These huge irregularly shaped pieces fit together like a jigsaw.
The plate tectonic idea helps to explain volcanoes and earthquakes,
It also explains mountain formation, and deep-sea trenches.
Around 200 million years ago there was one huge supercontinent, Pangaea.
Over millions of years the plates moved, by only a few centimetres each year.
The speed is about the same as the rate fingernails grow.
The supercontinent split up to form the continents we have today.
Evidence for plate tectonics comes from many areas of science.