Why Geology Matters: Decoding the Past, Anticipating the Future

251 Pages·2012·2.47 MB·English

by  Doug Macdougall

The publisher gratefully acknowledges the
generous support of the General Endowment Fund of
the University of California Press Foundation.
Why Geology Matters
Decoding the Past,
Anticipating the Future
Doug Macdougall

UNIVERSITY OF CALIFORNIA PRESS
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University of California Press
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London, England
© 2011 by The Regents of the University of California Library of Congress Cataloging-in-Publication Data
Macdougall, J. D., 1944– Why geology matters : decoding the past, anticipating the future / Doug
Macdougall. — 1
p. cm.
Includes bibliographical references and index.
ISBN 978-0-520-26642-1 (hardback) 1. Historical geology. I. Title.
QE28.3.M334 2011
551.7—dc22
2010043748
Manufactured in the United States of America 20 19 18 17 16 15 14 13 12 11
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For Sheila, as always
CONTENTS

List of Illustrations
Preface
Acknowledgments
1. Set in Stone
2. Building Our Planet
3. Close Encounters
4. The First Two Billion Years
5. Wandering Plates
6. Shaky Foundations
7. Mountains, Life, and the Big Chill
8. Cold Times
9. The Great Warming
10. Reading LIPs
11. Restless Giants
12. Swimming, Crawling, and Flying toward the Present
13. Why Geology Matters
Bibliography and Further Reading
Index
ILLUSTRATIONS

1. The geological timescale
2. Sedimentary layers spanning the Permian-Triassic boundary
3. The interior structure of the Earth
4. Barringer Crater, Arizona
5. Effects of the Tunguska impact, Siberia
6. Map of Chicxulub Crater, Yucatán, Mexico
7. Size-frequency diagram for impacts on the Earth
8. The asteroid Eros
9. Time line of the Earth's first two billion years
10. Fossil and living stromatolites
11. The major tectonic plates
12. Seafloor magnetic polarity stripes
13. Cross-section of a subduction zone
14. Cross-section showing mantle, crust, and lithosphere
15. World earthquake locations between 1963 and 1998
16. The San Andreas Fault, California
17. A precariously balanced rock, California
18. Location of the 2008 earthquake in Sichuan, China
19. Map of the Reelfoot Rift, southeastern United States
20. Map of Archean-age crust
21. Time line of the Proterozoic eon
22. Oxygen isotope data for the Camp Century (Greenland) ice core
23. Four hundred thousand years of data from the Vostok (Antarctica) ice core
24. Greenland temperatures over the past 50,000 years
25. Pathways of the carbon cycle
26. Sediment core data for the Paleocene-Eocene Thermal Maximum
27. The continents at the time of the Caribbean LIP
28. Rhino fossils at Ashfall Fossil Beds State Historical Park, Nebraska
29. Volume comparison for several large volcanic eruptions
30. Map of calderas formed by the Yellowstone hotspot
31. Time line of the Phanerozoic eon
32. Biodiversity through the Ordovician-Silurian boundary
33. World paleomaps for the Phanerozoic eon
PREFACE
The earth is not a mere fragment of dead history, stratum upon stratum like the leaves of a book, to
be studied by geologists and antiquaries chiefly, but living poetry like the leaves of a tree, which
precede flowers and fruit—not a fossil earth, but a living earth.
Henry David Thoreau, Walden

In this excerpt from Walden, Thoreau inadvertently touched on something
geologists and other scientists who study the Earth have appreciated for a long
time but that has become increasingly important for understanding our planet in
recent years: the Earth, far from being static, is dynamic and ever changing. Not
a living Earth, exactly, but an Earth with different parts that continually interact
in ways that have produced monumental changes over its long history. One way
to read that history is through Thoreau's strata, “like the leaves of a book”; there
are other ways, too, as will become apparent in the chapters that follow.
“History repeats itself” is an adage usually invoked to remind us that by
studying history we may be able to avoid mistakes of the past. That may even be
true, at least some of the time. Yet there are those—like Nassim Taleb, author of
The Black Swan—who argue just the opposite, that history is not a good guide to
the future and that the world is shaped by events that are rare or unprecedented
and therefore largely unpredictable. Still, even proponents of this point of view
don't advocate that we all become fatalists, just that we learn to expect the
unexpected. But if that is so, should we study history at all?
For the Earth, that is an easy question to answer, because only by
understanding our planet's past can we anticipate its future. It is true that Nature
can confront us with the unexpected: a “freak” storm, a devastating earthquake
or tsunami, an asteroid impact. But these are only unexpected because they are
rare in human experience. They are all things that have happened repeatedly
during the Earth's history, and they obey the natural laws of physics and
chemistry. That is why decoding the Earth's past is so important: the same
physical and chemical principles that have governed our planet since its
formation will also apply in the future. History really will repeat itself—if not in