Shatter cone

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 range of 2-30 GPa.cite book
author = French, B.M.
year = 1998
title = Traces of catastrophe
publisher = Lunar and Planetary Institute
isbn =
url = http://www.lpi.usra.edu/publications/books/CB-954/CB-954.intro.html
accessdate = 2007-05-20 ] cite journal
author = Sagy, A.
coauthors = Fineberg, J.; Reches, Z.
year = 2004
title = Shatter cones: Branched, rapid fractures formed by shock impact
journal = Journal of Geophysical Research
volume = 109
pages = B10209
doi = 10.1029/2004JB003016
url = http://web.cocc.edu/breynolds/classes/UO_Geol_353/shatter%20cones.pdf
accessdate = ] Citation
last = French
first = Bevan M.
title = Stalking the Wily Shatter Cone: A Critical Guide for Impact-Crater Hunters
journal = Impacts in the Field
publisher = [http://web.eps.utk.edu/ifsg.htm Impact Field Studies Group]
volume = 2
issue = Winter
pages = pgs 3-10
year = 2005
url = http://web.eps.utk.edu/ifsg_files/newsletter/Winter_2005.pdf]

Shatter cones have a distinctively conical shape that radiates from the top ("apex") of the cones repeating cone-on-cone in large and small scales in the same sample. Sometimes they're more of a spoon shape on the side of a larger cone. In finer-grained rocks such as limestone, they form an easy to recognize "horsetail" pattern with thin grooves (""). Coarser grained rocks tend to yield less well developed shatter cones, which may be difficult to distinguish from other geological formations such as slickensides. Geologists have various theories of what causes shatter cones to form, including compression by the wave as it passes through the rock or tension as the rocks rebound after the pressure subsides. The result is large and small branching fractures throughout the rocks.

Shatter cones can range in size from microscopic to several meters. A very large example of more than 10 meters in length is known from the Slate Islands impact structure, Canada. The azimuths of the cones's axes typically radiate outwards from the point of impact, with the cones pointing upwards and toward the center of the impact crater. Though the orientation of the rocks may be changed by post-cratering geological processes at the site.

Photo gallery

References

ee also

* Breccia
* Coesite
* Lechatelierite
* Shocked quartz
* Stishovite


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  • shatter cone — noun Date: 1933 a conical fragment of rock that has striations radiating from the apex and that is formed by high pressure (as from volcanism or meteorite impact) …   New Collegiate Dictionary

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