A fault is a fracture in rock where displacement has occurred due to movement of the Earth. There are three main types of faults defined by the direction of movement: normal faults create space by pulling rock apart; reverse faults squeeze rock by pushing two blocks on top of each other; strike-slip faults involve horizontal movement with little vertical displacement. Examples of fault systems in the Philippines include those near Laoag City, the Marikina Valley, near Borongan, and in General Santos City.