| OCR Text |
Show c CHAPTER XII. TIIE l>llYSICAL .I!"'EATURES 0.1!' THE VALLEY OF 'l'IJI~ COLORADO, CONTINUED. In the previous chapter, I have made frequent mention of long lines of cliffs, or escarpments, extending across th~ Colorado, far back into the country on either side. I have attempted to explain the origin of these cliffs, as well as tho origin of cafions, as due to the erosion of greater or smaller folds of tho stony formations, or beds of rock. rro explain the chief characteristics of the Grand Caiion, and the adjacent country, it is necessary to describe other lines of cli1Is, due to other causes. CI.Il"FS AND SLOPES OF DISPLACEMENT. The geological formations, or beds of roek, exposed in the Grand Canon and the tributary gorges, have been fractured, or folded, on an extensive scale. 'rheso groat fractures, or folds, extend across tl10 canon in a northerly and souther! y direction, 9-nd can be traced for scores of miles on either sidenot as huge cracks, or chasms, for they arc observable only to the eye of tho geologist, and are traced by the high steps and great displacements seen along their cow·ses. Along these fractures we find what geologists call faults, i.e., the beds have fallen down on one side of each crack. This displacement, or throw of the fault, ils it is technically called, is from one or two hundred to two or three thousand feet, and is always noticed to be quite variable along any particular fault which may be studied. Let us try to obtain a well defined conception of such a fault. Suppose that a fracture should be formed, extending from the shore of Lake Erie, in the northwest corner of Pennsylvania, diagonally through the State to the head of Delaware Bay-a groat crack, tlu·ough tho underlying rocks, to unknown depths below-and that the country on the southwestern side I |
