Definitions for "U-shaped valley"
A deep valley with steep upper walls that grade into a flat floor, usually eroded by a glacier.
A valley with a U-shaped cross-section caused by glacial erosion. Contrast with the V-shape of a typical stream valley.
The U-shaped valleys (or beheaded glacial valleys) that form Sun Notch and Kerr Notch were carved by glaciers on Mount Mazama. The glaciers had retreated far up the volcano when the caldera collapsed, beheading these and other, less spectacular valleys at the caldera wall. Glacial valley is shaped like a U, whereas stream valley (V-shaped valley carved by water) is shaped like a V.