Plate tectonics is the process that underpins much of our understanding of the Earth. It explains many aspects of the Earth, from magnetic patterns in oceanic rocks to the distribution of plants and animals. How unusual is it? Well, it doesn’t seen to be happening on other rocky planets in our solar system. Many geologists have argued that plate tectonics wasn’t active during the earth’s early history. As astronomers find many rocky planets in other solar systems, the question of understanding how ‘typical’ plate tectonics has implications beyond the earth. How long has it been going on – how old is it?