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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 Newark Supergroup, also known as the Newark Group, is an assemblage of Upper Triassic and Lower Jurassic sedimentary and volcanic rocks which outcrop intermittently along the east coast of North America. They were deposited in a series of Triassic basins, the Eastern North American rift basins, approximately 220–190 million years ago.
The landforms of Earth are generally divided into physiographic regions, consisting of physiographic provinces, which in turn consist of physiographic sections, [1] [2] [3] though some others use different terminology, such as realms, regions and subregions. [4]
Most included all of North America without regard to political subdivision. Fenneman expanded and presented a derivative of this system more fully in two books, Physiography of western United States (1931), [7] and Physiography of eastern United States (1938). [8]
A physiographic province is a geographic region with a characteristic geomorphology, and often specific subsurface rock type or structural elements. The continents are subdivided into various physiographic provinces, each having a specific character, relief, and environment which contributes to its distinctiveness.
The rift zone known as the mid-Atlantic ridge continued to provide the raw volcanic materials for the expanding ocean basin. [20] North America was slowly pulled westward away from the rift zone. The thick continental crust that made up the new east coast collapsed into a series of down-dropped fault blocks that roughly parallel today's coastline.
On a map showing only metamorphic rocks, the Canadian Shield forms a circular pattern north of the Great Lakes around Hudson Bay.. The Canadian Shield is a large area of Archean through Proterozoic igneous and metamorphic rocks in eastern Canada and north central and northeastern United States.
At the BFZ's eastern end, near the Steens Mountain fault, the zone of surface faulting turns slightly to the south-southeast (possibly due to rotation of Nevada), then follows the Northern Nevada Rift to form the Oregon–Nevada lineament, with a total length of over 75 km (47 mi).