The History of the Atom 5: The Modern Theory investigates the development of modern atomic theory. Greek philosophers Leucippus and Democritus first developed the concept of the atom in the 5th century B.C.E.
Therefore, based on the concepts of the continental drift and other developing ideas at the time, a general theory was developed, which is now known as the plate tectonics. Plate Tectonics. Plate tectonics is the theory explaining the motion of the outer crust or the lithosphere of earth. Lithosphere is divided into tectonics plates. Two main types of tectonics plates are the oceanic crust and continental crust. Oceanic crust is mainly composed of Silicon and magnesium, hence called SIMA.
We are not sure when this process began. Continental drift squashes and changes the continents so much that it is very hard to work out their early history. Continental drift is still happening today and is important because it causes volcanic eruptions, earthquakes and tsunamis. Some people also think that it is one cause of ice ages. Today the theory of plate tectonics, which includes continental drift, forms a framework for the study of geology and the Earth. For the evidence that continental drift is happening, click here.