SYSTEMATIC ASYMMETRY OF CREST LINES IN THE 

 HIGH SIERRA OF CALIFORNIA.' 



The substance of the present paper was communicated to the 

 Section of Physiography of the Congress of Arts and Science at St. 

 Louis last September. The section had just hstened to Mr. Johnson's 

 paper on "The Profile of Maturity in Alpine Glacial Erosion" (this 

 Journal, pp. — ). Mr. Johnson stated that since his first observa- 

 tions in the Sierra in 1883 his ideas as to the explanation of the phe- 

 nomena had undergone development, and he regretted that he had 

 been unable to revisit the region for purposes of verification. It 

 was therefore a matter of gratification that I was able to supplement 

 his presentation by the statement that during two seasons of explora- 

 tion in the glaciated district of the Sierra I had found his hypothesis 

 of cirque development by glacial sapping of the utmost utility in the 

 explanation of the topography. It happened also that its utihty was 

 illustrated in my discussion of the origin of the special features to 

 which my own communication referred. 



In the higher part of the Sierra Nevada the glacial cirque is a 

 conspicuous feature of the topography. Each main crest of the 

 great mountain mass, as a rule, is bordered on each side by a row of 

 cirques facing outward. Separating the cirques on the same side 

 of the main ridge are subordinate ridges or spurs. Gradually the 

 cirques unite to form glacial troughs, and these troughs are sepa- 

 rated, at a somewhat lower level, by ridges constituting subordinate 

 features of the range. Some of the ridges between cirques and between 

 troughs are equally steep on both sides of their crest lines, but many 

 — a large minority — are notably steeper on one side than on the other, 

 and this asymmetry of cross profile is definitely related to the cardinal 

 points. Ridges trending east and west are steeper on the north side 

 than on the south, those trending north and south are steeper on the 

 east side, and those trending northwest and southeast are steeper on 

 the northeast side. In general, the gentler slope has the grade of a 

 steep roof, and it is often clothed by rock fragments approximately 



I Published by permission of the director of the U. S. Geological Survey. 



579 



