3-D sketch of a half graben. A half graben is a topographic depression that forms as a result of movement on a normal fault (in this case, the normal fault is called the border fault, because it forms one of the borders or boundaries of the half graben). The hanging-wall block (block of rock above the fault, in this case, the block to the right of the fault) of a normal fault moves down whereas the footwall block moves up. Layers of sediment can accumulate within this depression. The sediments are commonly eroded from the uplifted footwall block. If the climate and other conditions are right, a lake may partially or completely fill the half graben. Modified from Schlische (1994).