What is the difference between a footwall and a hanging wall?
The Correct Answer and Explanation is:
The footwall and hanging wall are terms used to describe the two blocks of rock that form the two sides of a fault in geology. A fault is a crack or fracture in the Earth’s crust along which movement has occurred.
- Footwall: The footwall is the block of rock that lies beneath the fault plane. Imagine standing on the fault and looking up; the block beneath your feet would be the footwall. It is so named because it represents the “foot” or the lower part of the fault. In normal faults, where the hanging wall moves downward relative to the footwall, the footwall remains relatively stationary or moves upward.
- Hanging Wall: The hanging wall is the block of rock that lies above the fault plane. It is called the “hanging wall” because, if you were standing on the footwall, the hanging wall would be the block that appears to be suspended above you. In a reverse fault, where the hanging wall moves upward relative to the footwall, the hanging wall is pushed up over the footwall.
Explanation of Fault Types:
- Normal Faults: In a normal fault, the hanging wall moves downward relative to the footwall. This usually occurs when tectonic forces pull the Earth’s crust apart, resulting in an extensional environment (where the crust is being stretched). This type of fault is common in areas undergoing rifting or where the Earth’s crust is being pulled apart.
- Reverse (Thrust) Faults: In a reverse or thrust fault, the hanging wall moves upward relative to the footwall. This happens in regions where the crust is being compressed, such as at convergent plate boundaries, where one tectonic plate is being pushed over another.
In summary, the footwall is the lower block of rock, and the hanging wall is the upper block of rock in a fault system. The relative movement of these two blocks gives rise to different types of faults, such as normal or reverse faults.
