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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.
The Earthâs crust and upper part of the mantle is broken into large pieces of rock. These large pieces of rocks are called tectonic plates. Tectonic plates never stop moving, this process is called continental drift. Tectonic plates move because of convection currents. These convection currents happen in the mantle, underneath the tectonic plates. The heat, which causes the convection currents, is produced from the radioactive decay left over from the Earths formation. The reason why convection currents are relevant to the moving of tectonic plates is because the heat builds up pressure underneath the crust (tectonic plates).