0. H. Hershey — River Terraces of California. 249 



tion. The elevation may have contributed to the glaciation, 

 but to accepting it as the sole cause of the glaciation there is 

 one serious objection. That is that the glaciated areas in these 

 mountains are now probably as high above sea-level as they 

 ever have been, yet the existing glaciers, three in number, are 

 insignificant. 



The supposed submerged river valleys in the border of the 

 continental plateau oif the coast of California have been 

 accepted by certain writers as evidence of a former much 

 higher elevation of the California mountains, a probable cause 

 of Quaternary glaciation. For some time, the writer has 

 doubted the pertinence of the argument. In the first place, 

 it is not certain, as pointed out by Law son, "^ that all or any of 

 these long, narrow depressions are submerged valleys of erosion. 

 But, accepting the general opinion that they are such, it is not 

 certain that they were eroded as late as any part of the Glacial 

 Period. Further, it is not certain that they indicate an uplift 

 of the mountains of California above their present altitudes. 



The sub-marine border of the continental plateau west of 

 the Klamath region was depressed, not by a general epeirogenic 

 subsidence but by a sea-ward tilting of the land. Such differ- 

 ential movements of this region have characterized it through- 

 out the late Tertiary and Quaternaiy times, an opinion fully 

 accepted and enlarged on by Mr. Diller in the paper before 

 cited. The land has been swinging on an axis approximately 

 corresponding to the present shore-line. ^^ its not exactly 

 coinciding with the present shore-line have been produced the 

 various elevations and subsidences along the coast. But west 

 of this axis the dominating movements were depressions, sink- 

 ing the plateau border deeper and deeper beneath the sea. 

 East of the axis we have evidence chiefly of a succession of 

 differential uplifts. The supposed submerged river valleys off 

 shore are probably an extension of the upper portion of the deep 

 Pleistocene canons. They were first submerged by a sea-ward 

 tilting of the country long before the earliest glaciation of 

 which we have any record in the California mountains. This 

 statement I base on the fact that, since the submergence, the 

 sea near the present shore-line has cut away so much of the 

 land as that it must have been at work long before the earliest 

 glaciation in the California mountains. The larger topo- 

 graphic features of the present coast line had been developed 

 before the close of the Ped Bluff epoch. The present coast 

 line yields no evidence whatever of a marked elevation above 

 the present at any time as late as the Ped Bluff epoch. 



In short, it is in the submergence and not the erosion of the 

 *Biill. Dept. Geol., Univ. Calif., vol. i, pp. 57-59. 



