40 Adventures in Scenery 



that has been described occur. They are mostly short. The 

 two great rivers of the State, the Sacramento and the San 

 Joaquin, are not "consequent" rivers. The Feather, the Moke- 

 lumne, the Tuolumne, the Merced, Kings, and Kern, are not 

 consequent streams. Some tributaries of these rivers are con- 

 sequent; have developed from their own mouths where they 

 join the parent stream. That is the way streams develop where 

 rains fall on the land and drainage develops without interfer- 

 ence of some geologic catastrophe. But great catastrophies 

 have occurred in California. Great upheavels, great ruptures 

 of the earth's crust, have occurred. Rivers that had been es- 

 tablished as a consequence of the natural slope of the land have 

 been interrupted by the upheaval of mountain ranges, and by 

 the outpouring of vast masses of molten rock from the interior 

 of the earth, by the outflow of lava from volcanoes. Ice of 

 great glaciers flowed over large areas and filled river valleys, and 

 on melting left deposits of gravel, sand and clay. Sometimes 

 these deposits filled and obliterated valleys. Valleys were some- 

 times dammed and lakes formed in basins, and new outlets had 

 sometimes to be formed. 



Stream Courses Determined by Rock. Structure 



Thus "subsequent" streams came, following or subsequent 

 to the changed conditions of the land surface. The changed 

 conditions of the land surface were not in any way caused by 

 the streams that already existed. The new streams developed 

 to fit the new conditions. Since the streams followed the 

 changes in the surface of the land and adapted themselves to 

 the new conditions they are spoken of as subsequent streams, 

 and the drainage is subsequent drainage. The upper Sacra- 

 mento, Feather, San Joaquin, and many rivers of the western 

 slope of the Sierra Nevada Range would not have been where 

 they are had it not been for the great uplift by which the range 

 was formed, and had not the great slope from the crest of the 

 range toward the west been established. The Truckee River 



