The ice age in North America and its bearing upon the antiquity of man5th edwith many new maps and illus., enland rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation . Pig. 149—Part of Altanta, Missouri topoeraphic sheet. Scaled Million or 1 i nterval 20 feet. Ill ustrates post-Kansan —Part of Oelweln, Iowa, toposniplilcshoet. Scale CouLoui iuloi val20 feet. Ill ustrntes erosin in the so-called lowan drift. 590 THE ICE AGE IN NORTH AMERICA. The controlling influence of the
The ice age in North America and its bearing upon the antiquity of man5th edwith many new maps and illus., enland rewritten to incorporate the facts that bring it up to date, with chapters on Lake Agassiz and the Probable cause of glaciation . Pig. 149—Part of Altanta, Missouri topoeraphic sheet. Scaled Million or 1 i nterval 20 feet. Ill ustrates post-Kansan —Part of Oelweln, Iowa, toposniplilcshoet. Scale CouLoui iuloi val20 feet. Ill ustrntes erosin in the so-called lowan drift. 590 THE ICE AGE IN NORTH AMERICA. The controlling influence of the preglacial topography maybe observed in the neighborhood of Galesburg, Illinois, whereall along the divide between the Illinois and Mississippirivers the surface presents an extensive general level, coveredwith glacial drift of lUinoisan age to a considerable as one proceeds on either side towards the rivers men-tioned the size of the preglacial valleys increases so rapidlythat the glacial blanket is not sufficient to disguise them,while near the water-shed on both sides appear the originalextensive amphitheaters characteristic of valleys of extremeage. Evidently the post-glacial erosion is not by any means sogreat as would at first appear to be the case. But what seemto be valleys of post-glacial erosion are simply adjustments ofthe glacial blanket to the preced
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Keywords: ., bookauthoruphamwarren18501934, bookcentury1900, bookdecade1910
