A rare meteorite crash site has been discovered in Inver Grove Heights, the first found in Minnesota, and researchers hope it will soon be added to the map of other known crash sites around the world.
“I look at rock samples all day and I’ve never seen anything like this before,” said Julia Steenberg, a geologist and research scientist at the University of Minnesota. “It’s like a breath of fresh air to find and discover something new.”
There are about 190 confirmed sites around the world, including about 30 in the United States.
“We’re geology nerds and we’re really excited about this,” said Tony Runkel. senior geologist at the Minnesota Geological Survey, who called the “safe” site one of the most intriguing finds in his 33 years with the study.
The crater below Inver Grove Heights is about 2.5 miles wide and could span more than 9 square miles in total. It dates to about 490 million years ago, said Steenberg, who grew up in Dakota County.
The crater itself is hidden several hundred feet underground under sediment and cannot be seen by the human eye, he said.
Scientists with the Minnesota Geological Survey, the research arm of the U’s College of Earth and Environmental Sciences, found the meteorite’s impact site in early 2021 while updating geologic maps of Dakota County. They named it the Pine Bend Impact, after the Inver Grove Heights area where it was found, Steenberg said.
Beneath most of the state’s soil are flat layers of glacial sediment. Beneath the glacial layers are sandstones, limestones, and schists. As the scientists worked at Inver Grove Heights, they saw that the layers, which usually stack in a predictable pattern, were out of order and certain layers appeared to be tipped over.
“The more I looked at the records in that area, they didn’t make any sense,” Steenberg said.
He recalled finding small fractured sand grains known as impacted quartz, a common identifier for a meteorite impact. The grains are created only by the dramatic shock and compression of a meteorite impact or nuclear explosion, she said.
Most of the time, meteors burn up before hitting Earth, but sometimes a collision does happen, Steenberg said.
“There is such intense pressure associated … that it produces instantaneous geological effects,” he said.
For verification, Steenberg sent photos and samples of the sediment to the Natural History Museum in Vienna, Austria, and to the Institute of Geosciences of the University of Brazil. They confirmed that it was, in fact, impacted quartz.
Researchers are learning about the site and want to find out the exact size of the meteorite, Steenberg said, adding that the U hopes to get funding for the work. They plan to publish their findings and maps soon, she added.
Because the site is newly discovered, it is not listed on the official site yet Earth Impact Databasethough researchers hope it will be added, he said.
In the upper Midwest, impact sites have been found in Wisconsin, North Dakota, and Iowa. Rock Elm Crater in western Wisconsin, roughly halfway between the Twin Cities and Eau Claire, is the closest known crater to Minnesota. . It’s about 3.7 miles in diameter and slightly younger than the Pine Bend Impact is thought to be, Steenberg said.
Amy Looze, a spokeswoman for Inver Grove Heights, said residents are excited to tell the Pine Bend Impact as part of the city’s history.
“We are pleased, intrigued and relieved by Ms. Steenberg’s discovery,” Looze said in an email. “Delighted that [we] could become a major geological site, intrigued that the discovery could give scientists more data they need to predict future meteor impacts on Earth and relieved that there is no statistical chance of another meteor hitting our city.”
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