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 (14595725640).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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oot of Cape Blomidon,were often fifteen feet thick, and were pushed along, when thetide rose, over the sandstone ledges. He also stated that frag-ments of the black stone which fell from the summit of thecliff, a pile of which lay at its base, were often frozen into theice, and moved along with it. I then examined these fallenblocks of amygdaloid scattered around me, and observed inthem numerous geodes coated with quartz-crystals. I haveno doubt that the hardness of these gravers, firmly fixed inmasses of ice, which, although only fifteen feet thick, are of tenof considerable horizontal extent, have furnished sufficientpressure and mechanical power to groove the ledge of softsandstone.* Stones are also striated by other agencies than moving ice.Extensive avalanches and land-slides furnish conditions analo-2;ous to those of a glacier, and might in limited and favor-able localities simulate its results. In those larger geological * Travels in America, first series, vol. ii, pp. 144-146.
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•^ ^ t- SI^^S OF FORM BR GLACIATION. 129 movements, also, where the erast of the earth is broken andtlie edges of successive strata are shoved over each other, aspecies of striation is produced which in technical terms iscalled a sUcKenside. Oceasionailv this deceives the inex-perienced or incautious observer. But by due pains all tliesesemblances may be detected and eliminated from the prob-lem, leaving a sufficient number of unquestionable phenom-ena due to true glacial action. A second indubitable mark of glacial action is found inthe character of the deposit left after the retreat of the ice.Ice and water difier so much from each other in the extent oftheir fluiditv, that ordinarilv there is little dano^er of confus-ing the deposits made by them. A simple water deposit isinevitably stratified. The coarse and line material can not bedeposited by water alone, simultaneously in the same place.Along the shores of large bodies of water the deposits ofsolid material are arranged in su

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