A rare meteor 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 researcher at the University of Minnesota. “It’s like a breath of fresh air to find and discover something new.”
There are about 190 confirmed locations worldwide, including about 30 in the United States.
“We’re geology nerds and we’re really excited about that,” said Tony Runkel. senior geologist for the Minnesota Geological Survey, who said the site is “certainly” one of the most intriguing finds in his 33 years of surveying.
The crater under Inver Grove Heights is about 2.5 miles wide and could cover a total of 9 square miles. It dates to about 490 million years ago, said Steenberg, who grew up in Dakota County.
The crater itself is hidden under sediment several hundred feet underground and cannot be seen with the human eye, she said.
Scientists with the Minnesota Geological Survey, the research arm of the US School of Earth and Environmental Sciences, found the meteorite impact site in early 2021 while updating geological maps of Dakota County. They named it Pine Bend Impact, after the Inver Grove Heights area where it was found, Steenberg said.
Underneath most of the state’s soil are shallow layers of glacial sediment. Beneath the layers of glaciers are sandstone, limestone and shale. Working at Inver Grove Heights, scientists saw that the strata, which are normally stacked in a predictable pattern, were out of order and certain strata appeared to have tumbled.
“The more I looked at the records in that area, they just didn’t make sense,” Steenberg said.
She recalled finding tiny, broken grains of sand known as shocked quartz — a common identifier for a meteorite impact. The grains are formed 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 occurs, Steenberg said.
“There’s such intense pressure associated with it… that it creates immediate geological effects,” she said.
Steenberg sent photos and samples of the sediment to the Natural History Museum in Vienna, Austria, and to the Institute of Geosciences at the University of Brazil for verification. They confirmed that it was indeed shocked quartz.
Researchers are learning about the site and want to find out the exact size of the meteor, Steenberg said, adding that the U hopes to get funding for the work. They plan to release their results and their maps soon, she added.
Since the site was newly discovered, it is not yet included on the official website Earth Impact Databasealthough 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, about halfway between the Twin Cities and Eau Claire, is Minnesota’s closest known crater. It’s about 3.7 miles across and is slightly younger than the Pine Bend Impact it’s thought to be, Steenberg said
Inver Grove Heights spokeswoman Amy Looze said residents are thrilled to count the Pine Bend Impact as a piece of city history.
“We are delighted, intrigued and relieved by the discovery of Ms. Steenberg,” Looze said in an email. “That makes me happy [we] could become an important geological site, intrigued that the discovery could provide scientists with more data they need to predict future meteorite impacts on Earth, and relieved that there is no statistical chance another meteor will ever hit our city.