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Posts tagged Dunes

Namib Sand Sea Along Namibia’s Central Coast

24.6S 15.4E

March 24th, 2011 Category: Deserts

Namibia - March 22nd, 2011

The Namib Desert is a broad expanse of hyper-arid gravel plains and dunes that stretches along Namibia’s entire coastline. This image focuses on the sandy half of the desert, to the south, known as the Namib Sand Sea.

The sands that make up the sand sea result from processes of erosion that take place in the Orange River valley and areas further to the south. As sand-laden waters drop their suspended loads into the Atlantic, onshore currents deposit them along the shore. The prevailing south west winds then pick up and redeposit the sand in the form of massive dunes in the widespread sand sea, forming the largest sand dunes in the world.

Sahara Dunes by Tassili n’Ajjer Mountains in Illizi, Algeria – July 5th, 2010

25.5N 9.0E

July 5th, 2010 Category: Image of the day, Mountains

Algeria - April 28th, 2010

Algeria - April 28th, 2010

Part of the Illizi province (wilaya), in the south-eastern corner of Algeria, is visible here. The upper half of the image shows the orangey sand dunes of the Sahara Desert, while the lower half shows the brown slopes of the Tassili n’Ajjer mountain range.

The name of the range means “Plateau of the Rivers” in Tamazight. As the name suggests, the topography of the range is deeply indented, eroded by rivers in the past. Today the range is drier, although due to the altitude and the water-holding properties of the sandstone, the vegetation is somewhat richer than the surrounding desert.

Taklamakan Desert in China’s Tarim Basin

39.4N 81.7E

June 5th, 2010 Category: Mountains

China - June 2nd, 2010

China - June 2nd, 2010

The Taklamakan Desert forms the greater part of the Tarim Basin, west-central China. One of the world’s largest sandy wastes, it is about 600 mi (960 km) across, with an area of 123,550 sq mi (320,000 sq km).

It is flanked by high mountain ranges, including the Kunlun Mountains, whose rivers penetrate the desert 60–120 mi (100–200 km) before drying up in its sands. Its wind-blown sand cover is as much as 1,000 ft (300 m) thick and has formed such features as high pyramidal dunes.

Lake Turkana, an East African Rift Feature in Kenya and Ethiopia

3.6N 36.0E

March 25th, 2010 Category: Lakes, Volcanoes

Kenya and Ethiopia - March 5th, 2010

Kenya and Ethiopia - March 5th, 2010

Lake Turkana, formerly known as Lake Rudolf, is a lake in the Great Rift Valley in Kenya, with its far northern end crossing into Ethiopia. It is the largest permanent desert lake in the world and also the world’s largest alkaline lake.

The rocks of the surrounding area are predominantly volcanic. Central Island (visible in the center of the lake upon opening the full image) is an active volcano, emitting vapors. Outcrops and rocky shores are found on the East and South shores of the lake, while dunes, spits and flats are on the West and North, at a lower elevation.

The lake is an East African Rift feature. A rift is a weak place in the Earth’s crust due to the separation of two tectonic plates, often accompanied by a graben, or trough, in which lake water can collect. Currently the graben is 320 km wide in the north of the lake, 170 km in the south.

The visible tectonic features of the region result from extensive extrusions of basalt over the Turkana-Omo basin in the window 4.18-3.99 mya. These are called the Gombe Group Basalts. They are subdivided into the Mursi Basalts and the Gombi Basalts.

The two latter basalts are identified as the outcrops that are the rocky mountains and badlands around the lake.  Short-term fluctuations in lake level combined with periodic volcanic ash spewings over the region have resulted in a fortuitous layering of the ground cover over the basal rocks.

Tassili n’Ajjer Mountains in the Sahara Desert, Algeria

25.5N 9.0E

January 6th, 2010 Category: Snapshots

Algeria - December 16th, 2009

Algeria - December 16th, 2009

Tassili n’Ajjer is a mountain range in the Sahara desert in southeast Algeria, North Africa. It extends about 500 km, and the highest point is Adrar Afao, at 2158 m. The nearest town is Djanet, about 10 km southwest of the range. Much of the range is protected in a National park, Biosphere Reserve and World Heritage Site, named the Tassili n’Ajjer National Park.

The range is composed largely of sandstone. Erosion in the area has resulted in nearly 300 natural rock arches being formed, along with many other spectacular landforms. Because of the altitude and the water-holding properties of the sandstone, the vegetation is somewhat richer than the surrounding desert; it includes a very scattered woodland of the endangered endemic species Saharan Cypress and Saharan Myrtle in the higher eastern half of the range.