Earth’s interior processes produce flows of heat and material toward the surface to form crust. These processes drive plate tectonics and are responsible for nearly all other internal processes of volcanism, folding, and faulting. Further, there are four main causes of Earth’s movement. They are magma movement within the earth’s crust, gravitational force, and convectional currents in the mantle and isostatic adjustment.
The lithosphere is a mosaic of plates floating over the asthenosphere (Fig. 5). The total number of plates is yet to be discovered, but the recognized numbers are seven major plates, seven intermediate-sized plates, and six smaller plates.
Fig. 5 – Layers of Lithosphere and Asthenosphere
Movements at the boundary between two plates can explain the nature of landforms found in these areas. Where plates are moving apart there are divergent plate boundaries (constructive plate margins) (e.g. at the mid-ocean ridge) where the new crust is formed. When two plates move towards one another, at a convergent plate boundary (destructive plate margins), major physical features are formed. If one of the plates slides beneath the other, a subduction zone is formed and lateral sliding along plate boundaries, called transform movement.
The surface of the Earth is shaped by the physical agents of change. The earth movements are divided on the basis of the forces that cause them. These forces are called as endogenic and exogenic. The endogenic forces are the internal processes that produce flows of heat and material from deep below Earth’s crust. The exogenic forces involve external processes – above the Earth’s crust, that set into motion air, water, and ice, all powered by solar energy.
Endogenic forces produce moving, warping, and breaking of Earth’s crust (earthquakes and volcanic eruptions). The endogenic forces produce carve, shape, and reduce the landscape by the process like weathering (breaks up and dissolves the crust).