- BAVON, Va. - It is so peaceful
here - a flat green marsh bordering bay waters, reeds, scrubby pines, gulls
circling a distant lighthouse.
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- Only the clatter of a drilling rig breaks the spell,
as scientists poke deep below the ground. They are searching for traces
of one of the greatest catastrophes ever to hit the Earth.
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- Near this spot 35 million years ago, an enormous ball
of ice or rock screeched down from outer space in a blinding flash of light
and blasted a crater 56 miles across and almost a mile deep.
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- The meteor, the largest ever to strike what is now the
United States, hurled fragments as far as Antarctica and gouged a depression
that lies under the Chesapeake Bay, one of the East Coast's scenic wonders.
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- Today, a rough circle of low ridges in Virginia's coastal
plain, near historic Williamsburg and Jamestown, marks the outer rim of
the ancient crater, which is buried under thousands of feet of sand, silt
and clay.
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- Other signs of the collision remain: Two million nearby
residents face a shortage of fresh water, because the searing heat of the
long-ago impact vaporized huge quantities of seawater, leaving the basin
still filled with salt that threatens their freshwater aquifers. Nearby
rivers make a peculiar sharp bend as they are diverted toward the sunken
crater.
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- This summer, researchers from the U.S. Geological Survey
are drilling holes in and around the Chesapeake Bay Impact Crater, as it
is known. They are trying to understand what happened when the meteor hit
and what it means for people now and in the future.
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- Wylie Poag, a senior USGS scientist, pointed out that
our planet is constantly pummeled by extraterrestrial objects, around 25,000
of them each year. Most are small and harmless. A little one bonked a boy
on the head in Uganda in 1992, injuring him slightly; another dented in
a car fender in Peekskill, N.Y., the same year.
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- But it's only a matter of time, experts say, before another
"big one" strikes, like the monster that rammed the Earth off
the coast of Mexico 65 million years ago. Scientists think the long-lasting
global climate change that followed that collision wiped out the dinosaurs
and thousands of other species.
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- Speaking above the roar of the drill, Poag, who found
and identified the Chesapeake crater in 1994, shows off a box of cylindrical
cores pulled up from 2,000 feet below the ground. The muddy cylinders,
each about the size and shape of a child's baseball bat, show rock that
was twisted, jumbled and squeezed by the battering it endured long ago.
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- Scientists aren't certain whether the meteor was a comet,
made mostly of ice, or an asteroid, a lump of stone or iron. At 2 to 3
miles in diameter, it was only a third the size of the Mexican dinosaur-killer.
But when it crashed into the ocean here at 60,000 mph, it did awesome damage.
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- The splash-down caused a massive tidal wave that surged
far inland into the Appalachian foothills. Such a wave, known as a super-tsunami,
can tower more than a thousand feet, Poag said, as it roars into shallow
water near the shore.
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- In addition, a hail of white-hot debris flung outward
by the impact turned the Eastern United States into a wasteland. A cloud
of dust encircled the globe, darkening the sky for months. The world's
climate rapidly warmed and then cooled, perhaps contributing to a mass
extinction of sea creatures a million years later.
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- "Life on Earth would have been shocked, vaporized,
pulverized, barbecued, blinded, irradiated, acidified, drowned, starved
and frozen," Poag wrote in his book, "Chesapeake Invader."
"A similar strike in Chesapeake Bay today would wipe out all the major
East Coast cities, killing tens of millions. The scale of annihilation
is appalling to contemplate."
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- http://www.charlotte.com/observer/natwor/docs/crater0905.htm
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