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University of California. 



[Vol. 1. 



stretches of the stream valleys, and made long, finger-like bays of 

 them. The most notable of these flooded valleys is Tomales Bay, 

 a narrow inlet parallel to the coast, about 15 miles long, and less 

 than a mile in average width. The stream valley which now forms 

 Tomales Bay was clearly a valley of subsequent drainage, and the 

 transverse outlet was probably between Tomales Point and Bodega 

 Head. Not only is the main valley flooded, but the lateral feeders 

 are, also, in a more or less pronounced way invaded by the tide. 

 The most striking of these is Walker's Creek, which presents all 

 the characters of a fiord, being a narrow tidal inlet with high, pre- 

 cipitous walls on either side. The stream originally cut across a 

 coastal ridge, having been probably a superimposed stream antece- 

 dent to at least the last thousand feet of uplift of the coast which 

 preceded the subsidence that now floods its trench with the sea. 

 Entering Bodega Bay, which is the extension of Tomales Bay, are 

 two other similar creeks traversing the same ridge, the San Antonio 

 and the Estero Americano, both of which allow the tide to extend 

 several miles inland. Tomales Bay forms a natural trap for the 

 shore drift, and this material, together with the delta material of the 

 various small streams, is rapidly shoaling the bay, so that at present 

 it is unfit for shipping. 



The valley, which by flooding has thus become an inlet of the 

 sea, could only have been eroded to its present depth during the 

 latter part of the uplift, and the subsidence which caused the drown- 

 ing of the valley was, therefore, practically subsequent to the uplift. 

 There is, however, nothing to show that the elevatory movement 

 which affected the coast as a whole had entirely ceased when the 

 subsidence was inaugurated. The later movements of the uplift, 

 and the earlier of the depression, may, therefore, have been coeval. 



Even more significant of the recency of the depression are the 

 flooded streams which end at the sand beach of Drake's Bay. 

 These are called on the Coast Survey chart, Drake's Estero. These 

 are finger-like inlets which are very clearly flooded stream canons, 

 representing a drainage convergent towards the south. These 

 canons have effected the dissection of a plateau which is a marine 

 zvave-ait terrace, representing one of the later stages of the epeirogenic 

 uplift of the coast. Ballenas Bay is a similarly flooded valley which 



