Scientists Say Massive Meteorite Hit Wisconsin
By Juliet Williams
Scientists years ago saw something different about rocks
at Waverly, Wisconsin and concluded an ancient catastrophic
event occurred, although what type of calamity remained a mystery.
They believe they have finally solved the puzzle: A 650-
to 700-foot meteorite crashed into the earth at speeds up to 67,500 mph.
The impact 450 million years ago dislodged rocks and created
a massive hole in a 4-mile area called Rock Elm about 70 miles east of Minneapolis,
three scientists said in an article published in the Geological Society of America Bulletin.
Over time, shale, dirt and sediment filled the hole to
make the impact site virtually indistinguishable from the surrounding land. A shallow sea covering Wisconsin at the time of the impact likely blunted the meteorite's effect.
The report said the impact at Rock Elm released more than
1,000 megatons of explosive energy, lifted the earth at the center more than 1,650 feet and sent shock waves through the rocks,
"They were at ground zero, so they got the brunt of it,"
said William S. Cordua, of the University of Wisconsin-River Falls, and one of the paper's authors.
The confirmation of what happened here millions of years
ago is significant to geologists seeking to trace geological patterns, said Don Yeomans, an astronomer at NASA's Jet Propulsion
Laboratory in Pasadena, Calif.
Although they're not spectacular looking, to Cordua and
other scientists the rocks here have always appeared different than those just a few miles away. They're tipped at an angle
in many places, reflecting the damage inflicted millions of years ago.
Worldwide, there are only about 200 such impact formations,
and only a couple dozen in the United States.
They are believed to have occurred only every few hundred thousand years.
The first modern indication of anything wrong here came
in 1942, when a UW-Madison graduate student spotted the differences in soil and quartz and mapped out the area for more study.
"Mostly after its discovery it was pretty well ignored,"
said Bevan M. French, a former NASA geologist who is a research collaborator at the Smithsonian Institution. Even so, the
area has been known among amateur geologists and farmers as an anomaly.
Since the 1980s, Cordua has trudged through grassy fields
and muddy bogs looking for answers about Rock Elm. He started writing about the formation in 1985, and although he suspected
it was formed by a meteorite, he couldn't prove it.
"What I've been trying to do is hope that people who study
more of these things would get interested in it. And that finally happened," Cordua said.
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