<P> Tectonic plates are able to move because the Earth 's lithosphere has greater mechanical strength than the underlying asthenosphere . Lateral density variations in the mantle result in convection ; that is , the slow creeping motion of Earth 's solid mantle . Plate movement is thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography ( the ridge is a topographic high ) and density changes in the crust ( density increases as newly formed crust cools and moves away from the ridge ) . At subduction zones the relatively cold , dense crust is `` pulled '' or sinks down into the mantle over the downward convecting limb of a mantle cell . Another explanation lies in the different forces generated by tidal forces of the Sun and Moon . The relative importance of each of these factors and their relationship to each other is unclear , and still the subject of much debate . </P>
<P> Tectonic plates are able to move because the Earth 's lithosphere has greater mechanical strength than the underlying asthenosphere . Lateral density variations in the mantle result in convection ; that is , the slow creeping motion of Earth 's solid mantle . Plate movement is thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography ( the ridge is a topographic high ) and density changes in the crust ( density increases as newly formed crust cools and moves away from the ridge ) . At subduction zones the relatively cold , dense crust is `` pulled '' or sinks down into the mantle over the downward convecting limb of a mantle cell . Another explanation lies in the different forces generated by tidal forces of the Sun and Moon . The relative importance of each of these factors and their relationship to each other is unclear , and still the subject of much debate . </P>
the motion of earth 's plates is driven by
the motion of earth 's plates is driven by
thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography ( the ridge is a topographic high ) and density changes in the crust ( density increases as newly formed crust cools and moves away from the ridge )
thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography ( the ridge is a topographic high ) and density changes in the crust ( density increases as newly formed crust cools and moves away from the ridge )