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1 Seafloor spreading is one of the two major processes of plate tectonics, the other being subduction. 2  Seafloor spreading is the continuous process of forming new igneous rock at midocean ridges by injection of magma that forms new seafloor. Seafloor spreading is one of the two major processes of plate tectonics, the other being subduction. 2  Seafloor spreading is the continuous process of forming new igneous rock at midocean ridges by injection of magma that forms new seafloor.
Oceans filled the areas between these new sub-continents. The land masses continued to move apart, riding on separate plates, until they reached the positions they currently occupy. These continents are still on the move today. Exactly what drives plate tectonics is not known. One theory is that convection within the Earth's mantle pushes the plates, in much the same way that air heated by your body rises upward and is deflected sideways when it reaches the ceiling.