Well, at first the world formed Pangea, all one land. But then the Continential Drift took place, lasting over millions of years and then Pangea was split. Now we have our sev
…en continents. The inner core of the Earth is believed to be at a temperature of about 5700 degrees C. This is caused mainly by radioactivity, but maybe a small bit of gravitation compression as well. The next layer out is only a slightly lower temperature - but is molten (remember volcanoes), or at least somewhat liquid. These deeper layers are made of denser rocks, and on top of them float some lighter rock assemblies - the continents. The convection forces in the liquid layers move the floating continents around - in patterns that we don't yet understand. This is called Plate Tectonics. Occasionally (in geological terms), these floating bodies join together - the last time was about 250 Mya (million years ago). Folk have given the name Pangaea to this super continent. It gradually broke up, first into two major parts, then into more fragments - the lands and continents of our present Earth. This pattern has believed to have happened at least two other times in the history of the Earth. And the process continues. (MORE) 
