Interior Plains

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The Interior Plains are highlighted in red. NorthAmericaInteriorPlains.svg
The Interior Plains are highlighted in red.

The Interior Plains are a vast physiographic region that spreads across the Laurentian craton of central North America, extending from the Gulf Coast region to the Arctic Ocean along the east flank of the Rocky Mountains. In Canada, it separates the Rocky Mountains from the Canadian Shield, while in the U.S., it includes the Great Plains of the west and the Tallgrass prairie region to the south of the Great Lakes extending east to the Appalachian Plateau region. [1]

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 uniqueness. The physiographic provinces are then subdivided into smaller physiographic sections.

Laurentia A large continental craton that forms the ancient geological core of the North American continent

Laurentia or the North American Craton is a large continental craton that forms the ancient geological core of the North American continent. Many times in its past, Laurentia has been a separate continent, as it is now in the form of North America, although originally it also included the cratonic areas of Greenland and also the northwestern part of Scotland, known as the Hebridean Terrane. During other times in its past, Laurentia has been part of larger continents and supercontinents and itself consists of many smaller terranes assembled on a network of Early Proterozoic orogenic belts. Small microcontinents and oceanic islands collided with and sutured onto the ever-growing Laurentia, and together formed the stable Precambrian craton seen today.

North America Continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere

North America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It is also considered by some to be a northern subcontinent of the Americas. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.


Geology and physiography

This area was originally formed when cratons collided and welded together 1.81.9 billion years ago in the Trans-Hudson orogeny during the Paleoproterozoic Era.

Craton Old and stable part of the continental lithosphere

A craton is an old and stable part of the continental lithosphere, which consists of the Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates. They are characteristically composed of ancient crystalline basement rock, which may be covered by younger sedimentary rock. They have a thick crust and deep lithospheric roots that extend as much as several hundred kilometres into the Earth's mantle.

Trans-Hudson orogeny

The Trans-Hudson orogeny or Trans-Hudsonian orogeny was the major mountain building event (orogeny) that formed the Precambrian Canadian Shield, the North American Craton, and the forging of the initial North American continent. It gave rise to the Trans-Hudson orogen (THO), or Trans-Hudson Orogen Transect (THOT), which is the largest Paleoproterozoic orogenic belt in the world. It consists of a network of belts that were formed by Proterozoic crustal accretion and the collision of pre-existing Archean continents. The event occurred 2.0-1.8 billion years ago.

Paleoproterozoic Era (;), spanning the time period from 2,500 to 1,600 million years ago (2.5–1.6 Ga), is the first of the three sub-divisions (eras) of the Proterozoic Eon. The Paleoproterozoic is also the longest era of the Earth's geological history. It was during this era that the continents first stabilized.

Precambrian metamorphic and igneous rocks now form the basement of the Interior Plains and make up the stable nucleus of North America. With the exception of the Black Hills of South Dakota, the entire region has low relief, reflecting more than 500 million years of relative tectonic stability. [2]

Metamorphic rock Rock which was subjected to heat and pressure causing profound physical or chemical change

Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means "change in form". The original rock (protolith) is subjected to heat and pressure, causing profound physical or chemical change. The protolith may be a sedimentary, igneous, or existing metamorphic rock.

Igneous rock Rock formed through the cooling and solidification of magma or lava

Igneous rock, or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition. Solidification into rock occurs either below the surface as intrusive rocks or on the surface as extrusive rocks. Igneous rock may form with crystallization to form granular, crystalline rocks, or without crystallization to form natural glasses. Igneous rocks occur in a wide range of geological settings: shields, platforms, orogens, basins, large igneous provinces, extended crust and oceanic crust.

Black Hills mountain range in South Dakota and Wyoming

The Black Hills are a small and isolated mountain range rising from the Great Plains of North America in western South Dakota and extending into Wyoming, United States. Black Elk Peak, which rises to 7,244 feet (2,208 m), is the range's highest summit. The Black Hills encompass the Black Hills National Forest. The name "Black Hills" is a translation of the Lakota Pahá Sápa. The hills were so-called because of their dark appearance from a distance, as they were covered in trees.

The Interior Plains were often covered by shallow inland seas. Sediments from the shield and the Rocky Mountains were deposited in these seas over millions of years. Eventually, the sediments were compressed by the weight of the layers above into sedimentary rock. Part of the sedimentary rock deposited in these areas consists of coral reefs that formed close to the surface of seas during the Paleozoic Era. [1]

Western Interior Seaway A large inland sea from mid-Cretaceous to early Paleogene, splitting the continent of North America

The Western Interior Seaway was a large inland sea that existed during the mid- to late Cretaceous period as well as the very early Paleogene, splitting the continent of North America into two landmasses, Laramidia to the west and Appalachia to the east. The ancient sea stretched from the Gulf of Mexico and through the middle of the modern-day countries of the United States and Canada, meeting with the Arctic Ocean to the north. At its largest, it was 2,500 feet (760 m) deep, 600 miles (970 km) wide and over 2,000 miles (3,200 km) long.

Sediment Particulate solid matter that is deposited on the surface of land

Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sand and silt can be carried in suspension in river water and on reaching the sea bed deposited by sedimentation. If buried, they may eventually become sandstone and siltstone through lithification.

Rocky Mountains mountain range in North America

The Rocky Mountains, also known as the Rockies, are a major mountain range in western North America. The Rocky Mountains stretch more than 4,800 kilometers (3,000 mi) from the northernmost part of British Columbia, in western Canada, to New Mexico in the Southwestern United States. Located within the North American Cordillera, the Rockies are somewhat distinct from the Pacific Coast Ranges, Cascade Range, and the Sierra Nevada, which all lie farther to the west.

Paleozoic and Mesozoic

Throughout the Paleozoic and Mesozoic eras, the mostly low-lying Interior Plains region remained relatively unaffected by the mountain-building tectonic collisions occurring on margins of the continent. During much of the Mesozoic Era, the North American continental interior were mostly well above sea level, with two major exceptions. During part of the Jurassic, rising seas flooded the low-lying areas of the continent, forming the Sundance Sea; in the Cretaceous, much of the Interior Plains region lay submerged beneath the Western Interior Seaway. [2]

The PaleozoicEra is the earliest of three geologic eras of the Phanerozoic Eon. It is the longest of the Phanerozoic eras, lasting from 541 to 251.902 million years ago, and is subdivided into six geologic periods : the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. The Paleozoic comes after the Neoproterozoic Era of the Proterozoic Eon and is followed by the Mesozoic Era.

The Mesozoic Era is an interval of geological time from about 252 to 66 million years ago. It is also called the Age of Reptiles and the Age of Conifers.

Orogeny The formation of mountain ranges

An orogeny is an event that leads to both structural deformation and compositional differentiation of the Earth's lithosphere at convergent plate margins. An orogen or orogenic belt develops when a continental plate crumples and is pushed upwards to form one or more mountain ranges; this involves a series of geological processes collectively called orogenesis.


The Interior Plains continued to receive deposits from the eroding Rocky Mountains to the west and Appalachian and Ozark/Ouachita Mountains to the east and south throughout the era. The flatness of the Interior Plains is a reflection of the platform of mostly flat-lying marine and stream deposits laid down in the Mesozoic and Cenozoic eras. [2]

Appalachian Mountains mountain range in the eastern United States and Canada

The Appalachian Mountains, often called the Appalachians, are a system of mountains in eastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They once reached elevations similar to those of the Alps and the Rocky Mountains before experiencing natural erosion. The Appalachian chain is a barrier to east–west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east–west.

Ouachita Mountains

The Ouachita Mountains, simply referred to as the Ouachitas, are a mountain range in western Arkansas and southeastern Oklahoma. They are formed by a thick succession of highly deformed Paleozoic strata constituting the Ouachita Fold and Thrust Belt, one of the important orogenic belts of North America. The Ouachitas continue in the subsurface to the southeast where they make a poorly understood connection with the Appalachians and to the southwest where they join with the Marathon area of West Texas. Together with the Ozark Plateaus, the Ouachitas form the U.S. Interior Highlands. The highest natural point is Mount Magazine at 2,753 feet.

Related Research Articles

Canadian Shield Geographic and geologic area of Canada

The Canadian Shield, also called the Laurentian Plateau, or Bouclier canadien (French), is a large area of exposed Precambrian igneous and high-grade metamorphic rocks that forms the ancient geological core of the North American continent. Composed of igneous rock resulting from its long volcanic history, the area is covered by a thin layer of soil. With a deep, common, joined bedrock region in eastern and central Canada, it stretches north from the Great Lakes to the Arctic Ocean, covering over half of Canada; it also extends south into the northern reaches of the United States. Human population is sparse, and industrial development is minimal, while mining is prevalent.

Geology of the Appalachians

The geology of the Appalachians dates back to more than 480 million years ago. A look at rocks exposed in today's Appalachian Mountains reveals elongate belts of folded and thrust faulted marine sedimentary rocks, volcanic rocks and slivers of ancient ocean floor – strong evidence that these rocks were deformed during plate collision. The birth of the Appalachian ranges marks the first of several mountain building plate collisions that culminated in the construction of the supercontinent Pangaea with the Appalachians and neighboring Little Atlas near the center. These mountain ranges likely once reached elevations similar to those of the Alps and the Rocky Mountains before they were eroded.

Geology of the United States regional geology

The richly textured landscape of the United States is a product of the dueling forces of plate tectonics, weathering and erosion. Over the 4.5 billion-year history of our Earth, tectonic upheavals and colliding plates have raised great mountain ranges while the forces of erosion and weathering worked to tear them down. Even after many millions of years, records of Earth's great upheavals remain imprinted as textural variations and surface patterns that define distinctive landscapes or provinces.

Mississippi embayment Low-lying basin filled with Cretaceous to recent sediments

The Mississippi Embayment is a physiographic feature in the south-central United States, part of the Mississippi Alluvial Plain. It is essentially a northward continuation of the fluvial sediments of the Mississippi River Delta to its confluence with the Ohio River at Cairo, Illinois. The current sedimentary area was formed in the Cretaceous and early Cenozoic by the filling with sediment of a pre-existing basin. An explanation for the embayment's formation was put forward by Van Arsdale and Cox in 2007; movement of the earth's crust brought this region over a volcanic "hotspot" in the Earth's mantle causing an upthrust of magma which formed the Appalachian-Ouachita range. Subsequent erosion caused a deep trough that was flooded by the Gulf of Mexico and eventually filled with sediment from the Mississippi River.

Alleghanian orogeny

The Alleghanian orogeny or Appalachian orogeny is one of the geological mountain-forming events that formed the Appalachian Mountains and Allegheny Mountains. The term and spelling Alleghany orogeny was originally proposed by H.P. Woodward in 1957.

Geology of Texas

Texas contains a great variety of geologic settings. The state's stratigraphy has been largely influenced by marine transgressive-regressive cycles during the Phanerozoic, with a lesser but still significant contribution from late Cenozoic tectonic activity, as well as the remnants of a Paleozoic mountain range.

The East European Craton (EEC) is the core of the Baltica proto-plate and consists of three crustal regions/segments: Fennoscandia to the northwest, Volgo-Uralia to the east, and Sarmatia to the south. Fennoscandia includes the Baltic Shield and has a diversified accretionary Archaean and early Proterozoic crust, while Sarmatia has an older Archaean crust. The Volgo-Uralia region has a thick sedimentary cover, however deep drillings have revealed mostly Archaean crust. There are two shields in the East European Craton: the Baltic/Fennoscandian shield and the Ukrainian shield. The Ukrainian Shield and the Voronezh Massif consists of 3.2-3.8 Ga Archaean crust in the southwest and east, and 2.3-2.1 Ga Early Proterozoic orogenic belts.

Geology of the Rocky Mountains

The geology of the Rocky Mountains is that of a discontinuous series of mountain ranges with distinct geological origins. Collectively these make up the Rocky Mountains, a mountain system that stretches from Northern British Columbia through central New Mexico and which is part of the great mountain system known as the North American Cordillera.

Geology of Pennsylvania

The Geology of Pennsylvania consists of six distinct physiographic provinces, three of which are subdivided into different sections. Each province has its own economic advantages and geologic hazards and plays an important role in shaping everyday life in the state. They are: the Atlantic Coastal Plain Province, the Piedmont Province, the New England Province, the Ridge and Valley Province, the Appalachian Plateau Province, and the Central Lowlands Province.

Geology of Colombia

Geology of Colombia refers to the geological composition of the Republic of Colombia that determines its geography. Most of the emerged territory of Colombia covers vast areas within the South American plate, whereas much submerged territory lies within the Caribbean plate and the Nazca plate.

Geology of West Virginia

West Virginia's geologic history stretches back into the Precambrian, and includes several periods of mountain building and erosion. At times, much of what is now West Virginia was covered by swamps, marshlands, and shallow seas, accounting for the wide variety of sedimentary rocks found in the state, as well as its wealth of coal and natural gas deposits. West Virginia has had no active volcanism for hundreds of millions of years, and does not experience large earthquakes, although smaller tremors are associated with the Rome Trough, which passes through the western part of the state.

This is a list of articles related to plate tectonics and tectonic plates.

Geology of Russia regional geology of Russia

The geology of Russia, the world's largest country, which extends over much of northern Eurasia, consists of several stable cratons and sedimentary platforms bounded by orogenic (mountain) belts.

Geology of North America regional geology of North America

The geology of North America is a subject of regional geology and covers the North American continent, third-largest in the world. Geologic units and processes are investigated on a large scale to reach a synthesized picture of the geological development of the continent.

Geology of Germany

The geology of Germany is heavily influenced by several phases of orogeny in the Paleozoic and the Cenozoic, by sedimentation in shelf seas and epicontinental seas and on plains in the Permian and Mesozoic as well as by the Quaternary glaciations.

The geology of Wyoming includes some of the oldest Archean rocks in North America, overlain by thick marine and terrestrial sediments formed during the Paleozoic, Mesozoic and Cenozoic, including oil, gas and coal deposits. Throughout its geologic history, Wyoming has been uplifted several times during the formation of the Rocky Mountains, which produced complicated faulting that traps hydrocarbons.

The geology of Colorado was assembled from island arcs accreted onto the edge of the ancient Wyoming Craton. The Sonoma orogeny uplifted the ancestral Rocky Mountains in parallel with the diversification of multicellular life. Shallow seas covered the regions, followed by the uplift current Rocky Mountains and intense volcanic activity. Colorado has thick sedimentary sequences with oil, gas and coal deposits, as well as base metals and other minerals.

The geology of Montana includes thick sequences of Paleozoic, Mesozoic and Cenozoic sedimentary rocks overlying ancient Archean and Proterozoic crystalline basement rock. Eastern Montana has considerable oil and gas resources, while the uplifted Rocky Mountains in the west, which resulted from the Laramide orogeny and other tectonic events have locations with metal ore.


  1. 1 2 Donald F. Acton; J.M. Ryder; Hugh French (14 March 2015). "Physiographic Regions". Canadian Encyclopedia . Retrieved 2 June 2019. Interior Plains
  2. 1 2 3 USGS description of the U.S. Interior Plains region