Free Frozen Earth: The Once and Future Story of Ice Ages by Doug Macdougall Page A

been discussed up to the present time.
    And in this respect he was right.His theory was not a flight of fancy; it was carefully based on detailed field observations.Some of the observations he discussed drew on the work of de Charpentier and Venetz,but many were his own.The observational skills he had learned from Cuvier in Paris served him just as well in glaciological as in fossil studies.“Fortunately, in scientific problems, numerical majorities never settled any issue at first glance,” Agassiz told the skeptical delegates, confident of his ability to win over critics in the long run.
    Three years after his lecture at the Neuchâtel meeting, in 1840, Agassiz published his carefully compiled evidence for widespread past glaciation in a large volume written in French and titled Études sur les glaciers —translated as Studies on Glaciers. It was the formal presentation of the ice age theory to the world, and it is a remarkable book, truly a tour de force.Although he never considered studies of glaciers to be his primary scientific focus, in practice, Agassiz devoted a great deal of his time to this work, spending the better part of each summer in the Alps doing glaciological fieldwork.In his book, in engaging language, Agassiz described in great detail the observations that he and his colleagues had recorded during those summer field seasons: the temperatures, the nature of the crevasses, the morphology of moraines, the details of the grooves and scratches on the underlying rock, and much more.He included beautiful, if somewhat unnatural-looking, sketches of many of the glaciers they studied, often with tiny people—walkers, women in peasant dress, picnickers—or farm animals drawn in.After cataloging the field observations, and noting how similar features occur far from the present-day glaciers, Agassiz, in a few short sentences, laid out his revolutionary conclusion:
In my opinion, the only way to account for all these facts and relate them to known geological phenomena is to assume that . . . the Earth was covered by a huge ice sheet that buried the Siberian mammoths and reached just as far south as did the phenomenon of erratic boulders. . . . It extended beyond the shorelines of the Mediterranean and of the Atlantic Ocean, and even completely covered North America and Asiatic Russia.
    The frozen Siberian mammoths to which Agassiz refers in this passage had caused a great stir in Europe, and they featured significantly inthe ideas he developed about the biological effects of the ice ages.Several reports that had filtered out from arctic Siberia described these giant mammals melting out of decomposing ice, almost perfectly preserved.Hair, skin, and flesh were intact—in fact, polar bears fed on the thawing animals and local villagers hacked off meat for their dogs.To Agassiz this indicated that the ice age had begun suddenly and had been a biological catastrophe.He also mentions here erratic boulders, the same kinds of boulders that had played a major role in convincing Venetz and de Charpentier about past glaciation.Erratics had puzzled geologists for decades and, as has already been mentioned, were at the focus of the debate between those who wanted to explain most geological features as originating in the biblical Flood and those who sought more natural explanations.Some of the erratics in the Alps are huge, weighing thousands of tons, and they are unusual because they bear no resemblance to other rock types in their immediate vicinity.Their great importance in Agassiz’s theory was that they are markers of the extent of ice age glaciers.
    Agassiz dedicated his book to Venetz and de Charpentier.Still, they were slighted—Agassiz did not consult them about his ideas, and they felt that his grandiose theory misrepresented some of their ideas.No one before had postulated a truly global cold period, and no one was as enthusiastic or confident about promoting the theory as Agassiz.In addition to showing how