11. T. HILL — THE TEXAS-NEW MEXICAN REGION. 99 



It also caps the Eagle mountains and vast areas to the southward as- far as Las Mora 

 creek. The source of this basalt is undetermined, but it is supposed to have flowed 

 from fissures and not from craters in early Tertiary time. At a lower altitude and 

 apparently of later age, along the eastern border of this ancient basaltic flow, at its 

 contact with the Llano Estacado formation, and in the vicinity of Folsom, there is a 

 group of volcanic craters, composed of cinder cones of from 100 to 2,750 feet in height 

 above the plain, from which have been extruded vast sheets of lava and basalt, 

 covering tlie country for miles around and extending more or less irregularly from 

 Folsom to Rabbit Ear mountains near the Texas line, 100 miles distant and north 

 and s< iiith of the road about 50 miles, partially covering an area of 1,000 square miles. 

 The most conspicuous of these craters is Mount Capulin, six miles south of Folsom 

 station. This, a beautiful cinder cone (altitude, 9,000 feet), rises nearly 2,750 feet 

 above the railroad, with a vast crater at its top nearly a mile in diameter, slightly 

 broken down on its western side. From its summit many flows can be tract s< 1 .* To 

 the southward from six to twenty miles there are several similar craters, while to 

 the northward there are several smaller ones, called montcules by the Mexicans. 

 Around these craters there are numerous flows of vesicular, ropy lava. 



These are the easternmost known craters of the Rocky mountain region, and 

 their occurrence at the contact of the Llano Estacado shore line (or depi >sition level) 

 and the Raton plateau is interesting. The cinder cones are clearly of a more recent 

 origin than the adjacent basaltic cap of the Raton plateau, for they are situated in 

 an eroded valley between the main mesa and an outlier — the Sierra Grande — and 

 at a lower altitude than either of them. They are also apparently more recent 

 than the late Tertiary deposits of the Llano Estacado, the original surface of the 

 lava resting upon the latter and not covered by it except in case of the wind-blown 

 debris. 



For two hundred miles southward no more of these craters are encountered until 

 we reach the head of the Hueco-Organ basin, between the San Andreas and 

 Guadalupe mountains, on the stage road from Socorro to Fort Stanton. Here 

 again there is a great area of "malpais" lava, which is a terror to the traveler and 

 a barrier to the development of the country which it covers. f 



The northern end of the floor of the Mesilla basin is covered by another lava 

 flow, through which the railroad cuts at Fort Seldom Picocho peak and several 

 others, some ten miles west of Mesilla, are volcanic cones. Of these Dr. G. <i. 

 Shumardsays: "From the character and general appearance of these cones and 

 lava streams I am disposed to ascribe their origin to a comparatively recent geo- 

 logical period. They form part of an extensive volcanic chain, which may be 

 traced north and south Cur several hundred miles.'' 



The northern end of the Jornado del Muerto basin also is occupied by a great 

 lava sheet, 12 by 8 miles in area, or 96 square miles. This, too, is alleged to have 

 come from a crater, about 10 miles east of t he road, and bears the same intimate 

 relations to the basin floor as the other crater Hows mentioned. 



Another crater How upon the floor of the basin is about 30 miles northwest *<( El 

 Paso, bet ween A ft en and Aden stations, w here there is an alleged coneof great mag- 



*A brief notice of M t Capulin was published b} Ovestes St. John in " Notes on the Geologj ol 



Northwestern New Mexico": Bull. U. S. Geol. and Geog. Survey of tho Territories, vol. ii, 1876. 

 ; Since this paper wa9 begun Mr. Ralph S. Tarr has published n brief description of this Bow 



i \ ricn ii \ al ist, June, 1891). 



