The Libyan Desert, also known as Great Sand Sea or Western Desert, is an African desert that is located in the northern and eastern part of the Sahara Desert and occupies southwestern Egypt, eastern Libya, and northwestern Sudan. Covering an area of approximately 1,200,000 square kilometers (463,320 square miles), it extends approximately 1,100 km from east to west, and 1,000 km from north to south, in about the shape of a rectangle.
This desert is primarily sand and boulder plain and is inhabited by the Senussis, a conservative Islamic group. Rock plateaus and sandy plains extend from eastern Libya into northwestern Sudan. A group of oases enables the cultivation of cereal grains, olives, grapes, and dates. The surface is broken by numerous gorges that were likely caused by erosion linked to cycles of freezing and thawing.
Ridges and deep depressions (basins) exist in several parts of the desert, and no rivers or streams drain into or out of the area. The desert's Jilf al Kabir Plateau has an altitude of about 2,000 meters, an exception to the uninterrupted territory of basement rocks covered by layers of horizontally bedded sediments, forming a massive plain or low plateau.
Overview
There are eight important depressions in the Libyan Desert, and all are considered oases except the smallest, Qattara, because its waters are salty. Limited agricultural production, the presence of some natural resources, and permanent settlements are found in the other seven depressions, all of which have fresh water provided by the Nile River or by local groundwater. The Siwa Oasis, close to the Libyan border and west of Qattara, is isolated from the rest of Egypt but has sustained life since ancient times.
The other major oases include Dakhla and Kharga in Egypt, and Jaghbub in Libya, which, along with Siwa, form a topographic chain of basins extending from the Al Fayyum Oasis (sometimes called the Fayyum Depression) which lies sixty kilometers southwest of Cairo, south to the Bahariya, Farafra, and Dakhla oases before reaching the country's largest oasis, Kharga. A brackish lake, Lake Karun, at the northern reaches of Al Fayyum Oasis, drained into the Nile in ancient times. For centuries sweetwater artesian wells in the Fayyum Oasis have permitted extensive cultivation in an irrigated area that extends over 2,100 square kilometers.
Key geographic feaures
The Qattara Depression
The Qattara Depression, which contains the second lowest point in Africa, is approximately 15,000 km². (about the size of Connecticut and Rhode Island), and is largely below sea level (its lowest point is 133 meters below sea level). The sparsely inhabited Qattara Depression is covered by badlands, salt marshes, and salt lakes.
The Gilf Kebir
The Gilf Kebir plateau, which lies entirely in Egypt, rises about 300 meters (1,000 ft) above the general plain. It roughly equals Switzerland in size and is similar in structure to the other sandstone plateaus of the central Sahara. Its southeastern part is well defined on all sides, with sheer cliffs and deep, narrow wadis. The northeast part, separated from the other half by a broad valley called the "Gap" is more broken and supports three large wadis with vegetation.
The Sand Seas
The three sand seas, which contain dunes up to 110 meters in height and which cover approximately one quarter of the region include:
Egyptian Sand Sea
Kalansho Sand Sea
Ribiana Sand Sea
Flora and fauna
Camels were introduced to Northern Africa in the first century C.E. Considering the hyper-arid conditions, the fauna of the central Sahara is richer than is generally believed. Within this ecoregion there are seventy species of mammals, twenty of which are large mammals. There are also ninety species of resident birds (including vultures and hawks) and around one hundred species of reptiles. Arthropods are also numerous, especially ants.
The animals include fennec foxes, rodents, snakes, lizards, insects, and scorpions. The fennec fox has large ears to dissipate heat and hairy soles to protect its feet while crossing the desert in search of lizards and locusts. These kinds of adaptations have allowed them to survive in such an inhospitable environment. Many of the animals get their water only through metabolic processes. Animals may lose 30-60 percent of their body mass and still recover.
The central Sahara is estimated to include only five hundred species of plants, which is extremely low considering the huge extent of the area. Plants such as acacia trees, palms, succulents, spiny shrubs, and grasses have adapted to the arid conditions, either by reducing water loss or storing water. Plant leaves may dry out totally and then recover.
History
According to archeologists, the Sahara was much more densely populated more than twenty thousand years ago, when the desert's climate was not as arid as it is today. Fossils, rock art, stone artifacts, bone harpoons, shells, and many other items have been found in areas that today are considered too hot and dry to inhabit. The artifacts were located near remains of giraffe, elephant, buffalo, antelopes, rhinoceros, and warthog, as well as those of fish, crocodiles, hippopotamuses, and other aquatic animals, indicating the presence of lakes and swamps in the Sahara.
Between twenty thousand and twelve thousand years ago, severe conditions returned and the Sahara was largely depopulated, except in highland retreats where there were springs and surface pools fed by aquifers. By ten thousand years ago, gatherers and fishers had reoccupied the replenished lakes, streams, and swamps. There are some traces of possible agriculture from eight thousand years ago, and more verifiable evidence of cattle-keeping in the mountains by seven thousand years ago, perhaps in response to more arid conditions. That population would leave again three to four thousand years ago as conditions deteriorated. The Sahara became a largely impenetrable barrier to humans, with only scattered settlements around the oases but little trade. The one major exception was the Nile Valley
Immediately after the last ice age, the Sahara was a much wetter place than it is today. The modern Sahara, though, is not as lush in vegetation, except at a few oases. The region has been this way since about 3,000 B.C.E.
Modern exploration
Since ancient times, the Sahara was traversed by Muslim traders and natives. The first modern explorer in the region was the German Friedrich Gerhard Rohlfs. In his daring expeditions in 1865 he received much resistance from the natives of the Saharan oases he visited and was nearly killed in the attempt. All his instruments and scientific records were destroyed. Despite the resistance to all European outsiders at the time, especially by Senussis, Rohlfs managed to come back with several important findings and a first map of the Libyan Desert, though it contained a number of inaccuracies.
In 1924, the Egyptian diplomat Ahmed Hassanein undertook a 2,200-mile (3,500 km) expedition on foot across the Libyan Desert in which he made the first accurate maps and discovered the legendary oases of Jebel Uweinat and Jebel Arkenu. He wrote important accounts on the Senussis, explaining their lifestyle and ethics in his book The Lost Oases. The climax of his expedition was the discovery of unknown water sources that opened new Sahara routes from Kufra to Sudan. He is also remembered for the significant rock art he discovered and photographed depicting animals, including lions, giraffes, ostriches, gazelles and possibly also cattle, evidence of a flourishing human existence ten thousand years ago before desertification drove these mysterious people to the valley of the Nile.
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