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.
Earlier theories (e.g. by Alfred Wegener and Alexander du Toit) of continental drift were that continents ploughed through the sea. The idea that the seafloor itself moves (and carries the continents with it) as it expands from a central axis was proposed by Harry Hess from Princeton University in the 1960s.t the Mid-Atlantic Ridge (and in other areas), material from the upper mantle rises through the faults between oceanic plates to form new crust as the plates move away from each other, a phenomenon first observed as continental drift.