106 SOUTHERN CALIFORNIA GEOLOGY 



movements are as trivial as are slight settlings of the 

 ensemble of a majestic building. 



THE STRUCTURE PROVINCES 

 The southwestern part of our country may be di- 

 vided into certain, well-defined, natural provinces ac- 

 cording to the directional types of structure which pre- 

 vail in them. 



It is not desirable at this place or moment to give 

 details of all these great structural provinces of the 

 southwest, otherwise than those portions of them 

 which lie within the state of California. Descriptions 

 of the regions to the east are contained in a manuscript 

 I have prepared upon the Trans-Pecos Region. 



STRUCTURE PATTERN OF SOUTHERN 

 CALIFORNIA 



It is difficult to convey a word concept of the struc- 

 ture pattern of Southern California, although, as com- 

 pared to some other regions, the structure is conspic- 

 uously reflected in the physiography. Much is begin- 

 ning to be known about it, but more is still to be 

 learned. Hence it must be understood that the fol- 

 lowing remarks, although based upon many years of 

 individual observation, are only an endeavor to give 

 an elementary concept of a very complex subject. 



The highlands of Southern California may again be 

 classified into two categories according to the simplic- 

 ity or complexity of their geologic structures as re- 

 flected in their physiography. 



The first of these is of the simple type, and usually 

 consists of narrow, elongated folds or faulted blocks. 

 The second type consists of irregularly shaped plat- 

 eaux, usually more or less oblong and polygonal in out- 



