From what we know so far, Earth is the only planet that hosts life and the only one in the Solar System with liquid water on the surface. Earth is also the only planet in the solar system with active plate tectonics, where the surface of the planet is divided into rigid plates that collide and move apart, causing earthquakes, mountain building, and volcanism. Sites of volcanism along Earth's submarine plate boundaries are considered to be potential environments where life could have first emerged.