The Earth’s crust is split into gigantic pieces called tectonic plates. These plates are in constant motion, propelled by currents in the Earth’s upper mantle. Hot, less-dense rock rises before cooling and sinking, giving rise to circular convection currents which act like giant conveyor belts, slowly shifting the tectonic plates above them. Hawaii sits in the middle of the Pacific Plate, which is slowly drifting north-west towards the North American Plate, back to Alaska. The plates’ pace is comparable to the speed at which our fingernails grow.