Geology . olorado, where their sources were at altitudes of 11,000 feetor In no part of Colorado thus far studied does there appear to havebeen a body of ice which extended beyond the limits of a single drainage system. South of the Front range of Colorado, the eastern ranges of the Rockies werethe site of numerous glaciers as far south as northern New Mexico 8 (lat. 35° 45), 1 Willis, Tacoma folio, U. S. Geol. Survey. 2 B\ackwelder and Garrey, Jour, of Geol., Vol. IX, pp. 721-724. 3 Calhoun. Jour, of Geol, Vol. IX, p. 718. 4 Blackwelder, Jour, of Geol, Vol XI, p. 216. 5 King, Geol Surv
Geology . olorado, where their sources were at altitudes of 11,000 feetor In no part of Colorado thus far studied does there appear to havebeen a body of ice which extended beyond the limits of a single drainage system. South of the Front range of Colorado, the eastern ranges of the Rockies werethe site of numerous glaciers as far south as northern New Mexico 8 (lat. 35° 45), 1 Willis, Tacoma folio, U. S. Geol. Survey. 2 B\ackwelder and Garrey, Jour, of Geol., Vol. IX, pp. 721-724. 3 Calhoun. Jour, of Geol, Vol. IX, p. 718. 4 Blackwelder, Jour, of Geol, Vol XI, p. 216. 5 King, Geol Surv. of the 40th Parallel, Vol I. 6 Leffingwell and Capps, Jour, of Geol, Vol XII, p. 698. 7 Stone, Mono. XXXVII, V. S. Geol. Surv.; also Hole and Fverley, unpublished data. 8Salisbury, Jour, of Geol, Vol. IX, 1901 THE PLEISTOCEXE OR GLACIAL PERIOD. 33f) where an altitude of nearly 12,000 feet was necessary to give origin to were also small glaciers on the northeast slope of the San Franciscomoun-. Fig. 471.—Map showing the areas of the glaciers (black areas) of the Bighorn moun-tains during the last important glacial epoch. (Blackwelder and Bastin.) tain of Arizona (nearly 13,000 feet, lat. 35° 21), the most southerly point whereglaciers are known to have existed in the United 1Atwood, Jour, of Geol., Vol. XIII, p 276. 336 GEOLOGY. In Utah, the greatesl glaciers were in the Uinta mountains, where withinan area aboul 80 miles long by 35 miles wide, there was an aggregate area ofabout 1000 square miles of glacier Near the crest of the range, only nar-row divides with sleep slopes escaped glaciation. Every considerable valleyof the range whose head had an elevation of l(),()()() feet, contained a glacier. In a few eases, (he glaciers descended below (he mountains into the open valleysOf the plateau below. rrhe lowest altitude reached by any glacier in the rangewas about (>•)()() feet, and the ice descended on the average about 1000 feet loweron the
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