Vatnajökull (vätˈnäyöˈkŏl) [key], glacier, c.3,150 sq mi (8,160 sq km), SE Iceland; largest glacier in Europe. At an elevation of from 4,200 to 6,100 ft (1,280–1,860 m), it covers a huge volcanic plateau, which includes the Grím,svötn caldera, Iceland's third largest and historically most active volcano; the periodic release of water from the subglacial lake in the caldera, where heat melts the ice, has resulted in catastrophic flooding. Vatnajökull descends in some 40 branches into adjoining valleys. Some peaks rise above the ice, notably Öraefajökull.
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