ROCK GLACIERS IN ALASKA 375 



in this region, if these features are not landsHdes. None were seen 

 below the miles of prominent, steep cliffs of the area, though ordinary 

 talus cones are abundant. 



9. One rock glacier, in a western tributary of McCarthy Creek 

 (Fig, I, No. 4, and Fig. 9), shows all the characteristics of a typical 

 rock glacier at its upper end, but at the mouth of the hanging valley 

 on which it lies, it streams down to McCarthy Creek as a very perfect 

 talus cone. If it had come down suddenly as a landslide, no such 

 perfect talus cone would have been formed. The presence of the 

 talus cone indicates that the material of which it is composed was 

 supplied slowly, thus enabling the cone to build up symmetrically. 

 The talus cone is still being supplied with material by the rock glacier, 

 as may be seen in the figure from the way in which the talus from 

 above is invading the patch of alder bushes on the side of the cone. 



10. Wherever two rock glaciers in adjacent cirques join below 

 to form a single flow, the point of junction shows that the two branches 

 have flowed together synchronously without any evidence that the 

 flow from one branch has come down and overridden that from the 

 other (Fig. 10). 



