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Crater lake

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This page describes the geological feature. For the lake of the same name, see Crater Lake.

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Lake formed after 1991 eruption of Mount Pinatubo, Philippines

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A crater lake is a lake that forms in volcanic calderas or craters after the volcano has been inactive for some time. Some crater lakes are acidic, however, some lakes' water remains fresh. Some also have geothermal activity, especially if the volcano is merely dormant rather than extinct.

A well-known crater lake, which bears the same name as the geological feature, is Crater Lake of Crater Lake National Park, in Oregon, USA. It is formed in the caldera of Mount Mazama. It is isolated from rivers and streams, and therefore has no inflow or outflow at the surface, and hence no pollution from river input. It is fed by melting snow. Crater Lake is the deepest lake in the United States with a depth of 594 m (1949 feet).

Lakes can also fill craters formed by impact events. An example of this is the Lake Bosumtwi in Ghana, Africa.