MINDELEFF NATURAL FEATURES OF THE REGION 83 
into it, traces of lesser disturbances can be found throughout the 
country. It has been said that if a geologist should actually make 
the circuit of the plateau country, he could so conduet his route that 
for three-fourths of the time he would be treading upon volcanic mate- 
rials and could pitch his camp upon them every night. The oldest 
eruptions do not go back of Tertiary time, while some are so recent 
as probably to come within the historic period—within three or four 
centuries. 
The strata of the plateau country are remarkable for their homo- 
geneity, when considered with reference to their horizontal extensions; 
hardly less so for their diversity when considered in their vertical 
relation. Although the groups differ radically from each other, still 
each preserves its characteristics with singularly slight degrees of 
variation from place to place. Hence we have a certain amount of 
similarity and monotony in the landscape which is aided rather than 
diminished by the vegetation; for the vegetation, like the human oceu- 
pants of this country, has come under its overpowering influence. The 
characteristic landscape consists of a wide expanse of featureless plains, 
bounded by far-off cliffs in gorgeous colors; in the foreground a soil of 
bright yellow or ashy gray; over all the most brilliant sunlight, while 
the distant features are softened by a blue haze. 
The most conspicuous formation of the whole region is a massive 
bright-red sandstone out of which have been carved ‘the most striking 
and typical features of those marvelous plateau landscapes which will 
be subjects of wonder and delight to all coming generations of men. 
The most superb canyons of the neighboring region, the Canyon de 
Chelly and the Del Muerto, the lofty pinnacles and towers of the San 
Juan country, the finest walls in the great upper chasms of the Colo- 
rado, are the vertical edges of this red sandstone.” 
Of the climate of the plateau country it has been said that in the 
large valleys it is “temperate in winter and insufferable in summer; 
higher up the summers are temperate and the winters barely suffer- 
able.” It is as though there were two distinct regions covering the 
same area, for there are marked differences throughout, except in topo- 
graphic configuration, between the lowlands and the uplands or high 
plateaus. The lowlands present an appearance which is barren and 
desolate in the extreme, although the soil is fertile and under irrigation 
yields good crops. Vegetation is limited to a scanty growth of grass 
during a small part of the year, with small areas here and there 
scantily covered by the prickly greasewood and at intervals by clumps 
of sagebrush; but even these prefer a higher level, and develop better 
on the neighboring mesas than in the valleys proper. The arborescent 
growth consists of sparsely distributed cottonwoods and willows, 
closely confined to the river bottoms. On intermediate higher levels 
junipers and cedars appear, often standing so closely together as to 
seriously impede travel, but they are confined to the tops of mesas and 
