OCR Text |
Show SAN RAFAEL SWELL 19 Green River and the Wasatch Plateau. All these had their inception in Miocene time except the one around the Grand Canon, which goes back into the latter part of the Eocene. This gradual dissolution of the strata by the waste of their edges constitutes what Powell has called the Recession of Cliffs. Of these five centres of maximum erosion, the San Rafael Swell is by far the best suited for study, and may be regarded as the type of them all. If we stand upon the eastern verge of the Wasatch Plateau and look eastward, we shall behold one of those strange spectacles which are seen only in the Plateau Province, and which have a peculiar kind of impressiveness, and even of sublimity. From an altitude of more than 11,000 feet the eye can sweep a semicircle with a radius of more than 70 miles. It is not the wonder inspired by great mountains, for only two or three peaks of the Henry Mountains are well in view; and these, with their noble Alpine forms, seem as strangely out of place as Westminster Abbey would be among the ruins of Thebes. Nor is it the broad expanse of cheerful plains stretching their mottled surfaces beyond the visible horizon. It is a picture of desolation and decay; of a land dead and rotten, with dissolution apparent all over its face. It consists of a series of terraces, all inclining upwards to the east, cut by a labyrinth of deep narrow gorges, and sprinkled with numberless buttes of strange form and sculpture. We stand upon the Lower Tertiary, and right beneath our feet is a precipice leaping down across the edges of the level strata upon a terrace 1,200 feet below. The cliff on which we stand stretches far northward into the hazy distance, gradually swinging eastward, and then southward far beyond the reach of vision and below the horizon. It describes, as we well know, a rude semicircle around a centre more than 40 miles to the eastward. At the foot of this cliff is a terrace about 6 miles wide of Upper Cretaceous beds, inclining upwards towards the east very slightly, and at that distance it is cut off by a second cliff, plunging down 1,800 feet upon Middle Cretaceous beds. This second cliff describes a smaller* semicircle like the first and concentric with it. From its foot the strata again rise gently towards the east through a distance of 10 miles, and are cut off by a third series of cliffs as before. |