46 Adventures in Scenery 



Salinas thence proceeds northward on the floor of the great 

 valley. 



Such behavior of a river can hardly be explained on the 

 basis of differences in hardness or texture of the rocks encoun- 

 tered by the streams. It has been stated that the history of 

 drainage in this region goes far back through periods of great 

 change in the development of the landscape. During preced- 

 ing geologic periods, the full story of which need not be entered 

 into here, this region was depressed, or subsided, below sea level, 

 and sediments were deposited of widespread geologic forma- 

 tions. Subsequently upheaval occurred and erosion of streams 

 ensued. During long ages (as time is measured in years) ero- 

 sion continued and the rock formations that had been laid down 

 in what was probably a bay or arm of the ocean were carried 

 away. Drainage systems adapted to the conditions that then 

 prevailed were developed. The rocks that formed the surface 

 of the land then are thought to have been soft and easily eroded. 

 The ancestor of the Salinas River was developed upon the land- 

 scape. It cut down its channel into the soft rocks which over- 

 lay the granite of the present mountain ranges. As the channel 

 of the Salinas River was deepened it came upon the hard granite 

 rocks below. A river cannot change its course simply because 

 it cuts down and encounters hard rocks. What it does is to 

 proceed to cut for itself a channel into the hard rocks. That 

 is what the Salinas River did, and the river now flows through 

 canyons cut in hard granite rocks, because it could not get out 

 of its established channel. Because the land stood at a higher 

 altitude than now the current was more swift, and as sand and 

 gravel were carried from higher lands these in the accelerated 

 stream chiseled the hard granite rocks and cut the canyon. The 

 broad flat plain of Salinas Valley is part of what is called a pene- 

 plain. This was formed by the erosion of streams that reduced 

 the region to a stage of old age, leaving only the hard ridges of 

 granite or uplifted mountain masses standing above the general 

 level. The drainage that had been established on the earlier 



