What powers the movements of plates?

Geologists have hypothesized that the movement of tectonic plates is related to convection currents in the earth's mantle. ... Tremendous heat and pressure within the earth cause the hot magma to flow in convection currents. These currents cause the movement of the tectonic plates that make up the earth's crust.

well first you need the sample of the temperature and gas level. i couldnt write a hypothesis unless i had some data. i think temperature changes will effect volumes of gas because gas changed into a solid or liquid at specific temperatures.