National Geographic : 1898 Oct
LAKE CHELAN glacier and a certain type of river. In the arid regions of the West the streams which have their sources in the mountains flow down into the valleys and disappear, being absorbed by the dry soil and the thirsty atmosphere. These streams, like glaciers, bear detritus down from the mountains, and upon their disap pearance in the valley they drop this detritus as the glacier does. There are, therefore, certain characteristics by which the gorge produced by glacial erosion may be distinguished from that pro duced by aqueous erosion. The glacial gorge has the shape of CASCADE PASS AND AMPHITHEATER the capital letter U, while the waterworn gorge is a V-shaped notch. In a glacial gorge the spurs separating the tributaries have their ends blunted or planed off, while in a waterworn gorge they are sharp and angular. In a glacial gorge the tribu taries enter the valley above its level, while in a waterworn gorge they commonly grade down to its level. A glacial gorge has an amphitheater at its head; a waterworn gorge has not. A glacial gorge is commonly lined near its lower end with lateral moraines and across its foot stretches a terminal moraine, and often this terminal moraine has formed a lake.