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Show GENEKAL STBUCTTTRE OP THE WASATCH PLATEAU. 161 The eastern front of the plateau is simply a wall left standing by the erosion of the region which it faces. The Tertiary beds upon the summit, as well as ihe Cretaceous beneath, once spread, unbroken and undisturbed, as far to the eastward as the eye can reach, and thence far beyond the limits of vision. From the strange land which that summit now overlooks at an altitude of 11,500 feet, more than 8,000 feet of Tertiary and Mesozoic strata have been swept away, and the region which has been thus devastated is large enough for a great kingdom. The Wasatch Plateau is a mere remnant of that protracted process, and, so far as it extends, is a mere rim standing along a portion of the western boundary of the Plateau Province. The western front of the plateau, then, is a great monoclinal flexure, and its eastern front is a wall of erosion. To the northward the beds which compose it stretch far up toward the Uinta Mountains, still ending in lines of great cliffs or bold slopes gradually swinging to the eastward until, after a course of nearly a hundred miles, they cross the Green River, where Powell named the Tertiaries the Roan Cliffs, and the Upper Cretaceous the Book Cliffs. Southward the Tertiaries forming the summit of the plateau end abruptly in a precipice extending east and west, while the underlying Cretaceous beds continue, forming a lower terrace overlooking the still lower level of Castle Valley. The average altitude of the table is about 11,000 feet, and it stands from 5,500 to 6,000 feet above San Pete Valley on the west and about the same height above Castle Valley on the east. To gain an adequate conception of the great monoclinal, which forms the western flank, we must recur to the consideration that the upward curvature and reflection to horizontality leaves the Lower Tertiary beds full 5,500 feet above still more recent ones in the valley below. If the latter were now continuous across the summit, as they once probably were, the altitude would be from 1,500 to 2,000 feet greater than at present. Thus the total rise of the monoclinal appears to have been more than 7,000 feet, and the uplift has occurred with a near approach to equality along a line of strike of 50 miles. The transverse structure will be seen by referring to Plate 3, sections 6 and 7. The platform of the summit is rugged, the irregularities being due 11 H P |