Rare meteorite impact site discovered in Inver Grove Heights

Rare meteorite impact site discovered in Inver Grove Heights

A rare meteor crash site has been discovered in Inver Grove Heights – the first discovered 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 University of Minnesota geologist and researcher Julia Steenberg. “It’s a bit like a breath of fresh air to find and discover something new.”

There are around 190 confirmed sites worldwide, including around 30 in the United States.

“We are geology enthusiasts and it really excites us,” said Tony Runkel. chief geologist for the Minnesota Geological Survey, who said the site was “for sure” one of the most intriguing finds in his 33 years with the survey.

The crater below Inver Grove Heights is about 2.5 miles wide and could span 9 square miles in all. It dates back about 490 million years, said Steenberg, who grew up in Dakota County.

The crater itself is hidden several hundred meters underground under sediment and cannot be seen by the human eye, she said.

Scientists from the Minnesota Geological Survey, the research arm of the U.S. School of Earth and Environmental Sciences, discovered the meteorite impact site in early 2021 as they updated geological maps of Dakota County. They named it Pine Bend Impact, after the area in Inver Grove Heights where it was found, Steenberg said.

Beneath most of the state’s soil are flat layers of glacial sediments. Beneath the glacial layers are sandstone, limestone and shale. As scientists worked at Inver Grove Heights, they found that the layers, which are usually stacked in a predictable pattern, were out of order and some layers appeared to be knocked over.

“The more I looked at the records in this area, the more they made no sense,” Steenberg said.

She remembers locating tiny, fractured grains of sand known as shocked quartz – a common identifier for a meteor impact. The grains are only created by the dramatic shock and compression of a meteor impact or nuclear explosion, she said.

Most of the time, meteors burn up before hitting Earth — but sometimes a collision does occur, Steenberg said.

“There is such intense pressure associated … that it produces instantaneous geological effects,” she said.

For verification, Steenberg sent photos and sediment samples to the Museum of Natural History in Vienna, Austria, and to the Institute of Geosciences at the University of Brazil. They confirmed that it was in fact shocked quartz.

Researchers are learning about the site and want to determine the exact size of the meteor, Steenberg said, adding that the U hopes to secure funding for the work. They plan to publish their findings and maps soon, she added.

Because the site was newly discovered, it is not yet included in the official Earth Impact Database, although researchers hope it will be added, she said.

In the Upper Midwest, impact sites have been found in Wisconsin, North Dakota and Iowa. Rock Elm Crater in western Wisconsin, midway between the Twin Cities and Eau Claire, is the closest known crater to Minnesota. It measures about 3.7 miles in diameter and is slightly younger than the Pine Bend Impact, Steenberg said.

Amy Looze, spokeswoman for Inver Grove Heights, said residents were thrilled to count Pine Bend’s impact as a piece of the town’s history.

“We are thrilled, intrigued and relieved by Ms. Steenberg’s discovery,” Looze said in an email. “Glad that [we] could become an important 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 ever hitting our city.”

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