The term impact structure is closely related to the terms impact crater or meteorite impact crater, and is used in cases in which erosion or burial have destroyed or masked the original topographic feature with which we normally associate 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 most 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 expression 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.
Famous quotes containing the words impact and/or structure:
“As in political revolutions, so in paradigm choice—there is no standard higher than the assent of the relevant community. To discover how scientific revolutions are effected, we shall therefore have to examine not only the impact of nature and of logic, but also the techniques of persuasive argumentation effective within the quite special groups that constitute the community of scientists.”
—Thomas S. Kuhn (b. 1922)
“One theme links together these new proposals for family policy—the idea that the family is exceedingly durable. Changes in structure and function and individual roles are not to be confused with the collapse of the family. Families remain more important in the lives of children than other institutions. Family ties are stronger and more vital than many of us imagine in the perennial atmosphere of crisis surrounding the subject.”
—Joseph Featherstone (20th century)