The mechanism by which new seafloor is created along the rift at the crest of a mid-ocean ridge as adjacent plates move apart. The crust separates along the rift, and new seafloor forms as hot new crust upwells into these cracks. The new seafloor spreads laterally away from the rift and is replaced by even newer crust in a continuing process of plate creation (Grotzinger et al., 2007).