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a valley whose floor ends with a drop to the floor of another, larger valley or to the shore of a sea or lake.
Hanging valleys are formed by the significant differences in the erosive forces of water currents of the main valley and the valley of a tributary, as a result of which the cutting of the tributary lags behind the deepening of the valley of the main river. On sea and lake shores hanging valleys arise because the water-current erosion is slower than the destruction of the shore by surf. The occurrence of a hanging valley can also be connected with sharp changes in the basis of erosion, tectonic movements, a rapid decrease in the level of a reservoir, and differences in the lithology of the washed rocks; in mountain regions, hanging valleys may be connected with the varying speed of valley deepening by glaciers.