A cirque is a landform that results from erosion by glaciers and flowing water. A cirque is a bowl-shaped hollow that is located at the head of a glacier valley, with a steep back wall and a shallower slope towards the front. Glaciers erode rock by plucking and abrasion, and cirques are formed when the ice plucks out the rock at the head of a valley, leaving a hollow depression. Water from melting glaciers and snow collects in the cirque and may form a lake. Over time, the cirque may erode further, creating a larger basin-shaped valley called a glacier trough.