Identifier: bulletinofgeolo341923geol (find matches)
Title: Bulletin of the Geological Society of America
Year: 1890 (1890s)
Authors: Geological Society of America
Subjects: Geology
Publisher: (New York : The Society)
Contributing Library: Smithsonian Institution Libraries
Digitizing Sponsor: Biodiversity Heritage Library

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e glaciation 580 General statement i 580 Spokane River and Palouse River drainage 581 Vicinity of Spokane 581 Vicinity of Spangle 583 Vicinity of Cheney , 585 Vicinity of Lamont 586 Vicinity of Kahlotus 587 Vicinity of Sprague 587 Crab Creek drainage 588 General statement 588 Grand Coulee 591 Hartline structural valley 593 Quincy Valley or Basin 594 Moses Coulee ., 600 The Wisconsin glaciation , 602 Discussion 608 Introduction Only the northern part of the Columbia Plateau is concerned in thisstudy and only waters from the Cordilleran ice-sheet. Two glacialepochs are involved—one the Wisconsin, the other as yet undated. Be-sides contributing to the geological history of the region, this articleendeavors to show that glacier-born streams, under proper conditions,are erosive agents of great vigor over large tracts far from the front ofthe melting ice. ^ Manuscript received by tlie Secretary of the Society January 10, 1923. (573) )~4: J. n. BRETZ GLACIAL DRAI^•AGE OX COLUMBIA PLATEAU
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^f -m i^ vgvV- topographic features oio Topography axd Draixage The Columbia Ijasalt plateau is separated from several mountainranges on the north and from the Cascade Eange on the west by thetrench in which flows Columbia Eiver. On the east, the plateau abutsao-ainst and interflnoers with the Coeur dAlene Mountains of Idaho.When the Miocene basalt flows of this region ceased, the lava plainabutted in a similar fashion against the mountains on the north andwest. The cutting of the Columbia Valley between mountains and plainin the great arc known as the Big Bend has partially isolated thisportion of tl;ie former lava plain and thus given it the character of aplateau. The Columbia Valley north of the plateau is a great canyon.1,500 to 2,000 feet deep, its bottom less than 1,000 feet above the sea.It does not, however, serve for the complete northern boundary of theplateau. Spokane Eiver, its tributary from the Coeur dAlene Mountainson the east, may be considered as marking the northern

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