San Francisco Bay and Golden Gate 147 



Francisco-Marin faulted block, extending over the Montara 

 block in part, and to the uplifted southwest side of the Berkeley 

 block. A long time elapsed after the uplifting of these great 

 fault blocks, during which time erosion of the land surfaces of 

 these blocks went on. The river, which had been established 

 before the uplifting of the great blocks, continued on its course 

 during the slow rising of the blocks. 



The Region Sank, and Later Uplifted 



At a later time the region about San Francisco Bay subsided 

 so that drainage from the great interior valley to the sea was 

 interrupted. The land sank and the sea came in. The great 

 rivers, San Joaquin and Sacramento, continued to discharge 

 their waters into the basin, but sea waters now entered the basin 

 through the channel of the Golden Gate, and the Great Valley 

 through which most of the drainage of the State had reached 

 the sea was blocked. The intermingled waters from the rivers 

 and those from the sea were ponded. Thus the region of San 

 Francisco Bay became a vast drowned valley. Richardson Bay 

 and San Rafael Bay are drowned valleys of streams that flowed 

 into the basin of San Francisco Bay. San Pablo Bay and Suisun 

 Bay, and indeed the southern end of San Francisco Bay, should 

 be regarded as the submerged lower portions of the valleys that 

 lie above them, viz., Napa, the Sacramento, and the Santa 

 Clara. 



Stream Co^^rses Changed 



By the uplifting of the land the courses of streams entering 

 the basin have been modified and changed. On the Marin 

 Peninsula a valley having steep sides extends from the head of 

 Richardson Bay on the east across the mountain range of Mt. 

 Tamalpais to the ocean at Tennessee Cove. At the present 

 time two small streams occupy this valley, one flowing to the 

 northeast into Richardson Bay and the other to the southwest 

 to the ocean. The "divide" is about midway of the original 



