These forces continue their work inside the earth and are not apparent from outside. These forces come into origin because of expansion and contraction of rocks due to high temperature inside the earth. These forces also come into origin because of movement of hot molten magma. When the internal moulding forces work perpendicular to the layers of the earth, then some portions of the crust become elevated and some other portions of the crust move deeper. This results in formation of continents, islands, plateau, plain, sea, etc. on the surface. The sedimentary rocks formed inside the oceans, rise and reach the inner portions of the continents. When internal moulding forces work in horizontal direction then waves are formed.
These waves cause heavy shakeup of the rocks on the crust. These results in folds, prolapse, fissures on the surface, formation mountains and valleys.
