Multi-Plate and One-Plate Planets. Earth’s lithosphere, its rigid outer shell, is broken into 12 individual plates (red lines). Movement of these fault bounded plates is propelled by mantle convection, a mechanism driven by heat loss from Earth’s interior. Earth’s coast lines are shown (black lines). Mercury’s lithosphere by contrast, is a single, continuous plate that has been broken by many widely distributed faults (red lines). These faults are the result of global contraction driven by loss of heat from Mercury’s interior. Mercury’s smooth volcanic plains are shown (black lines).