The people near Birch Creek, Michigan, heard a boom in 2010 and felt the earth rock. On waking up the next morning they discovered a big crack in the ground. At that time nobody knew what caused it but now a group of researchers believe they know.

The thing that happened on the night of October 4th, 2010 left a big crack in the ground in the Upper Michigan Peninsula. It wasn’t an earthquake. The ground did move, but created the equivalent of a 1.0 magnitude earthquake. In the region there aren’t any geological faults.

The ground got split due to some other geological event, and the Michigan Technology University researchers now think that it was an event known as a ‘pop-up’.

The first sign was the fact that the split took place at a ridge top. A pop-up isn’t a pulling apart of some deep underground structure, in fact is a huge part of ground all of a sudden pushing upwards, making the ground over it to split.

They have found the pop-up using the sophisticated technique of knocking a sledgehammer against a metal ball present on the ground. As a result of the action, sound waves moved across the rock beneath. Based on the rock formation the sound moves at distinct speeds.

In this case, it stirred in immensely different ways parallel to the crack, in comparison to perpendicular to the crack, indicating that there was a big fracture in the limestone beneath the crack.

The occurrence of such sudden fractures takes place because of extreme strain in the rock, strain that can be pent up for so many years. Such an action is quite common around quarries, when removal of huge rock pieces can cause the rest to fracture and pop upwards all of a sudden. In rest of the times, it can occur spontaneously.

Now known as the Menominee Crack, it was possibly the outcome of a spontaneous fracture, though the researchers wonder it could have happened because of the removal of a huge tree from the region.