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NAMIBIA
Jenny Martin
In July and August 2005 we went on a train safari to
Namibia. As Namibia is four times the area of Germany,
this was an excellent way of seeing the country. The
scenery is fascinating, the minerals very varied, the
wildlife wonderful and the geology amazing. This is just a
snippet of what we saw.
The rocks vary in age from more than 2000 million years
old, in the remnants of the Vaalian mountains that arose
when land was added to the Congo craton, still visible in
the North West, to the very recent extension of the dune
belt along the coast from Walvis Bay to Swakopmund
caused by the sparse rainfall allowing the barchan dunes to
cross the delta area of the Kuiseb river.
The first place we visited was Fish River Canyon,
photograph 1. This is second in size only to the Grand
Canyon at 90km long, more than 20km across and 549m
deep at its deepest.
evidence in the area now. When Gondwana began to break
up at about 120ma, the Atlantic ocean opened pretty well
along the present day coast, the edges of the African
continent lifted, due to equalisation and the gradient of the
river was greatly increased and began to cut down within
its existing bed through the Nama group into the
metamorphic rocks below. With the current climate the
river only flows intermittently in the rainy season.We
walked about 3 kms along the Canyon rim marvelling at
the view of meanders and islands, also enjoying the birds
and flowers. We were lucky as there had been some rain in
the previous fortnight so, although it was winter, we saw
Namaqualand daisies, desert roses and many more
varieties that we did not know.
Back to the train for a BBQ then we travelled on to Aus for
the night. On the way we had to climb up from the Fish
river gorge on to the plateau, a circuitous route crossing
dry riverbeds and gradually rising through the rock layers.
There were baboons and gemsbok and, at one point, we
were allowed to get off to take a photo of the train in the
gorge!
Next morning we boarded coaches to descend from the
plateau to cross the stone desert to Luderitz, photograph 2.
Photograph 1: Fish River Canyon
The lowest rocks are the roots of the Namaqualand
Metamorphic Complex mountains of 1500ma (million
years old) and are gneisses. 800ma dolerite dykes were
intruded. Erosion continued until 650ma when there was a
marine transgression laying down horizontal layers of
sandstones, (later to become quartzites) and conglomerates
first, then black limestones and mudstones (later to become
schists); these are the Nama Group sediments. After the
sea dried, about 550ma, once again there was a gap. 350ma
a tectonic event activated faults and a graben was formed
and it is within this graben structure the Fish river flows.
Originally the gradient was shallow and most of the
erosion was sideways producing a riverbed with meanders
and cut-offs. At this time Namibia was part of Gondwana
and as the continent got closer to the South Pole the area
was affected by the Gondwana Glaciation; the canyon was
filled by ice and further eroded, although there is no visible
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Photograph 2: Luderitz
At first there was quite a lot of feathery grass; this has deep
fleshy roots to survive the lack of rain. Here there were
ostriches, gemsbok and a herd of horses that have managed
to adapt to the conditions after being abandoned in the
First World War! As we got towards the coast, the bushes
of Ostrich grass died out and there was nothing except
sand and stone with a few low granite hills against which
the sand had piled. Right down at the coast the old railway
running alongside was buried in places by Barchan dunes;
these are the wandering dunes that move along in the wind.
Sometimes the road gets blocked but not while we were
there. We finally dropped to the coast between amazingly
Journal of the Bath Geological Society, No. 25, 2006
convoluted rocks, once again the Namaqualand Metamorphic complex, but this time black and grey dolerite,
anatexite, gneiss, amphibolite and pink granite.
Out on the peninsula it is just a rock desert with flamingos,
cormorants, gulls and fur seals. Luderitz itself is very
interesting with old (1906!) German houses and the
Church on the Rocks overlooking the harbour. We drove
out onto Shark Island and looked across to the Dune Sea
sand hills as high as the coastal mountains - that extend
from Luderitz to Walvis Bay. The sand sea is a consequence of the arid climate and the prevailing wind. The
cold Benguela Current cools the South Westerly wind
which is pushed under the warm inland air masses so that
no rain clouds form. The sand comes up the coast from
South Africa, the product of erosion in central Africa
washed down the Orange River, deposited on the coast and
blown inland.
On our way back to the train we visited the deserted town
of Kolmanskuppe, once an extremely prosperous diamond
town; and also the First World War German POW camp at
Aus. I will skip our visit to Windhoek except to mention
the descent into the graben structure in which it is situated
between the Khomas Hochland mountains to the West,
which are mica schist, and the Auas mountains to the East,
which are quartzite. Both these ranges are the eroded
remains of the Damara Mountain Building event formed
from 750ma to 650ma when the Kalahari and Congo
Cratons joined, closing the sea between them and adding to
the eventual Gondwana continent.
Our next stop was Tsumeb in the Otavi mountains, which
are well known for the lead-zinc-copper deposits, and 226
different minerals have been found. The Tsumeb ore
deposit is a hydrothermal event in an ancient dolomite pipe
that was progressively filled with breccia and sand during
the closing of the sea between the Congo and Kalahari
cratons before the mountain building and associated
magmatic activity caused the mineralisation.Unfortunately
we only had time to drive round the town as we were
visiting Etosha National Park.
The Etosha NP is in the Ovambo Basin, which was the
foreland of the Damara mountains and collected erosional
materials. Later a glacier in the Gondwana Ice Age scoured
the depression and later again it became a desert with dune
sand that became consolidated as the Etjo sandstone. After
the break up of Gondwana and the uplift of the earth’s
crust, it became the recipient of river erosion debris from
the carbonate mountains of Angola, a huge lake formed
with only the Kunene river to partially drain to the sea.
Consequently, as the climate warmed, the lake shrank and
left salt crust behind. The Etosha Saltpan makes an
excellent place for viewing game, particularly on its
Southern edge where there are springs caused by the
meeting of the Karst Otavi mountain rocks with the clays
of the saltpan. We saw desert elephants, giraffe, zebra,
gemsbok, springbok, wildebeest, dikdik, impala, jackals,
yellow and red hornbills, Koori(!) bustards, ostriches,
bateleur eagles, louries, eland, hartebeest, vultures,
secretary birds, duiker, Cape starling, goshawks, steenbok
and wart hogs. The saltpan looked blue/green from a
distance but grey up close. There were dust devils and
mirages; altogether a memorable visit.
On our way back to the train we visited another fascinating
place. Otjikoto Lake is a very deep, almost round pool of
blue/green water set in white limestone cliffs. It is where
the roof of a cavern has fallen in; there is another fairly
nearby, and they are part of an underground system in the
very old (700ma) underlying dolomite rocks. The water
was sometimes still and then the surface would be
disturbed by up-welling from below and set up overlapping
ripple patterns before becoming calm again. Looking down
one could see fish, tilapia and something smaller in the
water. It is a bit commercialised and I bought some
tourmaline and beryl from the mines.
Next morning I woke to find we were passing the cliffs of
the Erongo volcano. The upper layers are ignimbrite over
ash and lava, these on top of Karoo sediments, with granite
exposed around the bottom. It looked magnificent in the
pink dawn light. We were on our way to Swakopmund so
once again we were leaving the mountains for the coastal
desert. We travelled in the Kahn river valley and had to
climb up the Stingbank to descend to the plain. Here we
had another chance to leave the train to roam the sand and
rock with low rises of granite and a fascinating array of
rocks to collect. We came across tracks that looked like
snake tracks except they would suddenly end; eventually
we found the cause - - it was ants, thousands of them
scurrying back and forth carrying eggs and twigs. They
seemed to be relocating their nest. The track was about 20
yards long and worn about ½ inch deep!
Once again the desert was endless flat sand with a few
plants; we saw oryx, ostrich and springbok; they must be
very hardy. We left the train at Arandis, close to the
uranium mine, and boarded the buses to visit Gounikontes,
which is an oasis actually in the bed of the Swakop river.
As we crossed the desert we passed through several long
black ridges standing above the plain, some were 1m
across, up to 10m for others. These are a dolerite dyke
swarm that intruded the area 130ma with the break-up of
Gondwana. We descended through steeply dipping granites
and mica schist strata into the river gorge where there is an
olive grove and many trees. Earlier last century there was a
thriving vegetable business using the seasonal water but
the whole enterprise was destroyed in 1934 by a
catastrophic flood which they could hear coming 3 hours
before it arrived; this did not save the livestock or some of
the people! I wonder when the next one will be!
We then drove up the canyon and out on to the plain where
we stopped to look at the amazing Badland scenery carved
by the Swakop river. It was a real ‘moon landscape’ with
dozens of river beds where water must have poured over
the edge over the millennia, but it was hard to see where it
had come from; it must have been from the far away
Journal of the Bath Geological Society, No. 25, 2006
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mountains. The granite in Namibia’s arid conditions is a
soft rock as the frequent heat variation and the salt-laden
fog causes it to disintegrate into granules that then get
washed or blown away.
caused by a superheated steam eruption; red finger dunes
reaching out from the Kalihari; visiting the Giants’
Playground, balanced dolerite blocks, and the Quiver tree
forest, photograph 4, in time for sunset.
We drove along Welwitchia drive to see these strange
plants, photograph 3, which only ever have two leaves
which get longer and longer and split lengthways. Some of
the plants are immensely old and are obviously well
adapted to desert conditions.
Photograph 4: Quiver Tree Forest at sunset
Photograph 3: Plants along Welwitchia Drive
We drove down the coast between the dunes and the sea to
Walvis Bay where we visited, briefly, the salt works and
saw the flamingos in the lagoon. One of the features of
Swakopmund is the salt, sand and gypsum roads. We
walked on the beach and collected pebbles for polishing,
then watched the sun go down over the sea. This is the
only day we experienced the fog, which is amazing as it
usually a feature of the morning four days out of five.
A word about water in the desert - for many years all water
was shipped into coastal towns until it was realised that all
the water that flowed from the mountains and Escarpment
to disappear before reaching the sea must be going
somewhere! Nowadays large underground aquifers provide
enough water for everybody.
In Swakopmund there is a fascinating museum-cumjewellers called the Kristall Galerie. It has large rock
specimens outside including stromatolites, tourmaline in
situ, boulders with amethyst and many more semi-precious
stone-bearing rocks. Inside there is a collection of huge
quartz crystal clusters, the biggest is taller than a person,
weighs 14100kgs, is 520 million years old and was found
on a farm in a cavern along with several smaller clusters.
The gallery has displays of crystal clusters of tourmaline
amethyst, dioptase, sulphur, pietersite and much more.
We finally started the return journey, back to Windhoek
and across the plateau to Keetmanshoop passing dry river
beds; the escarpment running parallel for miles then
gradually receding; past Brukkaros, a carbonate volcano
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That night we left Namibia but it was not the end of the
trip. In South Africa we stopped at Upington and travelled
through the vineyards around the Orange river to visit the
Augrabies Falls, then, on our last day we popped in for a
quick visit to the Big Pit at Kimberley. All in all a
memorable trip leaving me wanting to go back; there is so
much more to see, - Spitzkoppe and Brandberg, the
Fingerklip, Sossusvlei and Waterberg to name just a few.
YET MORE LIMERICKS
Asthenosphere
The asthenosphere really is not
An inviting or welcoming spot,
For it‘s frightfully deep
(Nuff to make the skin creep)
And the climate‘s oppressively hot.
S. A. Mc Burnie
Aquifers
The aquifers under our home
Beneath filtering trees, grass and loam,
Amid layers of clay
Are a tri-tiered array
Of groundwater, cached in a dome.
Carol June Hooker
Amygdale
I‘m sure it won‘t come as a shock
That small bubbles appear in a flock
Filled with stuff of all sorts,
Such as calcite and quartz;
They‘re amygdales in igneous rock.
Sheila B
Journal of the Bath Geological Society, No. 25, 2006