...and now ... the rest of the story.

A crack forms in Michigan’s Upper Peninsula 

By Dan La Ponsie, 8 October, 2010, 7 Comments

200 yards long, 5 feet deep in parts.

UPDATES at bottom of the post. (Last updated: Oct 12.)
A large crack can evoke something ominous and unsettling. They are like the door at the end of the hallway that is only partially open — nagging at you to find out where it came from and what lies just beyond the opening. There is something alien about the sudden arrival of a crack.
These are the very sorts of feelings gripping residents of a small town in Michigan’s upper peninsula. A crack has arrived, accompanied by tremors, in Menominee Township — right at the southern part of the base of Michigan’s upper peninsula. View Map
The crack isn’t noticeably growing bigger — and it has a long way to go if it’s going to turn the peninsula into an island. So rather than being afraid, local residents are simply scratching their heads and wondering where it came from. A team of researchers are expected to investigate soon.
Fortunately, the crack didn’t swallow up anyone’s home. It runs through a woodland. No one was reported injured.
An article at Upper Michigan Source has comments from residents who reported the tremor that announced the arrival of the mysterious crack:

It all started early Monday morning between 8 & 9 a.m. Central time, when Eileen and her neighbors heard a loud boom, and that’s when Eileen felt her house start to shake.
“I heard something, but I was concentrating more on the chair moving than I was listening,” Eileen explained. “It was just moving back and forth, like I had a vibrating chair, which I don’t have.”
Later on, Eileen told her friend, Doug Salewsky, what happened. On Tuesday, he stumbled upon the crevice a short distance away in the woods and later called the state police.
But what caused this unusual event? An earthquake? A sink hole? Authorities say, at the moment, no one seems to know.
“It’s a pretty remarkable sight really,” said MSP Trooper, Paul Anderson. “Everyone will speculate I’m sure. There are probably a hundred different opinions out there as to what caused this, but at this time, we don’t know what caused this.”
The U.S. Geological Survey along with Michigan Tech professors have been called to help “crack” the case. Until then, it remains a mystery.

A local FOX News, from WLUK, article reports that the crack has become something of a local tourist attraction. It also mentions that, while local residents felt tremors, there were no reported earthquakes.

Nestled just beyond the tree line of Eileen Heider’s 53 acres, is Menominee County’s newest tourist attraction. “It’s amazing, I want to get back there and check the rest of it out,” said Kevin Clermont of Wallace, Michigan, who stopped on his way home from work to sightsee.
Heider and neighbors heard an explosion-like sound Monday morning. Heider found the nearly 200-yard-long crevice, which measures five-feet deep in parts, Tuesday. “I was sitting in my recliner and the recliner started to vibrate,” said Heider. “And it’s not electric.”
Trooper Paul Anderson with Michigan State Police was the first to check it out. He said he ruled out a gas line leak, but could not determine much more. “This would be a first,” he said. “You don’t learn that at the academy.”
Anderson said he called some geological experts. So far none have come to look at the crevice.
There have not been any reported earthquakes in the area.

According to an article at WWLP, the crack is ”up two feet wide and five feet deep” in some parts.

A large unexplained crack now runs 200 yards through the Salewsky family’s property, eight miles north of Menominee in Birch Creek.
The family thinks it happened Monday around 9:00 in the morning. The ground raised five feet up, taking trees along for the ride. Some cracks were
“The house shook, the chairs shook,” Doug Salewsky said. “The logs weren’t there when I piled them.”

UPDATE — Oct 12:
There’s an article at mtu.edu titled “Menominee County Shakeup was an Earthquake, says Tech Researcher.” This is only a portion of the article, the entirety of which is available online.

That shaking and loud noise experienced recently in Menominee County of Upper Michigan was indeed an earthquake, albeit a small one, according to a Michigan Tech researcher.
“The large crack and ridge were created most probably by a magnitude 1 or 2 earthquake,” said Wayne Pennington, chair of geological and mining engineering and sciences, of the events that took place Monday, October 4.
The ridge and crack are 361 feet long, and the ridge is 4 to 5 feet high and 20 to 30 feet wide at its largest point, Pennington said after visiting the site. The crack is 2 feet wide and 4 to 5 feet deep at its largest point. Trees are tipped away from the crack at about 14 degrees on either side, showing that the surface is now tipping, having formed the ridge.
That ridge, according to Pennington, is the most informative feature, not the crack. Residents report that this ridge was not there earlier, and it appeared at the same time as the crack.
“The most-likely explanation is that the underlying limestone has faulted in a manner that has pushed rock on one side of the fault up and over the rock on the other side—a ‘reverse’ or ‘thrust’ fault,” said Pennington. “The limestone is hard and brittle, and this movement can be described as the small earthquake that was felt.
Overlying the limestone is about 20 feet of soft clay, he said. This clay will deform in a “mushy” manner, rather than breaking along a fault. It ends up being pushed together, and this is what formed the ridge.