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The Taklamakan Desert, China – September 13th, 2008

September 13th, 2008 Category: Image of the day

September 11th, 2008 - The Taklamakan Desert, ChinaThe Taklamakan Desert

September 11th, 2008 - The Taklamakan Desert, China

The Taklamakan Desert, also known as Taklimakan, is a desert in Central Asia, in the Xinjiang Uyghur Autonomous Region of the People’s Republic of China. It is bounded by Kunlun Mountains to the south, and Pamir Mountains and Tian Shan (ancient Mount Imeon) to the west and north.

Taklamakan is known as one of the largest sandy deserts in the world, ranking 15th in size in a ranking of the world’s largest non-polar deserts. It covers an area of 270,000 km² of the Tarim Basin, 1,000 km long and 400 km wide. It is crossed at its northern and at its southern edge by two branches of the Silk Road as travellers sought to avoid the arid wasteland. In recent years, the People’s Republic of China has constructed a cross-desert highway that links the cities of Hotan (on the southern edge) and Luntai (on the northern edge).

Taklamakan is the paradigm of a cold desert. Given its relative proximity with the cold to frigid air masses in Siberia, extreme lows are recorded in wintertime, sometimes well below −20 °C (−4 °F) . During the 2008 Chinese winter storms episode the Taklamakan was reported to be for the first time covered in its entirety of a thin layer of snow reaching 4 centimetres (1.6 in) in some observatories.

Its extreme inland position, virtually in the very heartland of Asia and thousands of kilometres from any open body of water, accounts for the cold character of its nights even during summertime.

There is no water on the desert and it is hazardous to cross. Takla Makan means “go in and you’ll never come out”. Merchant caravans on the Silk Road would stop for relief at the thriving oasis towns.

The key oasis towns, watered by rainfall from the mountains, were Kashgar, Marin, Niya, Yarkand, and Khotan (Hetian) to the south, Kuqa and Turfan in the north, and Loulan and Dunhuang in the east. Now many, such as Marin and Gaochang are ruined cities in sparsely inhabited areas in the Xinjiang Autonomous Region of the Peoples Republic of China.

The archeological treasures found in its sand buried ruins point to Tocharian, early Hellenistic, Indian and Buddhistic influences. Mummies, some 4000 years old, have been found in the region. They show the wide range of peoples who have passed through. Some of the mummies appear European. Later, the Taklamakan was inhabited by Turkic peoples. Starting with the Tang Dynasty, the Chinese periodically extended their control to the oasis cities of the Taklamakan in order to control the important silk route trade across Central Asia. Periods of Chinese rule were interspersed with rule by Turkic and Mongol and Tibetan peoples. The present population consists largely of Turkic, Uyghur people.

source Wikipedia

Ubari and Murzuq sand seas, Libya – September 9th, 2008

September 9th, 2008 Category: Image of the day

September 8th, 2008 - Ubari and Murzuq sand seas, LibyaLibya

September 8th, 2008 - Ubari and Murzuq sand seas, Libya

This Envisat image shows two huge sand dune seas in the Fezzan region of southwestern Libya, close to the border with Algeria.

Most of the face of the Sahara desert stretching across Northern Africa is bare stone and pebbles rather than sand dunes, but there are exceptions – sprawling seas of multi-storey sand dunes known as ‘ergs’.

The Erg Ubari (also called Awbari) is the reddish sand sea towards the top of the image. A dark outcrop of Nubian sandstone separates the Erg Ubari sand from the Erg Murzuq (also called Murzuk) further south.

A persistent high-pressure zone centred over Libya keeps the heart of the Sahara completely arid for years at a time, but research has discovered evidence of ‘paleolakes’ in this region associated with a wetter and more fertile past.

Sahara, Libya

Dunes detail, Sahara - Libya

Libya today has no permanent rivers or water bodies, but has various vast fossil aquifers. These natural underground basins hold enormous amounts of fresh water.

Two decades ago an ambitious project called Great Man-Made River was begun, aimed at drawing water from the aquifers beneath the Fezzan region shown in the image, via a network of underground pipes for irrigation in the coastal belt. Upon completion the huge network of pipelines will extend to about 3,380 km.

source ESA

The Namib Desert – September 7th, 2008

September 7th, 2008 Category: Image of the day

September 6th, 2008 - The Nabim DesertNamibia

September 6th, 2008 - The Nabim Desert

The Namib Desert is a desert in Namibia and southwest Angola which forms part of the Namib-Naukluft National Park. The desert is Africa’s second largest. The name “Namib” is of Nama origin.

The desert occupies an area of around 80900 km² (31200 square miles), stretching about 1600 km (1000 miles) along the Atlantic Ocean coast of Namibia. Its east-west width varies from 50 to 160 km (30-100 miles). The Namib Desert also reaches into southwest Angola. It is one of the 500 distinct physiographic provinces of the South African Platform physiographic division.

The area is considered to be one of the oldest deserts in the world, having endured arid or semi-arid conditions for at least 55 million years after the Atacama Desert. Its 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 10 mm (0.4 inches) of rain annually and is almost completely barren.

A number of unusual species of plants and animals are found only in this desert. One of these is Welwitschia mirabilis, one of the most unusual species. Welwitschia is a shrub-like plant, but grows just two long strap-shaped leaves continuously throughout its lifetime.

These leaves may be several meters long, gnarled and twisted from the desert winds. The taproot of the plant develops into a flat, concave disc in age. Welwitschia is notable for its survival in the extremely arid conditions in the Namib, sometimes deriving moisture from the coastal sea fogs.

Sand dunes - Sossusvlei, Namibia - O.Peyre

Sand dunes - Namibia

Although the desert is largely unpopulated and inaccessible, there are year-round settlements at Sesriem, close to the famous Sossusvlei and a huge group of sand dunes, which at more than 300 meters high are among the tallest sand dunes in the world.

The complexity and regularity of dune patterns in its dune sea have attracted the attention of geologists for decades. They still remain poorly understood.

The 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, causing sailors to lose their way. Along with the Skeleton Coast further north, it is notorious as the site of many shipwrecks. Some of these wrecked ships can be found as much as 50 metres inland, as the desert slowly moves westwards into the sea, reclaiming land over a period of many years.

The Namib desert is an important location for the mining of tungsten, salt and diamonds.

source Wikipedia

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