TOPOGRAPHY OF THE PACIFIC COAST. 45 



DEFORMATION OF THE BASELEVEL. 



It is evident that since the Miocene there have been sfreat 

 changes of level in northern California, for instead of the original 

 baselevel of the erosion, we have now prominent mountain 

 ranges, whose sides are furrowed by the deep canons of the 

 rejuvenated streams. 



The deformation of the baselevel may be studied along two 

 lines of evidence: (i) by tracing the present variations of alti- 

 tudes in the original baselevel, which must have had a very 

 gently sloping surface itself, and (2) by tracing the deformation of 

 the lone deposit which, when laid down, must have been below sea 

 level at a lower altitude than the baselevel, because deposited in 

 the water body upon its border. Each line of evidence should 

 corroborate the other and render conclusions concerning the 

 deformation more trustworthy. 



It is impossible to tell from what is known at present the 

 original inclination of the baselevel. It is evident, however, 

 that it must have been considerably less than one degree, for at 

 that angle streams generally erode their beds much more than 

 their banks, and cut canons. 



Upon the western edge of the baselevel, at the foot of the 

 Klamath Mountains in Tehama county, the altitude is nearly 2,300 

 feet, while upon the eastern edge it is considerably less than 

 1,000 feet, giving the old plain in the Greasewood hills a slope 

 of 100 feet to the mile to the eastward. Across this plain the 

 present streams flow in canons 300 to 400 feet deep, and they 

 are still cutting. The canons in general are deepest to the 

 westward and gradually run out to the Sacramento river in the 

 newer deposits which fill the valley. It is evident that since the 

 baselevel was formed, it has been affected by differential eleva- 

 tion in the uplifting of the Coast Range and Klamath Mountains, 

 just north of the fortieth parallel, to the extent of over 2,000 feet, 

 and if we may judge from the traces of the baselevel seen at 

 Shower's pass and South Fork Mountain, the upheaval in the 

 Klamath Mountains has been much greater. It has long been 



