254 



GEOLOGY. 



Where ice-caps are developed on plateaus whose borders are 

 trenched by valleys, ice-tongues from the edge of the ice-cap often ex- 

 tend down into the valleys and give rise to one type of valley glacier 

 (Figs. 224 and 227). A second and more familiar type of valley 



W%V\ Moraines 



\kik\ rore6ts 

 I— rJ Olaciens 



Pacific Oceczriy 



Fig. 232. — The Malaspina glacier, Alaska; the best known example of a piedmont 



glacier. (Russell.) 



glacier occu^pies mountain valleys, and is the offspring of mountain 

 snow-fields (Fig. 228). The former are confined chiefly to high lati- 

 tudes, and are distinguished as "polar or high-latitude glaciers (Figs. 227 

 and 229); the latter are known as alpine glaciers (Figs. 228 and 230). 

 The end and side slopes of polar glaciers are, as a rule, much steeper 

 than those of alpine glaciers. When a valley glacier descends through 

 its valley to the plain beyond, it| end deploys, forming a fan (Fig. 231). 

 The deploying ends of adjacent glaciers sometimes merge, and the 

 resulting body of ice constitutes a piedmont glacier (Fig. 232). At the 

 present time, piedmont glaciers are confined to high latitudes. In some 

 cases the snow-field that gives rise to a glacier is restricted to a relatively 

 small depression in the side of a mountain, or in the escarpment of a 

 plateau. In such cases the snow-field and glacier are hardly distinguish- 



