[meteorite-list] Meteor Buffs Promote Impact Crater in Tennessee

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun, 11 Feb 2007 18:55:07 -0800 (PST)
Message-ID: <200702120255.SAA21616_at_zagami.jpl.nasa.gov>

http://www.rctimes.com/apps/pbcs.dll/article?AID=/200702

Meteor buffs hope to make strike town's claim to fame
By LEON ALLIGOOD
Tennessean
February 11, 2007

ERIN, Tenn. - Nina Finley and Bob McKinnon are not ones to avoid the
obvious.

Finley, a former Houston County schoolmarm who ended her career as
county school superintendent, and McKinnon, retired from the lumber
business, have earned a reputation for promoting local history in their
hometown with its Irish name.

The pair think alike, and it is obvious to both that the story of one of
the area's most fascinating events is under-appreciated.

"People don't seem to acknowledge the immensity of what happened here,"
said Finley, a reed-thin woman whose speech is laced with the kind of
Southern accent that Hollywood actresses of a certain age try to imitate
but often fail to project.

"I mean, it was big," drawled Finley.

Indeed, what happened about 200 million years ago in Houston and Stewart
counties was extraordinary.

A meteor believed to be at least 10 football fields long entered the
Earth's atmosphere traveling at 20 miles per second. With the force of
an atomic bomb, it gouged a crater an estimated four miles wide and up
to 2,000 feet deep.

"We can't imagine what it was like when that thing hit," said McKinnon,
a man who wears a perpetual thin smile on his face.

The concussion of the strike prompted an upward movement of massive
amounts of rock as the shockwave was telegraphed underground, circling
the epicenter for a distance of several miles.

"BIG," repeated Finley.

Forget "Erin go bragh."

On that explosive day, it was Erin go boom.

Prehistoric boomtown

"It was a unique event," said Richard Stearns, a retired Vanderbilt
University geology professor who, in 1968, published what has been
called the definitive book on the subject.

As meteorite landing sites go, the Wells Creek Basin, as it is
officially called, is certainly the largest of four strike sites in
Tennessee and is "in the middle" of impact sites worldwide, Stearns said.

According to the Impact Database of the University of New Brunswick in
Canada, the smallest diameter of the strikes is 49 feet in Kansas, while
the largest is 186 miles in South Africa.

Wells Creek Basin was not discovered until surveyors and engineers for
the now-defunct Memphis, Clarksville and Louisville Railroad tromped
through Houston County to plot the path of the coming track. They
reported finding layers of rocks that were jumbled, some standing on
end, contrary to the horizontal seams of rock found everywhere else.

Stearns said the state geologist at the time, James Safford, inspected
the site in the late 1850s and made known the discovery. On an official
state map, drawn up circa 1860 but not published until after the Civil
War, Safford placed a mark at Wells Creek Basin.

Soon enough, geologists began to poke around. Some believed the site was
"cryptovolcanic," the unsettling done eons earlier by an active volcano.
But scientists eventually came to accept that it was the work of a
meteorite.

A volcano would have to be especially active over a very long time span
to create the kind of damage to the earth's surface, Stearns said. A
crashing meteor is more plausible.

"Rock that is exposed at Wells Creek is normally about 2,000 feet under
the ground, so an enormous amount of rock was lifted up into the air. To
do that with a volcanic explosion, there would have to be a whole series
of volcanic events," he said.

'Rocks' are hard evidence

The presence of shatter cones, usually hand-sized rocks that are altered
by the shockwaves of the impact, is also a sign of a meteor impact.
These rocks are cone- or fan-shaped, with fracture lines that resemble
horsetails. Shatter cones indicate a rock has been shattered by the
blast and are a product of high pressure and a high-velocity shockwave.

"Don't call 'em rocks. They're not just rocks," McKinnon said.

They are proof, he said.

>From the back seat of Finley's SUV, the tall man lowered his head to
look out the window at passing countryside as they drove along a flat
lane near the Houston-Stewart county line.

A few miles away the land sloped upward in a broken ring of hills around
the center. Except for the sentinel-like smokestacks of the Cumberland
City coal-fired steam plant looming to the north, the view was pastoral,
and pasture-al.

"Now this is your epicenter," said Finley, pointing to the field.

"Yeah, the cows are right where the meteor was, and they don't even know
it," McKinnon added.

Therein lies the rub for these pair of meteorite history fans. The
pounding of the elements and the passage of time have smoothed the scar,
making the impact site look like, well, like nothing special ever happened.

"It's a hard sell to tourists," McKinnon said.
Received on Sun 11 Feb 2007 09:55:07 PM PST