Sahara Desert

For other uses, see Sahara Desert (disambiguation).

File:Sahara satellite.jpg

Satellite image

The Sahara is the world's largest hot desert, and second largest desert after Antarctica at over 9,000,000 km² (3,500,000 mi²), almost as large as the United States. The Sahara is located in Northern Africa and is 2.5 million years old.

The name Sahara is an English pronunciation of the Arabic word for desert, ().

Overview

The top image shows the Safsaf Oasis on the surface of the Sahara. The bottom (using radar) is the rock layer underneath, revealing black channels cut by the meandering of an ancient river that once fed the oasis.

The boundaries of the Sahara are the Atlantic Ocean on the west, the Atlas Mountains and the Mediterranean Sea on the north, the Red Sea and Egypt on the east, and the Sudan and the valley of the Niger River on the south. The Sahara is divided into western Sahara, the central Ahaggar Mountains, the Tibesti Mountains, the Aïr Mountains (a region of desert mountains and high plateaus), Tenere desert and the Libyan desert (the most arid region). The highest peak in the Sahara is Emi Koussi (3415 m) in the Tibesti Mountains in northern Chad.

The Sahara divides the continent of Africa into North and Sub-Saharan Africa. The southern border of the Sahara is marked by a band of semiarid savanna called the Sahel; south of the Sahel lies the lusher Sudan and the Congo River Basin. Most of the Sahara consists of rocky hamada; ergs (large sand dunes) form only a minor part.

Humans have lived on the edge of the desert for almost 500,000 years. Immediately after the last ice age, the Sahara was a much wetter place than it is today. Over 30,000 petroglyphs of river animals such as crocodiles (which still exist in parts of the desert) survive, with half found in the Tassili n'Ajjer in southeast Algeria. Fossils of dinosaurs, including Afrovenator, Jobaria and Ouranosaurus, have also been found here. The modern Sahara, though, is not as lush in vegetation, except in the Nile Valley, at a few oases, and in the northern highlands, where Mediterranean plants such as the olive tree are found to grow. The region has been this way since about 3000 B.C.E.

Some 2.5 million people live in the Sahara, most of these in Egypt, Mauritania, Morocco and Algeria. Dominant ethnicities in the Sahara are various Berber groups including Tuareg tribes, various Arabised Berber groups such as the Hassaniya-speaking Maure/Moors (also known as Sahrawis), and various "black African" ethnicities including Tubu, Nubians, Zaghawa, Kanuri, Peul (Fulani), Hausa and Songhai. The largest city in the Sahara is the Egyptian capital Cairo, in the Nile Valley. Other important cities are Nouakchott, the capital of Mauritania; Tamanrasset, Ouargla, Bechar, Hassi Messaoud, Ghardaia, El Oued, Algeria; Timbuktu, Mali; Agadez, Niger; Ghat, Libya; and Faya, Chad.

Physical Features

The highest part of the desert is at the summit of Mount Koussi in the Tibesti Mountains, which is 11,204 feet (3,415 m) high. The lowest point of the Sahara is 436 feet (133 m) below sea level in the Qattara Depression in Egypt.

Climate history

The climate of the Sahara has undergone enormous variation between wet and dry over the last few hundred thousand years. During the last ice age, the Sahara was bigger than it is today, extending south beyond its current boundaries. The end of the ice age brought wetter times to the Sahara, from about 8000 B.C.E. to 6000 B.C.E., perhaps due to low pressure areas over the collapsing ice sheets to the north.

Once the ice sheets were gone, the northern part of the Sahara dried out. However, not long after the end of the ice sheets, the monsoon which currently brings rain to the Sahel came further north and counteracted the drying trend in the southern Sahara. The monsoon in Africa (and elsewhere) is due to heating during the summer. Air over land becomes warmer and rises, pulling in cool wet air from the ocean. This causes rain. Paradoxically, the Sahara was wetter when it received more insolation in the summer. In turn, changes in solar insolation are caused by changes in the Earth's orbital parameters.^{[citation needed]}

By around 2500 B.C.E., the monsoon retreated south to approximately where it is today, leading to the desertification of the Sahara. The Sahara is currently as dry as it was about 13,000 years ago. These conditions are responsible for what has been called the Sahara Pump Theory.

Temperatures

The Sahara desert has one of the harshest climates in the world. It has many strong winds that blow from the north-east. Sometimes on the border zones of the north and south, the desert will receive about 25 cm (10 in.) of rain a year. The rainfall is usually torrential when it occurs after long dry periods, which can last for years. Daytime temperatures can be 58°c (136°F), but freezing temperatures aren’t uncommon at night. Its temperature can become -6°c (22°F).^{[citation needed]}

History

The sun shines over Saharan dunes.

Cattle Period

By 6000 B.C.E. predynastic Egyptians in the southwestern corner of Egypt were herding cattle and constructing large buildings. Subsistence in organized and permanent settlements in predynastic Egypt by the middle of the 6th millennium B.C.E. centered predominantly on cereal and animal agriculture: cattle, goats, pigs and sheep. Metal objects replaced prior ones of stone. Tanning animal skins, pottery and weaving are commonplace in this era also. There are indications of seasonal or only temporary occupation of the Al Fayyum in the 6th millennium B.C.E., with food activities centering on fishing, hunting and food-gathering. Stone arrowheads, knives and scrapers are common. Burial items include pottery, jewelry, farming and hunting equipment, and assorted foods including dried meat and fruit. The dead are buried facing due west.

Berber Period

The Phoenicians created a confederation of kingdoms across the entire Sahara to Egypt, generally settling on the coasts but sometimes in the desert also.

By 2500 B.C.E. the Sahara was as dry as it is today and it became a largely impenetrable barrier to humans, with only scattered settlements around the oases, but little trade or commerce through the desert. The one major exception was the Nile Valley. The Nile, however, was impassable at several cataracts making trade and contact difficult.

Sometime between 633 and 530 B.C.E. Hanno the Navigator either established or reinforced Phoenician colonies in the Western Sahara, but all ancient remains have vanished with virtually no trace. See History of Western Sahara.

Greeks

By 500 B.C.E. a new influence arrived in the form of the Greeks and Phoenicians. Greek traders spread along the eastern coast of the desert, establishing trading colonies along the Red Sea coast. The Carthaginians explored the Atlantic coast of the desert. The turbulence of the waters and the lack of markets never led to an extensive presence further south than modern Morocco. Centralized states thus surrounded the desert on the north and east; it remained outside of the control of these states. Raids from the nomadic Berber people of the desert were a constant concern of those living on the edge of the desert.

Urban civilization

An urban civilization, the Garamantes, arose around this time in the heart of the Sahara, in a valley that is now called the Wadi al-Ajal in Fazzan, Libya. The Garamantes achieved this development by digging tunnels far into the mountains flanking the valley to tap fossil water and bring it to their fields. The Garamantes grew populous and strong, conquering their neighbors and capturing many slaves (which were put to work extending the tunnels). The ancient Greeks and the Romans knew of the Garamantes and regarded them as uncivilized nomads. However, they traded with the Garamantes, and a Roman bath has been found in the Garamantes capital of Garama. Archaeologists have found eight major towns and many other important settlements in the Garamantes territory. The Gartamantes civilization eventually collapsed after they had depleted available water in the aquifers, and could no longer sustain the effort to extend the tunnels still further into the mountains.

The Arabs

After the Arab invasion of the Sahara, trade across the desert intensified. The kingdoms of the Sahel, especially the Ghana Empire and the later Mali Empire, grew rich and powerful exporting gold and salt to North Africa. The emirates along the Mediterranean sent south manufactured goods and horses. From the Sahara itself salt was exported. This process turned the scattered oasis communities into trading centres, and brought them under the control of the empires on the edge of the desert.

This trade persisted for several centuries until the development in Europe of the caravel allowed ships, first from Portugal but soon from all Western Europe, to sail around the desert and gather the resources from the source in Guinea. The Sahara was rapidly remarginalized.

The colonial powers also largely ignored the region, but the modern era has seen a number of mines and communities develop to exploit the desert's natural resources. These include large deposits of oil and natural gas in Algeria and Libya and large deposits of phosphates in Morocco and Western Sahara.

Contemporary people of the region

Throughout the Sahara, Berbers, Arabs, and sub-Saharan Africans are significantly represented genetically.

See also

• Arabian-Nubian Shield
• Desertification
• Nile
• Red Sea
• Richat Structure
• Sahara Desert (ecoregion)
• Trans-Saharan trade
• Western Sahara
• Zaara

References

ISBN links support NWE through referral fees

• Pigs in Ancient Egypt by Marie Parsons www.touregypt.net
• Michael Brett and Elizabeth Frentess. The Berbers. Blackwell Publishers. 1996.
• Charles-Andre Julien. History of North Africa: From the Arab Conquest to 1830. Praeger, 1970.
• Abdallah Laroui. The History of the Maghrib: An Interpretive Essay. Princeton, 1977.
• Hugh Kennedy. Muslim Spain and Portugal: A Political History of al-Andalus. Longman, 1996.
• Fezzan Project - Palaeoclimate and environment - retrieved March 15 2006

External links

Wikimedia Commons has media related to:

Sahara

• Trans-Sahara routes
• Sahara pictures from Algerian UN Permanent Mission website
• Flora and Fauna of the Sahara

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