<P> The rocks making up the crust below the seafloor are youngest along the axis of the ridge and age with increasing distance from that axis . New magma of basalt composition emerges at and near the axis because of decompression melting in the underlying Earth's mantle . </P> <P> The oceanic crust 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 moves away from the ridge axis, the peridotite in the underlying mantle cools and becomes more rigid . The crust and the relatively rigid peridotite below it make up the oceanic lithosphere . </P> <P> The bathymetry, or profile of a MOR is largely determined by the seafloor spreading rate at the ridge . Slow spreading ridges (<5 cm / yr) like the Mid-Atlantic Ridge (MAR) generally have large, wide rift valleys, sometimes as wide as 10--20 km (6.2--12.4 mi), and very rugged terrain at the ridge crest that can have relief of up to a 1,000 m (3,300 ft). By contrast, fast spreading ridges (> 8 cm / yr) like the East Pacific Rise (EPR) are narrow, sharp incisions surrounded by generally flat topography that slopes away from the ridge over many hundreds of miles . Ultra-slow spreading ridges (<2 cm / yr), like the Southwest India and the Arctic Ridges form both magmatic and amagmatic ridge segments without transform faults . </P> <P> The spreading center or axis, commonly connects to a transform fault oriented at right angles to the axis . The flanks of mid-ocean ridges are in many places marked by the inactive scars of transform faults called fracture zones . At faster spreading rates the axes often display Overlapping Spreading Centers that lack connecting transform faults . </P>

What would you find at mid ocean ridge