CREST LINES IN THE HIGH SIERRAS 



581 



to nourish glaciers. Thus the glaciers resting against the southward 

 slopes were comparatively ill fed, and the glaciers of the northward 

 slopes were comparatively well fed. The north-south ridges may be 

 assumed to have been swept, then as now, by dominant westerly 

 winds, which carried much snow from the westward slopes over the 

 crests to the eastward slopes, where it accumulated; and thus the 

 glaciers resting against the eastward slopes were better nourished 

 than those of the westward. These peculiarities of snow distribution 



Fig. 2. — Southeastward from Alta Meadows, Sierra Nevada. Compare the 

 northeast-facing walls of the high glaciated valleys with their southwest-facing walls. 



may be readily observed at the present time. If one stands, late in 

 summer, upon a peak in the midst of the glaciated district and looks 

 toward the east or north, he sees bare rock, with only here and there 

 a small remnant of snow ; but if he turns toward the west or south, he 

 looks upon a patchwork of snow and rock in which the predominance 

 of the rock may not at once be apparent. Fig. 7 illustrates the rela- 

 tions of surviving snowbanks in early summer to northward and 

 southward slopes. 



It can hardly be doubted that the distribution of Pleistocene 

 snow deposition stands in causal relation to the distribution of asym- 

 metry in the crest lines of the minor ridges. .And it is in explanation 



