200 Adventures in Scenery 



verged from adjacent valleys. The materials of which moraines 

 are composed especially boulders and rock fragments of all 

 sizes show by their nature where the materials came from, 

 and hence give much assistance in determining the direction of 

 ice movement. Every glacier carries large quantities of rock 

 waste, ranging from huge boulders down to the finest mud. 

 Of this material part has fallen upon its surface from the frost- 

 riven canyon walls; part has been torn from the floor and sides 

 of the canyon by the glacier itself. As the ice melts in summer 

 some of the rock waste is released and dropped at the sides and 

 front of the glacier. If the edge of the ice remains stationary, 

 that is, if melting just about keeps pace with the forward move- 

 ment of the ice, the rock waste accumulates in the form of 

 more or less sharp-crested ridges, or moraines. The height to 

 which moraines may be piled depends upon the amount of 

 material carried by the ice and the length of time that the edge 

 of the glacier remains "stationary." In the Sierra Nevada 

 mountains moraines generally range from 10 to 30 feet in 

 height, but few reaching 60 feet. When a glacier melts back 

 the moraine loop formed during its "stationary" period is left 

 standing as a sort of monument that bears witness to the former 

 proportions of the ice mass. 



Moraines in Yosemite Valley 



In the lower half of the Yosemite Valley six frontal or ter- 

 minal moraines may be counted within the distance of 1 mile. 

 The one farthest down the valley is immediately above the 

 Bridalveil Meadow. The fifth and sixth moraines together 

 form a nearly straight dam across the valley just below the El 

 Capitan Meadow. A small gap cut by Merced River interrupts 

 the continuity of this dam and is now spanned by the El Capitan 

 Bridge. A remnant of the fourth moraine stands out boldly 

 from the northwest base of the Cathedral Rocks in the form 

 of a stony scantily timbered ridge about 30 feet high. The 

 second and third moraines have been largely demolished and 



