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 Holocene 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. A little earthy material may be in a few rocks and sheltered pockets, but the flows are virtually devoid of plants other than lichens. 2 Oil-waste land consists of areas where liquid oily wastes, principally saltwater and oil, have accumulated. 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.