The map shows the lithological properties of the surface geology of Africa. Lithology describes the mineral composition and structure of geological material which is based on rock formation (i.e. whether it is igneous, sedimentary, metamorphic) and mineralogy (e.g. carbonate, silicic, mafic). This map is a good proxy for soil parent material as it only reflects surface conditions and not the underlying bedrock. It should be noted that the general nature of this map means that at a local level, the conditions may be quite different to that shown. Other than the terms alluvium (deposited by water), aeolian (deposited by wind), organic (peat deposits) and colluvium (transported by gravity), all of which denote recent deposition, the age of material is not indicated. The preponderance of wind-blown sediments across Africa is striking as are the volcanic areas.