File:Forest physiography; physiography of the United States and principles of soils in relation to forestry (1911) (14590364267).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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us spur of the Rockies jutting far out beyond their border. The Bighorn Mountains are a great anticline lifted many thousandsof feet and composed of a thick series of sedimentary rocks (Paleozoicand Mesozoic) and a central core of granite and schist (pre-Cambrian).^The sedimentary rocks arch over the northern and southern portionsof the uplift, and give rise to elevated plateaus about 9000 feet highat the north and 8000 feet high at the south. On the divides theseplateaus often present broad tabular surfaces though they are trenchedby numerous large canyons. The central plateau terminates in highcliffs at certain places in the border region, but in others and especially 1 S. F. Emmons, Geol. Expl. of the 40th Par. (King Surveys), vol. 2, 1877, pp. i94-ig5. 2 N. H. Darton, Geology of the Bighorn Mountains, Prof. Paper U. S. Geo!. Surv. No. 51,1906, pp. lO-II. 5 Darton and Salisbury, Cloud Peak-Fort McKinney Foho U. S. Geol. Surv. No. 142, 1906,p. I, cols. 2, 3. 35° FOREST PHYSIOGRAPHY
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ROCKY MOUNTAINS. II 351 along the eastern side of the mountains it is flanked by a distinct ridgeof limestone that rises slightly above an inner valley and slopes steeplytoward the plains. These plateaus are covered by forests with manypark-like openings and are extensively used as grazing grounds for cattleand sheep during the short summer season. The subordinate topographic features of the Bighorns depend uponlocal flexures on the flanks of the main uplift and a number of faults,the latter being especially marked northwest of Buffalo and on theeastern border of the range, where one of the faults has a throwof about 9000 feet. The effect of the sharper flexing and of the pro-nounced faulting has been to increase the development of precipitousslopes, and to cause a greater development of hogback topographyespecially on the eastern side. The hogback ridges rise from 100 to200 feet above the adjoining valleys, and are due to the outcrop of sand-stone of moderate hardness, while the vall

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