How is a corrie formed?

A corrie is an armchair shaped depression on a mountain slope left by a cirque glacier. These are the steps leading to its formation: 1) Snow collects in a hollow on a mountain slope (normally the north facing slope in the Northern Hemisphere) and compacts into ice over several winters. 2) The ice gets heavy enough to flow under gravity and, using abrasion, carves out and deepens the “seat” of the armchair, while plucking and freeze-thaw processes steepen the head wall. 3) The glacier flows in a circular motion called “rotational slip” which concetrates the erosion at the base and lessens the erosion at the front, which allows the formation of a corrie lip from uneroded bedrock and deposited till. 4) The cirque glacier retreats to expose the armchair shaped depression in the rock face, sometimes leaving a meltwater lake called a “tarn” in the deep hollowed out “seat” of the armchair.