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STEPHEN R. CAPPS, JR. 



walls, it spreads out in a great lobe along the valley bottom. In this 

 lower lobe the longitudinal surface markings disappear and give place 

 to a set of concentric ridges or wrinkles, shown in Fig. 2, and in greater 

 detail in Fig. 5. The origin of these wrinkles is not clear, but they 

 strongly suggest rings of growth, and may represent the amount of 

 annual movement of the rock glacier. 



Fig. 5. — Concentric ridges on lower portion of rock glacier in McCarthy Creek 

 valley (Fig. i, No. i). 



At its foot the flow has pushed across the valley bottom almost 

 to the base of the east valley wall. McCarthy Creek has been forced 

 to the eastward, and occupies a narrow channel between the foot of 

 the rock glacier and the rock valley wall (Fig. 6). The foot of the 

 rock glacier is being cut into by the stream, and in places shows a 

 face 75 to 100 feet high in which the slope is about 35 degrees, or the 

 angle of rest for this material. The stream has been able only to 

 keep its channel open along the foot of the rock glacier, and it seems 

 probable that the flow is moving forward as fast as the stream can 

 cut it back. 



