Answer: The theory states that the earth's crust is divided into massive slabs known as tectonic plates.
Step-by-step explanation:
These plates move on the mantle which is a layer made of magma, which consists of semisolid rocks.The heat from earth's core causes convection currents much like in a beaker full of water.But, here the force developed by the magma is so great that it slowly moves the plates like boats on sea over millions of years.