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A U-shaped valley is a trough with a wide base, steep slope, U-shaped cross section and a stepped cross section when the ice tongue protruding from the ice bucket or ice cellar erodes, digs (pulls) and erodes the ice bed rock when flowing in the valley. Shaped valley. Such popular glacier tracks in Daweishan Geopark are developed on the northern slope of the mountain than on the southern slope, and the process is also longer. On the north slope, there is a boat bottom nest-sumu bridge U-shaped valley, Yuquan Temple (remains)-Xishangzi-Shiyangcheng U-shaped valley, Qiu’s old house-Dawangkeng U-shaped valley, etc.; on the south slope, there is a water-flooded dam-Wenzhu U-shaped valley and so on. Take the boat bottom nest on the north slope-the U-shaped valley of the Sumuqiao (Lushan Ice Age, Q3) as a representative narrative. This trough is formed by flowing and abrading the ice tongues that protrude from the ice bucket of Tianxing Lake and the ice cellar of the bottom of the ship in the valley. The longitudinal section is stepped, with a width of about 200-300m, the elevation of the trailing edge is about 1300m, and the elevation of the front edge is about 700m. From the trailing edge to the west about 2000m, there are continuous four-level rock sills (ice sills). The first level ice sill at the east end is about 1300m high, and the fourth level ice sill at the west end is about 740m high, with a drop of 460m. The ice ridge lies across the valley contraction, making the entire trough appear as an east-west stepped gourd valley. The cross-sections of these ice sills appear to be steep in the east and steep to the west, and a clear vertical bedrock ice skating surface remains on the west side of the second-level ice sill (near the single-plank bridge). From the vicinity of the Zhuangshishi to the west, side moraine dikes (maulite moraines) are piled up by huge and varying sizes of granite boulders, which extend concentratedly for about 600m and intermittently extend for more than 1km. |
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