File:Forest physiography; physiography of the United States and principles of soils in relation to forestry (1911) (14774483914).jpg

Identifier: forestphysiograp01bowm (find matches)
Title: Forest physiography; physiography of the United States and principles of soils in relation to forestry
Year: 1911 (1910s)
Authors: Bowman, Isaiah, 1878-1950
Subjects: Physical geography Forests and forestry Soils
Publisher: New York, J. Wiley & sons (etc., etc.)
Contributing Library: The Library of Congress
Digitizing Sponsor: The Library of Congress

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sheets. An examination of the valley systems in plan shows a remarkabledegree of headward cutting on the part of the glacier ice. The amphi-theatral valley heads or alcoves on opposite sides of a divide have inmany instances cut back to the point where a knife-like ridge has beenformed, as south of Gould Mountain and on the continental divide twomiles south of Chaney glacier. The process has resulted in the for-mation of pyramidal mountains such as Going-to-the-Sun Mountain,Cataract Mountain, Little Chief Mountain, Heavens Peak, and others,or in the formation of skeleton mountains of irregular outline such asAlmost-a-dog Mountain, Appekunny Mountain, and Merritt Mountain. The manner in which such headward cutting has taken place has beenwell set forth by Johnson,^ who has observed that in glaciated mountainsthe great curving bergschrund of the snow-field penetrates to the foot 1 D. W. Johnson, The Profile of Maturity in Alpine Glacial Erosion, Jour. Geo!., vol. 12, 1904, pp. 569-578.
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Fig. 95. — Mount Gould, Lewis Range, Montana, looking southwest from South Fork of Swift Current. See Fig. 86 forlocation. Characteristic cliff of limestone overlooking argillite. The dark band is intrusive diorite. The valley head isa glacial amphitheater developed along joint planes. It is 4670 feet from lake to summit. (Willis.) 313 314 FOREST PHYSIOGRAPHY of the precipitous rock slope constituting the wall of the amphitheaterenclosing the snow-filled cirque. He concludes that a causal rela-tion determines the coincidence in the position of the bergschrund andthe foot of the cliff wall. The opening allows air to come irito contactwith both ice and rock at the bottom of the crevasse. By day there isthawing, by night freezing, and blocks of rock are wedged off and thecirque wall riven. The bottom of the crevasse is therefore a narrowzone of relatively vigorous frost-weathering. The result is a sappingof the foot of the cirque wall and its gradual steepening and retreat. The continu

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