310 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



lated to the age of American glaciers supply informative background. 

 Be van and Dorf (1932) give a brief digest of the topography and 

 geological history of the Beartooth Range, explaining that in late 

 Tertiary and early Quaternary time, following an uplift of the moun- 

 tains, an ice cap developed on the plateaulike summit of the range. 

 The ice was extensive and when at its maximum development com- 

 prised 15 different glacier systems in the northern and eastern parts 

 of the Beartooth Range. Much of the area has since become a great 

 irregular subsummit peneplain, some 3,000 to 4,000 feet above the 

 surrounding plain, and sloping generally to the southwest. Upon 

 this mountain mass the high peaks are arranged along a divide 

 which runs from northwest to southeast. About the peaks many 

 large cirques occur as silent testimony of early erosive glaciation, 

 and in some of the scooped-out amphitheaters small glaciers now oc- 

 cur, one of them being Grasshopper Glacier. 



The presence of existing glaciers in the Beartooth Range was not 

 reported during the first explorations there. In reviewing North 

 American glaciers, Russell (1885) quotes one of the exploring geolo- 

 gists, TV. H. Holmes, regarding small glaciers in the Tetons of Wyo- 

 ming, stating that in the Beartooth Range he was "unable to discover 

 anything approaching a glacier in appearance, even in the center of 

 the great mass about the sources of Clark's Fork and the Rosebud." 

 If entirely absent then, of course the preserved grasshoppers of Grass- 

 hopper Glacier represent very recent deposits. The first scientist to 

 examine Grasshopper Glacier, so far as I know, was James P. Kimball, 

 of the United States Geological Survey, who made a geological re- 

 connaissance of the area in 1898. In his opinion (Kimball, 1899, p. 

 213) , Holmes did not visit the high country where glaciers are located. 

 I have mentioned the Holmes statement to several scientists who have 

 since visited Grasshopper Glacier, and they too feel that it is unlikely 

 that he actually penetrated the Beartooth Range sufficiently to locate 

 the glacier, in view of its relative inaccessibility. 



How ancient are American glaciers, and do they all date back to the 

 main "ice age" ? In a series of studies by several investigators, the re- 

 sults of which have been assembled by the late Dr. Francois Matthes, 

 then chairman of a committee on glaciers of the American Geophysical 

 Union, much helpful background on the question is supplied (Matthes, 

 1941, 1942a, 1942b) . In brief, it appears that a warm period, called a 

 "climatic optimum," followed the Pleistocene and that the great ma- 

 jority of glaciers now occurring in the United States did not then ex- 

 ist. Studies of the salt content of Owens Lake, which is fed primarily 

 by water from snow fields and glaciers in the Mount Whitney section 

 of the Calif ornian Sierras, and other investigations, suggest that these 

 "modern" glaciers may not date back more than 3,600 to 4,000 years. 



