244 . PROCEEDINGS OF THE CALIFORNIA 



detected In its depredations upon said tree, but also upon the 

 orange trees. 



The following remarks were made 



On Coast Surface and Scenic Geology. 



BY AMOS BOWMAN. 



The process by M'hich the San Francisco peninsula, and the Contra Costa 

 and Alameda hills and valleys, became dry land, was simple, gradual and com- 

 mon-place, and still going on. It was not one of sudden violence. From the 

 salt marshes to the mountain tops, everywhere are found systematic evidences, 

 in the loosened material, the gravels and sands on the surface of the older rocks, 

 to which geological attention has hitherto been most particularly directed, of 

 the ocean's presence in successive stages and in very recent times. What were 

 islands once, among the hills and valleys of California, now farmed and popu- 

 lated, can be traced by the diagrams. ****** "We may see 

 with our own eyes the birth and creation of the coast counties and California 

 valleys. The rock we rest upon on a Sunday excursion to San Bruno Moun- 

 tains, imparts to us in an hour its hoary wisdom. * * * * The scope 

 and scenery of this section of country can be well studied from the older 

 San Bruno mountains, a point easy of access in an hour from the city ; but to 

 get to the pliocene hills themselves, that are, of course, under water from that 

 island stand-point, one must go to School-house station, and drive three miles 

 along the Iiaguna road, to the south-west. 



Any one would, on attaining the divide here, in full view of the Pacific, ob- 

 serve a peculiarity in the scenic outlines of the hills. The geologist suspects 

 "a formation." A broad plateau lies at your feet. * * * All the highest 

 hills, some 700 feet above the sea, within five miles radius of this point, are 

 pliocene. The abundant fossils in them, as determined by the Geological Sur- 

 vey, tell the story. They were of the period just preceding the creation of the 

 species of mammalian animals now living. * * * * 



The Sun Francisco pliocene and its subordinate terraces, down to the recent 

 valley and the salt marshes of the sea of to-day, were next portrayed by a 

 birds'eye sketch, as they might be seen from a point half a mile in the air, 

 above Goat Island. The same can be recognized from Oakland wliarf, or any- 

 where along the railroad ther.ce to San Leaudro, in a favorable afternoon light. 

 What was most remarkable in this was, the testimony it bore of the exceeding 

 regularity and simplicity of the movement upward, whereby the waters of the 

 sea were caused to depart. The terrace lines showed an equal movement, 

 though sa^rging a little about the road from San .Mateo to Spanishtowu, and 

 southward rising up again into the redwoods near the summit of the peninsular 

 ridge, opposite San Jose. 



Wave-worn beaches and flats on the Mission hills, overlooking San Francisco, 

 show the continuations of the pliocene sea-levels to our very doors. Tiie terrace 

 in the San Bruno mountains which gives scenic individuality in the soft, blue 



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