astrobleme

astrobleme

[as-truh-bleem]
noun Geology.
an erosional scar on the earth's surface, produced by the impact of a cosmic body, as a meteorite or asteroid. Compare crater ( def 2 ).

Origin:
1965–70; < astro- + -bleme (< Greek blêma shot, wound)

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astrobleme (ˈæstrəˌbliːm)
 
n
a mark on the earth's surface, usually circular, formed by a large ancient meteorite impact
 
[C20: from astro- + Greek blēma shot, wound]

Collins English Dictionary - Complete & Unabridged 10th Edition
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astrobleme

(from Greek astron, blema, "star wound"), remains of an ancient meteorite-impact structure on the Earth's surface, generally in the form of a circular scar of crushed and deformed bedrock. Because such telltale features as crater walls, fused silica glass, and meteorite fragments are heavily modified over time by erosion and weathering, the identification of astroblemes is based chiefly on the presence of subsurface shock structures known as shatter cones. These are conically shaped structures that form in the bedrock directly under the point of impact. They radiate in a distinctive pattern from the point of impact and are identifiable even in drill-core samples. The suddenness and intensity of the shattering cannot be produced by other natural means, so it provides a useful criterion for recognizing astroblemes. Using this evidence, the Ashanti Crater in Ghana and the Vredefort Ring structure in South Africa have been identified as probable astroblemes.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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