THE SAX FRANCISCO EARTHQUAKE 73 



Farther south on the ocean side of the San Francisco peninsula the 

 coast is fringed with a raised beach, such as occur so abundantly along 

 much of the California coast. The top of this beach is 75 to 100 

 Ei ct above sea-level. At Purisima, the creek of that name runs out 

 across this raised beach through a slightly cut channel to the very 

 edge of the plane where it drops as a water-fall directly into the surf. 

 As the rocks through which it would have to cut to reach sea-level are 

 the only partly consolidated Merced series, there is striking evidence 

 of the recency of the raising of the beach. Again just south of San 

 Francisco are many places in which the recently raised deposits and in 

 slighter degree the underlying Merced rocks have been trenched to 

 depths of as much as 75 feet since the production of the Coast and 

 Geodetic Survey map of this region in 18G9. The fact that so large a 

 part of these recent deposits still remains in view of this rapid erosion 

 impresses one in the field most profoundly. 



There is another line of evidence to which the writer refers with 

 some hesitation. Indian shell mounds abound along the California 

 coast. In many cases these now occur spread out in thin sheets, ap- 

 parently forming the surface layer of the raised beaches over such large 

 areas that in his first study of them he was deceived and considered 

 them in many cases as marine deposits. As he remembers them now, 

 he can not help thinking that in many cases they have been reworked 

 by water before the final uplift. In one case 'the writer found an 

 Indian skeleton, evidently formally buried, half exposed in the side of 

 a stream channel so narrow as to force one to the conclusion that the 

 channel has been entirely cut since the burial of the body. This is 

 only a fraction of the evidence that in the field leads one to consider 

 this last uplift as a thing of yesterday, and in all probability of to-day 

 also, or, in other words, that these differential uplifts are still in 

 progress. 



A final question of maximum interest is : Is there physiographic or 



Fig. 6. A Portion of the U. S. Geological Survey Map from Mussel Rock southeast- 

 ward nearly to San Andreas Lake, showing topographic environment of a chain of ponds and 

 undrained basins believed to be due to recent earthquake movements. 



