Corries, also known as cooms, cwms or cirques, are steep-sided, semi-circular features cut into rock during glaciation. They may lie at the head of a valley or as separated incisions on mountain sides. To-day their lowest part may be occupied by a small lake which may be impounded by a moraine or rock bar.

Corries may have originated as hollows where snow accumulated in sufficient quantity for ice to form   As ice built up, it cut back and deepened the hollow, a process which, if sufficiently prolonged and intensive, might lead to the ice spilling out of the hollow and developing over time into a valley glacier.

Small corries are widespread across the higher mountains of Ireland. But the steep-sided Coomshingaun, cut into the eastern face of the Comeragh mountains, is especially impressive. The back wal l of this large corrie rises reaches a height of nearly 430 metres.