Hundreds of millions of years ago the area where the Sahara is now was covered by great seas. With time, the seas slowly drifted away, leaving behind a massive expanse of searing desert, much bigger than the one we have today. Around 800,000 years ago, the Sahara was hot, damp and covered with swamps, lakes, rivers and vegetation everywhere. This period of heavy rain lasted for hundreds of thousands of years. Ever since, the Sahara comes and goes just as the ice ages do elsewhere. One of these most recent cycles, between 12,000 and 10,000 years ago, brought heavy rainfalls to the area, and gradually transformed the Sahara into wet and lush-green land, covered with rivers and lakes, hippopotami, rhinoceroses, crocodiles and elephants. Around the same time, about 12,000 years ago, the same heavy rainfall flooded Lake Victoria and created the river Nile, thereby creating a new home for several Saharan refugees, including the ancient Egyptians, after the Sahara turned dry again between 7000 and 5000 years ago. However, according to an article published in the Independent Newspaper (September 8, 1999), titled: "Tilt of Earth's axis turned Sahara into a desert", scientists have found that the Sahara was abruptly transformed from fertile land into a desert after the Earth underwent one of its periodic changes in orientation between 9000 and 6000 years ago; during which its tilt lessened from 24.14 degrees off vertical to its present 23.45 degrees, and its closest position to the sun gradually shifted from July to January. The Sahara today is the largest desert in the world, estimated to be between seven and nine million square kilometres (7-9m km2) - that is about one third of Africa. Winters in the subtropical north can be very cold where temperatures can fall below freezing point, as opposed to the mild tropical south, where rain falls more during the summer than it does in the north. Similarly, temperatures are high during the day and low at night.The highest temperature in the world was recorded in Libya on the 13th of September 1922, in el-Azizia, close to Tripoli: a staggering 136.4 degree Fahrenheit (or 58 degrees Celsius). Although in the summer temperatures reach 50 degrees Celsius in the shade and in the winter can reach -9 (minus nine), the average year round temperature is about 30 degrees Celsius.
Citrullus colocynthis. Berber names: Alkhad (Tuareg); Tadjalt. Ground-creeping desert plant, with inedible gourds, the size of small melons. The milky sap of these gourds is used as a remedy for scorpion stings by the local Tuareg people. The gourd is also a purgative - that is cleanses and purifies the body. For further details, see "Traditional medicine in Central Sahara: Pharmacopoeia of Tassili N?ajjer", by Hammiche, H. & K. Maiza; Journal of Etnopharmacology, Volume 105 (2006) pp. 358-367
In prehistoric times the Sahara was significantly wetter, but climatic desiccation over the past few thousand years has destroyed much of its wildlife. The flora of the Sahara is estimated to include about 1,200 species, consisting mainly of xerophytes and ephemeral plants, with halophytes in moister areas, and Acacia, Tamarisk and Calotropis procera along the wadis. However, according to another scientific study, the Sahara's flora still includes about 3000 species. The fauna of the Sahara includes about 70 species of mammals, 300 species of birds, including 90 species of resident birds, and around 100 species of reptiles. Owing to extreme heat, most small desert creatures are nocturnal. The populations of these species were greatly reduced by over-hunting and many are now endangered species, like the ostrich, addax, some species of gazelles and the cheetah. Most of the African large mammals that were reported to have been present in the desert until the second half of the 19th century have now become extinct. Some of these animals can be seen in Fezzan Park, and also in Tripoli's zoo. The Sahara is also rich in oil and metallic mineral deposits, the most common of which is iron ore (found in large quantities in Algeria and Mauritania), followed by copper, manganese, phosphates, and uranium (with large deposits in Niger, which may explain the recent unrest that hit the country in the last decade or two).
Desert Roses:
Desert Roses from the Sahara around the Ghadames Area, Libya. Desert roses grow in size just like plants and animals do. The leaf-like structure of its crystals makes the stone look like a rose flower and hence its name. This leafy structure is slowly built using the mineral gypsum which grows in the tiny gaps between the specks of sand. A handful of sand would appear compact to the naked eye, but under the microscope one can easily see more cavities than sand. As it grows in these cavities the gypsum seals the surrounding sand particles in leaf-like flakes. These flakes then grow with time just like plant leaves do, and develop complex forms (see above).
Life In The DesertMost of the Sahara's oases are situated in depressions and sustained by underground basins and rivers. But how do plants survive in the desert?For plants to survive in the desert, they must invent ingenious ways to deal with lack of water. Some species germinate within 72 hours of rainfall and sow their seeds 2 weeks later. Shrubs and trees have extensive root systems which can penetrate as far as 50 metres into the ground; tamarisk and acacia have short, fat trunks that act as reservoirs for excess water. The seeds of ephemerals germinate only after heavy rain, and then very quickly consume their entire life-cycle; producing brightly coloured flowers to attract insects. Grasses, however, develop large and complex root systems for collecting water over a wide area, enabling them to survive when the over ground parts are scorched to death. Geophytes survive by remaining underground as bulbs, and like ephemerals, they quickly grow and develop when rain comes. Saharan succulents, like euphorbia, suck the extra water to store for later. Some insects collect moisture from the air and then direct it as droplets of water into their mouths. While the desert-ships (the camels) vary their bodies' temperature according to conditions: low when it is cool and high when hot; when they are thirsty transpiration drops to zero. While humans resort to nomadic way of life in order to survive in the Sahara, travelling from one location to another in search of water and vegetation. The only permanently inhabited zones in the Sahara are the oases and areas along the few fertile valleys, such as Wadi Alhayat (the Valley of Life) in Fezzan. The palm trees in these regions, which are normally arranged in narrow lines with an east-west orientation (in line with the apparent sun's course across the sky), occur where water is relatively close to the surface, and thus allowing the digging of shallow wells to support settled life. Rain in the Sahara falls at rare intervals, mostly between the months of January and April, with a variation from 0.5 inch to 4 inches over a 5 year period.
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Some of the main animals and insects that can be found in the Sahara include
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Fish (in pools):
Birds (Migratory & Breeding):
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Some of the main plants that can be found in the Sahara desert
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Palm Dates, Sahara, Libya.
Fossilised Wildlife In The SaharaThe Sahara desert is very rich in fossils of extinct wildlife. Some of the fossils found include those of dinosaurs, petrified tree trunks, lizards and marine shells. The following photos show some of the fossils currently on display in Ghadames Museum.
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Sunday, 27 September 2009
Wildlife in The Sahara
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