The surface is generally very unstable and erodes easily. Trafficability is very poor. Areas of hard gypsum are mapped as Rock outcrop. Lava flows are areas covered with lava. In most humid regions, the flows are of Holcene age, but in arid and very cold regions they may be older.
Most flows have sharp, jagged surfaces, crevices, and angular blocks characteristic of lava.
Others are relatively smooth and have a ropy glazed surface. It includes slush pits and adjacent areas affected by the liquid wastes. The land is barren, although some of it can be reclaimed at high cost. Pits are open excavations from which soil and commonly underlying material have been removed, exposing either rock or other material. Commonly, pits are closely associated with Dumps.