it appears to hit the sand. Be sure the student photographers know how to operate the camera before

starting the activity. Although the instructions and

precautions may seem involved, this exercise can be

done easily and successfully with a little practice.

Exercise Five: Comparative Cratering Processes
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Exercise Five: Comparative Cratering Processes

1. a. Answers will vary, student may say in

straight lines or arcs.

b. (See Figure 5.1) The formation of an impact

crater is a relatively well ordered event in

which the ejecta leaves the surface at approximately a 45° angle from the horizontal (upper

left picture Figure 5.1). As the crater enlarges

(middle left), the inverted cone sheet of ejecta,

called the ejecta plume, enlarges. Ejecta falls

first close to the crater, and as crater formation continues (bottom left), the ejecta strike

the surface at increasing distances. Note how

the base of the ejecta plume has enlarged

with time.

2. a. Ejecta from the vertical impact are thrown

out at about a 45° angle. The sheet of ejecta

moves outward in a symmetrical pattern, producing the appearance of an enlarging,

inverted cone. For the 45° impact, the ejecta

cone becomes asymmetrical and distorted in

the down-range direction.

b. (See Figure 5.2) As the angle of impact

departs from the vertical, the ejecta cone or

plume becomes asymmetric. For the relatively

low velocities represented in the figure (20

m/s), asymmetry is not apparent until the

impact angle is greater than 20°. At 20° (upper

right), the sequence of ejecta remains relatively symmetric. At 60° (lower left) and 75°

(lower right) from the vertical, the ejecta cone

is distorted in the downrange direction. For

impacts of much greater velocities (2 km/s),

the asymmetry does not occur until much

larger departures (80°) from the vertical.

3. a. (See Figure 5.1.) The upper and middle

right pictures in the figure show the relatively

chaotic and dispersed nature of the ejecta

caused by this type of cratering process.

b. In appearance, the crater shape is similar.

However, the ejecta pattern is chaotic and dispersed with ejecta thrown at all angles. Note

that the ejecta pattern and crater appearance

will vary with different depths of burial of

the balloon. 

4. (See Figure 5.1) The bottom right picture

shows the formation of the eruptive crater.

Ejecta is blown straight up and lands right

around the crater.

5. a. All three craters contain similar parts:

crater, rim, ejecta.

b. Answers will vary, but many students will

note that the explosive and volcanic craters

are not as symmetrical as the impact craters.

The volcanic eruption crater will be the most

irregular. 

c. All craters formed have raised rims.

d. Answers may vary. The crater ejecta patterns will probably be widest.

e. Impact has the greatest effect.

6. a. Olympus Mons (Figure 5.5) is volcanic;

Timocharis crater (Figure 5.6) is of impact

origin.

b. Timocharis has well developed ejecta patterns; the crater on Olympus Mons is irregular in outline and shows no ejecta patterns.

c. Impact craters have large, well-defined

ejecta patterns; the ejecta patterns of volcanic

explosion craters may not be as well-organized; volcanic eruption craters have little

ejecta or poorly organized ejecta patterns.

Answer Key
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Five: Comparative Cratering Processes

Figure 5.1. Comparison of the formation of an impact crater (left side), a low-energy explosion crater (top

two photos on the right side), and simulated volcanic eruptive crater (bottom right). All craters were

formed in a sand box and recorded using a strobe light.
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Exercise Five: Comparative Cratering Processes

Figure 5.2. Strobe light instant photographs of impacts into fine sand at different angles of incidence. Photograph

records two flashes of the strobe light in each illustration. The upper left image is for a vertical impact, upper right is at

20° from vertical, lower left is at 60° from vertical, and the lower right is 75° from vertical.
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Name

Exercise Five: Comparative Cratering Processes

Exercise

Five

Comparative

Cratering Processes

Purpose

To illustrate the similarities and differences in

craters formed by three different cratering processes:

impact, volcanic explosion, and volcanic eruption.

Materials

For each student group: tray (kitty litter box),

very fine sand, safety goggles (for all students), marbles, slingshot, video camera, VCR and TV, black

posterboard (2’ x 3’), 3-foot-long narrow diameter

flexible plastic tubing, bicycle pump, thin skinned

balloons, hose clamp, sheet of heavy clear plastic (to

protect the camera)

Introduction

In examining a planetary surface, it is important

to identify the processes that shaped the surface.

Not all craters form by impact processes; some

result from volcanic explosions and volcanic eruptions. This exercise examines the crater forms which

result from these three processes: impact, explosion,

and eruption.

Procedure and Questions

Part A: Impact Cratering Process

Use Figure 5.3 to set up the equipment for this part of the exercise. All students must wear safety goggles

during this part of the exercise. Hold the slingshot 70 to 90 cm above the target. While video taping the tray,

fire a marble straight down (vertically) into the sand tray using the slingshot . The goal is to photograph the

ejecta (material thrown out of the crater) while it is airborne and after it has landed. You may need to repeat

this part several times to get a good photographic record. 

Box of

Books

Strobe

Camera

Plexiglass

Box of Books Sand Tray Posterboard

Figure 5.3. Diagram showing the setup for photographing the impact experiment.
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Five: Comparative Cratering Processes

Sketch area

Sketch area

1. a. Before examining the video or photographs, describe how you think the ejecta will appear, and what 

path you think the ejecta took in the air.

b. Observe the video or photographs. Sketch the crater, the path the material appears to take in the air, 

and the pattern of ejecta deposited on the surface based on the photographic record and your

observations. Use the pause or stop action ability of the VCR to view the tape.

Remove the marble and smooth the sand surface. Record another impact while firing the marble at an angle

of 45° into the target surface. The slingshot should be 70 to 90 cm from the target. Be sure that no one is down

range and that you stand to one side and fire into the tray between the camera and posterboard. The projectile flight path should parallel the posterboard.

2. a. How are the ejecta paths through the air different from those during the vertical impact?

b. Sketch the crater, the path the material appears to take in the air, and the pattern of ejecta deposited on

the surface, based on the photographic record and your observations.
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Exercise Five: Comparative Cratering Processes

Sand Tray

Balloon Tightly

Clamped to

End of Hose

Bicycle Pump

Figure 5.4. Diagram showing the setup for photographing the explosive experiment.

Sketch area

Part B: Volcanic Explosive Cratering Process

Set up the equipment as shown in Figure 5.4. Place the bike pump where the person stood in Part A. Attach the

plastic tube to the bicycle pump. Check for air leaks. Next, pull the balloon tightly over the other end of the tube

and slip on the clamp. You are using only a small portion of the balloon and the balloon should burst easily when

the pump is used. Bury the tube in the sand but turn up its end in the center of the box so that it is almost vertical and about 2 centimeters below the surface of the sand. Smooth the surface of the sand over the tube. Start your

video or photographing and then give a quick, hard, single push of the bicycle pump. If the balloon did not burst,

check for air leaks or tighten the clamp on the balloon and try again.

3. a. Sketch the crater, the path the material appears to take in the air, and the pattern of ejecta deposited on

the surface based on the photographic record and your observations.

b. How does the resulting low-energy explosion crater compare with the impact crater?

Part C: Volcanic Eruptive Cratering Process

Remove the burst balloon and the clamp from the end of the tube. Rebury the tube in the sand, this time

without a balloon. Again make sure the end is turned up almost vertical in the center of the sand tray and that

it is only about 2 centimeters below the surface. Smooth the surface of the sand over the end of the tube. Start

video taping or photographing before pushing the pump. Do not push as hard as for the balloon. Push the

pump two more times for a total of three pushes.
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Five: Comparative Cratering Processes

4. a. Sketch the crater, the path the material appears to take in the air, and the pattern of ejecta deposited on the

surface based on the photographic record and your observations.

Sketch area

Compare the craters and features formed by each of the three processes.

5. a. How are all three similar?

b. How are they different?

c. Which craters have raised rims?

d. Which crater formed the widest ejecta pattern?

e. Which process affected the surrounding material most?

Examine Figures 5.5 and 5.6.

6. a. Which feature is probably volcanic in origin? Which feature is probably impact?

b. What evidence did you use to reach your conclusion?

c. If you were searching for a crater produced by an explosion, what features would you look for that

would distinguish it from a crater formed by volcanic eruption or impact?
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Exercise Five: Comparative Cratering Processes

Figure 5.5. Olympus Mons, Mars, showing the 80-km in diameter summit crater (arrow). North is to the top. (Viking

MDIM mosaic 211-5360.)

100 km

N
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Five: Comparative Cratering Processes

Figure 5.6. Timocharis, Moon. North is to the top. The crater is 33 kilometers in diameter. (Apollo 15 metric frame

AS15 0598.)

20 km

N
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Purpose

The objective of this exercise is to illustrate the

way in which planetary surfaces are modified by

multiple impacts and how surfaces can be dated

through analyses of craters. The effects of multiple

impacts and illumination angle are explored.

Materials

Per student group: watering can, duct tape, pin,

fine mesh screen, water, 4 large petri dishes, very

fine sand, portable light source (flashlight or flood

lamp)

Background

Impact craters are found on terrestrial planets

and nearly all satellites. Many surfaces have large

numbers of craters. This indicates that the surface is

very old, as it has accumulated craters over a long

time period.

This exercise demonstrates the effect of continuous cratering, using sand and ‘raindrop’ impactors.

Craters formed early will be degraded, or even

removed, by subsequent crater formation. After a

period of time the surface will reach equilibrium, in

which old craters are destroyed as rapidly as new

craters are formed. This exercise also explores the

effect of illumination angle in viewing and identifying craters. More detail is shown when the illumination angle is low and features cast shadows than

when the illumination angle is high. Advanced students and upper grades can attempt to answer the

optional starred (*) questions , which apply what

they have observed in this exercise and other general planetary background information to more complex planetary surfaces.

Figures 6.1 and 6.2 show sample experiments.

Science Standards

■ Earth and Space Science

• Earth’s history

Mathematics Standards

■ Geometry

Exercise Six: Impact Cratering on a Rainy Day

Exercise

Six

Instructor Notes

Suggested Correlation of Topics

Craters on the planets and satellites,

gradation, impact mechanics

Impact Cratering

on a Rainy Day

1.0 hours
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

1. a. During a slow, steady rain, many craters will

be similar in size.

b. Although craters typically are not clustered,

a few clusters may develop. They may overlap.

2. a. The large crater formed by the finger

becomes degraded (eroded) by the rain

impacts.

b. It becomes less sharp and distinct.

c. It would probably disappear.

d. There are more overlapping craters in this

dish.

3. a. The large craters become degraded (eroded).

Yes.

b. Tiny craters should be found in both dishes,

with the dish exposed for four minutes having

the greater number.

c. The change in appearance between the surfaces in these two dishes is not as distinct as the

change between the previous two surfaces.

Students may say the dishes appear almost

identical. The longer the surface is exposed to

cratering, the more difficult it becomes to distinguish the “age” difference between them (the

surfaces are approaching equilibrium). 

4. a. Small craters are nearly invisible. Little detail

visible.

b. Shadows help define many surface features.

Small craters are more obvious.

c. Shadows are long, hiding some small

craters.

d. Very long shadows. Edge of dish blocks the

view of some craters. 

5. a. A range of crater sizes in various states of

preservation; large number of craters per unit

area; similarity of terrain at different locations.

b. Younger; it is much less heavily cratered.

*c. 6.3 : mainly impact cratering, some volcanism in dark areas near limb. 6.4: volcanic plain

with relatively few impact craters.

*6. a. Surface features near the terminator are illuminated by low sun angle and show more

topographic detail. However, very near the

terminator less topography is discernible than

at a slight distance from the terminator. When

the shadows cover half or more of the crater

floor, the illumination is too low.

b. The surface near the limb is illuminated by

a nearly overhead sun and the craters appear

“washed out” (lacking detail); however, the

different albedo variations of the surface are

visible.

Answer Key

76 Exercise Six: Impact Cratering on a Rainy Day
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

Figure 6.1. Different sand surfaces

exposed for different lengths of time

to rain: 5 seconds (top), 30 seconds

(middle), and 2 minutes (bottom).

Exercise Six: Impact Cratering on a Rainy Day
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Six: Impact Cratering on a Rainy Day

Figure 6.2. Illustration of the effect of lighting angle on the identification of surface features. The craters are illuminated

from directly overhead (upper left), 60° from the horizontal (upper right), 30° from the horizontal (lower left) and 5° from

the horizontal (lower right).
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Exercise Six: Impact Cratering on a Rainy Day

Name

Exercise

Six

Impact Cratering

on a Rainy Day

Purpose

To learn how planetary surfaces are modified by

multiple impacts and how surfaces can be dated by

analysis of craters. In addition, to understand the

effects of illumination angle on the detection of

craters.

Materials

For each student group: Watering can, duct tape,

pin, fine mesh screen, 4 petri dishes, very fine sand,

flashlight.

Introduction

Impact craters are formed when meteoroids, asteroids, or comets impact planetary surfaces. As the

number of impact craters increases on a surface, the

appearance of the surfaces changes. After a period of

time, equilibrium is reached, in which old craters are

destroyed as quickly as new craters form.

Procedure and Questions

A. Place a piece of duct tape over the end of the watering can. Using the pin, poke one or two holes in the

tape. Fill the can with water, but don’t make it too heavy to hold for long periods of time. Fill each petri

dish with fine sand. Place one dish on the floor on top of a drop cloth or newspaper.

B. When making “raindrops” pour the water from the can very slowly, as single drops. Make each drop from

the can hit the mesh screen to break it into smaller drops. Move the screen so that the drops are hitting dry

screen as much as possible. As the holes of the screen fill with water, move the screen around so drops fall

on dry spots of screen. This activity works best if one person holds the watering can and a second person

holds screen. Holding the watering can at chest level, with the screen ~30 cm below the spout, “rain” on

the petri dish for about 5 seconds, or until several craters have formed.

1. a. How do the crater sizes vary?

b. Are the craters clustered together? Do they overlap?

Save all your “rained” on dishes for use in Question 4.

Make a crater in the second dish with your finger. Place this dish in the rain for approximately 30 seconds.

2. a. What does the surface look like?

b. What happened to the large crater you formed?
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Exercise Six: Impact Cratering on a Rainy Day

c. What do you suppose would happen to the large crater if you left it in the rain for 5 minutes (10 times

as long)?

d. Are there more or fewer overlapping craters here than in the first dish?

Make another “finger” crater in each of the other two dishes. Place one dish in the rain for two minutes; the

other for four minutes. Make sure you pour the water slowly or you will form a lake in the petri dish!

3. a. What has happened to the large craters? Does this agree with your prediction from question 2c?

b. Which dish has the most small craters?

c. Is there a marked difference between the two dishes, allowing you to easily tell which dish spent the 

most time in the rain?

The angle of illumination affects the visibility of surface features. Surfaces lit from directly overhead (noon

time) appear different from those lit at an angle, as during sunrise or sunset. Line up the four petri dishes with

their raindrop craters. Turn off the overhead lights. Use the flashlight and shine the light across the surface of the

dishes, estimating the illumination angle. Try shining the light from the following angles and describe what

you see. Examine the dishes from two locations—from the position of the flashlight and from directly above

the dishes.

4. a. 90° (directly above the craters)

b. 45°

c. 20°

d. 10°

Examine Figures 6.3 and 6.4.

5. a. Based on Figure 6.3, list the evidence you see on the Moon for long term impact cratering.

b. Is the surface shown in Figure 6.4 older or younger than the surface seen in Figure 6.3? How can you tell?
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*c. What geologic process(es) formed the surface seen in Figure 6.3? What process(es) formed the surface

seen in Figure 6.4?

Figure 6.3 shows both the limb and the terminator of the Moon. The limb is the horizon, seen in the upper left

corner. The terminator is the boundary between the day and night side, seen in the lower right. When examining spacecraft images, scientists are concerned with many aspects of the surface imaged. One aspect of interest

is topography, the ruggedness of the surface. Another aspect is albedo, a measure of how the surface reflects

light; albedo is a function of the composition and physical properties (such as grain size) of the surface.

*6. a. What part of Figure 6.3 gives the best topographic information? Is the illumination angle at this location

high or low?

b. What part of Figure 6.3 gives the best albedo information? Is the illumination angle at this location high

or low?

Exercise Six: Impact Cratering on a Rainy Day
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Figure 6.3. Photograph of the lunar highlands. Mare Marginis is the darker surface visible on the limb (lunar horizon,

upper left). (Apollo metric photograph AS16 3003.)

Exercise Six: Impact Cratering on a Rainy Day

100 km

N
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Figure 6.4. Photograph of lunar maria, looking south across Oceanus Procellarum. The large crater is Schiaparelli.

(Apollo metric photograph AS15 2617.) 

N 15 km

Exercise Six: Impact Cratering on a Rainy Day
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Earth is not unique in possessing an atmosphere. Venus, Mars, Pluto, and two of the

satellites of the outer planets—Titan (a moon

of Saturn) and Triton (a moon of Neptune) have

atmospheres that envelop their surfaces. In addition, the giant planets of the outer solar system—

Jupiter, Saturn, Uranus, and Neptune—are composed predominantly of gases. Other bodies in the

solar system possess extremely thin atmospheres.

Such bodies are the Moon (sodium gas), Mercury

(sodium gas), Europa (oxygen) and Io (sulfur).

The compositions of planetary atmospheres are

different, for a variety of reasons. First, surface gravity, the force that holds down an atmosphere, differs

significantly among the planets. For example, the

large gravitational force of the giant planet Jupiter is

able to retain light gases such as hydrogen and helium that escape from lower gravity objects. Second,

the distance from the sun determines the energy

available to heat atmospheric gas to a planet’s

escape velocity, the speed at which gas molecules

overcome a planet’s gravitational grasp. Thus, the

distant and cold Titan, Triton, and Pluto are able to

retain their atmospheres despite relatively low gravities. Finally, we know that the chemistry and geologic history are different for each planet. Because

atmospheric makeup is generally related to chemistry and temperature during planetary formation

and the subsequent escape of interior gases, the constituents and total pressures of planetary atmospheres are likely to be different. Moreover, on Earth,

atmospheric composition is largely governed by the

by-products of the very life that it sustains.

From the perspective of the planetary geologist,

atmospheres are important in the ways they shape

planetary surfaces. Wind can transport particles,

both eroding the surface and leaving deposits. Frost

and precipitation can leave direct and indirect

marks on a planetary surface. Climate changes can

influence a planet’s geological history. Conversely,

studying surface geology leads to an understanding of the atmosphere and climate of a

planet—both its present state and its past.

Unit

Three

Introduction to

Planetary Atmospheres
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Exercise Seven: Coriolis Effect

Purpose

The objective of this exercise is to demonstrate

that an object which moves in latitude over the surface of a rotating planet experiences the Coriolis

effect, an apparent deflection of its path from a

straight line. Upon completion of this exercise the

student should understand the concept of the

Coriolis effect and be able to understand viewing an

event from different frames of reference.

Materials

Suggested: lazy susan type turntable (must be

able to be rotated clockwise and counterclockwise),

paper, tape, markers (3 colors)

Background

The Coriolis effect is caused by an “imaginary”

force but has very real effects on the weather of

Earth and other planets. On Earth, which spins

counterclockwise as viewed from above its north

pole, objects are deflected to the right in the northern hemisphere and to the left in the southern hemisphere. This deflection is only apparent, however, as

an observer watching from space would see the

object’s path as a straight line. It is because we are

viewing in the frame of reference of the rotating

Earth that we see the apparent deflection. 

This exercise demonstrates the Coriolis effect by

using a rotating turntable. Students will draw

straight lines while spinning the turntable in different directions. To their surprise the resultant lines

will be curves on the paper covering the turntable.

This apparent deflection, the Coriolis effect, only

occurs in the frame of reference of the turntable. The

students, in a different frame of reference, know that

the path of the marker used to draw the line was

straight. On the sphere of the Earth, we occupy the

same reference frame as the motion, so we “see” the

Coriolis effect in action. To an outside observer, who

is occupying another reference frame, there is no

deflection and the motion is a straight line.

This concept has important implications for the

motion of ocean currents, storms on Earth, and even

missiles, but is unimportant at smaller scales. In

combination with pressure effects, the Coriolis

deflection gives rise to a counterclockwise rotation

of large storms, such as hurricanes, in the northern

hemisphere, and clockwise rotation in the southern

hemisphere. This could be illustrated to students

through pictures of hurricanes or other large storms

found in newspapers, magazines, or elsewhere in

this lab manual.

Students should work in pairs, one spinning the

turntable at a constant speed and the other marking

the line. Instructors should note that the spinning of

the Earth once a day on its axis is called rotation.

Students can experiment with rotating their

turntable faster or slower to see the effect on the

drawn lines. A faster spin will result in greater

deflection. If time or materials are a problem, this

exercise can be done as a demonstration by the

instructor. 

Vector motion of the surface of a sphere is complex. The magnitude of the Coriolis effect is controlled by rotation about the vertical axis. On Earth

the vertical axis of rotation is a line connecting the

geographic north and south poles. On a rotating

sphere, the maximum rotation is at the poles; there

is no rotation about the vertical axis at the equator.

To visualize this, imagine two flat disks glued onto

the surface of a sphere, one at the north pole and

one at the equator. As the sphere rotates, the disk at

Exercise

Seven Coriolis Effect

Instructor Notes

Suggested Correlation of Topics

Air and its movements, atmospheres, circulation of air or sea, meteorology, ocean

currents, physics: forces and mechanics,

planetary rotation

1.0 hours
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the north pole rotates around the vertical rotation

axis of the sphere. The vertical axis of the sphere is

also the axis of rotation of the disk. If viewed from

above, the disk spins in one spot, just as the sphere

does. The surface of the disk at the equator is parallel to the vertical rotation axis of the sphere. When

the sphere rotates, this disk revolves around the

axis. There is no spin or rotation of the disk at the

equator. The magnitude of the Coriolis effect

increases from the equator where it has no effect to

the poles. The turntable is equivalent to the disk at

the pole of the sphere, and illustrates the maximum

Coriolis effect. 

The Coriolis effect operates on Mars in a similar

way as on Earth. Because Mars rotates at about the

same rate and in the same sense as Earth, Mars has

large-scale weather systems just like on the Earth.

Students might try to predict the direction that the

Coriolis effect would deflect objects on Venus or

Uranus, which spin clockwise as viewed from

“above” (north of) the solar system. Advanced students and upper grades can answer the optional

starred (*) question, which applies their observations to more complex situations.

Science Standards

■ Earth and Space Science

• Origin and evolution of the Earth system

1. The line is straight. 

2. Unlike the real Earth, this model is not rotating. 

3. The line was deflected to the right. 

4. Counterclockwise. 

5. It would be deflected to the right.

6. It was deflected to the left.

7. Clockwise.

8. It would be deflected to the left. [The direction

of travel does not matter in the deflection, all

directions of travel are deflected to the right in

the northern hemisphere and to the left in the

southern hemisphere.]

9. Objects in the northern hemisphere are deflected to the right, while those in the southern

hemisphere deflect to the left.

10. The streaks form a curved path.

11. The streaks are curved because there is a

Coriolis effect on Mars. 

12. Yes; for there to be a Coriolis effect on Mars,

the planet must rotate.

13. The wind blew from the north.

14. The wind is being deflected to the left. 

15. Deflection to the left indicates we are looking

at the southern hemisphere of Mars.

*16. The Coriolis “force” is an imaginary force

because objects affected by it are really following a straight path. It is an apparent deflection

we see from the vantage point (frame of reference) of the rotating Earth. 

Answer Key

Exercise Seven: Coriolis Effect
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Name

Exercise Seven: Coriolis Effect

Purpose

By tracing an object as it moves across the surface

of a rotating and a non-rotating model, you will

demonstrate the true and apparent motions of

objects as they move across the real Earth. This

apparent motion is known as the Coriolis effect.

Materials

For each student group: Turntable which can be

spun both ways, paper, tape, colored markers (3)

Introduction

The Coriolis effect is the name given to the imaginary force that deflects objects, such as rockets or

large storms, which move over the surface of some

planets. It is important in causing the swirling

motion of storms, including hurricanes. The Coriolis

effect occurs on Earth and other planets because the

planets rotate.

Exercise

Seven Coriolis Effect

Questions

Cover the turntable with the paper, taping it to the edges of the turntable. Use one of the markers to draw

a straight line all the way across the turntable. This shows the path of clouds or objects moving on a non-rotating planet.

1. Observe and describe the shape of the line you drew. Looking down on your line, is it straight or

curved?

2. What is wrong with (missing from) this model of the Earth that might affect how objects truly move

over the Earth’s surface? 

Now spin the turntable counterclockwise. This is the direction that the Earth turns (or rotates), when

viewed from the north pole. The turntable is modeling the northern hemisphere of the Earth. Draw a straight

line across the turntable using a different colored marker, while spinning it at a constant speed. Be sure to

watch that your marker follows a straight path! Label the beginning of the line you drew with an arrow pointing in the direction the marker moved. Note that the line you drew is a curve.

3. With the starting point of the line directly in front of you, in which direction was line deflected? (Which

way does the arrow point—right or left?)

4. Which direction does the line curve (clockwise or counterclockwise)?
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Exercise Seven: Coriolis Effect

5. If you were in an airplane that takes off from Miami, Florida and is flying to Toronto, Canada, would

your plane be deflected to the left or to the right as it flew? 

Now spin the turntable clockwise. This is the direction that the Earth turns (or rotates), when viewed from

the south pole. The turntable is modeling the southern hemisphere of the Earth. Draw a straight line across the

turntable using a different colored marker, while spinning it at a constant speed. Be sure to watch that your

marker follows a straight path! Label the beginning of the line you drew with an arrow pointing in the direction the marker moved. Note that the line you drew is again a curve.

6. With the starting point of the line directly in front of you, in which direction was line deflected? (Which

way does the arrow point—right or left?)

7. Which direction does the line curve (clockwise or counterclockwise)?

8. If you were in a cruise ship that set sail from Cape Town, South Africa and was sailing for Rio de

Janeiro, Brazil, would your ship be deflected to the left or to the right as it traveled?

9. What is the difference between the way objects move over the Earth in the northern hemisphere compared with those in the southern hemisphere? 

Examine Figure 7.1, which shows part of Mars. The bright streaks associated with some craters can be used as

wind direction indicators. They are deposits of dust that can form downwind from craters. 

10. Does the group of streaks form a straight or a curved path (as a whole group)?

11. What does the shape of the wind streaks indicate about the existence of a Coriolis effect on Mars?

12. Does Mars rotate? How do you know?

13. From which way did the wind blow to make the streaks in Figure 7.1? 

14. Imagine you are on the part of Mars shown in this figure, standing with the wind to your back. Which way is

the wind being deflected, to your left or your right?

15. If Mars rotates in the same direction as the Earth (from west to east), is this a picture of the northern or southern hemisphere of Mars?

Optional Question

*16. Why is the Coriolis “force,” which causes objects to deflect from a straight path on a rotating planet, sometimes called an imaginary force?
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Exercise Seven: Coriolis Effect

Figure 7.1. Centered at 20 ̊, 250 ̊W, this mosaic is of a region on Mars called Hesperia Planum, site of much

aeolian (wind) activity. Note the bright streaks associated with some of the craters; they can be used as wind

direction indicators. North is to the top. Viking Orbiter mosaic 211-5478.

100 km

N
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Purpose

The objective of this exercise is to demonstrate

the fundamentals of atmospheric circulation as they

apply to Earth and other planets. Upon completion

of this exercise the student should understand the

fundamental controls on atmospheric circulation,

especially planetary rotation and the Coriolis effect.

In addition, the student will be able to make simple

weather predictions based on satellite photographs.

Materials

World map

Background

Earth’s weather patterns are complex, but some

basic meteorological concepts can be understood by

examining photographs of the Earth taken from

space. Furthermore, comparing Earth’s cloud patterns to those of other planets which have very different atmospheres—Mars, Venus, and Jupiter—

sheds light on some basic principles of atmospheric

circulation. 

A fundamental concept of this exercise is that air

moves from areas of high pressure toward areas of

lower pressure. An analogy can be made to water

flowing from a high pressure hose, or dye dissipating in water.

The simple Hadley cell circulation model of

Figure 8.1 introduces atmospheric circulation. The

pattern is driven by solar energy, which heats the

equatorial regions. As the planetary comparisons of

this lab indicate, rapid planetary rotation disrupts

this simple pattern into multiple circulation cells

and turbulent eddies. This occurs on Earth giving

rise to cyclonic storms, which are low pressure centers that result in inclement weather. The tilt of a

planet can also affect the atmospheric circulation

pattern, because the region of maximum solar heating will change with the season of the year. Venus

rotates very slowly (once in 243 Earth days) and is

tilted only 3° with respect to the plane of its orbit.

Thus, Venus has a relatively simple pattern of

atmospheric circulation which approximates a

Hadley cell.

The Coriolis effect, introduced in the previous

laboratory exercise, is an imaginary force that causes deflection of air parcels due to a planet’s rotation

(Figure 8.2). On a planet rotating toward the east

(such as the Earth and most other planets), this causes rightward deflection and counterclockwise rotation of winds in the northern hemisphere, and the

opposite effect in the southern hemisphere (Figure

8.3). The slow rotation of Venus makes the Coriolis

effect unimportant there. However, like Earth, Mars

has a 24 hour rotation period and the Coriolis effect

is important. 

To some students it will be readily apparent

which way a storm is spiraling. Others may first

want to sketch the spiraling clouds. If your pencil

moves clockwise as it moves in toward the center of

the spiral, then the clouds spiral clockwise, and vice

versa. This exercise calls on students to locate and

predict the weather in various cities around the

world. Using a world map to locate the cities and

then finding them on the Earth photo is a good lesson in geography. Additional cities can be added by

the instructor if time permits. 

Jupiter is a giant gas planet that has no solid surface; instead its atmosphere gets progressively

denser with depth. At great depth within the atmosphere the pressure is so tremendous that the gases

of the atmosphere are compressed into a liquid, and

Exercise Seven is suggested as an

introductory exercise.

Exercise Eight: Storm Systems

Exercise

Eight Storm Systems

Instructor Notes

Suggested Correlation of Topics

Air and its movements, air masses, atmospheres, Coriolis effect, cyclonic storms, geography, meteorology, rotation of planets, weather

forecasting, weather satellites, winds

1.0 hours
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below this is the solid core of the planet. Jupiter

rotates very rapidly, once in about 9 hours 55 minutes; Jupiter also has a large supply of internal heat.

These factors contribute to complex, turbulent flow

in the atmosphere. Neighboring bands in Jupiter’s

atmosphere typically have winds that blow in opposite directions. Vortices (spots) in the atmosphere

are generally not Coriolis-induced; instead they

develop along boundaries between bands as a result

of the opposing winds. Imagining that a storm

rotates like a pinwheel can help to reveal the directions that winds to either side are blowing. Most of

Jupiter’s spots are temporary features, appearing

and disappearing as winds and eddies shift slightly.

The Great Red Spot of Jupiter, observed from Earth

for more than 300 years, is a notable exception.

Science Standards

■ Earth and Space Science

• Energy in the Earth system

• Origin and evolution of the Earth system

1. a. It spirals counterclockwise. 

b. The Coriolis effect deflects any northern

hemisphere storm into a counterclockwise spiral. 

2. a. They spiral clockwise. 

b. The Coriolis effect deflects any southern

hemisphere storm into a clockwise spiral. 

3. The feature is a storm front, usually associated

with precipitation, wind, and cooler temperatures. 

4. a. Continued clouds and showers; cool. 

b. Continued clear and warm. 

c. Partly cloudy and hot. 

d. Increasing clouds with rain likely; cooler.

e. Continued clear and cool. 

5. The air pressure will decrease as the cyclonic

storm over the eastern United States, a center of

low pressure, passes through. 

6. a. It is a cyclonic storm. 

b. It must be in the northern hemisphere

because the clouds spiral counterclockwise. 

7. a. No. 

b. Venus has a more simple circulation pattern. 

c. Venus must rotate more slowly than the

Earth, because it does not show evidence for

Coriolis–induced storms. Also, its simple cloud

banding reflects a single equator-to-pole circulation cell. 

8. a. Jupiter rotates quickly. It shows well-defined

banding and a turbulent, complex pattern of

atmospheric circulation. 

b. The GRS lies in Jupiter’s southern hemisphere. 

c. Counterclockwise. 

d. No; the rotation is incorrect.

9.

Answer Key

Exercise Eight: Storm Systems
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Exercise Eight: Storm Systems

Name

Exercise

Eight Storm Systems

Purpose

By examining photographs of Earth, Mars,

Venus, and Jupiter, you will recognize wind circulation patterns and the influence of rotation and the

Coriolis effect on planetary atmospheres.

Materials

World map.

Introduction

Our lives are affected every day by the weather—

on some days more than others! Being able to predict

the weather is a convenience, but being able to predict

severe weather is important to public safety.

Furthermore, understanding the Earth’s weather patterns is critical to agriculture, transportation, and the

military. To gain insight into Earth’s weather and circulation patterns, it is useful to examine the atmospheres of other planets, comparing them to each other

and to Earth.

Atmospheric circulation is caused by differences in

heating, primarily between the poles and equator. On

an ideal non-rotating planet (Figure 8.1), warm air

would rise over the equatorial regions, lowering the

air pressure there. Air in each hemisphere would then

circulate to the cool polar regions where it would sink,

increasing air pressure there. To complete the cycle, the

cold high-pressure air would travel at ground level

back toward the equator. This simplified pattern of circulation is called a Hadley cell, named after the British

scientist who first proposed the model. On a real planet, the pattern of atmospheric circulation is complicated by rotation, which breaks the circulation into several cells from pole to equator and results in an everchanging pattern of turbulent swirling clouds, called

eddies.Also, if a planet is tilted with respect to its orbit

around the Sun, the latitude of maximum solar heating changes as the planet goes through its yearly cycle

of seasons. 

Air moves from regions of high pressure to regions

of low pressure. The pressure difference, or gradient, is

the driving force for atmospheric circulation.

However, other effects prevent the direct motion of a

given air mass from high to low pressure. Friction

between the ground and the atmosphere modifies air

motion, as does the presence of mountains or other

topography. Furthermore, the Coriolis effect deflects

air masses as they move. On a planet that rotates in the

normal sense (toward the east), a parcel of air is

deflected to the right of its direction of motion in the

northern hemisphere and to the left in the southern

hemisphere. Figure 8.2 shows this effect. 

Cyclonic storms are the fundamental mechanism

N

S

low pressure low pressure

high pressure

high pressure

Figure 8.1. The idealized Hadley cell model of atmospheric circulation. Although unrealistically simplified, this

pattern of airflow would develop on a planet if it were

spinning very slowly and if the axis were at right angles

to the orbital plane (that is, if there were no seasons). The

Sun would always heat the planet most strongly at the

equator. Air would rise along the equator and lower the

pressure locally. Colder, dense air would sink at the poles,

raising the air pressure there. This air would return

toward the equator along the ground. Rapid planetary

rotation breaks up this circulation pattern into several

cells and produces turbulent eddies. 
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for turbulent, inclement weather on Earth. These are

huge, well-organized centers of low pressure which

develop along the boundaries between air masses. As

a cyclone intensifies, so does weather activity along

the boundary, or front. In addition to its clouds, a

storm front commonly brings with it precipitation,

wind, and cooler temperatures.

The motion of air parcels on Earth generates such

low pressure centers. Air parcels can approach low

pressure cells from all directions. Because of the

Coriolis deflection, a circulation of winds is set up

around the low pressure centers (Figure 8.3). The

result is a counterclockwise spiral of air into a low center in the northern hemisphere, and a clockwise spiral

in the southern hemisphere.

Exercise Eight: Storm Systems

L

H

L

H

air parcel

pressure force

Coriolis “force”

L

H

time 1 time 2 time 3

pressure force

Coriolis “force”

pressure force

Coriolis “force”

Figure 8.2. As a small mass of air, called an air parcel, moves under the influence of a pressure gradient, its path is not

a direct one from high to low pressure. The curved lines around the low pressure centers (L) are contours of equal pressure, or isobars. The low pressure center can be considered a “well” or sink for air, and the high pressure center (H) can

be considered a “ridge” or source of air. If you were riding along an air parcel in the northern hemisphere, you would

be deflected to the right of your direction of motion as the air parcel drifts from high pressure toward lower pressure.

Thus, the final motion is nearly parallel to the isobars, rather than across them. In the southern hemisphere, the mirror

image of the diagram is observed, with the Coriolis “force” causing air parcels to deflect toward their left. 

Procedure and Questions

Examine Figure 8.4, using the world map to help identify the land masses that are visible.

1. Notice the well-defined spiral pattern of clouds southwest of the Baja peninsula, Mexico. 

a. Which way is this cloud pattern spiraling, clockwise or counterclockwise?

b. Why?

2. Now examine the two cloud spirals over the southern Pacific Ocean.

a. Which way are these clouds spiraling, clockwise or counterclockwise?

b. Why?

3. Notice the long line of clouds stretching over the southern Pacific Ocean. What is this feature and what kind

of weather is likely associated with it?
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Exercise Eight: Storm Systems

counterclockwise

wind circulation

rightward

deflection

Northern Hemisphere

L

clockwise

wind circulation

leftward

deflection

Southern Hemisphere

L

Figure 8.3. A simplified illustration of how low pressure cells (cyclones) develop. Air parcels

heading toward lows are deflected by the Coriolis effect to set up a counterclockwise circulation

pattern in the northern hemisphere, and a clockwise pattern in the southern hemisphere.

4. As Earth rotates from west to east, frictional drag pulls the atmosphere along more slowly in the same direction. Assuming that the storm system off of southern Chile will reach the coast by tomorrow, and noting that

this photo was taken in September, determine a likely weather forecast (temperature, clouds, and precipitation) for the next 24 hours in each of the following locations:

a. Indianapolis (40°N, 86°W)

b. El Paso (32°N, 106°W)

c. The Galápagos Islands (0°N, 91°W)

d. Tierra del Fuego (54°S, 68°W)

e. Buenos Aires (34°S, 58°W)

5. Will the air pressure become higher or lower in Bermuda during the next 24 hours? Explain. 

6. Look at Figure 8.5, taken by a spacecraft in orbit over Mars. Like Earth, Mars rotates west to east. 

a. What do you think this cloud feature is?

b. In what hemisphere is the feature? How do you know?
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Exercise Eight: Storm Systems

7. Examine the atmosphere of Venus as seen in Figure 8.6. 

a. Can you identify any obvious spiraling clouds that might be due to the Coriolis Effect?

b. Compare the photos of Venus and Earth, and recall the simple Hadley cell circulation model of Figure 8.1.

Does Venus appear to have a more simple or more complex pattern of atmospheric circulation than Earth?

c. How does the circulation pattern support the proposition that Venus rotates slowly?

Jupiter is a gaseous planet, having no solid surface (but likely possessing a solid core). Although the planet is

composed mostly of hydrogen and some helium, its visible clouds probably consist of ammonia (NH4), ammonium hydrosulfide (NH4HS), and water (H2O). The Great Red Spot (GRS) is a great storm in the clouds of Jupiter.

8. Base your answers to the following questions on the Voyager photos of Jupiter shown in Figures 8.7 and 8.8. 

a. Does Jupiter rotate quickly or slowly? Justify your answer. 

b. Does the GRS lie in the northern or southern hemisphere of Jupiter?

c. In which direction do winds around the GRS rotate?

d. Is the GRS a Coriolis-induced storm? Support your answer. 

9. The winds of Jupiter commonly blow in opposite directions in neighboring bands. That is, winds blow to the

east in one band and to the west in the neighboring band. These opposing winds can act to create swirling

eddies and storms. Draw a sketch of the GRS. Indicate with arrows the directions that winds along its northern and southern edges are blowing.

Sketch area
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Exercise Eight: Storm Systems

Figure 8.4. Earth as seen from the Geostationary Operational Environmental Satellite, GOES-7. The picture was taken

at 6 p.m. Greenwich Mean Time on September 25, 1994, soon after the start of northern hemisphere autumn. The north

pole is toward the top.
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Exercise Eight: Storm Systems

Figure 8.5. Viking Orbiter image 78A42, showing a water frost cloud pattern over the surface of Mars. North is

toward the top.

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Exercise Eight: Storm Systems

Figure 8.6. Patterns of cloud motion on Venus are revealed in this ultraviolet image, taken by the Pioneer Venus orbiter in

1979. Venus is unusual in that the planet and its atmosphere rotate from east to west. The surface of Venus cannot be seen

through the thick clouds. North is toward the top; the horizontal black line is missing data. Pioneer Venus image 0202-79-

046-0830, courtesy of Larry Travis.
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Exercise Eight: Storm Systems

Figure 8.7. Jupiter as seen

by the Voyager 1 spacecraft

from a distance of 54 million km (34 million miles),

as it approached the planet

on January 9, 1979. The

Great Red Spot (GRS) is a

large vortex just below center. North is toward the top.

Figure 8.8. Closeup of the Great Red Spot (GRS) seen by Voyager 1 on February 25, 1979 from a distance of 9.2 million km (5.7 million miles). The spot is about 25,000 km (16,000 miles) across, and could hold two Earths side-by-side.

White ovals and turbulent, swirling eddies are also visible.

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Purpose

The objective of this exercise is to demonstrate

the process of wind erosion and deposition around

surface features such as hills and craters.

Materials

■ 3-speed fan

■ 6-foot-long table (or longer)

■ chair

■ drop cloth

■ sugar (5-pound bag); very fine sand can be

substituted

■ small ball (tennis or racquet ball)

■ drinking glass

■ metric ruler

■ pencil

■ tape

■ ribbon or string (approximately 15 cm-long)

■ 3 to 5 obstacles, different sizes and types;

rocks, ruler, key, etc.

This exercise works well for groups of students.

In addition, it can be a demonstration by the instructor. This exercise is only a general simulation of the

complex interaction of the wind and a planetary

surface. The wind produced by the fan has a “spin”

to it because of the fan blades. For increased simulation accuracy, the wind can be stabilized by

removing the “spin”. To stabilize the wind, an open

gridwork, such as toilet paper tubes glued together,

must be placed between the fan and the experiment.

Because the gridwork will slow the wind, as well as

stabilize it, higher fan speeds will be necessary for

material movement. Commercial three speed fans

may not have sufficient wind velocities. Sugar is

much easier than sand to move with the wind velocities produced by a commercial fan. Both materials

are messy to work with, so have a dust pan and

broom on hand.

For more accurate simulation of the effects of

wind on planetary surfaces, it is recommended that

a wind tunnel be constructed. The directions for

constructing a wind tunnel are included here. The

construction of the wind tunnel is time consuming,

but can be used for quantitative experiments, or for

science-fair projects.

Wind Tunnel

Materials:

1. Wardrobe box from a moving company

2. 3-speed 50 cm box fan

3. Wind stabilizer (open ended milk cartons or

cardboard tubes glued together along their

lengths)

4. Base for inside box, approximately 15 cm

high and 50 cm wide

5. Masking tape

6. Clear plastic wrap (for the side ‘windows’)

7. Sand collection tray (such as a kitty litter

box)

8. Dark-colored posterboard

Construction:

Figure 9.1 shows the set-up for the wind tunnel.

Moving company wardrobe box (or similar size box

61 cm x 50 cm x 122 cm) is kept intact (do not

Exercise Nine: Aeolian Processes

Exercise

Nine Aeolian Processes

Instructor Notes

Suggested Correlation of Topics

Aerodynamics, air and its movements,

arid lands, climate, deserts, environments,

erosion, landforms, meteorology, weather, wind

and its effects

1.0 hours
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remove the flaps). Three windows are cut out, one

on each side and one on the top. The two side windows are sealed with clear plastic wrap (or clear

acrylic panels) and taped from the inside. The width

of the plastic wrap determines the height of the window. A convenient length is 40 cm. The top window

is left unsealed so that you can look more closely at

the sand crater and perhaps take pictures during

different stages of the experiment. A base is placed

on the floor of the wind tunnel in order to raise the

floor area to nearer the center of the fan. Fifteen centimeters above the floor is sufficient. The base

should fit snugly within the tunnel, to help stabilize

the box and to prevent the base from being moved

by the wind from the fan. The sand collection tray is

placed behind the base to catch some of the sand or

sugar. The posterboard is placed on top of the base

and should be taped down along the sides to prevent it from becoming airborne during the experiment. The wind stabilizer is placed directly against

the base within the tunnel and the fan is placed

immediately behind the wind stabilizer. The fan

should be within the flaps at one end of the box, and

directed to blow into the tunnel.

Science Standards

■ Earth and Space Science

• Energy in the Earth system

• Origin and evolution of the Earth system

Exercise Nine: Aeolian Processes

kitty litter tray

poster board

and base

box fan wind stabilizer

window

window

Placement of elements in wardrobe

box, with flaps left open at ends.

Figure 9.1. Diagram of wind tunnel construction.
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Exercise Nine: Aeolian Processes

1. Sketch of cone 

2. Answers will vary, depending on fan speed

and material (sugar or sand) used. Usually

travels entire distance of table and beyond (a

meter or more).

3. Answers will vary, but may see a sheet of

sugar/sand with ripple-like features developing perpendicular to the wind direction.

4. Answers will vary, depending on fan speed

and material used. Usually 1/3 to 1/2 meter

for the initial bounce. The second one is shorter (less energy).

5. Answers will vary, depending on fan speed

and material used. Usually a few centimeters.

6. Sketch (NOTE: sketches are not provided

within this answer key, as the variation in fan

velocities will control the speed of erosion and

deposition).

7. Sketch

8. Erosion occurs at the front and sides of the

cone.

9. Deposition occurs behind the cone.

10. The sketch below represents the aerodynamic

characteristics of a crater when wind blows

across it from left to right. Experiments to

visualize this model were done at the NASA

Ames Research Center. For a cone, the reverse

flow (seen within the crater) does not occur.

11. Sketch

12. Depending on the shape and positioning of the

obstacles, sugar will initially pile up against

the obstacle (on the front and sides), some

sugar will also be deposited behind each

obstacle. With time the sugar will be removed

from the front and sides, but will remain in the

lee of (behind) each obstacle. For discussion,

talk about windbreaks, such as snow fences,

and other obstacles man puts in the path of the

wind to control drifting sand and snow.

13. Sketch

14. Sketches, see answer 10 above for wind movement arrows.

15. Students should see sugar within the crater

moving from the back of the crater towards the

front (reverse flow). Once the back rim of the

crater has been removed by erosion this

motion will decrease dramatically and may

not be observed by the student.

16. Sketches, see answer 10 above for wind movement arrows.

17. Answers will vary, should be the same for both

crater shapes.

18. a. Answers will vary, but should have produced something similar to the windstreaks

seen in the figure (most likely during Part

Two).

b. The average prevailing wind has come from

the east (from right to left).

c. The bright crater tails are most likely depositional zones of bright surface materials.

Answer Key

Point of

Attachment

Reverse Flow

Deposition

Reverse Flow

Shadow Zone

Vortex Core
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Purpose

In this experiment you will investigate the

process of wind erosion and deposition around features such as craters and hills.

Materials

For each student group: 3 speed oscillating fan,

long table, chair, drop cloth, sugar, small ball (tennis

or racquet ball), drinking glass, metric ruler, pencil,

tape, ribbon or string (~15 cm long), 3 to 5 obstacles

(small rocks, keys, ruler, eraser, etc.).

Introduction

Wind is an important agent of gradation in many

arid and coastal regions of the Earth and on Mars

and Venus. During wind erosion, small particles are

moved in suspension, saltation, or traction. Very

small particles can be carried by the wind without

touching the ground until the wind slows or stops

and drops the particles. This is termed suspension.

Most sand (and sugar) sized particles are bounced

along the surface. This is termed saltation. Particles

too large to be picked up by the wind or bounced

along the surface may be pushed along the surface

by the wind or by the impact of particles in saltation. This is termed traction. Eventually the particles

are deposited by the wind in some new location.

Wind erosion and deposition of particles result in

distinctive landforms, such as dunes and windstreaks. Venus and Mars have wind related features

similar to those seen on Earth.

Sand or Sugar

Exercise Nine: Aeolian Processes

Figure 9.2. Diagram of the experimental set-up.

Drop Cloth

Name

Exercise

Nine Aeolian Processes

Procedure and Questions

Place the fan on the chair, centered at the end of the table. Make sure the center of the fan is even with the

surface of the table (see Figure 9.2). Direct the wind by tilting the fan towards the surface of the table at an

angle of 15 to 20 degrees from vertical. Tape a piece of ribbon or string on the end of a pencil. Turn the fan on

medium speed. Holding the pencil perpendicular to the surface of the table with the string along the table,

move the pencil around the table to locate the “dead spots” produced by the fan. Locate the area near the fan

where the air movement is greatest; this spot is where all sand piles should initially be placed. 

Part One

Form a 5 centimeter high cone of sugar in the identified spot. Make an initial sketch of the top view and

side view of the cone in the space provided.

1. Initial Sketch (use Sketch Area A):

Turn on the fan at a speed (usually medium) that results in moderate movement of material. Leave the

fan on for three minutes. Answer the following questions while the fan is blowing.

2. How far down the table surface has the sugar traveled after one minute?
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Exercise Nine: Aeolian Processes

Sketch Area A

3. Describe the pattern the sugar has formed at the far end of the table after 2 minutes.

4. What is the average length of the bounce of a sugar grain leaving the cone of sugar? Is the second

bounce of a sugar grain longer or shorter than the first bounce?

5. How high above the table does the sugar rise (in centimeters).

After three minutes turn off the fan and make a sketch of the cone. Include both a top and side view.

6. Second Sketch (use Sketch Area A):

Turn the fan back on for another two minutes. Be sure to note the saltation of the sugar grains at the far end

of the table. Sugar from the cone will hit sugar grains on the table and make them move along in saltation or

traction. After two minutes turn the fan off and make a final sketch of the top and side views of what

remains of the cone of sugar.

7. Final Sketch (use Sketch Area A):

Compare your previous two sketches with the final one.

8. From where has most of the sugar been eroded on the cone?

9. Has any sugar been deposited around the cone? If so, where?
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Exercise Nine: Aeolian Processes

10. Based on your three sketches of the sugar cone, diagram the effect the cone has on the wind movement. Do this

by imagining you can see the wind. Draw arrows to show how you think the wind moves around the cone.

Part Two

Clean up all the sugar on the table. Form another 5 cm high cone of sugar in the spot of greatest wind movement. Place obstacles (keys, small rocks, eraser, etc.) at different locations on the table downwind of the cone of

sugar. Place the obstacles at different orientations to the wind. For example, with a long side parallel, perpendicular or at an angle to the wind; flat or on its side. Turn on the fan at the same speed as in part one. After three minutes turn the fan off and observe the deposition and erosion of sugar around the obstacles.

11. Make a sketch (include both a top and side view) of each obstacle and the sugar surrounding it. Add arrows

to indicate the movement of the wind around each obstacle. (use Sketch Area B).

Sketch Area B

12. Where does most of the deposition occur at the obstacle? Where does most of the erosion occur?

Part Three

Remove the obstacles and clean up all the sugar on the table. Form a thin (few grains thick) layer of sugar

20 cm by 20 cm in size and make a 3 cm high cone of sugar in the center. Make sure the cone is in the spot of

maximum wind. Use the ball to form a bowl-shaped crater on the pile. Remove the ball and make an initial

sketch of the crater. Include a top and side view. 

13. Initial Sketch (use Sketch Area C):

In this part of the activity, you will be turning the fan on and off for three one-minute intervals to monitor the progress of erosion of the crater. Turn on the fan at the same speed used previously, producing

moderate movement of the sugar. After one minute, turn off the fan and observe what changes have

occurred to the crater and the surrounding area. Sketch what you observed. Include a top and side view,

as well as arrows indicating the wind movement over and around the crater.

14. a. Sketch after first one-minute interval (use Sketch Area C):

b. Sketch after second one-minute interval (use Sketch Area C):

c. Sketch after final one-minute interval (use Sketch Area C):

15. How is the movement of the wind around the crater different from the movement of the wind around

the cone in Part One?
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Part Four

Clean up all the sugar on the table. Form another thin layer of sugar 20 cm by 20 cm in size and make a 3 cm

high cone of sugar in the center. Make sure the cone is in the spot of maximum wind. Use the bottom of the drinking glass to form a flat-bottomed crater that goes all the way down to the table surface. Make an initial sketch of

the crater and its surroundings. Turn the fan on and off for three, one-minute intervals and sketch what you

observe. Include top and side view, as well as arrows indicating the wind movement over and around the crater.

(Use Sketch Area D, placing two sets of sketches in each box provided.)

16. a. Initial Sketch (use Sketch Area D):

b. Sketch after first one-minute interval (use Sketch Area D):

c. Sketch after second one-minute interval (use Sketch Area D):

d. Sketch after final one-minute interval (use Sketch Area D):

17. Based on your observations and sketches, are there any differences in erosion and deposition of sugar

between the bowl-shaped crater and the flat-bottomed crater? If yes, explain.

Exercise Nine: Aeolian Processes

Sketch Area C
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Sketch area D

Exercise Nine: Aeolian Processes

The wind is at work on other planetary surfaces besides Earth. Examine the photograph of Mars (Figure 9.3). 

18. a. Do you see anything similar to what you produced on the table?

b. From which direction do you think the wind was blowing?

c. Are the light areas behind the craters zones of erosion or deposition? Recall the obstacles in Part Two.
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Figure 9.3. Wind streaks on Mars located on plains between Tartarus Montes and Orcus Patera. The picture center is

approximately 19°N, 183° W. North is to the top. Viking Orbiter photograph 545A52.

Exercise Nine: Aeolian Processes

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The three decades from the mid-1960s to the

mid-1990s have revolutionized our understanding of the planets and their satellites.

During this period, spacecraft made an initial reconnaissance of all of the planets except Pluto, returning a wealth of information, much in the form of

images. The surfaces revealed in these images range

from the subtly familiar, such as the riverlike valleys

of Mars seen by the Viking Orbiters, to the wildly

exotic, like the ice cliffs of Miranda, a satellite of

Uranus.

What we understand of the histories of the planets and their satellites is based on observations of

their surfaces. For example, Mars shows a myriad of

landforms that were shaped by running water in the

past, even though liquid water is not stable near the

surface of Mars today. Thus, planetary scientists

conclude that Mars had a wet early history, and that

its climate somehow evolved to make Mars the

frozen desert that it is today. Many of the icy satellites of the outer solar system show evidence for

extensive flows of icy material, even though these

moons are frozen solid today. Thus, some energy

source increased the internal temperatures of these

satellites in the distant past. 

This unit introduces students to the interpretation of geologic landforms and processes on the

planets and satellites through five exercises. First,

the overall geology of the terrestrial planets is introduced. Then, individual activities concentrate on

the geology of Mars and Venus. Next, students are

led through the outer solar system using some of the

spectacular images from the Voyager mission.

Finally, the types of landforms and processes introduced in preceding activities are reviewed through

analysis of stereoscopic planetary images.

Unit

Four

Introduction to

Planetary Surfaces
Purpose

The objective of this exercise is to recognize and

compare the similarities and differences among the

surfaces of the terrestrial planets at a global scale.

Materials

Suggested: clear acetate or overhead transparency film, overhead projector markers, metric ruler,

drawing compass (a single compass can be used by

a group of students).

Substitutions: tracing paper, colored pens or pencils, pen and string (as a compass).

Background

This exercise views Mercury, Venus, Earth, Moon,

and Mars at the global scale. At this scale only the

largest and most prominent landforms and terrains

are visible. This provides a starting point for more

detailed study of planetary surfaces in later exercises or as provided by the instructor. Note that the

Moon, although not actually a planet, is typically

grouped with the terrestrial planets when considering its geology. 

This exercise is best worked in pairs or small

groups of students. When the students are working

on question 16, encourage them to compare the

images side by side in ordering the surfaces from

least to most complex. The starred question can be

used for more advanced students or for class discussion.

Science Standards

■ Earth and Space Science

• Origin and evolution of the Earth system

Mathematics Standards

■ Connections

■ Number and number relationships

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Exercise Ten:

Landform Mapping: The Terrestrial Planets

Exercise

Ten

Landform Mapping:

The Terrestrial Planets

Instructor Notes

Suggested Correlation of Topics

Planetary comparisons, geomorphology

1.5 hours

Exercise Two is suggested as an

introductory exercise.
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Exercise Ten:

Landform Mapping: The Terrestrial Planets

1. The highlands are bright, rugged and heavily

cratered. The plains are dark, flat, smooth and

less cratered.

2. The highlands.

3. The highlands.

4. Younger.

5. Cratered plains and rayed craters.

6. Older than the lunar plains. (Lunar plains are

often called maria.) 

7. All three surfaces have craters, although Mars

has the least. Mars has more extensive smooth

plains than the Moon or Mercury; no obvious

volcanoes or canyons are visible on either

Mercury or the Moon. Only Mars shows polar

ice caps.

8. Mars has a dynamic atmosphere (including

dust storms). Gradation by running water

occurred on Mars, but water never flowed on

the Moon. Volcanic activity has been more

extensive on Mars. Tectonism has occurred on

Mars. On the Moon, impact cratering and

plains volcanism have been the major geologic

processes; on Mars, all four major geologic

processes have worked to shape the surface.

9. Younger.

10. The southern region is older.

11. Mars.

12. a. Both are long and relatively narrow. The

canyon on Mars is straight, the one on Venus is

arcuate. [If the student says the Venus canyon

is bright and the Mars canyon is dark, remind

them of the differences in imaging systems:

radar vs. optical camera.]

13. Younger. 

14. a. Smooth plains, canyons (deep ocean trenches and rifts in Africa), volcanoes (represented

by islands) and rough “highlands” (mountain

ranges).

b. Continents, mid-ocean rift/ridge zones.

15. a. Similarities: if Earth’s continents are thought

of as “highlands,” both can be divided into

high– and low-standing regions; low-lying

regions are relatively smooth. Differences: the

Moon is dominated by craters; lowlands on

the Moon are formed by large impacts flooded

by volcanic material; no linear mountain chains

on the Moon; no prominent arcuate ridges or

trenches on the Moon. 

b. Students will have difficulty finding any

similarities between Earth and Mercury.

Differences: Mercury is dominated by craters

(impact cratering is the prominent geologic

process); on this image of the Earth, impact

cratering is the only geologic process that is not

apparent.

c. Similarities: both have volcanic and tectonic

landforms. Differences: no continents or midocean ridge system on Mars, no craters seen on

this global view of Earth.

d. Similarities: both show arcuate mountain

ranges; both show expansive smooth regions;

neither shows very large craters. Differences:

more extreme topography on Earth, continents

and deep ocean basins, compared to more uniform topographic level on Venus; no midocean ridge systems on Venus. 

16. a. Oldest to youngest: Mercury, Moon, Mars,

Venus, Earth.

b. Answers will vary based on students perception of “most complex.” Earth has the most

active geologic history reflected on its surface,

however, some students may argue that Venus is

more complex. Least to most complex: Mercury,

the Moon, Mars, Venus, Earth. 

17. (This representation is ~1/3 the size of what

student answer should be.)

*18. Answers may vary. In general it is true that the

larger the terrestrial planet, the more complex

its surface. This is not strictly true, however:

the Moon, despite its smaller size, is arguably

more complex than Mercury. Students might

wish to debate the relative complexity of Earth

and Venus, or Venus and Mars, as seen at the

global scale.

Answer Key

Moon Mercury Mars Venus Earth
Purpose

To examine and compare global-scale surfaces of

the terrestrial planets.

Materials

Clear acetate, overhead projector markers, metric

ruler, compass.

Introduction

At a global scale, only the largest planetary landforms and regions are visible and can be identified.

Such landforms include large volcanoes, canyons,

impact craters, plains regions, mountains, and highlands (topographically “high standing” regions).

Although the Moon and planets formed at the same

time (about 4.5 billion years ago) their surfaces differ in age. This difference is due to variation in the

levels of geologic activity on each body since their

formation. The four main geologic processes (volcanism, tectonism, gradation, and impact cratering) have worked to alter the original surfaces. In

comparing planetary surfaces, relative ages are usually determined from impact craters. In general,

older surfaces show more craters, larger craters, and

more degraded craters than younger surfaces.

Exercise Ten:

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Name

Exercise

Ten

Landform Mapping:

The Terrestrial Planets

Questions

Moon

Examine Figure 10.1. Place a piece of clear acetate over the photo. Trace the outline of the Moon. Divide the Moon

by its two major regions—highlands (light) and plains (dark)—by outlining the light-toned and dark-toned areas.

On the Moon, the plains are called “maria” (which means “seas” in Latin) for their fanciful resemblance to oceans.

1. Describe the characteristics of each region.

2. Which of the two regions appears to be most heavily cratered?

3. Which region on the Moon is older—the plains or the highlands?

4. Some large, young craters have bright ejecta deposits that form a star-like pattern of rays around them.

Trace two such craters and their deposits onto your acetate map. Are these craters older or younger than

the plains?

Mercury

5. Examine Figure 10.2. What landforms and regions do you observe on Mercury?
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Exercise Ten:

Landform Mapping: The Terrestrial Planets

6. Based on the number of craters, do you think the surface of Mercury is older, younger, or about the same age

as the plains on the Moon?

Mars

Examine Figure 10.3. Mars has a thin atmosphere, seasonal dust storms and polar ice caps (notice the bright

south polar ice cap near the bottom of the figure). At one time, Mars had liquid water on its surface, although today

Mars is too cold to have liquid water and only has ice. The darker spots within the bright region of the upper left

of the image (marked A–D) are large volcanoes. Images sent back from surface landers and other remotely acquired

data show that the lighter toned areas are relatively dusty and the darker toned areas are sandy or bare rock. Near

the center of the image is Valles Marineris (marked E), a large canyon system of probable tectonic origin.

7. List similarities and differences in the features found on Mars compared to those on the Moon and Mercury.

8. Why is the surface of Mars different from the Moon? (List reasons that support your answer.)

9. Based on the number of impact craters, do you think the surface of Mars seen here is older, younger, or

about the same age as the highlands on the Moon?

10. Based on the number of impact craters, which part of Mars is older, the northern or the southern region?

Venus

Although the atmosphere of Mars is relatively cloud free, the thick cloud cover on Venus completely hides the

surface from viewing by cameras. Using radar, which can penetrate through clouds, the Magellan spacecraft sent

back radar images of the surface of Venus. In general, these radar images show rough topography (such as mountains, rift zones, crater rims and ejecta) as bright, and smoother material (plains) as dark. A volcano (A), a crater

(B), and a canyon (C) have been labeled on the image.

11. Which planet looks more like Venus at the global scale: Mercury or Mars?

12. Compare Valles Marineris on Mars to Artemis Corona (the canyon marked C) on Venus. How are their

morphologies the same? How are they different?

13. Based on the number of craters, do you think the surface of Venus is older, younger, or about the same age

as the highlands on the Moon?

Earth

Figure 10.5 shows a digital representation of the Earth, shown as it might look from space if it had no clouds

and no oceans. In this way, Earth’s landforms can be compared to those of other planets.

14. a. List some major landforms on Earth that are comparable to what you have seen on the other planets.

b. List some different types of landforms you can see.
Exercise Ten:

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15. List some similarities and differences between the landforms of the Earth and:

a. Moon

b. Mercury

c. Mars

d. Venus

16. Based on the number of craters, the number of geologic processes evident and the different types of landforms seen on the images, list the five surfaces you have examined in order :

a. From oldest to youngest.

b. From least complex to most complex.

17. Examine the table on the next page. Using a compass, draw circles showing the relative sizes of Mercury,

Venus, Mars, the Moon, and Earth in the sketch area below. Let the diameter of Earth equal 6 cm.

Sketch area
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Mercury Venus Earth Moon Mars

Mean Distance from 57.9 108.2 149.6 384,400 km 227.9 Sun (millions of km) from Earth

Equatorial Diameter 4880 12,104 12,756 3476 6787 (km)

Equatorial Diameter 0.38 0.95 1.000 0.272 0.53 (Earth diameters)

Mass (relative to 0.055 0.815 1.000 0.0123 0.108 Earth)

Volume (relative to 0.06 0.88 1.000 0.0203 0.15 Earth)

Density (g/cm3

) 5.4 5.2 5.5 3.34 3.9

*18. Before the initial reconnaissance of the solar system by spacecraft was completed, it was traditionally

believed that the geological complexity of surface features on a solar system body would be related to

the size of the body, larger planets being more geologically complex. Is this true of the terrestrial planets? Support your answer.

Exercise Ten:

Landform Mapping: The Terrestrial Planets
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Landform Mapping: The Terrestrial Planets

Figure 10.1. Photograph of the Moon. North is to the top. (Courtesy of Ewen A. Whitaker, University of Arizona.)
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Exercise Ten:

Landform Mapping: The Terrestrial Planets

Figure 10.2. Mariner 10 mosaic of Mercury. North is to the top. (NASA P-14580.)
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Exercise Ten:

Landform Mapping: The Terrestrial Planets

Figure 10.3. Viking Orbiter global mosaic of Mars, centered at -30°, 90°. North is to the top.

(Courtesy U.S. Geological Survey, Flagstaff, Arizona.)

A B

C

D E
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Exercise Ten:

Landform Mapping: The Terrestrial Planets

Figure 10.4. Magellan radar mosaic of Venus. North is to the top. The smooth gray and black sections at the bottom of

the figure are portions of the south pole that were not imaged by the spacecraft. (NASA P-39225.)

A

B

C
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Exercise Ten:

Landform Mapping: The Terrestrial Planets

Figure 10.5. Global representation of the Earth in which higher standing topography is shown as brighter, centered at

0°, 50°. North is to the top. (Courtesy U.S. Geological Survey, Flagstaff, Arizona.)
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Exercise Eleven: Geologic Features of Mars

Purpose

By examining images of martian surface features,

students will learn to identify landforms and interpret the geologic processes which formed them.

Background

To perform this exercise students should have been

introduced to the four geologic processes—gradation,

impact cratering, tectonism, and volcanism.

In many ways Mars is similar to Earth. Martian

volcanoes, although apparently extinct, are similar to

those on Earth. Mars does not experience plate tectonics like the Earth, but it does have familiar tectonic features, such as rift zones. Gradation on Mars is

also similar to the forms observed on Earth, although

liquid water is not stable on the surface of Mars

today. On Mars, as on most other worlds, impact cratering is much more conspicuous than on Earth. The

number, size, and freshness of craters, and their relation to other geologic features, can be used to determine the relative ages of Martian surfaces.

A more detailed description of the processes that

have acted on Mars is presented in the students’

introduction.

Science Standards

■ Earth and Space Science

• Energy in the Earth system

• Origin and evolution of the Earth system

• Earth in the solar system

Exercise

Eleven

Geologic Features

of Mars

Instructor Notes

Suggested Correlation of Topics

Mars, geomorphology, gradation, impact cratering, tectonism, volcanism

1.0 hours

Exercise Two is suggested as an

introductory exercise.
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Exercise Eleven: Geologic Features of Mars

1. It is approximately circular, but has numerous

over-lapping craters within it and at the margins.

2. Answers will vary, but should include: a) erosion, b) tectonism (faulting).

3. Geologically young because there are few

impact craters. Younger than the surface of the

moon.

4. Answers will vary. The sharp, straight cliffs and

the large dimensions suggest tectonic processes; the stream patterns on the south side are

indicative of modification by running water.

5. Ius Chasma is larger by several times.

6. a. Northeast (to the top of the photo).

b. Craters are numerous and degraded, indicating this is a relatively ancient region. 

c. The craters are older than the valleys which

cut across the center rims. However, there are

also a few fresh, young craters superposed on

the channels, indicating that these impacts

occurred after channel formation.

7. a. The diffuse streaks of bright material are

found on the southeast side of craters.

b. The wind blew from the northwest. 

8. a. Like Olympus Mons, Apollinaris Patera has

radial flow patterns and a basal scarp (cliff).

Apollinaris Patera has more craters, a large

flow trending to the south, and a less complex

caldera than that of Olympus Mons. Olympus

Mons is a much larger edifice. 

b. Volcanism, considering its characteristics

described above.

c. Impact formed Reuyl crater, indicated by the

ejecta pattern and central peak. 

d. Gradation by running water, indicated by

the meandering pattern and tributary channels.

e. Water that once flowed through Ma’adim

Vallis may have deposited sedimentary material onto the floor of Gusev crater.

9. Answers will vary. D, A (C), C (A), B. D is a

very old degraded crater. The flows from A are

modified at their southern part by sediments

from crater D due to flow of water in channel

C. So A preceded C. (This is very difficult to

see and students may reverse the order of

these two events.) Crater B is fresh in appearance—rim is not eroded—and thus is probably

very young.

Answer Key
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Exercise Eleven: Geologic Features of Mars

Name

Exercise

Eleven

Geologic Features

of Mars

Purpose

To learn to identify landforms on the surface of

Mars and the geological processes that produced

them.

Introduction

In many ways Mars is similar to Earth. The same

four geologic processes that shape Earth—gradation, impact cratering, tectonism, and volcanism—

have left their mark on Mars. Volcanism has produced vast lava flows, broad shield volcanoes, and

plains of volcanic material. Mars has some of the

largest volcanoes in the solar system, including

Olympus Mons, a massive volcano many times

larger than the Island of Hawaii. Olympus Mons is

only one of four huge volcanoes in a 3000 km-wide

region called Tharsis. These volcanoes erupted

repeatedly over many millions of years, growing

higher with each lava flow. Enormous collapse

calderas are found on the summits of each of the

volcanoes. 

Gradation is the dominant geologic process acting on Mars today. Mass movement is the displacement of material by landslides or slumping through

the action of gravity. Aeolian (wind) activity is also

a continuing process of gradation. Sand and dust

particles carried by the wind form dunes and windstreaks. Although temperatures below freezing and

low atmospheric pressures do not allow liquid

water on the surface of Mars today, gradation

processes involving running water were important

on Mars in the past. Valley systems cut through

many of the cratered terrains of Mars and have characteristics analogous to water-cut valleys on Earth.

A mystery concerning water on Mars is “Where did

it go?” Some water probably seeped into the ground

and is frozen there today as ice, and some likely

escaped into space over time. Moreover, the polar

caps contain some water ice. Mars, like the Earth,

has seasons. The polar caps shrink during local

summer and grow during local winter.

Although Mars does not have plate tectonics like

the Earth, there are many tectonic features that

show its surface has been deformed. Stresses can be

caused by subsurface uplift or by the addition of

mass (such as lava flows) that weigh down an area.

Extensional stresses have led to the formation of

great valleys such as Valles Marineris, the longest

canyon system in the solar system. 

As on the Moon, Mercury, Venus, and most of the

outer planet satellites, impact craters are found on

the surface of Mars. Craters can be used to determine the relative ages of martian surface materials;

in general, older surfaces have craters which are

more numerous, larger, and more degraded than

those on young surfaces. Moreover, the principles of

superposition and cross-cutting relations indicate

that a feature which at least partly covers another

feature is the younger. Thus, if a valley cuts through

a crater, the crater must be older. Individual craters

are degraded or destroyed over time by gradational

processes and further cratering. Therefore, crisp

craters with upraised rims and steep sides are

young, while less distinct and eroded craters with

partial rims are probably older. Through a combination of these principles, the relative ages of geologic

features can be determined, and a sequence of geologic events developed.
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Exercise Eleven: Geologic Features of Mars

Questions and Procedures

Examine Figure 11.1: Olympus Mons is a shield volcano 600 km in diameter, towering 25 km above the surrounding plain. Around its base is a steep cliff as high as 6 km. It has a summit caldera some 80 km wide.

1. Examine the caldera (labeled A) and describe its shape. 

2. Suggest some ways in which the scarp around Olympus Mons might have formed.

3. Do you think the surface of Olympus Mons is geologically old or young, compared to the surface of the

Moon? Explain your answer.

Examine Figure 11.2: Ius Chasma is part of the western end of Valles Marineris, the largest Martian canyon.

Smaller valleys join the main east-west chasm.

4. Which of the four geologic processes might be responsible for the formation of Ius Chasma?

5. Compare the size of Ius Chasma and its tributaries to the size of the Grand Canyon of Arizona. Which is

larger, and by how much?

Examine Figure 11.3: Valleys west of Chryse Planitia. Similar to some river systems on Earth, these martian

channels have a branching pattern.

6. a. In what direction did the water flow?

b. Based on the number and morphology of craters, is this a relatively old or young region of Mars?

c. Are the craters you observe older or younger than the valleys? Use the principle of cross-cutting relations to justify your answer. 

Examine Figure 11.4: The Hesperia region in the southern hemisphere consists of cratered plains which

have been modified by aeolian processes. Wind-produced features, called bright windstreaks, are associated

with many craters.

7. a. Describe the appearance and orientation of the windstreaks.
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Exercise Eleven: Geologic Features of Mars

b. If windstreaks are dust deposits formed downwind from the craters, what wind direction is indicated here? (Remember that wind direction refers to the direction from which the wind blows.) 

Examine Figure 11.5: Apollinaris Patera and surrounding region. All four geologic processes can act to

shape a planetary landscape. For the following, you will use the knowledge from previous questions to identify Martian landforms and describe the geologic processes that created them.

8. a. Compare Apollinaris Patera (marked A on Figure 11.5) to Olympus Mons (Figure 11.1). How are

they similar, and how are they different?

b. What process do you think formed Apollinaris Patera? How can you tell?

c. What process do you think formed Reuyl crater (marked B on Figure 11.5)? Justify your answer. 

d. Ma’adim Vallis is the channel in the southeast part of the photograph, marked C. Which of the four

processes do you think formed Ma’adim Vallis? Justify your answer. 

e. Consider the relationship between Ma’adim Vallis and Gusev, the 160 km diameter crater marked D.

What could be the origin of the material that comprises the floor of Gusev? (Hint: the region slopes

to the north.) 

9. Based on your observations, what is the probable order of occurrence of A, B, C, and D in Figure 11.5

(i.e., which came first, second, third, last)? Give evidence for your answer.
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Exercise Eleven: Geologic Features of Mars

Figure 11.1. Martian shield volcano, Olympus Mons. The summit caldera is about 80 km in diameter.

(Viking MDIM mosaic 211-5360)

100 km

N

A
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Exercise Eleven: Geologic Features of Mars

Figure 11.2. Ius Chasma, part of the Valles Marineris system. (Viking image 645A57.)

25 km

N
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Exercise Eleven: Geologic Features of Mars

Figure 11.3. Valleys on western Chryse Planitia near the Viking Lander 1 site. The large crater at left center is 28 km in

diameter. (Viking mosaic P-17698.)

10 km

N
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Exercise Eleven: Geologic Features of Mars

Figure 11.4. Hesperia Planum, showing bright windstreaks associated with some of the craters. Location: 24° S, 245° W.

North is to the top. (Viking MDIM Volume 4.) 

100 km

N
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Exercise Eleven: Geologic Features of Mars

Figure 11.5. Apollinaris Patera and surrounding region centered at 10° S, 190° W. (Viking MDIM Volume 4.)

A

D

C

B

50 km

N
Purpose

The objective of this exercise is to introduce the student to the remote sensing technique of radar imaging

and to introduce the surface features found on Venus.

Materials

Suggested: clear acetate or overhead projector film,

overhead projector markers, tape, 25 cm piece of string

Substitutions: tracing paper, pencil, ruler

Background

This exercise introduces the use of radar images

for geologic feature identification. Most people are

not familiar with radar as an imaging system.

Consequently, the student introduction contains

extensive information to aid in completing this exercise. With completion of the exercise, the student

should be able to recognize and identify some of the

major geologic features found on Venus and understand the use of radar as a remote sensing technique.

The explanation of radar and radar imaging in

this exercise is highly simplified, focusing only on

surface roughness. Factors such as wavelength, incidence angle, polarization and signal processing are

not presented, although these factors are very

important controls on the appearance of radar

images. Students may only be familiar with the use

of radar for weather satellites, air traffic control

monitors, and police speed guns. Air traffic control

radar and police speed guns work because the metal

in cars and airplanes is highly reflective at radar

wavelengths. Because radar is an active system (it

emits energy), it is not dependent on the sun or

good weather for use; it can be used at night and is

an important safety measure for air travel. Weather

satellite radar systems use relatively short wavelengths, small enough for individual ice crystals and

water droplets in clouds to reflect the signal back to

the satellite, producing the images we see on the

evening newscast. The Magellan spacecraft at Venus

used a longer wavelength system that penetrated

the thick cloud cover that shrouds the planet. 

The vertical stripes on some images of Venus

(most obvious in figures 12.4, 12.5 and 12.9) are artifacts of the Magellan imaging system. Each stripe

represents a single orbit of the spacecraft. Black

stripes are present where the spacecraft did not

image.

Teacher Recommendations

The instructor is encouraged to present the electromagnetic spectrum before working this exercise,

and to explain the radar part of the spectrum. The

exercise is divided into three parts. The first part

examines Venus features and asks the student to

answer questions based on the images. The second

part has the student identify various features within a region of Venus. The third part has the student

design a rover journey to some of the features identified in part two. The “rover” part of this exercise

will produce many and varied paths, depending on

features identified, features chosen for a rover visit,

and the rover starting point. The map in the answer

key identifies all the features students are asked to

locate, and includes two sample rover paths. The

test for rover path accuracy is in the distance used

(25 cm maximum) and whether the rover stays on

the dark (smooth) plains while traveling to the

selected features of interest. This exercise can be

Exercise Twelve: Geologic Features of Venus

Exercise

Twelve

Geologic Features

of Venus

Instructor Notes

Suggested Correlation of Topics

Venus geomorphology, impact cratering,

radar, remote sensing, tectonism, volcanism

1.0 hours

Exercise Two is suggested as an

introductory exercise.

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1. a. The ejecta, rim, and central peak consist of broken rock fragments and have a rough texture

which appear bright in the image. The crater

floor is smooth and appears dark in the image.

b. Feature A has a rough texture. 

2. Crater is older. It had to already be there to be

rifted by later tectonic activity.

3. No. The same tectonic activity that formed the

complex ridged terrain has not affected the

volcanic plains, meaning that the plains are

younger, and that either that style of tectonism

has ceased, or that it is episodic and has not

occurred since the plains were emplaced.

4. Almost all appear to have a central summit

crater, and to be cone shaped. Some are brighter

than others indicating differences in texture.

5. Flow textures are both rough (bright) and

smooth (dark). The flows have lobate outlines

and contain “feeder” channels (usually dark in

tone) that supplied the lava to the flow front. 

6. ~200 km in diameter

7. a. Flows are rough (bright on the image).

b. ~150 km

NOTE: On the student maps, they will label all

tectonic zones as “rift zones.” On the

answer key, these zones are marked as rift

zones, ridge zones, and fracture zones.

Ridge zones have positive relief, rift zones

have negative relief, and fracture zones

have not had any displacement (neither

positive nor negative).

Answer Key

Exercise Twelve: Geologic Features of Venus

done in groups or by individual students. A further

suggestion for this exercise is to plot all the rover

paths on a single page (or on an overhead projector

viewgraph) and have the class decide on the path

that is best, providing the most interesting scientific

results with the least risk to the rover. Such a discussion closely simulates planning meetings for

NASA missions. For further interdisciplinary application, rover groups could assign different tasks

within each group: someone to draw a picture of the

rover, someone to draw pictures of what the rover

might see, a science group to plan the rover path, a

“reporter” to write up a travelogue of what the

rover did and saw, and any other tasks that the students consider to be important to the mission.

Science Standards

■ Earth and Space Science

• Origin and evolution of the Earth system

Mathematics Standards

■ Measurement
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Exercise Twelve: Geologic Features of Venus

Name

Exercise

Twelve

Geologic Features

of Venus

Purpose

To learn about geologic features on Venus and the

use of radar images.

Materials

Clear acetate, overhead projector markers, tape,

25cm piece of string

Introduction

Radar is an imaging and detection system that

uses the microwave section (~1mm to ~1m wavelengths) of the electromagnetic spectrum. By

changing the wavelength used by radar, different

objects can be detected. Radar is an active system in

that the signal energy is transmitted from and

received by the instrument. Our eyes are a passive

system, we only receive reflected energy (as from

the sun or a light bulb). Because radar produces and

receives its own energy, it is not generally dependent on environmental conditions for its use. It can

be used during the day and at night, and because

radar wavelengths can penetrate clouds, it can be

used during most kinds of weather. 

All electromagnetic energy interacts with the

objects and surfaces it encounters by being

absorbed, transmitted, or reflected. We see only the

light that is reflected (bounced) toward our eyes.

The radar system will only “see” the radar waves

reflected back to the antenna (Figure 12.1). The more

energy reflected back to the antenna, the brighter

the tone created in the resultant image. In general,

smooth surfaces are dark in a radar image and

rough surfaces appear bright. One way to think

about radar is that it shows how the surface “feels”

(rough or smooth), whereas a conventional photograph shows how a surface “looks” (color and

brightness). Because we are not accustomed to

thinking about a surface in terms of its texture,

working with radar images can be difficult at first.

Figures 12.2 a and b show the same area of the

Mojave Desert of California. Figure 12.2a is a visible

wavelength Landsat satellite photo and 12.2b is a

Seasat radar image. The feature marked A is a lava

flow. In the Landsat photo it is dark, because the

rocks are dark in visual appearance; but on the

radar image the lava flow is very bright, because

the surface is very rough and scatters the radar

energy back to the antenna. The feature marked B is

a dry lake bed. In the Landsat photo it is light,

because the materials are light colored sands and

clays. In the radar image, the lake bed is very dark

and difficult to distinguish from the surrounding

dark area. This is because both the lake bed and the

surrounding sands are very smooth. Mountains

appear bright in the radar image. It is easier to distinguish mountains from the surrounding sand

deposits in the radar image than in the Landsat

photo. Because of the radar’s sensitivity to surface

texture, it is able to image structural features (such

as faults and fractures) that may be undetected in a

Figure 12.1. Diagram of radar reflectance and effect on

resultant image. Smooth surfaces reflect the incident

energy away from the antenna, producing a dark tone

(non-return) on the image. A rough surface scatters the

incident energy, some of which will be returned to the

antenna and produce a bright tone on the image.

Energy

Radar Antenna

Smooth

Surface

Intermediate

Surface

Rough

Surface

Resultant Image
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Exercise Twelve: Geologic Features of Venus

visible wavelength photo. Note that a cinder cone

within the lava flow (marked C) is easier to see in

the radar image than in the Landsat photo.

Radar was used to image the surface of Venus

because thick cloud cover makes the use of visible

wavelength imaging impossible. The Venus radar

images in this exercise were acquired by the

Magellan spacecraft, which orbited Venus from 1990

to 1994. The vertical black stripes on some images

are missing data, places where the spacecraft did

not image the surface.

Questions and Procedures

Part A

Figure 12.3 shows two impact craters on Venus. They are surrounded by smooth volcanic plains, which are

dark on the radar image. The crater rims are easily identified, as are the ejecta deposits. 

1. a. Describe the ejecta, rim, floor, and central peak of the smaller crater in terms of texture.

b. The ejecta of the larger crater is different from that of the smaller crater. Part of the ejecta of the larger

crater was molten, melted rock and formed flows. What is the texture of the ejecta flow labeled A?

The right side of Figure 12.4 shows a rift zone on Venus. Although the rift zone appears almost flat in the

image, the topography of this area is more like the Grand Canyon of Arizona, with steep cliffs and deep valleys. The other bright lineaments in this figure are fractures and faults. 

2. Note the crater at A. Is it younger or older than the rift? How do you know?

Figure 12.5 shows an area of “complex ridged terrain,” the term used for some mountains and highlands

on Venus. This area has been fractured, faulted, rifted, uplifted and surrounded by younger smooth (dark)

plains. The deformed area is very bright in the radar image because the complex structures have produced

very rough terrain.

3. Does the tectonic activity that formed the complex ridged terrain appear to have affected the volcanic

plains? What does this indicate about tectonic activity in this area and the age of the volcanic plains?

Figure 12.6 shows many small (1–10 km in diameter) volcanoes, constituting a “volcanic shield field.”

Volcanism has played a major role in the formation of the surface of Venus, and shield fields are common. 

4. List any similarities and differences among the individual volcanoes.

Most dark (smooth) plains on Venus are volcanic. However, not all volcanic flows on Venus are dark; some

are bright. Figure 12.7 shows an area of volcanic flows. 

5. Describe the field of flows shown in the image. Include information as to texture, outline, and any other

interesting features.
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Exercise Twelve: Geologic Features of Venus

So far all the figures have shown features that can be found on Earth as well as on Venus. Figure 12.8 shows

features that may be unique to Venus. Termed “coronae” (the singular is “corona”), these features are identified by circular sets of fractures. Some form low, circular domes that can have associated volcanic flows (for

example, the flows to the north and northwest of the corona marked A); or the centers may have subsided,

leaving bowl-shaped depressions, which can be filled by lava flows. Radial fractures commonly surround

coronae, giving a “buglike” appearance.

6. What is the diameter of the largest corona in the image?

7. a. Are the flows to the north and northwest of the corona labeled A rough or smooth in texture?

b. How far from the letter A did the volcanic material flow to the northwest?

Part B

Figure 12.9 shows part of the Carson Quadrangle of Venus, centered at 11°S, 345°E. The area shown is equal

to about two-thirds of the continental United States. All the types of features shown in the previous figures can

be found on this image; however, due to their small size, shield fields are very difficult to see. The black areas

are regions that were not imaged by Magellan. The bright circular spots are where meteoritic material struck

the surface without forming an impact crater. These are called “splotches.” Be sure to note the difference in

scale between this figure and the previous ones.

Tape a piece of clear acetate to the figure. Draw a box outlining the image. Trace the scale bar and north

arrow. On the acetate, identify all the features listed below.

A. Identify as many coronae as you can. Trace their outline and place a “C” within the outline.

B. Identify and mark with an “x” all the craters in the image area.

C. Outline and label with the letters “CRT” all areas of complex ridged terrain.

D. Outline and label with an “R” all rift zones.

E. Outline and label with a “V” areas of volcanic flows. Do not include the extensive smooth plains flows.

Look for the variation in texture as seen in Figure 12.7.

Part C

One day, planetary scientists hope to send a robotic rover to the surface of Venus. Because the surface temperature is about 470°C (~870°F), people will probably never set foot on this planet. In this part of the exercise you will

plan a rover journey. 

In planning the rover path remember these rules: 1) the robotic rover can only travel on smooth terrain (dark

plains); 2) it cannot cross rift zones or complex ridged terrain; 3) it must travel in straight lines (turns are allowed,

but the path will be lines and angled turns rather than curves); and 4) the rover can crossthe black non-imaged parts

of the image, but you cannot drive for any great distance inside the black areas, because there may be unknown

obstacles.

You should develop a rover path to include a visit to at least 1 crater, 2 coronae, the edge of a region of complex ridged terrain, and an area of volcanic flows (not including the smooth plains). Spacecraft and rover engineers designed the rover to travel a maximum distance of 3430 km (a distance of 25 cm on the image) starting

from either landing point A or B. Because of the high temperatures on the surface and the limited fuel carried

by the rover, 3430 km is the maximum lifetime-distance expected of the rover. Optimizing your path to travel

less than 3430 km is highly recommended by the design team. Use the string (or a ruler), the image, and your

acetate map with the features identified to plan a rover path to visit the five features listed above. 

You may choose any individual feature to visit, but you must begin at either point A or B, and you must complete the path to all five features in 3430 km (25 cm) or less. You do not need to return to the starting point. If you

are having difficulty in planning the rover path, ask your instructor to check that you have identified all possible

locations for each type of feature. Once you have settled on the features to visit and the rover path, trace the path

onto your acetate “map.”
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Figure 12.2.a. Landsat photo of part of the Mojave Desert, CA. 

Figure 12.2b. Seasat radar image of the same part of the Mojave Desert, CA as shown in Figure 12.1a.

The feature labeled A is the Pisgah lava flow. The feature labeled B is a dry lake bed. The feature labeled C

is a cinder cone.

Exercise Twelve: Geologic Features of Venus

A

C B

5 km N

A

C

B

5 km N
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Exercise Twelve: Geologic Features of Venus

Figure 12.3. The

prominent circular

features in this

image are impact

craters. Magellan

radar image (FMIDR 30N287).

North is to the top.

Figure 12.4. The right side of

this image shows a major

zone of rifting. Note that the

crater labeled A has been cut

by the rift, with part of the

crater visible on both sides of

the rift. The thin linear features in the southern portion

of this image are faults and

fractures. Magellan radar

image (F-MIDR 30N281).

North is to the top. 

A

100 km

N

A

100 km

N
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Exercise Twelve: Geologic Features of Venus

Figure 12.5. This image shows the terrain termed “complex ridged terrain” or “tessera” on Venus. Considered by many to

be the oldest surface terrain, it has been subject to extensive faulting and fracturing. It generally forms highlands above

the surrounding volcanic plains. Magellan radar image (F-MIDR 30N123). North is to the top. 

100 km

N
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Exercise Twelve: Geologic Features of Venus

Figure 12.6. Volcanoes come in all sizes on Venus. The ones in this image range from 1 to 10 kilometers in diameter.

While volcanoes of this type and size are sometimes found as an isolated structure within the volcanic plains, they are generally found in clusters, termed “shield fields,” like the field shown here. Magellan radar image (F-MIDR 45N119). North

is to the top. 

100 km

N
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Figure 12.7. This image shows an area of young volcanic flows. Magellan radar image (F-MIDR 20S180). North is to the top.

Exercise Twelve: Geologic Features of Venus

100 km

N
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Exercise Twelve: Geologic Features of Venus

Figure 12.8. The circular features in this image are termed “coronae” (singular: “corona”). Interpreted to have formed by the

rise and then subsidence of subsurface plumes of material, these features are easily identified by the characteristic circular and

radial fracture patterns. Some coronae have been the site of volcanic flows, such as at the corona labeled A. Magellan radar

image (F-MIDR 40N018). North is to the top. 

100 km

N

A
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ Figure 12.9. Magellan radar image of part of the Carson Quadrangle, Venus (C2-MIDR 00N337;2). North is to the top.

Exercise Twelve: Geologic Features of Venus 200 km

N

A

B
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Purpose

This exercise allows the student to develop skills

in image interpretation and comparative planetology by analyzing similarities and differences in the

landforms and the geological histories of four outer

planet satellites. Incorporated are skills of geological

mapping, description, and interpretation of tables.

Materials

Clear acetate or overhead projector transparencies (2 sheets per student or group), overhead projector markers (colored markers can be used for

added clarity)

Substitutions: Tracing paper, pencils (colored

pencils for added clarity) 

Background

Reconnaissance of the giant, gaseous outer planets of the solar system and their major satellites was

undertaken by the two Voyager spacecraft,

launched in 1977. Voyagers 1 and 2 flew past Jupiter

and its major satellites in 1979, then explored Saturn

and its moons in 1980 and 1981. Voyager 2 flew past

Uranus and its satellites in 1986 and explored the

Neptune system in 1989. These spacecraft enabled

the discovery of the spectacular diversity in the

geology of the outer planet satellites. 

This exercise uses Voyager images of four of these

moons—Ganymede and Io at Jupiter, and

Enceladus and Rhea at Saturn—to illustrate this

diversity. Most of the outer planet satellites are composed of mixtures of rock and ice. The ice typically is

water ice, but more exotic ices, such as methane, are

present in some satellites, especially those circling

planets farthest from the sun. Io is unusual in being

a rocky world, and in the predominance of active

volcanism which shapes its surface today.

Ganymede and Enceladus show widespread evidence for past volcanism, but the “lava” that once

flowed on these satellites is comprised of ice, rather

than rock. Ganymede and Enceladus show clear evidence for tectonism, expressed as grooves and

ridges. Tectonism has affected Io and Rhea to lesser

degrees, and its expression will probably not be

apparent to students from the images supplied in

this exercise. The most observant students, however,

may notice small grooves on Rhea and Io. The abundant cliffs on Io may be tectonic in origin, or they

may be related to sublimation of a volatile material

and subsequent collapse, a form of gradation.

In general, gradational processes on outer planet

satellites are not apparent at the scale of Voyager

images and are not specifically addressed in this

exercise. However, in discussing the morphologies

of craters on Rhea, it would be useful to point out to

students that the principal cause of crater degradation on that satellite is the redistribution of material

by impact cratering. New craters pelt older ones,

creating ejecta and redistributing material to subdue

the forms of fresh craters over time. To a lesser

extent, mass wasting probably acts to modify crater

shapes through the action of gravity. 

There are many opportunities for class discussion

of specific topics only touched upon by this exercise.

For example, question 5 regarding the morphologies

of craters on Ganymede might initiate discussion on

what could cause their different appearances.

Where relevant, information that will help the

instructor guide discussion is included in square

brackets within the answer key.

Exercise Thirteen:

The Geology of Outer Planet Satellites

Exercise

Thirteen

Geologic Features of

Outer Planet Satellites

Instructor Notes

Suggested Correlation of Topics

Comparative planetology, geological mapping, geomorphology, impact cratering, outer

planets, tectonism, volcanism

2.5 hours

Exercises Two and Fifteen are suggested

as introductory exercises.
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Exercise Thirteen:

The Geology of Outer Planet Satellites

It may be interesting to consider the sources of

heat for driving the volcanism and tectonism on

outer planet satellites. The gravitational pull on a

satellite by the parent planet about which it orbits

and by neighboring satellites can cause tidal heating

of the satellite. Heat is generated as the satellite is

squeezed by gravitational stress as it moves in a

slightly elliptical orbit about its primary planet. This

is the principal source of heat for Io, and may have

driven activity on Ganymede and Enceladus in the

past. Rhea has been relatively inactive; however,

poor resolution Voyager views of Rhea’s opposite

hemisphere provide tantalizing hints that volcanism

and tectonism indeed have affected Rhea to some

extent.

The instructor may choose to show Voyager

images of other icy satellites, such as Iapetus, a moon

of Saturn that shows one bright, icy hemisphere

while its other half is as dark as charcoal; Miranda, a

moon of Uranus that shows spectacular regions of

volcanism and tectonism juxtaposed within ancient

cratered terrain; or Triton, Neptune’s large moon

which has active geysers likely propelled by liquid

nitrogen that shoots up into a tenuous atmosphere.

Also, this exercise has neglected enigmatic Titan, the

largest moon of Saturn, which possesses an atmosphere of nitrogen, methane, and organic compounds

so thick as to hide its surface. Pluto and its satellite

Charon have not yet been visited and photographed

by spacecraft. These two objects are small and icy,

akin to many outer planet satellites; thus, information

about them is included in Table 1.

This exercise is designed for individual completion by each student. Instructors may wish to have

students work together in groups, perhaps with

each student of a group being responsible for a specific satellite. Where relevant questions are encountered, encourage students to separate their description of a satellite surface from their interpretation of

the geological history of the surface; questions here

attempt to distinguish the two. Note that some

questions ask for the student to report a radius

value when given a satellite’s diameter, requiring

some simple math. 

If the mapping exercises are done on clear acetate

as recommended, then they can be overlain on an

overhead projector to compare student maps and

prompt discussion of mapping choices. The final

question (number 20) works well when done

together as a class discussion. It may be useful for

the class to construct a chart that summarizes the

radii, densities, and compositions of each satellite

(compiling information from questions 1, 6, 11, and

16). This will facilitate discussion of how these parameters might affect satellite activity. It will be found,

however, that there are no obvious correlations from

the satellites introduced in this exercise. 

It would be useful to review with students the

processes of impact cratering, volcanism, and tectonism (as introduced in Unit One) before proceeding with this exercise. Discussion of geologic mapping and stratigraphic relations (introduced in Unit

5) would be helpful as well. Exercise 10 is a good

complement to this one, as it investigates the terrestrial planets at the global scale.

Science Standards

■ Earth and Space Science

• Origin and evolution of the Earth system

Mathematics Standards

■ Computation and estimation
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I. Ganymede

1. Ganymede orbits the planet Jupiter. Its radius of

2631 km makes it the largest satellite in the solar

system, bigger even than the planet Mercury. Its

density of 1.94 g/cm3 means that it is composed

of a roughly equal mixture of rock and ice. 

2. a. The bright terrain has a high albedo and

shows few craters. It contains sets of parallel

and intersecting grooves, and also shows

smooth areas. Some of the bright material is

contained within narrow lanes that cut across

the dark terrain.

b. The dark terrain has a low albedo and shows

many craters. Few grooves are seen on the dark

terrain. The dark terrain can form “islands”

within the bright terrain. 

3. a. The dark terrain is older, as it is the more

heavily cratered and is cross-cut by swaths of

bright terrain. 

b. Although the ages of individual crater ejecta

deposits will vary depending on the age of a

crater, ejecta from crater “A” is superimposed on

both bright and dark materials, indicating that

the ejecta is younger than these other materials. 

4. The bright terrain includes smooth patches and

is only lightly cratered, suggesting that it is volcanic in origin and that bright terrain volcanism

probably erased preexisting dark terrain craters.

The bright terrain contains numerous grooves,

which are probably of tectonic origin. [The

grooves probably formed by extensional tectonism (rifting), meaning that the bright material

was pulled apart, and fault valleys formed the

grooves.]

5. a. This 100 km diameter crater shows a central

dome. [Crater domes might form in large craters

either by rebound upon impact or from later

magmatism.] It also shows very small craters

around it, some aligned in chains. [These smaller craters are secondaries—formed as chunks of

ejecta were thrown from the large crater as it

formed.]

b. This 23 km diameter crater shows bright rays

emanating from it. [Bright rays are created by

ejecta thrown from relatively fresh craters, and

they disappear over time as subsequent smaller

impacts pelt this material.]

c. This 50 km crater has been cut by a dark terrain

groove.

d. This 10 by 60 km feature is probably an impact

crater that formed by an oblique (low angle)

impactor which skimmed the surface of

Ganymede as it hit. [Students may notice that

some craters in the bright material have dark

floors. Dark craters can form in bright material

either because the impactor was a dark asteroid

rather than a bright comet, or because the craters

punch through bright material to throw out

underlying dark material in their ejecta.]

II. Enceladus

6. Enceladus orbits the planet Saturn and has a

radius of only 251 km. Its density of 1.24

g/cm3 means that it is composed of mostly ice. Its albedo of 95% is higher than the albedo of

any other satellite.

7. The largest craters on Enceladus show central

mounds. [The mounds might be due to central

volcanism or slow rebound of the crater shape

because of a warm satellite interior.] Some

medium-sized craters in the bottom third of the

image appear to have been cut in half. [They

were probably disrupted by tectonism and/or

partially flooded by volcanism.]

Answer Key

Geologic Sketch Map of Enceladus

Exercise Thirteen:

The Geology of Outer Planet Satellites
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8. Grooves and ridges are predominantly concentrated in a band that runs across the satellite. 

9. (Answers will vary) 

a. Cratered terrain: Characterized by numerous

craters, with few obvious grooves.

b. Ridge-and-groove terrain: Characterized by

approximately parallel-trending ridges and

grooves that curve gently and has few craters.

c. Smooth plains: Smooth-appearing plains with

little evidence for topography other than a few

tectonic features. 

10. a. The cratered terrain is oldest, as it is the

most heavily cratered and it appears to be

cross-cut by the ridge-and-groove terrain.

b. It is difficult to be certain of the relative

ages of the smooth plains and the ridge-andgroove terrain. The smooth plains may be the

youngest, having flooded the region neighboring the ridge-and-groove terrain. On the other

hand, preexisting smooth plains may have

been tectonically deformed to create the ridgeand-groove terrain. (Answers will vary.) 

III. Rhea

11. Rhea orbits the planet Saturn and has a radius

of 764 km. Its density of 1.33 g/cm3 means that

it is composed of ice with minor amounts of rock.

12. Impact cratering.

13. a. (See question 14.a. below.)

b. (See question 14.a. below.)

c. Craters probably have sharp-appearing morphologies when they first formed, i.e., when

they were “fresh.” Over time, craters become

more and more subdued or “degraded.”

14. a. [Because subdued craters may be difficult to

find, several are indicated on this sketch map.]

b. Central peaks are more apparent in fresh

craters.

c. The fact that peaks are most apparent in

fresh craters suggests that central peak topography, like the rest of the crater, becomes

more subdued and less prominent over time

as subsequent impacts redistribute material.

d. The transition diameter is between ~10 and

20 km.

15. a. Rhea shows abundant evidence for cratering, and is more heavily cratered than the

surfaces of the other two satellite. Unlike

Ganymede and Enceladus, this part of Rhea

shows no smooth terrains and essentially no

grooves. Like Enceladus, Rhea's surface is of

uniform albedo; this is in contrast to the surface of Ganymede, which shows bright and

dark terrains.

b. Rhea has had a less active geological history. It is dominated by the external process of

cratering. Unlike Ganymede and Enceladus, it

does not show widespread evidence for the

internally-driven processes of volcanism and

tectonism. 

IV. Io

16. Io is a satellite of the planet Jupiter. Its density of

3.57 g/cm3 means that it is composed of rock.

This density is unusual in that it is higher than

that of any other outer planet satellite. Io is 1815

km in radius.

Answer Key (continued)

Exercise Thirteen:

The Geology of Outer Planet Satellites

Rhea Crater map
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17. a. Volcanism.

b. It shows a somewhat irregular, scalloped

shape of three coalescing circles. 

c. A caldera. 

18. Volcanism is the principal process shaping the

surface of Io, as demonstrated by the abundance of flow-like features, smooth materials,

and irregularly-shaped calderas that are commonly associated with high and/or low albedo materials. No impact craters can be confidently identified on Io, and they have presumably been erased by volcanism. 

19. Craters on Rhea are a) generally more circular; b)

more numerous; c) commonly have smaller

craters superimposed on them; d) show a range

of morphologies from sharp to subdued (a range

of degradation states); e) show central peaks.

Some craters on Io are associated with bright

and/or very dark materials. 

20. (Answers may vary—acceptable alternative

answers are provided in parentheses.)

Ganymede

Impact Cratering 2 (3) 3 (2) 1 4

Volcanism 3 (2) 2 (3) 4 1

Tectonism 1 (2) 2 (1) 4 (3) 3 (4)

Enceladus Rhea Io

Exercise Thirteen:

The Geology of Outer Planet Satellites

Answer Key (continued)
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Exercise Thirteen:

The Geology of Outer Planet Satellites

Name

Exercise

Thirteen

Geologic Features of

Outer Planet Satellites

Purpose

To recognize the similarities and differences in

the processes affecting the outer planet satellites,

and in the resulting landforms.

Materials

Acetate (2 sheets), overhead transparency markers

Introduction

Planetary geologists study the solid surfaces of

solar system objects. This includes the planets of the

inner solar system and the moons, or satellites, of all

the planets. The giant gaseous planets of the outer

solar system—Jupiter, Saturn, Uranus, and

Neptune—have a total of 62 satellites. 

The outer planets are far from the warmth of the

Sun, so the satellites that circle them are very cold—so

cold that many are composed partly or mostly of ice.

Much of the ice in these satellites is water ice, the kind

in your freezer. But some satellites probably contain

other types of ice, including ammonia, methane, carbon monoxide, and nitrogen ices. These are compounds that you may know as liquids or gases in the

warm environment of Earth.

Some outer planet satellites display many impact

craters, and some are less cratered. In general, an older

surface shows more and larger impact craters than a

younger surface. Also, younger features and surfaces

will cut across or lie on top of older features and surfaces. Relatively fresh or large craters commonly show

a blanket of bright ejecta, material thrown from the

crater as it was formed. 

The surfaces of outer planet satellites can also be

shaped by volcanism and tectonism. Volcanism can

erase craters while creating regions that appear

smooth. On a rocky satellite, the volcanic lava will

be rocky; on an icy satellite, an icy or slushy “lava”

might emerge from the satellite's relatively warm

interior. A centers of volcanism is sometimes

marked by an irregularly shaped volcanic crater

termed a caldera. Tectonism can create straight or

gently curving grooves and ridges by faulting of the

surface. Commonly, an area smoothed by volcanism

will be concurrently or subsequently affected by tectonism. A volcanic or tectonic feature must be

younger than the surface on which it lies. 

The density of a planet or satellite provides information about its composition. Density is a measure

of the amount of mass in a given volume. Rock has

a density of about 3.5 g/cm3, and most ices have a

density of about 1 g/cm3. This means that a satellite

with a density of 3.5 g/cm3 probably is composed

mostly of rock, while a satellite of density 1 g/cm3 is

composed mostly of ice. A satellite with a density of

2 g/cm3 probably is composed of a mixture of nearly equal amounts of rock and ice. 

The albedo of a satellite is a measure of the percentage of sunlight that the surface reflects. A bright

satellite has a high albedo, and a dark satellite has a

low albedo. Pure ice or frost has a very high albedo.

If a satellite's surface is icy but has a low albedo,

there is probably some dark material (such as rock)

mixed in with the ice. 

Even if the albedo of a satellite is completely uniform, the apparent brightness of the surface can

change based on the positions of the Sun and the

observer. The lit edge, or limb, of a planet or satellite

typically appears bright. The surface looks darker as

the day/night line, or terminator, is approached

because that is where shadows are longest.
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Questions and Procedures

I. Ganymede

1. The Table will help you to fill in the blanks: 

Ganymede orbits the planet ________ . Its radius of _______ km makes it the largest satellite in the

solar system, even bigger than the planet Mercury. Its density of ______ g/cm3 means that it is composed of _________ . 

Examine Figure 13.1a, which shows part of the Sippar Sulcus region of Ganymede, and compare what you see

to the geomorphic sketch map of the area (Figure 13.1b). Notice that the surface of Ganymede can be divided into

two principal geologic units, bright terrain and dark terrain. The dark terrain is believed to be a mixture of ice and

rock, while the bright terrain is probably composed mostly of ice. 

2. List and describe the many characteristics of the bright and dark terrains. Be as detailed as possible.

Include factors such as albedo, number of craters, general surface appearance, and other characteristics

that are apparent. 

a. bright terrain:

b. dark terrain:

Exercise Thirteen:

The Geology of Outer Planet Satellites

Properties of the Major Satellites* of the Solar System and Pluto

Planet Satellite Diameter (km) Mass (x1023g) Density (g/cm3) Albedo (%)

Earth Moon 3476 735 3.34 12

Jupiter Io 3630 894 3.57 63

Europa 3138 480 2.97 64

Ganymede 5262 1482 1.94 43

Callisto 4800 1077 1.86 17

Saturn Mimas 394 0.38 1.17 60

Enceladus 502 0.8 1.24 95

Tethys 1048 7.6 1.26 70

Dione 1118 10.5 1.44 50

Rhea 1528 24.9 1.33 60

Titan 5150 1346 1.881 20

Iapetus 1436 18.8 1.21 4 (leading),

50 (trailing)

Uranus Miranda 492 0.69 1.15 32

Ariel 1158 12.6 1.56 31

Umbriel 1170 13.3 1.52 20

Titania 1578 34.8 1.70 28

Oberon 1522 30.3 1.64 23

Neptune Triton 2706 214 2.07 73

Proteus 416 ~0.4? ~1.5? 6

Pluto ~2360 ~130 ~2 ~50

Charon ~1180 ~110 ~1.3 ~40

* Only satellites larger than about 400km diameter are listed here, in order of increasing distance
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Exercise Thirteen:

The Geology of Outer Planet Satellites

3. a. Which of Ganymede’s two principal terrain types is older? How can you tell?

b. What is the age of the ejecta for the crater marked “A” relative to the bright and dark terrain? How

can you tell?

4. Many researchers believe that the bright terrain of Ganymede was shaped by both volcanism and tectonism. What is some evidence that this is true?

5. All the craters you can see in Figure 13.1a probably formed by the impacts of comets or asteroids. Many

show small central pits, created as a result of impact into an icy target.

Four craters that show unusual morphologies are indicated in Figure 13.1b with the letters A through D.

Describe the shapes and characteristics of these interesting craters. Include the dimensions of each crater using the

scale bar, and also describe the characteristics that make it peculiar compared to most other craters on Ganymede. 

A:

B:

C: 

D:

II. Enceladus

6. Enceladus orbits the planet __________ and has a radius of only _______ km. Its density of ______ g/cm3

means that it is composed of __________ _____________________. Its albedo of __________ is

__________ than the albedo of any other satellite.

Now make a geological sketch map of Enceladus. Use as a guide the map of Ganymede in Figure 13.1. Tape

a piece of acetate over the photograph of Enceladus, Figure 13.2. Trace the outline of the satellite. You will find

that it is simple to trace the satellite's limb, but the terminator is not as clearly defined. Next, outline the most

prominent craters on the satellite, you will have to decide which craters should be included.

7. Locate and describe two unusual looking craters.

Grooves on Enceladus are probably tectonic features; next map their locations. This symbol ( ) is one

way of mapping a groove. Draw a thin line along each groove you see, and place a dot near the center

of each line to indicate it is a groove. 

8. Where do grooves (and the ridges between them) occur on Enceladus? 
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Exercise Thirteen:

The Geology of Outer Planet Satellites

The surface of Enceladus can be divided into three different types of terrain. Think about the features you

have mapped so far, and decide on how to divide the surface into three terrains. Decide on names that describe

your units. (For example, “cratered terrain.”)

Draw boundaries around the different units. There might be only one patch of each unit, or there could be

more than one patch. To complete the map of Enceladus, label the units with the descriptive names that you

have given them. 

9. List the names of your three units. Following each name, describe the characteristics of each unit as you

defined it in making your map of Enceladus.

A:

B:

C: 

10. a. Which is the oldest of these three major units on Enceladus? How can you tell?

b. Which is the youngest of these three major units on Enceladus? How can you tell?

III. Rhea

11. Rhea orbits the planet __________ and has a radius of _______ km. Its density of ______ g/cm3 means

that it is composed of _____________________.

12. Examine Figure 13.3, which shows a part of Rhea's surface. What is the principal geologic process that

has shaped this part of Rhea? 

13. Notice the morphologies (shapes) of the craters that you see in Figure 13.3. The 60 km crater A shows a

sharp and distinct morphology, with steep and well-defined slopes. On the other hand, the 65 km crater

B is more difficult to identify, as it is rounded and indistinct. Keep in mind that the cratered surface of

Rhea seen is probably about 4 billion years old.

a. Lay a piece of acetate over Figure 13.3, taping it at the top. Trace the rectangular outline of the photo,

and also trace and label the scale bar. With a solid line, trace the outline of crater A, and label the

crater “sharp.” Next locate and trace the outline of crater B, but this time use a dashed line. Label this

crater “subdued.”

b. Locate one additional sharp crater, outlining it with a solid line. Find an additional subdued crater,

and outline it with a dashed line.
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Exercise Thirteen:

The Geology of Outer Planet Satellites

c. The terms “sharp” and “subdued” are descriptive terms, used to describe the morphologies of

craters. Sharp-appearing craters are sometimes referred to as “fresh,” while subdued-appearing

craters are commonly referred to as “degraded.” What do the terms “fresh” and “degraded” imply

about how a crater’s morphology changes with time on Rhea? 

14. Notice that some of Rhea’s craters, including crater A, show central peaks. These form upon impact, due

to rebound of the floor during the “modification stage” of the cratering process.

a. On the acetate, outline as many central peak craters as you can confidently identify. Retain the

scheme of outlining each sharp crater with a solid line, and each subdued crater with a dashed line.

Put a dark dot in the middle of each central peak crater that you identify. 

b. Are central peaks more recognizable in sharp or subdued craters?

c. Based on your answer to part b, what can you infer about how the topography of a central peak

changes over time? 

d. Central peaks form only in craters above a certain diameter. This “transition diameter” from simple,

bowl-shaped craters to more complex, central peak craters depends on surface gravity and material

properties, so it is different for each planet and satellite. Estimate the transition diameter for craters

on Rhea based on the smallest central peak craters that you are able to identify.

15. Consider the surface of Rhea (Figure 13.3) in comparison to the surfaces of Ganymede (Figure 13.1) and

Enceladus (see Figure 13.3 and your sketch map).

a. Compare and contrast the general appearance of the surface of Rhea to the surfaces of Ganymede

and Enceladus. 

b. What do the differences in surface appearance suggest about the geological history of Rhea as compared to the histories of Ganymede and Enceladus? 

IV. Io

16. Io is a satellite of the planet __________. Its density of ______ g/cm3 means that it is composed of

_____________________. This density is unusual in that it is ___________ than that of any other outer

planet satellite. Io is _____________ km in radius. 

Examine Figure 13.4, which shows part of the surface of Io. The very high albedo material is considered to

be sulfur dioxide frost. When the two Voyager spacecraft flew by Io in 1979, they photographed nine actively

erupting volcanoes. 

17. Examine the feature in the far northeast corner of the image, which shows a central depression with relatively low albedo (dark) material radiating from it.

a. What process created this feature?
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Exercise Thirteen:

The Geology of Outer Planet Satellites

b. Describe in detail the shape of the central depression. Use a sketch if you like. (Use the sketch area

below.)

Sketch area

c. What kind of volcanic “crater” is this central depression?

18. Examine the other craters and surface features seen in Figure 13.4. What is the principal process shaping

the surface of Io? List some observations that support your answer.

19. Contrast the characteristics of craters that you see on Io to those on Rhea. List at least four differences

between Io’s volcanic craters and Rhea’s impact craters.

20. On the chart below, rank the relative importance of impact cratering, volcanism, and tectonism on the

four outer planet satellites that you have studied, based on the images you have seen. Use numbers

from 1 (for the satellite most affected) to 4 (for the satellite least affected). 

Ganymede

Impact

Cratering

Volcanism

Tectonism

Enceladus Rhea Io
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Exercise Thirteen:

The Geology of Outer Planet Satellites

Figure 13.1.a. Voyager 2 image of Ganymede (FDS 20636.02) at a resolution of 1.5 km/pixel, showing part of Sippar

Sulcus in lower half.

100 km

N
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Figure 13.1.b. Geological sketch map corresponding to Figure 13.1a. 

Exercise Thirteen:

The Geology of Outer Planet Satellites
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Exercise Thirteen:

The Geology of Outer Planet Satellites

Figure 13.2. Photomosaic of Enceladus constructed from Voyager 2 images with resolutions of about 2 km/pixel. The

satellite has a diameter of approximately 500 km. (Jet Propulsion Laboratory photomosaic P-23956 BW). 
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Exercise Thirteen:

The Geology of Outer Planet Satellites

Figure 13.3. The surface of Rhea, seen by Voyager 1 at 700 m/pixel (FDS 34952.59).

50 km

N

A

B
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Figure 13.4.

The surface of

Io seen in a

mosaic of

Voyager images

FDS 16392.43,

.39, and .41.

Resolution is

2.1 km/pixel.

(United States

Geological

Survey mosaic

V0357/1).

Exercise Thirteen:

The Geology of Outer Planet Satellites

200 km

N
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Purpose

The objective of this exercise is to apply the

techniques of stereoscopic photograph analysis to

the interpretation of the geology and history of

planetary bodies.

Materials

For each student group: Stereoscope 

Background

Unit One introduced students to the four geologic processes: volcanism, tectonism, gradation,

and impact cratering. In Exercise Three, stereoscopic photographs were used to acquaint students

with the three dimensional shapes of some terrestrial landforms created by these processes. Here,

these themes are extended to other planets and

planetary bodies. 

This exercise builds upon previous ones. It would

be useful to review the four geologic processes of

Unit One before proceeding. The procedure for

using stereoscopic photographs is briefly reviewed

in the student section of this exercise, but for more

detail, refer to Exercise Three: Geologic Processes

Seen on Stereoscopic Photos. 

This exercise promotes comparisons among the

planetary bodies examined, including the Moon,

Mars, Venus, and several outer planet satellites. It is

useful for the student to have completed previous

exercises (10 through 13) which introduce the geology of these bodies, although this exercise can be

worked independently. 

This exercise has many parts. If time does not

permit completion of the entire exercise by all students, then groups of students might be assigned

the different parts. Class discussion could then be

used to share and synthesize what has been learned.

Science Standards

■ Earth and Space Science

• Origin and evolution of the Earth system

Exercise Fourteen: Planets in Stereo

Exercise

Fourteen Planets in Stereo

Instructor Notes

Suggested Correlation of Topics

Comparative planetology, impact craters,

stereoscopic photography

2.0 hours

Exercises Two, Three, Ten, Eleven,

Twelve, and Thirteen are suggested

as introductory exercises.
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1. a. The contact is sharp and abrupt. The plains

appear to lap up against the hills. 

b. The indication is that the plains are

younger, having filled low-lying regions.

2. The plains consist of volcanic lava flows.

Hadley Rille transported some of these lavas. 

3. a. Hadley is a bowl shaped crater. Its rim is

upraised above the surroundings. 

b. These characteristics suggest an impact origin.

4. Hadley Rille is older, as the crater’s ejecta

appears to cover part of the rille. 

5. The rim is raised and slopes continuously

upward from the surrounding plains. Ejecta

deposits are superposed on the plains.

Moreover, the crater is superimposed on, and

thus younger than, Hadley Rille (which probably formed at the same time as the plains).

6. a. The crater shows a raised rim, a central

peak, terraced walls, and a relatively flat

floor. 

b. These characteristics suggest an impact origin. 

7. The crater forms the rounded edge of the

“island.” It might have served as a barrier to

liquid that flowed around the crater, eroding

away material to either side, and leaving an

island downstream of the crater. This island

might be in a dry river bed. The process is

gradation.

8. The material appears to be layered.

9. a. Tectonism. 

b. Crater material has slid down a steep slope

into the trough below, leaving a rough (radar

bright) landslide deposit. This is an example

of gradation. 

10. a.

b. Volcanism.

c. They are irregular depressions (pits),

formed volcanically.

11. a. There are many large, irregular depressions. Some smaller depressions are linear or

aligned in chains. Some depressions are long

and sinuous. 

b. The similarity in shape suggests that the

sinuous depressions on Venus may have

formed as lava channels and collapsed tubes

similar to Hadley Rille on the Moon. 

c. Volcanism.

12. Ida is irregularly shaped rather than spherical.

Its outline consists of concavities (some of

which are large craters) and ridge-shaped features between them.

13. Cratering; the concavities, ridges, and irregular

shape probably resulted from the shattering of

a larger parent asteroid and repeated impact

bombardment.

14. Cratering. 

15. Craters on Rhea have irregular outlines, and

they overlap one another. Dione’s craters are

more circular, and there are fewer craters on

Dione, so there is less overlapping. Both satellites show some central peak craters. 

16. a. Rhea’s surface is older, as it is much more

heavily cratered. 

b. Dione may have been volcanically resurfaced in the past. This would have obliterated

its older craters. The craters we see have all

formed since this event. 

17. a. A large rift cuts across Titania. It shows

curved fault segments and a jagged overall

trace. 

b. Tectonism. 

18. a. The material is smooth appearing and is

convex-upward in shape. 

b.

c. Tectonism and volcanism.

19. a. The coronae show ridges and troughs. This

is different from the cratered terrain, which

shows few scarps. The cratered terrain is

more heavily cratered. 

b. Tectonism, and probably volcanism.

Tectonism produced the ridges, grooves, and

scarps. Volcanism may be responsible for

light and dark patches within the coronae.

Answer Key

Exercise Fourteen: Planets in Stereo
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Exercise Fourteen: Planets in Stereo

Name

Exercise

Fourteen Planets in Stereo

Purpose

To apply techniques of stereoscopic photograph

analysis to the interpretation of the geology and history of planetary bodies.

Materials

For each student group: stereoscope

Introduction

Geologists are concerned with rock formations and

landforms as three dimensional units. An understanding of the geometry of a geologic formation is important to the interpretation of its origin and history.

Topographic information can be obtained in a variety

of ways. The most simple and reliable is by means of

stereoscopic photographs. 

We see in three dimensions and are able to judge the

distances to objects because our eyes are spaced about

65 mm apart. We see the same scene from two different angles, and the brain is able to interpret this information to give us a perception of depth. The same

principle is used to view a pair of stereoscopic photographs taken from spacecraft. 

A stereoscopic pair is made by taking two images of

the same scene from slightly different angles. This can

be done by a spacecraft as it moves above the surface

of a planetary body. For example, the metric mapping

cameras of the Apollo orbiter took sequential pictures

that overlap by 78%. That is similar to the overlap that

our two eyes provide for the same scene. 

To observe the three-dimensional stereoscopic

effect, each photograph of the stereo pair must be

viewed by a separate eye. This can be accomplished by

viewing through a stereoscope. Center the stereoscope

on the seam between the photographs of a stereo pair,

relax your eyes, and let the photos merge together into

one image in order to observe the stereo effect. Try

placing your index fingers on the same object within

each photo of the stereo pair, and then focus until your

fingers appear to overlap. When you remove your fingers, the stereo effect should become apparent. Some

people cannot see stereo at all; for most others, it simply takes patience and practice. 

In analyzing the stereo photographs of this exercise,

recall the four geologic processes: volcanism, tectonism, gradation, and impact cratering. You will be

asked to recognize the processes that have shaped

planetary surfaces based on the three-dimensional

appearances of the visible landforms. 

Questions

Part A. Moon. 

Examine Figure 14.1, which shows the area of Hadley Rille, landing site of Apollo 15. Hadley Rille, the sinuous

trough winding across the region, is an ancient lava channel that carried active flows into the dark plains (maria).

Hadley crater is the prominent crater beside the rille. 

1. Study the contact (boundary where two different types of materials meet) between the bright, rough hills and

the smooth, dark plains. 

a. Describe this contact. What is the character of the boundary? 
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Exercise Fourteen: Planets in Stereo

b. What conclusions can you draw about the age relationship between the hills and plains? 

2. How might the plains have formed?

3. Examine the appearance of Hadley crater.

a. Describe the crater’s shape and characteristics, including its rim and interior. 

b. These characteristics suggest what kind of origin for Hadley crater?

4. Which is older, Hadley Rille or Hadley crater? How can you tell? 

5. What evidence is there that Hadley crater is younger than the plains lavas, instead of the plains lavas having

flowed around an old pre-existing crater?

Part B. Mars. 

Examine Figure 14.2, which shows part of Ares Vallis on Mars. 

6. Notice the prominent 7 km crater. 

a. Describe the shape and characteristics of the crater, including its rim and interior. 

b. Based on these characteristics, what geologic process formed this crater?

7. What is the relationship between the crater and the teardrop shaped “island”? How might the teardrop feature have formed? What is the geologic process?

8. Look carefully at the sides of the teardrop “island,” and also at the steep cliff near the top of the photo.

What can you say about the material near the surface of Mars, as revealed by the cross sections exposed

in the cliffs?

Part C. Venus. 

The surface of Venus is hidden from direct view by its thick clouds. To penetrate the clouds, radar has been used

to map the surface of Venus. In general, rough areas appear bright in these radar images, and smooth areas appear

dark. (For an introduction to the interpretation of radar images and the geology of Venus, see Exercise Twelve:

Geologic Features of Venus.) 
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Exercise Fourteen: Planets in Stereo

9. Examine the stereo images of Figure 14.3, showing the region surrounding crater Geopert-Meyer. 

a. Which of the four geologic processes has most affected this region of Venus?

b. Notice the rough (radar bright) material aside crater Geopert-Meyer, and its relationship to the

prominent trough. What has happened here?

10. Figure 14.4 shows the Eistla region of Venus. 

a. Sketch a cross-section of the shape of the broad domes as they might appear from the surface of

Venus. Use the sketch area below.

Sketch area

b. Which geologic process could have created these domes? 

c. Notice the small depressions on the crests of the broad domes. What is their shape, and what process

likely created them?

11. Examine the topographic depressions in Aphrodite Terra seen in Figure 14.5. 

a. Describe the shapes of the topographic depressions that you see. 

b. Compare this image of Aphrodite Terra to the Hadley Rille area of the Moon (Figure 14.1). What does

the comparison suggest as to the possible origin of the sinuous depressions on Venus? 

c. Which of the geologic process was most important in shaping this region?
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Exercise Fourteen: Planets in Stereo

Part D. Asteroid Ida. 

A stereoscopic view of asteroid 243 Ida is shown in Figure 14.6. 

12. Compare the overall shape of Ida to that of other planetary bodies you have studied. What is unusual about

the asteroid’s shape?

13. What geological process has affected the surface of Ida? How might this process account for the asteroid’s

overall shape?

Part E. Outer Planet Satellites. 

The following figures show stereoscopic images of some of the satellites of Saturn and Uranus. Only five

satellites are shown, a sampling of the dozens of moons of the outer planets. All of the moons shown have icerich surfaces, and none have atmospheres. Figures 14.7 and 14.8 show Rhea and Dione, respectively. These are

two of Saturn’s icy satellites. 

14. What geologic process has most shaped the surface of Rhea?

15. Compare the appearance of craters on Dione to those on Rhea. Include both similarities and differences

in their morphologies. 

16. a. Which satellite appears to have an older surface, Rhea or Dione? How can you tell? 

b. What does this say about whether these satellites might have been resurfaced by volcanism at some

time in the past?

Figures 14.9, 14.10, and 14.11 show Titania, Ariel, and Miranda, respectively. These are icy satellites of

planet Uranus.

17. Notice the prominent feature that stretches across the surface of Titania (Figure 14.9). 

a. Describe this feature.

b. What process is responsible for its formation?

18. Several valleys cross the surface of Ariel , especially near the terminator (the day/night line), visible on

the right side of the stereo image (Figure 14.10).

a. What is unusual about the appearance of the material in these valleys?
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Exercise Fourteen: Planets in Stereo

b. Sketch what a profile across a typical one of these valleys might look like in the sketch area below.

Sketch area

c. What two processes probably acted together to form these features?

19. The surface of Miranda (Figure 14.11) consists of cratered terrain and several regions termed “coronae”

(singular: corona). In contrast to the cratered terrain, the coronae consist of light and dark materials. 

a. Describe the topography and character of the coronae as compared to the cratered terrain which surrounds them. 

b. What process(es) have likely shaped the coronae of Miranda? 
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Figure 14.1. Stereoscopic photographs of the Hadley Rille area of the Moon, landing site of Apollo 15.

The sinuous trough (Hadley Rille) is about 300 m deep. The prominent crater, Hadley, is 5.7 km in diameter. North is toward the top. (Left half is part of AS15-0586, right half, AS15-0585. Spacecraft motion

was from left to right parallel to the bottom edges of the photos).

Exercise Fourteen: Planets in Stereo
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Figure 14.2. Stereoscopic

photographs of the Ares Vallis

region of Mars, constructed

from Viking orbiter images.

North is toward the upper

right. The prominent crater is

about 7 km across. The

Viking 1 Lander site is about

800 km to the west. (Viking

Orbiter 004A52, left, and

004A93, right).

Figure 14.3. Crater

Geopert-Meyer and

surrounding features

on Venus. The prominent trough is about 1

km deep, and the scene

is about 154 km

across. North is

toward the top (NASA

P-42612).

Exercise Fourteen: Planets in Stereo

5 km

N

20 km

N
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Figure 14.4. Domes in

the Eistla region of

Venus. The largest is

about 65 km across but

less than 1 km in

height. North is

toward the top (NASA

P-42684).

Figure 14.5. Part of the

Aphrodite Terra highlands, Venus. Depths

here are as great as 1

km. The image is 73 km

wide, and north is

toward the top (NASA

P-42611).

Exercise Fourteen: Planets in Stereo

20 km

N

10 km

N
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Figure 14.6. Stereoscopic

view of asteroid 243 Ida. The

asteroid is about 60 km long

and 18 km wide. Resolution

is 60 m/pixel. (Stereo image

courtesy Peter Thomas,

Cornell University; from

Galileo spacecraft images

s0202561945 [left] and

s0202562000 [right]).

Figure 14.7. Saturn's icy satellite Rhea is seen in this stereo pair. (Image courtesy Paul Schenk, Lunar

and Planetary Laboratory, Houston; reprojected mosaics of Voyager frames FDS 34950.29, .35, .41, .47,

and .53 [left] and 34952.53, .55, .57, .59, 34953.01, .03, and .07 [right]).

Exercise Fourteen: Planets in Stereo
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Figure 14.8. Dione, an icy satellite of Saturn. (Image courtesy Paul Schenk, Lunar

and Planetary Laboratory, Houston; reprojected Voyager frames FDS 34944.58 [left]

and 34948.28 [right]).

Figure 14.9. The icy satellite Titania, a moon of Uranus. (Stereo image courtesy Paul

Schenk, Lunar and Planetary Laboratory, Houston; reprojected Voyager frames FDS

26836.55 [left] and 26843.13 [right]). 

Exercise Fourteen: Planets in Stereo
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Figure 14.10. The icy uranian satellite Ariel is seen in this stereo pair. (Image courtesy Paul

Schenk, Lunar and Planetary Laboratory, Houston; reprojected Voyager frame FDS 26843.40

[left] and reprojected mosaic of frames 26845.33, .35, .37, and .39 [right]).

Figure 14.11. Miranda, the innermost of the five major icy moons of Uranus, seen in

stereo. (Image courtesy Paul Schenk, Lunar and Planetary Laboratory, Houston; a

reprojected mosaic of Voyager frames FDS 26846.11 and .14 [left] and reprojected

frame 26846.26 [right]).

Exercise Fourteen: Planets in Stereo

25 km
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Maps have been used since the dawn of

communication, when early hunters

scratched simple maps in dirt with sticks.

Through the years maps have evolved to show a

wide variety of cultural and political subdivisions,

historical events, and natural features. Maps figure

prominently in exploration, including solar system

exploration.

Geologic maps show the distribution of rocks and

structures (such as faults) exposed on planetary surfaces. Geologic maps on Earth are usually derived

from field work in which the geologist can examine

rock exposures, called outcrops, up close. Geologists

also use aerial photographs and other remote sensing

data to construct geologic maps of Earth.

Except for the six Apollo landing sites on the

Moon, direct field observations are not available for

making planetary geologic maps. Consequently,

most geologic maps of planets and satellites are

derived from photographs and other remote sensing data, using the same geologic principles used

on Earth. Planetary geologic maps are similar to

preliminary maps constructed for Earth prior to

field work. 

This unit includes three exercises. The first introduces students to the principles of planetary geologic mapping using photographs, the next two

enable the student to put those principles into practice by mapping parts of the Moon and Mars.

Unit

Five

Introduction to

Planetary Geologic

Mapping
Purpose

The objective of this exercise is to demonstrate

how observations of a planet can be used to produce

geologic maps. This includes the identification of

rock units and placement of units in a time

sequence.

Materials

Suggested: clear acetate or overhead transparency, overhead projector markers, tape 

Substitutions: tracing paper and pencil 

Background

Planetary photogeologic mapping differs from

geologic mapping on Earth because field work

generally is not possible. Photogeologic mapping

depends on photo interpretation, supplemented

with other remote sensing data. Despite the lack of

“ground truth,” photogeologic maps are important

for deriving the geologic histories of planetary surfaces. It is assumed that students are familiar with

geologic processes and landforms, as investigated

in earlier exercises.

All additional information for completing this

exercise is contained in the student’s introduction.

Student maps can be overlaid for comparison.

Variation will occur based on the characteristics

chosen to delineate each unit. Have the students

discuss with each other the reasoning behind their

unit selection.

Science Standards

■ Physical Science

• Motions and forces

■ Earth and Space Science

• Origin and evolution of the Earth system

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Exercise Fifteen:

Introduction to Photogeologic Mapping

Exercise

Fifteen

Introduction to

Photogeologic Mapping

Instructor Notes

Suggested Correlation of Topics

Geologic time, geometric relations, geomorphology, maps, remote sensing,

satellite observations, stratigraphy

1.0 hours

Exercise Two is suggested as an

introductory exercise.
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Exercise Fifteen:

Introduction to Photogeologic Mapping

1. Answers will vary. At a minimum students

should list the following: Terrain One: dark

plains—smooth (low relief), dark (low albedo),

sparsely cratered, topographically low areas;

Terrain Two: bright highlands—rough (high

relief), light (high albedo), heavily cratered,

topographically high areas. Possible additional terrains include: large young craters with

rayed ejecta and moderate albedo highlands.

2. Answers will vary given terrains selected. For

the terrains listed in question 1, the highlands

are the oldest, the smooth plains are younger,

and rayed craters are the youngest. Students

should see that the rayed craters are superposed

(on top) of the other terrains, and that the

smooth plains cover (embay) the highlands.

Unit Descriptions

3. The graben is younger than the unit that contains it (the highlands).

4. The smooth plains are younger than the highlands. The highlands contain more craters,

larger craters, and more eroded craters. In

addition, the graben ends at the contact. It is

overlain by the volcanic smooth plains.

5. The ridge is younger.

6. The crater is younger.

Stratigraphic Column

Geologic History: This region was initially covered by a unit, possibly of volcanic origin,

which was heavily cratered and modified by

continued cratering. After formation of the

highlands, tectonism occurred, as evidenced by

the graben. Volcanic flows were emplaced in

map area, represented by the smooth plains

unit. No source area for the flows is identifiable

within the mapped area. Cratering continued

after the emplacement of the smooth plains

unit. There has been a continuation (or reactivation) of tectonic activity in this area, indicated

by the ridge. Finally, cratering has continued—

represented by the crater on the ridge.

Answer Key

Unit Name

Smooth Plains Volcanic flow

Smooth plains, few

craters (mostly

small), low albedo

Highlands

Old, heavily modified surface, possibly

of volcanic origin

Rugged, numerous

craters are various

sizes, high albedo,

topographically high

Observation Interpretation

Smooth Plains

Graben

Youngest

Oldest

Crater on Ridge

Ridge

Highlands

Geologic Unit Structural Features
Exercise Fifteen:

Introduction to Photogeologic Mapping 185

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Name

Exercise

Fifteen

Introduction to

Photogeologic Mapping

Purpose

The objective of this exercise is to demonstrate

how careful observations of a planet can be used to

construct geologic maps. This includes the identification of rock units and placement of units in a time

sequence.

Materials

Clear acetate or overhead transparency, overhead

projector markers, tape (or tracing paper and pencil)

Introduction

More than three decades of planetary exploration

show that the surfaces of the solid planets and satellites have been subjected to the same geologic

processes: volcanism, tectonism (e.g., earthquakes),

gradation (erosion, etc.), and impact cratering. The

relative importance of each process differs from

planet to planet, depending upon the local environment. For example, a planet not having running

water, such as the Moon, will experience erosion of

a different style and intensity in contrast to a planet

having abundant running water such as Earth.

Prior to the space program, the importance of

impact cratering as a geologic process was not fully

appreciated. It is now known that all of the planets

were subjected to intense impact cratering in the

early history of the solar system. Indeed, most of the

craters on the Moon are of impact origin. On some

planets, such as the Moon and Mercury, evidence of

the impact process is preserved; on other planets,

such as Earth, impact cratering is less evident. On

the Moon, craters range in size from tiny micro

craters of sub-millimeter size to the giant impact

basins such as the 1300 km-diameter Imbrium basin.

A geologic map is a graphic portrayal of the distribution and sequence of rock types, structural features such as folds and faults, and other geologic

information. Such a map allows geologists to represent observations in a form that can be understood

by others and links the observations made at different localities into a unified form. In many respects, a

geologic map is like a graph to a physicist; it allows

one to understand many observations in a comprehensive form.

The unit is the basic component of geologic

maps. By definition, it is a three-dimensional body

of rock of essentially uniform composition formed

during some specified interval of time and that is

large enough to be shown on a conventional map.

Thus, the making of geologic maps involves subdividing surface and near-surface rocks into different

units according to their type and age. On Earth, geologic mapping involves a combination of field work,

laboratory studies, and analyses of aerial photographs. In planetary geology, geologic mapping is

done primarily by remote sensing methods--commonly interpretation of photographs. Field work is

rather costly and not always possible. Mapping

units are identified on photographs from morphology (the shape of the landforms), albedo characteristics (the range of “tone” from light to dark), color,

state of surface preservation (degree of erosion), and

other properties. Remote sensing of chemical compositions permits refinements of photogeologic

units. Once units are identified, interpretations of

how the unit was formed are made. In planetary

geologic mapping the observation and interpretation parts of a unit description are separated (see

figure 15.1).

After identifying the units and interpreting their

mode of formation, the next task in preparing a photogeologic map is to determine the stratigraphic

(age) relation among all the units. Stratigraphic relations are determined using: (a) the Principle of

Superposition, (b) the law of cross-cutting relations,

(c) embayment, and (d) impact crater distributions.

The Principle of Superposition states that rock units

are laid down one on top of the other, with the oldest (first formed) on the bottom and the youngest on

the top. The law of cross-cutting relations states that

for a rock unit to be modified (impacted, faulted,

eroded, etc.) it must first exist as a unit. In other
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Exercise Fifteen:

Introduction to Photogeologic Mapping

words, for a rock unit that is faulted, the rock is

older than the faulting event. Embayment states that

a unit “flooding into” (embaying) another unit must

be younger. On planetary surfaces, impact crater

frequency is also used in determining stratigraphic

relations. In general, older units show more craters,

larger craters, and more degraded (eroded) craters

than younger units. 

Once the stratigraphic relations have been determined, the units are listed on the map in order from

oldest (at the bottom) to youngest (at the top). This

is called the stratigraphic column. The final task,

and the primary objective in preparing the photogeologic map, is to derive a general geologic history of

the region being mapped. The geologic history synthesizes, in written format, the events that formed

the surface seen in the photo -- including interpretation of the processes in the formation of rock units

and events that have modified the units -- and is

presented in chronological order from oldest to

youngest.

Figure 15.1 shows a sample geologic map, including its unit descriptions and stratigraphic column.

The relative ages were determined in the following

manner: The cratered terrain has more (and larger)

craters than the smooth plains unit -- indicating that

the cratered terrain unit is older. In addition, fault 1

cuts across the cratered terrain, but does not continue across the smooth plains. Faulting occurred after

the formation of the cratered terrain and prior to the

formation of the smooth plains -- indicating that the

smooth plains unit is younger than the cratered terrain and fault 1. The crater and its ejecta unit occurs

on top of the smooth plains unit, and thus is

younger. Finally, fault 2 cuts across all the units,

including the crater and its ejecta unit, and is thus

the youngest event in the region. The geologic history that could be derived from this map would be

similar to the following:

“This region was cratered and then faulted by

tectonic activity. After the tectonic activity, a plains

unit was emplaced. Cratering continued after the

emplacement of the smooth plains unit, as seen by

the craters superposed on the smooth plains and the

large, young crater mapped as its own unit. Finally,

there has been a continuation (or reactivation) of

tectonic activity, indicated by the major fault which

postdates the young crater. “

Questions

The Near Side of the Moon

Examine Figure 15.2, an observatory photograph of the near side of the Moon and answer the following

questions:

1. Visually separate the different areas of the Moon into terrains (for example, continents and oceans on

Earth). List the characteristics of each terrain.

2. Which terrain do you think is the oldest? the youngest? Explain why.

This figure shows that the surface of the Moon is not the same everywhere. The terrains, however, are

not units in the strictest sense. Rather, each terrain is made up of many different units; close inspection

of Figure 15.2 shows small areas having distinctive characteristics and that, when observed on high resolution photographs or on the ground, are seen to be distinct rock units.

Examine Figure 15.3. This photo shows in greater detail the boundary between two of the terrains you

identified previously. Tape a piece of acetate or tracing paper over the photo. Mark the four corners as

reference points in case the sheet shifts while you are working on it and also to allow for overlaying

with other maps for comparison. Draw the contact between the rough highlands and the smooth plains.

Note the feature indicated by the A on the photo. This is a graben caused by tectonic activity. The feature

marked B on the photo is a ridge caused by tectonic activity. Trace these features on your map. Fill in the

unit descriptions in the space provided below. Label the units on your map.
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Exercise Fifteen:

Introduction to Photogeologic Mapping

3. What is the age relation between the graben and the highlands? (Is the graben older or younger than the

highlands?)

4. What is the age relation between the highlands and the smooth plains? What observations did you use

to decide?

5. What is the age relation between the ridge and the smooth plains?

6. What is the age relation between the ridge and the large crater on it?

Place the geologic units and structural features identified above in their correct sequence in the stratigraphic

chart below. List the oldest at the bottom and the youngest at the top.

Unit Name Observation Interpretation

Youngest

Oldest

Geologic Unit Structural Features
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Using your unit descriptions and stratigraphic chart, write a short geologic history for the area you have

mapped.

Geologic History:

Exercise Fifteen:

Introduction to Photogeologic Mapping
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Exercise Fifteen:

Introduction to Photogeologic Mapping

Figure 15.1. Sample

geologic map and

derived stratigraphic

column.

Geologic

Unit

Structural

Event

Fault 2

Fault 1

Crater and

Ejecta

Smooth

Plains

Crater

Terrain

Oldest

Youngest

Stratographic Column

Unit Name Observation

Crater and

Ejecta

Smooth

Plains

Crater

Terrain

Unit Descriptions

Interpretation

rough, blocky

surface, high

albedo, surrounds

and includes crater

smooth plains, few

craters, low albedo,

lobate (rounded)

margins

rugged, heavily

cratered plains,

high albedo

crater and ejecta

formed by impact

volcanic flow

old unit, possibly of

volcanic origin, has

had extensive

cratering
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Exercise Fifteen:

Introduction to Photogeologic Mapping

Figure 15.2. Near Side of the Moon. North is to the top. Photo courtesy of Ewen A. Whitaker, Unviersity of Arizona.
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Figure 15.3. Apollo 15 photograph of the moon. North is to the top. The small crater above the letter B is 3.8

kilometers in diameter. Apollo metric AS15 0583.

Exercise Fifteen:

Introduction to Photogeologic Mapping

10 km

N

A

B
Purpose

The objective of this exercise is to become familiar with the techniques of constructing geologic

maps of planetary surfaces, as applied to the Moon.

Upon completion of this exercise the student should

understand the concept of superposition and be

able to make interpretations about the geologic history of part of the Moon.

Materials

Suggested: clear acetate or overhead transparency, tape, overhead projector markers

Substitutions: tracing paper, colored pencils

Background

Planetary photogeologic mapping differs from

geologic mapping on Earth because field work generally is not possible. Photogeologic mapping

depends on photo interpretation, supplemented

with other remotely sensed data. Despite the lack of

“ground truth,” photogeologic maps are important

for deriving the geologic histories of planetary surfaces. It is assumed that students are familiar with

geologic processes and landforms, as investigated in

earlier exercises.

All the necessary information for completing this

exercise is contained in the student’s introduction.

This can be a difficult exercise, and student maps

will vary. Students should have some familiarity

with the general geology of the Moon, and have

completed Exercise 15. Encourage students to

record their unit descriptions before beginning to

draw the contacts, as this will help maintain consistency within each map. Contact placement will vary

with different unit choices and descriptions. The

map included in the answer key should be used as a

general guide in assessing student maps.

Science Standards

■ Physical Science

• Motions and forces

■ Earth and Space Science

• Origin and evolution of the universe

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Exercise Sixteen:

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Exercise

Sixteen

Photogeologic

Mapping of the Moon

Instructor Notes

Suggested Correlation of Topics

Geologic time, geometric relations, geomorphology, maps, remote sensing,

satellite observations, stratigraphy

3.0 hours

Exercises Two and Fifteen are suggested

as introductory exercises.
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Part A

1. Contacts are sharp; transition from plains to

mountains is abrupt; hills appear as islands in

smooth plains; relief of hills is variable; sinuous rilles appear to be controlled by hill

topography (hills predate rilles); there are

more craters on plains than on hills.

2. Smooth plains appear to be more heavily

cratered than hills; explained as function of :

1) areal exposure of plains emphasizes number of craters; 2) hard to preserve craters on

steep slopes of hills; 3) craters difficult to see

in shadows and bright hill slopes.

3. Mountainous terrain pre-dates (is older than)

smooth plains.

4. A smooth, gently undulating surface; contains

numerous sinuous rilles. One rille lies on a

topographic crest and is therefore unlikely to

be an erosional channel. The unit is probably

volcanic in origin, emplaced in part by the sinuous rilles (lava tubes/channels).

5. The hills are part of the system that surrounds Mare Imbrium and are probably related to one or more of the highly degraded and

flooded multi-ring basins. Hence, they are

analogous to crater deposits around smaller

structures.

6. Presence of possible flow scarp. Numerous

channels (rilles), some with leveed sides

(Note: channel network does not interconnect

and is therefore unlikely to be a fluvial

“drainage” system, analogous to terrestrial

watersheds—the rilles are probably lava

channels).

7. Clusters of irregular, overlapping craters—

herringbone pattern points to south-southeast. All are younger than smooth plains.

8. Secondary crater clusters from a large primary outside the field of view (somewhere to

the south-southeast).

9. Hummocky, irregular topography associated

with inner facies; radial and concentric texture in outer facies.

10. The topography is a result of ejecta from the

Euler impact event. The inner facies represents continuous deposits, modified by postimpact slumping; the outer facies is a result of

secondary cratering processes.

11. NW 33 km; NE 64 km; SE 31 km; SW 23 km.

Note: distances may vary somewhat, depending upon where contact is drawn.

12. Presence of numerous sinuous rilles around

regions of the west and south show that some

Euler ejecta deposits have been covered by

emplacement of late-stage mare lava.

13. Parts of the smooth unit post-date Euler,

other parts seem to have faint texture associated with outer ejecta facies of Euler and are

pre-Euler.

14. Crater clusters post-date Euler (are superposed on Euler ejecta), clusters post-date all

mare deposits.

15. The clusters are probably secondary craters

from some primary crater located to the

south-southeast.

Answer Key

Exercise Sixteen:

Photogeologic Mapping of the Moon
Part B

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Answer Key, continued

Unit Name Observation Interpretation

ce1 (continuous

ejecta; pre-mare

craters)

inner facies (crater rim materials) of

pre-mare craters; arranged

concentrically to crater depression

pre-mare crater material; of

early Eratosthenian age

ce2 (continous

eject; post-mare

craters)

rough hummocky inner facies of

post-mare craters; arranged

concentrically to crater depression

crater materials; of

Eratosthenian age

de (discontinuous

crater ejecta)

radial and sub-radial texture at

distal end of rim materials -

herringbone structure; at Euler,

gradational with secondaries - not

related to irregular crater clusters

crater materials; of

Eratosthenian age

cc (crater cluster)

groups of large, irregular craters; vshape pointing SSE; occur

predominantly in SE corner - one

group superposed on Euler ce2

secondary craters from a large

primary located to the SSW; of

Copernican age

mt (mountainous

terrain)

large isolated massif structures in

W and SW of map area; not

continuous - appear to proturde

through mare (smooth plains)

basin and large crater ejecta

fromed in pre-mare times; of

Imbrium age

m1 (old mare)

rough textured mare underlying

Euler ejecta; pre-Euler mare with

most primary structure degraded

or destroyed

pre-Euler mare flows; of

Eratosthenian age

m2 (young mare)

smooth mare plains overlying

Euler ejecta; contains large number

of channel-like structures (sinuous

rilles)

flows emplaced primarily by

sinuous rilles (volcanic origin);

of Eratosthenian age

Exercise Sixteen:

Photogeologic Mapping of the Moon
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Unit mt is rim and ejecta material formed by a

massive impact, or series of impacts related to the

formation of the Imbrium Basin and is the oldest

unit in this region. Cratering continued with the

formation of the ce1 craters. The smooth plains

(m1) were emplaced by volcanic activity prior to

the impact and formation of Euler crater. After

Euler was formed, volcanic activity continued

with the formation of the m2 flows. Cratering continued with the formation of the ce2 craters. The

youngest craters in the area are the cc secondary

craters from a large impact outside the map area.

Geologic Unit Structural Event Age

Youngest

cc Copernican

ce2,de Channels Eratosthenian

m2

m1 Euler impact

ce1 Eratosthenian

Oldest mt Imbrian

Answer Key, continued

Exercise Sixteen:

Photogeologic Mapping of the Moon

Youngest

Oldest

Geologic History
Euler

ce2

ce2 ce2

m1

de

m2

cc

cc

de

cc

cc

mt

cc

cc mt ce2

cc

cc

ce2

mt

mt

ce1

ce2

mt mt

mt

ce2

m2

mt

ce2

mt

cc

cc

mt

ce2

mt

mt

mt

mt

mt

cc

cc cc

cc cc

m2

cc

m1

cc

mt

mt

mt

mt

mt

cc

cc

mt

mt

mt

mt

cc

cc

mt m1

ce2

mt

m2

cc

de

m1

ce1

Euler

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Answer Key, continued

Exercise Sixteen:

Photogeologic Mapping of the Moon
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Exercise Sixteen:

Photogeologic Mapping of the Moon

Name

Exercise

Sixteen

Purpose

Through observation and analysis of photographs of the Moon you will become familiar with

the techniques of constructing geologic maps of

planetary surfaces.

Materials

Tape, clear acetate or overhead transparency,

overhead projector markers (or tracing paper and

colored pencils)

Introduction

A geologic map is a graphic portrayal of the distribution and age of rock types, structural features

such as folds and faults, and other geologic information. Such a map allows geologists to link observations made at different localities into a unified

form and to represent those observations in a form

that can be easily understood by others. One of the

first tasks in preparing a geologic map is the identification of units. By definition, a unit is a threedimensional body of rock of essentially uniform

composition formed during a specified interval of

time and that is large enough to be shown on a conventional map. Thus, the making of geologic maps

involves subdividing surface and near-surface rocks

into different units according to their type and age.

On Earth, this involves a combination of field work,

laboratory studies, and analyses of aerial photographs. In planetary geology, geologic mapping

must be done primarily by remote sensing methods,

commonly the interpretation of photographs. Units

are identified on photographs by their surface

appearance (morphology—smooth, rugged, hilly,

etc.), their albedo (how they reflect sunlight—light

to dark), their state of surface preservation (degree

of erosion), and other properties. In some cases

remote sensing of chemical compositions permits

refinements of photogeologic units.

Three decades of planetary exploration have

shown that the solid-surface planets and satellites

have been subjected to the same basic geologic

processes: volcanism, tectonism, gradation, and

impact cratering. The relative importance of each

process in shaping the surface differs from body to

body, depending on the local environment (presence of an atmosphere, running water, etc.). All four

of these processes have worked to shape the surface

of the Moon and have produced landforms and rock

units that can be recognized and mapped. An

important part of preparing a geologic map, once

the units are identified, is interpreting the geologic

process(es) responsible for the formation of each

map unit. When preparing a planetary photogeologic map, unit descriptions are divided into two

parts: the observation (what you see) and the interpretation (how you believe it formed).

After identifying the units and interpreting their

mode of formation, the next task in preparing a photogeologic map is to determine the stratigraphic

(age) relation among all the units. Stratigraphic relations are determined using: (a) the Principle of

Superposition, (b) the law of cross-cutting relations,

(c) embayment, and (d) impact crater distributions.

The Principle of Superposition states that rock units

are laid down one on top of the other, with the oldest (first formed) on the bottom and the youngest on

the top. The law of cross-cutting relations states that

for a rock unit to be modified (impacted, faulted,

eroded, etc.) it must first exist as a unit. In other

words, for a rock unit that is faulted, the rock is

older than the faulting event. Embayment states that

a unit “flooding into” (embaying) another unit must

be younger. On planetary surfaces, impact crater

frequency is also used in determining stratigraphic

relations. In general, older units show more craters,

larger craters, and more degraded (eroded) craters

than younger units. 

Once the stratigraphic relations have been determined, the units are listed on the map in order from

oldest (at the bottom) to youngest (at the top). This is

called the stratigraphic column. The final task, and

the primary objective in preparing the photogeologic

Photogeologic

Mapping of the Moon
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Exercise Sixteen:

Photogeologic Mapping of the Moon

map, is to derive a general geologic history of the

region being mapped. The geologic history synthesizes, in written format, the events that formed the

surface seen in the photo—including interpretation

of the processes in the formation of rock units and

events that have modified the units—and is presented in chronological order from oldest to

youngest.

Figure 16.1 shows a sample geologic map, including its unit descriptions and stratigraphic column.

The relative ages were determined in the following

manner: The cratered terrain has more (and larger)

craters than the smooth plains unit—indicating that

the cratered terrain unit is older. In addition, fault 1

cuts across the cratered terrain, but does not continue across the smooth plains. Faulting occurred after

the formation of the cratered terrain and prior to the

formation of the smooth plains—indicating that the

smooth plains unit is younger than the cratered terrain and fault 1. The crater and its ejecta unit occurs

on top of the smooth plains unit, and thus is

younger. Finally, fault 2 cuts across all the units,

including the crater and its ejecta unit, and is thus

the youngest event in the region. The geologic history that could be derived from this map would be

similar to the following:

“This region was cratered and then faulted by

tectonic activity. After the tectonic activity, a plains

unit was emplaced. Cratering continued after the

emplacement of the smooth plains unit, as seen by

the craters superposed on the smooth plains and the

large, young crater mapped as its own unit. Finally,

there has been a continuation (or reactivation) of

tectonic activity, indicated by the major fault which

postdates the young crater. “

The geologic mapping principles listed above

have been applied to the Moon as a whole and a

generalized geologic time scale has been derived

(Figure 16.2). Two important units on the Moon are

the Fra Mauro Formation and the Janssen

Formation, ejecta deposits from the Imbrium and

Nectaris impact basins, respectively. These are

widespread units that were formed in the hours following the gigantic impacts that excavated the

basins, and hence are excellent datum planes. Rock

samples returned from several localities on the

Moon enable radiometric dates to be placed on the

generalized time scale.

Geologic mapping of impact crater-related

deposits requires some knowledge of the impact

process. When one planetary object such as meteoroid, strikes another there is a transfer of energy

that causes the crater to form by having material

excavated from the “target” surface. Most of the

incoming object is destroyed by fragmentation,

melting, and vaporization. Figure 16.3 is a diagram

showing typical impact crater deposits. Extending

about one crater diameter outward from the rim is a

zone of continuous ejecta deposits consisting of

material thrown out from the crater (called ejecta)

and local material churned up by the ejecta.

Extending farther outward is a zone of discontinuous ejecta deposits; unlike the zone of continuous

ejecta deposits, these are surfaces that have been

affected only locally by the impact. Bright, wispy

rays extend beyond the zone of discontinuous ejecta deposits. Distinctive secondary craters formed by

blocks of ejecta occur in singlets, doublets, triplets,

chains and clusters. They often form a “herringbone” ridge pattern, the apex of which points

toward the primary, or parent crater.

On the Moon and Mercury, geologic mapping

involves distinguishing various deposits related to

impact craters. In addition, most of the terrestrial

planets have experienced volcanism that produced

vast basaltic lava flows. Samples returned by the

Apollo astronauts show that the dark, smooth areas

of the Moon, named maria, are basalt flows. Some of

these basalt flows were generated as enormous

“floods” of lava, similar to the Columbia River

Plateau of the northwest United States; others were

produced as thin sheets that were fed by rivers of

lava, visible today as sinuous rilles (Figure 16.4).

Procedure and Questions

The area you will be mapping is the Euler (pronounced ‘oiler’) crater region on the Moon. Euler is an impact

crater, 28 km in diameter, located at 23°20'N, 29°10'W, placing it on the rim of the Imbrium basin on the near

side of the Moon(see Figure 16.5). It is about 450 km northwest of the 93 km-diameter Copernicus impact

crater. The photograph (Figure 16.6) was obtained with a mapping camera on board the Apollo 17 service

module from an altitude of about 117 km. The photograph is 180 km on a side; the sun elevation angle at its

center is about 6.5°.
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Exercise Sixteen:

Photogeologic Mapping of the Moon

To establish age relations and interpret the mode of formation of the rock units in the area it is best to examine the area in detail. Enlargements of Figure 16.6 will be used for this purpose.

Part A

1. Study Figure 16.7 (an enlargement of the southwest quadrant of Figure 16.6) in detail and list observations and evidence which might establish the relative age of the rugged clusters of hills and the intervening smooth regions.

2. List possible reasons why craters are more readily apparent on the smooth regions (vs. the hills).

3. Indicate your conclusion about the relative age of the two terrains (which is older).

4. List the characteristics of the smooth unit which might bear on its mode of formation; suggest a possible

origin(s) for this unit.

5. List the characteristics of the rugged hills and suggest possible origins. Interpretations should be preliminary pending examination of the other quadrant enlargements (see also Figure 16.5).

6. Study Figure 16.8 (an enlargement of the northwest quadrant of Figure 16.6). List any additional characteristics associated with the smooth region which might bear on its mode of origin.

7. Briefly describe the several clusters of craters visible in Figure 16.8. What is their age in relation to the

smooth region?

8. Propose a tentative mode of origin for these crater clusters, including any possible directional information.

9. Study Figure 16.9 (an enlargement of the northeast quadrant of Figure 16.6). Briefly describe the various

characteristics of the topography surrounding and associated with the crater Euler.

10. Propose an origin for the topography of the material at crater Euler.

11. Study the outer boundary of the unit which includes Euler and its associated crater materials (recall

Figure 16.3). Using Figures 16.6, 16.7, 16.8, 16.9, 16.10 measure and record the distance from the rim

crest of Euler to the outer boundary of the crater materials in a NW, NE, SE, and SW direction.
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Asymmetry in deposits surrounding a crater can result from several factors including: (1) oblique

impact of projectile, (2) fractures in bedrock causing asymmetric ejection of material, (3) strong prevailing winds (on Earth and Mars), (4) later events modifying parts of the deposits, (5) topographic effects

on flow of material from craters (on Venus), (6) a combination of the above.

12. Study the stratigraphic relations around the Euler deposit and list evidence to account for the observed

deposit asymmetry.

13. Study Figure 16.10 (an enlargement of the southeast quadrant of Figure 16.6) and Figures 16.7, 16.8, and

16.9. What is the age relation of the deposit surrounding Euler and the smooth unit. Present evidence for

your conclusions.

14. Describe the large crater clusters in Figure 16.9 (craters larger than about 500 meters). What is their age

in relation to Euler? What is their age in relation to the mare deposits (smooth unit)?

15. Describe the mode of origin of these clusters and include any directional information concerning their source.

Part B

Examine Figure 16.6 in detail (as well as the enlargements of the four quadrants) and classify the terrain

into geologic units based on surface morphology, albedo, crater frequency, and other characteristics. There are

at least 3 major geologic units in the region. Tape the acetate or tracing paper over the photo (Figure 16.6). If

you are using tracing paper, tape it at the top only so that the paper can be flipped up to see the photograph.

Make reference marks in the four corners, in case the acetate or paper shifts while you are working on it , and

also to help in overlaying with other maps for comparison. Draw preliminary contacts around the units—DO

NOT WRITE ON THE PHOTO. Label the units by writing the name, or letters symbolizing the name, within

each unit. Areas of a unit need not be laterally continuous on the surface, but may exist as isolated patches.

Use symbols for features such as faults, grabens, fractures, and crater rims (see symbols sheet, Figure 16.13).

Tabulate the units on Figure 16.11 and describe their main characteristics. Names are of your choice, such as

“mountain unit,” “smooth plains.” Names should be based on observations, not interpretations of possible

mode of origin (“smooth plains” rather than “volcanic plains”). If you are using tracing paper, color the map,

using a different color for each unit.

Using the stratigraphic relations and interpretations developed in part A compile a stratigraphic column

and geologic history for the Euler region. Based on your observations, determine the stratigraphy of the units

(the relative order of units from youngest to oldest). List the units in the column “Geologic Unit” in Figure

16.12 in order from youngest at the top to oldest at the bottom. Place any structural information in the column

“Structural Events”. Use the lunar time scale to determine the age (e.g., Eratosthenian) in which the units

formed and note this information on your stratigraphic column and in the geologic history.

Exercise Sixteen:

Photogeologic Mapping of the Moon
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Figure 16.1. Sample

geologic map and

derived stratigraphic

column.

Geologic

Unit

Structural

Event

Fault 2

Fault 1

Crater and

Ejecta

Smooth

Plains

Crater

Terrain

Oldest

Youngest

Stratographic Column

Unit Name Observation

Crater and

Ejecta

Smooth

Plains

Crater

Terrain

Unit Descriptions

Interpretation

rough, blocky

surface, high

albedo, surrounds

and includes crater

smooth plains, few

craters, low albedo,

lobate (rounded)

margins

rugged, heavily

cratered plains,

high albedo

crater and ejecta

formed by impact

volcanic flow

old unit, possibly of

volcanic origin, has

had extensive

cratering

Exercise Sixteen:

Photogeologic Mapping of the Moon
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Lunar Geologic Time Scale

(after Guest and Greely, 1977)

Figure 16.2.

Exercise Sixteen:

Photogeologic Mapping of the Moon
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Figure 16.3. Diagram of typical impact crater deposits.

Figure 16.4. Diagram of a typical sinuous rille.

Exercise Sixteen:

Photogeologic Mapping of the Moon
Figure 16.5. Photograph of the near side of the moon, showing the Imbrium Basin (indicated by arrows). North is to

the top. (courtesy of Ewen A. Whitaker, Univ. of Arizona)

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Exercise Sixteen:

Photogeologic Mapping of the Moon

Figure 16.6. Photograph of the Euler crater region on the near side of the moon. North is to the top. Euler crater (the

large one) is 27 kilometers in diameter. Apollo 17 metric photo AS17 2730.

20 km

N
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Figure 16.7. Southwest quadrant of Euler region photo. North is to the top. Apollo 17 metric photo AS17 2730. 

Exercise Sixteen:

Photogeologic Mapping of the Moon

10 km
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Exercise Sixteen:

Photogeologic Mapping of the Moon

Figure 16.8. Northwest quadrant of Euler region photo. North is to the top. Scale is the same as for Figure 16.7. Apollo

17 metric photo AS17 2730. 
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Exercise Sixteen:

Photogeologic Mapping of the Moon

Figure 16.9. Northeast quadrant of Euler region photo. North is to the top. Scale is the same as for Figure 16.7. Apollo

17 metric photo AS17 2730. 
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Exercise Sixteen:

Photogeologic Mapping of the Moon

Figure 16.10. Southeast quadrant of Euler region photo. North is to the top. Scale is the same as for Figure 16.7.

Apollo 17 metric photo AS17 2730.
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Unit Name Observation Interpretation

Figure 16.11. Unit descriptions.

Exercise Sixteen:

Photogeologic Mapping of the Moon
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Geologic Unit Structural Event Age

Youngest

Oldest

Figure 16.12. Stratigraphic column.

Geologic History:

Exercise Sixteen:

Photogeologic Mapping of the Moon

Youngest

Oldest
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Purpose

The objective of this exercise is to become familiar with the techniques of constructing geologic

maps of planetary surfaces. Upon completion of this

exercise the student should understand the concept

of superposition and be able to make interpretations

about the geologic history of the area studied.

Materials

Suggested: Photomosaic MC-16 (SE) of Mars

(U.S. Geological Survey Map I-1187)*, clear acetate

or overhead transparency, overhead projector markers, tape

Substitutions: tracing paper, set of colored pencils

*This can be ordered from: Western Distribution

Branch, U.S. Geological Survey, Box 25286, Federal

Center, Denver, CO 80225.

Background

All the necessary information for completing this exercise is contained in the student’s introduction. This can be a difficult exercise, and student

maps will vary. Encourage students to record their

unit descriptions before beginning to draw the contacts, as this will help maintain consistency within

each map. Contact placement will vary with different unit choices and descriptions. The map included

in the answer key should be used as a general guide

in assessing student maps.

Science Standards

■ Physical Science

• Motions and forces

■ Earth and Space Science

• Origin and evolution of the universe

Exercise

Seventeen

Photogeologic

Mapping of Mars

Instructor Notes

Suggested Correlation of Topics

Deductive reasoning, geologic time, geometric

relations, geomorphology, maps, remote sensing,

satellite observations, stratigraphy, superposition

2.0 hours

Exercise Two and Fifteen are suggested

as introductory exercises.

Exercise Seventeen:

Photogeologic Mapping of Mars
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Map after 1) Scott et al., 1981, Map Showing Lava Flows in the Southeast Part of the Memnonia

Quadrangle of Mars, USGS Map I-1271 and 2) Craddock and Greeley, 1994, Geologic Map of the MTM -

20147 Quadrangle, Mangala Valles Region of Mars, USGS Map I-2310.

Answer Key

Unit Name Observation Interpretation

A

flat, generally featureless plains,

uniform albedo, contains faults

(graben) and ridges in some areas

probable volcanic flows, may

be mantled by wind deposited

materials

B

mottled albedo, flow appearance,

lobate margins, some channels

evident, forms broad lobes and

sheets, embays older terrain

volcanic flows, no source visible

in area

C fresh craters with complete rims

and identifiable ejecta deposits impact craters

D

rugged plains, relatively heavily

cratered, topographically higher

than surroundings, contains faults

(graben) and ridges, embayed by

younger units

old terrain of unknown origin,

possibly volcanic, has

undergone extensive cratering

E streamlined channel deposits water eroded topography and

fluvial deposits

Geologic History

The history of this area begins with the formation of the rugged plains (Unit D). This unit has

been extensively cratered. Tectonic events may

have initiated at this time. Graben in the area trend

ENE, while ridges trend NS. Tectonic activity may

have been intermittent or somewhat continuous

over time, as graben and a few ridges are found on

all units, but are most common on Unit D. Volcanic

plains (Unit B) were emplaced in the eastern section of the mapped area; the source of these flows

is not contained within the map area, but most likely is to the east. Fluvial activity, perhaps concurrent

with volcanic flow emplacement, cut topographic

features and deposited materials (Unit E) in the

north-central section of the map. The age relation

between units B and E is unknown. Large craters

and low land areas were filled by Unit A, probably

consisting of volcanic flows and a mantling

dust/sand deposit. Finally, impacts occurred forming the young craters and their ejecta blankets.

Geologic Unit Structural Event

Youngest C Graben?

A Graben?

B/E Ridges?

Oldest D Tectonics?

Exercise Seventeen:

Photogeologic Mapping of Mars

Youngest

Oldest
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Sample Photogeologic Map for the Memnoia Region, Mars

Exercise Seventeen:

Photogeologic Mapping of Mars
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Name

Exercise

Seventeen

Photogeologic

Mapping of Mars

Purpose

Through observation and analysis of the Mars

photomosaic you will become familiar with the

techniques of constructing geologic maps of planetary surfaces.

Materials

Photomosaic MC-16 (SE) of Mars, clear acetate or

overhead transparency, tape, overhead projector

markers (or use tracing paper and colored pencils)

Introduction

A geologic map is a graphic portrayal of the distribution of rock types, structural features such as folds

and faults, and other geologic information. Such a

map allows geologists to link observations made at

different localities into a unified form and to represent

those observations in a form that can be easily understood by others. One of the first tasks in preparing a

geologic map is the identification of units. By definition, a unit is a three-dimensional body of rock of

essentially uniform composition formed during some

specified interval of time and that is large enough to be

shown on a conventional map. Thus, the making of

geologic maps involves subdividing surface and nearsurface rocks into different units according to their

type and age. On Earth, this involves a combination of

field work, laboratory studies, and analyses of aerial

photographs. In planetary geology, geologic mapping

must be done primarily by remote sensing methods,

commonly the interpretation of photographs.

Mapping units are identified on photographs by their

surface appearance (morphology—smooth, rugged,

hilly, etc.), their albedo (how they reflect sunlight—

light to dark), their state of surface preservation

(degree of erosion), and other properties. In some cases

remote sensing of chemical compositions permits

refinements of photogeologic units.

Three decades of planetary exploration have shown

that the surfaces of rocky and icy planets and satellites

have all been subjected to the same basic geologic

processes: volcanism, tectonism, gradation, and

impact cratering. The relative importance of each

process in shaping the surface differs from body to

body, depending on the local environment (presence

of an atmosphere, running water, etc.). All four of the

processes listed above have worked to shape the surface of Mars. In addition to volcanism, seen in the form

of large volcanoes and extensive lava flows, and

impact cratering, Mars has undergone tectonism. This

process is indicated by the presence of faults, fractures,

and graben. Gradation has occurred on Mars through

the work of running water (in the past), wind,

periglacial processes, and landslides. All these

processes have produced landforms and rock units

that can be recognized and mapped. An important

part of preparing a geologic map, once the units have

been identified, is interpreting what geologic

process(es) was responsible for the formation of each

map unit. When preparing a planetary photogeologic

map, unit descriptions are divided into two parts: the

observation (what you see) and the interpretation

(how you think it formed).

After identifying the units and interpreting their

mode of formation, the next task in preparing the photogeologic map is to determine the stratigraphic (age)

relation among all the units. Stratigraphic relations are

determined using: a) the Principle of Superposition, b)

the law of cross-cutting relations, c) embayment, and

d) impact crater distributions. The Principle of

Superposition states that layered rock units are laid

down one on top of the other, with the oldest (first

formed) on the bottom and the youngest on the top.

The law of cross-cutting relations states that for a rock

unit to be modified (impacted, faulted, eroded, etc.) it

must first exist as a unit. In other words, for a rock unit

that is faulted—the rock is older than the faulting

event. Embayment states that a unit “flooding into”

(embaying) another unit must be younger. On planetary surfaces, impact crater frequency is also used in

determining stratigraphic relations. In general, older

units show more craters, larger craters, and more

degraded (eroded) craters than younger units. 

Exercise Seventeen:

Photogeologic Mapping of Mars
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Once the stratigraphic relations have been determined, the units are listed on the map in order from

oldest (at the bottom) to youngest (at the top). This

is called the stratigraphic column. The final task,

and the primary objective in preparing the photogeologic map, is to derive a general geologic history of the region being mapped. The geologic history synthesizes the events that formed the surface

seen in the photo—including interpretation of the

processes in the formation of rock units and events

that have modified the units—and is presented in

chronological order from oldest to youngest.

Figure 17.1 shows a sample geologic map,

including its unit descriptions and stratigraphic

column. The relative ages were determined in the

following manner: The cratered terrain has more

(and larger) craters than the smooth plains unit—

indicating that the cratered terrain unit is older. In

addition, fault 1 cuts across the cratered terrain, but

does not continue across the smooth plains.

Faulting occurred after the formation of the

cratered terrain and prior to the formation of the

smooth plains—indicating that the smooth plains

unit is younger than the cratered terrain and fault 1.

The crater and its ejecta unit occurs on top of the

smooth plains unit and thus is younger. Finally,

fault 2 cuts across all the units, including the crater

and its ejecta unit, and is thus the youngest event in

the region. The geologic history that could be

derived from this map would be similar to the following:

“This region was cratered and then faulted by

tectonic activity. After the tectonic activity, a plains

unit was emplaced. Cratering continued after the

emplacement of the smooth plains unit, as seen by

the craters superposed on the smooth plains and

the large, young crater mapped as its own unit.

Finally, there has been a continuation (or reactivation) of tectonic activity, indicated by the major

fault which postdates the young crater.“

Procedure and Questions

Exercise Seventeen:

Photogeologic Mapping of Mars

Part A: The Geologic Map

The area you will be mapping is the Memnonia

region (SE), which lies between 135° to 157.5° west

longitude and 15° to 30° south latitude. In this area, the

volcanic units of the Tharsis region flow onto the

southern cratered highlands. All four of the principal

geologic processes described above have left their

imprint on this region and the rock units resulting

from these processes can be mapped.

Examine the photomosaic in detail and identify the

geologic units based on surface morphology (hilly,

flat, etc.), albedo (light, dark), crater density, and other

appropriate characteristics. There are at least 4 major

geologic units in the region. Place the acetate (or tracing paper) over the photomosaic and tape it to the

photo. If using tracing paper, tape at the top only so

that it can be lifted up to see the image beneath. Mark

the four corners of the photomosaic to use as reference

points if the acetate (or paper) shifts, and also for overlaying with other maps for comparison. Draw preliminary contacts around the units—DO NOT WRITE

ON THE PHOTOMOSAIC. Label the units by name,

or letters symbols within each unit. Areas of a unit

need not be laterally continuous on the surface. Use

symbols for features such as faults, grabens, fractures,

and crater rims (see symbols sheet, Figure 17.2).

Tabulate the units on Figure 17.3 and describe their

main characteristics. Names are of your choice, such

as “mountain unit, “ “smooth plains”. If you are using

tracing paper, color the map, using a different color for

each unit.

Contact: dashed where

inferred; querried where

unknown

Fault: ball and bar on

downthrown side

Graben

Lineament

Ridge

Trough

Scarp: barb points downslope, line at base

Channel

Mound

Crater rim

Depression

Key to Map Symbols

Figure 17.1.
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Figure 17.2. Sample

geologic map and

derived stratigraphic

column.

Geologic

Unit

Structural

Event

Fault 2

Fault 1

Crater and

Ejecta

Smooth

Plains

Crater

Terrain

Oldest

Youngest

Stratographic Column

Unit Name Observation

Crater and

Ejecta

Smooth

Plains

Crater

Terrain

Unit Descriptions

Interpretation

rough, blocky

surface, high

albedo, surrounds

and includes crater

smooth plains, few

craters, low albedo,

lobate (rounded)

margins

rugged, heavily

cratered plains,

high albedo

crater and ejecta

formed by impact

volcanic flow

old unit, possibly of

volcanic origin, has

had extensive

cratering

Exercise Seventeen:

Photogeologic Mapping of Mars
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Exercise Seventeen:

Photogeologic Mapping of Mars

Unit Name Observation Interpretation

Figure 17.3. Unit descriptions

Part B: Regional Geologic History

Based on your observations, determine the stratigraphy of your units (the relative order of units from

youngest to oldest). List the units in the column “Geologic Unit” in Figure 17.4 in order from youngest at the

top to oldest at the bottom. Place an structural information in the column “Structural Events”. Using the stratigraphic relations and interpretations based on your examination of the photomosaic, derive a geologic history for the Memnonia region.
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Exercise Seventeen:

Photogeologic Mapping of Mars

Geologic Unit Structural Event

Youngest

Oldest

Figure 17.4. Stratigraphic column

Youngest

Oldest

Geologic History:
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Glossary

of Terms

Aeolian: Pertaining to wind. 

Albedo: The ratio of the radiation reflected by a body to the amount incident upon it, often expressed as a

percentage, as, the albedo of the Earth is 34%.

Angle of illumination: The angle that a ray of electromagnetic energy makes with the plane of a surface

(light from directly overhead is at 90°).

Atmosphere: The body of gases surrounding or comprising any planet or other celestial body, held there by

gravity.

Caldera: Large, circular to subcircular depression associated with a volcanic vent. Calderas result from collapse, explosion, or erosion. 

Cinder cone: A volcanic, conical hill formed by the accumulation of cinders and other pyroclastic materials;

slopes are usually greater than 10°.

Contact: A plane or irregular surface between two types or ages of rock.

Coriolis effect: The acceleration which a body in motion experiences when observed in a rotating frame.

This force acts at right angles to the direction of the angular velocity.

Corona: Elliptical, tectonically deformed terrains found on Venus and Miranda.

Crater: Circular depression on a surface. 

Cyclonic storm: Atmospheric disturbance with circulation of winds in a counterclockwise direction in the

northern hemisphere and in a clockwise direction in the southern hemisphere. 

Datum plane: A surface of widespread extent used as a reference for stratigraphic determinations.

Density: Measure of the concentration of matter in a substance; mass per unit volume.

Deposition: The accumulation of material by physical or chemical sedimentation. 

Dip: The angle that a surface makes with the horizontal (measured perpendicular to the strike of the surface).

Dune: Mound of fine-grained material formed by wind or water

Eddy: A temporary current, usually formed at a point at which a current passes some obstruction, or

between two adjacent currents flowing in opposite directions, or at the edge of a permanent current. 

Ejecta: The deposit surrounding an impact crater composed of material (rock fragments, glass) thrown from

the crater during its formation.

Electromagnetic spectrum: Energy in the form of radiation, all sharing the same speed of propagation (c -

speed of light) but varying in frequency and wavelength. 

Embayment: A low area containing rocks that extend into the terrain of other rocks (lap over or up against

other rock units).

Equilibrium (cratered surface): A state of “balance”, in which craters of a given size are formed and obliterated at the same rate.

Glossary of Terms
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Erosion: Process whereby materials are loosened, dissolved, or worn away, and moved from one place to

another by natural agencies. Includes weathering, solution, corrosion, and transportation.

Fault: A fracture or zone of fractures along which the sides are displaced relative to one another.

Fault, normal: Fault in which the rocks have been shifted vertically by extensional forces.

Fault, reverse: Fault in which the rocks have been shifted vertically by compressional forces.

Fault, strike-slip: Fault in which the rocks have been shifted horizontally past each other along the strike of

the fault.

Force: That which tends to put a stationary body in motion or to change the direction or speed of a moving

body.

Fracture: General term for any break in a rock or rock unit due to mechanical failure by stress (includes

cracks and joints).

Front (storm): The contact at a planet’s surface between two different air masses, commonly cold and warm.

Geologic map: A graphic record of the distribution, nature, and age relations of rock units and structural

features (such as faults) in an area.

Geomorphic: Pertaining to the surface morphology (landforms) of a planet.

Graben: An elongate crustal depression bounded by normal faults on its long sides.

Gradation: Geological process involving the weathering, erosion, transportation, and deposition of planetary materials by the agents of wind, water, ice, and gravity.

Hadley cell: A thermally driven unit of atmospheric circulation that extends in both directions from the

equator. Air rises at the equator, flows poleward, descends, and then flows back toward the equator. 

Ice: Solid formed of volatile materials, particularly water, methane, ammonia, and nitrogen.

Impact: In planetology, the collision of objects ranging in size from tiny micrometeoroids to planetesimals.

Impact cratering: Process involving impact of objects with a planetary surface. 

Kinetic energy: Energy of motion; KE = 1/2 (mass) (velocity) 2

Landform: Any feature of a surface having a distinct shape and origin.

Lava: Magma (molten rock or liquid material) that reaches the surface of a planet or satellite.

Leeward: The side located away from the wind; the sheltered side.

Limb: The edge of the apparent disk of a planetary body.

Linea: Elongate markings on a planetary surface.

Lithosphere: The stiff upper layer of a planetary body; the solid outer part of a planet; on Earth, it includes

the crust and the upper part of the mantle and is about 100 km thick.

Macula: A dark spot.

Magma: Melted or fluid rock material.

Mare (pl., maria): An area on the moon that appears darker and smoother than its surroundings; composed

primarily of basaltic lava flows.

Mass wasting: The movement of rock and soil downslope caused by gravity.

Meteor: A “shooting star”—the streak of light in the sky produced by the transit of a meteoroid through the

Earth’s atmosphere; also the glowing meteoroid itself. The term “fireball” is sometimes used for a very

bright meteor.

Meteorite: Extraterrestrial material which survives to a planetary surface as a recoverable object.

Glossary of Terms
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Meteoroid: A small particle in space.

Morphology: The external structure, form, and arrangement of rocks and solid materials in relation to the

development of landforms.

Periglacial: Processes, areas, and climates at the immediate margins of former and existing glaciers and ice

sheets, and influenced by the cold temperature of the ice.

Pit crater: An impact crater containing a central depression.

Plate tectonics: The theory of planetary dynamics in which the lithosphere is broken into individual plates

that are moved by convection of the upper mantle.

Radar: (1) A method, system, or technique of using beamed, reflected, and timed radio waves for detecting,

locating, or tracking objects (such as rockets) , for measuring altitude, etc., in any of various activities,

such as air traffic control or guidance. (2) The electronic equipment or apparatus used to generate, transmit, receive, and , usually, to display radio scanning or locating waves; a radar set.

Rays: Long, thin deposits of ejecta thrown out radial to young impact craters.

Regio: A large area on a planetary surface having distinctive albedo markings.

Rift zone: A belt of strike-slip or normal faults in close proximity to each other.

Rille: Trench or crack-like valleys, up to several hundred kilometers long and 1 to 2 kilometers wide. May

be sinuous in form.

Rotation: Turning of a body about an internal axis, as a rotation of Earth.

Saltation: A mode of sediment transport in which the particles are moved progressively forward in a series

of short intermittent leaps, jumps, hops, or bounces.

Satellite: An attendant body that revolves about another body, the primary.

Scarp: Cliff produced by tectonic, impact, or erosion processes.

Secondary crater: Crater formed by ejecta thrown from a “primary” crater.

Shield volcano: A volcanic mountain in the shape of a broad, flattened dome.

Sinuous rille: see Rille

Slip face: The steeply sloping surface on the lee side of a dune, standing at or near the angle of repose of

loose sand, and advancing downwind by a succession of slides wherever that angle is exceeded.

Strata: layers of rock (singular = stratum) 

Stratigraphic column: Diagram that shows the relative ages of units within an area (oldest at the bottom,

youngest at the top) 

Stratigraphic relations: see Stratigraphy

Stratigraphy: Science of rock strata; concerned with the original succession and age relations of rock strata

as well as their form, distribution and composition. 

Strike: The azimuth or trend taken by a rock layer or structural surface.

Superposition (principle of): The principle that, in a series of strata that has not been overturned, the oldest

rocks are at the bottom and the youngest are at the top. 

Suspension: A mode of sediment transport in which the upward currents in eddies of turbulent flow are

capable of supporting the weight of sediment particles and keeping them indefinitely held in the surrounding fluid (air or water).

Tectonic: Refers to deformation of planetary materials, as in faulting of Earth’s crust.

Tectonism: Process involving movement of the lithosphere. 

Terminator: The line of sunrise or sunset on a planet or satellite.

Glossary of Terms
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Terrain: A region of a surface sharing common characteristics ( as in “mountainous terrain”). 

Terrestrial: Of or pertaining to Earth or earthlike.

Tidal heating: The process of frictional heating of a planetary object by the alternate growth and decay of a

tide in its lithosphere. 

Topography: The general configuration of a surface, including its relief and the position of features.

Traction: A mode of sediment transport in which the particles are swept along, on, near, or immediately

above and parallel to a bottom surface by rolling, sliding, pushing, or impact of saltating grains.

Unit: Three-dimensional body of rock with uniform characteristics and formed within a specific period of

time. 

Vertical exaggeration: The apparent increase in relief as seen in a stereoscopic image.

Volcanism: The process by which magma and its associated gases rise into the crust, and are extruded onto

the surface and into the atmosphere.

Vortices: Revolving motions within fluid flow.

Wavelength: The distance between successive wavecrests, or other equivalent points, in a series of harmonic

waves. 

Weathering: Chemical and physical alteration of materials exposed to the environment on or near the surface of a planetary object.

Wind streak: Zone where sediments have been preferentially deposited, eroded, or protected from wind erosion. Often form “tails” on the lee side of obstacles.

Windward: The side located toward the direction form which the wind is blowing; facing the wind.

Glossary of Terms
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Planetary Geology Resources

Planetary

Geology

Resources

1.1 Undergraduate geology textbooks.

There are dozens of college freshman textbooks

that introduce geology. Most are similarly organized

and cover the same basic material. Any college or

university which teaches geology or earth science

will carry one or more of these in their bookstore.

1.2 Planetary science textbooks.

These publications cover general planetary science and typically include chapters on each planet

and planetary system. Most of these books assume

a fundamental background in the sciences.

Beatty, J. K., and Chaikin, A., eds. (1990). The New

Solar System, Cambridge, MA: Sky Publishing

Corp. and Cambridge University Press, 326 pp.

Carr, M.H., Saunders, R.S., Strom, R.G., and

Wilhelms, D.E. (1984). The Geology of the

Terrestrial Planets, Washington, DC: National

Aeronautics and Space Administration, 317 pp.

Christiansen, E.H. and Hamblin, W.K. (1995).

Exploring the Planets. Englewood Cliffs, New

Jersey: Prentice Hall, 500 pp.

Francis, Peter (1981). The Planets, New York:

Penguin Books, 411 pp.

Greeley, Ronald (1994). Planetary Landscapes, New

York: Chapman and Hall, 286 pp.

Guest, J.E. (1979). Planetary Geology, London: David

and Charles (Publ.) , 208 pp.

Hamblin, W.K., and Christiansen, E.H. (1990).

Exploring the Planets, New York: Macmillan

Publishing Co., 451 pp.

Hartmann, William K. (1983). Moons and Planets,

2nd ed., Belmont, CA: Wadsworth Publishing

Co., 509 pp.

Morrison, D., and Owen, T. (1988). The Planetary

System, Reading, MA: Addison-Wesley

Publishing Co., 519 pp.

Murray, B., Malin, M.C., and Greeley, R. (1981).

Earthlike Planets: Surfaces of Mercury, Venus,

Earth, Moon, Mars, San Francisco, CA: W.H.

Freeman and Co., 387 pp.

1.3 Reference books.

These publications are collections of review

papers or deal with focused topics. They serve as

research resources at a professional level. Some can

be used in advanced classes.

Atreya, S.K., Pollack, J.B., and Matthews, M.S.,

(1989). Origin and Evolution of Planetary and

Satellite Atmospheres, Tucson, AZ: The

University of Arizona Press, 881 pp.

Barnes, C. W. (1980). Earth, Time, and Life—An

Introduction to Geology, New York, NY: John

Wiley & Sons, Inc., 583 pp.

Barsukov, V.L., et al., eds. (1992). Venus Geology,

Geochemistry, and Geophysics: Research Results

from the Soviet Union, Tucson, AZ: The

University of Arizona Press, 421 pp.

Bergstralh, J. T., Miner, E. D. and Matthews, M. S.,

eds. (1991). Uranus, Tucson, AZ: The University

of Arizona Press, 1076 pp.

Binzel, R. P., Gehrels, T., and Matthews, M. S., eds.

(1990). Asteroids II, Tucson, AZ: The University

of Arizona Press, 1258 pp.

Bullard, F. M. (1976). Volcanoes of the Earth, Austin,

TX: University of Texas Press, 579 pp.

Burns, J. W., ed. (1977). Planetary Satellites, Tucson,

AZ: The University of Arizona Press, 598 pp.

Burns, J. A., and Matthews, M. S., eds. (1986).

Satellites, Tucson: University of Arizona Press,

1021 pp.

Carr, M. H. (1981). The Surface of Mars, New Haven,

CT: Yale University, 232 pp.

Cattermole, P. (1992). Mars: The Story of the Red

Planet. London: Chapman and Hall, 224 pp.
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Cattermole, P. (1994). Venus: The Geological Story.

Baltimore: The Johns Hopkins University

Press, 250 pp.

Christianson, N. B. (1989). Earth Has a Cold Heart,

Glendale, AZ: Ne-do Press, 202 pp.

Cox, A.N., Livingston, W.C. and Matthews, M.S.,

eds. (1992). Solar Interior and Atmosphere,

Tucson, AZ: The University of Arizona Press,

1416 pp.

Frazier, K. (1985). Solar System: Planet Earth,

Alexandria, VA: Time-Life Books, 176 pp.

Gallant, R. (1964). Bombarded Earth, London,

England: John Bkaer Publishers, Ltd., 256 pp.

Gehrels, T., and Matthews, M. S., eds. (1984).

Saturn, Tucson, AZ: The University of Arizona

Press, 968 pp.

Gehrels, T., ed. (1976). Jupiter, Tucson, AZ: The

University of Arizona Press, 1254 pp.

Greeley, R., and Batson, R. (1997). The NASA Atlas

of the Solar System. Cambridge, England:

Cambridge University Press, 369 pp.

Greenberg, R., Brahic, W., eds. (1984). Planetary

Rings, Tucson, AZ: The University of Arizona

Press, 784 pp.

Glass, B.P. (1982). Introduction to Planetary Geology,

New York, NY: Press Syndicate of the

University of Cambridge, 469 pp.

Hamblin, W. K. (1975). The Earth’s Dynamic Systems,

Minneapolis, MN: Burgess Publishing

Company, 578 pp.

Hartmann, W. K., (1983). Moons and Planets,

Belmont, CA: Wadsworth Publishing

Company, 509 pp.

Hunten, D.M., Colin, L., Donahue, T.M., and

Moroz, V.I., eds.(1991). Venus, Tucson, AZ: The

University of Arizona Press, 1143 pp.

Kieffer, H.H., Jakosky, B.M., Snyder, C.W., and

Matthews, M.S., eds. (1992). Mars, Tucson, AZ:

The University of Arizona Press, 1498 pp.

Mark, K., ed. (1987). Meteorite Craters, Tucson, AZ:

The University of Arizona Press, 288 pp.

Miller, P., Beer, D., Brown, A. H. (1985). Atlas of

North America, Washington, DC: National

Geographic Society, 264 pp.

Miller, V. C., Miller, C. F. (1961). Photogeology, New

York, NY: McGraw-Hill Book Company, Inc.,

243 pp.

Morrison, D., ed. (1982). Satellites of Jupiter, Tucson,

AZ: The University of Arizona Press, 972 pp.

Newsom, H. E., Jones, J. H. (1990). Origin of the

Earth, New York, NY: Oxford University Press,

378 pp.

Palmer, A. R. (1992). The Geology of North America

Series, Boulder, CO: The Geological Society of

America.

Péwé, T. L., ed. (1981). Desert Dust: Origin,

Characteristics, and Effect on Man, Boulder, CO:

The Geological Society of America, Inc., 303 pp.

Roberts, J. L. (1982). Introduction to Geological Maps

and Structures, Elmsford, NY: Pergamon Press,

Ltd., 332 pp.

Roddy, D. J., Pepin, R. O., Merrill, R. B., eds. (1976).

Impact and Explosion Cratering: Planetary and

Terrestrial Implications, Elmsford, NY: Pergamon

Press, 1301 pp.

Rothery, D.A., (1992). Satellites of the Outer Planets:

Worlds in their Own Right, Oxford, England:

Clarendon, 208 pp. 

Scientific American (1983). The Planets, San

Francisco, CA: W. H. Freeman and Company,

132 pp. 

Shupe, J. F., et al., (1992). Atlas of the World: Revised

Sixth Edition, Washington, DC: National

Geographic Society, 136 pp.

Sonett, C.P., Giampapa, M.S. and Matthews, M.S.,

eds. (1992). The Sun in Time, Tucson: University

of Arizona Press, 990 pp.

Walls, J. (1980). Land, Man, and Sand, New York,

NY: MacMillan Publishing Co., Inc., 336 pp.

Tilling, R. I., ed. (1988). How Volcanoes Work,

Washington, DC: American Geophysical

Union, 14,880 pp.

Vilas, F., Chapman, C.R., Matthews, M.S., eds.

(1988). Mercury, Tucson, AZ: The University of

Arizona Press, 794 pp.

Walls, J. (1980). Land, Man, and Sand, New York,

NY: MacMillan Publishing Co., Inc., 336 pp.

Wilhelms, D.E. (1987). The Geologic History of the

Moon, U.S. Geological Survey Professional

Paper 1348, Washington, DC: U.S. Govt.

Printing Office, 328 pp.

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Planetary Geology Resources

1.4 NASA publications.

NASA publishes a wide variety of books dealing with missions, mission results, and planetary exploration, as well as planetary map atlases. Although many of these are no longer available, copies are usually

contained in libraries which carry U.S. Government publications.

Object

Earth

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Year

1980

1964

1965

1965

1966

1966

1966

1966

1969

1969

1969

1970

1970

Serial

SP-403

SP-61

SP-62

SP-63

SP-111

SP-112

SP-126

JPL-TR

32-800

SP-184

SP-214

SP-201

SP-242

SP-200

Title

Volcanic Features of Hawaii: A

Basis for Comparison with Mars

Ranger VII photograph of the

Moon, Part I, Camera A series

Ranger VII photographs of the

Moon, Camera B series

Ranger VII photographs of the

Moon, Camera P series

Ranger VIII photographs of the

Moon, Cameras A, B, P

Ranger IX photographs of the

Moon

Surveyor I: a preliminary report

Ranger VIII and IX experimenters’ analysis and interpretations

Surveyor: program results

Apollo 11 preliminary science

report

Apollo 8, photography and visual

observations

Guide to Lunar orbiter photographs

The Moon as viewed by Lunar

orbiter

Notes

Photographic collection

Photographic collection

Photographic collection

Photographic collections

Mission description and science results

Mission description with photographs; includes descriptions and results from various

experiments on board the

command module and/or

lander spacecraft

Explains camera system and

gives footprints

Mission description and photographs; includes descriptions and results from various

experiments on board the

command module and/or

lander spacecraft
232

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Object

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Moon

Year

1971

1971

1971

1971

1971

1971

1972

1972

1972

1972

1973

1974

1973

1975

1978

Serial

SP-241

SP-206

SP-232

SP-238

SP-272

SP-246

SP-315

SP-289

SP-284

SP-306

SP-330

EP-100

SP-341

SP-350

SP-362

Title

Atlas and gazeteer of the near side

of the Moon

Lunar orbiter photographic atlas of

the Moon

Apollo 10, photography and visual

observations

Apollo 11 mission report

Apollo 14 preliminary science

report

Lunar photographs from Apollo 8,

10, 11

Apollo 16 preliminary science

report

Apollo 15 preliminary science

report

Analysis of Surveyor 3 material

and photographs returned by

Apollo 12

Compositions of major and minor

minerals in five Apollo 12 crystalline rocks

Apollo 17 preliminary science

report

Apollo

Atlas of Surveyor 5 television data

Apollo expedition to the Moon

Apollo over the Moon

Notes

Lunar orbiter photographs

with place names

Photographic collection

Mission description with photographs; includes descriptions and results from various

experiments on board the

command module and/or

lander spacecraft

Description of samples

Mission description with photographs; includes descriptions and results from various

experiments on board the

command module and/or

lander spacecraft

Public information booklet

Photographs with short captions

Mission description with photographs; general public

Summary of Apollo missions to

the Moon; color photographs

and science discussions

Planetary Geology Resources
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Object

Mars

Mars

Mars

Mars

Mars

Mars

Mars

Mars

Mars

Mars

Mars

Mars

Mars

Mars

Mercury

Mercury

Venus

Venus

Year

1968

1971

1974

1974

1974

1975

1979

1980

1980

1980

1981

1982

1983

1984

1978

1978

1975

1983

Serial

SP-179

SP-263

SP-334

SP-329

SP-337

SP-425

SP-438

SP-444

SP-441

CR-3326

SP-429

CR-3568

RP-1093

SP-4212

SP-423

SP-424

SP-382

SP-461

Title

The book of Mars

The Mariner 6 and 7 missions to

Mars

The Viking mission to Mars

Mars as viewed by Mariner 9

The new Mars, the discovery of

Mariner 9

The Martian landscape

Atlas of Mars, the 1:5000000 map

series

Images of Mars—the Viking

extended mission

Viking orbiter views of Mars

The mosaics of Mars as seen by the

Viking lander cameras

Viking site selection and certification

Viking lander atlas of Mars

A catalog of selected Viking orbiter

images

On Mars, exploration of the red

planet 1958–1978

Atlas of Mercury

The voyage of Mariner 10

The atmosphere of Venus

Pioneer Venus

Notes

Mission description and photographic collection

Photographs with science

Photographs with science

Mission description and photographs for Viking

Map and photomosaic collection

Photograph collection

Photograph collection with

science

Photomosaics based on Mars

charts; gives frame locations

Lander photographs and

maps

Photomosaics based on Mars

charts; gives frame locations

History of missions and

explorations

Synopsis of Mariner 10

results; collection of photographs and USGS charts

Mission description

Popularized account of mission with discussion of science results

Planetary Geology Resources
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

Object

Jupiter

Jupiter

Jupiter

Jupiter

Jupiter/

Saturn

Jupiter/

Saturn

Saturn

Saturn

Saturn

Saturn

Saturn

Saturn

general

general

general

general

general

Year

1971

1974

1980

1989

1977

1980

1974

1974

1980

1982

1984

1978

1971

1976

1981

1984

1997

Serial

SP-268

SP-349

SP-439

SP-494

SP-420

SP-446

SP-340

SP-343

JPL-400-100

SP-451

SP-474

CP-2068

SP-267

SP-345

EP-177

SP-469

Title

The Pioneer mission to Jupiter

Pioneer Odyssey—encounter with

a giant

Voyage to Jupiter

Time-variable phenomena in the

jovian system

Voyager to Jupiter and Saturn

Pioneer: first to Jupiter, Saturn,

and beyond

The atmosphere of Titan

The rings of Saturn

Voyager I encounters with Saturn

Voyages to Saturn

Voyager I and II atlas of six saturnian satellites

The Saturn System

Physical studies of the minor planets

Evolution of the Solar System

A meeting with the universe

The geology of the terrestrial planets

The NASA atlas of the Solar System

Notes

Mission description and photographic collection

Popularized account of mission with discussion

Public information booklet

Popularized account of mission with discussion of science results

Conference proceedings

Popularized account of Solar

System exploration

An introduction to Mercury,

Venus, Earth, Moon, and Mars,

and a chapter on asteroids,

comets, and planet formation

Cambridge Univerity Press

Planetary Geology Resources
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Planet Mission Journal

Mercury Mariner 10 Science, 1974, 185, no. 4146

Mercury Mariner 10 J. Geophys. Res., 1975, 80, no. 17

Mercury Mariner 10 Phys. Earth Planet. Int., 1977, 15, nos. 2 and 3

Mercury Mariner 10 Icarus, 1976, 28, no. 4

Venus Mariner 10 Science, 1974, 183, no. 4131

Venus Pioneer Science, 1979, 203, no. 4382

Venus Pioneer Science, 1979, 205, no. 4401

Venus Pioneer J. Geophys. Res., 1980, 85, no. A13

Venus general Icarus, 1982, 51, no. 2

Venus general Icarus, 1982, 52, no. 2

Venus Vega Science, 1986, 231, no. 4744

Venus Magellan Science, 1991, 252, no. 5003

Venus Magellan J. Geophys. Res., 1992, 97, nos. E8 and E9

Moon Apollo II Science, 1970, 167, no. 3918

Moon Apollo The Moon, 1974, 9

Moon general Rev. Geophys. Space Phys., 1974, 12, no. 1

Moon general The Moon, 1975, 13, nos. 1,2 and 3

Moon Galileo Science, 1992, 255, no. 5044

Mars Mariner 6 and 7 J. Geophys. Res., 1971, 76, no. 2

Mars Mariner 9 Icarus, 1972, 17, no. 2

Mars Mariner 9 Icarus, 1973, 18, no. 1

Mars Mariner 9 J. Geophys. Res., 1973, 78, no. 20

Mars Mariner 9 Icarus, 1974, 22, no. 3

Mars Viking 1 Science, 1976, 193, no. 4255

Mars Viking 1 and 2 Science, 1976, 194, no. 4260

Mars Viking J. Geophys. Res., 1977, 82, no. 28

Mars Viking Icarus, 1978, 34, no. 3

Mars general J. Geophys. Res., 1979, 84, no. B14

Mars general Icarus, 1981, 45, nos. 1 and 2

Mars general Icarus, 1982, 50, nos. 2 and 3

Mars general J. Geophys. Res., 1982, 87, no. B12

Mars general J. Geophys. Res., 1990, 95, no. B9

Jupiter Pioneer 11 Science, 1975, 188, no. 4187

Jupiter Voyager 1 Nature, 1979, 280, no. 5725

Jupiter Voyager 1 Science, 1979, 204, no. 4396

Jupiter Voyager 2 Science, 1979, 206, no. 4421

Jupiter Voyager J. Geophys. Res., 1981, 86, no. A10

Saturn Pioneer 11 Science, 1980, 207, no. 4429

Saturn Voyager 1 Nature, 1981, 292, no. 5825

Saturn Voyager 1 Science, 1981, 212, no. 4491

Saturn Voyager 2 Science, 1982, 215, no. 4532

Saturn Voyager Icarus, 1983, 53, no. 2

Uranus Voyager 2 Science, 1986, 233, no. 4739

Neptune Voyager 2 Science, 1989, 246, no. 4936

Neptune Voyager 2 J. Geophys. Res., 1991, 96, supplement

Neptune-Triton Voyager 2 Science, 1990, 250, no. 4979

Comet Halley 5 missions Nature, 1986

Planetary Geology Resources
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Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

1.6 Regional Planetary Image Facilities.

In a quarter century of solar system exploration,

nearly a million images have been obtained of the

planets and their satellites. Some 17 facilities exist

worldwide which contain archives of planetary

images. These facilities are open to the public for aid

in finding specific images. They do not, however,

provide copies of photographs (see Section 1.8).

Arizona State University, SPL, Department of

Geology, Box 871404, Tempe, AZ 85287-1404

University of Arizona, RPIF, Lunar and Planetary

Lab, Tucson, AZ 85721 

Brown University, RPIF, Box 1846, Department of

Geological Sciences, Providence, RI 02912

Cornell University, SPIF, 317 Space Sciences

Building, Ithaca, NY 14885

Deutsche Forschungsanstalt fuer Luftund

Raumfahrt e.V. (DLR) , Regional Planetary

Image Facility, Institute for Planetary

Exploration, Rudower Chaussee 5, 0-1199

Berlin, Germany

University of Hawaii, RPIF, Hawaii Institute of

Geophysics, Planetary Geoscience Division,

Honolulu, HI 96822

Institute of Space and Astronomical Sciences,

Regional Planetary Image Facility, 3-1-1

Yoshinodai, Sagamihara-shi, Kanagawa 229,

Japan

Israeli Regional Planetary Image Facility, BenGurion University of the Negev, P.O. Box 653,

Beer-Sheva, 84105, Israel.

Jet Propulsion Laboratory, RPIF, MS 202-101, 4800

Oak Grove Drive, Pasadena, CA 91109

University of London Observatory, Regional

Planetary Image Facility, 33/35 Daws Lane,

Observatory Annexe, London, NW7 4SD,

England

Lunar and Planetary Institute, Center for

Information Research Services, 3600 Bay Area

Blvd., Houston, TX 77058

University of Paris-Sud, Phototheque Plantaire

de'Orsay, Laboratoire de Geologie Dynamique

de la Terre et des Plantes, Department des

Sciences de la Terre, Batiment 509, F-91, 405

Orsay Cedex, France

University of Oulu, Regional Planetary Image

Facility, Department of Astronomy, 90570

Oulu, Finland

Southern Europe Regional Planetary Image Facility,

CNR Institutio Astrofisica Spaziale, Reparto di

Planetologia, Viale Dell' Universita, 11, 00185

Roma, Italy

Smithsonian Institution, RPIF, Room 3773, National

Air and Space Museum, Washington, DC

20560

U.S. Geological Survey, RPIF, Branch of

Astrogeologic Studies, 2255 N. Gemini Drive,

Flagstaff, AZ 86001

Washington University, RPIF, Box 1169, Department

of Earth and Planetary Sciences, One Brookings

Drive, St. Louis, MO 63130-4899 

1.7 Videos

The following sources have video and/or films

on planetary science topics. Most will provide catalogs or lists on request.

1. Instructional Video

P.O. Box 21

Maumee, Ohio 43537

2. The Planetary Society

65 North Catalina Ave

Pasadena, CA 91106

(818) 793-5100

3. Michigan Technological University

Video Marketing

1400 Townsend Drive

Houghton, MI 49931-1295

(906) 487-2585

4. Gould Media, Inc.

44 Parkway West

Mt. Vernon, NY 10552-1194

(914) 664-3285

FAX (914) 664-0312

5. Finley-Holiday Film Corp.

12607 E. Philadelphia St.

P.O. Box 619

Whittier, CA 90601

(310) 945-3325

6. NASA CORE

Lorain County Joint Vocational School

15181 Route 58 South

Oberlin, OH 44074

(440) 774-1051 ext. 293/249

7. National Air and Space Museum

Smithsonian Institution

Educational Resource Center, MRC 305

Washington, DC 20560

(202) 786-2109

Planetary Geology Resources
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EG-1998-03-109-HQ Activities in Planetary Geology for the Physical and Earth Sciences

8. Films for the Humanities & Sciences

P. O. Box 2053

Princeton, NJ 08543-2053

9. Astronomical Society of the Pacific

390 Ashton Avenue

San Francisco, CA 94112

(800) 335-2624

10. Instructional Video

P. O. Box 21

Maumee, OH 43537

(419) 865-7670

FAX (419) 867-3813

11. JLM Visuals

1208 Bridge Street

Grafton, WI 53024-1946

(414) 377-7775

12. Sky Publishing Corporation

P. O. Box 9111

Belmont, MA 02178-9111

(800) 253-9245

13. Crystal Productions

Box 2159

Glenview, IL 60025

(800) 255-8629

FAX (708) 657-8149

1.8 CD-ROMs

1. Hopkins Technology

421 Hazel Lane

Suite 700

Hopkins, Minnesota 55343-7116

2. National Space Science Data Center

Code 633

Goddard Space Flight Center

Greenbelt, MD 20771

(301) 286-6695

3. Astronomical Society of the Pacific

390 Ashton Avenue

San Francisco, CA 94112

(800) 335-2624

4. Sky Publishing Corporation

P. O. Box 9111

Belmont, MA 02178-9111

(800) 253-9245

5. Crystal Productions

Box 2159

Glenview, IL 60025

(800) 255-8629

FAX (708) 657-8149

1.9 Slide sets

1. Astronomical Society of the Pacific

390 Ashton Ave

San Francisco, CA 94112

(800) 335-2624

2. Finley-Holiday Film Corp.

12607 E. Philadelphia St.

P.O. Box 619

Whittier, CA 90601

(310) 945-3325

3. Lunar and Planetary Institute

3600 Bay Area Blvd.

Houston, TX 77058

(713) 486-2100

4. Gould Media, Inc.

44 Parkway West

Mt. Vernon, NY 10552-1194

(914) 664-3285

FAX (914) 664-0312

5. American Geophysical Union

2000 Florida Avenue, N.W.

Washington, DC 20009

(800) 966-2481 (North America only) 

(202) 462-6900

6. NESTA/MESTA Publications

c/o Lisa Bouda

28815 Ironwood

Warren, MI 48093

7. National Association of Geology Teachers

P. O. Box 5443

Bellingham, WA 98227-5443

8. Sky Publishing Corporation

P. O. Box 9111

Belmont, MA 02178-9111

(800) 253-9245

9. Crystal Productions

Box 2159

Glenview, IL 60025

(800) 255-8629

FAX (708) 657-8149

1.10Maps

1. Earth Science Information Center

U. S. Geological Survey

507 National Center

Reston, VA 22092

(703) 860-6045

Planetary Geology Resources
238

Activities in Planetary Geology for the Physical and Earth Sciences EG-1998-03-109-HQ

2. Map Link

25 Eat Mason

Santa Barbara, CA 93101

(805) 965-4402

3. National Space Science Data Center (NSSDC) 

Code 633

Goddard Space Flight Center

Greenbelt, MD 20771

(301) 286-6695

4. U. S. Geological Survey

Distribution Branch

Box 25286 Federal Center

Denver, CO 80225

(303) 234-3832

1.11 Miscellaneous Products (globes, posters, equipment) 

1. Crystal Productions

Box 2159

Glenview, IL 60025

(800) 255-8629

FAX (708) 657-8149

2. Sky Publishing Corporation

P. O. Box 9111

Belmont, MA 02178-9111

(800) 253-9245

3. Astronomical Society of the Pacific

390 Ashton Ave

San Francisco, CA 94112

(800) 335-2624

4. The Planetary Society

65 North Catalina Ave

Pasadena, CA 91106

(818) 793-5100

5. Lunar Sample Curator (Apollo lunar samples

for Colleges/Universities only) 

SN2 NASA/Johnson Space Center

Houston, TX 77058-3698

FAX (713) 483-2911

A Note About Photographs

An essential part of Planetary Geology is the use

of spacecraft photographs. Ideally each studentteam should have access to glossy photographic

prints for use during the laboratory exercises.

Photocopies of the pictures in this book (such as

Xerox copies) generally lack sufficient detail to be

useful. Offset printing is slightly better, but again

this process is at least three generations removed

from the original product.

Glossy prints or copy negatives can be obtained

for a nominal cost (in some cases for no charge)

from various sources. Each spacecraft photograph

caption in this book contains the necessary picture

identification numbers to help you in obtaining the

photos. Usually the mission name (Apollo, Viking,

etc.) and frame number is sufficient identification.

Listed below are sources of space photography.

Instructions for ordering photography will be provided upon written request. Be sure to include

your name, title, the fact that the photographs will

be used at a non-profit educational institution, and

specific photograph numbers.

For planetary mission photography:

National Space Science Data Center

Code 633

Goddard Space Flight Center

Greenbelt, MD 20771

For Earth photography:

EROS Data Center

U.S. Geological Survey

Sioux Falls, SD 57198

For photographs indicating Arizona State

University as their source, contact:

Arizona State University

Space Photography Laboratory

Department of Geology

Box 871404

Tempe, AZ 85287-1404

Planetary Geology Resources
Planetary Geology—A Teacher’s Guide

with Activities in Physical and Earth Sciences

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