66 GUIDEBOOK OF THE WESTERN UNITED STATES. 
is a prominent feature west of Bond. (See sheet 12, p. 7 2.) Itis due 
to a dome-shaped uplift of the rocks which in the center exposes an 
extensive area of red beds and underlying limestones of Carboniferous 
age. The light-gray foothills are the outcrop of the upturned edges 
of the Dakota sandstone. 
For some distance south of milepost 730 the Greenhorn limestone 
is near the track, and finally, as it is crossed by the railway, it is exposed 
extensively in cuts, notably between mileposts 732 and 734. A short 
distance beyond milepost 734 the route descends from the flat ridge 
of the limestone into a broad area of lava (basalt). This lava came 
from the Maxson Crater, an irregular volcanic cone which is visible on 
the southeast slope of the Turkey Mountain uplift, 5 miles west of 
Optimo (op’tee-mo). The lava flowed down slopes of Dakota sand- 
stone, then across the broad flat which is now traversed by the railway 
from Optimo nearly to Shoe- 
maker, and finally down the 
canyon of Mora River nearly 
to its mouth, 20 miles to the 
southeast. The flow is mod- 
erately recent and exhibits a 
Morea River 
Se a hey ene Soi variety of features character- 
isa Tee a ee of thie later basalt flows. 
oh fre N. Mex., showing relations of na dew ten. pepe aunt ate 79 sess apres 
ing east. ‘The total depth of the canyon is about 700 feet. Plistered, and much of the 
rock is vesicular or spongy, 
with small cavities due to the escape of steam. 
In the broad valley south of Optimo the lava spread out widely, but 
in flowing down the deep canyon of Mora River it was narrowed to a 
: few hundred yards. It filled this canyon about half- 
aaa 3 way up its sides, but the river has since cut a narrow 
sseaatay Sr oe, mane: gorge into the lava sheet and in places through 
the lava into underlying rocks, as shown in figure 10. 
This lava-filled canyon begins 6 miles east of the railway, and its outer 
walls of sandstone are plainly visible from the vicinity of milepost 740. 
Halfway between mileposts 741 and 742 the southern margin of the 
lava sheet abuts against a cliff of Dakota sandstone which extends 
a northwestward. A short distance beyond this place, 
i. near Shoemaker, the bank of Mora River is reached, 
Kaneas Cite eet exiies, 2H the railway follows this stream along the north 
side of the deep canyon which it has cut in the Dakota 
sandstone and underlying beds. The beds lie nearly horizontal and 
in places the high cliffs of sandstone have at their bases the greenish- 
gray shale of the underlying Morrison formation. On the north side 
, of the track at milepost 748 the Dakota sandstone is extensively 
quarried for railway ballast. Two miles beyond there is, on the south 
Fiacver 10 Secti oA, D 
up t 4U 
iat cnel apie 
