Describe the conditions and processes involved in the formation of a corrie

There are physical conditions required for the formation of a glacial corrie to take place. For the processes to begin, snow must collect in a naturally occurring hollow on the side of a mountain. The hollow is often required to be north-facing, unless shadowed by a larger mountain, as this is where the accumulation of snow is greater than the ablation. This allows snow to become compressed in the hollow from the weight of the snow accumulation, and the snow at the base of the hollow turns to ice. There are four main processes that occur after enough snow material has accumulated in the hollow, one of which being freeze-thaw weathering. Freeze-thaw, sometimes referred to as frost shattering, is a physical process affecting the back wall of the hollow, whereby water enters cracks in the hard rock during the day when temperatures are higher and freezes at night in subzero temperatures. The continuation of this wears down the rock, allowing more water to enter the cracks each day, resulting in a jagged wall and the creation of scree. Other common glacial processes such as plucking and abrasion take place, deepening and widening the hollow and pushing down the moraine created during these processes, which puts into motion the final process, named rotational sliding. Rotational sliding pushes moraine in a circular motion towards the front of the corrie, known as the rock lip. An over build-up of the debris may result in the formation of a corrie lochan if enough melt water is trapped.