This leads the tectonic plates on top to slowly jostle one another.
The movement also creates gaps in tectonic plates, which reduce the pressure on the mantle beneath it, allowing it to melt and push through.
The mantle makes up 84 percent of Earth's volume, and though it's solid rock, over the course of millions of years, it behaves like a liquid.
The buildup and sudden release of friction from this movement can cause earthquakes.