CHAPTER: V, 
GENERAL VIEW OF THE STRUCTURE OF THE GREAT CENTRAL PLATEAU, 
COMMON GEOLOGICAL CHARACTER OF ALL THE COUNTRY BETWEEN THE MISSISSIPPI AND COLORADO —SoOURCE AND COURSE OF*THE UPPER 
ADO.—TABLE-LANDS BETWEEN ROCKY MOUNTAINS AND CERBATS.—GREAT CANON.—GEOLOGICAL ELEMENTS OF ITS SECTION.— 
BaSIN OF THE LITTLE COLORADO —ITS OUTLINES AND STRUCTURE.—ANCIENT GRANITIC BARRIERS WHICH LIMIT IT.—HIGH MESA ABOUT 
SAN FRANCISCO MOUNTAIN —V ALLEY OF THE LITTLE COLORADO.—STRUCTURE OF MESA BOUNDING IT ON THE NORTH AND EAST.— 
CRETACEOUS MESA OF THE MOQUIS VILLAGES.—GREAT WHITE MESA RESTING ON THE LAST.—SNOWY MESA BORDERING THE COLORADO.— 
ORIGIN OF THE PECULIAR TOPOGRAPHY OF THE TABLE-LANDS.—REFERRED TO A VAST SYSTEM OF EROSION.—ALL THE CANONS OF 
WESTERN NEW MEXICO DUE TO AQUEOUS ACTION.—MESA WALLS, BOUNDARIES OF BROAD VALLEYS OF EROSION.—AREA AND LIMITS OF 
THE PAL0ZOIC CONTINENT.— SOURCES OF THE SEDIMENTS FORMING THE STRATA OF THE TABLE-LANDS AND CONDITIONS OF THEIR 
DEPOSITION.—OUTLINES OF NORTH AMERICAN CONTINENT APPROXIMATELY DEFINED IN THE EARLIEST PALAOZO1C AGES 
The geology of the country traversed by our party east of the great bend of the Colorado 
may be conveniently considered in several distinct sections, as there are embraced in this vast 
region a number of well-marked geographical districts, of which the geological features are, in 
some respects, peculiar, and are not repeated. And yet these different districts form but parts 
of the great central plateau of the continent, and the relations which the structure of each 
part sustains to that of the other portions of the geological arch—if I may use the simile— 
which spans the interval between the lower Colorado and the Mississippi are such, that it is 
quite as important it should be studied as a part of a great whole as in its local and minor 
details. 
I shall take the liberty, therefore, of anticipating in some degree my geological narrative, 
and give very briefly here, as the most convenient and appropriate place, the results of a line 
of observation carried quite across this great plateau, of which the geological structure is so 
clearly revealed in the magnificent sections of the banks of the Colorado, not very far distant 
from the point we had reached at the close of the last chapter. 
The Colorado rises in a thousand sources, at an elevation of from ten to twelve thousand feet 
above the sea, on the western side of the Rocky mountains. Descending from their fountain- 
heads its tributaries fall upon a high plateau of sedimentary rocks, which forms the western 
base of these mountains and occupies all the interval between them and the great bend of the 
Colorado, where the river enters the volcanic district already described. From that point its 
course trends northeasterly into Utah, where its outline has not been traced. Southward it 
follows the trend of the Black and Cerbat#mountains, which bound it on the southwest, and 
extends far into Mexico. In the intervals between the ranges of the Rocky mountain system 
portions of the same ‘‘mesa’’ are seen, often much disturbed, and flanking the axes of the 
comparatively modern lines of elevation. 
ast of the mountains it still continues, forming the high prairies which everywhere skirt 
their bases. Cut into somewhat detached plateaus by the streams flowing from the mountains, 
a belt of country in that region has been designated by the name of the ‘‘ high table-lands ;”’ 
but there is no well-defined geographical area to which that name is strictly applicable, as the 
most remarkable unity, both of topographical and geological structure, prevails over the entire 
area of the ‘ plains, ’? which reach from the mountains to the Mississippi.. The geological 
elements which compose the great table-lands of the Colorado here reappear, exhibiting the 
same harmonious stratification. The strata all dip very greatly eastward, and form the western. 
slope of the great Mississippi valley. 
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