354 



Adventures in Scenery 



vented overflowing of the lake by an outlet, and Manix Lake 

 became the sink of the Mojave River. On the northeast side of 

 the basin are two deep gravel ridges which mark the shore line 

 of the ancient lake. One of these ridges is crossed by the high- 

 way. From this ridge gravel was taken in the construction of 

 the highway. A period of desiccation or drying up of the lake 



Courtesy Eliot Blackwelder and Journal of Geology 



FIG. 103. Sketch map of Afton Basin, an arm of Manix Lake which in 

 Quaternary time was the sink of Mojave River. The two black stripes indi- 

 cate the positions of the high gravel embankments. 



occurred, and the basin became a playa or dry lake. This period 

 of desiccation was apparently followed by a time of greater 

 precipitation, for a lake returned and reached a level 20 feet 

 higher than the former lake. An outlet was formed over the 

 eastern rim of the basin. At the point of outflow east of Afton 

 the river undoubtedly lowered its channel rapidly through the 

 friable fanglomerate deposits. Down-cutting in the more re- 

 sistant underlying granitic rocks undoubtedly proceeded more 



