2O4 



LAKES 



the sea; that of Great Salt Lake contains about 18%; that of the 

 Dead Sea, about 24%. 



Many salt lakes, such as Dead Sea and Great Salt Lake, are 



Fig. 203. Terraces on the shore of the ancient Lake Lahontan, north of Pyra- 

 mid Lake, Nevada. (Fairbanks.) 



descended from lakes which were fresh, while others, like the Caspian 

 Sea, are probably isolated portions of the ocean. Most lakes 

 of the former class have become salt through a decrease in the 



Fig. 204. Tufa domes, Pyramid Lake, Nevada. (Fairbanks.) 



humidity of the region where they occur. The inflowing waters 

 bring in small amounts of saline matter, and the water begins to 

 be salty when the aridity is such that evaporation from the lake 



