Fault
A fault is a surface along which rocks slide past one another. A fault scarp is a "steep-slope or cliff formed directly by movement along a fault and representing the exposed surface of the fault before modification by erosion and weathering" (Bates and Jackson, 1980, p. 224). The motion of faults is described in a relative sense. The hanging wall is the "overlying side of an orebody, fault, or mine working; esp. the wall rock above an inclined vein or fault" (Bates and Jackson, 1980, p. 283). The footwall is the "underlying side of a fault ... esp. the wall rock beneath an inclined fault" (Bates and Jackson, 1980, p. 241).
Photograph by D.A. Swanson, June 24, 1971, U.S. Geological Survey.
For most of the surface faults on Kilauea, the hanging wall has moved down relative to the footwall to produce a normal fault. Normal faults are common in areas that are undergoing extension. The fault scarps of the Hilina fault system are the major landforms in the coastal area of the park. These fault scarps are as high as 1,600 feet (490 m), resulting of seaward movement of unsupported rocks over thousands of years. Halape is on the coast along the right margin of the photo.
