Riverwash is unstabilized sandy, silty, clayey, or gravelly sediment that is flooded, washed, and reworked frequently by rivers. Rock outcrop consists of exposures of bare bedrock other than lava flows and rock-lined pits. Many rock outcrops are too small to be delineated as areas on soil maps but can be shown by spot symbols. Some areas are large, broken by only small areas of soil. Most rock outcrops are hard rock, but some are soft.
Rubble land consists of areas of cobbles, stones, and boulders.
Rubble land is commonly at the base of mountains but some areas are deposits of cobbles, stones, and boulders left on mountainsides by glaciation or by periglacial processes. Salt flats are undrained flats that have surface deposits of crystalline salt overlying stratified very strongly saline sediment. These areas are closed basins in arid regions. The water table may be near the surface at times. Scoria land consists of areas of slaglike clinkers, burned shale, and fine-grained sandstone remaining after coal beds burn out.