sea-floor spreading

Sea-floor spreading along the midoceanic ridge. 

Photo credit: USGS and Natl. Park Service
Used with permission

Sea-floor spreading occurs where oceanic plates are diverging from one another. Magma rises along a rift zone and spreads out at the surface building new sea floor. As a result, the age of the rocks increases as one moves away from the rift zone. The midoceanic ridge is the primary site for sea-floor spreading. Earthquakes and volcanoes are where sea floor spreading is occurring.