A fault block is a section of the Earth's crust that has been displaced due to geological faults. These faults are fractures in the Earth's surface where rocks on either side have moved relative to each other. Fault blocks can be uplifted or lowered, creating various landforms such as mountains or valleys. In geology, fault blocks are often studied to understand tectonic activity and the formation of landscapes. They can be categorized into different types, such as normal faults, reverse faults, and strike-slip faults, each describing the direction of movement along the fault line.