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Mid-ocean ridge cross-section (cut-away view) 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.
At nearly 60,000 km long, the mid-ocean ridge is an extensive chain of underwater volcanic mountains that spans the globe. [30] Centralized in the oceans, this unique geological formation houses a collection of ridges , rifts, fault zones , and other geological features.
Magnetic anomalies off west coast of North America. Dashed lines are spreading centers on mid-ocean ridges. The Vine–Matthews-Morley hypothesis correlates the symmetric magnetic patterns seen on the seafloor with geomagnetic field reversals. At mid-ocean ridges, new crust is created by the injection, extrusion, and solidification of magma.
Spreading rate is the rate at which an ocean basin widens due to seafloor spreading. (The rate at which new oceanic lithosphere is added to each tectonic plate on either side of a mid-ocean ridge is the spreading half-rate and is equal to half of the spreading rate). Spreading rates determine if the ridge is fast, intermediate, or slow.
If originated from current tectonic forces, they are often referred to as a mid-ocean ridge. In contrast, if formed by past above-water volcanism, they are known as a seamount chain. The largest and best known undersea mountain range is a mid-ocean ridge, the Mid-Atlantic Ridge. [1]
Pillow lava from the Gakkel Ridge. The Gakkel Ridge is approximately 1,800 kilometres (1,100 mi) long and is the slowest known spreading ridge on earth, with a rate of less than one centimeter per year. It continues to the south and connects with the Knipovich Ridge. [8] The Gakkel ridge is not offset by any transform faults.
Mid-ocean ridge spreading centres are the sites of almost continuous magmatism. The basalts erupted at mid-ocean ridges are tholeiitic in character and result from the partial melting of upwelling asthenosphere. The composition of Mid-Ocean Ridge Basalts (MORB) shows little variation globally as they come from a mostly homogeneous source. [4]
Axial lies where the chain intersects with the Juan de Fuca Ridge, [7] approximately 480 km (298 mi) west of Oregon. It is a product of the Cobb hotspot, but now sits on an ocean spreading center between the Juan de Fuca plate and the Pacific Plate, [8] offset by the Blanco fracture zone to the south and a ridge-built triple junction to the ...