EVIDENCE FROM THE SIERRAS 37 



Professor J. C. Branner* has shown that the singular topography 

 about the cataracts in the Yosemite valley was produced by the more 

 rapid down- cutting by the streams draining the glaciers than by the ice 

 itself. He sa} r s: 



" The evidence of the falls at the mouths of the hanging valleys shows that the 

 wearing done by the ice was trivial compared with the wearing done by the glacial 

 streams. The subglacial streams also cut channels beneath the ice a great deal 

 faster than the ice cut the broader floors on which it moved." (Page 551.) 



The latest paper is by Lawson,f on the upper Kern valley, in the high 

 Sierras, a very interesting description of a most remarkable valley and 

 region : 



11 The canyon of the upper Kern is one of the great canyons of the Sierra Nevada, 

 and in some respects it is the most remarkable of them all. . . . But while it 

 is a feature essentially due to stream erosion its characters as such have been modi- 

 fied by its having been occupied for a time by along trunk glacier, which extended 

 down the canyon as far as the mouth of Coyote creek and which was fed by sev- 

 eral tributary glaciers. ... In consequence of this episode in its history the 

 canyon above Coyote creek has the typical U shape in cross profile so characteristic 

 of glaciated mountain valleys." (Pages 328, 329.) 



"The width of Kern canyon below the Kern-Kaweah river does not appear to 

 have been appreciably increased by the occupation of the ice. This is practically 

 proven by the following consideration: The depth of the ice in the canyon aver- 

 aged probably not more than 1,200 feet. The walls of the canyon are about twice 

 this height, and the lateral recession of this upper portion of the walls in conse- 

 quence of glacial sapping or scour at their base could only have been by a process 

 of shedding rock fragments upon the surface of the glacier. These fragments would 

 accumulate at the terminal moraine ; but the volume of the two terminal moraines 

 together does not exceed 2,100,000 cubic yards. If we distribute this over the upper 

 1,200 feet of both walls of the canyon for the distance of 14 miles from the Kern- 

 Kaweah river to the main terminal moraine, it would make a layer 4 inches thick. 

 If we consider that probably half of the moraine came from sources outside the 

 canyon, the layer would be reduced to 2 inches. This estimate may be modified 

 and corrected in a variety of ways, but it leaves a quantity for the glacial widening 

 of the canyon which is negligible. The canyon, then, had practically the same 

 width before its occupancy by ice that it has today." (Pages 349, 350. ) 



The perfectly straight canyon was occupied by a bolt of ice more than 

 20 miles in length, formed by the junction at the valley head of two 

 strong glaciers, and joined along its course by six tributaries, each formed 

 from several glaciers (see Lawson's plate 31). So far as the drainage 

 area (volume), valley conformation (freedom of flow), and latitude (tem- 



*J. C Branner : "A Topographic feature of the hanging valleys of the Yosemite." Jour. Geol., 

 vol. 11, pp. 547-553, 1893. 



tA. J. Lawson: '• The geomorphogeny of the upper Kern basin." Univ. of Calif. Pub., Bull. Dept. 

 Geol , vol. 3, 1904, pp. 291-376. 



VI— Bull. Geol. Soc. Am.. Vol. 16. 1904 



