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The term impact structure is closely related to the terms ''impact crater'' and ''meteorite impact crater'', and is used in cases in which erosion or burial has destroyed or masked the original topographic feature with which one normally associates the term ''crater''. This is the fate of almost all old impact craters on Earth, unlike the ancient pristine craters preserved on the Moon and other geologically inactive rocky bodies with old surfaces in the Solar System. Impact structure is synonymous with the less commonly used term ''astrobleme'' meaning "star wound". In an impact structure, the typical visible and topographic expressions of an impact crater are no longer obvious. Any meteorite fragments that may once have been present would be long since eroded away. Possible impact structures may be initially recognized by their anomalous geological character or geophysical expression. These may still be confirmed as impact structures by the presence of shocked minerals (particularly shocked quartz), shatter cones, geochemical evidence of extraterrestrial material or other methods. == See also == * Complex crater * ''Traces of Catastrophe'' book from Lunar and Planetary Institute - comprehensive reference on impact crater science * Earth Impact Database * Impact event 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Impact structure」の詳細全文を読む スポンサード リンク
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