LAKE EROSION 



121 



are not heavy enough to effectively cut back the shores, while the 

 current of water through the lake is too slow and the sediment 

 transported too small and light to erode the bottom as a river 

 does. In great lakes, such as those which drain into the St. 

 Lawrence, storms develop a very heavy surf, and such lakes 



Fig. 45. — Beach on Lake Ontario. (U. S. G. S.) 



eat into their shores as the ocean does, but the very small 

 tide confines the work of the waves within narrower limits, and 

 the lighter breakers are less effective. Lakes are subject to 

 various accidents which cause great fluctuations of the water- 

 level. Deserted shore-lines are marked by beaches and terraces. 

 The method of denudation by lakes is the same as that of the sea, 

 but the modes of accumulation of material are characteristically 

 different. 



