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| September 28, 2005 | Sahara desert |
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Sahara, with a size of 8.6 million km², is the world's largest desert, covering large parts of North Africa.
Its maximum length is 4,800 km, running from west to east, and up to 1,200 km from north to south. Sahara is covers Mauritania, Morocco, Algeria, Tunisia, Libya, Egypt, Sudan, Chad, Niger and Mali. Sahara is bordered in the north by the Atlas Mountains and the Mediterranean Sea and in the west by the Atlantic Ocean. In the south, the desert zone reaches 16º northern latitude; it is bordered by the Nile in the east, even if the desert continues to the east of the river until it reaches the Red Sea.
2.5 million people live in Sahara, most of these in Mauritania, Morocco and Algeria. Dominant groups of people are Sahrawis, Tuareg and Negroids. The largest city is Nouakchott, Mauritania's capital. Other important cities are Tamanrasset, Algeria and Ghat, Libya.
Sahara is very dry but there is an annual rainfall in most regions, although just a couple of millimetres.
1/4 of Sahara is mountainous, with the highest peak reaching 3415 metres above sea level (Emi Koussi, Chad). The lowest point lies in the Qattara Depression in Egypt. Some mountain peaks are covered with snow in the winter. The main mountain rages are Hoggar, Algeria; Aïr/Azbine, Niger; and Tibesti, Chad.
Sand sheets and dunes represent about 25% of the Sahara; the other parts are mountains, stoney steppes and oases. Pyramidal dunes can be as high as 150 metres, while mountainous sand ridges as high as 350 metres.
There are several rivers running through the Sahara, of which the Nile and Niger are the most important permanent ones. Most other rivers are seasonal, or filled with water only for short periods, often with years in between.
Metallic minerals are very important to most Saharan countries. Algeria and Mauritania have several major deposits of iron ore, while smaller deposits are found in Egypt, Tunisia, Morocco, Western Sahara and Niger. Copper is found in Mauritania and manganese in Algeria. Small deposits of uranium are widely distributed in the Sahara, while Niger has the largest deposits. Phosphates are found in great quantities in Morocco and Western Sahara, and are already well-exploited. Algeria's phosphate production is smaller, but large enough for exports. Oil is mainly found in Algeria, and is of great importance to the economy of the entire country. While the mineral exploitation has led to economic growth in Sahara, this has rarely helped the indigenous population, but rather workers immigrating to the different fields.
Only 200,000 km² of Sahara are fertile oases, where dates, corn and fruits are grown. The few fertile regions today are fed by underground rivers and underground basins. Oases are in almost all cases depressions (areas under sea level) where water surfaces from underground.
The soil in Sahara is low in organic matter, and often biologically inactive. The soil in depressions, where there is a good chance of artesian wells, is often saline. Animal life is limited to gazelles, antelopes, jackals, foxes, badgers and hyena.
Other sorts of vegetation include scattered concentrations of grasses, shrubs and trees in the highlands, as well as in the oases and along river beds. Some plants are well adjusted to the climate, allowing them to germinate within 3 days of rain and sow their seeds within 2 weeks after that.
Animal life of Sahara include gerbil, jerboa, cape hare and desert hedgehog, barbary sheep, oryx, gazelle, deer, wild ass, baboon, hyena, jackal, sand fox, weasel and mongoose. The bird life counts more than 300 species.
Sahara has a subtropical climate in its northern parts, and a tropical one in the south. Winters in the north are cold to cool; in the south, mild. Summers are hot all over the desert. The highest temperature every recorded is 58ºC in Aziziyah, Libya. There is very little rain in the northern parts, virtually nothing in the east, although more in the south. Most rain falls throughout the summer, followed by some scarce winter rain.
MAXIMUM TEMPERATURES OF SAHARA (in Celsius)
J F M A M J J A S O N D Avg.
Tamanrasset, Alg. 21 24 27 30 33 36 35 34 33 30 26 21 29
Rainfall (in mm) 2 1 0 4 5 5 4 15 12 3 3 2 56
Sebha, Libya 17 22 26 32 36 40 39 37 35 33 27 16 30
Rainfall 0 0 0 0 4 0 0 0 0 0 4 0 8
Dakhla, Egypt 22 24 28 33 37 39 39 39 36 33 28 23 32
Rainfall 0 4 6 5 0 0 0 0 0 0 0 0 15
Agadez, Niger 29 33 38 41 44 43 41 38 40 39 35 32 38
Rainfall 0 0 0 0 0 0 0 0 0 0 0 0 0
Timbouctou, Mali 31 34 38 42 43 43 39 36 39 40 37 32 38
Rainfall 0 0 3 0 5 23 79 81 38 3 0 0 232
Atar, Mauritania 31 33 34 39 40 42 43 42 42 38 33 29 446
Rainfall 3 0 0 0 0 3 8 30 28 3 3 0 78
HISTORY
5 million years ago: Climatic changes turn the region of Sahara into a desert.
Around 5000 BCE: Domesticated livestock appears in Sahara, leading to nomadic pastoralism.
Around 4000 BCE: First traces of agriculture.
Around 0 CE: The climate of Sahara returns mainly to desert, rather similar to modern conditions.
3rd century: Camels are introduced in Sahara, taking the place of horses. This allows a great increase in trade, but also banditry.
7th century: Islam is introduced to Sahara, but the conversion process takes almost 4 centuries.
16th century: Climatic changes involve increased precipitation.
18th century: The level of precipitation declines gradually, leading to conditions similar to modern times.
1922: Storms and floods destroy Tamanrasset in Algeria.
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