File:The ice age in North America and its bearing upon the antiquity of man. 5th ed. with many new maps and illus., enl. and rewritten to incorporate the facts that bring it up to date, with chapters on (14782469135).jpg

Identifier: iceageinnorthame00wriguoft (find matches)
Title: The ice age in North America and its bearing upon the antiquity of man. 5th ed. with many new maps and illus., enl. and rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation
Year: 1911 (1910s)
Authors: Wright, G. Frederick (George Frederick), 1838-1921 Upham, Warren, 1850-1934
Subjects: Glacial epoch Glaciers
Publisher: Oberlin, Ohio Bibliotheca Sacra Co
Contributing Library: Gerstein - University of Toronto
Digitizing Sponsor: MSN

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of east and west glacial furrows, on Kellys Island. Till rests imme-diately on the rock, witli washed pebbles at the surface. The following very important extracts concerning glacialerosion, from the recent report of Mr. I. C. Kussell, needno introduction and no comment: That the rock-basins in the bigli Sierra were excavated byglacier.^ the writer finds no reason whatever to question. Theyfrequently occur at the lower limit of a steep slope, which ispolished and grooved, and bears every indication of havingbeen abraded by glacial action. In such cases the slope andthe direction of the furrows show that ice once descended intothe basin. On examining the opposite portion of the rim ofthe depression, glacial markings of the same character will befound. The proof is thus positive that the ice descended intothe depressions now filled with water, and emerged from themagain to continue its course. As there is no other agent knowncapable of eroding hollows in solid rock having the character
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GLACIAL EEOSIOy AND TRANSPORTATION: 269 of the basins observed in the high Sierra, it seems evident thatthe theory of the formation of rock-basins proposed by A. C.Ramsay, from evidence obtained in Scotland and Switzerland^is substantially correct, and furnishes the true explanation ofthe origin of the examples before us.* The manner in whichthe power of moving ice is directed so as to erode depressionsmay be open to discussion, but the conclusion that rock-basinsare a result of glacial action is now too strongly supported byfacts to be questioned. . . . On examining the numerous lakes more critically, one findsthat many of them occui)y de))ressions in morainal debris, orare confined by terminal moraines. In numerous instances,however, as in Bloody and Gibbs Canons, at the head of EushCreek, and all about Mount Lvell and Mount Ritter, the factthat the lakes occupy depressions in solid rock is beyond allquestion. One may walk entirely around many of them with-out stepping off rock in p

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