Ancient Earthquakes Leave Tracks from Kentucky to New York
Date: Nov. 14, 2000
By: Chris Curran
Phone: (513) 556-1806
Archive: Research News
Images by: Colleen Kelley and Patrick McLaughlin
Cincinnati -- A team of geologists from the University of
Cincinnati will present evidence that powerful Ordovician
earthquakes caused similar damage across a wide range of what is
now the eastern United States.
Professor Carlton Brett,
graduate students Patrick McLaughlin and Sean Cornell, and
undergraduate Alan Turner will present their findings Tuesday,
Nov. 14 during the annual meeting of the Geological Society of
America in Reno.
While a faculty member at the University of
Rochester, Brett spent many years studying rock beds of same age
(about 450 million years old) in the Mohawk Valley of New York,
include highly deformed sediments. After joining the UC faculty,
he and his students began examining the Ordovician deposits of
southwest Ohio and northern Kentucky. The patterns of deformation
were surprisingly similar.
"One of the interesting things is
the widespread distribution of these deformed beds," said Brett.
"We see the same kinds of folding and fracturing from Frankfort
to Lexington and northeastward to Augusta and Maysville" in
Kentucky. The formations can also be found across the Ohio River
near Moscow and New Richmond, Ohio.
"We're seeing these
patterns in an area that covers at least 50,000 square miles,"
remarked Brett. "That's an enormous area, and evidence that these
were very large earthquakes, probably with a magnitude from 7 to
9 on the Richter Scale."
Meanwhile, similar large quakes were
shaking the ground from eastern Virginia through upstate New
York. Brett believes the quakes stemmed from the same tectonic
forces that created the Taconic mountains in the northeastern
United States. The process of mountain-building known as
"orogeny" may have activated old faults according to
Brett, who emphasized those faults pose virtually no risk today.
"It's intriguing that you see similar effects 700 miles
away," said Brett. The common cause? The collision of North
America with a volcanic island chain. "Huge blocks of ocean floor
sediment were being thrust upon the eastern edge of North
America, forming the rising Taconic mountains."
aspects of his research, Brett works to understand how large-
scale events have impacted life on Earth. Surprisingly, many
large regional crises such as the huge earthquakes or widespread
volcanic ash burial don't appear to lead to catastrophic
extinctions. "Organisms appear to be very resilient to these
kinds of events," said Brett.
Brett has found evidence for
long periods of stability or near equilibrium in the history of
life. He believes it takes a combination of much larger
catastrophic events (usually combinations of sea level, climate
change and other major crises) to push life out of what he calls
"coordinated stasis" into a period of rapid extinction and
"The common theme seems to be some kind of
accelerated change after long periods of little change. And an
increased frequency of disturbances may increase the risk that
change will occur."