A fault is a rock fracture where blocks of rock have slipped past each other.
Faults usually occur in fault zones, which are often along the boundaries between tectonic plates. Faults are typically caused by earthquakes.
Single earthquakes rarely move blocks more than a few centimeters. Repeated small earthquakes can shift blocks hundreds of kilometers.
Compression faults are faults caused by rocks being squeezed together, perhaps by converging plates.
Tension faults are faults caused by rocks being pulled together, perhaps by diverging plates.
Normal, or dip-slip, faults are tension faults where the rock fractures and slips straight down.
A wrench, or tear, fault occurs when plates slide past each other and make blocks slip horizontally.
Large wrench faults, such as the San Andreas in California, USA, are called transcurrent faults.
Rift valleys are huge, trough-shaped valleys created by faulting, such as Africa’s Great Rift Valley. The floor is a thrown-down block called a graben. Some geologists think they are caused by tension, others by compression.
Horst blocks are blocks of rock thrown up between normal faults, often creating a high plateau