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 to apply for additional federal research and education funds allocated to these national resources. Following a small uproar, the Senate voted to revoke the designation on March 24 (although New York and Vermont universities would continue to receive funds to monitor and study the lake). In the early years of the 21st century, water levels in the Great Lakes were a concern. Researchers at the Mowat Centre said that low levels could cost $19bn by 2050. Except when the water is frozen during winter, more than 100 lake freighters operate continuously on the Great Lakes, which remain a major water