322 University of California Publications in Geology [Vol. 13 



On the south flank of the mountains the extremely rugged topog- 

 raphy, as seen just south of San Gorgonio Mountain, gives way to low 

 foothills, dissected by numerous streams draining southward into San 

 Gorgonio Pass. 



The country north of the mountains is typical of a large part of 

 the desert region of Southern California. For the most part it is 

 characterized by great, barren, sandy wastes above which rise steep 

 hills. In some cases the smaller hills are almost completely buried in 

 their own detritus. There are also numerous playas or dry lakes. 



The San Bernardino Mountains contribute to three drainage basins. 

 Bear Creek and all streams south as far as Smith Creek, a small stream 

 three miles northeast of Beaumont, drain into the Santa Ana and 

 thence to the Pacific. The streams between Smith Creek and the 

 divide in Morongo V alley flow into the Salton Sink to the southeast, 

 or are lost in the desert before getting that far. Those north of the 

 Morongo divide and Bear Creek drain into the Mojave Desert, where 

 they are lost by sinking into the sand and by evaporation. 



The San Bernardino Mountains afford splendid views from the 

 summits. Looking over the mountain mass as a whole, the upper 

 portion seems to have a general level from which it drops off rather 

 suddenly on all sides. This is in marked contrast to the San Gabriel 

 Kange, which can be seen in the distance and which seems to have a 

 maximum central height at the intersection of opposing slopes. The 

 significance of this seems to be that the San Gabriel has been uplifted 

 longer than the San Bernardino, and hence has become more reduced 

 on its outer portions. Mendenhall 1 says: 



The San Gabriel and the San Bernardino ranges are adjacent mountain 

 masses, separated only by Cajon Pass, and holding identical relations to the 

 valley of southern California, and to the Mojave Desert, lying to the north and 

 east of it. They also are similarly related to the principal fault lines of this 

 part of California, each of them being bounded along its southern margin by a 

 major fracture, and one of them, the San Gabriel, certainly being limited in a 

 similar way along its northern base, while less definite evidence indicates that 



the San Bernardino range is related in the same way to the desert lowland 



The San Gabriel range has been completely dissected, resulting in thoroughly 

 graded streams, sharp peaks, and knifedike ridges of discordant heights. No 

 level areas at or near the summits, nor in the valley bottoms, exist within the 

 mountain mass. The San Bernardino range contrasts sharply with its neighbor 

 in these respects. Throughout its western end there is a strikingly level sky- 

 line at an elevation of 5000 feet or more. It contains many broad meadows, 

 with lakes and playas, separated by smooth ridges. The topography of the 

 central part is, in brief, topography of an old, well reduced type. About its 



i Mendenhall, W. C, Two mountain ranges of Southern California, Geological 

 Society of America, Bull. 18, 1907, pp. 660-661. 



