hogback, sharp-crested ridge with steep slopes on both sides, formed by the erosion of steeply tilted rock layers. Hogbacks are commonly formed along the eroded flanks of large, tightly folded anticlines and synclines (see fold). Impressive hogbacks are seen in the foothills east of the Front Range of the Rocky Mts. in Colorado, where they are formed by the vertical or steeply dipping layers of Dakota sandstone. This region forms the intake area for the Dakota artesian system. Hogbacks are also common in the Black Hills of South Dakota where sedimentary rocks were uplifted by the intrusion of Black Hills granite. See cuesta.