GLACIERS 



197 



swept snow from the surrounding crags and peaks, the snow 

 fields constitute feeding grounds for the glaciers which descend 

 from them. The larger part of the snow of such fields is 

 really granular, half -formed ice (neve), mantled and bordered 

 with recently gathered snow. 



Movement of glaciers. Most glaciers move with extreme 

 slowness. Other things being equal, a glacier moves faster 



FIG. 203. Glacier des Grandes Jorasses and the Italian face of the Grandes 

 Jorasses. Chain of Mont Blanc. (R. T. Chamberlin.) 



when it is thick, when the slope of its surface is considerable, 

 when its bed is steep and regular, and when its temperature 

 is relatively high, than it does under the opposite conditions. 

 The glaciers of the Alps move on the average a foot or two a 

 day, while some of the great glaciers of Alaska and Greenland 

 move several times as fast. Certain Greenland glaciers have 

 been credited with the very unusual rate of 50 feet and more 

 per day. From what has already been said, it is evident that 

 glaciers move faster in summer than in winter. The ice of a 

 glacier also moves more rapidly in the center at the surface, than 

 along the bottom and sides (Why ?) . Since in the gathering 



