The lithosphere and the origin of continents

The idea that the solar system and the Earth formed from the joining of dust and gas particles in space was put forward by R. Descartes (1644), I. Kant (1755) and P. Laplace (1796), so it is called the Descartes–Kant–Laplace hypothesis. Inside the Earth, matter was sorted: lighter material rose to form the crust and heavier material sank to form the mantle and core. The idea that continents move is called mobilism: the German scientist A. Wegener supported it in 1912, saying that about 200 million years ago there was a single supercontinent, Pangaea, which split into Laurasia and Gondwana and then into today’s continents. As evidence he cited how the coasts of Africa and South America fit together. The textbook says that Abu Rayhan Beruni (973–1048) expressed a similar thought much earlier. In the late 1960s (1968) the new mobilism — plate tectonics — was created; according to it plates move a few centimetres a year because of flows of material in the asthenosphere. At mid-ocean ridges plates move apart and new oceanic crust forms; spreading is also seen in the East African Rift, Lake Baikal and the Red Sea. Today most scientists accept this hypothesis.