What drives the movement of tectonic plates?

Convection currents

Explanation:

The tectonic plates on Earth have been formed, and have been moving ever since their formation because of the convection currents. These currents are present in the mantle layer, which is the second layer from top to bottom. The radioactive decay of elements that are found deep inside the interior of the Earth manage to melt the rocks and metals, thus creating the magma. With its slow and constant movement, the convection currents manage to bring the heat and magma to the surface. As they have already broken the Earth's surface into multiple pieces, the magma is pushed up through the cracks, or occasionally forms new ones. That causes the creation of new crust, a crust that pushes the old crust aside, resulting in plate collision and subduction in other part of the surface, so the old crust gets into the mantle gradually and gets molten. This process is responsible for all the geological activity on the planet.