The whole region has been subjected to many displacements, both flexures of the monoclinal type and faults. Some of these flexures attain a length of over 80 miles and a displacement of 3,000 feet, and the faults reach even a greater magnitude. There is also an abundance of volcanic rocks and extinct volcanoes, and while the principal eruptions have occurred about the borders of the region, extending but slightly 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 conduct his route that for three-fourths of the time he would be treading upon volcanic materials 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 homogeneity, 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 occupants 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 Colorado, are the vertical edges of this red sandstone."