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Show 192 EXPLORA'£10N Oli' 1.'BE OANONS Oli' TilE OOLORADO. 76 is a cross section, intended to represent the structure of these interesting cliffs. In some places, the erosion of the western escarpment has been carried back further than tho line of displacement; in other places, not quite up to it. But wherever the line of erosion has been brought up to the line of displacement, or near it, we find the rocks standing in sharp crags. I have heretofore explained tha.t one of the conditions essential to the cliff structure is that the beds of the summit must be comparatively hard, and the beds below, at the foot of the cliffs, very soft; and this condition is well illustrated in these cliffs. Now the lower beds are turned down, by the monoclinal fold, below the reach of the waters employed in degradation, as you pass across the fold from west to east, and hence th~se cliffs cannot be carried farther to the eas~, by the progress of undermining, as long as the present conditions exist; and now the agency of erosion can only be exerted in obliterating the ridge. For this reason the ridge disappears in those places along its line where the undermining erosion from the west has progrossed the farthest. On tho we:::;torn side of the Paria Plateau there is an escarpment, facing the west, due to erosion, and the line of tho escarpment, on its northern end, coincides with tho line of flexure of the Eastern Kaibab Fault. Here, again, wo have a line of crags or peaks, forming an irregular ridge, like that in the Echo Oli1fs; but this stand::; on the brink of a well defined plateau, and is higher tllan the g·eneral surface of tho table. The crags and peaks are carved from the upturned edges of the beds. '"rhe slope due to displacemont i:::; soen farther to the west, and is tho slope of the Kaibab Plateau, and faces the escarpment. Only a small portion of this slope is seen in the edge of the plateau, where stands tbe line of crags. The softer beds at the bottom, which constitute one of the conditions on which the escarpment depends, are still exposed to the action of rains and streams, and the cliff condition is not terminated, as in the section previously given, and future erosion will carry this line of clilfs hack to tho east, as long as the present conditions are preserved. Figure 77 is a section extending from the Paria Plateau, on the east, across H{)use Hock Valley, to the Kaibab Plateau, on the west, and shows the uptumed odgcs of tho rocks on tho brink of the Paria Plateau. The |