1989 Edition


  • Adrian F. Park
Reference work entry

An astrobleme (Greek: star wound) consists of the crater, macro- and microstructures, ejecta and/or shock-metamorphic effects of meteorite impact on the Earthʼns surface. The energy released by such an event is related to the kinetic energy of the projectile, a function of its mass and terminal velocity (e = 1/2mv2 where e = kinetic energy, m = mass, and v = velocity). Thus, a meteorite of radius 10 m (ca. 32,000 t if it is an iron meteorite) traveling at 10 km/sec will release some 1·6 ⋉ 1015 joules, approximately the equivalent of the explosion of 380 kt of TNT (about 20 Hiroshima bombs) or an earthquake of 5 on the Richter scale. A crater up to 0.5 km in diameter would be produced if such an impact occurred on land.

In a fall of this size, or larger, the impact would fragment the projectile and pulverize considerable quantities of country rock: small quantities of impact melt material would also be produced. The explosion that excavates the crater, generating the cloud of ejecta,...
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© Van Nostrand Reinhold 1989

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  • Adrian F. Park

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