Faults in the Earth's Crust

A fault is a break in the Earth's surface that is created when crustal rock breaks and the rock surfaces move past each other. Most faults occur along tectonic plate boundaries.

When a fault forms, the block of rock that is above the fault line is called the hanging wall and the block below is called the footwall.

A normal fault is formed when tension causes the blocks of earth to pull apart and the hanging wall moves down relative to the footwall.

A reverse fault is formed when compression pushes the blocks of earth against each other and the hanging wall moves up relative to the footwall.

A strike-slip fault is formed when blocks of rock slide past each other and experience shearing stress. This type of fault is usually found at tectonic plate transform boundaries.