A group of researchers at the Michigan Technology University in Houghton found that a mystery phenomenon split ground in Michigan forest with a loud sound five years ago.
During the event, a long crack appeared in the soil, while nearby homes were shaken just like in a magnitude-1 earthquake. Nevertheless, earthquake experts said that their readings didn’t indicate any quake on Oct. 4, 2010. So, the phenomenon in the Birch Creek forest remained largely a mystery in the past years.
According to locals, the strange crack, also known as the Menominee crack was 360 feet long with a depth of five feet. Strangely, the crack was framed by uprooted trees on both sides, with many of them leaving torn roots behind. Because all trees were tilted at the same angle, scientists concluded that the crack was new.
Wayne Pennington, lead author of the recent study on the mystery crack, said that his team was puzzled by the force behind the event that apparently was stronger than the roots.
Since an earthquake was ruled out, MTU researchers believe that the split in the ground was caused by a rare geological phenomenon called a ‘pop-up.’ Study authors explained that a bulge occurred in the lower limestone layers, thus, causing a ridge in the upper clay layers and the crack we can see today.
A study on the mysterious phenomenon was published this week in the Seismological Research Letters.
Study authors based their findings on simulations conducted at the scene. They slammed a sledgehammer against a steel ball to create artificial sound waves in the ground. Next, the team looked at the underground layers of rock to see how sound waves influenced limestone layers.
Computer models showed that the limestone layer was cracked open by the violent pop-up. The event was so abrupt and violent that it displaced the 5-foot-thick clay layer above. As clay was stretching and going up, a crack appeared in the process. The process is very similar to the emergence of tiny cracks in bread dough’s surface as the dough rises.
Researchers also said that no quake was behind the crack since instruments recorded a jolt similar to one created by a magnitude-1 earthquake. But to create such a crack it would take a much stronger earthquake. Plus, the pop-up occurred in superficial layers, while quakes strike miles deep.
Nevertheless, the pop-up’s source in the Michigan forest remains largely a mystery since such pop-ups happen when either mining activities displace large amounts of rock or when glaciers retreat, which was not the case in our story.
Image Source: MTU