DENVER & RIO GRANDE WESTERN ROUTE. 171 
down of the granite has made the surface of the land adjacent to 
the tops of most of the narrow canyons flat—in other words, the 
streams have cut trenches in mesas or plateaus. 
In the Gunnison Valley another chapter has been written as an 
episode in the geologic history of the general region—a chapter re- 
cording events of a time, after the sedimentary rocks had been de- 
posited, when the region was covered with lava flows or with material 
derived from them or from volcanic eruptions. 
From the summary of the geologic history of the region just given 
the scenery below the town of Gunnison, even including that in the 
Black Canyon, may be more readily interpreted. The country for a 
few miles below the station at Gunnison must have been at some time 
long past flooded with lava. The volcanic rocks thus formed are now 
generally soft, but in places, as on the upland southwest of the station, 
they rise above the general level in great monuments or spires, making 
a very rough country. (See Pl. LXX, 2.) The character of the vol- 
canic rock—a breccia—which composes much of the surface where the 
slopes are smooth, may be seen in the cut at milepost 290. 
Wherever the granite appears above the level of the streams they 
have cut into it narrow canyons, above which the slopes may be very 
gentle up to some horizontal bed of sandstone, which generally stands 
out asa mesacap. Where the slopes are gentle and the valley is broad 
hay fields abound, but where the valley narrows down to a canyon the 
bottom can not be cultivated. 
The first large canyon below Gunnison begins at a siding called 
Hierro (yay’rro; Denver 294.5 miles), where the top of the granite 
stands at track level. The top of the granite rises downstream, and 
within a short distance below the siding the train passes through a 
pretty little winding canyon, whose granite walls range in height 
from 100 to 150 feet. The scenery in this canyon is not grand and 
striking, like that in the Black Canyon, farther down, but many 
beautiful views may be obtained of the clear, sparkling river, the 
fringe of willows and cottonwoods, and the gray canyon walls. The 
canyon ends at Elkhorn (Denver 297 miles), a resort devoted entirely 
to the followers of Izaak Walton. Below this place the canyon widens 
out, the granite decreases in height above the stream, and the slopes 
above the granite include horizontal beds of sand- 
Jola. stone, so that they are made up of a number of 
~ satcralipepg may mesas or terraces. Hay ranches abound in the 
Denver 299 miles, | broad valley, and opposite the village of Iola even 
the terrace formed by the granite about 50 feet 
above the bottom of the valley has been irrigated and yields flourish- 
ing crops. 
A mile and a half below Iola another granite canyon begins, and 
in a short distance its walls rise to a height of about 150 feet. From 
