Meteorite Crater

a round depression in the soil formed as a result of the fall of a large meteorite; the diameters of such depressions range from a few meters to tens of kilometers. At velocities of 2–5 km/sec or more, a meteorite is converted at the moment of impact from a solid into a strongly compressed vapor that generates a powerful shock wave. Only small fragments of the meteorite may be preserved.

There are two principal types of meteorite craters: impact and explosion. Intermediate types also exist. Impact craters are characterized by relatively small dimensions (a diameter ranging from 8–9 m to a few tens of meters), an upturned rim, and the presence of numerous, primarily small, meteorite fragments interspersed with fragments of rock. Meteorite dust and meteor dust are usually present in the debris that fills the crater and in the soil surrounding the crater. The characteristic features of an explosion crater are its large size (ranging from many tens of meters to tens of kilometers), strata of rocks that have been uplifted radially with respect to the center of the crater, and the absence in the crater of meteorite fragments, which are usually scattered around it. Depending on the composition of the rocks, the crater may contain impactites; shatter cones, which are distinctive radial structures on the fragments of rocks; and mineral varieties of quartz—coecite and stishovite.

Several dozen single or group meteorite craters are known. The Arizona meteorite crater, located in the United States, measures 1,207 m wide and 174 m deep. In the USSR, there is the Kaalijarv group, consisting of eight craters, located on Saaremaa Island in the Estonian SSR. The diameter of the largest crater, an explosion one, is 110 m, and its depth is 16 m. All known meteorite craters were probably formed thousands of years ago. Twenty-four impact craters (from 8 to 26 m in diameter) were formed on Feb. 12, 1947, in the Primor’e Krai of the USSR as a result of the impact of the huge Sikhote-Alin meteorite.

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