One driving force for plate movements, plate boundaries, and sea-floor spreading is convection currents within the Earth's mantle. These currents are caused by the heat generated by the radioactive decay of elements in the Earth's core. As the mantle heats up, it becomes less dense and rises towards the surface, creating convection currents that push the tectonic plates on the surface of the Earth. This movement of the plates leads to the formation of plate boundaries and the process of sea-floor spreading.
