THE PLEISTOCENE OR GLACIAL PERIOD 907 



into existence, but after a time it appears to have dried up, probably 

 because of another change of climate. Still later, the lake was 

 restored, and its water rose higher than before, and found an outlet 

 to the northward. In the course of time, evaporation from the 

 lake again became more considerable than precipitation and inflow, 

 and the lake gradually shrank to the present dimensions of Great 

 Salt Lake. At its maximum, Lake Bonneville was more than 1000 



Fig. 597. Shore of former Lake Bonneville, Wellsville, Utah. (U. S. Geol. 



Surv.) 



feet deep, and had an area of more than 19,000 square miles; the 

 maximum depth of Great Salt Lake is less than 50 feet (average 

 less than 20) and its area but about one-tenth that of its ancestor 

 It is apparently doomed to still further decrease by the diversion 

 of water from the feeding streams for purposes of irrigation. 



Terraces, deltas, and embankments of other sorts were developed 

 about the shores of Lake Bonneville wherever the appropriate con- 

 ditions existed (Figs. 269 and 597), and because of the aridity of 

 the climate since the lake sank below them, they have been modified 

 but little by erosion. As the lake dried up, deposits of salts were 

 made, among which sodium chloride and sodium sulphate are most 



