SAND
When admiring the spectacular view of the Namib
dunes one can sometimes forget about the smaller detail. Scoop up a handful of sand, let it trickle through
your fingers, smell it, literally get the feel of the dunes. Scoop some sand into the
palm of your hand, then take binoculars and use them wrong way around to have a look at the particles of sand
in your hand. The colours will amaze you, from white quartz to red garnets, the blacks and yellows, all
in the palm of your hand.
Scientists tell us that sand must not be larger
than 2.0 mm, or smaller than 0.05 mm in diameter. If bigger it is classified
as gravel and if smaller silt, and then clay. Sand is simply large rock formations that have been eroded over
millions of years. A granite boulder will be eroded by wind and water, and later this little piece of rock
will slowly find its way into a river wash. Once the river comes down,
this little piece will be banged against other rocks and polished smooth.
These little pieces of rock will find their
way into the ocean, where they accumulate and then get compressed by heavier material. The chemical action of the
ocean “cement” these layers, and thus sandstone is formed. Once the ocean level drops
the sandstone is once again exposed to wind and weather, and the erosion process starts
again.
According to the scientists most of the sandstone
was formed in the Southern Namib, where it was transported to the ocean by the Orange River.
From here it was moved North by the Benguela current, and then thrown out onto
the beached of the Namibian coastline. Once on the coast, the
predominantly south-westerly wind will continue the journey of this grain of sand.
To complete the life cycle of a grain of sand, it
gets polished by all the other sand particles around. Getting wet from the fog and
then drying in the hot sun again, caused the grains of sand to form a translucent film over
them. Call
if “frosting” if you want. The last process that gives the orange colour to the sand is known as
oxidation.
From sandstone to sand, transported thousands of
kilometres, getting polished, and that is maybe how the sand of the Namib dunes was formed.
At sunset the orange colour of the dunes can become a deep red, and that is
exactly why it is so fascinating in the dunes. It is never the same from
hour to hour.
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