New evidence has emerged demonstrating that a deadly comet devastated North America some 12,900 years ago, causing unimaginable firestorms, the return of the ice age and a 70 percent destruction of human population, according to the findings of 25 strong research team.
This incredible view of events centred around the end of the geological era known as the Pleistocene was presented last week to a stunned audience at the American Geophysical Union meeting in Acapulco, Mexico. It features also in the latest issue of NEW SCIENTIST magazine (194:2605, 26 May 2007, 8-9), from which this story is taken.
Scientists now believe that the cause of this continental sized cataclysm was a disintegrating comet, which fractured into tiny pieces as it entered the atmosphere from the north or northwest, causing massive explosions and fireballs.
A Continent on Fire
One of the three-main scientists speaking on behalf of the team, Jim Kennett, an oceanographer at the University of California, Santa Barbara, showed striking evidence from several sites of large scale wildfires that torched North America in the wake of the comet break-up. In his words: 'The whole continent was on fire.'
Evidence comes from a narrow 12,900 year old carbon-rich layer of sediment uncovered at no less than eight sites belonging to a level known as the Clovis horizon, as well as from several other sample sites of sediment in North America.
At many of the sites the scientific team have uncovered evidence of extraterrestrial debris, including what they refer to as nanodiamonds, tiny glass-like spherules which form rapidly when molten droplets cool rapidly in the air. They form usually during comet or asteroid impacts. Also discovered at the sites were rare helium-3 molecules, which are more common in deep space than on Earth.
'You might find some other explanation for these individually,' said Richard Firestone, a nuclear analytical chemist working at Lawrence Berkeley National Laboratory in California, 'but taken together, it's pretty clear that there was an impact.'
He also believes that the obvious culprit is a comet strike, since the key sediment layers examined thus far have not produced characteristic evidence of high nickel and iridium content, found in connection with asteroid and meteorite impacts, such as that found in connection with the so-called KT Boundary Event suspected of wiping out the dinosaurs some 65 million years ago.
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