Rise (Mid-Ocean)

A rise is the broad, gently sloped axial uplift of a fast-spreading mid-ocean ridge, the morphology that distinguishes a rise from a slow ridge. Where the full spreading rate exceeds about 8 to 9 cm/yr, the crest is hot, buoyant, and wide, so it lacks the deep axial rift valley of slow boundaries and instead forms a smooth swell only a few hundred meters high at the axis. The East Pacific Rise is the type example. The term contrasts with ridge: usage reserves rise for fast, smooth-crested boundaries and ridge for slow, rift-valley boundaries, though both produce oceanic crust at a spreading center.