A
mid-ocean ridge (
MOR) 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 long (several times longer than the
Andes, the longest continental mountain range), and the total length of the oceanic ridge system is 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 (known as MORB for Mid-Ocean Ridge Basalt) and
gabbro.
The rocks making up the crust below the sea floor are youngest at the axis of the ridge and age with...
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