ROCK GLACIERS IN ALASKA 



367 



The rock glacier heads in the talus cones which have formed at 

 the base of the steep rock cliffs. These cones have nowhere grown 

 to large size, the materials evidently having moved on down valley 

 as parts of a rock glacier as fast as they were supplied from above. 

 From the base of the more vigorous talus cones smooth, ridgelike lines 

 extend on down the rock glacier, seeming to show that the forward 



Fig. 4. — Profile of rock glacier on McCarthy Creek (Fig. i, No. i). The surface 

 scope of the rock glacier conforms in a noticeable way with the glacial U -shape of the 

 McCarthy Creek valley. 



movement has been uniform and continuous. This is especially 

 well shown for the flow on the opposite side of the ridge (Fig. i. No. 2), 

 in Fig. 3. The longitudinal ridges mark the surface for the upper 

 three-fourths of the total length of the flow. The cirque basin is a 

 hanging valley extending down to an elevation of about 4,000 feet, 

 below which it joins the broad V-shaped valley of the McCarthy 

 Creek. As it passes over the lip of this hanging cirque the rock glacier 

 cascades steeply down the valley side (Fig. 4), and upon reaching 

 the gentler slope below, being no longer confined by restricting valley 



