1922] Vaugitan: Geology of San Bernardino Mountains 



335 



Glacial Features 



Glaciation in the San Bernardino Mountains has been described 

 by Fairbanks and Carey, 3 and the present writer can add but little to 

 the record of their observations. Well preserved cirques and moraines 

 constitute the evidence of the former period of ice action. This glaci- 

 ation was of such a local character that the moraines do not extend 

 far beyond the cirques and no typical glaciated valleys are found in 

 the region. Practically all of the detritus is angular and no striated 

 boulders were seen. 



There is a typical glacial cirque on the northeast side of San 

 Gorgonio Mountain. It is very nearly equidimensional, being about 

 500 yards long, 300 yards wide, and 400 yards deep. A moraine 

 extends about 400 yards beyond the cirque and crosses the uppermost 

 part of the north fork of the Whitewater River, thus inclosing a small 

 irregular basin, which, however, is usually dry. After building up a 

 moraine 250 feet high the ice retreated for 150 yards and then con- 

 tinued to drop its load, thus forming a semicircular ridge which rose 

 100 feet above the first. It again retreated, but made a short stop, 

 during which it built a ridge 20 feet in height across the mouth of the 

 cirque. The upper portions of the walls of the cirques are steep, and 

 the surface is extremely irregular due to the plucking action of the 

 ice, which removed great blocks of granite. The lower slopes of the 

 walls are covered with talus. 



On the northwest side of San Gorgonio Mountain there are two 

 cirques facing north and northeast respectively and separated by a 

 sharp ridge (pi. 17A, left of center). The walls of these cirques are 

 ribbed vertically, probably due to the fact that the plucking action of 

 the ice was influenced by a jointage system in the granite. Toward 

 the north the ridge between the cirques has been so reduced that the 

 detritus from the two forms a single large moraine extending about a 

 mile beyond. It is three-quarters of a mile wide and forms a dam 

 400 feet high across the east branch of South Fork. This together 

 with a small artificial dam retains a small body of water known as 

 Dry Lake. 



In the upper part of the west branch of South Fork there are 

 several ridges of debris extending longitudinally down the canon. 

 The north side has a moderate slope and the head of the canon rises 



3 Fairbanks, H. W., and Carey, E. P., Glaciation in the San Bernardino Range, 

 California, Science, n. s., vol. 31, no. 784, p. 32. 



