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Ice Ages: Solving the Mystery PDF

206 Pages·1979·18.455 MB·English
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liCJE 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, 11

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