EXTINCT VOLCANOES OF NORTHEAST NEW MEXICO 361 



CAPULIN MOUNTAIN AS SKlvN 1<RUM THE PLAIN BELOW IT. 



Folsom, New Mexico, about 30 miles 

 southeast of Raton. Until recently it 

 has been readily accessible only from 

 Folsom, a small town on the Colorado 

 and Southern Railway, but recently a 

 railroad has been constructed from 

 Raton eastward which passes within 

 three miles of the summit. The moun- 

 tain has an altitude of about 8,000 feet 

 or about 1,500 feet above the general 

 level of the plain on which it stands. 

 There is a broad platform at its base 

 built up by successive flows of lava, 

 and on this platform rests a steep- 

 sided crater cone nearly circular in 

 outline and probably a mile and a half 

 in diameter at the base, having a well- 

 defined crater at its summit. The bot- 

 tom of the crater is about 75 feet lower 

 than the lowest part of the rim and 

 about 275 feet lower than the highest 

 part. Its diameter from rim to rim 

 was estimated at 1,500 feet. 



The lava platform on which the cone 

 stands is composed of scoriaceous, 

 ropy lava evidently extruded from 

 Capulin in the early stages of its vol- 



canic activity, in successive flows sep- 

 arated by considerable periods of time. 

 Some of the older lavas where they 

 were not covered by more recent ones 

 have decomposed at the surface form- 

 ing a thin layer of soil in which grass 

 and shrubs have taken root. Some of 

 the younger flows have all the ear- 

 marks of recent origin. They are very 

 slightly decomposed, are scoriaceous 

 and ropy, and have fractured crust, 

 cavernous openings, blister cones, etc. 

 In short, they form typical "mal pais." 

 The appearance of the nearly vertical 

 faces of some of the more recent flows 

 suggests a rapidly advancing tidal wave 

 frozen in transit. As the surface of 

 the molten rock cooled the solid crust 

 at the advancing front was fractured 

 and rolled under, and when the whole 

 mass ceased to move this rolling front 

 stopped in the position seen at the pres- 

 ent time. In some places where the 

 nearly vertical front is 25 to 30 feet 

 high, scarcely a block has fallen from 

 it, so recently was it formed. 



