Ice calving

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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. 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 three kilometres (1+1⁄2 nautical miles). 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 often preceded by a rift. An ice shelf in steady state calves at roughly the same rate as the influx of new ice, and calving events may occur on sub-annual to decadal timescales to maintain an overall average mean position of the ice shelf front. When calving rates exceed the influx of new ice, ice front retreat occurs, and ice shelves may grow smaller and weaker.