144 GUIDEBOOK OF THE WESTERN UNITED STATES. 
The soft Tertiary and Cretaceous formations have been eroded 
very rapidly, and vast quantities of clay, gravel, and sand have been 
washed into the basin-like valley below the narrow canyon which 
the river has cut through the Grand Hogback. This loose material 
ence filled the valley to a considerable depth, and the streams then 
removed part of it, leaving the remainder as great sloping terraces, 
which come down from the sides of the valley and would meet in 
the middle were it not for the trench which the river has cut. The 
presence of this fine material has given to one of 
Silt. the villages the appropriate name of Silt. On the 
aca — feet. old maps of this region this broad valley was called 
Denver 380 miles, | Cactus Valley, on account of the barrenness of the 
region and the presence of many forms of cacti. To- 
day the parts on which water has been taken bear little resem- 
blance to a cactus valley, but the unreclaimed part is extremely 
barren. Here for the first time on this journey the traveler is coming 
into the real semiarid region, where precipitation is so slight that 
crops can not be raised without irrigation and where the unreclaimed 
tracts are either barren of vegetation or have the kind that is char- 
acteristic of the more nearly desert regions. On the south (left) 
the traveler may see the east front of Battlement Mesa, which is 
capped by a layer of basalt that has preserved the even surface over 
which it flowed as lava. Its east front, which is seamed and scarred, 
presenting a very rugged face, is one of the highest points in the 
vicinity, having an altitude of over 10,000 feet. The even surface 
upon which this flood of lava was poured is probably a part of the 
peneplain of which the White River Plateau is another remnant. 
Those who have made no study of geology may think that all pla- 
teaus are formed by the uplift of parts of the country to a greater 
altitude than that of the surrounding regions—in other words, that 
they are on anticlines or upfolds of the rocks, but this is not uni- 
formly true. The White River Plateau is on such an upfold, but 
Battlement Mesa is in a downfold, and generally upfolds and down- 
folds have no necessary connection with the formation and preser- 
vation of plateaus. 
Rifle, on Colorado River at the mouth of Rifle Creek, although not a 
large town, is one of the most important points on the railroad. 
The irrigated land along the river near Rifle yields 
Rifle. abundant crops, but they are somewhat different 
te re — feet. from those that are raised about Glenwood Springs, 
Denver 387 mites, 10 the land here stands at a lower altitude and the 
summer temperature is consequently higher. Po- 
tatoes and grains are not large crops about Rifle ; sugar beets, alfalfa, 
and fruits are more common. From Rifle a stage line, 42 miles long, 
leads northward to Meeker, the largest town in the irrigated valley 
