The Behavior of Rivers 55 



does fall. Evaporation is very rapid. The river loses more and 

 more of its water. Presently there is no river save occasional 

 pools separated by beds of sand, silt, and gravel. For a short 

 time in the winter and spring the river operates. Then it 

 dwindles. At length about 125 miles from its "source" in the 

 San Bernardino Mountains it gives up altogether and spreads 

 out what water it still has on the flat saucers of Soda and Silver 

 lakes (playas). So it ceases to be a river. It has "retired" 

 from active service. It is a relic of what was under a more 

 humid climate a real river. (That was during the Ice Age, 

 when waters from melting glaciers kept it at flood stage.) 



Retired Rivers of the Desert 



With all its eccentricities the Mojave River tells of a past 

 that is far gone. Once the land was higher. Much rock and 

 soil have been carried away by erosion. Once the proud river 

 ran over a landscape that was many feet above the present land- 

 scape. The granitic rocks of the mountains that now stand 

 above the plain were buried underneath softer overlying forma- 

 tions. The river then went about its business. It cut down 

 into the soft rocks. Presently it encountered the granite rocks 

 below. It had established a channel. It could not get away 

 from the channel. It carried sand and gravel, and these served 

 as chisels to cut the hard granite. So as the landscape was re- 

 duced by erosion and lowered the river kept cutting down its 

 channel. And thus there is now the granite canyon through 

 which the river moves (when there is any water) instead of 

 going around the mountains over soft easily eroded rocks. This 

 is to say, the river has been "superimposed" upon the present 

 landscape let down from above. Thus it started out as a con- 

 sequent stream. It got itself superimposed upon a hard rugged 

 landscape, and finally, its work being done it has "retired." It 

 is dead. Its place is marked by its channel and by the work 

 it has done. 



The Amargosa River has a hard time trying ever to become 



