Midcontinent Rift System
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The Midcontinent Rift System (MRS) is a 2000 km. long geological rift going from central Michigan into Lake Superior, then turning and going through Minnesota, Iowa, Nebraska and Kansas. It is approximately 1,100 million years old. Near Lake Superior, rocks produced by this rift can be found on the surface of the planet, but further south, the rift is buried thousands of feet below. It has been mapped primarily by gravity anomalies - its dense basaltic rock increases gravity locally. Aeromagnetic and seismic data are also used in the mapping process. When sufficiently deep drilling (usually commercial drilling for petroleum) makes actual rock samples available, these are used to test interpretations of the data mentioned above.
The MRS is also called the Keweenawan Rift.
