Unearthing Clues to a Cataclysm
Sunday, October 23, 2005
EASTVILLE, Va. A white fireball two miles across thunders from the sky at 30,000 mph and crashes into the ocean off the Virginia coast. The impact vaporizes billions of tons of water, rips a hole in the sea floor six miles deep and fractures the bedrock far into the Earth.
The splash is 30 miles high. Debris is lofted over the horizon and rains down on an area of 3 million square miles, as distant as the Antarctic. Towering tsunamis surge toward the Blue Ridge Mountains.
Nearby life -- ferocious-looking sea creatures and dog-sized proto-horses along the tropical shoreline -- is blasted and then swept into the abyss by the boiling ocean. A calamity of unimaginable scale, it is probably the most stupendous geological event ever on the East Coast.
For more than a decade, geologists have believed that a gigantic object, an asteroid or a comet, struck the Earth north of Norfolk about 35 million years ago in a cataclysmic occurrence that left behind a 53-mile-wide, long-buried crater.
An international team of scientists, seeking clues to the origins of the planets, has assembled in a windblown bean field near the crater's center to try to determine, among other things, exactly what happened when the object struck.
Since early last month, the team has been working with a large drilling rig that uses diamond-tipped bits and brings up core samples to bore through eons of sedi ment toward the floor of the crater and the place where the impactor hit, believed to be about 7,000 feet below the surface.
As a farmer harvested his soybean crop just north of Cape Charles on Virginia's Eastern Shore and the wind off the Chesapeake Bay blew dust and grasshoppers across the drilling site, it was hard to imagine the scale of what geologists believe happened there.
"This is so big that we can't really picture it," said David S. Powars, a U.S. Geological Survey geologist, who said he first suspected the presence of an impact crater in the 1980s. "You could take the whole nuclear arsenal in its heyday: Russia, China, U.S. . . . That's a firecracker compared to what this explosion would be."
The men and women of the small but intense crater community who gather at the spot attempt to picture it every day. "I dream this all the time," Powars said. "People say, 'Did you sleep?' I say, 'I worked all night dreaming it.' I try, but I'll be honest: I can't imagine the event."
Their work is the culmination of a five-year project in which the USGS has drilled six holes probing the crater's landscape. This hole will be the program's deepest, and the last, officials say.
Since the formal announcement in 1995 of what is now called the Chesapeake Bay Impact Crater, studies have detailed its dimensions and outline, experts say. Last year scientists for the first time found rock that had been melted by the impact and fossils of microorganisms that had been smashed in the event.
There are scores of known impact sites around the world and millions more on planets and moons across the solar system. The one near Norfolk is Earth's seventh-largest site and the biggest in the United States.