Table Of ContentliCJE AGlE§
liCJE AGJE§
§OlLVTING THE MYSTERY
John Imbrie and
Katherine Palmer Imbrie
M
©John Imbrie and Katherine Palmer Imbrie 1979
Softcover reprint of the hardcover 1st edition 1979
All rights reserved. No part of this publication may be reproduced
or transmitted, in any form or by any means, without permission.
First published in the United States of America 1979 by Enslow Publishers
First published in Great Britain 1979 by
THE MACMILLAN PRESS LTD
London and Basingstoke
Associated companies in Delhi Dublin
Hong Kong johannesburg Lagos Melbourne
New York Singapore and Tokyo
ISBN 978-1-349-04701-7 ISBN 978-1-349-04699-7 (eBook)
DOI 10.1007/978-1-349-04699-7
This book is sold subject to the standard conditions of the
Net Book Agreement.
CONTENTS
PREFACE 7
LIST OF ILLUSTRATIONS 9
PROLOGUE: The Forgotten Ice Age 11
PART 1: ICE AGE DISCOVERED
I: Louis Agassiz and the Glacial Theory 19
2: The Triumph of the Glacial Theory 33
3: Exploring the Ice-Age World 47
PART II: EXPLAINING THE ICE AGES
4: The Ice-Age Problem 61
5: Birth of the Astronomical Theory 69
6: The Astronomical Theory of James Croll 77
7: Debate Over Croll's Theory 89
8: Through Distant Worlds and Times 97
9: The Milankovitch Controversy 113
10: The Deep and the Past 123
II: Pleistocene Temperatures 135
12: Milankovitch Revival 141
13: Signal from the Earth 147
14: Pulsebeat of Climate 153
15: Pacemaker of the Ice Ages 161
PART III: ICE AGES OF THE FUTURE
16: The Coming Ice Age 177
EPILOGUE: The Last Billion Years of Climate 189
APPENDIX: Chronology of Discovery 195
SUGGESTED READING 203
BIBLIOGRAPHY 205
INDEX 215
PREFACE
Knowledge that the world once endured an ice age has been
widespread for more than a century. Indeed, the concept is now
so familiar that nearly every winter storm prompts dramatic
headlines: Is a new ice age upon us?
This book tells the story of the ice ages-what they were like,
why they occurred, and when the next one is due. It is a tale of
scientific discovery, and therefore a book about people-about
the astronomers, geochemists, geologists, paleontologists, and
geophysicists from a dozen countries who have been engaged for
nearly a century and a half in the search for a solution to the
ice-age mystery.
We are indebted to many people for their advice and assistance
in the preparation of this book. In particular we wish to thank
Vasko Milankovitch for sharing with us his memories of his
father, Milutin Milankovitch. Tatomir P. Angelitch of the Serbian
Academy of Sciences and Arts was kind enough to provide us with
a complete list of Milankovitch's publications. Barbara Gronquist
translated many passages from the German. Gordon Craig of the
University of Edinburgh helped locate information about james
Croll. The studies by Albert V. Carozzi of the University of
Illinois were an invaluable guide to the early development of the
glacial theory. Catherine Krause located obscure sources that
contributed greatly to this book.
Many people put their personal recollections at our disposal.
Among them were William A. Berggren, Wallace S. Broecker,
Rose Marie Cline, Cesare Emiliani, Samuel Epstein, David B.
Ericson, Rhodes W. Fairbridge, James D. Hays, George J. Kukla,
Robley K. Matthews, Neil D. Opdyke, Nicholas J. Shackleton, and
Manik Talwani.
Rosalind M. Mellor prepared the typescript and kept an eagle
eye out for inconsistencies. Terry A. Peters also helped in this
preparation. Barbara Z. Imbrie gave the manuscript its first criti
cal reading and made many helpful suggestions.
7
The Museum of Science in Boston was kind enough to grant
one of us (K.P.I.) a leave of absence so that this book might be
written.
Finally, we wish to express our gratitude to our editor, Ridley
Enslow, for his encouragement and advice. In large part, his
enthusiasm and interest have made this book a reality.
Seekonk, Massachusetts J.l.
june, 1978 K.P.I.
LIST OF ILLUSTRATIONS
1. Earth today and during the last ice age. 12, 13
2. Glacial deposit on Cape Ann, Massachusetts. 15
3. Scratched stone from a glacial deposit in Europe. 20
4. Zermatt glacier in the Swiss Alps. 23
5. Portrait of Louis Agassiz at the Unteraar Glacier. 27
6. Polished bedrock near Neuchatel, Switzerland. 29
7. Erratic boulder in Scotland. 38
8. The Reverend Professor Buckland, equipped
as a "glacialist." 42
9. Antarctic Ice Sheet. 44
10. Chamberlin's map of North America
during the ice age. 50
11. Shorelines of ancient Lake Bonneville, Utah. 56
12. Multiple tills in Scotland. 57
13. March of the seasons. 69
14. Dates of equinox and solstice. 70
15. Precession of the earth. 73
16. Precession of the equinoxes. 74
17. Ellipses with different eccentricities. 82
18. Orbital eccentricities calculated by James Croll. 82
19. Croll's theory of the ice ages. 84
20. Photograph of James Croll. 87
21. Succession of fossiliferous strata
according to Charles Lyell. 90
22. Lyell's classification of earth history. 91
23. Modern classification of the Cenozoic Era. 92
24. Milankovitch radiation curve for latitude
65° North. 105
25. Effect of axial tilt on the distribution of sunlight. 107
26. Milankovitch radiation curves for
different latitudes. 108
27. Milutin Milankovitch. 110
28. Theoretical succession of North American
ICe ages. 115
9
10 Ice Ages: Solving the Mystery
29. Theoretical succession of European ice ages. 116
30. Eberl's test of the Milankovitch theory. 118
31. Fluctuations of the ice-sheet margin
between Indiana and Quebec. 122
32. Fossil from the deep-sea floor. 130
33. Succession of Caribbean ice ages
according to Ericson and Emiliani. 132
34. Reef terraces on New Guinea. 145
35. Astronomical theory of Barbados sea levels. 146
36. Magnetic history of the earth. 150
37. Climatic history recorded in a
Czechoslovakian brickyard. 155
38. The 100,000-year pulse of climate. 157
39. The "Rosetta Stone" of late Pleistocene climate. 165
40. Climate of the past half-million years. 169
41. Changes in eccentricity, tilt, and precession. 170
42. Spectrum of climatic variation over the past
half-million years. 171
43. Climate of the pastyears. 179
44. Climate of the past 1 00 years. 180
45. Climate of the past 1 ,000 years. 181
46. The Argentiere glacier today and in 1850. 182
47. Climatic forecast to the year A.D. 2100. 185
48. Climatic forecast of the next 25,000 years. 186
49. The last billion years of climate. 190
PROLOGUE
The Forgotten
Ice Age
Twenty-thousand years ago, the earth was held in thrall by re
lentlessly probing fingers of ice-ice that drew its power from
frigid strongholds in the north, and flowed southward to bury
forests, fields, and mountains. Landscapes that were violated by
the slowly moving glaciers would carry the scars of this advance
far into the future. Temperatures plummeted, and land surfaces
in many parts of the world were depressed by the unrelenting
weight of the thrusting ice. At the same time, so much water was
drawn from the ocean to form these gargantuan glaciers that sea
levels around the world fell by 350 feet, and large areas of the
continental shelf became dry land.
This period in the earth's history has come to be called the ice
age. In North America, glacial ice spread out from centers near
Hudson Bay to bury all of eastern Canada, New England, and
much of the Midwest under a sheet of ice that averaged more than
a mile in thickness. A second ice sheet spread out from centers in
the Canadian Rockies and other highlands in western North
America to engulf parts of Alaska, all of western Canada, and
portions of Washington, Idaho, and Montana. In Europe, the ice
reached outward from Scandinavia and Scotland to cover most of
Great Britain, Denmark, and large parts of northern Germany,
Poland, and the Soviet Union. A smaller ice cap, centered on the
Alps, buried all of Switzerland and nearby portions of Austria,
Italy, France, and Germany. In the southern hemisphere, small
ice sheets developed over parts of Australia, New Zealand, and
Argentina. In all, the ice covered about 11 million square miles of
land that is today free of ice.
Immediately south of these great northern-hemisphere ice
sheets, the landscape was treeless tundra. Here, during the short,
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