How do earth's plates move?

Plate tectonics move because they are carried along by convection currents in the upper mantle of the planet (the mantle is a slowly flowing layer of rock just below Earth's crust). Hot rock just below the surface rises and when it cools and gets heavy, it sinks again.

Explination:

I learned about it :)

b. read the phase at the intersection of any given temperature and pressure.