Frozen Earth: The Once and Future Story of Ice Ages
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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 Earth also 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.
refrigerator. A bona fide glacier must be permanent. Generally, this implies that sufficient fresh snow must accumulate during the cold months to offset melting during the summer, although on a year-to-year basis, glaciers may expand or contract, depending on local and global climatic conditions. Today, most glaciers around the world are in retreat because of the warming climate, and it appears that the rate of melting is accelerating. This has been documented spectacularly in places such as the
the community, marriage into a good family, and a comfortable life at home in Switzerland. But it was not to be. In spite of their best efforts, Agassiz was unwavering in his determination to become a naturalist. He was not a rebel in the conventional sense, and he always had great respect and love for his parents, but he also always managed to persuade them—either himself or through influential relatives or mentors—to do things his way. One of the first instances of this characteristic that we
radioactivity had not yet been discovered, and geologists had no way to measure time accurately. The age of the Earth was unknown, although there were some wildly varying estimates based on such things as how long it would take an originally molten Earth’s crust to cool to its current temperature. But the astronomical variations could be calculated quite accurately as a function of time. If changes in climate were really tied to the changes in the Earth’s orbit, the geological effects—the glacial
Lilliputian. Bretz added the adjective “channeled” to scablands, and ever since this vast area of eastern Washington has been known as the Channeled Scablands. He described it as a roughly rectangular block, bordered on the north and west by the deep canyons of the Columbia River, and on the south by the Snake. These two rivers merge in southern Washington and flow together westward to the Pacific. The Channeled Scablands are underlain by the dense, hard rock of the Columbia River Basalts,
close to the border between Montana and Idaho and directly to the east of the Channeled Scablands. Pardee concluded that they must have been formed by the sudden release of a huge volume of water from the dammed glacial lake. He noted that it would have contained at least 1,700 cubic kilometers of water at its highest levels. Although Pardee didn’t say so explicitly, it was quite apparent that a sudden release of Lake Missoula’s water might have been the source of Bretz’s catastrophic flooding.