Mid-ocean ridge

Mid-ocean ridge

Overview
A mid-ocean ridge is a general term for an underwater
Underwater
Underwater is a term describing the realm below the surface of water where the water exists in a natural feature such as an ocean, sea, lake, pond, or river. Three quarters of the planet Earth is covered by water...

 mountain system
Mountain range
A mountain range is a single, large mass consisting of a succession of mountains or narrowly spaced mountain ridges, with or without peaks, closely related in position, direction, formation, and age; a component part of a mountain system or of a mountain chain...

 that consists of various mountain ranges (chains), typically having a valley
Valley
In geology, a valley or dale 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...

 known as a rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....

 running along its spine, formed by plate tectonics
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

. This type of oceanic ridge is characteristic of what is known as an oceanic spreading center, which is responsible for seafloor spreading
Seafloor spreading
Seafloor spreading is a process that 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....

. The uplifted seafloor results from convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....

 currents which rise in the mantle as magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 at a linear weakness in the oceanic crust
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...

, and emerge as lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

, creating new crust upon cooling.
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Unanswered Questions
Encyclopedia
A mid-ocean ridge is a general term for an underwater
Underwater
Underwater is a term describing the realm below the surface of water where the water exists in a natural feature such as an ocean, sea, lake, pond, or river. Three quarters of the planet Earth is covered by water...

 mountain system
Mountain range
A mountain range is a single, large mass consisting of a succession of mountains or narrowly spaced mountain ridges, with or without peaks, closely related in position, direction, formation, and age; a component part of a mountain system or of a mountain chain...

 that consists of various mountain ranges (chains), typically having a valley
Valley
In geology, a valley or dale 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...

 known as a rift
Rift
In geology, a rift or chasm is a place where the Earth's crust and lithosphere are being pulled apart and is an example of extensional tectonics....

 running along its spine, formed by plate tectonics
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

. This type of oceanic ridge is characteristic of what is known as an oceanic spreading center, which is responsible for seafloor spreading
Seafloor spreading
Seafloor spreading is a process that 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....

. The uplifted seafloor results from convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....

 currents which rise in the mantle as magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 at a linear weakness in the oceanic crust
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...

, and emerge as lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

, creating new crust upon cooling. A mid-ocean ridge demarcates the boundary between two tectonic plates, and consequently is termed a divergent plate boundary.

The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean
Ocean
An ocean is a major body of saline water, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a continuous body of water that is customarily divided into several principal oceans and smaller seas.More than half of this area is over 3,000...

, making the mid-oceanic ridge system the longest mountain range
Mountain range
A mountain range is a single, large mass consisting of a succession of mountains or narrowly spaced mountain ridges, with or without peaks, closely related in position, direction, formation, and age; a component part of a mountain system or of a mountain chain...

 in the world
World
World is a common name for the whole of human civilization, specifically human experience, history, or the human condition in general, worldwide, i.e. anywhere on Earth....

. The continuous mountain range is 65000 km (40,389.2 mi) long (several times longer than the Andes
Andes
The Andes is the world's longest continental mountain range. It is a continual range of highlands along the western coast of South America. This range is about long, about to wide , and of an average height of about .Along its length, the Andes is split into several ranges, which are separated...

, the longest continental mountain range), and the total length of the oceanic ridge system is 80000 km (49,709.8 mi) long.

Description



Mid-ocean ridges are geologically active, with new magma constantly emerging onto the ocean floor and into the crust at and near rifts along the ridge axes. The crystallized magma forms new crust of basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

 (known as MORB for Mid-Ocean Ridge Basalt) and gabbro
Gabbro
Gabbro refers to a large group of dark, coarse-grained, intrusive mafic igneous rocks chemically equivalent to basalt. The rocks are plutonic, formed when molten magma is trapped beneath the Earth's surface and cools into a crystalline mass....

.

The rocks making up the crust below the sea floor are youngest at the axis of the ridge and age with increasing distance from that axis. New magma of basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...

 composition emerges at and near the axis because of decompression melting in the underlying Earth's mantle.

The oceanic crust
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...

 is made up of rocks much younger than the Earth itself: most oceanic crust in the ocean basins is less than 200 million years old. The crust is in a constant state of "renewal" at the ocean ridges. Moving away from the mid-ocean ridge, ocean depth progressively increases; the greatest depths are in ocean trenches. As the oceanic crust
Oceanic crust
Oceanic crust is the part of Earth's lithosphere that surfaces in the ocean basins. Oceanic crust is primarily composed of mafic rocks, or sima, which is rich in iron and magnesium...

 moves away from the ridge axis, the peridotite
Peridotite
A peridotite is a dense, coarse-grained igneous rock, consisting mostly of the minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium, reflecting the high proportions of magnesium-rich olivine, with appreciable iron...

 in the underlying mantle cools and becomes more rigid. The crust and the relatively rigid peridotite below it make up the oceanic lithosphere
Lithosphere
The lithosphere is the rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.- Earth's lithosphere :...

.

Slow spreading ridges like the Mid-Atlantic Ridge
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...

 generally have large, wide rift valleys, sometimes as big as 10–20 km (6.2–12.4 mi) wide and very rugged terrain at the ridge crest that can have relief of up to a 1000 m (3,280.8 ft). By contrast, fast spreading ridges like the East Pacific Rise
East Pacific Rise
The East Pacific Rise is a mid-oceanic ridge, a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate...

 are narrow, sharp incisions surrounded by generally flat topography that slopes away from the ridge over many hundreds of miles.

Formation processes



There are two processes, ridge-push
Ridge-push
Ridge push or sliding plate force is a proposed mechanism for plate motion in plate tectonics. Because mid-ocean ridges lie at a higher elevation than the rest of the ocean floor, gravity causes the ridge to push on the lithosphere that lies farther from the ridge.As molten magma rises at a...

 and slab pull
Slab pull
The Slab pull force is a tectonic plate force due to subduction. Plate motion is partly driven by the weight of cold, dense plates sinking into the mantle at trenches. This force and the slab suction force account for most of the overall force acting on plate tectonics, and the ridge push force...

, thought to be responsible for the spreading seen at mid-ocean ridges, and there is some uncertainty as to which is dominant. Ridge-push occurs when the growing bulk of the ridge pushes the rest of the tectonic plate away from the ridge, often towards a subduction zone. At the subduction zone, "slab-pull" comes into effect. This is simply the weight of the tectonic plate being subducted (pulled) below the overlying plate dragging the rest of the plate along behind it.

The other process proposed to contribute to the formation of new oceanic crust at mid-ocean ridges is the "mantle conveyor" (see image). However, there have been some studies which have shown that the upper mantle
Mantle (geology)
The mantle is a part of a terrestrial planet or other rocky body large enough to have differentiation by density. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer between the crust and the outer core....

 (asthenosphere
Asthenosphere
The asthenosphere is the highly viscous, mechanically weak and ductilely-deforming region of the upper mantle of the Earth...

) is too plastic (flexible) to generate enough friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 to pull the tectonic plate along. Moreover, unlike in the image above, mantle upwelling that causes magma to form beneath the ocean ridges appears to involve only its upper 400 km (248.5 mi), as deduced from seismic tomography
Seismic tomography
Seismic tomography is a methodology for estimating the Earth's properties. In the seismology community, seismic tomography is just a part of seismic imaging, and usually has a more specific purpose to estimate properties such as propagating velocities of compressional waves and shear waves . It...

 and from studies of the seismic discontinuity at about 400 km (248.5 mi). The relatively shallow depths from which the upwelling mantle rises below ridges are more consistent with the "slab-pull" process. On the other hand, some of the world's largest tectonic plates such as the North American Plate
North American Plate
The North American Plate is a tectonic plate covering most of North America, Greenland, Cuba, Bahamas, and parts of Siberia, Japan and Iceland. It extends eastward to the Mid-Atlantic Ridge and westward to the Chersky Range in eastern Siberia. The plate includes both continental and oceanic crust...

 are in motion, yet are nowhere being subducted.

The rate at which the mid-ocean ridge creates new material is known as the spreading rate, and is generally measured in mm/yr. The common subdivisions of spreading rate are fast, medium, and slow with values generally being >100 mm/yr, 100–55 mm/yr, and 55–20 mm/yr, respectively. The spreading rate of the north Atlantic Ocean is ~ 25 mm/yr, while in the Pacific region, it is 80–120 mm/yr. Ridges that spread at rates <20 mm/yr are referred to as ultraslow spreading ridges (e.g., the Gakkel ridge in the Arctic Ocean and the Southwest Indian Ridge) and they provide a much different perspective on crustal formation than their faster spreading brethren.

The mid-ocean ridge systems form new oceanic crust. As crystallized basalt extruded at a ridge axis cools below Curie point
Curie point
In physics and materials science, the Curie temperature , or Curie point, is the temperature at which a ferromagnetic or a ferrimagnetic material becomes paramagnetic on heating; the effect is reversible. A magnet will lose its magnetism if heated above the Curie temperature...

s of appropriate iron-titanium oxides, magnetic field directions parallel to the Earth's magnetic field are recorded in those oxides. The orientations of the field in the oceanic crust record preserve a record of directions of the Earth's magnetic field
Earth's magnetic field
Earth's magnetic field is the magnetic field that extends from the Earth's inner core to where it meets the solar wind, a stream of energetic particles emanating from the Sun...

 with time. Because the field has reversed directions at irregular intervals throughout its history, the pattern of reversals in the ocean crust can be used as an indicator of age. Likewise, the pattern of reversals together with age measurements of the crust is used to help establish the history of the Earth's magnetic field.

History



Discovery


Mid-ocean ridges are generally submerged deep in the ocean. It was not until the 1950s, when the ocean floor was surveyed in detail, that their full extent became known.

The Vema, a ship of the Lamont-Doherty Earth Observatory
Lamont-Doherty Earth Observatory
The Lamont–Doherty Earth Observatory is a research unit of Columbia University located on a campus in Palisades, N.Y., north of Manhattan on the Hudson River.- History :...

 of Columbia University
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...

, traversed the Atlantic Ocean
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

, recording data about the ocean floor from the ocean surface. A team led by Marie Tharp
Marie Tharp
Marie Tharp was a geologist and oceanographic cartographer who, along with her colleague Bruce Heezen, mapped the ocean floor including the Mid-Oceanic Ridges, a line of undersea mountains.-Biography:...

 and ruce C. Heezen|Bruce Heezen]'.',L'MKLBJOVUYFV
L\LPKLJKJKJFGFUHHHBBJKKK was an enormous mountain chain running along the middle of floor of the Atlantic. Scientists gave the name "Mid-Atlantic Ridge
Mid-Atlantic Ridge
The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...

" to the submarine mountain range.

At first, the ridge was thought to be a phenomenon specific to the Atlantic Ocean. However, as surveys of the ocean floor continued around the world, it was discovered that every ocean contains parts of the mid-ocean ridge system. Although the ridge system runs down the middle of the Atlantic Ocean, the ridge is located away from the center of other oceans.

Impact


Alfred Wegener
Alfred Wegener
Alfred Lothar Wegener was a German scientist, geophysicist, and meteorologist.He is most notable for his theory of continental drift , proposed in 1912, which hypothesized that the continents were slowly drifting around the Earth...

 proposed the theory of continental drift
Continental drift
Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...

 in 1912. He stated: the Mid-Atlantic Ridge ... zone in which the floor of the Atlantic, as it keeps spreading, is continuously tearing open and making space for fresh, relatively fluid and hot sima [rising] from depth. However, Wegener did not pursue this observation in his later works and his theory was dismissed by geologists because there was no mechanism to explain how continent
Continent
A continent is one of several very large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents—they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia.Plate tectonics is...

s could plow through ocean crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...

, and the theory became largely forgotten.

Following the discovery of the world-wide extent of the mid-ocean ridge in the 1950s, geologists faced a new task: explaining how such an enormous geological structure could have formed. In the 1960s, geologists discovered and began to propose mechanisms for sea floor spreading. Plate tectonics
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

 was a suitable explanation for sea floor spreading, and the acceptance of plate tectonics by the majority of geologists resulted in a major paradigm shift
Paradigm shift
A Paradigm shift is, according to Thomas Kuhn in his influential book The Structure of Scientific Revolutions , a change in the basic assumptions, or paradigms, within the ruling theory of science...

 in geological thinking.

It is estimated that 20 volcanic eruptions occur each year along earth's mid-ocean ridges and that every year 2.5 square kilometre of new sea floor is formed by this process. With a crustal thickness of 1 to 2 km (0.621372736649807 to 1.2 mi), this amounts to about 4 km³ (0.959651034417147 cu mi) of new ocean crust formed every year.

List of oceanic ridges

  • Aden Ridge
    Aden Ridge
    The Aden Ridge is a divergent tectonic plate boundary which runs offshore in the Gulf of Aden and Indian Ocean along the southeastern coastline of the Arabian Peninsula. It extends eastward from the Afar Triple Junction to a junction with the Owen Fracture Zone, and separates the Arabian Plate...

  • Explorer Ridge
    Explorer Ridge
    The Explorer Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located about west of Vancouver Island, British Columbia, Canada. It lies at the northern extremity of the Pacific spreading axis...

  • Gorda Ridge
    Gorda Ridge
    The Gorda Ridge is a tectonic spreading center located off the coast of Oregon and northern California north of Cape Mendocino. It runs from a triple junction with the San Andreas Fault and the Mendocino Fracture Zone northward to another transform boundary, the Blanco Fracture Zone...

  • Juan de Fuca Ridge
    Juan de Fuca Ridge
    The Juan de Fuca Ridge is a tectonic spreading center located off the coasts of the state of Washington in the United States and the province of British Columbia in Canada. It runs northward from a transform boundary, the Blanco Fracture Zone, to a triple junction with the Nootka Fault and the...

  • Cocos Ridge

  • American-Antarctic Ridge
    American-Antarctic Ridge
    The American-Antarctic Ridge is a tectonic spreading center between the South American Plate and the Antarctic Plate. It runs along the seafloor from the Bouvet Triple Junction in the South Atlantic Ocean southwestward to a major transform fault boundary east of the South Sandwich...

  • Chile Rise
    Chile Rise
    The Chile Rise or Chile Ridge is an oceanic ridge, a tectonic divergent plate boundary between the Nazca and Antarctic Plates. Its eastern end is the Chile Triple Junction where the Chile Rise is being subducted below the South American Plate in the Peru-Chile Trench...

  • East Pacific Rise
    East Pacific Rise
    The East Pacific Rise is a mid-oceanic ridge, a divergent tectonic plate boundary located along the floor of the Pacific Ocean. It separates the Pacific Plate to the west from the North American Plate, the Rivera Plate, the Cocos Plate, the Nazca Plate, and the Antarctic Plate...

  • East Scotia Ridge
  • Gakkel Ridge
    Gakkel Ridge
    The Gakkel Ridge is a mid-oceanic ridge, a divergent tectonic plate boundary between the North American Plate and the Eurasian Plate. It is located in the Arctic Ocean between Greenland and Siberia, and has a length of about 1,800 kilometers...

     (Mid-Arctic Ridge)
  • Pacific-Antarctic Ridge
    Pacific-Antarctic Ridge
    The Pacific–Antarctic Ridge is a divergent tectonic plate boundary located on the seafloor of the South Pacific Ocean, separating the Pacific Plate from the Antarctic Plate...


  • Southeast Indian Ridge
    Southeast Indian Ridge
    The Southeast Indian Ridge is a divergent tectonic plate boundary located along the seafloor of the southern Indian Ocean. It separates the Indo-Australian Plate to the north from the Antarctic Plate to the south...

  • Central Indian Ridge
    Central Indian Ridge
    The Central Indian Ridge is a divergent tectonic plate boundary between the African Plate and the Indo-Australian Plate, traversing the western regions of the Indian Ocean...

    • Carlsberg Ridge
      Carlsberg Ridge
      The Carlsberg Ridge is the northern section of the Central Indian Ridge, a divergent tectonic plate boundary between the African Plate and the Indo-Australian Plate, traversing the western regions of the Indian Ocean....

  • Southwest Indian Ridge
    Southwest Indian Ridge
    The Southwest Indian Ridge is a divergent tectonic plate boundary located along the floor of the southwest Indian Ocean. It separates the African Plate to the north from the Antarctic Plate to the south....


  • Mid-Atlantic Ridge
    Mid-Atlantic Ridge
    The Mid-Atlantic Ridge is a mid-ocean ridge, a divergent tectonic plate boundary located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. It separates the Eurasian Plate and North American Plate in the North Atlantic, and the African Plate from the South...

    • Knipovich Ridge (between Greenland and Spitsbergen)
    • Mohns Ridge
    • Kolbeinsey Ridge (North of Iceland)
    • Reykjanes Ridge (South of Iceland)

List of ancient oceanic ridges

  • Aegir Ridge
    Aegir Ridge
    The Aegir Ridge is an extinct mid-ocean ridge in the far-northern Atlantic Ocean. It marks the initial line of break-up of the northern Atlantic, along which seafloor spreading was initiated at the beginning of the Eocene epoch...

  • Alpha Ridge
    Alpha Ridge
    The Alpha Ridge is a major volcanic ridge under the Arctic Ocean between the Canada Basin and the Lomonosov Ridge. It was active during the formation of the Amerasian Basin. It was discovered in 1963. The highest elevation is about 2.7 km over the ocean floor. It is 200 to 450 km wide...

  • Bellingshausen Ridge
    Bellingshausen Plate
    The Bellingshausen Plate was an ancient tectonic plate that fused onto the Antarctic Plate. It is named after the Baltic German-Russian explorer of Antarctica, Fabian Gottlieb von Bellingshausen....

  • Izanagi Ridge
    Izanagi Plate
    The Izanagi Plate was an ancient tectonic plate, which began subducting beneath the Okhotsk section of the North American Plate during 130 - 100 Ma. The rapid plate motion of the Izanagi Plate caused the northward drift of north-west Japan and the outer zone of south-west Japan...

  • Kula-Farallon Ridge
  • Pacific-Kula Ridge
    Pacific-Kula Ridge
    The Pacific–Kula Ridge is a former mid-ocean ridge that existed between the Pacific and Kula plates in the Pacific Ocean during the early Tertiary period. Its appearance was in an east-west direction and the Hawaiian-Emperor seamount chain had its attribution with the ridge...

  • Pacific-Farallon Ridge
    Pacific-Farallon Ridge
    The Pacific–Farallon Ridge is a former mid-ocean ridge that existed between the Pacific and Farallon plates in the Pacific Ocean during the Tertiary period. Its appearance was in a north-south direction. About 60 million years ago, it might have extended at least . Remnants of the...

  • Phoenix Ridge
    Phoenix Ridge
    The Phoenix Ridge was an ancient mid-ocean ridge that existed between the Phoenix Plate and the Pacific Plate. The Phoenix Ridge consisted of three ridges and had a spreading rate of 18–20 cm per year until around 84 Ma. A major decrease in spreading rate, and the convergence rate with the...


See also

  • Divergent boundary
    Divergent boundary
    In plate tectonics, a divergent boundary or divergent plate boundary is a linear feature that exists between two tectonic plates that are moving away from each other. Divergent boundaries within continents initially produce rifts which produce rift valleys...

  • List of Oceanic Landforms
  • Petrological Database of the Ocean Floor
    Petrological Database of the Ocean Floor
    The Petrological Database of the Ocean Floor is a relational database and repository for global geochemical data on igneous and metamorphic rocks generated at mid-ocean ridges including back-arc basins, young seamounts, and old oceanic crust...

  • Plate tectonics
    Plate tectonics
    Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

  • Ridge-push
    Ridge-push
    Ridge push or sliding plate force is a proposed mechanism for plate motion in plate tectonics. Because mid-ocean ridges lie at a higher elevation than the rest of the ocean floor, gravity causes the ridge to push on the lithosphere that lies farther from the ridge.As molten magma rises at a...

  • Seafloor spreading
    Seafloor spreading
    Seafloor spreading is a process that 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....

  • Slab window
    Slab window
    In geology, a slab window is a gap that forms in a subducted oceanic plate when a mid-ocean ridge meets with a subduction zone. They are commonly associated with the formation of convergent plate boundaries and they have had significant effects on the formation of the North American Cordillera.A...

  • Famous locations on the continent
    • Iceland
      Geography of Iceland
      Iceland is a medium-sized island in the North Atlantic ocean. The island is located east of Greenland and immediately south of the Arctic Circle, atop the divergent boundary of the Mid-Atlantic Ridge in the North Atlantic Ocean. It lies about from New York City and from Scotland...

    • Afar Depression
      Afar Depression
      The Afar Triangle is a geological depression that is caused by the Afar Triple Junction which is part of the Great Rift Valley. It overlaps Eritrea, Djibouti and the entire Afar Region of Ethiopia. The Afar Triangle includes the Danakil Depression and the lowest point in Africa, Lake Asal...


External links