2 EE eo 
90 GUIDEBOOK OF THE WESTERN UNITED STATES. 
Here and there in the rocky cliffs and canyons are the present and 
former communal homes of aboriginal peoples, whose arts and reli- 
gious ceremonials partly lift the veil of the past and reveal glimpses 
of earlier stages of human culture. These vast expanses were long 
ago the abode of aboriginal tribes; later they were explored and 
dominated by the mounted Spanish conquistadores; and finally they 
have been made accessible to all by the comfortable railway of to-day. 
The plateau country and its approaches, in all their aspects—geologic, 
ethnologic, and historical—form a region which will hold the atten- 
tion of all passers-by in whom there exists a spark of appreciation of 
striking natural phenomena and significant human events. 
A short distance beyond Isleta the main line of the Santa Fe begins 
its climb out of the valley of the Rio Grande, ascending by a rather 
steep grade to the mesa which lies west of the river 
flat. The crest of this mesa is reached at Sandia 
siding.'’ In the cuts on this ascent there are many 
exposures of sands and loams (Santa Fe marl) which 
are capped by sheets of lava and volcanic cones on both sides of the 
track. The railway reaches the edge of the lava sheet a short dis- 
tance beyond milepost 16 and passes over it for 2 miles or more. 
There is a group of volcanic cones 2 miles west and another group to 
the northwest of milepost 21. From these cones small flows of lava 
spread over areas of moderate extent at a time not very remote 
geologically, when the river valley was about 200 feet less deep than 
at present. 
Sandia. 
Elevation 5,286 feet. 
Kansas City 941 miles. 
From the top of the mesa just beyond Sandia siding there are 
extensive views in every direction. About 15 miles to the east may 
* This place should not be confounded sheets of the various sed 
with the ancient pueblo of Sandia, which | lying nearly horizontal or presenting very 
lies 12 miles north of Albuquerque. wide dip sl 
* The region west of the Rio Grande, 
well known to geologists as ‘‘ the Plateau | with steep fronts and relatively level or 
country,” is a province which differs in | smooth tops. The harder formati 
its geography and geologic structure from stitute the surface of the plateaus; the 
th : ; softer beds crop out in the slopes. 
of tt ince are Many mesas or portions of these pla- 
450 miles, its western margin being far to | teaus cut apart from the main area by 
i erosion. 
: Spr The rocks are sandstones, limestones, 
: surfaces or plateaus consisting of great | and shales of Cambrian to earlier Tertiary 
