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A volcanic crater that was created by violent explosion but not accompanied by igneous extrusion; frequently, it is filled by a small circular lake.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



a funnel-shaped or cylindrical depression of volcanic origin, formed on the earth’s surface during a single gas explosion not accompanied by the extrusion of lava. They are up to 3,200 m across and 300-400 m deep. Maars are often ringed by ridges made up of fragments of rock shattered by the gases. In wet climates maars often fill with water and form lakes, for example, the Laacher See in the Eifel massif (Federal Republic of Germany) and Lakes Pavin and La Godivelle in Auvergne, France.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Some other unusual eruptive processes may have been important at these high-latitude maars. For instance, the depth of excavation of the maars is similar to but slightly greater than the modern thickness of permafrost.
Volcaniclastic sediments surrounding Devil Mountain Maar and the other Espenberg Maars contain evidence of numerous surges and explosions during these hydromagmatic eruptions.
As shown in this paper, hydromagmatic eruptions through permafrost on the northern Seward Peninsula of Alaska have repeatedly excavated caldera-sized craters, forming the largest known maars on earth (Beget and Mann, 1992).
While the Espenberg maars are currently the only known examples of caldera-sized maars formed by permafrost-magma interactions, it is important to note that broadly similar processes may operate during hydromagmatic eruptions at maars at lower latitudes.
Lorenz (1986) suggested that maars form when hydromagmatic explosions "ream out" funnel-shaped vents that had become backfilled with ejecta and wall-collapse material.
Although similar maars have not been described from other areas of the world, it seems likely that other examples of unusually large maar craters exist.
Devil Mountain Lakes Maar on the northern Seward Peninsula is the largest known maar on earth, and South Killeak, North Killeak, and Whitefish Maars are also larger than any previously described maars on earth.
The four Espenberg Maars are similar in size to or larger than small calderas like those at Kilauea, Katmai, and Crater Lake.
Key words: maar, permafrost, arctic, Alaska, hydromagmatic
Mots cles: maar, pergelisol, arctique, Alaska, hydromagmatique