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(in Icelandic, literally “mosquito lake”), a lake in northeastern Iceland. Area, 38 sq km; maximum depth, 4.5 m; elevation of surface, 277 m. The lake occupies an ancient glacial basin, dammed up by a lava flow. The water, which is light blue, is distinctive because of its great clarity. The lake is drained by the Laxa River (length, 58 km) into the Greenland Sea. Myvatn contains many volcanic islands; individual craters have heights of 20–30 m. Fumaroles are found by the eastern shore. Clouds of mosquitoes swarm over Myvatn in the summer; this gave the lake its name. There is tourism.