A break in the Earth's crust is called a fault. According to Dictionary.com, a fault in geology is a fracture in the Earth's crust that results in the displacement and loss of continuity of rocks on either side of the fracture plane. A fault is the result of plate-tectonic forces.
There are various types of faults, including a normal fault, reverse fault, strike-slip fault and transform fault. Normal faults occur when rocks above the fault plane move down to the rocks below the plane and cause rocks to pull apart, while reverse faults are the result of rocks moving upward to the rocks below the plane. Strike-slip faults are the result of shearing stress that causes rocks to slide parallel to the fault line, and transform faults occur when a crack occurs in part of two tectonic plates' boundary.