Geol.— Vol. I.] TURNKK—ORIGIN OF YOSEMITE J\4LLEy. 285 



equivalent in the precise fraction of a foot of rock annually 

 removed from the area drained by the glacier. The amount 

 of material falling from the cliff and deposited as moraines 

 may evidently be estimated directly from the moraines them- 

 selves. Of course this method applies only to living gla- 

 ciers. Helland^ estimated that there is annually carried off 

 by the Justadel glacier in Norway, covering an area of 830 

 square kilometers, 180,000,000 kilograms of rock, at spe- 

 cific gravity 2.6, or an average of 217,000 kilograms per 

 square kilometer. As pointed out by Geikie, this includes 

 the sediment washed into the glacial river from surrounding 

 slopes by running water, and in summer the amount from 

 this source must be considerable. At the same rate, the 

 Yosemite glacier, with a superficial extent during the epoch 

 of maximum glaciation of about 300 square kilometers, must 

 have carried off annually during that epoch 65,100,000 kilo- 

 grams of rock. These are "very large amounts, and if 

 reliable would indicate a greater degrading power than is 

 ordinarily accredited to glaciers. 



Russell" attempted to determine the amount of material 

 removed by ice action from Lundy Canyon, on the east 

 slope of the Sierra Nevada, by the size of the moraines and 

 the size of the delta where Lundy Creek enters Mono Lake. 

 This delta is regarded by Russell as being largely made up 

 of glacial sediment. The conclusion was that the amount 

 removed in this manner from the canyon was greatly less 

 than its entire cubic space, indicating that the canyon had 

 been largely formed by stream erosion before being occu- 

 pied by the ice. However, as Russell remarks, the amount 

 of fine sediment carried farther into the lake and deposited 

 cannot be estimated. The conclusion of Russell as to the 

 inadequacy of ice erosion to account for the canyons drain- 

 ing into Mono Lake applies with equal cogency to the greater 

 canyons on the west slope. The amount of morainal mate- 

 rial in the Merced drainage area is insignificant in compar- 

 ison with the size of the canyons of the Merced and its 



1 A. Helland, Geol. Foren. Stockholm Korhandl., 1874, Band II, pp. 212-213. 



2 Quaternary History of Mono Valley, p. 349. 



