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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 ...
The river is the result of geologic forces going back 1.1 billion years. At that time, the Mid-Continent Rift rendered the middle of North America apart, creating a volcanic zone. The lava spewed forth cooled into hard basalt. That basalt is what today creates the dramatic cliffs around the Interstate State Parks.
Structures of Kansas showing the Nemaha Uplift/Ridge. The Nemaha Ridge (also called the Nemaha Uplift and the Nemaha Anticline [1]) is located in the Central United States.It is a buried structural zone associated with a granite high in the Pre-Cambrian basement that extends from approximately Omaha, Nebraska to Oklahoma City, Oklahoma.
The Keweenawan Supergroup is a supergroup of volcanic and sedimentary rocks that fill the Midcontinent Rift System in the U.S. states of Michigan, Wisconsin, and Minnesota. [1] [2] It is about 30 kilometers (19 mi) thick and it formed about 1.1 billion years ago. [3]
Bedrock geologic map illustrating the main geologic regions of Minnesota. Igneous bodies lie across the northern half of the state, with intrusions throughout the northwest and basalts and other igneous rocks of the Duluth Complex and Beaver Bay Complex from the Midcontinent Rift System bordering Lake Superior in the northeast.
Mid-continental Rift System. Items portrayed in this file depicts. inception. 5 December 2023. media type. image/webp. File history. ... Midcontinent Rift System;
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]
Lake Tanganyika, second by both measures, is in the Albertine Rift, the westernmost arm of the active East African Rift. Lake Superior in North America, the largest freshwater lake by area, lies in the ancient and dormant Midcontinent Rift. The largest subglacial lake, Lake Vostok, may also lie in an ancient rift valley. [5]