THE PHYSIOGRAPHY OF MEXICO 



63 



regarded as a single chain or mountain mass, but rather a group of 

 chains, generally of the same orientation, successively rising, one 



Fig. 1. — Physiographic Provinces of Mexico 

 Sierra Madre Occidental. 



Anahuac Desert Plateau. 5- Volcanic. 



Sonoran Desert. 6. Sierra del Sur. 



Gulf Coastal Plain. 7- Tehuantepecan. 



above the other, from west to east, separated by depressions, of vari- 

 ous widths and furrowed by streams of more or less importance." 1 

 1 E. Ordonez, Inst. Geol, Mex., IV. 



