Kettle holes are formed when large blocks of ice calve from the main glacier onto an outwash plain. As the glacier retreats the block of ice is left stranded. The ice then gets surrounded and possibly buried by subsequent meltwater deposits and outwash. Eventually, when the temperature increases and the ice block melts it leaves a large depression in the ground that the ice occupied. These are known as kettle holes. Where the depressions subsequently fill with rainwater, they are known as kettle lakes.