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Did a Comet Cause a North American Die-Off around 13,000 Years Ago?
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dav-@quik.com
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Jul 22, 2009 06:00 PDT
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http://www.scientificamerican.com/article.cfm?id=did-a-comet-cause-die-off
July 20, 2009
Did a Comet Cause a North American Die-Off around 13,000 Years Ago?
Tiny hexagonal diamonds suggest a massive impact during the late
Pleistocene that could have wiped out the Clovis people,
mastodons and other continental inhabitants--but the geologic
evidence falls short for some skeptics
Researchers have found shock-synthesized hexagonal diamonds on one
of California's Channel Islands, which they say is the strongest
evidence yet that a comet exploded in the atmosphere above North
America, causing widespread extinctions there around 12,900 years
ago. Skeptics, however, say the debate is far from over.
In 2007 researchers theorized that a comet set off continental fires
that led to the mysterious disappearance of the Clovis people and
the extermination of 35 mammal genera, including mammoths,
mastodons, ground sloths and camels. The team documented a
"black mat" of charcoal throughout North America that contains high
levels of iridium, magnetic spheres, and nano-diamonds, which are
consistent with such an airburst. The controversial theory also
gibes with the 1908 Tunguska atmospheric detonation (also thought to
be from a comet or meteorite) that leveled trees in Siberia, and it
echoes the extraterrestrial impact widely believed to have wiped out
the dinosaurs 65 million years ago.
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