astrobleme


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astrobleme

(ăs`trōblēm'), large, circular structure ranging from c. 1-2 mi to 40 mi (.8–64 km) in diameter. Astroblemes are found at numerous places on the earth's surface, e.g., Meteor, or Barringer, Crater in Arizona, Brent Crater in Ontario, and Vredefort Ring in South Africa. The presence of meteor fragments, strange conical fracture patterns (called shatter cones), and coesite (a superdense, high-pressure form of quartz) in the rocks at astroblemes suggest an impact, rather than volcanic, origin to these circular structures.

astrobleme

[′as·trō‚blēm]
(geology)
A circular-shaped depression on the earth's surface produced by the impact of a cosmic body.
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References in periodicals archive ?
For instance, Gravbeg-1 (Sweden) and Vorotilov (Russia) boreholes were drilled within astroblemes, i.
2004, A re-evaluation of the size of the Carswell astrobleme, Saskatchewan, Canada: 67th Annual Meteodrical Society Meeting: 5071.
En effet, les geologues qui faisaient des forages en mer de Barents ont trouve le plus grand astrobleme d'Europe, date de 150 M.
Mots cles: geomagnetisme, astroblemes, tectites, inversion de polarite.