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Research team says extraterrestrial impact to blame for Ice Age extinctions
Date:9/24/2007

What caused the extinction of mammoths and the decline of Stone Age people about 13,000 years ago remains hotly debated. Overhunting by Paleoindians, climate change and disease lead the list of probable causes. But an idea once considered a little out there is now hitting closer to home.

A team of international researchers, including two Northern Arizona University geologists, reports evidence that a comet or low-density object barreling toward Earth exploded in the upper atmosphere and triggered a devastating swath of destruction that wiped out most of the large animals, their habitat and humans of that period.

The detonation either fried them or compressed them because of the shock wave, said Ted Bunch, NAU adjunct professor of geology and former NASA researcher who specializes in impact craters. It was a mini nuclear winter.

Bunch and Jim Wittke, a geologic materials analyst at NAU, are co-authors of the paper, which fingers an extraterrestrial impact 12,900 years ago for the mass extinctions at the end of the Ice Age. The paper was just released online in the Proceedings of the National Academy of Sciences. The research team includes several members of the U.S. National Academy of Sciences and researchers from Hungary and the Netherlands.

No one has found a giant crater in the Earth that could attest to such a cataclysmic impact 13,000 years ago, but the research team offers evidence of a comet, two and a half to three miles in diameter, that detonated 30 to 60 miles above the earth, triggering a massive shockwave, firestorms and a subsequent drastic cooling effect across most of North America and northern Europe.

The comet may have broken up into smaller pieces as it neared the Earth and then these pieces detonated in various places above two continents, Bunch said.

The evidence for multiple detonations comes from a four-inch-thick black mat of carbon-rich material that appears as far n
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Contact: Lisa Nelson
Lisa.Nelson@nau.edu
928-523-6123
Northern Arizona University
Source:Eurekalert

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