Basin and range topography results from crustal extension (extensional tectonics). As the crust stretches, faults develop to accommodate the extension. For example, in the western United States, this topography is built by a number of normal faults that meet at a basal detachment fault. The basins are down-fallen blocks of crust and the ranges are relatively uplifted blocks, many of which tilt slightly in one direction at their tops due to the motion of their bottoms along the main detachment fault.