198 Adventures in Scenery 



altitudes. Trunk glaciers ploughed down the deep canyons 

 beyond the lowest limits of the general ice field. In the region 

 of Yosemite Park the ice field extended down the slope to pres- 

 ent altitudes of a little less than 5,000 feet. The trunk glaciers 

 extended to lower levels but did not reach to the foot of the 

 Sierra slope. 



The Tuolumne glacier attained a length of 60 miles, and 

 extended a dozen miles beyond the margin of the general ice 

 field. It terminated, however, 30 miles above the foot of the 

 range slope. The Yosemite glacier reached a length of 37 miles, 

 and extended 7 miles beyond the margin of the ice mantle. Its 

 lower end was in the Merced canyon below El Portal, about 50 

 miles from the foot of the range. The San Joaquin glacier was 

 more than 50 miles in length, but it pushed only a few miles 

 beyond the margin of the ice mantle and ceased 45 miles above 

 the mouth of the canyon through which it flowed. Kings gla- 

 cier was 44 miles in length (along the middle branch) and came 

 to an end 37 miles above the base of the range. 



The ice movement of the trunk glaciers farther down the 

 Sierra slope than the general ice mantle was natural. The 

 canyons offered easier highways for the passage of the ice. The 

 canyons were wide and deep. The depth of the ice in the great 

 canyons was 3,000 to 4,000 feet. Movement or flow of the ice 

 in canyons was less hindered by friction than when spread out 

 over broad rock surfaces. The movement of the ice was more 

 rapid, probably several feet in a day. The high canyon walls 

 protected the ice from the melting effects of the sun. Thus the 

 trunk glaciers offered easier escape for the great body of ice 

 which pushed down from the uplands. 



Work Done by Moving Ice 



The work done by the ice in giving the Yosemite landscape 

 its present form was unmistakably very great. That glacial ice 

 has been an important agent in giving the Yosemite region its 

 present character there can hardly be serious question. The 



