An impact structure is a generally circular or craterlike
geologic structure of deformed
bedrock
In geology, bedrock is solid rock that lies under loose material (regolith) within the crust of Earth or another terrestrial planet.
Definition
Bedrock is the solid rock that underlies looser surface material. An exposed portion of bedro ...
or
sediment produced by
impact on a
planetary surface, whatever the stage of
erosion of the structure. In contrast, an
impact crater is the surface expression of an impact structure. In many cases, on Earth, the impact crater has been destroyed by erosion, leaving only the deformed rock or sediment of the impact structure behind.
[Neuendorf, K.K.E., J.P. Mehl Jr., and J.A. Jackson, eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. ] 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 cone
Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact craters or underground nuclear explosions. They are evidence that the rock has been subjected to a shock with pressures in the ran ...
s,
geochemical evidence of
extraterrestrial material or other methods.
See also
*
Complex crater
Complex craters are a type of large impact crater morphology.
Above a certain threshold size, which varies with planetary gravity, the collapse and modification of the transient cavity is much more extensive, and the resulting structure is call ...
*
Earth Impact Database
*
Impact event
*
List of impact craters on Earth
*
List of possible impact structures on Earth
This is a list of possible impact structures on Earth. More than 130 geophysical features on the surface of the Earth have been proposed as candidate sites for impact events by appearing several times in the literature and/or being endorsed by the ...
* ''
Traces of Catastrophe
''Traces of Catastrophe: A Handbook of Shock-Metamorphic Effects in Terrestrial Meteorite Impact Structures'' is a book written by Bevan M. French of the Smithsonian Institution. It is a comprehensive technical reference on the science of impact ...
'' book from
Lunar and Planetary Institute - comprehensive reference on impact crater science
*
Peak ring
References
External links
Terrestrial Impact Cratersat the Lunar and Planetary Institute
Earth Impact Database
{{Authority control
Impact geology