366 



STEPHEN R. CAP PS, JR. 



The rock glacier which was studied in most detail lies on the west 

 side of McCarthy Creek, east of Kennicott (Fig. i, No. i). Although 

 neither so long nor so large in area as others within the limits of the 

 Nizina Special Map, it presents in a typical way many of the notable 

 characteristics of all of the flows (Fig. 2). This rock glacier heads 

 in a glacial cirque in a mountain composed largely of porphyry but 



Fig. 3. — The upper portion of a rock glacier (Fig. i, No. 2), showing the character 

 of the longitudinal ridges, and their relations to the talus slopes in which they head. 



having many inclosed masses of black Jurassic shale, the mountains 

 at the cirque head reaching a maximum height of 6,315 feet. The 

 rock glacier occupies the cirque floor below an elevation of 5,250 feet. 

 Above this talus slopes extend upward for about 200 feet, the remain- 

 der of the cirque walls being bare, ragged cliffs. The porphyry is 

 much fractured and the formation of talus unusually rapid. The 

 valley head lies below the elevation necessary for the maintenance 

 of true glaciers, and the winter's snows disappear completely during 

 the summer. On July 4, the time visited, but little snow remained. 



