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2.01 Topography of southern Africa and surrounding marine bathymetry1

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On average, the subcontinent of southern Africa stands higher than other continental interiors. Rising from coastal lowlands, the subcontinent has a fringe of highlands on its western, southern and eastern margins which are 1,500–2,000 metres above sea level (masl) on average, but reach as high as 2,500 metres in the west and almost 3,500 metres in the east. These highlands encircle the lower-altitude interior of the subcontinent, which ranges between 1,000 and 1,500 metres above sea level. As high as some of southern Africa's highlands are, the surrounding oceans are deeper with the seabed dropping away to depths of more than 5,000 metres below sea level (mbsl).

A large area of the interior of southern Africa – the Kalahari Basin – filled with sediments forms a vast sea of sand. The basin extends 3,000 kilometres from the Northern Cape of South Africa, across most of Botswana and eastern Namibia, through much of Angola and northwards into the Democratic Republic of the Congo. From west to east, the basin is 1,500 kilometres at its widest extent. The Kalahari is generally held to be Earth's largest continuous area of sand. It underlies about half of Namibia: all of Zambezi, Kavango East, Kavango West, Ohangwena and Oshana regions, most of Omusati and Oshikoto, and large areas of eastern Otjozondjupa, Omaheke and Hardap.

Some of southern Africa's rivers flow into the Kalahari Basin and end there in large inland wetlands where waters percolate into the flat, sandy landscape or evaporate. These wetlands include the Okavango Delta, Makgadikgadi Pans, Etosha Pan, Linyanti Swamps and Lake Liambezi. Many of them were much bigger in the past when rainfall was higher.2 Other rivers have found their way through the margin of highlands and flow down to the sea, the best examples being the Kunene, Orange and Zambezi rivers. Many other rivers have their headwaters in the subcontinent's fringe of highlands and progressively erode the mountains as they flow to the coast.