Mid-ocean ridge

A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about 2,600 meters (8,500 ft) and rises about 2,000 meters (6,600 ft) above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin.

For broader coverage of this topic, see Undersea mountain range.

The production of new seafloor and oceanic lithosphere results from mantle upwelling in response to plate separation. The melt rises as magma at the linear weakness between the separating plates, and emerges as lava, creating new oceanic crust and lithosphere upon cooling.

The first discovered mid-ocean ridge was the Mid-Atlantic Ridge, which is a spreading center that bisects the North and South Atlantic basins; hence the origin of the name 'mid-ocean ridge'. Most oceanic spreading centers are not in the middle of their hosting ocean basis but regardless, are traditionally called mid-ocean ridges. Mid-ocean ridges around the globe are linked by plate tectonic boundaries and the trace of the ridges across the ocean floor appears similar to the seam of a baseball. The mid-ocean ridge system thus is the longest mountain range on Earth, reaching about 65,000 km (40,000 mi).

Impact on global sea level[edit]

Increased rates of seafloor spreading (i.e. the rate of expansion of the mid-ocean ridge) have caused the global (eustatic) sea level to rise over very long timescales (millions of years).^[32]^[33] Increased seafloor spreading means that the mid-ocean ridge will then expand and form a broader ridge with decreased average depth, taking up more space in the ocean basin. This displaces the overlying ocean and causes sea levels to rise.^[34]

Sealevel change can be attributed to other factors (thermal expansion, ice melting, and mantle convection creating dynamic topography^[35]). Over very long timescales, however, it is the result of changes in the volume of the ocean basins which are, in turn, affected by rates of seafloor spreading along the mid-ocean ridges.^[36]

The 100 to 170 meters higher sea level of the Cretaceous Period (144–65 Ma) is partly attributed to plate tectonics because thermal expansion and the absence of ice sheets only account for some of the extra sea level.^[34]

Oceanic ridge and deep sea vent chemistry

Plates in the crust of the earth, according to the plate tectonics theory

Seafloor magnetic striping

A demonstration of magnetic striping

– Rift portion in Gulf of Aden

Aden Ridge

– Pacific volcanic hotspot

Cocos Ridge

– Mid-ocean ridge west of British Columbia, Canada

Explorer Ridge

- an east-west trending mid-ocean ridge east of the eponymous islands between the Nazca and Cocos plates

Galapagos Spreading Center

– Tectonic spreading center off the northern coast of California and southern Oregon

Gorda Ridge

– Divergent plate boundary off the coast of the Pacific Northwest region of North America

Juan de Fuca Ridge

– Mid-ocean ridge in the South Atlantic between the South American Plate and the Antarctic Plate

South American–Antarctic Ridge

– Submarine oceanic ridge in the Pacific Ocean

Chile Rise

– Mid-oceanic ridge at a divergent tectonic plate boundary on the floor of the Pacific Ocean

East Pacific Rise

– Mid-oceanic ridge under the Arctic Ocean between the North American and Eurasian plates(Mid-Arctic Ridge)

Gakkel Ridge

– Tectonic plate boundary in the South Pacific Ocean

Pacific-Antarctic Ridge

Central Indian Ridge

Carlsberg Ridge

– Mid-ocean ridge in the southern Indian Ocean

Southeast Indian Ridge

– A mid-ocean ridge on the bed of the south-west Indian Ocean and south-east Atlantic Ocean

Southwest Indian Ridge

Mid-Atlantic Ridge

Kolbeinsey Ridge

– Geological depression caused by the Afar Triple Junction

Afar Triangle

Geography of Iceland

– Links to Wikipedia articles on landforms

List of oceanic landforms

Ocean chemistry

Oceanic crust

Petrological Database of the Ocean Floor

– first crewed submersible study of the rift valley of the Mid-Atlantic Ridge

Project FAMOUS

– discovery of black smokers hydrothermal systems on the East Pacific Rise

RISE project

– Type of gap in a subducted oceanic plate

Slab window

– Underwater vents or fissures in the Earth's surface from which magma can erupt

Submarine volcano

hypothesis; explains relation of marine magnetic anomalies to seafloor spreading.