Michigan's Upper Peninsula isn't like California. No one is predicting it will break away and fall into Lake Superior. In fact the UP had never had an earthquake in recorded history - until the Menominee Crack opened up in 2010.

Just outside of Menominee, which sits on the shores of Lake Superior on the Wisconsin border, loud rumbling was heard and the earth shook on the morning of October 4, 2010. Local residents were very surprised to find a large crack in the ground. Scientists rushed to the area to see the mysterious and completely unexpected Menominee Crack. After 5 years of study, there are perhaps some answers as to what caused the ground to open up.

The geographic feature is known as a pop-up. As to why the ground popped up? Michigan Tech's Dr Wayne Pennington told Science Daily,

The limestone in the area may have been stressed almost to the point of cracking when the last glaciers retreated, they say. The recent removal of the double-trunked pine, which may have weighed as much as 2000 kilograms--over two tons--could have been the final straw, allowing the rock to bend upward when that weight was removed.

Pennington said "no one should be losing sleep" over the strange feature, which technically counted as the first natural earthquake in Michigan's Upper Peninsula--measuring less than magnitude 1.

"It may be a one-of-a kind phenomenon," he said. "But if it happens again, we'll be all over it, trying to figure it out."

This YouTube blogger captured footage of the crack just days after it occurred.

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[MTU.edu, ScienceDaily]