[meteorite-list] Drilling Continues at Chesapeake Bay Crater

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Tue Jun 1 19:07:12 2004
Message-ID: <200406012307.QAA17420_at_zagami.jpl.nasa.gov>

http://story.news.yahoo.com/news?tmpl=story&cid=624&ncid=624&e=1&u=/ap/20040601/ap_on_sc/chesapeake_bay_crater

Drilling Finds Crater Beneath Va. Bay
Associated Press
June 1, 2004

CAPE CHARLES, Va. - Geologists drilling half a mile below Virginia's
Eastern Shore say they have uncovered more signs of a space rock's
impact 35 million years ago.

For more than two weeks, scientists drilled around the clock
alongside a parking lot across the harbor from Cape Charles.
They stopped at 2,700 feet.

>From the depths came jumbled, mixed bits of crystalline and
melted rock that can be dated, as well as marine deposits, brine
and other evidence of an ancient comet or asteroid that slammed
into once-shallow waters near the Delmarva Peninsula.

Cape Charles is considered Ground Zero for the resulting
56-mile-wide depression below what's now the Chesapeake
Bay. The drilling project marks the first time the geologists
explored the inner portion of the inverted-sombrero-shaped
crater.

"We expected to see some pretty strange rocks because of the
extreme pressure and temperatures that occurred" approximately
35 million years ago, said geologist Greg Gohn, who led the
$180,000 project for the U.S. Geological Survey.

Over the past decade, USGS and Virginia scientists have
investigated indications that a 2-mile-wide brilliant ball
traveling tens of thousands of miles per hour crashed off the
Virginia coast, burrowing thousands of feet and depressing and
fracturing the bedrock.

Billions of tons of ocean water vaporized. Millions of tons of
debris spewed 30 miles high before collapsing back into the
excavation. A train of giant waves inundated the land. The
waves then dragged debris as they washed back into the crater,
preserving it beneath a blanket of rock and sediment.

It probably took just a few minutes to create the largest crater
in the United States and sixth-largest known on the planet,
according to computer simulations.

The catastrophe squeezed freshwater from many of the aquifers of
southeastern Virginia and filled others with briny water. Its
legacy is well-known to residents who try to drill for drinkable
groundwater and encounter the saltwater "wedge," pockets of
brine nestled in an arc from the lower Eastern Shore to the
Hampton Roads-Newport News area.

Geological research off the coast of New Jersey and in Virginia,
begun in 1983, led to the crater's discovery a decade later.
Drilling and further study of seismic data narrowed the location
in the Chesapeake Bay.

"We're getting evidence about how hot this thing (was) and what
was the energy," said USGS hydrologist David Powars, one of
those credited with the crater's discovery.

More clues to the space rock's identity will come from cores taken
in the drill's final 280 feet.

A $1.2 million proposal to dig 7,000 feet not far from Cape Charles
is before the International Continental Scientific Drilling Program,
which would then assist the USGS with funding.
Received on Tue 01 Jun 2004 07:06:57 PM PDT


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