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A mountain glacier and its features A glacier is a moving mass of ice. Some glaciers snake down mountain valleys, while others such as the ice sheets of Greenland or Antarctica are so huge and thick they almost totally cover the land. Although it is solid, ice can flow down slopes and around bends, although much more slowly than a river—often less than a metre (3 ft 3 inches) per day. Glaciers occur in very cold regions, high in mountains and in the far north and south polar regions.

The head of a glacier

How glaciers form

A glacier is fed by snow. Over many years, the snow piles up at the head of a high valley and compacts into ice. It collects in a cirque, a bowl-shaped feature. Being thick and heavy, the ice moves under the pressure of its own weight, flowing downhill as a glacier.

About 10% of the Earth's land area is covered with ice, including glaciers, ice caps, and the ice sheets of Greenland and Antarctica.

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