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(October 2007)| A mid-ocean ridge is a general term for an
underwater mountain system that consists of various mountain
ranges (chains), typically having a valley known as a rift
running along its spine, formed by plate tectonics. This type of
oceanic ridge is characteristic of what is known as an oceanic
spreading center, which is responsible for seafloor spreading.
The uplifted seafloor results from convection currents which
rise in the mantle as magma at a linear weakness in the oceanic
crust, and emerge as lava, 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, making the mid-oceanic ridge system the longest mountain
range in the world. The continuous mountain range is 65,000 km
(40,400 mi) long (several times long