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The Midcontinent Rift System (MRS) or Keweenawan Rift is a 2,000 km (1,200 mi) long geological rift in the center of the North American continent and south-central part of the North American plate. It formed when the continent's core, the North American craton , began to split apart during the Mesoproterozoic era of the Precambrian , about 1.1 ...
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One billion years ago, the Midcontinent Rift System began to extend along a 2,000 kilometres (1,200 mi) path, [10] across both the Canadian Shield and the Stable Platform. The rift failed, then crustal movement reversed. A range formed then eroded, forming basins on either side of a horst.
Iowa magnetic anomaly map showing the Midcontinent Rift curving from the north center to the southwest part of the state. [8]Buried deeply within Iowa's bedrock, the Midcontinent Rift System can be seen clearly in magnetic anomaly maps of Iowa.
The Midcontinent Rift is the largest-known continental rift in the world. The rift began as a hot spot of basaltic magma underneath the Lake Superior region; it extruded layers of lava up to 20 km (12 mi) thick and extending up to 100 km (60 mi) on either side of the rift. The deposited lava along the North Shore of Lake Superior is 7,620 m (5 ...
Members of the Keweenawan Supergroup are exposed at the surface only in the Lake Superior region, particularly at the perimeter of the Midcontinent Rift System. To the southeast and southwest, they are covered by sedimentary rocks of Paleozoic age. At its thickest, the supergroup consists of about 20 kilometers (12 mi) of volcanic rocks ...
Over 1,100 mya, a rift formed and lava emerged from cracks along the edges of the rift valley. This Midcontinent Rift System extended from the lower peninsula of Michigan north to the current Lake Superior, southwest through the lake to the Duluth area, and south through eastern Minnesota down into what is now Kansas. [5]
The fault thrusts lava flows of the Midcontinent Rift System onto sedimentary rocks of the Jacobsville Sandstone. The fault is part of the inversion of the Midcontinent Rift where a region that had previously undergone extension experienced significant contraction. This contraction occurred during the final stages of the Grenvillian orogeny. [2]