| OCR Text |
Show SUMMIT VALLEY. 259 about 9,300 feet, brings us upon the floor of Summit Valley. Upon the west is a sharp crest-line, constituting the eastern verge of Fish Lake Plateau, which overlooks the valley from an altitude of 11,000 to 11,400 feet. Upon the east side rise two conspicuous massesâ€"Mount Terrill and Mount Marvine. This valley is an excellent starting-point, from which we may make excursions radiating in many directions, and study in detail the diversified objects which compose the surrounding country. And, first, let us look at the nature of the valley itself. Not the smallest among its attractions for the geologist is the fact that it is a most eligible summer camping-place. In the daytime, throughout July, August, and most of September, it is mild and genial, while the nights are frosty and conducive to rest. The grass is long, luxuriant, and aglow with flowers. Clumps of spruce and aspen furnish shade from the keen rays of the sun, and fuel is in abundance for camp-fires. Thus the great requsites for Western camp-life, fuel, water, and grass, are richly supplied, while neither is in such excess as to be an obstacle to progress and examination. The valley floor is, for the most part, Lower Tertiary. For a considerable portion of the length the edges of these beds are exposed upon the eastern side of the valley, forming the lower slopes of Mounts Terrill and Marvine. They are also seen at the base of the Fish Lake slopes; but a little higher up they are covered with ancient lavas. Northward, however, lavas form the floor of the valley. Proceeding in that direction a few miles, the mountain-walls which inclose the valley rapidly decline in altitude and die away in steep slopes, while the platform on which we travel at length becomes the summit of a plateau, having an altitude about 2,000 feet lower than the neighboring tables; and projecting 4 or 5 miles farther northward, it ends in abrupt volcanic cliffs, from the crests of which we overlook all the space which intervenes between them and the "Wasatch Plateau, 20 miles distant. The thickness of the lava at these cliffs is about 700 feet, and is composed of hornblendic trachytes in very massive sheets, alternating with augitic andesites, which are much thinner. Retracing our steps and traveling to the southern end of the valley, we find its floor undulating with little hills, a part of which are Eocene beds and a part are old |
