2 SOUTHERN CALIFORNIA GEOLOGY 



consideration of the rock materials, their nature being 

 for the most part understood. 



To comprehend the occurrence and significance of 

 the faulting in California to which the subject of 

 earthquakes is so intimately related one must have an 

 understanding of the broader features of its geography 

 and geology. Inasmuch as the earthquake situation 

 cannot be viewed without this knowledge and as no 

 serious attempt to present the latter has ever been 

 made, I see no other alternative than to at least epito- 

 mize the same, as is herein done. This effort has been 

 no small task, as it has involved the assemblage and 

 classification of thousands of observations and the con- 

 densation into a few pages of a subject that should 

 fill many. 



Furthermore, since I believe that the lessons on 

 geologic history teach us that each relief-shock is 

 a step towards some adjustment or equilibrium and 

 that there is no reason for expecting shocks of in- 

 creasing seismicity in the future, it will be necessary 

 to present briefly some of the facts of the more recent 

 geologic history. 



It seems a curious statement to make in this en- 

 lightened age, but the little may herewith included as 

 Plate I, as poor as it is, is the first assemblage and 

 outline presentation of the chief physiographic fea- 

 tures of Southern California. 



