Did you enjoy doing the Micro Geology Quiz yesterday? (See the post just below.) Now it's time to step way, way back and look at one of the biggest things on Earth, in my new article on supercontinents. These are what happens when the wandering continents, and various smaller bits of continental crust, happen to glom together in one big landmass. Supercontinents appear to have formed four times in Earth history, and another one appears to be coming up starting in about 50 million years.
Some people wonder if such a thing would knock Earth off balance, but it wouldn't, for the same reason that melting icebergs don't change the sea levelthe simple physics of buoyancy sees to that. The question we don't have a perfect answer for yet is what supercontinents do to the circulation of the mantle underneath them. It is clear, though, that supercontinents aren't any more stable than other plate-tectonic arrangements, because they have always broken apart after a while.