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The Sahara (, ; ar, الصحراء الكبرى, ', 'the Greatest Desert') is a desert on the
African continent Africa is the world's second-largest and second-most populous continent A continent is any of several large landmasses. Generally identified by convention (norm), convention rather than any strict criteria, up to seven geographical reg ...

African continent
. With an area of , it is the largest hot
desert A desert is a barren area of landscape where little precipitation occurs and, consequently, living conditions are hostile for plant and animal life. The lack of vegetation exposes the unprotected surface of the ground to the processes of ...

desert
in the world and the third largest desert overall, smaller only than the deserts of
Antarctica Antarctica ( or ) is Earth's southernmost continent. It contains the geographic South Pole and is situated in the Antarctic region of the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Oc ...

Antarctica
and the northern
Arctic The Arctic ( or ) is a polar regions of Earth, polar region located at the northernmost part of Earth. The Arctic consists of the Arctic Ocean, adjacent seas, and parts of Alaska (United States), Canada, Finland, Greenland (Danish Realm, ...

Arctic
. The name "Sahara" is derived from the Arabic word for "desert" in the feminine irregular form, the singular ' ( ), plural ' ( ), ''ṣaḥār'' (صَحَار), ''ṣaḥrāwāt'' (صَحْارَاوَات), ''ṣaḥāriy'' (صَحَارِي). The desert comprises much of
North Africa North Africa or Northern Africa is a region encompassing the northern portion of the African continent. There is no singularly accepted scope for the region, and it is sometimes defined as stretching from the Atlantic shores of Mauritania in th ...

North Africa
, excluding the fertile region on the
Mediterranean Sea The Mediterranean Sea is a connected to the , surrounded by the and almost completely enclosed by land: on the north by and and , on the south by , and on the east by the . The Sea has played a central role in the . Although the Mediterrane ...
coast, the
Atlas Mountains The Atlas Mountains ( ar, جِبَال ٱلْأَطْلَس, jibāl al-ʾaṭlas /ʒibaːl al atˤlas/, Tamazight The Berber languages, also known as the Amazigh languages (Berber name: , ; Neo-Tifinagh: ⵜⴰⵎⴰⵣⵉⵖⵜ, Tuareg Tifin ...

Atlas Mountains
of the
Maghreb The Maghreb (; ar, المغرب, al-Maghrib, lit=the west), also known as Northwest Africa, is the western part of North Africa and the Arab world. The region includes Algeria, Libya, Mauritania (also considered part of West Africa), Morocco and ...

Maghreb
, and the
Nile Valley The Nile, , Bohairic , lg, Kiira , Nobiin Nobiin, or Mahas, is a Northern Nubian languages, Nubian language of the Nilo-Saharan languages, Nilo-Saharan language family. "Nobiin" is the genitive case, genitive form of ''Nòòbíí'' ("Nubi ...

Nile Valley
in
Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses. Generally identi ...

Egypt
and
Sudan Sudan ( or ; ar, السودان, as-Sūdān), officially the Republic of the Sudan ( ar, جمهورية السودان, link=no, Jumhūriyyat as-Sūdān), is a country in Northeast Africa. It borders the countries of Central African Republ ...

Sudan
. It stretches from the
Red Sea The Red Sea ( ar, البحر الأحمر, translit=al-Baḥr al-ʾAḥmar; or ; Coptic Coptic may refer to: Afro-Asia * Copts, an ethnoreligious group mainly in the area of modern Egypt but also in Sudan and Libya * Coptic language, a North ...

Red Sea
in the east and the Mediterranean in the north to the
Atlantic Ocean
Atlantic Ocean
in the west, where the landscape gradually changes from desert to coastal plains. To the south, it is bounded by the
Sahel The Sahel (; ar, ساحل ' , "coast, shore") is the ecoclimatic and of in between the to the north and the to the south. Having a , it stretches across the south-central latitudes of between the Atlantic Ocean and the . The Sahel part o ...

Sahel
, a belt of semi-arid tropical savanna around the
Niger River The Niger River (; , ) is the main river of West Africa, extending about . Its drainage basin is in area. Its source is in the Guinea Highlands in southeastern Guinea near the Sierra Leone border. It runs in a crescent through Mali, Niger, ...

Niger River
valley and the
Sudan Region Sudan is the geographic region to the south of the Sahara The Sahara (, ; ar, الصحراء الكبرى, ', 'the Greatest Desert') is a desert on the African continent. With an area of , it is the largest hot desert in the world and the ...
of
Sub-Saharan Africa Sub-Saharan Africa (commonly called Black Africa) is, geographically, the area of the continent of Africa that lies south of the Sahara. According to the United Nations, it consists of all list of sovereign states and dependent territories i ...

Sub-Saharan Africa
. The Sahara can be divided into several regions, including the western Sahara, the central
Ahaggar Mountains The Hoggar Mountains ( ar, جبال هقار, Berber: ''idurar n Ahaggar'') are a highland region in the central Sahara, southern Algeria, along the Tropic of Cancer. The mountains cover an area of approximately 550,000 square km (212,000 sq ...
, the
Tibesti Mountains The Tibesti Mountains are a mountain range A mountain range is a series of mountains ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alig ...

Tibesti Mountains
, the
Aïr Mountains The Aïr Mountains or Aïr Massif ( tmh, Ayăr; Hausa language, Hausa: Eastern ''Azbin'', Western ''Abzin'') is a triangular massif, located in northern Niger, within the Sahara Desert. Part of the West Saharan montane xeric wood ...
, the
Ténéré The Ténéré (Tuareg The Tuareg people (; also spelt Twareg or Touareg; endonym An endonym (from Greek: , 'inner' + , 'name'; also known as autonym) is a common, internal name A name is a term used for identification by an external obse ...
desert, and the
Libyan Desert The Libyan Desert (not to be confused with the Libyan Sahara) is a geographical region filling the north-eastern  Sahara Desert, from eastern Libya to the Western Desert of Egypt and far northwestern Sudan. On medieval maps, its use predates ...
. For several hundred thousand years, the Sahara has alternated between desert and savanna grassland in a 20,000 year cycle caused by the
precession Precession is a change in the orientation Orientation may refer to: Positioning in physical space * Map orientation, the relationship between directions on a map and compass directions * Orientation (housing), the position of a building with re ...

precession
of Earth's
axis Axis may refer to: Politics *Axis of evil The phrase "axis of evil" was first used by President of the United States, U.S. President George W. Bush in his State of the Union address on January 29, 2002, less than five months after the Septe ...

axis
as it rotates around the Sun, which changes the location of the
North African MonsoonNorth African climate cycles have a unique history that can be traced back millions of years. The cyclic climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variabi ...
.


Geography

The Sahara covers large parts of
Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital = Algiers , coordinates = , largest_city = capital , religion = , official_languages = , languages_type = Oth ...

Algeria
,
Chad Chad (; ar, تشاد , ; french: Tchad, ), officially known as the Republic of Chad ( ar, جمهورية تْشَاد, link=no '; ), is a landlocked A landlocked country is a country that does not have territory connected to an oce ...

Chad
,
Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses. Generally identi ...

Egypt
,
Libya Libya (; ar, ليبيا, Lībiyā), officially the State of Libya ( ar, دولة ليبيا, Dawlat Lībiyā), is a country in the Maghreb region in North Africa bordered by the Mediterranean Sea to the north, Egypt to Egypt–Libya border, th ...

Libya
,
Mali Mali (; ), officially the Republic of Mali (french: République du Mali; bm, ߡߊߟߌ ߞߊ ߝߊߛߏߖߊߡߊߣߊ, Mali ka Fasojamana, ff, 𞤈𞤫𞤲𞥆𞤣𞤢𞥄𞤲𞤣𞤭 𞤃𞤢𞥄𞤤𞤭, Renndaandi Maali, ar, جمهورية م ...

Mali
,
Mauritania Mauritania (; ar, موريتانيا, ', french: Mauritanie; Berber languages, Berber: ''Agawej'' or ''Cengit''; Pulaar language, Pulaar: ''Moritani''; Wolof language, Wolof: ''Gànnaar''; Soninke language, Soninke: ''Murutaane''), officially ...

Mauritania
,
Morocco ) , image_map = Morocco (orthographic projection, WS claimed).svg , map_caption = Location of Morocco in northwest Africa.Dark green: Undisputed territory of Morocco.Lighter green: Western Sahara, a United Nations lis ...

Morocco
,
Niger ) , official_languages = French , languages_type = National language A national language is a language A language is a structured system of communication used by humans, including speech (spoken language), gestures (Signed languag ...

Niger
,
Western Sahara Western Sahara ( '; ; ) is a disputed territory Controversy is a state of prolonged public dispute or debate, usually concerning a matter of conflicting opinion or point of view. The word was coined from the Latin ''controversia'', as a com ...

Western Sahara
,
Sudan Sudan ( or ; ar, السودان, as-Sūdān), officially the Republic of the Sudan ( ar, جمهورية السودان, link=no, Jumhūriyyat as-Sūdān), is a country in Northeast Africa. It borders the countries of Central African Republ ...

Sudan
and
Tunisia ) , image_map = Tunisia location (orthographic projection).svg , map_caption = Location of Tunisia in northern Africa Africa is the world's second-largest and second-most populous , after in both cases. At about 30.3 million km2 (11. ...

Tunisia
. It covers , amounting to 31% of Africa. If all areas with a mean annual precipitation of less than 250 mm were included, the Sahara would be . It is one of three distinct
physiographic provinces A physiographic province is a geographic region with a characteristic geomorphology incised into shale at the foot of the North Caineville Plateau, Utah, within the pass carved by the Fremont River and known as the Blue Gate. GK Gilbert studied ...
of the African massive physiographic division. The Sahara is mainly rocky
hamada A hamada (Arabic Arabic (, ' or , ' or ) is a Semitic language that first emerged in the 1st to 4th centuries CE.Semitic languages: an international handbook / edited by Stefan Weninger; in collaboration with Geoffrey Khan, Michael P. Str ...

hamada
(stone plateaus);
ergs The erg is a unit of energy equal to 10−7joule The joule ( ; symbol: J) is a derived unit of energy In physics, energy is the physical quantity, quantitative physical property, property that must be #Energy transfer, transferred to ...
(sand seas – large areas covered with sand
dune A dune is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the ...

dune
s) form only a minor part, but many of the
sand dune A dune is a landform A landform is a natural or artificial feature of the solid surface of the Earth or other planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the ...

sand dune
s are over high.
Wind Wind is the natural movement of air or other gases relative to a planet's surface. Wind occurs on a range of scales, from thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by th ...
or rare rainfall shape the desert features: sand dunes, dune fields, sand seas, stone plateaus, gravel plains (''reg''),
dry valleys
dry valleys
(''wadi''),
dry lake A dry lake bed, also known as a playa, is a basin or depression that formerly contained a standing surface water body, which disappeared when evaporation processes exceeded recharge. If the floor of a dry lake is covered by deposits of alkaline ...

dry lake
s (''oued''), and
salt flats Salt flats, Salt flat, Salt Flats, or Salt Flat may refer to: Geology *Salt pan (geology)Salt pans can refer to: *Salt pan (geology), a flat expanse of ground covered with salt and other minerals, usually found in deserts **Sabkha, a phonetic tran ...
(''shatt'' or ''chott''). Unusual landforms include the
Richat Structure The Richat Structure, also called ''Guelb er Richât'' (Arabic قلب الريشات ''Qalb ar-Rīšāt''), is a prominent circular geological feature in the 's , near , west–central , . In the local dialect, ''Richat'' means ''feather'' an ...
in Mauritania. Several deeply dissected mountains, many volcanic, rise from the desert, including the
Aïr Mountains The Aïr Mountains or Aïr Massif ( tmh, Ayăr; Hausa language, Hausa: Eastern ''Azbin'', Western ''Abzin'') is a triangular massif, located in northern Niger, within the Sahara Desert. Part of the West Saharan montane xeric wood ...
,
Ahaggar Mountains The Hoggar Mountains ( ar, جبال هقار, Berber: ''idurar n Ahaggar'') are a highland region in the central Sahara, southern Algeria, along the Tropic of Cancer. The mountains cover an area of approximately 550,000 square km (212,000 sq ...
,
Saharan Atlas The Saharan Atlas ( ar, الأطلس الصحراوي) is a range of the Atlas Mountain System. It is located mainly in Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital ...
,
Tibesti Mountains The Tibesti Mountains are a mountain range A mountain range is a series of mountains ranged in a line and connected by high ground. A mountain system or mountain belt is a group of mountain ranges with similarity in form, structure, and alig ...

Tibesti Mountains
,
Adrar des Iforas The Adrar des Ifoghas (also Adrar des Iforas; Tamasheq: ⴰⴷⵔⴰⵔ ⵏ ⵉⴼⵓⵖⴰⵙ in Tifinagh Tifinagh (; also written in the Berber Latin alphabet; Neo-Tifinaɣ: ; Tuareg Tifinagh: or ) is an abjad An abjad () is a type of ...
, and the
Red Sea Hills Itbāy ( ar, اطبيه) or ʿAtbāy is a region of southeastern Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a transcontinental country This is a list of countries located on more than one continent ...
. The highest peak in the Sahara is
Emi Koussi Emi Koussi (also known as Emi Koussou) is a high pyroclastic shield Image:Emi Koussi-Tibesti Mountains-Chad.jpg, 250px, Emi Koussi seen from International Space Station In volcanology, a pyroclastic shield or ignimbrite shield is an uncommon typ ...

Emi Koussi
, a
shield volcano A shield volcano is a type of volcano A volcano is a rupture in the crust of a planetary-mass object A planet is an astronomical body orbit In physics, an orbit is the gravitationally curved trajectory of an physical body, obj ...

shield volcano
in the
Tibesti The Tibesti Mountains are a mountain range in the central Sahara The Sahara (, ; ar, الصحراء الكبرى, ', 'the Greatest Desert') is a desert on the African continent. With an area of , it is the largest hot desert in the world ...

Tibesti
range of northern Chad. The central Sahara is hyperarid, with sparse vegetation. The northern and southern reaches of the desert, along with the highlands, have areas of sparse grassland and desert shrub, with trees and taller shrubs in
wadi Wadi ( ar, وَادِي, wādī), alternatively ''wād'' ( ar, وَاد), North African Arabic Oued, is the Arabic term traditionally referring to a valley A valley is an elongated low area often running between hills or mountains, ...

wadi
s, where moisture collects. In the central, hyperarid region, there are many subdivisions of the great desert:
Tanezrouft The Tanezrouft ( ar, تنزروفت) is a natural region located along the borders of Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital = Algiers , coordinates = , ...
, the
Ténéré The Ténéré (Tuareg The Tuareg people (; also spelt Twareg or Touareg; endonym An endonym (from Greek: , 'inner' + , 'name'; also known as autonym) is a common, internal name A name is a term used for identification by an external obse ...
, the
Libyan Desert The Libyan Desert (not to be confused with the Libyan Sahara) is a geographical region filling the north-eastern  Sahara Desert, from eastern Libya to the Western Desert of Egypt and far northwestern Sudan. On medieval maps, its use predates ...
, the
Eastern Desert The Eastern Desert is the part of the Sahara desert that is located east of the Nile The Nile ( ar, النيل, an-Nīl, , Bohairic , lg, Kiira , Nobiin: Áman Dawū) is a major north-flowing river A river is a natural flowing water ...
, the
Nubian Desert 280px, Fragment of Nubian Desert seen from space The Nubian Desert ( ar, صحراء النوبة, ''Şaḩrā’ an Nūbyah'') is in the eastern region of the Sahara Desert, spanning approximately 400,000 km2 of northeastern Sudan Sudan ...
and others. These extremely arid areas often receive no rain for years. To the north, the Sahara skirts the
Mediterranean Sea The Mediterranean Sea is a connected to the , surrounded by the and almost completely enclosed by land: on the north by and and , on the south by , and on the east by the . The Sea has played a central role in the . Although the Mediterrane ...
in Egypt and portions of Libya, but in
Cyrenaica Cyrenaica ( ; ar, برقة, Barqah; grc-koi, Κυρηναϊκή παρχία Kurēnaïkḗ parkhíā after the city of Cyrene, Libya, Cyrene) is the eastern coastal region of Libya. Also known as ''Pentapolis'' ("Five Cities") in A ...

Cyrenaica
and the
Maghreb The Maghreb (; ar, المغرب, al-Maghrib, lit=the west), also known as Northwest Africa, is the western part of North Africa and the Arab world. The region includes Algeria, Libya, Mauritania (also considered part of West Africa), Morocco and ...

Maghreb
, the Sahara borders the Mediterranean forest, woodland, and scrub eco-regions of northern Africa, all of which have a
Mediterranean climate A Mediterranean climate or dry summer climate is characterized by dry summers and mild, wet winters. The climate Climate is the long-term pattern of weather Weather is the state of the atmosphere, describing for example the degre ...
characterized by hot summers and cool and rainy winters. According to the botanical criteria of Frank White and geographer Robert Capot-Rey, the northern limit of the Sahara corresponds to the northern limit of
date palm ''Phoenix dactylifera'', commonly known as date or date palm, is a flowering plant species in the palm family, Arecaceae The Arecaceae is a family (biology), family of Perennial plant, perennial flowering plants in the Monocotyledon, monoco ...

date palm
cultivation and the southern limit of the range of
esparto Esparto, halfah grass, or esparto grass is a fiber produced from two species of perennial grass Poaceae () or Gramineae () is a large and nearly ubiquitous family In human society, family (from la, familia) is a group of people rela ...

esparto
, a
grass Poaceae () or Gramineae () is a large and nearly ubiquitous family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain ...
typical of the Mediterranean climate portion of the Maghreb and
Iberia The Iberian Peninsula , ** * Aragonese language, Aragonese and Occitan language, Occitan: ''Peninsula Iberica'' ** ** * french: Péninsule Ibérique * mwl, Península Eibérica * eu, Iberiar penintsula also known as Iberia, is a penin ...

Iberia
. The northern limit also corresponds to the
isohyet A contour line (also isoline, isopleth, or isarithm) of a function of two variables is a curve In mathematics, a curve (also called a curved line in older texts) is an object similar to a line (geometry), line, but that does not have to b ...
of annual precipitation. To the south, the Sahara is bounded by the Sahel, a belt of dry
tropical savanna Tropical and subtropical grasslands, savannas, and shrublands is a terrestrial biome defined by the World Wide Fund for Nature The World Wide Fund for Nature (WWF) is an international non-governmental organization founded in 1961 that wor ...
with a summer rainy season that extends across Africa from east to west. The southern limit of the Sahara is indicated botanically by the southern limit of ''
Cornulaca monacantha
Cornulaca monacantha
'' (a drought-tolerant member of the
Chenopodiaceae Amaranthaceae is a family of flowering plants commonly known as the amaranth family, in reference to its type genus '' Amaranthus''. It includes the former goosefoot family Chenopodiaceae and contains about 165 genera and 2,040 species, making i ...
), or northern limit of ''
Cenchrus biflorus ''Cenchrus biflorus'' is a species of annual grass in the family Poaceae Poaceae () or Gramineae () is a large and nearly ubiquitous family In human society, family (from la, familia) is a group of people related either by consangu ...

Cenchrus biflorus
'', a
grass Poaceae () or Gramineae () is a large and nearly ubiquitous family In , family (from la, familia) is a of people related either by (by recognized birth) or (by marriage or other relationship). The purpose of families is to maintain ...
typical of the Sahel. According to climatic criteria, the southern limit of the Sahara corresponds to the isohyet of annual precipitation (this is a long-term average, since
precipitation In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology dates back , though significant progress in meteorology did not begin until the 18th century. The 19th century saw mod ...
varies annually). Important cities located in the Sahara include
Nouakchott Nouakchott (; ; ar, نواكشوط; ber, label=Berber languages, Berber, italic=yes, Nwakcoṭ, originally derived from ber, label=Berber languages, Berber, italic=yes, Nawākšūṭ, "place of the winds") page 273. is the Capital (political), c ...

Nouakchott
, the capital of Mauritania;
Tamanrasset Tamanrasset (; ar, تامنراست), also known as Tamanghasset or Tamenghest, is an oasis In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the land ...

Tamanrasset
,
Ouargla Ouargla (Berber Berber or Berbers may refer to: Culture * Berbers Berbers or ''Imazighen'' ( ber, translit=Imaziɣen, ⵉⵎⴰⵣⵉⵖⵏ, ⵎⵣⵗⵏ; singular: , ) are an ethnic group mostly concentrated in North Africa, specifically ...

Ouargla
,
Béchar Béchar ( ar, بشار) is the capital city of Béchar Province, Algeria. It is also a Communes of Algeria, commune, coextensive with Béchar District, of Béchar Province. In 2008 the city had a population of 165,627, up from 134,954 in 1998, wi ...
,
Hassi Messaoud Hassi Messaoud ( ar, حاسي مسعود) is a town in Ouargla Province, eastern Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital = Algiers , coordinates = , lar ...

Hassi Messaoud
,
Ghardaïa Ghardaïa ( ar, غرداية, Mzab-Berber: ''Taɣerdayt'') is the capital city of Ghardaïa Province Ghardaïa ( ar, ولاية غرداية) is located in the north of the Algerian desert upright=1.5, alt=see caption, Sand dunes i ...

Ghardaïa
, and
El Oued El Oued ( ar, اﻟﻮادي, ber, Suf meaning ''the River''), Souf or Oued Souf is a city, and the capital of El Oued Province, in Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = ...

El Oued
in Algeria;
Timbuktu Timbuktu ( ; french: Tombouctou; tmh, label=Tuareg languages, Tuareg, script=Tfng, ⵜⵏⴱⴾⵜ, Tin Buqt; Koyra Chiini: ) is a city in Mali, situated north of the Niger River. The town is the capital of the Tombouctou Region, one of the e ...

Timbuktu
in Mali;
Agadez Agadez, formerly spelled Agadès, is the fifth largest city in Niger, with a population of 110,497 based on the 2012 census. The capital of Agadez Region, it lies in the Sahara desert, and is also the capital of Aïr, one of the traditional ...
in Niger;
Ghat Ghat, a term used in the Indian subcontinent, depending on the context could refer either to a range of stepped hills with valley A valley is an elongated low area often running between hills or mountains, which will typically contai ...
in Libya; and
Faya-Largeau Faya-Largeau (also known as Faya, ar, فايا لارجو or ) is the largest city in northern Chad and was the capital of the regions of Chad, region of Bourkou-Ennedi-Tibesti Region, Bourkou-Ennedi-Tibesti. It is now in the Borkou Region, which ...
in Chad.


Climate

The Sahara is the world's largest
hot desert upright=1.5, alt=see caption, Sand dunes in the Rub' al Khali ("Empty quarter") in the United Arab Emirates">Rub'_al_Khali.html" ;"title="Sand dunes in the Rub' al Khali">Sand dunes in the Rub' al Khali ("Empty quarter") in the United Arab ...
. It is located in the
horse latitudes The horse latitudes are the latitude In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Eart ...
under the
subtropical ridge The horse latitudes are the latitude In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Eart ...
, a significant belt of semi-permanent subtropical warm-core high pressure where the air from the upper troposphere usually descends, warming and drying the lower troposphere and preventing cloud formation. The permanent absence of clouds allows unhindered light and thermal radiation. The stability of the atmosphere above the desert prevents any convective overturning, thus making rainfall virtually non-existent. As a consequence, the weather tends to be sunny, dry and stable with a minimal chance of rainfall. Subsiding, diverging, dry air masses associated with subtropical
high-pressure system A high-pressure area, high, or anticyclone, is a region where the atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the pressure within the atmosphere of Earth File:Atmosphere gas prop ...
s are extremely unfavorable for the development of convectional showers. The subtropical ridge is the predominant factor that explains the
hot desert climate The desert climate or arid climate (in the Köppen climate classification The Köppen climate classification is one of the most widely used systems. It was first published by German-Russian (1846–1940) in 1884, with several later modific ...
(
Köppen climate classification The Köppen climate classification is one of the most widely used climate classification Climate classification is a way of categorizing the world's s. A climate classification may correlate closely with a category, as climate is a major infl ...
''BWh'') of this vast region. The descending airflow is the strongest and the most effective over the eastern part of the Great Desert, in the Libyan Desert: this is the sunniest, driest and the most nearly "rainless" place on the planet, rivaling the , lying in
Chile Chile, officially the Republic of Chile, is a country in the western part of South America South America is a entirely in the and mostly in the , with a relatively small portion in the . It can also be described as the southern ...

Chile
and
Peru , , image_flag = Flag_of_Peru.svg , image_coat = Escudo_nacional_del_Perú.svg , other_symbol = Great Seal of the State , other_symbol_type = Seal (device), National seal , national_mott ...

Peru
. The rainfall inhibition and the dissipation of cloud cover are most accentuated over the eastern section of the Sahara rather than the western. The prevailing
air mass In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology dates back , though significant progress in meteorology did not begin until the 18th century. The 19th century saw mode ...
lying above the Sahara is the continental tropical (cT) air mass, which is hot and dry. Hot, dry air masses primarily form over the North-African desert from the heating of the vast continental land area, and it affects the whole desert during most of the year. Because of this process, a
thermal low Thermal lows, or heat lows, are non- frontal low-pressure area 250 px, This low-pressure system over Iceland spins counter-clockwise due to balance between the Coriolis and pressure gradient force. In meteorology Meteorology is a branch of ...
is usually noticed near the surface, and is the strongest and the most developed during the summertime. The Sahara High represents the eastern continental extension of the
Azores High The Azores High ( pt, Anticiclone dos Açores) also known as North Atlantic (Subtropical) High/Anticyclone or the Bermuda-Azores High, is a large subtropical The subtropical zones or subtropics are geographical Geography (from Greek ...
, centered over the North Atlantic Ocean. The subsidence of the Sahara High nearly reaches the ground during the coolest part of the year, while it is confined to the upper troposphere during the hottest periods. The effects of local surface low pressure are extremely limited because upper-level subsidence still continues to block any form of air ascent. Also, to be protected against rain-bearing weather systems by the atmospheric circulation itself, the desert is made even drier by its geographical configuration and location. Indeed, the extreme aridity of the Sahara is not only explained by the subtropical high pressure: the
Atlas Mountains The Atlas Mountains ( ar, جِبَال ٱلْأَطْلَس, jibāl al-ʾaṭlas /ʒibaːl al atˤlas/, Tamazight The Berber languages, also known as the Amazigh languages (Berber name: , ; Neo-Tifinagh: ⵜⴰⵎⴰⵣⵉⵖⵜ, Tuareg Tifin ...

Atlas Mountains
of Algeria, Morocco and Tunisia also help to enhance the aridity of the northern part of the desert. These major mountain ranges act as a barrier, causing a strong
rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its Windward and leeward#Meteorological significance, leeward side. Evaporation, Evaporated moistu ...

rain shadow
effect on the leeward side by dropping much of the humidity brought by atmospheric disturbances along the
polar front 400px In meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant ...
which affects the surrounding Mediterranean climates. The primary source of rain in the Sahara is the Intertropical Convergence Zone, a continuous belt of low-pressure systems near the equator which bring the brief, short and irregular
rainy season The wet season (sometimes called the rainy season) is the time of year when most of a region's average annual rainfall Rain is liquid water in the form of droplet Raindrops in a plant. A drop or droplet is a small column of liquid ...

rainy season
to the
Sahel The Sahel (; ar, ساحل ' , "coast, shore") is the ecoclimatic and of in between the to the north and the to the south. Having a , it stretches across the south-central latitudes of between the Atlantic Ocean and the . The Sahel part o ...

Sahel
and southern Sahara. Rainfall in this giant desert has to overcome the physical and atmospheric barriers that normally prevent the production of precipitation. The harsh climate of the Sahara is characterized by: extremely low, unreliable, highly erratic rainfall; extremely high sunshine duration values; high temperatures year-round; negligible rates of
relative humidity Humidity is the concentration of water vapour (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vap ...

relative humidity
; a significant
diurnal temperature variation In meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progr ...
; and extremely high levels of
potential evaporation Potential evaporation (PE) or potential evapotranspiration (PET) is defined as the amount of evaporation that would occur if a sufficient water source were available. If the actual evapotranspiration is considered the net result of atmospheric de ...
which are the highest recorded worldwide.


Temperature

The sky is usually clear above the desert, and the
sunshine duration Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. ...
is extremely high everywhere in the Sahara. Most of the desert has more than 3,600 hours of bright sunshine per year (over 82% of daylight hours), and a wide area in the eastern part has over 4,000 hours of bright sunshine per year (over 91% of daylight hours). The highest values are very close to the theoretical maximum value. A value of 4300 hours (98%) of the time would be recorded in
Upper Egypt Upper Egypt ( ar, صعيد مصر ', shortened to , , locally: ; ) is the southern portion of Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a transcontinental country This is a list of countries lo ...
(
Aswan Aswan (, also ; ar, أسوان, ʾAswān ; cop, Ⲥⲟⲩⲁⲛ, Souan ) is a city in the south of Egypt Egypt ( ; ar, مِصر ), officially the Arab Republic of Egypt, is a transcontinental country spanning the North Africa, northeast ...

Aswan
,
Luxor Luxor (; ar, الأقصر ', , Upper Egyptian pronunciation: ; Sahidic ''Pape'', ) is a city in Upper (southern) Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a transcontinental country This is ...

Luxor
) and in the Nubian Desert (
Wadi Halfa Wādī Ḥalfā ( ar, وادي حلفا) is a city in the Northern state of Sudan Sudan (; ar, السودان, as-Sūdān), officially the Republic of the Sudan ( ar, جمهورية السودان, link=no, Jumhūriyyat as-Sūdān), is a c ...
). The annual average is around 2,800 kWh/(m2 year) in the Great Desert. The Sahara has a huge potential for solar energy production. The high position of the Sun, the extremely low relative humidity, and the lack of
vegetation Vegetation is an assemblage of plant Plants are predominantly photosynthetic Photosynthesis is a process used by plants and other organisms to Energy transformation, convert light energy into chemical energy that, through cellular re ...

vegetation
and rainfall make the Great Desert the hottest large region in the world, and the hottest place on Earth during summer in some spots. The average high temperature exceeds during the hottest month nearly everywhere in the desert except at very high altitudes. The world's highest officially recorded average daily high temperature was in a remote desert town in the
Algerian Desert The Algerian Desert ( ar, الصحراء الجزائرية) is located in north-central Africa and is part of the Sahara Desert. The desert occupies more than four-fifths of Algerian territory. Its expansion starts from the Saharan Atlas as a st ...

Algerian Desert
called Bou Bernous, at an elevation of above sea level, and only
Death Valley, California Death Valley is a desert valley in Eastern California, in the northern Mojave Desert The Mojave Desert ( ; mov, Hayikwiir Mat'aar) is an arid rain-shadow desert and the driest desert upright=1.5, alt=see caption, Sand dunes in th ...

Death Valley, California
rivals it. Other hot spots in Algeria such as Adrar,
Timimoun Timimoun ( ar, ﺗﻴﻤﻴﻤﻮن) is a town and Communes of Algeria, commune, and capital of Timimoun District, in Adrar Province, south-central Algeria. According to the 2008 census it has a population of 33,060, up from 28,595 in 1998, with an ...

Timimoun
,
In Salah In Salah or officially Aïn Salah ( ar, عين صالح) is the oasis town in central Algeria that is the capital of the In Salah Province and In Salah District. It was once an important trade link of the Trans-Saharan trade, trans-Saharan caravan ...

In Salah
, Ouallene,
Aoulef Aoulef ( ar, أولف , translit=Awlaf) is a town and commune An intentional community is a voluntary residential community designed from the start to have a high degree of group cohesiveness, social cohesion and teamwork. The members of a ...

Aoulef
,
Reggane Reggane (from Berber "Argan"; ar, رقان) is a town and commune, and the capital of Reggane District, in Adrar Province, central Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 ...
with an elevation between above sea level get slightly lower summer average highs, around during the hottest months of the year. Salah, well known in Algeria for its extreme heat, has average high temperatures of , , and in June, July, August and September respectively. There are even hotter spots in the Sahara, but they are located in extremely remote areas, especially in the
Azalai The Azalai (Tuareg language, Tamasheq, var. Azalay) is a semi-annual salt Camel train, caravan route practiced by Tuareg people, Tuareg traders in the Sahara desert between Timbuktu and the Taoudenni salt mine in Mali, or the act of traveling wit ...
, lying in northern Mali. The major part of the desert experiences around three to five months when the average high strictly exceeds ; while in the southern central part of the desert, there are up to six or seven months when the average high temperature strictly exceeds . Some examples of this are
Bilma Bilma is an oasis In geography, an oasis (, plural oases, ) is a fertile land in a desert or semi-desert environment. Sand and ground temperatures are even more extreme. During daytime, the sand temperature is extremely high: it can easily reach or more. A sand temperature of 83.5 °C (182.3 °F) has been recorded in
Port Sudan Port Sudan ( ar, بور سودان, Būr Sūdān) is a port city in eastern Sudan, and the capital of the state of Red Sea (state), Red Sea. , it has 489,725 residents. Port Sudan is located on the Red Sea, and it is recognized as Sudan's main seap ...

Port Sudan
. Ground temperatures of have been recorded in the Adrar of Mauritania and a value of 75 °C (167 °F) has been measured in
Borkou Borku (french: Borkou) or Borgu (') is a region of Central Africa Central Africa is a subregion A subregion is a part of a larger region In geography Geography (from Greek: , ''geographia'', literally "earth description") is a ...

Borkou
, northern Chad. Due to lack of cloud cover and very low humidity, the desert usually has high
diurnal temperature variation In meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progr ...
s between days and nights. However, it is a myth that the nights are especially cold after extremely hot days in the Sahara. On average, nighttime temperatures tend to be cooler than in the daytime. The smallest variations are found along the coastal regions due to high humidity and are often even lower than a difference, while the largest variations are found in inland desert areas where the humidity is the lowest, mainly in the southern Sahara. Still, it is true that winter nights can be cold, as it can drop to the freezing point and even below, especially in high-elevation areas. The frequency of subfreezing winter nights in the Sahara is strongly influenced by the
North Atlantic Oscillation#REDIRECT North Atlantic oscillation {{Redirect category shell, 1= {{R from other capitalisation ...
(NAO), with warmer winter temperatures during negative NAO events and cooler winters with more frosts when the NAO is positive. This is because the weaker clockwise flow around the eastern side of the subtropical anticyclone during negative NAO winters, although too dry to produce more than negligible precipitation, does reduce the flow of dry, cold air from higher latitudes of Eurasia into the Sahara significantly.


Precipitation

The average annual rainfall ranges from very low in the northern and southern fringes of the desert to nearly non-existent over the central and the eastern part. The thin northern fringe of the desert receives more winter cloudiness and rainfall due to the arrival of
low pressure system In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology dates back , though significant progress in meteorology did not begin until the 18th century. The 19th century saw mode ...
s over the Mediterranean Sea along the polar front, although very attenuated by the rain shadow effects of the mountains and the annual average rainfall ranges from to . For example,
Biskra Biskra ( ar, بسكرة ; ; Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the area around Rome, known as Latium. Through the p ...

Biskra
, Algeria, and
Ouarzazate Ouarzazate (, ; ar, ورزازات, ''Warzāzāt''; ary, وارزازات, ''Wārzāzāt''; ber, label= Berber, ⵡⴰⵔⵣⴰⵣⴰⵜ, ''Warzazat''), nicknamed ''the door of the desert'', is a city and capital of Ouarzazate Province in the r ...

Ouarzazate
, Morocco, are found in this zone. The southern fringe of the desert along the border with the Sahel receives summer cloudiness and rainfall due to the arrival of the Intertropical Convergence Zone from the south and the annual average rainfall ranges from to . For example, Timbuktu, Mali and
Agadez Agadez, formerly spelled Agadès, is the fifth largest city in Niger, with a population of 110,497 based on the 2012 census. The capital of Agadez Region, it lies in the Sahara desert, and is also the capital of Aïr, one of the traditional ...
, Niger are found in this zone. The vast central hyper-arid core of the desert is virtually never affected by northerly or southerly atmospheric disturbances and permanently remains under the influence of the strongest anticyclonic weather regime, and the annual average rainfall can drop to less than . In fact, most of the Sahara receives less than . Of the of desert land in the Sahara, an area of about (about 31% of the total area) receives an annual average rainfall amount of or less, while some (about 17% of the total area) receives an average of or less. The annual average rainfall is virtually zero over a wide area of some in the eastern Sahara comprising deserts of: Libya, Egypt and Sudan (
Tazirbu Tazerbu ( ar, تازربو), is an oasis In geography Geography (from Greek: , ''geographia'', literally "earth description") is a field of science devoted to the study of the lands, features, inhabitants, and phenomena of the Earth ...
,
Kufra Kufra () is a basinBertarelli (1929), p. 514. and oasis group in the Kufra District of southeastern Cyrenaica in Libya Libya (; ar, ليبيا, Lībīyā), officially the State of Libya, ( ar, دولة ليبيا, Dawlat Lībīyā) is a cou ...
, Dakhla,
Kharga The Kharga Oasis ( ar, الخارجة ', ) "the outer"; (''Di)Wah Ēnhib'', "Oasis of Hib", ''(Di)Wah Ēmpsoy'', "Oasis of Psoi") is the southernmost of Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a tr ...

Kharga
,
Farafra The Farafra depression ( ar, واحة الفرافرة, ) is a geological depression, the second biggest by size in Western Egypt Egypt ( ; ar, مِصر ), officially the Arab Republic of Egypt, is a transcontinental country spanning th ...
, ,
Asyut AsyutAlso spelled ''Assiout'' or ''Assiut''. ( ar, أسيوط ' , ''Siōwt'' ) is the capital of the modern Asyut Governorate Asyut Governorate is one of the many governorates of Egypt. It stretches across a section of the Nile River. The cap ...
,
Sohag Sohag ( , ), also spelled as ''Sawhāj'', ''Suhag'' and ''Suhaj'', is a city on the west bank of the Nile The Nile, , Bohairic , lg, Kiira , Nobiin Nobiin, or Mahas, is a Northern Nubian languages, Nubian language of the Nilo-Sahara ...

Sohag
, Luxor, Aswan,
Abu Simbel Abu Simbel (also Abu Simbal, Ebsambul or Isambul; ar, أبو سنبل, Abū Sinbal or ar, أبو سمبل, Abū Simbal) is a village in the Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a tra ...

Abu Simbel
, Wadi Halfa) where the long-term mean approximates per year. Rainfall is very unreliable and erratic in the Sahara as it may vary considerably year by year. In full contrast to the negligible annual rainfall amounts, the annual rates of potential evaporation are extraordinarily high, roughly ranging from per year to more than per year in the whole desert. Nowhere else on Earth has air been found as dry and evaporative as in the Sahara region. However, at least two instances of snowfall have been recorded in Sahara, in February 1979 and December 2016, both in the town of
Ain Sefra Ain (, ; frp, En) is a Departments of France, department named after the Ain River on the eastern edge of France. It is part of the Auvergne-Rhône-Alpes region and bordered by the rivers Saône and Rhône. Ain is composed of four geograph ...
.


Desertification and prehistoric climate

One theory for the formation of the Sahara is that the monsoon in Northern Africa was weakened because of glaciation during the
Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic The Cenozoic ( ; ) is Earth's current geological era An era is a span of time defined for the purposes of chronology or historiography, as in the regnal ...
period, starting two or three million years ago. Another theory is that the monsoon was weakened when the ancient
Tethys Sea The Tethys Ocean ( el, Τηθύς ''Tēthús''), also called the Tethys Sea or the Neo-Tethys, was an ocean during much of the Mesozoic The Mesozoic Era ( ), also called the Age of Reptiles and the Age of Conifers, is the second-to-last era ...
dried up during the
Tortonian The Tortonian is in the geologic time scale The geologic time scale (GTS) is a system of chronological dating Chronological dating, or simply dating, is the process of attributing to an object or event a date in the past, allowing such object ...
period around 7 million years. The climate of the Sahara has undergone enormous variations between wet and dry over the last few hundred thousand years, believed to be caused by long-term changes in the
North African climate cycleNorth African climate cycles have a unique history that can be traced back millions of years. The cyclic climate pattern of the Sahara is characterized by significant shifts in the strength of the North African Monsoon. When the North African Monsoon ...
that alters the path of the
North African MonsoonNorth African climate cycles have a unique history that can be traced back millions of years. The cyclic climate Climate is the long-term average of weather, typically averaged over a period of 30 years. More rigorously, it is the mean and variabi ...
– usually southward. The cycle is caused by a 41000-year cycle in which the tilt of the earth changes between 22° and 24.5°. At present (2000 ACE), we are in a dry period, but it is expected that the Sahara will become green again in 15000 years (17000 ACE). When the North African monsoon is at its strongest annual precipitation and subsequent vegetation in the Sahara region increase, resulting in conditions commonly referred to as the " green Sahara". For a relatively weak North African monsoon, the opposite is true, with decreased annual precipitation and less vegetation resulting in a phase of the Sahara climate cycle known as the "desert Sahara". The idea that changes in
insolation Solar irradiance is the power Power typically refers to: * Power (physics) In physics, power is the amount of energy transferred or converted per unit time. In the International System of Units, the unit of power is the watt, equal to one j ...

insolation
(solar heating) caused by long-term changes in Earth's orbit are a controlling factor for the long-term variations in the strength of monsoon patterns across the globe was first suggested by Rudolf Spitaler in the late nineteenth century, The hypothesis was later formally proposed and tested by the meteorologist John Kutzbach in 1981. Kutzbach's ideas about the impacts of insolation on global monsoonal patterns have become widely accepted today as the underlying driver of long-term monsoonal cycles. Kutzbach never formally named his hypothesis and as such it is referred to here as the " Orbital Monsoon Hypothesis" as suggested by Ruddiman in 2001. During the last
glacial period A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age An ice age is a long period of reduction in the temperature of Earth Earth is the third planet from the Sun and the ...
, the Sahara was much larger than it is today, extending south beyond its current boundaries. The end of the glacial period brought more rain to the Sahara, from about 8000 BCE to 6000 BCE, perhaps because of
low pressure area In meteorology Meteorology is a branch of the atmospheric sciences Atmospheric science is the study of the Earth's atmosphere File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. L ...
s over the collapsing
ice sheet In glaciology Lateral moraine on a glacier joining the Gorner Glacier, Zermatt">Gorner_Glacier.html" ;"title="moraine on a glacier joining the Gorner Glacier">moraine on a glacier joining the Gorner Glacier, Zermatt, Swiss Alps. The moraine is ...

ice sheet
s to the north. Once the ice sheets were gone, the northern Sahara dried out. In the southern Sahara, the drying trend was initially counteracted by the
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology ...

monsoon
, which brought rain further north than it does today. By around 4200 BCE, however, the monsoon retreated south to approximately where it is today,Sahara's Abrupt Desertification Started by Changes in Earth's Orbit
Accelerated by Atmospheric and Vegetation Feedbacks.
leading to the gradual
desertification Desertification is a type of land degradation Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land. It is viewed as any change or distu ...
of the Sahara. The Sahara is now as dry as it was about 13,000 years ago.
Lake Chad Lake Chad (french: links=no, Lac Tchad) is a historically large, shallow, endorheic lake Image:LakeBadwater crop.jpg, 230px, Death Valley, Spring 2005: ephemeral Lake Badwater in the flooded Badwater Basin An endorheic lake (also called a sink ...

Lake Chad
is the remnant of a former inland sea, paleolake Mega-Chad, which existed during the African humid period. At its largest extent, sometime before 5000 BCE, Lake Mega-Chad was the largest of four Saharan paleolakes, and is estimated to have covered an area of 350,000 km2. The
Sahara pump theory The Sahara pump theory is a hypothesis that explains how flora Flora is all the plant life present in a particular region or time, generally the naturally occurring (indigenous (ecology), indigenous) native plant, native plants. Sometimes b ...
describes this cycle. During periods of a wet or " Green Sahara", the Sahara becomes a
savanna A savanna or savannah is a mixed woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the ''plurale tantum'' woods), a low-density forest forming open habitats ...

savanna
grassland and various flora and fauna become more common. Following inter-pluvial arid periods, the Sahara area then reverts to desert conditions and the flora and fauna are forced to retreat northwards to the
Atlas Mountains The Atlas Mountains ( ar, جِبَال ٱلْأَطْلَس, jibāl al-ʾaṭlas /ʒibaːl al atˤlas/, Tamazight The Berber languages, also known as the Amazigh languages (Berber name: , ; Neo-Tifinagh: ⵜⴰⵎⴰⵣⵉⵖⵜ, Tuareg Tifin ...

Atlas Mountains
, southwards into
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 17 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Mauritania ...

West Africa
, or eastwards into the
Nile Valley The Nile, , Bohairic , lg, Kiira , Nobiin Nobiin, or Mahas, is a Northern Nubian languages, Nubian language of the Nilo-Saharan languages, Nilo-Saharan language family. "Nobiin" is the genitive case, genitive form of ''Nòòbíí'' ("Nubi ...

Nile Valley
. This separates
population Population typically refers the number of people in a single area whether it be a city or town, region, country, or the world. Governments typically quantify the size of the resident population within their jurisdiction by a process called a ...

population
s of some of the species in areas with different
climate Climate is the long-term pattern of weather Weather is the state of the atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a la ...

climate
s, forcing them to , possibly giving rise to
allopatric speciation Allopatric speciation (from Ancient Greek ἄλλος, ''allos'', meaning "other", and πατρίς, ''patris'', "fatherland"), also referred to as geographic speciation, vicariant speciation, or its earlier name, the dumbbell model, is a mode of ...
. It is also proposed that humans accelerated the drying out period from 6000 to 2500 BCE by pastoralists overgrazing available grassland.


Evidence for cycles

The growth of
speleothems A speleothem (; from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is ap ...
(which requires rainwater) was detected in Hol-Zakh, Ashalim, Even-Sid, Ma'ale-ha-Meyshar, Ktora Cracks, Nagev Tzavoa Cave, and elsewhere, and has allowed tracking of prehistoric rainfall. The Red Sea coastal route was extremely arid before 140 and after 115 kya (thousands of years ago). Slightly wetter conditions appear at 90–87 kya, but it still was just one tenth the rainfall around 125 kya. In the southern
Negev Desert The Negev or Negeb (; he, הַנֶּגֶב, ha-Négev; ar, ٱلنَّقَب, an-Naqab) is a desert and semidesert region of southern Israel. The region's largest city and administrative capital is Beersheba (pop. ), in the north. At its southe ...

Negev Desert
speleothems did not grow between 185 and 140 kya ( MIS 6), 110–90 (MIS 5.4–5.2), nor after 85 kya nor during most of the interglacial period (MIS 5.1), the glacial period and
Holocene The Holocene ( ) is the current geological epoch In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age (geology), age but shorter than a period (geology), period. The current epoch is the Holocene E ...
. This suggests that the southern Negev was arid-to-hyper-arid in these periods. During the
Last Glacial Maximum The Last Glacial Maximum (LGM), also referred to as the Late Glacial Maximum, was the most recent time during the Last Glacial Period that ice sheets In glaciology Lateral moraine on a glacier joining the Gorner Glacier, Zermatt">Gorner_Gla ...
(LGM) the Sahara desert was more extensive than it is now with the extent of the tropical forests being greatly reduced, and the lower temperatures reduced the strength of the
Hadley Cell#REDIRECT Hadley cell The Hadley cell, named after George Hadley, is a global scale tropical atmospheric circulation Atmospheric circulation is the large-scale movement of Atmosphere of Earth, air and together with ocean circulation is the mean ...
. This is a climate cell which causes rising tropical air of the Inter-Tropical Convergence Zone (ITCZ) to bring rain to the tropics, while dry descending air, at about 20 degrees north, flows back to the equator and brings desert conditions to this region. It is associated with high rates of wind-blown mineral dust, and these dust levels are found as expected in marine cores from the north tropical Atlantic. But around 12,500 BCE the amount of dust in the cores in the Bølling/ Allerød phase suddenly plummets and shows a period of much wetter conditions in the Sahara, indicating a Dansgaard-Oeschger (DO) event (a sudden warming followed by a slower cooling of the climate). The moister Saharan conditions had begun about 12,500 BCE, with the extension of the ITCZ northward in the northern hemisphere summer, bringing moist wet conditions and a savanna climate to the Sahara, which (apart from a short dry spell associated with the
Younger Dryas The Younger Dryas (around 12,900 to 11,700 years BP) was a return to glacial conditions after the Late Glacial Interstadial The Late Glacial Interstadial (LGI) c.14,670 to c.12,890 BP represents the first ''pronounced'' warming since the end o ...
) peaked during the Holocene thermal maximum climatic phase at 4000 BCE when mid-latitude temperatures seem to have been between 2 and 3 degrees warmer than in the recent past. Analysis of
Nile River The Nile, , Bohairic , lg, Kiira , Nobiin Nobiin, or Mahas, is a Northern Nubian languages, Nubian language of the Nilo-Saharan languages, Nilo-Saharan language family. "Nobiin" is the genitive case, genitive form of ''Nòòbíí'' ("Nub ...
deposited sediments in the delta also shows this period had a higher proportion of sediments coming from the
Blue Nile The Blue Nile (; ), is a river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course ...

Blue Nile
, suggesting higher rainfall also in the
Ethiopian Highlands The Ethiopian Highlands is a rugged mass of mountain A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. A mountain differs from a plateau in having a limited summit are ...
. This was caused principally by a stronger
monsoon A monsoon () is traditionally a seasonal reversing wind accompanied by corresponding changes in precipitation In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology ...

monsoon
al circulation throughout the sub-tropical regions, affecting India, Arabia and the Sahara.
Lake Victoria Lake Victoria ( luo, Nam Lolwe; lg, 'Nnalubaale; rw, Nyanza; also ''Ukerewe'') is one of the African Great Lakes. Though having multiple local language names, the lake was renamed after Queen Victoria by the explorer John Hanning Speke, the ...

Lake Victoria
only recently became the source of the
White Nile The White Nile ( ar, النيل الأبيض ') is a river in Africa, one of the two main tributaries A tributary, or affluent, is a stream A stream is a body of water (Lysefjord) in Norway Norway, officially the Kingdom ...

White Nile
and dried out almost completely around 15 kya. The sudden subsequent movement of the ITCZ southwards with a
Heinrich event A Heinrich event is a natural phenomenon in which large groups of iceberg An iceberg is a piece of freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water Water is an Inorganic compound, inorganic ...
(a sudden cooling followed by a slower warming), linked to changes with the
El Niño-Southern Oscillation EL, El or el may refer to: Religion * El (deity) (also ʼIl, uga, 𐎛𐎍; phn, 𐤀𐤋; he, אֵל; syr, ܐܠ; ar, إيل or ; cognate to akk, 𒀭, ilu) is a Northwest Semitic languages, Northwest Semitic word meaning "god" or ...
cycle, led to a rapid drying out of the Saharan and Arabian regions, which quickly became desert. This is linked to a marked decline in the scale of the Nile floods between 2700 and 2100 BCE.


Ecoregions

The Sahara comprises several distinct
ecoregion An ecoregion (ecological region) or ecozone (ecological zone) is an ecologically Ecology (from el, οἶκος, "house" and el, -λογία, label=none, "study of") is the study of the relationships between living organisms, including h ...
s. With their variations in temperature, rainfall, elevation, and soil, these regions harbor distinct communities of plants and animals. The
Atlantic coastal desert The Atlantic coastal desert is the westernmost ecoregion An ecoregion (ecological region) or ecozone (ecological zone) is an ecology, ecologically and geographically defined area that is smaller than a bioregion, which in turn is smaller tha ...
is a narrow strip along the Atlantic coast where fog generated offshore by the cool
Canary Current The Canary Current is a wind-driven surface current that is part of the North Atlantic Gyre. This eastern boundary current branches south from the North Atlantic Current and flows southwest about as far as Senegal where it turns west and later jo ...
provides sufficient moisture to sustain a variety of
lichen A lichen ( , ) is a composite organism In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecu ...

lichen
s,
succulents ''. In botany Botany, also called , plant biology or phytology, is the science Science (from the Latin word ''scientia'', meaning "knowledge") is a systematic enterprise that Scientific method, builds and Taxonomy (general), organizes ...
, and shrubs. It covers an area of in the south of Morocco and Mauritania. The
North Saharan steppe and woodlands The North Saharan steppe and woodlands is a desert upright=1.5, alt=see caption, Sand dunes in the Rub' al Khali ("Empty quarter") in the United Arab Emirates">Rub'_al_Khali.html" ;"title="Sand dunes in the Rub' al Khali">Sand dunes in t ...
is along the northern desert, next to the
Mediterranean forests, woodlands, and scrub Mediterranean forests, woodlands, and scrub is a biome defined by the World Wide Fund for Nature. The biome is generally characterized by dry summers and rainy winters, although in some areas rainfall may be uniform. Summers are typically hot in ...
ecoregions of the northern Maghreb and Cyrenaica. Winter rains sustain shrublands and dry woodlands that form a transition between the Mediterranean climate regions to the north and the hyper-arid Sahara proper to the south. It covers in Algeria, Egypt, Libya, Mauritania, Morocco, and Tunisia. The Sahara Desert ecoregion covers the hyper-arid central portion of the Sahara where rainfall is minimal and sporadic. Vegetation is rare, and this ecoregion consists mostly of sand dunes (''erg, chech, raoui''), stone plateaus (''hamadas''), gravel plains (''reg''), dry valleys (''wadis''), and salt flats. It covers of: Algeria, Chad, Egypt, Libya, Mali, Mauritania, Niger, and Sudan. The
South Saharan steppe and woodlands The South Saharan steppe and woodlands, also known as the South Sahara desert, is a deserts and xeric shrublands ecoregion An ecoregion (ecological region) or ecozone (ecological zone) is an ecology, ecologically and geographically defined ar ...
ecoregion is a narrow band running east and west between the hyper-arid Sahara and the Sahel savannas to the south. Movements of the equatorial Intertropical Convergence Zone (ITCZ) bring summer rains during July and August which average but vary greatly from year to year. These rains sustain summer pastures of grasses and herbs, with dry woodlands and shrublands along seasonal watercourses. This ecoregion covers in Algeria, Chad, Mali, Mauritania, and Sudan. In the West Saharan montane xeric woodlands, several volcanic highlands provide a cooler, moister environment that supports Saharo-Mediterranean woodlands and shrublands. The ecoregion covers , mostly in the Tassili n'Ajjer of Algeria, with smaller enclaves in the Aïr of Niger, the Dhar Adrar of Mauritania, and the Adrar des Iforas of Mali and Algeria. The Tibesti-Jebel Uweinat montane xeric woodlands ecoregion consists of the Tibesti and Jebel Uweinat highlands. Higher and more regular rainfall and cooler temperatures support woodlands and shrublands of date palm, acacias, Myrtus, myrtle, oleander, tamarix, and several rare and endemic plants. The ecoregion covers in the Tibesti of Chad and Libya, and Jebel Uweinat on the border of Egypt, Libya, and Sudan. The Saharan halophytics is an area of seasonally flooded saline depressions which is home to halophytic (salt-adapted) plant communities. The Saharan halophytics cover including: the Qattara Depression, Qattara and Siwa Depression, Siwa depressions in northern Egypt, the Tunisian salt lakes of central Tunisia, Chott Melghir in Algeria, and smaller areas of Algeria, Mauritania, and the southern part of Morocco. The
Tanezrouft The Tanezrouft ( ar, تنزروفت) is a natural region located along the borders of Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 = , capital = Algiers , coordinates = , ...
is one of the Sahara's most arid regions, with no vegetation and very little life. A barren, flat gravel plain, it extends south of
Reggane Reggane (from Berber "Argan"; ar, رقان) is a town and commune, and the capital of Reggane District, in Adrar Province, central Algeria ) , image_map = Algeria (centered orthographic projection).svg , map_caption = , image_map2 ...
in Algeria towards the Adrar des Ifoghas highlands in northern Mali.


Flora and fauna

The flora of the Sahara is highly diversified based on the bio-geographical characteristics of this vast desert. Floristics, Floristically, the Sahara has three zones based on the amount of rainfall received – the Northern (Mediterranean), Central and Southern Zones. There are two transitional zones – the Mediterranean-Sahara transition and the Sahel transition zone. The Saharan flora comprises around 2800 species of vascular plants. Approximately a quarter of these are endemism, endemic. About half of these species are common to the flora of the Arabian deserts. The central Sahara is estimated to include 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, by growing lower to avoid water loss by strong winds, by storing water in their thick stems to use it in dry periods, by having long roots that travel horizontally to reach the maximum area of water and to find any surface moisture, and by having small thick leaves or needles to prevent water loss by evapotranspiration. Plant leaves may dry out totally and then recover. Several species of fox live in the Sahara including: the fennec fox, pale fox and Rüppell's fox. The addax, a large white antelope, can go nearly a year in the desert without drinking. The dorcas gazelle is a north African gazelle that can also go for a long time without water. Other notable gazelles include the rhim gazelle and dama gazelle. The Saharan cheetah (northwest African cheetah) lives in Algeria, Togo, Niger, Mali, Benin, and Burkina Faso. There remain fewer than 250 mature cheetahs, which are very cautious, fleeing any human presence. The cheetah avoids the sun from April to October, seeking the shelter of shrubs such as balanites and acacias. They are unusually pale. The other cheetah subspecies (northeast African cheetah) lives in Chad, Sudan and the eastern region of Niger. However, it is currently extinct in the wild in Egypt and Libya. There are approximately 2000 mature individuals left in the wild. Other animals include the monitor lizards, hyrax, Cerastes (genus), sand vipers, and small populations of African wild dog, in perhaps only 14 countries and red-necked ostrich. Other animals exist in the Sahara (birds in particular) such as African silverbill and black-faced firefinch, among others. There are also small desert crocodiles in Mauritania and the Ennedi Plateau of Chad. The deathstalker scorpion can be long. Its venom contains large amounts of agitoxin and scyllatoxin and is very dangerous; however, a sting from this scorpion rarely kills a healthy adult. The Saharan silver ant is unique in that due to the extreme high temperatures of their habitat, and the threat of predators, the ants are active outside their nest for only about ten minutes per day. Dromedary camels and goats are the domesticated animals most commonly found in the Sahara. Because of its qualities of endurance and speed, the dromedary is the favourite animal used by nomads. Human activities are more likely to affect the habitat in areas of permanent water (oases) or where water comes close to the surface. Here, the local pressure on natural resources can be intense. The remaining populations of large mammals have been greatly reduced by hunting for food and recreation. In recent years development projects have started in the deserts of Algeria and Tunisia using irrigated water pumped from underground aquifers. These schemes often lead to soil degradation and Soil salinity, salinization. Researchers from Hacettepe University have reported that Saharan soil may have bio-available iron and also some essential macro and micro nutrient elements suitable for use as fertilizer for growing wheat.


History

People lived on the edge of the desert thousands of years ago,Discover Magazine
2006-Oct.
since the end of the last glacial period. In the Central Sahara, engraved and painted rock art were created perhaps as early as 10,000 years ago, spanning the Bubaline Period, Kel Essuf Period, Round Head Period, Pastoral Period, Caballine Period, and Cameline Period. The Sahara was then a much wetter place than it is today. Over 30,000 petroglyphs of river animals such as crocodilesNational Geographic News
17 June 2006.
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 lush in vegetation, except in the Nile Valley, at a few oasis, oases, and in the northern highlands, where Mediterranean plants such as the olive tree are found to grow. It was long believed that the region had been this way since about 1600 BCE, after shifts in axial tilt, Earth's axis increased temperatures and decreased precipitation, which led to the abrupt desertification of North Africa about 5,400 years ago.


Kiffians

The Kiffian culture is a prehistoric industry, or domain, that existed between 10,000 and 8,000 years ago in the Sahara, during the Neolithic Subpluvial. Human remains from this culture were found in 2000 at a site known as Gobero, located in
Niger ) , official_languages = French , languages_type = National language A national language is a language A language is a structured system of communication used by humans, including speech (spoken language), gestures (Signed languag ...

Niger
in the Ténéré, Ténéré Desert. The site is known as the largest and earliest grave of Stone Age people in the Sahara desert. The Kiffians were skilled Hunter-gatherer, hunters. Bones of many large savannah animals that were discovered in the same area suggest that they lived on the shores of a lake that was present during the Holocene Wet Phase, a period when the Sahara was verdant and wet. The Kiffian people were tall, standing over six feet in height. Craniometric analysis indicates that this early
Holocene The Holocene ( ) is the current geological epoch In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age (geology), age but shorter than a period (geology), period. The current epoch is the Holocene E ...
population was closely related to the Late Pleistocene Iberomaurusians and early Holocene Capsian culture, Capsians of the Maghreb, as well as mid-Holocene Mechta-Afalou, Mechta groups. Traces of the Kiffian culture do not exist after 8,000 years ago, as the Sahara went through a dry period for the next thousand years. After this time, the Tenerian culture colonized the area.


Tenerians

Gobero was discovered in 2000 during an archaeological expedition led by Paul Sereno, which sought dinosaur remains. Two distinct prehistoric cultures were discovered at the site: the early
Holocene The Holocene ( ) is the current geological epoch In geochronology, an epoch is a subdivision of the geologic timescale that is longer than an age (geology), age but shorter than a period (geology), period. The current epoch is the Holocene E ...
Kiffian culture, and the middle Holocene Tenerian culture. The post-Kiffian desiccation lasted until around 4600 BCE, when the earliest artefacts associated with the Tenerians have been dated to. Some 200 skeletons have been discovered at Gobero. The Tenerians were considerably shorter in height and less robust than the earlier Kiffians. Craniometric analysis also indicates that they were osteologically distinct. The Kiffian skulls are akin to those of the Late Pleistocene Iberomaurusians, early Holocene Capsian culture, Capsians, and mid-Holocene Mechta-Afalou, Mechta groups, whereas the Tenerian crania are more like those of Mediterranean groups. Graves show that the Tenerians observed spiritual traditions, as they were buried with artifacts such as jewelry made of hippo tusks and clay pots. The most interesting find is a triple burial, dated to 5300 years ago, of an adult female and two children, estimated through their teeth as being five and eight years old, hugging each other. Pollen residue indicates they were buried on a bed of flowers. The three are assumed to have died within 24 hours of each other, but as their skeletons hold no apparent trauma (they did not die violently) and they have been buried so elaborately – unlikely if they had died of a plague – the cause of their deaths is a mystery.


Tashwinat Mummy

Uan Muhuggiag appears to have been inhabited from at least the 6th millennium BCE to about 2700 BCE, although not necessarily continuously. The most noteworthy find at Uan Muhuggiag is the well-preserved mummy of a young boy of approximately years old. The child was in a fetal position, then embalmed, then placed in a sack made of antelope skin, which was insulated by a layer of leaves. The boy's organs were removed, as evidenced by incisions in his stomach and thorax, and an organic preservative was inserted to stop his body from decomposing. An ostrich eggshell necklace was also found around his neck. Radiocarbon dating determined the age of the mummy to be approximately 5600 years old, which makes it about 1000 years older than the earliest previously recorded mummy in ancient
Egypt Egypt ( ar, مِصر, Miṣr), officially the Arab Republic of Egypt, is a transcontinental country This is a list of countries located on more than one continent A continent is one of several large landmasses. Generally identi ...

Egypt
. In 1958–59, an archaeological expedition led by Antonio Ascenzi conducted anthropological, radiological, histological and chemical analyses on the Uan Muhuggiag mummy. The team claimed that the mummy was a 30-month-old child of uncertain sex who possessed Negroid features (Note: "negroid" is derived from a disproven theory of biological race, and modern genetics has since rendered such terminology obsolete). A long incision on the specimen's abdominal wall also indicated that the body had been initially mummified by evisceration and later underwent natural desiccation. One other individual, an adult, was found at Uan Muhuggiag, buried in a crouched position. However, the body showed no evidence of evisceration or any other method of preservation. The body was estimated to date from about 7500 BP.


Nubians

During the Neolithic Era, before the onset of
desertification Desertification is a type of land degradation Land degradation is a process in which the value of the biophysical environment is affected by a combination of human-induced processes acting upon the land. It is viewed as any change or distu ...
around 9500 BCE, the central Sudan had been a rich environment supporting a large population ranging across what is now barren desert, like the Wadi el-Qa'ab. By the 5th millennium BCE, the people who inhabited what is now called Nubia, were full participants in the "agricultural revolution", living a settled lifestyle with domesticated plants and animals. Saharan rock art of cattle and herdsmen suggests the presence of a cattle cult like those found in Sudan and other pastoral societies in Africa today. Megaliths found at Nabta Playa are overt examples of probably the world's first known archaeoastronomy devices, predating Stonehenge by some 2,000 years. This complexity, as observed at Nabta Playa, and as expressed by different levels of authority within the society there, likely formed the basis for the structure of both the Neolithic society at Nabta and the Old Kingdom of Egypt.


Egyptians

By 6000 BCE 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 BCE centered predominantly on cereal and animal agriculture: cattle, goats, pigs and sheep. Metal objects replaced prior ones of stone. Tanning of animal skins, pottery and weaving were commonplace in this era also. There are indications of seasonal or only temporary occupation of the Al Fayyum in the 6th millennium BCE, with food activities centering on fishing, hunting and food-gathering. Stone arrowheads, knives and scrapers from the era are commonly found.Fayum, Qarunian
(Fayum B, about 6000–5000 BCE?)
Digital Egypt
Burial items included pottery, jewelry, farming and hunting equipment, and assorted foods including dried meat and fruit. Burial in desert environments appears to enhance Egyptian preservation rites, and the dead were buried facing due west.Predynastic (5,500–3,100 BCE), Tour Egypt. By 3400 BCE, the Sahara was as dry as it is today, due to reduced precipitation and higher temperatures resulting from a shift in Earth's orbit. As a result of this aridification, it became a largely impenetrable barrier to humans, with the remaining settlements mainly being concentrated around the numerous oases that dot the landscape. Little trade or commerce is known to have passed through the interior in subsequent periods, the only major exception being the Nile Valley. The Nile, however, was impassable at several Cataracts of the Nile, cataracts, making trade and contact by boat difficult.


Tichitt culture

In 4000 BCE, the start of sophisticated social structure (e.g., trade of cattle as valued assets) developed among herders amid the Pastoral Period of the Sahara. Saharan pastoral culture (e.g., fields of tumuli, lustrous stone rings, axes) was intricate. By 1800 BCE, Saharan pastoral culture expanded throughout the Saharan and Sahelian regions. The initial stages of sophisticated social structure among Saharan herders served as the segue for the development of sophisticated hierarchies found in African settlements, such as Dhar Tichitt. After migrating from the Central Sahara, Mande peoples established their civilization in the Tichitt region of the Western Sahara The Tichitt Tradition of eastern Mauritania dates from 2200 BCE to 200 BCE. Tichitt culture, at Dhar Néma, Dhar Tagant, Dhar Tichitt, and Dhar Walata, included a four-tiered hierarchal social structure, farming of cereals, metallurgy, numerous funerary tombs, and a rock art tradition At Dhar Tichitt and Dhar Walata, pearl millet may have also been independently tamed amid the Pastoral Neolithic, Neolithic. The Urban area, urban Tichitt Tradition may have been the earliest large-scale, Complex society, complexly organized society in
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 17 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Mauritania ...

West Africa
, and an early civilization of the Sahara, which may have served as the segue for state formation in West Africa. As areas where the Tichitt cultural tradition were present, Dhar Tichitt and Dhar Walata were occupied more frequently than Dhar Néma. Farming of crops (e.g., millet) may have been a feature of the Tichitt cultural tradition as early as 3rd millennium BCE in Dhar Tichitt. As part of a broader trend of iron metallurgy developed in the West African Sahel amid 1st millennium BCE, iron items (350 BCE – 100 CE) were found at Dhar Tagant, iron metalworking and/or items (800 BCE – 400 BCE) were found at Dia, Mali, Dia Shoma and Walaldé, and the iron remnants (760 BCE – 400 BCE) found at Bou Khzama and Djiganyai. The iron materials that were found are evidence of iron metalworking at Dhar Tagant. In the late period of the Tichitt Tradition at Dhar Néma, tamed pearl millet was used to temper the tuyeres of a oval-shaped low shaft furnace; this furnace was one out of 16 iron furnaces located on elevated ground. Iron metallurgy in Africa, Iron metallurgy may have developed before the second half of 1st millennium BCE, as indicated by pottery dated between 800 BCE and 200 BCE. At Dhar Walata and Dhar Tichitt, copper was also utilized. After its decline in Mauritania, the Tichitt Tradition spread to the Middle Niger region (e.g., Méma, Macina, Mali, Macina, Dia, Mali, Dia Shoma, Jenne Jeno) of Mali where it developed into and persisted as Faïta Facies ceramics between 1300 BCE and 400 BCE among rammed earth architecture and iron metallurgy (which had developed after 900 BCE). Thereafter, the Ghana Empire developed in the 1st millennium CE.


Phoenicians

The people of Phoenicia, who flourished from 1200 to 800 BCE, created a confederation of kingdoms across the entire Sahara to Egypt. They generally settled along the Mediterranean coast, as well as the Sahara, among the people of ancient Libya, who were the ancestors of people who speak Berber languages in North Africa and the Sahara today, including the Tuareg people, Tuareg of the central Sahara. The Phoenician alphabet seems to have been adopted by the ancient Libyans of north Africa, and Tifinagh is still used today by Berber-speaking Tuareg camel herders of the central Sahara. Sometime between 633 BCE and 530 BCE, Hanno the Navigator either established or reinforced Phoenician colonies in Western Sahara, but all ancient remains have vanished with virtually no trace.


Greeks

By 500 BCE, Ancient Greece, Greeks arrived in the desert. Greek traders spread along the eastern coast of the desert, establishing trading colonies along the
Red Sea The Red Sea ( ar, البحر الأحمر, translit=al-Baḥr al-ʾAḥmar; or ; Coptic Coptic may refer to: Afro-Asia * Copts, an ethnoreligious group mainly in the area of modern Egypt but also in Sudan and Libya * Coptic language, a North ...

Red Sea
. The Carthage, Carthaginians explored the Atlantic coast of the desert, but the turbulence of the waters and the lack of markets caused a lack of presence further south than modern Morocco. Centralized states thus surrounded the desert on the north and east; it remained outside the control of these states. Raids from the nomadic Berber people of the desert were of constant concern to those living on the edge of the desert.


Urban civilization

An urban civilization, the Garamantes, arose around 500 BCE in the heart of the Sahara, in a valley that is now called the Wadi al-Ajal in Fezzan, 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 (who were put to work extending the tunnels). The ancient Greeks and the Ancient Rome, Romans knew of the Garamantes and regarded them as uncivilized nomads. However, they traded with them, and a Roman bath has been found in the Garamantes' capital of Garama. Archaeology, Archaeologists have found eight major towns and many other important settlements in the Garamantes' territory. The Garamantes' civilization eventually collapsed after they had depleted available water in the aquifers and could no longer sustain the effort to extend the tunnels further into the mountains. Between the first century BCE and the fourth century CE, several Romans in Sub-Saharan Africa, Roman expeditions into the Sahara were conducted by groups of military and commercial units of Roman Empire, Romans.


Berbers

The Berber people occupied (and still occupy with Arabs) much of the Sahara. The Garamantes Berbers built a prosperous empire in the heart of the desert. The Tuareg nomads continue to inhabit and move across wide Sahara surfaces to the present day.


Islamic and Arabic expansion

The Byzantine Empire ruled the northern shores of the Sahara from the 5th to the 7th centuries. After the Muslim conquest of Arabia, specifically the Arabian peninsula, the Muslim conquest of North Africa began in the mid-7th to early 8th centuries and Islamic influence expanded rapidly on the Sahara. By the end of 641 all of Egypt was in Muslim hands. Trade across the desert intensified, and a significant slave trade crossed the desert. It has been estimated that from the 10th to 19th centuries some 6,000 to 7,000 slaves were transported north each year. The Beni Ḥassān and other nomadic Arab tribes dominated the Sanhaja Berber people, Berber tribes of the western Sahara after the Char Bouba war of the 17th century. As a result, Arabian culture and language came to dominate, and the Berber tribes underwent some Arabization.


Ottoman Turkish era

In the 16th century the northern fringe of the Sahara, such as coastal regencies in present-day Ottoman Algeria, Algeria and Tunisia, as well as some parts of present-day Libya, together with the semi-autonomous kingdom of Egypt, were occupied by the Ottoman Empire. From 1517 Egypt was a valued part of the Ottoman Empire, ownership of which provided the Ottomans with control over the Nile Valley, the east Mediterranean and North Africa. The benefit of the Ottoman Empire was the freedom of movement for citizens and goods. Traders exploited the Ottoman land routes to handle the spices, gold and silk from the East, manufactured goods from Europe, and the slave and gold traffic from Africa. Arabic continued as the local language and Islamic culture was much reinforced. The Sahel and southern Sahara regions were home to several independent states or to roaming Tuareg clans.


European colonialism

European colonialism in the Sahara began in the 19th century. July Monarchy, France conquered the regency of Algiers from the Ottomans in 1830, and French rule spread south from French Algeria and eastwards from French Senegal, Senegal into the upper Niger River, Niger to include present-day Algeria, Chad, Mali then French Sudan including
Timbuktu Timbuktu ( ; french: Tombouctou; tmh, label=Tuareg languages, Tuareg, script=Tfng, ⵜⵏⴱⴾⵜ, Tin Buqt; Koyra Chiini: ) is a city in Mali, situated north of the Niger River. The town is the capital of the Tombouctou Region, one of the e ...

Timbuktu
(1893), Mauritania, Morocco (1912), Niger, and Tunisia (1881). By the beginning of the 20th century, the trans-Saharan trade had clearly declined because goods were moved through more modern and efficient means, such as airplanes, rather than across the desert. The French took advantage of long-standing animosity between the Chaamba Arabs and the Tuareg. The newly raised ''Méhariste'' Méhariste, camel corps were originally recruited mainly from the Chaamba nomadic tribe. In 1902, the French penetrated Hoggar Mountains and defeated Kel Ahaggar, Ahaggar Tuareg in the battle of Tit, Tamanrasset, Tit. The French Colonial Empire was the dominant presence in the Sahara. It established regular air links from Toulouse (HQ of famed Aéropostale (aviation), Aéropostale), to Oran and over the Hoggar to Timbuktu and West to Bamako and Dakar, as well as trans-Sahara bus services run by La Compagnie Transsaharienne (est. 1927). A remarkable film shot by famous aviator Captain René Wauthier documents the first crossing by a large truck convoy from Algiers to Tchad, across the Sahara. Egypt, under Muhammad Ali of Egypt, Muhammad Ali and his successors, conquered Nubia in 1820–22, founded Khartoum in 1823, and conquered Darfur in 1874. Egypt, including the Sudan, became a British protectorate in 1882. Egypt and United Kingdom of Great Britain and Ireland, Britain lost control of the Sudan from 1882 to 1898 as a result of the Mahdist War. After its capture by British troops in 1898, the Sudan became an Anglo-Egyptian condominium (international law), condominium. Restoration (Spain), Spain captured present-day
Western Sahara Western Sahara ( '; ; ) is a disputed territory Controversy is a state of prolonged public dispute or debate, usually concerning a matter of conflicting opinion or point of view. The word was coined from the Latin ''controversia'', as a com ...

Western Sahara
after 1874, although Rio del Oro remained largely under Sahrawi people, Sahrawi influence. In 1912, Kingdom of Italy, Italy captured parts of what was to be named Ottoman Libya, Libya from the Ottomans. To promote the Roman Catholic religion in the desert, Pope Pius IX appointed a delegate Apostolic of the Sahara and the Sudan in 1868; later in the 19th century his jurisdiction was reorganized into the Vicariate Apostolic of Sahara.


Breakup of the empires and afterwards

Egypt became independent of Britain in 1936, although the Anglo-Egyptian treaty of 1936 allowed Britain to keep troops in Egypt and to maintain the British-Egyptian condominium in the Sudan. British military forces were withdrawn in 1954. Most of the Saharan states achieved independence after World War II: Libya in 1951; Morocco, Sudan, and Tunisia in 1956; Chad, Mali, Mauritania, and Niger in 1960; and Algeria in 1962. Spain withdrew from
Western Sahara Western Sahara ( '; ; ) is a disputed territory Controversy is a state of prolonged public dispute or debate, usually concerning a matter of conflicting opinion or point of view. The word was coined from the Latin ''controversia'', as a com ...

Western Sahara
in 1975, and it was partitioned between Mauritania and Morocco. Mauritania withdrew in 1979; Morocco continues to hold the territory (see Western Sahara conflict). Tuareg people in Mali Tuareg rebellions (disambiguation), rebelled several times during the 20th century before finally forcing the Malian armed forces to withdraw below the line demarcating Azawad from southern Mali during the Tuareg rebellion (2012), 2012 rebellion. Islamist rebels in the Sahara calling themselves al-Qaeda in the Islamic Maghreb have stepped up their violence in recent years. In the post–World War II era, several mining, mines and communities have developed to utilize the desert's natural resources. These include large deposits of petroleum, oil and natural gas in Algeria and Libya, and large deposits of phosphates in Morocco and Western Sahara. Libya's Great Man-Made River is the world's largest irrigation project. The project utilizes a pipeline system that pumps fossil water from the Nubian Sandstone Aquifer System to cities in the populous Libyan northern Mediterranean coast including Tripoli and Benghazi. A number of Trans-African Highway network, Trans-African highways have been proposed across the Sahara, including the Cairo–Dakar Highway along the Atlantic coast, the Trans-Sahara Highway from Algiers on the Mediterranean to Kano (city), Kano in Nigeria, the Tripoli – Cape Town Highway from Tripoli in Libya to N'Djamena in Chad, and the Cairo – Cape Town Highway which follows the Nile. Each of these highways is partially complete, with significant gaps and unpaved sections.


People, culture, and languages

The people of the Sahara are of various origins. Among them the Amazigh including the Tuareg people, Tuareg, various Arabized Amaziɣ groups such as the Hassaniya-speaking Sahrawis, whose populations include the Znaga, a tribe whose name is a remnant of the pre-historic Zenaga language. Other major groups of people include the: Toubou, Nubians, Zaghawa people, Zaghawa, Kanuri people, Kanuri, Hausa people, Hausa, Songhai people, Songhai, Beja people, Beja, and Fula people, Fula/Fulani (french: Peul; ff, Fulɓe). Arabic dialects are the most widely spoken languages in the Sahara. Arabic, Berber and its variants now regrouped under the term Amazigh (which includes the Guanche language spoken by the original Berber inhabitants of the Canary Islands) and Beja languages are part of the Afro-Asiatic or Hamito-Semitic family. Unlike neighboring
West Africa West Africa or Western Africa is the westernmost region of Africa. The United Nations defines Western Africa as the 17 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Mali, Mauritania ...

West Africa
and the central governments of the states that comprise the Sahara, the French language bears little relevance to inter-personal discourse and commerce within the region, its people retaining staunch ethnic and political affiliations with Tuareg and Berbers, Berber leaders and culture. The legacy of the French French North Africa, colonial era administration is primarily manifested in the territorial reorganization enacted by the French Third Republic, Third and French Fourth Republic, Fourth republics, which engendered artificial political divisions within a hitherto isolated and porous region. Diplomacy with local clients was conducted primarily in Arabic, which was the traditional language of bureaucratic affairs. Mediation of disputes and inter-agency communication was served by interpreters contracted by the French government, who, according to Keenan, "documented a space of intercultural mediation," contributing much to preserving the indigenous cultural identities in the region.Jeremy Keenan, ed. (2013). ''The Sahara: Past, Present and Future''. Routledge,


See also

* Arid Lands Information Network * List of deserts * List of deserts by area * Neolithic Subpluvial * Sahara Conservation Fund * Sahara Sea * Saharan explorers *Trans-Saharan slave trade


References


Bibliography

* * Republished with a new preface Columbia University Press, 1990. * * * * * *


External links


About Sahara subsurface hydrology
and planned usage of the aquifers] {{Authority control Sahara, Articles containing video clips Deserts and xeric shrublands Deserts of Africa Geography of North Africa Geography of the Arab world Palearctic realm Physiographic provinces