I .AWSON. 



Coast of Northern California. 



263 



that the essential features of the peneplain were developed during the 

 Pliocene period of general depression, while the Wild-cat Series was 

 in process of accumulation, and that the geomorphic cycle was 

 locally interrupted in Humboldt County by the orogenic disturb- 

 ances above referred to, while it persisted to the southward in Men- 

 docino, Sonoma, and Marin Counties, we would have an explana- 

 tion of the bold mountainous features of the more northern portion 

 of the coast. The same movement which deformed the Wild-cat 

 terrane probably broke up the peneplain by throwing up orogenic 

 blocks and anteclinal arches. As the general uplift of the coast 

 did not immediately ensue, there was time for the peneplain to 

 extend in between the ridges of Humboldt County and to truncate 

 the upturned edges of the Wild-cat strata before the more impor- 

 tant epeirogenic movement set in. If, further, we suppose the same 

 orogenic disturbance to have effected a synclinal sag of the coast 

 of Mendocino County, we would have an adequate explanation of 

 the gentle slope of the seaward edge of the coastal plateau, which is 

 elsewhere remarkable for its abrupt character. 



THE (iOLDEN GATE SUBSIDENCE. 



The region of the Bay ot San Francisco and the coast adjacent 

 to it, from Bodega Head to about the latitude of San Jose, a dis- 

 tance of 80 miles, possesses in a marked degree the geomorphic 

 features of a sunken country. These features cause this portion of 

 the coast to stand out in strong contrast to the other parts to the 

 north and to the south of the sunken tract. These geomorphic 

 characteristics are so strongly pronounced that a mere inspection 

 of the maps has enabled Professor Davis to recognize the fact of the 

 subsidence.* The features which afford such unmistakable evidence 

 of depression of the land along this part of the coast are due to the 

 flooding of stream valleys by the sea. As has be'en stated in a 

 former part of this paper, all the streams of the coast from Bodega 

 Bay to Cape Mendocino emerge immediately upon the shore line 

 through narrow canons, and there are no embayments in the shore- 

 line. South of Bodega Head the tide has invaded the lower 



*Geographical Illustrations, p. 36, JS93. 



