THE WORK OF-SSfcEAMS 



125 



Fig. 114. — An^alluvial fan near Salt Lake City. (U. S. Geol. Surv.) 



by evaporation and by absorption into the porous soil. In this way 

 a pile of waste is accumulated, half cone-shaped, with a base varying 

 in diameter from a 

 foot to forty or more 

 miles. Accumula- 

 tions such as this are 

 called alluvial cones 

 when steep, or fans 

 (Fig. 114) when the 

 slope is not great. 

 In general they are 

 composed of coarser 

 materials at the apex 

 and progressively 

 finer ones toward the 

 base, since a stream 

 first drops the larger 

 debris with which it 

 is burdened when its 

 velocity is checked. 



The streams flowing „ J.l G - II5 -~ Th u e San ]o c ^T va T lle , y a . nd Tulare Lake, 



° California, lhe basin of lulare Lake is due chiefly to 



over alluvial cones or t } ie building up of alluvial fans across the San Joaquin 



fans seldom have valley by Kings River and Los Gatos Creek. 



