160 WORK OF SNOW AND ICE 



are less favorable. The topography of the ground moraine (Plate 

 XIV) is, as a rule, less uneven than that of the terminal moraine 

 (Fig. 168). 



Lateral moraines. Lateral moraines are the product of valley 

 glaciers. The lateral moraines on such glaciers are let down on 

 the surface beneath when the ice melts; but the lateral moraines 

 in a valley from which the ice has melted are not merely the lateral 

 moraines which were on the glacier. They are made up chiefly of 

 drift accumulated beneath the sides of the glacier. This accumula- 

 tion is the result of the lateral motion of the ice from the center to 



Fig. 164. A lateral moraine ielt by a former glacier in the Bighorn Mountains 

 of Wyoming. (Photo, by Blackwelder.) 



the sides of the valley. Such sub-lateral accumulations are akin to 

 terminal moraines. Some of the lateral moraines of ancient valley 

 glaciers, those like of the Uinta, Wasatch, and Bighorn mountains 

 are several hundred feet high (Fig. 164), or even as much as a thou- 

 sand. In northern Italy a lateral moraine is said to be more than 

 2,000 feet high. 1 



Distinctive nature of glacial deposits. The deposits made by 

 glaciers are distinctive. In the first place, the ice. does not assort 

 its drift, and bowlders, cobbles, pebbles, sand, and clay are con- 

 fusedly commingled (Fig. 165). In this respect, the deposits of ice 

 differ notably from those of water. Furthermore, many stones of 

 the drift show the peculiar type of wear which glaciers inflict. 



1 Geikie. The Great Ice Age, jd ed., p. 529. 



