GLACIAL DEPOSITS 



153 



V. Ice Deposits 



Deposits made, directly or indirectly, by the agency of ice are 

 very characteristic, and though some are formed on land and some 

 under water, it is desirable to consider them together in a single 

 section. The peculiar features of ice formations may be much 

 obscured by the action of water, either at the time of their deposi- 

 tion or at some subsequent period. Ice deposits play but a very 



Fig. 57. — Glacier des Bossons, Switzerland. The terminal moraine follows the 

 lower end of the glacier. (Photograph by McAllister.) 



small part in the construction of the earth's crust, but the light 

 which they throw upon changes of climate and similar questions, 

 lends them an unusual degree of interest. 



Glacial Deposits. — We have already learned that glaciers carry 

 with them great masses of debris, either in the form of lateral 

 and medial moraines upon their upper surfaces, or frozen in the 

 interior of the ice, or pushed along beneath it. When the glacier 

 arrives at its lower end, where the rates of motion and melting 



