- Associated Press - Thursday, February 11, 2016

MENOMINEE, Mich. (AP) - Faculty and student researchers from Michigan Technological University believe they have figured out how a large crack opened in the ground more five years ago near the Michigan-Wisconsin border.

In October 2010, the ground shook in Menominee, Michigan, causing residents to think they were experiencing an earthquake.

“I was sitting watching television on my recliner, and I start moving. It was weird. Maybe only lasted 15 seconds, but it was moving,” Eileen Heider said, remembering the event like it was yesterday.

Since the Upper Peninsula isn’t known for its earthquakes, the university’s researchers have been studying the area in an effort to determine what caused 360-foot long crack on Heider’s property.

“When I got there I was completely shocked by what I saw,” said Wayne Pennington, a geophysicist who’s the dean of Michigan Tech’s College of Engineering.

Pennington knew right away that the crack wasn’t caused by a typical earthquake, and scientists say it didn’t register on a seismograph.

“The crack is remarkable, but the ridge, a six-foot-high ridge, the length of a football field. That doesn’t happen easily inside the earth,” he said.

The Michigan Tech researchers have determined that a geological pop-up occurred when underground pressure on the limestone rock in the area was released, allowing the crack to form, WLUK-TV (http://bit.ly/1Ljlrl8 ) in Green Bay, Wisconsin, reported.

“Usually it’s caused by the removal of a glacier. But the glacier left here 11,000 years ago. So why did it wait until 2010 to happen?” Pennington said.

There are other less likely theories as to what caused the pop-up, he said, adding that it’s a unique event.

“All the stress in that area has been relieved. If it was waiting 11,000 years for the final trigger, there’s not a lot more stress there waiting to happen,” Pennington said.

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