86 WARREN N. THAYER 



Figures are totally inadequate to express the amount of this 

 extrusive material. Even using the largest familiar units of 

 volume they would run into orders which no mind is capable of 

 comprehending. There are a half-dozen or more peaks rising from 

 5,000 to 10,000 feet above the plateau, and these are but stubs of 

 former peaks which have been reduced by erosion. 1 A few of these 

 are worthy of particular mention. 



Orizaba, the ''shining star" or " Citlaltepetl 1 ' of the Aztecs, is 

 a majestic cone which rises from the eastern edge of the plateau 

 to a height of 18,240 feet above the sea, and is visible 80 miles out 

 from the coast. 2 Popocatepetl, the "smoking mountain," is built 

 upon the plateau just south of Mexico City. It rises 17,520 feet 

 above the sea and has a crater half a mile in depth and of the same 

 diameter, from which steam and sulphur gases escape continually, 

 proclaiming it not extinct, but dormant. Ixtaccihuatl, "the 

 woman in white," raises its cone just east of Popocatepetl and to a 

 height of 15,082 feet; and Toluca, called in the Aztec tongue Xin- 

 antecatl, and supposed to mean the "nude man," is situated just 

 west of Popocatepetl and rises to a height of 13,000 feet. 3 The 

 Cofre de Perote, or "Nahucampatepetl," to the north of Orizaba, 

 rises to a height of 13,411 feet. Volcano Jorullo in Michoacan 

 belongs to the third era of eruption, which will be discussed under 

 the head of physiographic history, and although not situated on the 

 plateau is a sort of "outlier" of this province. It rises from an 

 amphitheater almost 3,000 feet below the level of the plateau. 4 

 Colima, on the western edge of the plateau, shows an altitude of 

 12,664 feet, while numerous other cones, somewhat lower, though 

 scarcely less imposing, dot the plateau in many places. Most of 

 the cones are of the " strato-volcanic " type and show plainly the 

 several flows of which they were built. 5 



The volcanoes of Colima, Popocatapetl, and Orizaba are unique 

 in that they consist of twin peaks, one with a crater and the other 



1 Hill, Eng. and Mitt. Jour., LXXXV, 6S1-88. 



2 Melgareo, Natl. Geog. Mag., XXI, 741. 3 Melgareo, loc. cit. 



A Ordonez, Guides des excursions, 10th Inter. Geol. Cong. Mex., igo6, No. 9. 

 5 Hovey, Science, N.S., XXV, 764; T. Flores, Guides des excursions, 10th Inter. 

 Geol. Cong. Mex., 1906, No. 9, p. 14. 



