PLATE TECTONICS by Matthew The Earth's crust is broken into nineteen giant land masses and a few smaller ones.  These huge pieces of crust fit together like a giant jigsaw puzzle.  They are solid rock and float on top of the mantle which is hot, molten rock. The rock in the mantle that is closest to the crust cools down and the rock closest to the core is heated up.  This causes convection currents in the mantle and the liquid rock rises and falls, acting a bit like a big conveyor belt.  Scientists think that this causes the movements of the plates. Scientists think that the plates were once one large piece of land which was a "super continent" called Pangaea.  Pangaea separated into two huge landmasses, Gondwanaland, which had the continents that made up the Southern Hemisphere, and Laurasia, that had the Northern Hemisphere continents. Over the last 200 million years the plates that made up these giant landmasses have separated and moved slowly into the positions they are today. The plates continue to move about 4cm a year, either towards each other or away from each other.  This causes earthquakes and volcanoes. Click HERE to return to the index.