rift valley

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A rift valley near Quilotoa, Ecuador.
A rift valley in geology is a valley created by the formation of a rift. The Great Rift Valley, located in the Middle East and Africa, is the most famous of the world's rift valleys. Rift valleys are produced by tensional tectonic forces which occur at divergent plate boundaries. Rift valleys typically appear as a downdropped graben between a pair of faults, or vertical Earth movements. Rift valleys are often deep and flanked by volcanoes. The margins of rifts are commonly uplifted, so that the downfaulting of the rift floor is associated with the uplift of both margins. Which of these two processes initiates the composite rifting penomenon is still debated, but their co-occurrence is common. Where the extension that generates rifting is not normal to the rift axis but is somewhat oblique, a series of basins may develop along the axial zone, then, as extension continues, the basins merge to form the rift. Such basins are commonplace in the central and northern Red Sea, as well as other rifts.

The most extensive rift valley is located along the crest of the mid-ocean ridge system and is the result of seafloor spreading. Existing continental rift valleys are usually the result of a failed arm (aulacogen) of a triple junction. Examples besides the Great Rift Valley include the Mississippi embayment and the Rio Grande Rift in North America.

The largest freshwater lakes in the world are all located in rift valleys.[1] Lake Baikal in Siberia, a World Heritage Site,[2], lies in an active rift valley. Baikal is both the deepest lake in the world and, with 20% of all of the liquid freshwater on earth, has the greatest volume.[3] Lake Tanganyika, second by both measures, is in the Albertine Rift, the westernmost arm of the active Great Rift Valley of East Africa and Southwest Asia. Lake Superior in North America, the largest freshwater lake by area, lies in the ancient and dormant Midcontinent Rift.

Notes

1. ^ The World's Greatest Lakes. Retrieved on 2007-01-07.
2. ^ Lake Baikal - World Heritage Site. World Heritage. Retrieved on 2007-01-13.
3. ^ The Oddities of Lake Baikal. Alaska Science Forum. Retrieved on 2007-01-07.
  • Bonatti, E., 1985. Punctiform initiation of seafloor spreading in the Red Sea during transition from a continental to an oceanic rift. Nature, 316: 33-37.
  • Mart, Y., Dauteuil, O., 2000. Analogue experiments of propagation of oblique rifts. Tectonophysics, 316: 121-132.
Oceanic crust      0-20 Ma
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geology, a valley is a depression with predominant extent in one direction. A very deep river valley may be called a canyon or gorge.

The terms U-shaped and V-shaped are descriptive terms of geography to characterize the form of valleys.
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rift is a place where the Earth's crust and lithosphere are being pulled apart. Typical features are a central linear downdropped fault segment, called a graben, with parallel normal faulting and rift-flank uplifts on either side forming a rift valley.
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Great Rift Valley is a vast geographical and geological feature, approximately 6,000 kilometres (0 mi) in length, which runs from northern Syria in Southwest Asia to central Mozambique in East Africa.
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Middle East is a historical and political region of Africa-Eurasia with no clear boundaries. The term "Middle East" was popularized around 1900 in Britain, and has been criticized for its loose definition.
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Africa is the world's second-largest and second most-populous continent, after Asia. At about 30,221,532 km² (11,668,545 sq mi) including adjacent islands, it covers 6% of the Earth's total surface area, and 20.4% of the total land area.
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Plate tectonics (from Greek τέκτων, tektōn "builder" or "mason") is a theory of geology that has been developed to explain the observed evidence for large scale motions of the Earth's lithosphere.
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graben is a depressed block of land bordered by parallel faults. Graben is German for ditch.

A graben is the result of a block of land being downthrown producing a valley with a distinct scarp on each side. Grabens often occur side-by-side with horsts.
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fault or fault line is a planar rock fracture, which shows evidence of relative movement. Large faults within the Earth's crust are the result of shear motion and active fault zones are the causal locations of most earthquakes.
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Volcano:
1. Large magma chamber
2. Bedrock
3. Conduit (pipe)
4. Base
5. Sill
6. Branch pipe
7. Layers of ash emitted by the volcano
8. Flank 9. Layers of lava emitted by the volcano
10. Throat
11. Parasitic cone
12. Lava flow
13. Vent
14.
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mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent
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Seafloor spreading occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics.

Earlier theories (e.g.
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In geology, an aulacogen is a failed arm of a triple junction of a plate tectonics rift system. A triple junction beneath a continental plate initiates a three way breakup of the continental plate.
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A triple junction is the point where the boundaries between three tectonic plates, and three plate margins, meet. At the triple junction a boundary will be one of 3 types - a ridge, trench or transform fault and triple junctions can be described according to the types of plate
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Great Rift Valley is a vast geographical and geological feature, approximately 6,000 kilometres (0 mi) in length, which runs from northern Syria in Southwest Asia to central Mozambique in East Africa.
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Mississippi embayment is a physiographic feature in the south-central United States. 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.
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The Rio Grande Rift is a rift valley extending north from Mexico, near El Paso, Texas through New Mexico into central Colorado.[1] The upper Rio Grande flows south down the rift valley, but did not incise the rift valley.
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North America is a continent [1] in the Earth's northern hemisphere and (chiefly) western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the south and west
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Coordinates Coordinates:
Lake type Continental rift lake
Primary sources
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Siberia (Russian: Сиби́рь, Sibir); is a vast region on the eastern and North-Eastern part of the Russian Federation constituting almost all of Northern Asia and comprising a large part of the
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A UNESCO World Heritage Site is a specific site (such as a forest, mountain, lake, desert, monument, building, complex, or city) that has been nominated and confirmed for inclusion on the list maintained by the international World Heritage Programme administered by the UNESCO
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Coordinates Coordinates:
Lake type Rift Valley Lake
Primary sources Ruzizi River
Malagarasi River
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Great Rift Valley is a vast geographical and geological feature, approximately 6,000 kilometres (0 mi) in length, which runs from northern Syria in Southwest Asia to central Mozambique in East Africa.
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East Africa or Eastern Africa is the easternmost region of the African continent, variably defined by geography or geopolitics. In the UN scheme of geographic regions, 19 territories constitute Eastern Africa:

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Southwest Asia or Southwestern Asia (largely overlapping with the Middle East) is the southwestern portion of Asia. The term Western Asia is sometimes used in writings about the archeology and the late prehistory of the region, and in the United States subregion
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Coordinates Coordinates:
Lake type Rift lake
Primary sources Nipigon River,
St.
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North America is a continent [1] in the Earth's northern hemisphere and (chiefly) western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the south and west
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Fresh Water is the debut album by Australian rock and blues singer Alison McCallum, released in 1972. Rare for an Australian artist at the time, it came in a gatefold sleeve.
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lake (from Latin ligacus) is a body of water or other liquid of considerable size contained on a body of land. A vast majority of lakes on Earth are fresh water, and most lie in the Northern Hemisphere at higher latitudes.
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Midcontinent Rift System (MRS) or Keweenawan Rift is a 2,000 km. long geological rift in the center of the North American continent and south-central part of the North American plate.
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