THE ARAPAHOE GLACIER 



rock debris. This covering formed such a protection that the 

 outer rim of the glacier wasted more slowly than the ice imme- 

 diately in the rear. A trough has therefore begun, which in 

 another season like the one just past, may grow to such an extent 

 as to leave the inner ridge completely detached from the glacier. 



Fig. 3. — -Terminal moraine ; the dark bands are ice. The rocks hetween the 

 dark bands probably overlie ice. The stratification of the ice is transverse to the 

 bands seen here. 



The third steep ice front behind the second trough is already 

 becoming covered with debris. A series of years of deficient 

 snowfall or excessive melting, or both, might in this way produce 

 a series of concentric ridges having ice cores, whose subsequent 

 melting would leave a topography very much more choppy than 

 that which would result from a series of ordinary recessional 

 moraines. It is suggested that a part of the very confused 

 morainic area several miles east of Silver Lake may thus be con- 

 nected with the wasting of the glacier at an excessive rate. 



