Frozen Earth

Frozen Earth: The Once and Future Story of Ice Ages

Doug Macdougall
Copyright Date: 2004
Edition: 1
Pages: 267
https://www.jstor.org/stable/10.1525/j.ctt1ppbvp
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  • Book Info
    Frozen Earth
    Book Description:

    In this engrossing and accessible book, Doug Macdougall explores the causes and effects of ice ages that have gripped our planet throughout its history, from the earliest known glaciation-nearly three billion years ago-to the present. Following the development of scientific ideas about these dramatic events, Macdougall traces the lives of many of the brilliant and intriguing characters who have contributed to the evolving understanding of how ice ages come about. As it explains how the great Pleistocene Ice Age has shaped the earth's landscape and influenced the course of human evolution,Frozen Earthalso provides a fascinating look at how science is done, how the excitement of discovery drives scientists to explore and investigate, and how timing and chance play a part in the acceptance of new scientific ideas. Macdougall describes the awesome power of cataclysmic floods that marked the melting of the glaciers of the Pleistocene Ice Age. He probes the chilling evidence for "Snowball Earth," an episode far back in the earth's past that may have seen our planet encased in ice from pole to pole. He discusses the accumulating evidence from deep-sea sediment cores, as well as ice cores from Greenland and the Antarctic, that suggests fast-changing ice age climates may have directly impacted the evolution of our species and the course of human migration and civilization.Frozen Earthalso chronicles how the concept of the ice age has gripped the imagination of scientists for almost two centuries. It offers an absorbing consideration of how current studies of Pleistocene climate may help us understand earth's future climate changes, including the question of when the next glacial interval will occur.

    eISBN: 978-0-520-93980-6
    Subjects: Geology

Table of Contents

  1. Front Matter
    (pp. i-vi)
  2. Table of Contents
    (pp. vii-viii)
  3. List of Illustrations
    (pp. ix-x)
  4. Acknowledgments
    (pp. xi-xii)
  5. CHAPTER ONE Ice, Ice Ages, and Our Planet’s Climate History
    (pp. 1-14)

    The American author and historical popularizer Will Durant once wrote, “Civilization exists by geological consent, subject to change without notice.” That is not a new idea, even if Durant phrased it especially well, but nowadays many historians scoff at the notion of environmental determinism, the possibility that climate or geology may have seriously affected the course of human history. And yet there are still many places on this planet where Durant’s observation rings true, especially places with extremes of climate. One such is the arctic regions, particularly Greenland. Ninety-five percent of that island country is covered by ice. Towns and...

  6. CHAPTER TWO Fire, Water, and God
    (pp. 15-24)

    Louis Agassiz’s theory of a global ice age overturned the conventional wisdom about the Earth’s past. It also bruised a few egos, especially those of scientists who had built their reputations on quite different versions of the planet’s history (in this respect, at least, scientific disputes seem not to have changed much over the intervening century and two-thirds). They did not appreciate this brash young newcomer—a zoologist at that—with his revolutionary ideas. Agassiz himself had anticipated opposition to his theory, but he was taken aback at the virulence of some of the critics. He saw the geological evidence...

  7. CHAPTER THREE Glaciers and Fossil Fish
    (pp. 25-44)

    Louis Agassiz grew up in Switzerland, in a village that was almost surrounded by water—two lakes and a river flanked his little town. From the time he was a small boy, he loved to go fishing. Local fishermen would take the parson’s son out in their boats and teach him their secrets. They liked this precocious lad, and they soon realized that he was a quick study. Although none of them knew it at the time, fish were to be an important part of Agassiz’s later life. So too were the glaciers of the Alps, looming on the horizon...

  8. CHAPTER FOUR The Evidence
    (pp. 45-64)

    What, exactly, are the clues that betray the presence of extensive continental ice sheets in our planet’s recent past? Some have already been described in previous chapters, and if you live north of about 40 degrees latitude in North America, or a bit further north than that in Europe, or in a mountainous region almost anywhere, you have probably seen some of the effects of glaciers for yourself—although you may not have realized it. Today many more features are recognized as having originated in the glacial-interglacial cycles of the Pleistocene Ice Age than was the case in Agassiz’s day—...

  9. CHAPTER FIVE Searching for the Cause of Ice Ages
    (pp. 65-88)

    Curiously enough, there is no evidence that Louis Agassiz ever spent much time thinking about what caused the ice age that he proposed. He seems to have been much more interested in effects than in causes. The fact that there was no easily grasped mechanism to explain the Earth’s sudden descent into frigidity was undoubtedly one of the reasons the ice age theory was resisted for so long, despite the field evidence. Agassiz was content to amass the various clues that supported his conclusions about widespread glaciation and to fit the theory neatly into his own thinking about the history...

  10. CHAPTER SIX Defrosting Earth
    (pp. 89-114)

    Joseph Adhémar’s apocalyptic vision of a melting polar ice cap, a shifting center of gravity for the Earth, and devastating floods as ocean water rushed from one hemisphere to another is far from an accurate picture of what happens at the end of a glacial period. But at their maximum, the ice caps did hold huge volumes of water, and accumulating evidence shows that therewereglacial floods as they melted, some of them catastrophic. In fact, some were so catastrophic that when the claim was first made that flowing water had produced the devastation they left in their wake,...

  11. CHAPTER SEVEN The Ice Age Cycles
    (pp. 115-140)

    Just a few years before Bretz published his first paper on the Scablands, a book appeared in Europe that was to have a lasting impact on thinking about the Pleistocene Ice Age. It was written by a Serbian mathematician who, in all probability, had never seen a moraine or an erratic boulder. But he was a gifted theorist who was ambitious and eager to take on large, unsolved problems in the sciences. The mathematician was Milutin Milankovitch, and he eventually settled on climate as a field that seemed ripe for the application of mathematical principles. Today, you will find his...

  12. CHAPTER EIGHT Our Planet’s Icy Past
    (pp. 141-163)

    Oxygen isotopes in deep-sea cores, together with a few other indicators of past climates, have given us a surprisingly clear picture of the coming and going of glaciers during the Pleistocene Ice Age. But the current ice age occupies only the past few million years, an almost insignificant slice of our planet’s four-and-a-half-billion-year history. What was the climate like for the rest of that vast sweep of time? The “norm,” if it is possible to speak of such a thing, was one of warmth and little or no permanent ice. However, there is good evidence that our small (by the...

  13. CHAPTER NINE Coring for the Details
    (pp. 164-186)

    The physical and chemical records of ancient ice ages stored in rocks—scratched and faceted boulders, glacial drift deposits hardened into coherent tillite, carbon isotopes, and various other signatures—allow us to trace glaciation back through almost three-quarters of our planet’s history. However, we know almost nothing about the finer details of the frigid intervals that occurred before the Pleistocene Ice Age—what the actual temperatures were, whether there were repeated 100,000-year cycles of glaciation and deglaciation paced by the Earth’s orbit, or how the climate varied across the globe. But over the past few decades, scientists have accumulated an...

  14. CHAPTER TEN Ice Ages, Climate, and Evolution
    (pp. 187-211)

    Weather is always a topic of conversation, and even today’s city dwellers, quite insulated from the natural world, tune in to the Weather Channel to learn the latest about weather in their region or across the globe. Climate is simply average weather on a long timescale. Thornton Wilder’s playThe Skin of Our Teethdeliberately mixes geological periods—modern Americans, dinosaurs, and an ice age exist simultaneously—and weather, as often in literature, is a metaphor for crisis and conflict. Some anthropologists and biologists think that in real life, it is much more than a metaphor: that climate—especially the...

  15. CHAPTER ELEVEN The Last Millennium
    (pp. 212-231)

    We are now about twenty thousand years past the peak of the most recent glacial advance of the Pleistocene Ice Age and are in the midst of the maximum warmth of an interglacial period. Record high temperatures have been the norm in recent years; newspapers report the melting of permafrost in Alaska and the possibility of an ice-free Arctic Ocean at the North Pole. And yet in the winter of 2000–2001, Scots were delighted when a spell of very cold weather allowed them to hold curling tournaments on lakes that had not been frozen for decades. In 2003, there...

  16. CHAPTER TWELVE Ice Ages and the Future
    (pp. 232-244)

    It is worth reiterating here something that was pointed out in the first chapter of this book but may have drifted into the background since: the Earth is still in an ice age. We are in a warm period, one of the many interglacial intervals that have occurred throughout the Pleistocene Ice Age, but even so, there are significant amounts of permanent ice in polar regions. It is easy to forget that this may be just a short respite before another glacial interval begins. Or perhaps the respite may be longer than we anticipate. Man’s activities may intervene and confound...

  17. SUGGESTIONS FOR FURTHER READING
    (pp. 245-248)
  18. INDEX
    (pp. 249-256)
  19. Back Matter
    (pp. 257-257)