The theory of plate tectonics
In theory the earth's crust is made of about a dozen plates which the continents and oceans rest on.The word tectonics is a word that comes from the greek word "to build" and the theory of plate tectonics is widely known by scientists in the 1960s and 1970s.There are 7 mian tectonic plates in the world; South America plate,Africa plate,Eurasia plate,North America,Pacific plate,Australia plate and Antarctic plate.