THE ARAPAHOE GLACIER 



31 



Dr. Fenneman's paper. The other point of shrinkage is where 

 the western surface drainage breaks through the moraine. Both 

 of these ice valleys were greatly deepened, and their sides were 

 much steeper than last year, which suggests stream erosion as 

 the prime cause of the change in the face of .the glacier at these 

 points. However, as 

 the surface streams flow 

 southward, and their 

 valleys are consequent- 

 ly exposed to the full 

 glare of the noonday 

 sun and protected from 

 cooling breezes, the 

 confinement of heated 

 air in the valleys is an 

 element to be reckoned 

 with in the problem of 

 waste at these points. 

 These surface streams 

 on the front of the 

 glacier are made possi- 

 ble by the fact that for 

 some distance back from the terminus the ice is free from open 

 crevasses into which the water arising from surface melting could 

 otherwise plunge. Wasting at these points, while apparently 

 gaining slightly, or at least fully holding its own, at other points 

 along the front of the glacier shows clearly how a glacier may 

 change the shape of its terminus, and consequently of its 

 terminal moraine, as shown by the accompanying diagram. It 

 is probable that the confusion of moraines several miles below 

 the present terminus of Arapahoe Glacier, where they intersect 

 each other at all angles, is partly due to the rapid and repeated 

 changes in the end of the former ice tongue, as well as partly to 

 the melting out of ice blocks in the moraine, as suggested by Dr. 

 Fenneman. 



Where the surface stream enters the terminal lake the ice is 

 now worn to the ground moraine, so that the water issues from 



Fig. I — Diagram on exaggerated scale, the 

 broken line showing change in front of glacier now 

 apparently in progress, from erosion and melting 

 along water courses. 



