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Encyclopedia > Laurentia

The North American craton (also known as Laurentia), like all craton land, was created as continents move about the surface of the Earth, bumping into other continents and drifting away. Image File history File links North_america_craton_nps. ... Image File history File links North_america_craton_nps. ... World map showing North America A satellite composite image of North America. ... World geologic provinces. ... Color-coded regions of the world based on the seven commonly reckoned continents Dymaxion map by Buckminster Fuller shows land masses with minimal distortion as nearly one continuous continent A continent is one of several large landmasses on Earth. ... Earth, also known as the Earth or Terra, is the third planet outward from the Sun. ...


Many times in its past, Laurentia has been a separate continent as it is now in the form of North America. During other times in its past, Laurentia has been part of a supercontinent. It is named after the Laurentian Shield. Color-coded regions of the world based on the seven commonly reckoned continents Dymaxion map by Buckminster Fuller shows land masses with minimal distortion as nearly one continuous continent A continent is one of several large landmasses on Earth. ... In geology, a supercontinent is a land mass comprising more than one continental core, or craton. ... The Canadian Shield is a large geographic area in eastern and central Canada and adjacent portions of the United States, composed of bare rock dating to the Precambrian Era (between 4. ...


This process takes millions of years to happen, but the results can be seen today in the rocks of the continents.


The middle of most continents have not been buckled up into mountains the way the edges have been. That is because the middle of the continents are made of very strong old rock. This part of the continent is called the stable craton.

Contents

Interior Platform

In eastern and central Canada, much of the stable craton is exposed at the surface as the Canadian Shield. In the United States the craton bedrock is covered with sedimentary rocks of the Interior Platform except in northern Minnesota and Wisconsin and the Upper Peninsula of Michigan. The sequence of rocks varies from approximately 3,500 in excess of 20,000 feet in thickness. The cratonic rocks are metamorphic and igneous while the overlying sedimentary rocks are composed mostly of limestones, sandstones, and shales. These sedimentary rocks were deposited from 650 to 290 million years ago. Canadian Shield The Canadian Shield— also called the Precambrian Shield, Laurentian Shield, Bouclier Canadien (French), or Laurentian Plateau— is a large shield covered by a thin layer of soil that forms the nucleus of the North American craton. ... Quartzite, a form of metamorphic rock, from the Museum of Geology at University of Tartu collection. ... Igneous rocks are formed when molten rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... This article or section does not adequately cite its references or sources. ... For other uses, see Limestone (disambiguation). ... Red sandstone interior of Lower Antelope Canyon, Arizona, worn smooth due to erosion by flash flooding over millions of years Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. ... Shale Shale is a fine-grained sedimentary rock whose original constituents were clays or muds. ...


Tectonic Setting

The metamorphic and igneous rocks of the "basement complex" were created 1.5 to 1.0 billion years ago in a tectonically active setting. It was a setting of great pressure and temperature. The younger sedimentary rocks that were deposited on top of this basement complex were formed in a setting of quiet marine and river waters. During much of Mississippian time, the craton was the site of an extensive marine carbonate platform on which mainly limestones and some dolostones and evaporites were deposited. This platform extended either from the present Appalachian Mountains or Mississippi Valley to the present Great Basin. The craton was covered by shallow, warm, tropical epicontinental or epicratonic sea (meaning literally "on the craton") that had maximum depths of only about 60 m (200 ft) at the shelf edge. Sometimes land masses or mountain chains rose up on the distant edges of the craton and then eroded down, shedding their sand across the landscape. In geology, the terms basement and crystalline basement are used to define the rocks below a sedimentary platform or cover, or more generally any rock below sedimentary rocks or sedimentary basins that are metamorphic or igneous in origin. ... Lyskamm, 4 527 m, Pennine Alps A mountain is a landform that extends above the surrounding terrain in a limited area. ...


Geological history of Laurentian craton in chronological order

  • ~2.5 billion years ago, Arctica formed as an independent continent.
  • ~2.45 billion years ago, Arctica was part of the major supercontinent Kenorland.
  • ~2.1 billion years ago, when Kenorland shattered, the Arctican craton was part of the minor supercontinent Nena along with Baltica and Eastern Antarctica.
  • ~1.8 billion years ago, Laurentia was part of the major supercontinent Columbia.
  • ~1.5 billion years ago, Laurentia was an independent continent.
  • ~1.1 billion years ago, Laurentia was part of the major supercontinent Rodinia.
  • ~750 million years ago, Laurentia was part of the minor supercontinent Protolaurasia. Laurentia nearly rifted apart.
  • ~600 million years ago, Laurentia was part of the major supercontinent Pannotia.
  • ~Cambrian, Laurentia was an independent continent.
  • ~Ordovician, Laurentia was shrinking and Baltica got bigger.
  • ~Devonian, Laurentia collided against Baltica, forming the minor supercontinent Euramerica.
  • ~Permian, all major continents collide against each other for forming the major supercontinent Pangaea.
  • ~Jurassic, Pangaea rifted into two minor supercontinents: Laurasia and Gondwana. Laurentia was part of the minor supercontinent Laurasia.
  • ~Cretaceous, Laurentia was an independent continent called North America.
  • ~Neogene, Laurentia, in the form of North America, crashed into South America, forming the minor supercontinent America.
  • ~250 million years from now, all continents may crash together, forming the major supercontinent Pangaea Ultima. Laurentia will be part of Pangaea Ultima.

Arctica was an ancient continent approximately 2. ... Kenorland was one of the earliest supercontinents found on Earth. ... Nena was an ancient minor supercontinent. ... Baltica (green) Baltica is a Late Proterozoic-Early Palaeozoic continent that now includes the East European craton of northwestern Eurasia. ... Depiction of Rodinia at time of initial breakup. ... Laurasia is the overall name for the vast continent that was composed of Laurentia, Siberia, Baltica and parts of Asia. ... Pannotia is the name given to a hypothetical supercontinent that existed from about 600 to about 540 mya. ... The Cambrian is a major division of the geologic timescale that begins about 542 ± 1. ... The Ordovician period is the second of the six (seven in North America) periods of the Paleozoic era. ... Disambiguation: Devonian is sometimes used to refer to the Southwestern Brythonic language, and the people of the county of Devon are sometimes referred to as Devonians The Devonian is a geologic period of the Paleozoic era spanning from roughly 415 to 360 million years ago. ... Euramerica (also known as Laurussia) was a minor supercontinent created in the Devonian by the collision of Laurentia and Baltica (Scandian Orogeny). ... The Permian is a geologic period that extends from about 299. ... Map of Pangaea Pangaea or Pangea (derived from Παγγαία, Greek meaning all earth) is the name given to the supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the process of plate tectonics separated each of the component continents into their current configuration. ... The Jurassic Period is a major unit of the geologic timescale that extends from about 199. ... Laurasia was a supercontinent that most recently existed as a part of the split of the Pangaean supercontinent in the late Mesozoic era. ... Gondwanaland redirects here. ... The Cretaceous Period is one of the major divisions of the geologic timescale, reaching from the end of the Jurassic Period (i. ... Neogene Period is a unit of geologic time consisting of the Miocene, Pliocene, Pleistocene, and Holocene epochs. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... Pangaea Ultima is a possible future supercontinent configuration, which, consistent with the supercontinent cycle, may occur within the next 250 million years. ...

Other use

"Laurentia" was also a proposed name for the country that united as Canada. Detail from the current Canadian $20 bank note, issued in 2004. ...


External links

External image


  Results from FactBites:
 
Laurentia - Wikipedia, the free encyclopedia (371 words)
Laurentia is the craton at the heart of North America.
Many times in its past, Laurentia has been a separate continent as it is now in the form of North America.
"Laurentia" was also a proposed name for the country that united as Canada.
  More results at FactBites »

 
 

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