U.S. Water News Online
RESTON, Va. -- In a former federal printing plant, Belgium
geologist Philippe Claeys hovered over the tables of rocks, some 600
million years old, hoping to find traces of an asteroid.
Claeys was among dozens of scientists from around the globe
descending on the U.S. Geological Survey to select samples of a
1.1-mile-long core, much of it granite, unearthed last fall from the
ancient crater under the Chesapeake Bay.
He and about two dozen other scientists from Finland, Austria,
Germany, Estonia and elsewhere strolled through the one-time printing
plant filled with open boxes of cores. In an atmosphere of a silent
auction, they wrote their names on slips of clear Mylar and tucked
them beside the desired rocks for project officials to sort through
and distribute later.
They were drawn to the USGS headquarters by the remains of what
geologists say was a fiery, 2-mile-wide space rock that blasted into
coastal Virginia more than 35 million years ago, carving a hole that
quickly filled with tons of water, rubble and debris.
"The only thing you could do to simulate the conditions of the
impact is a nuclear blast," said Greg Gohn, the USGS project leader.
Claeys, from the Free University of Brussels, wants to identify
the cause of the crater without setting off a nuclear explosion. He
suspects that the bay was a bystander to a major collision in the
asteroid belt between Mars and Jupiter.
Debris from that collision, he says, might have bombarded the
Earth not just in the Chesapeake Bay but in Siberia, Canada and
possibly other sites where craters from about the same time frame
have been found.
"What we have so far is pointing to an asteroid," he said.
He plans to study the ratio of platinum-related elements, a
telltale sign of a meteorite, in the Virginia cores. Comparing that
with the ratio found in other craters of the same age could nail the
culprit here in Virginia.
"Something that happens in the asteroid belt, between Mars and
Jupiter, can, in a short geologic time frame . . . send a whole bunch
of large projectiles towards Earth," he said. "That's a little bit
scary. We don't know when that's going to happen again."
Two of the crater project's principal investigators, Uwe Reimold
of Germany's Humboldt University and Christian Koeberl of the
University of Vienna, worked side by side, conferring over the
samples. Moving slowly from table to table, they scrutinized the
mostly gray and tan rock for samples to investigate the physical
processes involved in creating impact craters and how the rock was
Koeberl said he was convinced that new data from a much younger
and well-preserved crater in Ghana would help them interpret the
crater centered on Virginia's Eastern Shore.
They left a long trail of Mylar slips. Each scientist was limited
to 150 requests.
Both assisted in the drilling last fall, which ran nearly
continuously in Northampton County near Cheriton for almost three
months to remove 5,795 feet of cores.
The USGS paired with the International Continental Scientific
Drilling Program and NASA on the nearly $1.5 million project to drill
into the basement of the 53-mile-wide crater. The crater's epicenter
is Cape Charles.
Scientists expect the cores to reveal more about the effects the
prehistoric impact had on the region's geology and water supply and
to help better estimate the space rock's speed, size and energy as it
slammed into the seabed. Other scientists will study samples of
ancient water found in the cores that had been trapped in the
crater's depths by the impact's aftermath.
The crater is the largest of its kind in the U.S. and the
seventh-largest in the world. It is 1,000 feet beneath the lower part
of the bay, surrounding peninsulas and the intercontinental shelf of
the Atlantic Ocean.
The USGS plans to return this spring to the drill site to core the
top 412 feet to complete the record.
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