Ice calving

Ice calving, also known as glacier calving or iceberg calving, is the breaking of ice chunks from the edge of a glacier. It is a form of ice ablation or ice disruption and is normally caused by the glacier expanding. It is the sudden release and breaking away of a mass of ice from a glacier, iceberg, ice front, ice shelf, or crevasse. The ice that breaks away can be classified as an iceberg, but may also be a growler, bergy bit, or a crevasse wall breakaway.

Calving of glaciers is often accompanied by a loud cracking or booming sound before blocks of ice up to 60 metres (200 ft) high break loose and crash into the water. The entry of the ice into the water causes large, and often hazardous waves. The waves formed in locations like Johns Hopkins Glacier can be so large that boats cannot approach closer than 3 kilometres (1.9 mi). These events have become major tourist attractions in locations such as Alaska.

Many glaciers terminate at oceans or freshwater lakes which results naturally with the calving of large numbers of icebergs. Calving of Greenland's glaciers produce 12,000 to 15,000 icebergs each year alone.

Calving of ice shelves is usually preceded by a rift. These events are not often observed.

Etymologically, calving is cognatic with calving as in bearing a calf.

It is useful to classify causes of calving into first, second, and third order processes. First order processes are responsible for the overall rate of calving at the glacier scale. The first order cause of calving is longitudinal stretching, which controls the formation of crevasses. When crevasses penetrate the full thickness of the ice, calving will occur. Longitudinal stretching is controlled by friction at the base and edges of the glacier, glacier geometry and water pressure at the bed. These factors, therefore, exert the primary control on calving rate.

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