On Thu, Jan 1, 2009 at 10:46 PM, Michael Pollak <mpollak at panix.com> wrote:
>
> http://www.nytimes.com/2009/01/02/science/02impact.html
>
> The New York Times
> January 2, 2009
>
> New Evidence of Meteor Bombardment
>
> By KENNETH CHANG
>
> At least once in Earth's history, global warming ended quickly, and
> scientists have long wondered why.
>
> Now researchers are reporting that the abrupt cooling -- which took
> place about 12,900 years ago, just as the planet was emerging from an
> ice age -- may have been caused by one or more meteors that slammed
> into North America.
>
> That could explain the extinction of mammoths, saber-tooth tigers and
> maybe even the first human inhabitants of the Americas, the scientists
> report in Friday's issue of the journal Science.
>
> The hypothesis has been regarded skeptically, but its advocates now
> report perhaps more convincing residue of impact: a thin layer of
> microscopic diamonds found in rocks across America and in Europe.
>
> "We're up over 30 sites, as far west as offshore California, as far
> east as Germany," said Allen West, a retired geology consultant who is
> one of the scientists working on the research.
>
> The meteors would have been smaller than the six-mile-wide meteor that
> struck the Yucatán peninsula 65 million years ago and led to the mass
> extinctions of the dinosaurs. The killing effects of the hypothesized
> bombardment 12,900 years ago would have been more subtle.
>
> Climatologists believe that the direct cause of the 1,300-year cold
> spell, known as the Younger Dryas, was a sudden rush of fresh water
> from a giant lake in central Canada to the North Atlantic.
>
> Usually a surface current of warm water flows northward in the Atlantic
> toward Greenland and Europe, then cools and sinks, returning south in
> the deep ocean. But the fresh water, which is less dense, blocked the
> sinking of the cold, salty water in the North Atlantic, disrupting the
> currents.
>
> That sudden change in plumbing has long been known, but what caused it
> has never been satisfactorily explained.
>
> The authors of the paper in Science say it was meteors.
>
> <end excerpt>
>
> Full at:
> http://www.nytimes.com/2009/01/02/science/02impact.html
>
> Michael
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