It's convection cells, not unlike water boiling in a kettle, the atmospheric circulation that gives us weather, or the ever-so-slow churning of solid rock in Ea

It's convection cells, not unlike water boiling in a kettle, the atmospheric circulation that gives us weather, or the ever-so-slow churning of solid rock in Earth's mantle that gives rise to volcanism and plate tectonics. The timescales are very different, though.