SURFACE OF THE EAKTH 195 



Many beds of rock have been disorganized and much soil 

 made through the diff erent kinds of water-action upon rocks. 



218. Glaciers and the earth's crust. In former times glaciers 

 were important agencies in changing the earth's crust, and in 

 some places their work is still going on (fig. 95). The glaciers 



FIG. 95. A valley glacier 



A glacier on the slopes of Mount Rainier. At the lower end the ice is covered by 

 the broken stone which it is carrying. Photograph by Dr. G. E. Nichols 



have been formed by tremendous accumulations of ice, which 

 fell as snow and then by pressure of its own weight became 

 ice. Ice, like water, flows toward places of lower level, though 

 it flows very slowly. As it moves it may grind or tear away 

 the rocks in its path and carry the fragments along with it. 

 Often these rocks are ground over one another, and marks or 



