U.S. Water News Online
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
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 fresh water 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
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
"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 drill 7,000 feet not far from Cape
Charles is before the International Continental Scientific Drilling
Program, which would then assist the USGS with funding.
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