PHYSICAL GEOGRAPHY 67 



the Colorado Plateau, the Rio Grande Ranges and the 

 Great Plains Regions, and still farther eastward as the 

 great synclinal troughs of the Rio Grande Embayment 

 and the Gulf of Mexico. Its last eastward recognizable 

 appearance is as the great fault escarpment north of 

 Porto Rico and the Virgin Islands. 



This belt separates the southern parts of Texas, New 

 Mexico, Arizona, and California and all of the Mexican 

 border region on the south from the northern parts 

 of the states named, and divides California into two 

 entirely different worlds. In fact it is the boundary 

 line between Neo-Tropical and Temperate North 

 America. 



The transcontinental Southern Pacific railway sys- 

 tem from Los Angeles to Galveston practically follows 

 the northern end of the sub-tropical region, while the 

 nearly-parallel Santa Fe system follows the southern 

 border of the different regions to the north. 



The chief features of the Transverse Belt in Cali- 

 fornia are its structural lines — gigantic, elongated, 

 east-west extending master faults and some folds, the 

 former of which are mostly omitted from Dr. Willis's 

 consideration and from his earthquake map published 

 by the Seismological Society. In general, this hitherto 

 but little appreciated lineament plays a wide and funda- 

 mental part in dividing California as well as North 

 America into its Northern and Southern parts. The 

 failure to appreciate the existence of these features 

 and the accompanying geographic conditions has been 

 the cause of a great confusion of knowledge. 



Further comments on the mountains, valleys and 

 faults of this lineament in California are more fully 

 described under the head of Southern California. 



