Seafloor spreading is a phenomenon that occurs at mid-oceanic ridges, such as the mid-atlantic ridge. new crust, which is created by volcanic activity, spreads away from the ridge. seafloor spreading could be one reason a) the continents are drifting apart. b) all earthquakes have their epicenters in oceans. c) most active volcanoes are found in the atlantic ocean. d) the mid-atlantic ridge is the longest mountain range in the world.