. Elements of geology : a text-book for colleges and for the general reader. Geology. FISSURES, OR FRACTURES. 222 20,000 feet. In Southwest Virginia, accord- ing to Rogers, there is a line of fracture ex- tending parallel to the Appalachian chain for eighty miles, in which there is a vertical slip of 8,000 feet,* the Lower Silurian being brought up on one side until it comes in con- junction with the Lower Carboniferous on the other (Fig. 196). In Western Pennsyl- vania, according to Leslie, there is another fault extending for twenty miles, in which the lowermost of the Lower Silurian is brou
. Elements of geology : a text-book for colleges and for the general reader. Geology. FISSURES, OR FRACTURES. 222 20,000 feet. In Southwest Virginia, accord- ing to Rogers, there is a line of fracture ex- tending parallel to the Appalachian chain for eighty miles, in which there is a vertical slip of 8,000 feet,* the Lower Silurian being brought up on one side until it comes in con- junction with the Lower Carboniferous on the other (Fig. 196). In Western Pennsyl- vania, according to Leslie, there is another fault extending for twenty miles, in which the lowermost of the Lower Silurian is brought up on a level with the uppermost of the Upper Silurian, the whole Silurian strata being at this place 20,000 feet thick, so that one may stand astride of the fissure with one foot on the Trenton limestone (Lower Silu- rian), and the other on the Hamilton shales (Devonian).f On the north side of the Uintah Mountains there is a slip, according to Powell, of nearly 20,000 feet. J The Sevier Valley fault, Utah, may be traced partly as a slip, partly as a monoclinal fold, for 225 miles (Gilbert). On the west side of the Wahsatch range there is a fault of 40,000 feet (King),* and on the east side of the Sierra one of at least 15,000 feet. || But nowhere on this continent, or per- haps in the world, are fissures and faults de- veloped on so grand a scale as in the high Plateau region, i. e., the region bounded by the Wahsatch, the Uintah, and the Colorado Mountains. The whole of this elevated re- gion is traversed by a system of north and south fissures, extending for hundreds of miles, by which the almost horizontal strata are broken into huge oblong prismatic blocks many miles wide. The slipping of these blocks, some to a higher and some to a lower level, with a difference of 1,000 to 5,000 feet, * Dana's Manual, p. 399. f Manual of Coal, p. 147. % Exploration of Colorado River, p. 156. * Survey of the Fortieth Parallel, vol. i, pp. 728-746. || Le Conte, American Journal of Scie
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