footwall

Footwall is a term used in structural geology and mining to denote the rock block on one side of a fault plane or ore vein that lies below the plane relative to the hanging wall. The opposite block is called the hanging wall. The designation is relative to the fault geometry and is commonly used to describe displacement, stress, and the contact relations of rock masses.

In faulting, movement along the fault displaces the footwall and hanging wall relative to each other by the slip on the fault; the footwall block may remain intact while the hanging wall moves, or vice versa. The interaction of these blocks helps characterize fault mechanisms and the distribution of stresses in the crust.

In mining and ore deposit contexts, the footwall is the rock beneath an ore body or vein; mine design, ground support, and extraction methods depend on the strength and structure of the footwall. For example, if the footwall is weak or fractured, backfill and support are adjusted to maintain stability; in dipping ore bodies, the footwall contact may control the geometry of the stopes and affects roof and floor control.

Origin of terms: The terminology derives from historical mining practice. The hanging wall would “hang” above the footwall, and the name is carried into structural geology to describe the relative positions of rock masses across a fault or ore contact. The terms are relative and depend on the reference frame along the fault or vein.