Earth science is known as plate tectonics. Plate tectonics might be thought of as the process by which the Earth is resurfaced. As the result of seafloor spreading, new crust and lithosphere is created by the flow of magma from the mantle to the near surface, through fissures, where it cools and solidifies. Through subduction, oceanic crust and lithosphere returns to the convecting mantle. Areas of the crust where new crust is created are called "divergent boundaries", those where it is brought back into the Earth are "convergent boundaries" and those where plates slide past each other, but no new lithospheric material
Lithosphere felsic rocks. Oceanic lithosphere thickens as it ages and moves away from the mid-ocean ridge. This thickening occurs by conductive cooling, which converts hot asthenosphere into lithospheric mantle and causes the oceanic lithosphere to become increasingly thick and dense with age. In fact, oceanic lithosphere is a thermal boundary layer for the convection in the mantle. The thickness of the mantle part of the oceanic lithosphere can be approximated as a thermal boundary layer that thickens as the square root of time. Here, formula_2 is the thickness of the oceanic mantle lithosphere, formula_3 is the thermal diffusivity (approximately 10 m/s)