THE WORK OF SNOW AND ICE 



257 



tributaries out of topographic adjustment. Thus if a main valley 

 is lowered 100 feet by glacial erosion while its tributary is not 

 deepened, the lower end of the latter will be 100 feet above the 



Fig.. 209. A hanging valley near Lake Kootenay. (Photo, by Atwood.) 



former when the ice disappears. Such a valley is called a hanging 

 valley (Fig. 209). Such valleys are common in regions which were 

 recently glaciated, like the western mountains of North America. 



Fig. 210. Diagram representing a hill unworn by ice, and the irregular con- 

 tact of soil and rock. 



Fig. 211. Diagram showing the effect of glacial wear on a hill such as is 



shown in Fig. 210. 



Ice-caps which overspread the surface irrespective of valleys 

 and hills tend to reduce the angularities of the surface. Hills and 

 ridges are cut down and smoothed (Figs. 210 and 211); but since 



