THE GEOLOGY OF MEXICO.^ 



IT is an encouraging sign of the times that the RepubHc 

 of Mexico has recently esta Wished a geological survey; 

 and it is still further matter for congratulation that the survey 

 has already proceeded so far that it has been able to issue a 

 sketch of the geology of the country as a whole. The 

 sketch, no doubt, will require considerable alteration in the 

 future ; and, indeed, it is apparent upon the face of it that 

 the palaeontological evidence has not yet been sufficiently 

 examined. But there is no reason to doubt its general 

 accuracy, and it gives a very good idea of the geological 

 structure of the Republic. 



In a broad and general way the geology of Mexico 

 offers some resemblance to that of the Peninsula of India. 

 There is the same almost entire absence of fossiliferous 

 Palaeozoic rocks. The Trias contains little but plants, and 

 the Jurassic is very feebly developed. At the close of the 

 Cretaceous period there began a great series of volcanic 

 eruptions, comparable with the Deccan Trap ; but in 

 Mexico these eruptions have continued down to the 

 present day. In Mexico, too, the marine Cretaceous is 

 much more extensively developed than in India. 



Geographically, Mexico consists of a great central table- 

 land, inclined towards the north and north-east, and in- 

 cluded between two chains of mountains (the Sierra Madre 

 del Pacifico and the Sierra Madre Oriental), which are 

 separated from the sea by narrow strips of low-lying country. 

 In the southern part of the republic the two chains unite 

 with each other in the form of a V, near the apex of which 

 are situated the great volcanoes of Popocatepetl, Ixtaccihuatl, 

 Orizaba, etc. 



South of the V, the country is lower, with a range of 

 mountains parallel to the Pacific coast. 



^Jose G. Aguilera. " Sinopsis de geologia Mexicana. Bosquejo 

 geoldgico de Mexico : segunda parte." BoL del Itist. Geol. de Mexico. 

 Nums. 4, 5, y 6, pp. 189-270. One map. Mexico, 1897. 



