Popigai crater

The Popigai crater in Siberia, Russia is tied with Manicouagan Reservoir as the 4th largest impact crater on Earth.Cite book
publisher = Springer
pages = 81-85
last = Masaitis
first = Victor L.
title = Popigai Crater: General Geology
date = 2003
url = http://books.google.com/books?hl=en&lr=&id=mLfsNALR19oC&oi=fnd&pg=PA109&dq=Popigai+Chesapeake+age&ots=k1GTZnBtjO&sig=4dQ9bN1z4gYv8Rmd1KpxwKR39Pw#PPA81,M1] A large bolide impact created the 100-kilometer diameter crater 35.7 ± 0.2 (2σ) million years ago during the late Eocene (Priabonian stage).Cite journal
volume = 41
pages = 689–703
last = Deutsch
first = Alexander
coauthors = Christian Koeberl
title = Establishing the link between the Chesapeake Bay impact structure and the North American tektite strewn field: The Sr-Nd isotopic evidence
journal = Meteoritics & Planetary Science
accessdate = 2008-06-16
date = 2006
url = http://www.ingentaconnect.com-content-arizona-maps-2006-00000041-00000005-art00004] Cite book
publisher = Springer
pages = 99-116
last = Armstrong
first = Richard
coauthors = S. Vishnevsky & C. Koeberl
title = U-Pb Analysis of zircons from the Popigai impact structure, Russia: First Results
date = 2003
url = http://books.google.com/books?hl=en&lr=&id=mLfsNALR19oC&oi=fnd&pg=PA109&dq=Popigai+Chesapeake+age&ots=k1GTZnBtjO&sig=4dQ9bN1z4gYv8Rmd1KpxwKR39Pw] The crater is just north of the Siberian city Norilsk, or 1 1/2 hours (by helicopter) from the outpost of Khatanga. It is designated by UNESCO as a Geopark, a site of special geological heritage.Cite journal
volume = 23
number = 1
pages = 3–12
last = Deutsch
first = Alexander
coauthors = V.L. Masaitis, F. Langenhorst & R.A.F. Grieve
title = Popigai, Siberia—well preserved giant impact structure, national treasury, and world’s geological heritage
journal = Episodes
accessdate = 2008-06-16
date = 2000
url = http://www.episodes.org/backissues/231/03-11%20Deutsch.pdf]

For decades the Popigai crater has fascinated paleontologists and geologists, but the entire area was completely off limits because of the diamonds and the mines constructed by gulag prisoners under Stalin; however, a major investigatory expedition was undertaken in 1997 (IPEX 1997) which greatly advanced understanding of the enigmatic structure. The impactor in this event has been identified as either an eight-kilometer diameter chondrite asteroid, or a five-kilometer diameter stony asteroid.

The shock pressures from the impact instantaneously transformed graphite in the ground into diamonds within a 13.6 kilometer radius of the impact point. Diamonds are usually 0.5 to 2 millimeters in diameter; a few exceptional specimens are 10 millimeters in size. The diamonds not only inherit the tabular shape of the original graphite grains but they additionally preserve the original crystal's delicate striations.

Popigai is the best example yet of the formation of a crater of this type. Three other craters are larger, but they are either buried (Chicxulub), strongly deformed (Sudbury), or deformed and severely eroded (Vredefort).

There is a small possibility that Popigai impact crater formed simultaneous with the "c." 35 million year old Chesapeake Bay and Toms Canyon impact craters.

References

External links

* [http://www.unb.ca/passc/ImpactDatabase/ Earth Impact Database]
* [http://www.mines.edu/academic/geology/faculty/klee/PopigaiImpact.pdf About the Popigai impact structure]
* [http://unesdoc.unesco.org/images/0015/001500/150007e.pdf UNESCO Global Geopark Network]