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 . heterminus of the glacier, and in the Haenke and Marvineglaciers to their very end. In Variegated and Atrevida glaciers the ice has beenbroken for a distance of five to seven miles: in Marvineglacier the breaking extends fully fifteen miles. The crevassingin all cases extends completely across the valley portion ofthe glacier and down into the stagnant,
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 . heterminus of the glacier, and in the Haenke and Marvineglaciers to their very end. In Variegated and Atrevida glaciers the ice has beenbroken for a distance of five to seven miles: in Marvineglacier the breaking extends fully fifteen miles. The crevassingin all cases extends completely across the valley portion ofthe glacier and down into the stagnant, or nearly stagnant,moraine-covered margin. In all cases, too, the thrust isaccompanied by a forward movement of the margin; and inat least three cases—the Variegated, Haenke, and Atrevida—there has been a distinct thickening of the ice as a result ofthe forward thrust. . Such a remarkable changein the condition of the glaciers as to transform long-stag-nant, unbroken, moraine-covered valley glaciers into a laby-rinth of crevasses in the short interval of ten months—aphenomenon, so far as known, not elsewhere recorded—callsfor a special explanation. ?United States Geological Survey, Professional Paper 64, pp. 91-106. <k. GLACIERS ON THE PACIFIC COAST. 33 Professor Tarr attributes this remarkable advance to theeffect of the earthquake which occurred in the region in 1899,six years before. This earthquake, which was sufficient toelevate a portion of the coast forty-seven feet, he supposes tohave shaken large quantities of snow down from the moreelevated peaks upon the head of the glaciers, and that ittook all the intervening six years to make its influence feltat the margin. Thus, as the weather bureau, when the extentof the rainfall at the sources of a great river is known, canpredict when the s^vollen current will reach successive pointsalong the river valley, so the glacialist can foretell, from thesnow-fall over the 7ieve, when its influence will be felt belowthroug
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