6 RURAL CALIFORNIA 



logic yesterday, is written in more detail than else- 

 where in the world. It treats of marine, terrestrial 

 and glacial conditions : of the base-leveling of moun- 

 tain ranges followed by vulcanism, earth movements 

 and the re-birth of mountain systems." For what 

 is, therefore, rare in California of the uplift of 

 primeval rocks that have entered into the visible 

 structure of older parts of the continent, there is com- 

 pensation in the greater extent and variety of geo- 

 logic action in later periods which these older parts 

 have not so richly experienced, or, at least, of which 

 they do not present to the trained vision such clear 

 and complete record. 



^ons ago, in times which geologists call "ter- 

 tiary" because two great geologic epochs preceded 

 them (and furnished materials visible in the struc- 

 ture of the Atlantic side of the continent), there 

 arose from the primordial world-spread of waters on 

 what is now the Pacific Coast, ridges of earth-crust 

 lifting above the flood the sediments which had for 

 millions of years been collecting beneath it. These 

 ridges separated the waters on the east from those 

 on the west and created an ancient inland sea which 

 has been called the "Great Basin Sea," covering the 

 vast region lying west of the Rocky Mountains and 

 which was designated the "Great American Desert" 

 on the United States maps of more than half a cen- 

 tury ago. These first uplifts of the earth-crust were 

 not the mountain ranges of California as we now know 

 them but were in a way progenitors of them. Upon 

 their eastern sides lashed the waters of the Great 



