Meteor craters are not volcanic, they are landforms associated with ‘fire’ not from within but outside the earth. The meteorites cause scars on the surface by their impact. The meteor theory of the origin of craters, however, has not always been accepted unequivocally. Some believe these craters as due to volcanic explosion even when the evidences of volcanic activity are scarce. But there are some craters in which the evidences weigh in favor of meteoric explosion. One of these is Meteor Crater in Arizona, U.S.A. (c. 200 meters deep, over one kilometer across, the rim being about 45 meters high above the surrounding country).
“It has apparently been formed by an explosion resulting from impact of an exceptionally large meteorite with the earth.” Another feature called Pretoria Salt Pan in South Africa, c. a kilometer across and 120 meters deep is believed to be of meteoric origin. This is also believed to be the nature of Lonar Lake (c. 1 ½ kilometer in diameter and 100 meters deep) in Buldana district of Maharashtra in Deccan trap country. The region has not witnessed any volcanism for several geological periods.
The raised rim which characterizes this and other craters is believed to have been caused by the great fiery explosion occasioned by the impact of a larger meteorite. Mud Volcano Craters. Such shallow craters are associated with ‘mud volcanoes’. Mud Volcanoes are not volcanoes. They are bodies of mud in relatively young oilfield areas (e.g., Burma, Timor, Trinidad and the Caucasus oilfield areas) ejecting mud due to compaction and consequent pressure in unconsolidated formation. The eruption of mud, associated with natural oil gases may be hot as it comes from depth and may be accompanied with steam giving the semblance of volcanic eruption.
Some small craters may also form in areas of artesian basins. Artesian pressure pushes up various substances which, with the escape of gases contained in them, accumulate as cratered mounds as in the Great Artesian Basin of Australia.