164 GUIDEBOOK OF THE WESTERN UNITED STATES 
west of that place. Several large fresh-looking cinder cones are 
plainly visible not far north of the railroad. West of the lava fields 
there are knobs of igneous rocks on both sides of the track, but they 
are mostly of the older period of eruption. 
At intervals during Tertiary and Quaternary time there was great 
volcanic activity in many parts of the West, and in southwestern New 
Mexico large areas were covered by lavasin both periods. At numer- 
ous vents the outflow of lava was followed by an outburst of cinders 
and ash, which were thrown into the air and, settling back about the 
vent, formed a cone, generally having a central crater. The building 
of these cinder cones therefore usually marked the last stage of ac- 
tivity of the voleano, but in some places a later gush of lava issued 
from the side or base of the cone. The lava contained a vast volume 
of steam, for much of it is highly porous, or vesicular, owing to the 
expansion of the steam in the lava as it spread over the surface. The 
cinder consists of lava filled with small steam holes, so that most of 
it is completely porous or ‘‘pumiceous.” In the cinder of the cones 
are usually embedded masses of compact lava, probably thrown out 
as bombs. These vary in form from balls to elongated and irregular 
shapes, mostly with smooth surfaces, such as might be expected in 
molten material ejected from a vent. In places there are flattened 
masses of lava several yards in extent, in part twisted around some of 
the cinders in which they are inclosed. 
On approaching Arena siding (turn to sheet 19) the railroad 
descends nearly 200 feet into a wide, smooth-surfaced basin, or desert, 
which extends to Columbus and beyond. It slopes southward into 
Mexico and is occupied by Palomas Arroyo, a dry wash which is 
crossed 2 miles east of Columbus. This arroyo leads south into 
Palomas Lake, in Mexico, a water body due to springs known as Ojo 
de las Adjuntas (o’ho day las ad-hoon’tas), which come up in the 
valley bottom about 2 miles south of the international boundary. 
: umbus is a commercial center for agricultural and stock interests 
in the southern part of Luna County. <A considerable area in the 
ee ae Palomas Valley north of Columbus is irrigated from 
Elevation 405 fet. wells which draw water from a widespread underflow 
Poguiation 9 contained in the gravel and sand that underlie the 
a» 1282 desert plain. Columbus is on a main road from 
Mexico and has a custom house and at times has had 
_ an encampment of United States troops. It was the scene of a 
o — rary by the Mexican outlaw Pancho Villa in 1915 “_ has 
‘itnessed many border episodes of greater or less importanc 
oe “ont 20 miles north of Columbus are the Florida Mountains, the 
a south end of which is plainly visible. This range is described on 
se 139, To the northwest are the Tres Hermanas Mountains 
ee ‘nas, a for three sisters), named from the three 
/ conical in the north end. main feature of this 
