Glaciation of the Puget Sound Region

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...Sound Glacier crossed the Des Chutes River valley where it emerged from the Huckleberry Mountains. The upper part of the Des Chutes Valley was protected by the Huckleberry Mountains against invasion of ice from Mount Rainier, and it was dammed by Puget Sound ice at its debouchure on the plain. This gave rise to a glacial lake. The pebbly clay deposited in this lake probably is responsible for the flat on which is the group of small farms and the Bald Hill School, a mile or two above the moraine crossing. The lake deposits and the moraine have been responsible for the superposition of the river on a rock spur of its pre-Vashon valley, and the consequent formation of the Des Chutes Falls, a beautiful double cataract with a picturesque canyon below it. (Plate X, Fig. An interesting problem is afforded by a comparison between the Nisqually and Des Chutes rivers where they enter the Puget Sound drift plain. Both were diverted after the glaciation, and forced to cut through rock for a short distance. Both possess deep post-glacial canyons, but the Des Chutes has a cataract at the head of its canyon while the grade of the Nisqually rises gradually through the canyon until it is at the level of the pre-Vashon valley. The rock is a fairly uniform dense lava in the Nisqually canyon, and a volcanic agglomerate in the Des Chutes canyon. Both are cut by dikes of more resistant rock which project on the canyon slopes. The Des Chutes carries over its fall debris secured by the erosion of the rock in the upper part of its valley while the Nisqually carries outwash gravel from the present Nisqually Glacier on Mount Rainier. The reason why one stream possesses a fall in its postglacial gorge while the other does not may be found in this difference of amount of debris carried...