Feeds:
Posts
Comments

Posts Tagged ‘brandberg mountain’

From close by it resembles a climbing wall for free climbers: Vingerklip is 35 metres high, about 15 metres wide and dotted with protruding stones. In 1973 the rock stack in the valley of the seasonal Ugab River, some 40 km east of Khorixas, was indeed conquered in free climbing manner by Udo Kleyenstuber, who ascended on its east side. The hooks which can still be seen were left by American mountaineer Tom Choate who is credited with the first ascent of Vingerklip in 1970.

For geologists, on the other hand, the erosional rock formation is like a book in which they can read stories that happened millions of years ago and shaped this landscape. They are captivating stories about sea levels dropping and rising, wet and dry phases of the climate, torrential rivers, chalky soil and rivulets that cause rocks to split. Even laypersons will notice that Vingerklip consists of different layers – layers of large stones alternate with layers of fine sand. They testify to the fact that at times the Ugab flowed rapidly enough to drag rocks with it, while at others it was so sluggish that sand was deposited in its bed.

Vingerklip/Outjo, issued in 1986, artist: Johan van Niekerk

Vingerklip/Outjo, issued in 1986, artist: Johan van Niekerk

Knowing this much it already becomes clear that it was the Ugab River that sculpted Vingerklip. These days a seasonal river which comes down in flood only after sufficient rainfalls, the Ugab rises in the western foothills of the Otavi Mountains, then passes south of Outjo and north of Brandberg Mountain to reach the Atlantic Ocean about 180 km north of Swakopmund.

Some 120 million years ago, as the southern supercontinent of Gondwana breaks up and South America drifts away, the southern African plate rises and so does its gradient to the sea level. Thus the erosional force of the rivers increases further. Southwest of Outjo the Ugab cuts its course deeper and deeper into the rock. Then, towards the end of the ice age 20 to 10 million years ago, the sea level rises again and a wetter climate prevails. The Ugab River fills the valley, which it created earlier, with rocks and sand. Layer is deposited upon layer, up to a height of 100 m.

The Vingerklip in the Ugab Valley, some 40 km east of Khorixas. Photo: Gondwana Collection

Two million years ago, during the ice age in the northern hemisphere, the sea level drops again and the Ugab once more cuts deep into its course which it previously filled with rocks and sediments. Parts of the wide riverbed fall dry. As the water evaporates, minerals precipitate – most of all lime because the Ugab and its tributaries drain the soil west of the Otavi Mountains and around Outjo which contains carbonate. The precipitated lime works like cement and binds rocks and sand into a conglomerate which is as hard as concrete. The deeper the river cuts into its original bed the narrower it becomes, forming several terraces over time.

The ‘cement’ in the conglomerate, i.e. the lime, is dissolved again by rain. This results in rivulets and streams which gradually cut into the terraces as if they were a cake. Erosion continues to gnaw on the edges of these pieces of cake, causing them to shrink and the gaps between them to widen as time passes. Vingerklip is the remainder of one such piece of cake, albeit not the only one: from its base another two, larger terrace islands can be seen in the Ugab Valley.

Furthermore, three different terraces can be distinguished. There is the ‘old’ main terrace, the plateau of which now rises some 160 m above the current riverbed, while the surface of a younger terrace lies about 100 m and that of the youngest one some 30 m above the Ugab.

Since this area does not experience much rain, chances are that Vingerklip will remain for years to come. It sits on a sound wide base with a circumference of 44 metres – in contrast to the Finger of God in southern Namibia, which collapsed in December 1988.

Advertisements

Read Full Post »

Gladiator, issued in 2003, artist: Helge Denker

Gladiator, issued in 2003, artist: Helge Denker

At the start of this millennium Namibia caused worldwide headlines when biologists found a mysterious insect on Brandberg Mountain which did not fit into any known genus, family or order. In the end a whole new order had to be established – for the first time since 1914. Thus some scientists felt that the discovery of the ‘gladiator’ was as sensational as finding a life mastodon or sabre-toothed tiger.

The predatory insect was nicknamed ‘gladiator’ because parts of it are covered with spiky armouring reminiscent of the legendary warriors of ancient Rome. The name ‘heelwalker’ is also used by some because the insect always points the feet on its hind legs away from the ground and puts down the heels only.

The scientific name Mantophasmatodea is derived from Mantodea (the praying mantis) and Phasmatodea (the stick insect). The gladiator, unlike the praying mantis, grabs its prey with both its fore and mid legs, and in contrast to the stick insect its first body segment is the largest. Nor does it feed on plants.

Between 1.5 and 4 cm long, the gladiator has a size that made many scientists wonder why it took so long to notice this insect. It does, however, live rather inconspicuously: it is nocturnal and prefers to stay in the shelter provided by clumps of grass and rock crevices. Males are smaller than females and have to beat a hasty retreat after mating, otherwise they may get eaten.

The discovery of the gladiator insect turned into a piece of detective work: At the Max Planck Institute for Fresh Water Research in Plön, Germany, Ph.D. student Oliver Zompro is busy examining a fossil insect trapped in a drop of amber which is 45 million years old. He concludes that the insect cannot be classed with any of the known categories and turns to the Museum of Natural History in Berlin. There he comes across a specimen which appears to be related to his object of research and which had been collected in the German colony of South West Africa in 1909. Reason enough for the exciting assumption that an insect, which over the past 45 million years became extinct in Europe, had possibly survived in Africa.

Enquiring at the insect department of the National Museum in Namibia he learns that indeed they have a similar insect – in fact it was received only a few days earlier. Namibian biology student Martin Wittneben found it on an excursion to Brandberg Mountain in north-western Namibia. The tiny creature had come into his camp and he was unable to identify it. This was a very lucky coincidence, as Wittneben had of course taken down the GPS coordinates.

The predatory gladiator insect in its typical environment at the Fish River Canyon. Photo: EduVentures

The predatory gladiator insect in its typical environment at the Fish River Canyon. Photo: EduVentures

Zompro decided to travel to Namibia. In March 2002 he joined an expedition to the Brandberg, jointly sponsored by Conservation International, the Max Planck Institute and the National Museum of Namibia. The team consisted of 16 entomologists from Germany, Britain, South Africa, Namibia and the United States. The scientists were dropped onto Brandberg and began a painstaking search on the stony, arid summit. Zompro collected a dozen of the insects and carried them back to his lab in Germany to study mating, feeding and other forms of behaviour in the insects. Aggressive tendencies became one area of interest — a couple of the insects apparently were eaten during the trip back.

After in-depth research it can be stated without doubt that this insect does not belong to any known genus, family or order. The last time this happened was in 1914. And so another new order was added to the 30 known ones – the gladiator or Mantophasmatodea.

Since then some 20 gladiator species have been identified and divided into 10 genera and 3 to 4 families. These species have so far only been found in southern and east Africa – more precisely in Namibia, South Africa and Tanzania.

In Namibia, by the way, Brandberg is no longer the only site where gladiators have been found. The inconspicuous predatory insect also occurs at the Fish River Canyon. On an expedition arranged in 2006 by EduVentures, an initiative of the National Museum of Namibia, to the northern parts of Gondwana Cañon Park biologists and students unexpectedly discovered three gladiator specimens.

Read Full Post »

%d bloggers like this: