The 2012 Great Lakes volcanic eruptions were a series of unusual volcanic eruptions that took place in the Great Lakes of North America from July 6 to December 8, 2012. The first to form was Chicago Island, northeast of Chicago in Lake Michigan. The largest of the eruptions was a VEI-4 eruption that destroyed the Mackinac Volcano, which, in turn destroyed the Mackinac Bridge, killing nearly a thousand when it collapsed. The main cause of the eruptions was a weakening of the earth's crust, which allowed mantle plumes to 'punch' through the crust throughout the region, creating nearly a fifty hotspot volcanoes all across the Lakes, all of which would remain active for thousands of years. A major shift of the Great Lakes Tectonic Zone, marked by the Chicago earthquake, is believed to be the main 'trigger' for these eruptions.