BULLETIN 



OF THE 



SooiDern Galilornla flcademn ot hmmh 



VOL I LOSANOCLES, CAL, AUGUST I, 1902. MO. 6 



231 \VE?iT FiKST Street. 



PREHISTORIC CALIFORNIA. 



(Continued from July Bulletix ) 



BY DR. LORENZO GORDIN YATES. 



This was followed by a period of excessive precipitation of 

 rain, when rushing torrents of water cut deep chasms where 

 mountains had formerly separated the river channels, and filling 

 up the valleys, thus made more marked alterations in the to- 

 pography, bringing down immense quantities of detritus, de- 

 stroying large forests of timber and scattering the remains of 

 the huge animals which had inhabited them, carrying away much 

 of the deposits of soil which had accumulated during a period 

 of comparative inaction of the elements, and leaving the surface 

 of the earth nearly in the condition in which we find it today. 



It has been shown that there have been several well 

 marked revolutionary epochs which affected large areas of the 

 earth's crust, and also (especially since the Miocene period) 

 large numbers of changes which have been restricted to small 

 areas, and caused local (orogenic) displacements. 



These local changes in the physiography of the region oc- 

 curred at different, but not widely separated epochs of time ; they 

 were gradual in their development and are still going on, as may 

 be shown by the gradual elevation, or depression, at various points 

 along our present coast. 



That portion of California lying south of the Golden Gate 

 seems to exhibit the greater number of these local displacements. 



In some instances are showai upthrusts of the older (some- 

 times granitic) rocks ; this changed the water courses, and new 

 ones were formed ; or, the uplift closed the exits of large bodies 

 of water lying in the interior depressions, forcing them to find, or 

 cut, new outlets. 



Professor Lawson says that, during the Pliocene numerous 

 peaks and ridges rose above the general level. Numerous islands, 

 large and small, fringed the coast of California. There were nu- 

 merous submerged valleys, so that the Coast was well supplied 

 with harbors. In a word, the coast of California at the close of 

 the Pliocene had the aspect of an archipelago. The archipelagic 

 condition endured into the early Pleistocene, and from this con- 

 dition it has been gradually recovering up to the present day." 



