. Contributions to the geography of the United States, 1923-1924. Geology; Mines and mineral resources. 48 CONTRlBiaTIOis^S TO GEOGRAPHY OF Ui^ITED STATES, 1923-1924. especially along the margin toward the axis of the valley, the knolled and pitted configuration characteristic of moraines. The altitudes of such terraces on opposite sides of a valley do not usually cor- respond, as in lake or stream terraces, where the deposit is controlled by a common water level, and there may be variation in the gradients on the two sides, such as in lake or stream terraces might be taken as evidence of subs
. Contributions to the geography of the United States, 1923-1924. Geology; Mines and mineral resources. 48 CONTRlBiaTIOis^S TO GEOGRAPHY OF Ui^ITED STATES, 1923-1924. especially along the margin toward the axis of the valley, the knolled and pitted configuration characteristic of moraines. The altitudes of such terraces on opposite sides of a valley do not usually cor- respond, as in lake or stream terraces, where the deposit is controlled by a common water level, and there may be variation in the gradients on the two sides, such as in lake or stream terraces might be taken as evidence of subsequent deformation. After the ice had melted off the uplands for some miles to the north lobes of the glacier still remained in the valleys. The waters from the melting ice flowed down the slopes and ravines and washed more or less drift onto the margins of the valley lobes, where they lay against the rock slope (fig. Y, A). The waters thus gathered into considerable streams along this contact—^here flowing over a bed of ice, there swinging against the valley slope—spreading out the. FiGDEE! 7.—Diagram illustrating formation of kame terraces. A, Terrace formed at the side of a melting glacial lobe in a valley; B, view up the valley after melting of ice has caused slumping of overlying material and formation of " ice-contact" slopes below the terraces. sands and gravels and forming deposits a quarter of a mile to half a mile or more in width. At the south end of each ice lobe the stream deposits merge into the moraine, filling the valley from side to side. " Here the melting ice left the drift piled in irregular knolls and ridges, except as spread out smoothly by the glacial waters. The sheet of debris lapped over the margin of the melting- lobe, filling in crevasses and burying many ice blocks left detached by the melting. Through the sj)aces between the piles of drift and over the buried ice blocks the water escaped down the valley. Chan- nels were cut, an
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