Faults A fault is a surface or zone of rock fracture, where there has been displacement of land from a few centimeters to a few kilometers in scale. Faults are classified by direction of movement. In order to classify the types of fault, geologists have adopted the terms hanging wall block and footwall block from early miners who found mineral deposits along fault zones. Your feet are on the footwall block with the hanging wall block over your head.
All movement is parallel to the dip of the fault plane.
One block moves up or down in the opposite direction of the block on the other side of the fault. Normal faults are characterized by the hanging wall moving downward relative to the footwall. An example of a normal fault in the Gorge is the Hood River fault. If the hanging wall moves upward relative to the footwall, it is called a reverse fault . An example of a reverse fault in the Gorge can be seen along the west side of the water gap in the Columbia Hills west of The Dalles, Oregon.