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Sandy
Offspring of the Drakensberg Mountains
To the left it is dune to dune behind dune and next
to dune – an endless sea of reddish sand stretching
all the way to the distant horizon. On the right it
is vast plains in shades of grey and beige with the
occasional inselberg jutting out. In between, a sandy
dry riverbed is lined by greenery. The Namib Desert
is a narrow tract of land, only about 100 km wide, along
the coast of the country to which it gave its name.
It is a desert with several faces. This is spectacularly
evident in the southern half of the Namib along large
river courses like that of the Kuiseb or Koichab. |
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Generally the
Namib is considered to be the entire dry zone extending
from southern Angola through Namibia right down to South
Africa. Scientists, however, prefer to draw the border
at the tarred road from Lüderitz to Aus. The area
south of that line is referred to as the Succulent Karoo.
Based on these geographical perimeters the Namib is
the narrow strip between the winter rain system in the
south-west and the summer rain area in the north-east.
Annual precipitation is highly irregular and varies
between 5 and 85 mm, depending on the area; the water
deficit factor is 25 to 150. Coastal fogs, at times
moving as far as 60 km inland, provide an essential
source of moisture. Temperatures may rise up to 40 degrees
in summer and drop to about 2 degrees in winter. The
dry riverbeds, with their subterranean reserves of water,
represent vital oasis lines across the plains. |
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Biologically
the Namib is subdivided into three vegetation types:
the mountainous northern desert with changing landscapes
and a sparse growth of grasses on varying soils, the
central gravel plains with some shrubs and grasses,
and the sand-sea of the south. On the whole the picture
is dominated by annual grasses and small plants which
grow rapidly after rainfalls; bigger shrubs or even
trees are usually found only along the river courses.
Despite the sparse vegetation the Namib Desert sustains
a large variety of animals. They have adapted to their
habitats in imaginative ways and developed the most
amazing mechanisms of survival. There are 30 endemic
vertebrates, including the Side-Winder Adder which leaves
a striking pattern when moving on the dunes, as well
as the Dune Lark and the Golden Mole, a mole-like rodent
without eyes. |
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With
an age of more than 20 million years the Namib
is considered to be the oldest desert on earth.
In its current form, however, it 'only' evolved
about 5 million years ago when South America and
Antarctica split up and ocean currents developed
around the new polar continent. This was the hour
of birth of the cold Benguela Current which plays
a major role in maintaining the arid conditions
along the west coast of southern Africa. This
current prevents the air from absorbing much moisture.
Due to inversion (warm layers of air on top of
cool layers) there are no turbulences, a prerequisite
for the build-up of cloud. Therefore, no rain
can be expected from the Atlantic. Condensation
only results in fogs which, mainly at night, may
move far inland.
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Finally, the great mountains of sand
which make up the Dune Namib are a stupendous monument
to the immense forces of nature. As unlikely as it may
seem, this sand is erosion material from the Drakensberg
Mountains and other geological formations in the interior
of the southern African subcontinent. Over millions
of years the Orange/Gariep River washed the weathered
debris into the Atlantic Ocean where the Benguela Current
transported it north and deposited it along the coast.
Strong south-westerly winds blew the sand into the interior
and in the course of 2 to 3 million years swept it up
into mountains. |
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Humans have
dwelt in the Namib only sporadically: rock art and stone
tools can be found under the ledges of inselbergs in
the middle of the desert. About 200 years ago the Topnaar
Nama settled at the lower course of the Kuiseb River. |
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