Nature Notes

Vol. IX November, 1931 No. 11

Emmons Glacier Receeds

The Emmons Glacier, largest glacier on Mount Rainier and largest glacier in continental United States, receeded - from September 15, 1930 to October 10, 1931 - a total of 142 feet. This is the first recessional study made on this glacier though similar measurements have been kept on the Nisqually Glacier since 1918. (See October Nature Notes)

As in the case of most glaciers on "The Mountain" absolute recessional measurements are impossible to obtain due to conditions which are encountered at the snout. It has been customary to consider the point at which the stream emerges from the ice as the actual terminus though in most cases the ice partially encloses that point in a sort of semicircle. That is particularly true of the Emmons whose huge terminal moraine is almost entirely underlaid with ice and which, because of its being protected by the mantle of rock which forms this moraine, melts very slowly. Another theory which may be advanced concerning its rapid recession is that it possibly moves downward rather fast, the top portion of the ice moving faster than the ice in contact with the glacial bed due to reduced friction. This causes the formation of a large overhanging "lip" which break off in great chunks. This feature reduces the glacier much more rapidly than ordinary melting. A large overhanging "lip" and large, rapidly melting chunks along the stream, gave evidence of this fact.

Regular annual recessional measurements of this glacier will be made hereafter. Points have also been established for such studies near the snouts of the Carbon and South Tahoma Glaciers.


sketch of Emmons Glacier on Mount Rainier

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