Mid-Ocean Ridge

A mid-ocean ridge is the globe-encircling volcanic mountain chain where two plates diverge and new oceanic crust forms by decompression melting of upwelling mantle. The crust cools, contracts, and subsides with age, so depth increases predictably with distance from the axis (the age-depth relation). Spreading rates run from a few centimeters a year at slow ridges like the Mid-Atlantic to over 15 cm at the fast East Pacific Rise, which shapes ridge morphology.