Five years after the abrupt appearance of a strange fracture in the Earth in a forest near Birch Creek on Michigan's Upper Peninsula, researchers were able to explain what it is.

Published in the journal Seismological Research Letters, the new study detailed a limestone bulge first discovered on the morning of Oct. 4, 2010. The fracture was preceded by a low, loud noise and a seismic event with the strength of a magnitude-1 earthquake, according to Live Science.

"We wanted to look into the crack because we could not find information in the literature on pop-up structures forming outside specific areas," study co-author Wayne Pennington, dean of the College of Engineering at Michigan Technical University, said in a press release. "As far as we can tell, this is a one-of-a-kind event; but in case it is not, we wanted the information about it to be available for other investigators."

Pennington conducted the research with a group of MTU students and the group concluded the upper layer of limestone broke and rose to form a ridge, though they could not pinpoint the reason for it.

"There are no nearby quarries, however," Pennington said. "There was a large tree that had been removed after it fell over and the timing certainly provides an interesting coincidence."