1. Sand dunes are asymmetrical mounds. Describe in your own words the shape of the dunes here, and where this shape comes from?
3. The Welwitschia is a shrub-like plant perfectly adapted to this desert climate and can live for over a thousand years. How many leaves has the plant?
4. Deserts are divided into four categories, Subtropical deserts, Cold Winter deserts, Polar Regions deserts, and Cool Coastal deserts like the Namib. Can you name a desert for the other three categories?
1. Sand Dünen sind asymmetrisch geformt. Beschreibe in eigenen Worten woher die Form kommt und wie sie entsteht.
2. Die Düne 45 ist wohl die bekannteste Düne hier. Woher kommt denn der Name „Düne 45“?
3. Die Welwitschia ist eine typische Pflanze der Region, hält die Hitze aus und ist der Dürre angepasst, sie kann viele hunderte Jahre alt werden. Wie viele Blätter hat denn diese Pflanze?
4. Wüsten können in 4 Kategorien eingeteilt werden, Subtropische Wüsten, Binnenwüste, Polarwüste und kalte Küstenwüste wie z.B. die Namib. Bitte nenne jeweils ein Beispiel für die anderen Kategorien.
Henzz, Namibia, Jun/29/2013
The Namib Desert is believed to be the world’s oldest desert and it has been arid for at least 55 million years. The convergence of the Benguela upwelling and the hot interior have maintained, and perhaps increased this aridity in recent times, but they did not generate the aridity. The region, isolated between the ocean and the escarpment, is considered to be a constant island of aridity surrounded by a sea of climatic change. The arid conditions probably started with the continental split of West Gondwana 130 million to 145 million years ago when this area shifted to its present position along the Tropic of Capricorn. These events led to the formation of a range of subvolcanic complexes – the so-called Damaraland Complexes – and to the deposition of flood basalts – the Etendeka Lavas. The Damaraland Complexes include some striking inselberg features of great size, including Erongo, Brandberg and Spitzkoppe.
Many investigators believe that the desert sands are derived mainly from fluvial sediment transported to the Namib coast by a perennial river about 300 km south of the Plate. The sediments are then transported north by longshore drift. Some of the sand near the coast is of marine origin, and a little sand is brought in from the Great Escarpment and beyond.
The most important climatic feature of the Namib Desert is its sparse and highly unpredictable annual rainfall. The annual mean ranges from 5 mm in the west to about 85 mm along its eastern limits. The low rainfall of the Namib has two causes. Firstly, the easterly trade winds emerging over the Indian Ocean lose most of their humidity when rising over the eastern escarpment of the Drakensberg Mountains in South Africa. On their way over the continent, they lose further moisture and reach the western escarpment of Namibia warm and dry. These air masses move down onto the low-lying Namib and produce extremely hot and dry winds. Secondly, the prevailing local southwesterly winds, cooled down by the Benguela current along the west coast of South Africa, produce an inland movement of cold air, which is overlain by the warmer, lighter air. This inversion prevents the convectional rise of the cool, humid air and thus no clouds are formed. The cool air does, however, regularly form a stable layer of fog, which is blown inland as far as 50 km. This coastal fog is the life-blood in the Namib and is an important factor contributing to the remarkably high diversity of animal life in this extremely arid environment.
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Wind as a Geologic Agent:
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