100 PROCEEDINGS OF WASHINGTON MEETING. 



nitude, from which a narrow stream of lava flows southeastward about 20 miles. 

 There are other areas in western Xew Mexico of volcanic lava, notably that south 

 of Grand station, on the Atlantic and Pacific railway. 



In Trans-Pecos Texas no craters have been noted, although they may occur in 

 the mountainous regions. Many old volcanic pipes or necks without lava flows 

 occur between Austin and Del Kio, but they are of entirely different type and age 

 from those of Xew Mexico. The relation of those cinder cones and suit-recent flows 

 to those of northwestern Xew .Mexico and Arizona cannot be stated from personal 

 observation. 



Proceeding south west ward into Mexico they still continue, and in cases exhibit 

 evidences of activity, increasing southward toward the neck of Mexico where the 

 present epoch seems to represent but a southern continuation of the volcanic and 

 lacustral conditions which so recently prevailed over the northern portion of the 

 basin region. 



The fact that these cinder cones and lava flows occur in the floor of the Quater- 

 nary lake basins is indicative of their recent origin. It is possible that future 

 investigations will show an intimate connection between the drying up of the 

 basins and the activity of these volcanoes. 



It is also evident from the investigations that eruptive activity lias occurred in 

 the Texas-Xew Mexican region from Cretaceous to the present time, and at least 

 three well-defined epochs are at present recognizable which may serve as a guide 

 to future observations, viz : 



1. The Austin-Del Rio system, or Shumard knobs; ancient volcanic necks or 

 laccolites bordering the Rio Grande embayment, begun in later Cretaceous time. 

 the lava sheets of which have been obliterated by erosion. 



2. The lava flows of the Raton system, which are fissure eruptions of Tertiary 

 time, and which are only partially removed by erosion. 



3. The cinder cones and lava flows of the Capulin system, which are late Pleisto- 

 cene and which still maintain their original slope and extent. 



The most valuable evidence of the recent origin of the craters in addition to their 

 location in the post-Tertiary valleys is their perfect shape and preservation from 

 the great erosion from which all of the older and more consolidated features of the 

 country have suffered greatly. To one acquainted with the active erosion of this 

 region, by both cloudbursts and wind, the preservation of an unconsolidated and 

 fragile structure like the Xew Mexican cinder cones is the most convincing evi- 

 dence of newness. 



The foregoing features are presented without any attempt at broad correllation 

 with the coastal or other regions of the United states, although they present a 

 tempting field therefor. For the present, however, I prefer to leave this task to 

 others, boping that the remarkable Tertiary and Pleistocene history will receive 

 that attention which it deserves. 



