194 



PHYSICAL GEOLOGY 



A glacier spreading in all di- 

 rections from its center on a 

 plain or plateau is an ice sheet 

 or ice cap (Fig. 212). Glaciers 

 confined to valleys are valley 

 glaciers (Figs. 201, 202, and 

 203, and Plate X). Com- 

 pound glaciers formed on plains 

 or plateaus at the base of moun- 

 tains by the union of valley 

 glaciers which have spread out 

 in front of the mouths of their 

 mountain valleys, are piedmont 

 (foot of the mountain) glaciers 

 (Fig. 211). 



VALLEY GLACIERS 



Distribution and size. 



There are hundreds of valley 

 glaciers among the mountains 

 of Alaska, western Canada, and 

 northwestern United States. 

 Here high mountains near the 

 coast force the vapor-laden 

 ocean winds to precipitate 

 much moisture in the form of 

 snow. Seward Glacier, the 

 largest valley glacier in Alaska, 

 is over 50 miles long and 5 

 miles and more wide. Very 

 few glaciers in the United 

 States are more than a mile 

 long. There are nearly two 

 thousand glaciers in the Alps 

 Mountains. The longest of 



