dotkw.] DIVISIONS OF THE GRAND CANON. 71 



gram. (PJ. X11J.) Immediately south of the Paria Plateau extends the 

 Marble Canon, with a south westward course. Directly across the re- 

 maining four plateaus winds the Grand Canon of the Colorado. South 

 of tlu' river is a vast expanse of nearly flat surface, but little diversified, 

 called the Colorado Plateau. Upon its southern borders rise abruptly 

 a group of great volcanic piles called the San Francisco Mountains, the 

 largest or dominant cone being of an impressive order of magnitude. 

 There are still other portions beyond, but the entire region south of the 

 Colorado has been reconnoitered rather than surveyed; and though we 

 have a general knowledge of pretty nearly the whole of it, our knowl- 

 edge of details is not as yet precise. 



The entire expanse of the Grand Canon platform within the terraces 

 consists of a flat surface, interrupted at wide intervals by cliffs or sharp 

 flexures produced by the great displacements which traverse the land in 

 a prevailing north to south direction.* On the whole, it is a smooth 

 country in comparison with the other districts of the Plateau Province. 

 It is not dissected or honeycombed by the ramifications of innumerable 

 side gorges, as is the case with most of the other districts, for the Grand 

 Canon has on the north side only one lateral or tributary canon of any 

 considerable length, and this tributary has but few branches. In truth, 

 one of its remarkable features is the paucity of lateral chasms. The 

 southern side is not more diversified than the northern, and I think we 

 may say that it is somewhat less so. Between the great cliffs of dis- 

 placement and between the foot of the terraces and the brink of the 

 chasm the country is not more uneven than the Great Plains of Western 

 Nebraska and Kansas, and not much more so than Indiana and Illinois. 

 But the traveler is seldom out of sight of the palisades reared at the 

 fault-lines, or of the gigantic and gorgeously colored walls which bound 

 the terraces of the High Plateaus. 



The Grand Canon will be described at some length in subsequent 

 chapters, llere will be noted only those more general features which 

 may be made to appear on the map. It crosses transversely the four 

 western plateaus of the district, while the Marble Canon traverses the 

 eastern or fifth plateau. The two canons are only nominally separated, 

 for there is no jrap between them. The Marble Canon begins at the 

 base of the eastern terraces. The Colorado River, after traversing the 

 central mesas of the Plateau country in a series of profound chasms, at 

 length emerges from the Echo Cliffs of Triassic and Permian age. Here 

 for an instant the river is in comparatively open country. But within 

 a mile or two it begins to sink another chasm in the Carboniferous 

 rocks, and in the course of Co miles the depth steadily increases until 

 it becomes about 3,500 to 4,000 feet. This is the Marble Canon. It is 



*It will be noted here that (litis may he produced (1) hy faults lifting the country 

 on one side of the fault-line or depressing it on the other; (2) hy the denudation of 

 the strata in front ofthecliff. The former are called Clijficf Displacement; the latter, 

 Cliff* of Erosion. 



