;o6 



LEWIS G. WESTGATE 



valleys which enter Lake Creek above Twin Lakes are either short 

 V-valleys, unoccupied by glaciers, or occupied only by masses of ice 

 forming cirques at their head, or else are, like Echo Gulch, U -valleys 

 in their middle and upper course, and V-valleys below, the ice- 

 tongue not having reached the main valley. 



4. Two periods 0} glacial erosion in the gorge. — The moraines of 

 the Twin Lakes glacier show two glacial periods separated by a long 



Fig. 10. — Hanging valley of Crystal Lake Gulch. 



interglacial period, during which the cutting of the rock-gorge of 

 the Arkansas took place. Only portions of the earlier moraine 

 remain, but they show that certainly in part, and probably on the 

 whole, the earlier glacier reached farther into the valley than did 

 the later glacier. The gravels associated with this earlier moraine 

 are much greater in bulk than those associated with the later moraine. 

 The material of the moraine was obviously derived from the valley 

 of Lake Creek, and the great abundance, in the gravels, of material 

 derived from the valley of Lake Creek indicates that the gravels. 



