pans

pans The word ‘pan’ has at least three meanings in Earth science. In the context of soils it can refer to compacted or cemented subsurface horizons (hardpans, duripans, fragipans, etc.). In the context of geomorphology it can refer either to small weathering pits developed on rock surfaces (equivalent to rock basins or grammas), or to various types of closed depression that occur widely in many of the drier parts of the world. The last of these three meanings is the most prevalent and is the one that is discussed here.

Pans are depressions with no active outlet (i.e. they are closed) that range in size from small depressions, a few tens of metres across and only centimetres deep, to large depressions many kilometres in extent and many tens of metres deep. Many examples display a characteristic kidney-, clam-, chop-, or heart-shaped morphology. On their lee sides some pans have clay dunes or lunettes composed of sandy, silty, clayey, and salty materials blown out from the pan floor. Pans develop in a variety of settings: on susceptible rock surfaces (especially shales and fine sandstones), on desiccated lake surfaces, in inter-dune corridors, and on coastal plains. They are especially widespread in the Pampas, Kalahari, Texan High Plains, and the drier parts of Australia. Solution, tectonics, and annual activity may play a role in their development but deflation by wind is probably the crucial factor in most cases.

Andrew S. Goudie