Valley - Hanging Valleys

Hanging Valleys

A hanging valley is a tributary valley with the floor at a higher relief than the main channel into which it flows. They are most commonly associated with U-shaped valleys when a tributary glacier flows into a glacier of larger volume. The main glacier erodes a deep U-shaped valley with nearly vertical sides while the tributary glacier, with a smaller volume of ice, makes a shallower U-shaped valley. Since the surfaces of the glaciers were originally at the same elevation, the shallower valley appears to be ‘hanging’ above the main valley. Often, waterfalls form at or near the outlet of the upper valley. Hanging valleys are also the product of varying rates of erosion of the main valley and the tributary valleys. The varying rates of erosion are associated with the valleys rock composition of the adjacent rocks in the different valley locations. The tributary valleys are eroded and deepened by glaciers at a slower rate than that of the main valley floor. Thus the difference in the two valleys depth increases over time. The tributary valleys that were composed of more resistant rock then hangs over the main valley.