Forest physiography; physiography of the United States and principles of soils in relation to forestry . Fig. ij$. — Wall at head of cirque, upper end of a tributary of West Tensleep Creek, Bighorn View from above rim, showing old rounded surface. B. View from below rim, showing granitewalls nearly looo feet high. (Blackwelder, U. S. Geol. Surv.)352 ROCKY MOUNTAINS. II 353 During both the advance and the retreat of the ice the number ofseparate glaciers was greater than during the time of maximum glacia-tion, for the ice was melted out of the lower glacial troughs, while itstill l
Forest physiography; physiography of the United States and principles of soils in relation to forestry . Fig. ij$. — Wall at head of cirque, upper end of a tributary of West Tensleep Creek, Bighorn View from above rim, showing old rounded surface. B. View from below rim, showing granitewalls nearly looo feet high. (Blackwelder, U. S. Geol. Surv.)352 ROCKY MOUNTAINS. II 353 During both the advance and the retreat of the ice the number ofseparate glaciers was greater than during the time of maximum glacia-tion, for the ice was melted out of the lower glacial troughs, while itstill lingered in the separate tributary valleys. The glaciers on the. ^/7,Jm°oo) Fig. IK: - Glacier systems of the Bighorns at the time of their maximum development,welder, U. S. Geol. Surv.) (After Black- west side covered almost twice as great an area as those on the east andthey were also somewhat longer, a difference due to the heavier precipi-tation on the west side (prevailing westerly winds) and the wider catch-ment basins. The surviving glaciers are now found wholly on the eastside, a condition probably due to the better protection of the cirques 354 FOREST PHYSIOGRAPHY on that side from the sun and in part to the westerly winds whichdrift snow over the crest of the range and into the cirques and alcoveson the lower side. The lower limits of the glaciers were from 6500 feetto 10,500 feet, the necessary elevation for the generation of glaciers inthe Bighorn Mountains during the last glacial epoch ranging from 9500to 11,500 feet.^ Glacial cirques and hanging valleys are of frequent occurrence, thougharetes and needles are absent because glacial s
Size: 1327px × 1884px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectforestsandforestry
