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Glasford Meteor May Have Played A Role in Ancient Ice Age

Photo by Christopher Korose for the Illinois State Geological Survey. \ Used With Permission
The Glasford fold shows how shale and rock was twisted and shaped by the impact of the meteor.

New research on a central Illinois crater suggests possible links to an Ice Age about 455 million years ago. 

Charles Monson is an assistant project coordinator with the Illinois State Geological Survey. He said his team's research suggests a ancient meteor about the size of Wrigley Field struck near Glasford, 20 miles southwest of Peoria, creating a 2.5 mile wide crater that's now buried under a more than a thousand feet of sediment. 

Scientists look for certain geologic signs like shatter cones (or altered rock) to prove a meteor impact is responsible for a crater, instead of another phenomenon. Monson said no one's taken a good look at the crater since its discovery more than 50 years ago. Using 21st century technology and methods, he said scientists were able to learn more. 

"We've documented some of those at the Glasford structure, much more thoroughly than they've been previously documented, so you could say we are the first ones to completely prove this was a meteor impact," he said. 

Monson said dating established through marine fossils suggests it may also have links to the Great Ordovician Meteor Shower, which bombarded Earth for around 30 million years. A study from Dr. Birger Schmitz of Lund University and the Field Museum suggests extraterrestrial dust linked to these meteor impacts may have drastically cooled Earth's climate. 

"If this new idea stands the test of time, that would indicate that not only is this Glasford meteor potentially tied to the Ordivician meteor shower, but also to this ice age that really kind of affected the course of evolution on Earth," Monson said. 

Most of Illinois was under a shallow sea at the time. Monson said that kind of impact would create a massive void that would soon refill with rushing water.

Fossils in the marine rocks in Glasford suggests the impact the meteor showers had on life at the time. 

The Glasford crater is one of just two known meteor craters in Illinois. The other is near Des Plaines.

Monson's is the first major study published about the Glasford crater since its discovery in 1963.It appeared in the October 2019 edition of the academic journal Meteoritics and Planetary Science.

Editor's note: The Glasford crater is about 1/5 of a mile under the surface, not a full mile as previously stated. Fossils were used to help date the meteor. Shatter cones were used to establish the crater was made by a meteor impact. 

Tim is the News Director at WCBU Peoria Public Radio.