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The Namib is a coastal desert in southern Africa. The name ''Namib'' is of Nama origin and means "vast place". According to the broadest definition, the Namib stretches for more than along the Atlantic coasts of Angola, Namibia, and South Africa, extending southward from the Carunjamba River in Angola, through Namibia and to the Olifants River in Western Cape, South Africa. The Namib's northernmost portion, which extends from the Angola-Namibia border, is known as Moçâmedes Desert, while its southern portion approaches the neighboring Kalahari Desert. From the Atlantic coast eastward, the Namib gradually ascends in elevation, reaching up to inland to the foot of the Great Escarpment.〔 Annual precipitation ranges from in the most arid regions to at the escarpment, making the Namib the only true desert in southern Africa.〔〔 Having endured arid or semi-arid conditions for roughly 55–80 million years, the Namib may be the oldest desert in the world.〔〔 The desert geology consists of sand seas near the coast, while gravel plains and scattered mountain outcrops occur further inland. The sand dunes, some of which are high and span long, are the second largest in the world after the Badain Jaran Desert dunes in China.〔 Temperatures along the coast are stable and generally range between annually, while temperatures further inland are variable—summer daytime temperatures can exceed while nights can be freezing.〔 Fogs that originate offshore from the collision of the cold Benguela Current and warm air from the Hadley Cell create a fog belt that frequently envelops parts of the desert. Coastal regions can experience more than 180 days of thick fog a year.〔〔 While this has proved a major hazard to ships—more than a thousand wrecks litter the Skeleton Coast—it is a vital source of moisture for desert life. The Namib is almost completely uninhabited by humans except for several small settlements and indigenous pastoral groups, including the Ovahimba and Obatjimba Herero in the north, and the Topnaar Nama in the central region.〔 Owing to its antiquity, the Namib may be home to more endemic species than any other desert in the world. Most of the desert wildlife is arthropods and other small animals that live on little water, although larger animals inhabit the northern regions. Near the coast, the cold ocean water is rich in fishery resources and supports populations of brown fur seals and shorebirds, which serve as prey for the Skeleton Coast's lions.〔 Further inland, the Namib-Naukluft National Park, the largest game park in Africa, supports populations of African Bush Elephants, Mountain Zebras, and other large mammals. Although the outer Namib is largely barren of vegetation, lichens and succulents are found in coastal areas, while grasses, shrubs, and ephemeral plants thrive near the escarpment. A few types of trees are also able to survive the extremely arid climate.〔 ==Geography and geology== The Namib Desert is one of the 500 distinct physiographic provinces of the South African Platform physiographic division. It occupies an area of around 80,950 km² (31,200 square miles), stretching from the Usiab River (north) to the town of Lüderitz (south) and from the Atlantic Ocean (west) to the Namib Escarpment (east). It is about long from north to south and its east-west width varies from . To the north, the desert leads into the Kaokoveld; the dividing line between these two regions is roughly at the latitude of the city of Walvis Bay, and it consists in a narrow strip of land (about 50 km wide) that is the driest place in Southern Africa. To the south, the Namib borders on the South African Karoo semi-desert. Southern Namib (between Lüderitz and the Kuiseb River) comprises a vast dune sea with some of the tallest and most spectacular dunes of the world, ranging in color from pink to vivid orange. In the Sossusvlei area, several dunes exceed in height. The complexity and regularity of dune patterns in its dune sea have attracted the attention of geologists for decades, but it remains poorly understood. Moving north from Sossusvlei, the sand gradually gives way to a rocky desert that extends all the way from Sossusvlei to the Swakop river. This area is traversed by the Tropic of Capricorn and is mostly flat, although some scenic canyons and elevations are found in some areas, for example in the Moon Valley system. While most of the soil is rocky, sand dunes are still occasionally found in this region; for example, sand dunes occupy much of the coastline between Walvis Bay and Swakopmund. Two well known sand dunes are Dune 7 and Dune 45. Dune 7 is 10 kilometers outside the town of Walvis Bay and its the highest dune in the coastal dune belt of the Namib Desert. The dune is about 130meters high with a very steep slip face. The dune was frequently used by numbers of the South African defense force for training purposes.〔 Dune 45 is the most iconic and frequently photographed dune. It is located near the entrance to the popular southern Namib Desert attraction of Sossusvlei. 〔 The Namib desert is an important location for the mining of tungsten, salt and diamonds. Several rivers and streams run through the Namib, although all of the rivers south of the Cunene River and north of the Orange River are ephemeral and rarely or never reach the ocean.〔 These rivers arise in the interior mountains of Namibia and flow after summer rain storms.〔 ==Climate== The Namib's aridity is caused by the descent of dry air of the Hadley Cell, cooled by the cold Benguela current along the coast. It has less than of rain annually and is almost completely barren. Besides rain being scarce, it is also hardly predictable. The western Namib gets less rain (5 mm) than the eastern Namib (85 mm). This is due to several factors. Winds coming from the Indian Ocean lose part of their humidity when passing the Drakensberg mountains, and are essentially dry when they reach the Namib Escarpment at the eastern end of the desert. Winds coming from the Atlantic Ocean, on the other hand, are pressed down by hot air from the east; their humidity thus forms clouds and fog. Morning fogs coming from the ocean and pushing inwards into the desert are a regular phenomenon along the coast, and much of the life cycle of animals and plants in the Namib relies on these fogs as the main source of water. The dry climate of the Namib reflects the almost complete lack of bodies of water on the surface. Most rivers flow underground and/or are dry for most of the year, and even when they are not, they usually drain into endorheic basins, without reaching the sea. The Swakop and the Omaruru are the only rivers that occasionally drain into the ocean. All along the coast, but mostly in the northernmost part of it, interaction between the water-laden air coming from the sea via southerly winds, some of the strongest of any coastal desert, and the dry air of the desert causes immense fogs and strong currents. It causes sailors to lose their way; this is testified by the remnants of a number of shipwrecks that can be found along the Skeleton Coast, in northern Namib. Some of these wrecked ships can be found as much as inland, as the desert slowly moves westwards into the sea, reclaiming land over a period of many years. Benguela's El Niño (similar to the Pacific event in its environmental change in the seas) spreads from the Kunene estuary southward to, on occasion, south of Luderitz. Warm waters with depth and associated water flows from the northwest were first fully catalogued by Sea Fisheries researchers, Cape Town (L V Shannon ''et al.''). The research noted the positive effect of Benguela's El Niño on the rainfall of the interior. Rainfall records also show positive values variously across the Namib, Desert Research Station, Gobabeb for instance. This event recurs approximately mid-decade (1974, 1986, 1994, 1995 and 2006 are recent examples) 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Namib Desert」の詳細全文を読む スポンサード リンク
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