Page:Popular Science Monthly Volume 70.djvu/103

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THE

POPULAR SCIENCE

MONTHLY



FEBRUARY, 1907



GLACIAL EROSION IN ALASKA[1]
By Professor RALPH S. TARR
CORNELL UNIVERSITY

WHEN Henry Gannett made the statement that "thousands of cubic miles" of rock had been removed from the fiords of southeastern Alaska by glacial erosion, and that "the relief features of this region, its mountains and its gorges partly filled by the sea, are all of glacial origin,[2] it is probable that many readers had the feeling that he had greatly exaggerated the case of glacial erosion. For my own part, I distinctly remember reading this with the feeling that, although glaciers are unquestionably capable of doing great work of erosion, it would require the most convincing evidence to satisfy me of even the approximate accuracy of this statement. Having now made four trips over a part of the route upon which Mr. Gannett based his statements, and having examined the phenomena attentively, there and elsewhere, I have the conviction that in reality his statement of the case is in close harmony with the truth. It is the purpose of this paper to state the argument upon which this conclusion is based.

It is a well-known fact that it is possible to go from Seattle to Sitka, along a series of 'Channels' 'Canals' and 'Reaches' without once entering the open ocean. In addition to this unique 'Inside Passage' of upwards of 1,000 miles, there is a maze of branches of such enormous extent that the whole system of channels has not yet been charted. Everywhere these arms of the sea are enclosed between

  1. Published by permission of the Director of the U. S. Geological Survey. I am indebted to Lawrence Martin and O. von Engeln, members of my expeditions, for photographic work, as indicated under the illustrations, and to Mr. Martin and B. S. Butler for valuable assistance in my field investigations.
  2. Harriman Alaska Expedition, Vol. II., History, Geography, Resources, 1902, pp. 258-259.