What causes sea-floor spreading and continental drift?
Seafloor spreading occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. Seafloor spreading helps explain continental drift in the theory of plate tectonics. Earlier theories (e.g., by Alfred Wegener and Alexander du Toit) of continental drift were that continents “plowed” 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[1]. The theory is well-accepted now, and the phenomenon is known to be caused by convection currents in the plastic, very weak upper mantle, or asthenosphere. Continental drift theory has been replaced by the science of plate tectonics, an all inclusive explanation of the process of continent movements, crust creation, lithologies, subduction, the rock cycle, and so on. The engine behind plate tectonics is heat from the interior of the Earth. This
