[meteorite-list] Scientists Delve Into Chesapeake Bay Crater's Mysteries

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:07:05 2004
Message-ID: <200210301739.JAA00406_at_zagami.jpl.nasa.gov>

http://www.pilotonline.com/news/nw1030tri.html

Scientists delve into Bay crater's mysteries
By DIANE TENNANT
The Virginian-Pilot
October 30, 2002

A volcanic plug in western Virginia is the same age as the Chesapeake Bay
impact crater, prompting a geology professor to speculate that the comet or
meteor crash awakened magma 200 miles away.

In a presentation today to the Geological Society of America, Rick Diecchio
of George Mason University will discuss the possible relationship of Trimble
Knob, Virginia's hot springs and the drainage divides of major rivers to the
enormous hole under the Chesapeake Bay.

Interest in the crater is spreading as scientists continue studying it. The
GSA is devoting an entire morning to it, with at least 12 presentations on
the topic. One of them will be Diecchio's.

Trimble Knob is a basalt plug formed when molten rock hardened underground.
It is just south of Monterey in Highland County, near the West Virginia
line.

The most recent volcanic activity in Virginia was about 45 million years
ago. But Trimble Knob is only 35 million years old, the same age as the
crater.

The Chesapeake Bay impact crater was created when a meteor or comet 2 miles
wide blasted into the shallow sea at what is now Cape Charles, excavating a
hole a mile deep and 56 miles wide. Although it is now buried under hundreds
of feet of sand and dirt and water, the crater still causes problems for
Hampton Roads. It disrupted water aquifers, trapped salty seawater and
cracked the bedrock. Maybe it did more.

Perhaps, Diecchio said, the impact realigned the plumbing underground as far
as 200 miles away, opening cracks that allowed hot water and hot rock to
rise again.

Trimble Knob sits on the drainage divide -- high ground that causes water on
one side to flow in one direction and water on the other side to flow
another way -- between the Potomac and James rivers. It is only a short
distance from the Eastern Continental Divide, which sends water toward the
Ohio River or the Chesapeake Bay.

``If you take a map of all the rivers on the East Coast, it doesn't take
much to imagine a circle that goes from the southern edge of Pennsylvania
down to the Carolina coast,'' Diecchio said. ``The circle has spokes. The
spokes are the drainage divides between the Susquehanna and the Potomac, and
the Potomac and the York, and the York and the James, the James and the
Roanoke. You have this pattern that seems to center on the impact. It seems
as plain as the nose on your face. But just looking at a map and drawing
lines doesn't constitute a cause and effect.''

Hot and warm springs run along the Appalachians, from Pennsylvania through
Berkeley Springs in West Virginia to the famous Homestead resort in western
Virginia. They lie along Diecchio's imaginary circle, centered on the impact
crater.

The impact would not have heated the water, Diecchio said, but it could have
reopened old faults or created new ones that allowed the water to reach the
surface. Perhaps it allowed magma to rise again as well, creating Trimble
Knob, which also lies on the circle.

Raising questions may prompt more study, Diecchio said, which could provide
answers. One puzzle he hopes to examine further is a waterfall just north of
Covington called Falling Springs. It comes from a hot spring on the
mountainside and, as it falls, it loses carbon dioxide. This forms a mineral
deposit called travertine, the same substance that makes drip formations in
caves.

It makes stalactites behind the waterfall and even coats logs and rocks and
beer cans, he said.

It would be interesting, Diecchio said, to drill a core hole into the
travertine to see whether it dates to the time of the impact.

``These are all questions. There are no answers here,'' he said. ``I could
be all wet. But it sure is intriguing.''

Reach Diane Tennant at 446-2478 or dianet_at_pilotonline.com
Received on Wed 30 Oct 2002 12:39:32 PM PST