Badlands. View across the Badlands National Park in South Dakota, USA. Badlands is a term applied to this type of terrain, where horizontal beds of unconsolidated sedimentary material with little vegetation cover is cut across by deep, interlocked ravines. The ravines are formed by seasonal deluges of rainwater, followed by differential weathering and wind erosion. The name of this type of terrain comes from early French explorers, who described the landscape as 'mauvaises terres a traverser' ('bad lands to cross'). This type of terrain is also seen in other parts of the USA, in Algeria and in Morocco.