Vol. XVIII, No. 6 WASHINGTON 



June, 1907 



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BIGHORN MOUNTAINS 



By N. H. Darton 

 Of the United States Geological Survey 



ONE of the least-known portions of 

 the Rocky Mountain province 

 is the high outlying range 

 known as the Bighorn Mountains. It ex- 

 tends north and south across the north- 

 ern-central portion of Wyoming, a rug- 

 ged barrier lying between the Great 

 Plains on the east and a wide valley, 

 known as Bighorn Basin, on the west. Its 

 length is about 120 miles and the width 

 varies from 30 to 50 miles. The higher 

 summits rise over 13,000 feet above sea- 

 level, or about 9,000 feet higher than the 

 adjoining plains. The mountains lie some 

 distance from the main lines of travel, 

 the nearest railroad being the Burlington, 

 which passes 20 miles east of them in the 

 vicinity of Sheridan, Wyoming. Owing 

 to their height and northern latitude, they 

 are extensively snow-covered, much of 

 the snow remaining on the higher sum- 

 mits throughout the summer. Several 

 small glaciers lie in the shadow of the 

 higher peaks. During the Glacial epoch 

 they were covered with wide-spread fields 

 of ice, of which the present glaciers are 

 shrunken remnants. To the geologist 

 these mountains present many phe- 

 nomena of great interest. To the sight- 

 seer and Alpine climber many of their 

 rugged features will prove most attract- 



ive. Game is abundant and most of the 

 streams are teeming with trout. There is 

 no hot weather, for the summers are cool 

 by day and cold by night. 



The mountains are due to a great up- 

 lift in the earth's crust, an arch whose 

 crest has been truncated by erosion, leav- 

 ing an elevated central area of old 

 granite, with high flanking ridges of 

 overlying sandstones and limestones. The 

 arch is beautifully defined by the east- 

 ward dip of the strata on the east side 

 of the range and the westward dip on 

 the west side, features which are well ex- 

 hibited in high cliffs in many of the deep 

 canyons which cross the front range. 

 The central area of granite presents con- 

 siderable variety of scenery. The lower 

 portions contain numerous parks cov- 

 ered with grass and various herbs which 

 afford exceptionally fine pasturage, and 

 during the summer season these are 

 occupied by sheep and cattle. The parks 

 are separated by numerous rocky ridges 

 of granite, and a wide area from 6,000 

 to 10,000 feet in altitude is covered with 

 forests of pine. Much of the main divide 

 rises above 10,000 feet and presents high, 

 rough mountain summits with surfaces 

 either of loose granite blocks, or steep 

 cliffs. This district culminates in Cloud 



