t 



Law?on. ] Post-Pliocene DiastropJiism. 1 1 7 



excited as to the probable extension of these strands along the 

 coast. In order to ascertain the general character of the coast with 

 a view to possible future investigations, a short trip was made from 

 San Francisco to San Diego by steamer, so that, by stopping over 

 at various points, opportunities were secured for an inspection of 

 the coastal topography. Other excursions were also subsequently 

 made by rail. The data obtained are the results of rapid reconnais- 

 sance methods. They are, however, of sufficient importance and 

 immediate interest in the judgment of the writer to warrant present 

 publication, notwithstanding the many gaps which could readily be 

 filled by more systematic inquiry. Even with these gaps, the infor- 

 mation here given establishes two general facts of no small moment 

 in certain discussions affecting the recent history of the continent. 

 These are : — 



1. The uplift or emerge'nce from the sea of the entire coast of 

 California from San Francisco to San Diego, in post-Pliocene time 

 to an extent of from 800 to 1,500 feet, a very notable epeirogenic 

 event. 



2. The local deformation or differential movement of the crust 

 to a very remarkable degree, particularly in the vicinity of Santa 

 Catalina Island and near the city of San Francisco, very notable 

 orogenic events, also of post-Pliocene age. 



THE SAN DIEGO MESA. 



Physiography. — The county of San Diego comprises portions of 

 three distinct physiographic provinces. These are: (1) The central 

 mountainous range of the Peninsular Sierra, (2) the Colorado Des- 

 ert on the east, and (3) the coastal slope on the west. This coastal 

 slope is a terraced plain which has a breadth, between the ocean 

 and the mountains, of from twelve to eighteen miles. It is locally 

 known, and commonly spoken of, as "the mesa," the term being 

 applied indiscriminately to the original plateau and to the terraces 

 which have been developed from it. This mesa has been examined 

 cursorily by the writer practically along the entire front of San 

 Diego County, and has been crossed on the line of the San Diego, 

 Cuyamaca and Eastern Railway, and on the branch line of the 



