1922] EDWARDS, GEOLOGICAL WORK AT RAINER NATIONAL PARK 



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green or blue and a very beautiful color banding of the ice is shown in 

 this way. Some of the crevasses are of great width and depth, but 

 many of them are relatively small openings in the surface of the ice. 

 Those which cross the glacier from one side to the other are called 

 "transverse crevasses" and are usually bowed with the convex side 

 down stream. This is due to the swifter motion of the central part 



Fig. 40. — Looking into a large crevasse in Nisqually 

 Glacier. The rock dust embedded in the ice is clearly 

 shown in the foreground. 



of the glacier. Crevasses, when once opened, are not permanent, but 

 change from day to day, the ice closing together again whenever ten- 

 sion is relieved or breaking open in new places as tension is again put 

 upon it. Many of these crevasses are crossed by ice bridges and it is 

 bv means of these that one is enabled to cross from one ice block to 



