The Colorado Desert 111 



Cocopah Mountains, and was in time built entirely across the 

 gulf. This ridge was built up till its crest was 40 feet above 

 the water level of the gulf. Then the waters as they continued 

 to be discharged into the filling gulf spread each way from the 

 backbone of the delta, alternately southward to the Gulf of 

 California and northward into the basin which had been cut 

 off by the delta ridge. Thus the trough of the original Gulf 

 of California was separated into two parts. The basin to the 

 north, which represents the extreme north end of the trough, 

 was filled with water, probably originally salt or brackish. 

 This body of water has been called Lake Cahuilla, or Blake Sea, 

 the former name being given by its early discoverer, Prof. W. 

 P. Blake, and the latter assigned in honor of the man who first 

 discovered this remarkable region and explained its true char- 

 acter in 1853. 



It is thought that the waters alternately discharged into the 

 gulf below and to Lake Cahuilla above as floods carried debris 

 and repeatedly blocked the channels of discharge. If Lake 

 Cahuilla was at first salt it must soon have become brackish or 

 fresh with the influx of waters from the river. Tides which 

 drive in from the ocean with great force disrupted the channels 

 by which the waters of the inpouring river sought to reach the 

 ocean. Due to the intense heat, evaporation carried away the 

 water from Lake Cahuilla, and its surface was gradually low- 

 ered. It ultimately became a dry basin with layers of salt on 

 its bottom. This is called the Salton Sink. 



The long depression in which the waters of the Gulf of 

 California had ebbed and flowed was a trough or sunken portion 

 of the earth's crust formed by faulting of the rocks. The basin 

 is walled in by mountains on either side. With the building of 

 the delta ridge from Yuma to the Cocopah Mountains, and the 

 further filling of the trough with sediments, the sea was effec- 

 tually shut out, and Lake Cahuilla came to occupy the north 

 end of the trough. The Chocolate, Chuckawalla, Cottonwood, 

 and San Bernardino ranges on the northeast, and the San 



