The geological formation of the state is greatly varied, with the Michigan Basin being the most major formation. Primary boulders are found over the entire surface of the Upper Peninsula (being principally of primitive origin), while Secondary deposits cover the entire Lower Peninsula. The Upper Peninsula exhibits Lower Silurian sandstones, limestones, copper and iron bearing rocks, corresponding to the Huronian system of Canada. The central portion of the Lower Peninsula contains coal measures and rocks of the Pennsylvanian period. Devonian and sub-Carboniferous deposits are scattered over the entire state.
Michigan rarely experiences earthquakes, thus far mostly smaller ones that do not cause significant damage. A 4.6-magnitude earthquake struck in August 1947. More recently, a 4.2-magnitude earthquake occurred on Saturday, May 2, 2015, shortly after noon, about 5 miles south of Galesburg, Michigan (9 miles southeast of Kalamazoo) in central Michigan, about 140 miles west of Detroit, according to the Colorado-based U.S. Geological Survey's National Earthquake Information Center. No major damage or injuries were reported, according to Governor Rick Snyder's office.