Asked by: Cassy Swan, Leicestershire
The idea that the Earth’s fragmented crust drifts over the hot mantle beneath, often creating earthquakes and volcanoes, only gained widespread acceptance in the 1960s. Some planetary geologists believe that certain surface features on Mars, and the fact that it had active volcanoes during its earliest phase, indicate that the Red Planet may also have several crustal plates.
Apart from this possibility, which is as yet unconfirmed, Earth appears to be unique in the Solar System in having plate tectonics, driven by huge convective loops of hot rock. This may be because the Earth’s interior has remained warm enough for the material to flow easily, and possibly because the Earth’s crust is relatively thin, and so more easily cracked to form plates.
Subscribe to BBC Focus magazine for fascinating new Q&As every month and follow @sciencefocusQA on Twitter for your daily dose of fun facts.