The Witwatersrand is a 56-kilometre-long north-facing scarp in the Gauteng Province of South Africa. It consists of a hard, erosion-resistant quartzite sedimentary rock, over which several north-flowing rivers form waterfalls, which account for the name “Witwatersrand”, meaning the “ridge of white waters” in Afrikaans. This east–west-running scarp can be traced with only one short gap from Bedfordview (about 10 km west of O.R. Tambo International Airport) in the east, through Johannesburg and Roodepoort, to Krugersdorp in the west (see the diagram bottom-left below).