10 



GLACIERS 



The glaciers mentioned are examples of the various forms of 

 moving bodies of land ice. We have (i) Alpine glaciers, of which 

 those in the Alps are types, and are relatively small streams occu- 

 pying narrow mountain valleys. (2) Piedmont glaciers, like the 

 Malaspina of Alaska. These are great accumulations or lakes of 

 ice which form at the foot of mountains, by the coalescence of 



Fig. 37. — Edge of the Greenland ice-sheet, with a glacier descending from it. 

 The dark line is a medial moraine. (Photograph by Libbey.) 



numerous glaciers of the Alpine, or valley type. (3) Continental 

 glaciers are those which cover enormous areas of land, such as the 

 ice-sheet under which nearly all of Greenland is buried and that 

 which covers the Antarctic land. This is a type of especial inter- 

 est and significance to the geologist, because of the light which it 

 throws upon the often mysterious operations of the ice-sheets 

 which once covered large portions of North America and Europe. 

 Glacier Erosion is highly characteristic, and enables us to detect 

 the former extension of ice streams which have greatly shrunken 



