Sierra Club Bulletin. 



Vol, V. San Francisco, June, 1905. No. 4. 



THE GRADE PROFILE IN ALPINE GLACIAL 

 EROSION.* 



By Willard D. Johnson. 



It was early asserted of the canons of the Sierra 

 Nevada that they are essentially the products of glacial 

 erosion. A continuous glacier mass, or ice-cap, was sup- 

 posed to have covered the summit region of the range, 

 with individual glacier tongues channeling its flanks to 

 the foothills, on the broad western flank descending close 

 to sea-level. These canons, except as to their lower and 

 older parts, were described as U-troughs. There was 

 no mention, however, of distinctive character in their 

 longitudinal profiles. 



My own acquaintance with the phenomena of Pleis- 

 tocene glaciation of the alpine type had its beginning in 

 the High Sierra, in 1883. this later date prevailing 

 opinion apparently leaned to quite the opposite view, — 

 that glacial occupation, even here, had been relatively 

 protective of the preglacial topography. It was shown 

 that the earlier announcement had been without sufficient 

 warrant. It appeared that glacier extension on the west 

 had fallen notably short of the range-foot. There was 



* Read at the International Congress of Arts and Science, St. Louis, 

 Sept. 21, 1904. Reprinted, with changes by the author, from the Journal 

 of Geology, October-November, 1904. 



