ANCIENT GLACIERS. 



123 



upon the western side much below the 6,000-foot level, 

 and only barely came to the edge of the great Snake 

 Eiver lava plains. To the east the movement from the 

 Teton Mountains joined that from various other lofty 

 mountains, where altogether they have left a most intri- 

 cate system of glacial deposits, in whose reticulations Jack- 

 son's Lake is held in place. 



In Utah extensive glaciers filled all the northern val- 

 leys of the Uintah Mountains, and extended westward in 

 the Wahsatch range to the vicinity of Salt Lake City. 

 The mountain region of Colorado, also, had its glaciers, 



mswmi 



. Jamm. 



- -^ 





■ ■ ' ' ' ■■ ■■■ ■ - 



Fig. 37.— Moraines of Grape Creek, Sangre del Cristo Mountains, Colorado (after 



Stevenson). 



occupying the head-waters of the Arkansas, the Platte, the 

 Gunnison, and the Grand Eivers. The most southern 

 point in the Eocky Mountains at which signs of local 

 glaciers have been noted is near the summits of the San 



