42 Adventures in Scenery 



San Joaquin and Sacramento Rivers 

 Flow Where Opportunity Offers 



The two principal rivers of California, the Sacramento and 

 the San Joaquin, conform only in their upper courses to the 

 principles indicated for the development of rivers on an ideal 

 continent. The San Joaquin and its tributaries flow down the 

 western slope of the Sierra Range. These streams, or those that 

 preceded them, probably once discharged their waters into a 

 body of water that occupied the great basin now known as the 

 Great Valley of California. These streams and their ancestors 

 have been carrying sediments into the Great Valley for long 

 ages. The great mountain uplift which preceded the present 

 Sierra Range was eroded by streams, and was worn down to a 

 plain, and the rock materials carried by the streams now form 

 strata of sedimentary formations that form the floor of the 

 Great Valley. The streams that now flow down the Sierra 

 slope may have had their courses determined by drainage sys- 

 tems that had been developed before the latest upheaval of the 

 Sierra Range. However, in their upper courses they are now 

 active streams. Tributaries of the main streams are pushing 

 their heads back into the land. But the main streams have 

 been developed not by pushing back from the sea landward but 

 from greater rainfall and from melting glaciers high on the 

 mountains. They thus have come to flow where opportunity 

 best offered. They are subsequent streams, streams that have 

 developed subsequently to the uplifting of the land. They have 

 cut deep canyons because they flowed across hard rocks, and 

 carried much sand and gravel which have acted as chisels cut- 

 ting the rocks over which they were driven by rapid streams. 

 Breaks in the crust of the earth, faults, have in some cases fur- 

 nished channels ready made, and streams have followed along 

 their courses. Streams whose courses have been determined by 

 rock formations, that is, streams that follow the contour of the 

 land, are called subsequent streams because they follow the con- 

 tour of the land. 



