It is believed to have see-sawed between an arid and semi-arid state for at least 80 million years, but there where times when there where more rivers and surface waters.
Not all of the landscape features that we see today, however, are of a venerable age.
They have been modified and changed greatly over the ages by the forces of water, wind, heating and cooling.
The Namib Desert forms a narrow ribbon along the coastal plain, rarely more than 200 kilometers wide and bounded in the west by the cold oceanic waters and in the east by the escarpment known as the Khomas Hochland.
The Namib can be divided into a number of distinct units for convenience of description: the vast sand dune oceans, extensive gravel and calcrete plains, hill ranges and massive granitic inselbergs, seasonally flowing rivers, perennial rivers in the north and south, and the coastal plain.
Apart from the Orange River which forms part of the international border between Namibia and South Africa, and the Kunene in the north, separating western Angola and Namibia, all of the others rivers flow only after good rains have fallen in the highlands.
A few of these rivers, such as the Kuiseb and Swakop, flow more frequently than others, and in the case of the former this plays a crucial role in preventing the mighty longitudinal sand dunes from relentlessly marching north-wards.
Questa foto di Namibia è offerta da TripAdvisor.
Many of these rivers have names that evoke something of the mystery of this desert: Hoarusib, Hoanib, Uniab, Huab, Ugab and Orawab.
These river courses allow many non-desert adapted creatures and plants to penetrate what would otherwise be a totally hostile environment for them.
If we take one of these rivers, the Kuiseb, as an example, we find around it a great spectrum of both desert-adapted species, as well as those that would perish without this lifeline.
This river also prevents the southern sands spilling northwards.
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