Louis Agassiz: Encyclopedia II - Louis Agassiz - Proposal of an ice age

Louis Agassiz - Proposal of an ice age

In 1837 Agassiz was the first to scientifically propose that the Earth had been subject to a past ice age. Prior to this de Saussure, Venetz, Jean de Charpentier and others had made the glaciers of the Alps the subjects of special study, and Charpentier had even arrived at the conclusion that the erratic blocks of alpine rocks scattered over the slopes and summits of the Jura mountains had been moved there by glaciers. The question having attracted the attention of Agassiz, he not only made successive journeys to the alpine regions in company with Charpentier, but he had a hut constructed upon one of the Aar glaciers, which for a time he made his home, in order to investigate the structure and movements of the ice. These labours resulted, in 1840, in the publication of his work in two volumes entitled Etudes sur les glaciers ("Study on Glaciers"). In it he discussed the movements of the glaciers, their moraines, their influence in grooving and rounding the rocks over which they travelled, and in producing the striations and roches moutonnees seen in Alpine-style landscapes. He not only accepted Charpentier's idea that some of the alpine glaciers had extended across the wide plains and valleys drained by the Aar and the Rhône, but he went still farther. He concluded that, in the relatively recent past, Switzerland had been another Greenland; that instead of a few glaciers stretching across the areas referred to, one vast sheet of ice, originating in the higher Alps, had extended over the entire valley of northwestern Switzerland until it reached the southern slopes of the Jura, which, though they checked and deflected its further extension, did not prevent the ice from reaching in many places the summit of the range. The publication of this work gave a fresh impetus to the study of glacial phenomena in all parts of the world.

Thus familiarized with the phenomena associated with the movements of recent glaciers, Agassiz was prepared for a discovery which he made in 1840, in conjunction with William Buckland. The two visited the mountains of Scotland together, and found in different locations clear evidence of ancient glacial action. The discovery was announced to the Geological Society of London in successive communications. The mountainous districts of England, Wales, and Ireland were also considered to constitute centres for the dispersion of glacial debris; and Agassiz remarked "that great sheets of ice, resembling those now existing in Greenland, once covered all the countries in which unstratified gravel (boulder drift) is found; that this gravel was in general produced by the trituration of the sheets of ice upon the subjacent surface, etc."

Adapted from the Wikipedia article "Proposal of an ice age", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki