Great Lakes tectonic zone southern Ontario. Several earthquakes have been documented in Minnesota in the last 120 years, with at least six in the GLTZ. The epicenters show a clear relationship to tectonic features of the state; four epicenters lie along the Great Lakes tectonic zone. Depths are estimated at . The best-documented event occurred on July 9, 1975, near Morris, Minnesota, with a magnitude of 4.6, and a felt area of covering parts of four states. Wisconsin has had no earthquakes along the GLTZ, Michigan's Upper Peninsula has had four earthquakes in the vicinity of the GLTZ – Negaunee, Newberry and two in
Great Lakes on Lake Ontario's northeast shore. Related to the lake effect is the regular occurrence of fog over medium-sized areas, particularly along the shorelines of the lakes. This is most noticeable along Lake Superior's shores. The Great Lakes have been observed to help intensify storms, such as Hurricane Hazel in 1954, and the 2011 Goderich, Ontario tornado, which moved onshore as a tornadic waterspout. In 1996 a rare tropical or subtropical storm was observed forming in Lake Huron, dubbed the 1996 Lake Huron cyclone. Rather large severe thunderstorms covering wide areas are well known in the Great Lakes during mid-summer; these