222 



Sierra Club Bulletin. 



LITTLE STUDIES IN THE YOSEMITE VALLEY* 



By Francois E. Matthes. 



I. The Extinct Eagle Peak Falls. 

 At one time in its history the Yosemite Valley boasted 

 one more great waterfall than it does today — or, to be 

 more accurate, a group of falls. A sheer 1,500 feet they 

 plunged, like a cluster of Yosemite Falls coming down 

 together, mingling their spray. No human being was 

 privileged to behold them, it is safe to say, for it was 

 only during glacial times that they existed, at a period 

 when the Yosemite Valley was filled with ice to a depth 

 of some 2^000 feet, and even the little upland valleys 

 tributary to it were smothered under glaciers of consid- 

 erable size. Only the upper portion of the falls was 

 visible, most likely, while their foot must have been deeply 

 ensconced below the surface of the Yosemite glacier, in 

 a chasm of their own fashioning, between ice and valley 

 wall. 



But, it may be asked, if there was no human witness 

 how do we know that this picture is correct? What evi- 

 dence have we of the existence of the falls, of their loca- 

 tion or of the glacial character of their setting? 



It is a well-known characteristic of waterfalls that they 

 cut back the cliffs over which they plunge. Both cliff 

 and fall thus ever tend to retreat, and the rate of retro- 

 gression may under favorable conditions be rapid enough 

 to be appreciable even in a few short years, as in the 

 classic case of the Niagara Falls. 



A waterfall leaping over the side of a steep-walled 

 trough like the Yosemite Valley will therefore in time 

 produce an embayment in the same, a recess breaking into 

 the alignment of the cliffs. An excellent example on a 



* Published by permission of the Director of the U. S. Geological 

 Survey. 



