WORK OF GLACIERS 



127 



or scarcity of sharp angled rocks, and cirques. How is he to rec- 

 ognize glacial erosion in other regions? A trip to a region con- 

 taining rock exposures such as rock hills but not rock valleys 

 will convince him that the facts already learned can be applied. 

 In traveling over such a region, however, he observes that the 

 rock hills have a gentle slope on the side from which the glacier 

 came (stoss side) and a steep slope on the other (lee) side (Fig. 

 2). Why do glaciers give this characteristic shape to a rock 

 hill? Are there exceptions? Can this shape be used as a proof 

 to show the direction of ice movement? Can the grooves and 

 scratches be used for the same purpose? are some of the prob- 

 lems that confront him. 



Fig. 2. Rock hill shaped by a glacier passing over it from right to left. 

 WORK OF DEPOSITION. 



Let us secure a good view point near the lower end of the 

 same mountain valley where we can look up the valley and also 

 out upon the plain. How was that semi-circular ridge (Fig. 3) 

 around the mouth of the valley — the terminal moraine — formed? 

 From this position he can form a mental picture of the ice mass 

 that occupied the valley, depositing great quantities of loose rock 



Fig. 3. Terminal moraine around the lower end of valley 

 shown in Fig. 1. Both pictures were taken from the same 

 point. 



