Where is the Sahara desert on the map. Sahara desert in tunisia. Environmental problems of the Sahara desert

Most of North Africa is occupied by the Sahara desert. This is the greatest wilderness the globe(the area is about 8 million km 2, larger than Australia), stretching from the Red Sea for 6000 km and from the Mediterranean to the Sudanese plains for 2000 km. southern border The Sahara is drawn from the plains of Sudan along a line from the mouth of Senegal north of the basins of the Middle Niger and Lake Chad to Khartoum and further to the Red Sea coast at the northern edge of the Ethiopian highlands. In the north, the region faces mediterranean sea and at the foot of the Atlas Mountains. Under common name The Sahara unites a number of tropical deserts of various types (Nubian, Libyan, Igidi, Shesh, etc.). On its territory are the southern parts of the Maghreb countries, Libya, Egypt, Western Sahara (Saharan Arab Democratic Republic), Mauritania, northern Mali, the Republic of Chad, Niger, Sudan.

Many belong to the Sahara climate records: the highest amounts of solar radiation and air temperature, the highest values ​​of evaporation in the world, the most acute shortage of moisture. The main feature of nature is the extreme degree of aridity, which determines almost all the main natural features. Of the factors causing aridity, the main one is the position in tropical zone in the zone of circulation of the trade wind type, where air currents of the northeast direction with downward vertical movement predominate. The orographic structure of the territory also plays a role. The Sahara is located within the ancient African Platform, mostly on plate structures. The relief is dominated by plains of different hypsometric levels (mainly uplands and plateaus), which form a system of shallow basins, which exacerbates the features of the continental climate.

The tropical climate of the Sahara desert is different a high degree continentality and extra-aridity. Within a narrow strip of the Mediterranean coast, the climate is subtropical, but also dry. In the extreme west, the climatic conditions of tropical coastal (“cold”, “wet”) deserts are presented.

Most of the territory throughout the year is occupied by dry and hot continental tropical air, which enters in winter mainly from outside or is formed in the region itself in the high area. In summer it is of local or Mediterranean origin. Mediterranean air coming from the area high pressure, has the properties of a trade wind, carries an inversion and does not give precipitation. The dryness of the air and the absence of clouds bring insolation to almost 100%. In the east of the region, the annual values ​​of total radiation reach the highest values ​​on Earth (220 kcal/cm2). July isotherm (32°C) delineating the main part of the desert. Evaporation is up to 5000 mm and more, and precipitation in most of the territory is less than 50 mm / year, which indicates an acute moisture deficit. It rains occasionally in the north in winter (the action of Mediterranean cyclones), in the rest of the territory - in summer, when here in the region low pressure air masses penetrate and a trade wind front is formed. The slopes of the mountains and the outskirts of the desert are somewhat better irrigated, but even here there is a shortage of moisture.

The Precambrian base of the platform is mostly hidden under limestone, sandstone, sand and clay. Formation plains 300-500 meters high dominate. The central parts of internal depressions and foredeeps are occupied by lower accumulative plains. Where the foundation comes to the surface, basement plains and revived mountains (the highlands of Ahaggar and Tibesti, Etbay, etc.) have formed. In the highlands, as a result of the development of volcanism processes, there are sections of lava plateaus and ancient ones: the highest point of the Sahara - Mt. Emi-Kusi in the Tibesti highlands (3415 meters) is an extinct volcano. Arid climate determines the predominance of physical weathering processes and the dominance of the eolian relief. As a result of physical weathering processes in conditions of a sharp change in temperature during the day and wind activity in areas with different lithological composition rocks different types of deserts are formed. Rocky and gravelly (khamads) prevail on outcrops of hard rocks, pebble and sandy-pebble (regs and serirs) on ancient alluvium. Sandy deserts (ergs) with accumulative eolian relief occupy about 20% of the region's area in the lower parts of the basins. There are areas of clay deserts and solonchaks (sebkhas and shotts) in place of dried lakes. The plateaus and highlands of the Sahara are covered with a dense network of dry channels - oueds, which are relics of past pluvial epochs. The heritage of these humid climatic conditions is also represented by cuesta ridges (tassili) on monoclinal limestones and sandstones, bordering uplifts. Forms of eolian corrosion are formed on rocky outcrops, and accumulation and deflation are formed on sands. There are cliffs fancifully worked by the wind, honeycomb sands, dunes, dunes, etc.

Due to the extreme aridity of the Sahara desert climate, there is almost no surface water. The only major permanent watercourse is the transit river Nile, fed outside the desert. Ueda and most of the relict lake basins are filled with water only during short showers. In these conditions great importance acquire groundwater, which in some places lie close to the surface. In such places, natural and artificial oases arise. The artesian basins of the Sahara desert are the largest in the world, but many of them have saline waters.

The vegetation cover in the region under conditions of the most acute moisture deficit is extremely poorly developed, very sparse, and practically absent on vast expanses of moving sands, stony placers or solonchaks. The species composition of the flora is poor: only a little more than 1200 species have been found on a vast territory.

Perennial xerophytic grasses and shrubs, annual ephemera dominate. Grasses are predominantly from the genus Aristida, shrubs - Saharan gorse, juzgun, retam, ephedra, acacia, camel thorn, etc. All of them have certain adaptations to life in conditions of low water, strong daytime heat and temperature changes. Altitudinal zonality is observed in the high uplands. There are deserted savannahs and mountain steppes. In the valleys of the oueds from the north they enter mediterranean views, and from the south - Sudanese flora.

The soil cover in the Sahara is discontinuous, in many places it is practically absent. Soils are poorly developed, but contain a large number of nutrient minerals, that is, potentially fertile.

The animal world is poor in species, but relatively rich in individuals. The fauna is characteristic of the desert regions of the Holarctic and is close to the Arabian one. About 60 species of mammals, many reptiles, terrestrial insects and birds live here. All of them are adapted to life in arid conditions, to high daytime temperatures and large diurnal temperature amplitudes. The fact that in the past the climate of the Sahara was humid is evidenced by some species of animals in mountainous areas that have a limited range, cut off from their main habitats (for example, crocodiles in the relict reservoirs of the Ahaggar highlands). Ancient frescoes on the Tassilin-Ajer plateau depict giraffes, elephants, hippos, which, apparently, lived in these areas already in the memory of people.

The Sahara is well endowed with some species natural resources. The huge amount of heat and the abundance of various mineral salts in the soils make this region potentially favorable for agricultural use. The limiting factor is . Indeed, where there is - in oases, people get rich harvests of tropical crops. The main cultivated plant of the oases is the date palm, but various fruit, grain and industrial crops are also grown, such as cotton and tobacco. The main population of the Sahara desert is concentrated in oases.

A special type of oasis (and the largest in the world) is the Nile Valley with a multi-million population and a diverse modern economy. Agriculture This region has centuries-old traditions and a high culture of water and land use.

Some tribes of the Saharan peoples still lead a nomadic lifestyle and are engaged in breeding camels and sheep. They wander from well to well and concentrate in areas of oases.

A special place is occupied by the wealth of the subsoil of the region. Large deposits of gas have been discovered here, there are reserves of manganese and uranium ores, some non-ferrous ores. Since ancient times, soda has been mined in the Sahara. The settlements that arose in the places of mining can be considered oases of a new type. The use of all natural resources is hampered by the lack of water. Wide application for water supply they have artesian waters, especially fresh ones. However, irrigation and watering in hot climates are associated with the danger of soil salinization and require a very careful thoughtful approach.

The economic development of the Sahara desert in recent decades has led to the aggravation of many environmental problems in the region. The already meager natural vegetation is degrading, the number of wild animals is declining (many species are on the verge of extinction), soils are being destroyed and salinized, water sources are being polluted and depleted. On the borders of the Sahara, the processes of desertification are actively developing, both natural (due to the drying up of the climate) and anthropogenic. In some places in the south of the region, the deserts move at a speed of 10-50 km per year, absorbing the territories of the savannas. The implementation of programs to combat desertification and restore disturbed lands in this region with such a vulnerable nature faces great difficulties, the main of which is the lack of funds to implement these projects.

28.04.2014

Great Sahara Desert is located in North Africa and partially or completely covers the territory of almost eleven countries. This largest desert in the world covers an area of ​​​​more than 9,000,000 square meters. km, quite comparable with the area of ​​the USA. It stretches 1600 km wide and about 5000 km long from east to west. It is said that a thousand years ago the climate in the desert was more humid. The fact is that in the distant past, the territory of the Sahara underwent various atmospheric changes, which led to a change in climatic conditions. The desert divides the African continent into two parts - North and Sub-Saharan Africa. By reviewing the following interesting facts, you will learn more about this desert.

The Sahara Desert is the second largest desert in the world (after Antactis) and the largest hot desert planets.

It covers almost all parts of North Africa. It stretches from the Red Sea, including parts of the Mediterranean coast, to the outskirts of the Atlantic Ocean. In the southern region, its border is the semi-arid Sahel savannah region (Sahel), separating the desert from Sub-Saharan Africa. However, the boundaries of the desert are not clearly defined; moreover, over the past thousand years they have undergone significant changes.

The Sahara passes through the following countries: Algeria, Chad, Egypt, Libya, Morocco, Mauritania, Mali, Niger, Sudan, Tunisia, Western Sahara

The history of the desert goes back at least 3 million years.

The climate of the Sahara is combined: in the north it is subtropical, and in the south - tropical.

The relief is quite diverse, but in general it is a plateau lying at an altitude of 400-500 m above sea level. There are underground rivers that sometimes flow to the surface, forming oases. Vegetation develops well in such natural oases. The soil of such regions of the Sahara is very fertile, so where irrigation is possible, an excellent crop grows.

Part of the desert is occupied sand dunes that reach a height of 180 meters .

The central region is more elevated above sea level compared to the rest of its regions. The central plateau stretches for 1600 km from the northwest to the southeast. Its height varies from 600 to 750 m, some peaks reach the level of 1800 m and even 3400 m. high points- Emi Koussi peaks with a height of 3415 m, Tahat - 3003 m, the Tibetsi massif and the Ahaggar highlands.

It may seem strange, but in winter time snow caps lie on the mountain peaks. In the eastern part of the Sahara - the Libyan desert - the climate is the driest, so there are very few oases. In this part, sandy areas with large dunes are concentrated, the height of which reaches 122 meters or more.

The climate of the Sahara Desert is very hot and dry. During the day it is very hot here, and at night it is cool.

The Sahara receives only 20 cm of precipitation per year. It is for this reason that a very small number of people live here, only 2 million people.

Previously, the desert was a fertile land where elephants, giraffes and other animals grazed. Gradually, it became more and more arid, and the fertile landscape turned into the barren region as we know it today.

The central part of the Sahara is exceptionally dry, with little or no vegetation. In places where moisture accumulates, meadows, desert shrubs, trees and tall shrubs are sometimes found here.

During the last ice age, the desert was larger than it is now, extending south beyond its current borders.

Climatic conditions here are considered the toughest in the world. The prevailing northeasterly winds often cause sandstorms and dust devils micro-tornadoes.

Arabic is the most widely spoken language in the Sahara, from the Atlantic to the Red Sea.

The Sahara is divided into several regions: Western Sahara, Central Ahaggar Highlands, Tibesti Mountains, Aïr Mountains (a region of desert mountains and high plateaus), the Tenere Desert and the Libyan Desert (the driest region).

The Nile Valley and the mountainous regions of the Nubian Desert east of the Nile are geographically part of the Sahara Desert. However the waters of the Nile turned this territory of Egypt from a barren desert into a fertile agricultural area.

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Sahara Desert

(North Africa)

A truly endless sea of ​​sand, stone and clay scorched by the sun, revived only by rare green spots of oases and a single river - this is what the Sahara is. The gigantic scale of this very big desert the world is simply amazing. Its territory occupies almost eight million square kilometers - it is larger than Australia and only slightly smaller than Brazil. Its hot expanses stretch for five thousand kilometers from the Atlantic to the Red Sea.

Nowhere else on Earth is there such a huge waterless space. There are places in the interior of the Sahara where it doesn't rain for years. So, in the oasis of In-Salah, in the heart of the desert, for eleven years, from 1903 to 1913, it rained only once - in 1910, and only eight millimeters of rain fell.

These days, the Sahara is not so difficult to access. From the city of Algiers on a good highway to the desert can be reached in one day. Through the picturesque gorge of El Kantara - "Gateway to the Sahara" - the traveler finds himself in places that by their landscape do not at all resemble the "sandy sea" he expected with golden waves of dunes. To the left and right of the road, which runs along a rocky and clay plain, small rocks rise, to which the wind and sand have given the intricate outlines of fairy-tale castles and towers.

Sandy deserts - ergs - occupy less than a quarter of the entire territory of the Sahara, the rest falls on the share of rocky plains, as well as clayey areas cracked from the scorching heat and salt-white depressions-salt marshes, generating deceptive mirages in the unsteady haze of heated air.

In general, the Sahara is a vast plateau, a table, the flat character of which is broken only by the depressions of the Nile and Niger valleys and Lake Chad. On this plain, only in three places do truly high, albeit small in area, mountain ranges rise. These are the Ahaggar and Tibesti highlands and the Darfur plateau, rising more than three kilometers above sea level.

The mountainous, gorge-cut, absolutely dry landscapes of Ahaggar are often compared to lunar landscapes. But under the natural rocky canopies, archaeologists have discovered here a whole art gallery of the Stone Age. The rock paintings of ancient people depicted elephants and hippos, crocodiles and giraffes, rivers with floating boats and people harvesting ... All this suggests that the climate of the Sahara used to be more humid, and savannas were once located in most of the current desert.

Now they are found only on the slopes of the Tibesti highlands and the flat high plains of Darfur, where for a month or two a year, while it rains, real rivers even flow through the gorges, and abundant springs all year round feed the oases.

In the rest of the Sahara, precipitation is less than two hundred and fifty millimeters per year. Geographers call such areas arid regions. They are unsuitable for agriculture, and herds of sheep and camels can only be driven over them in search of scarce food.

Here are the hottest places on our planet. For example, in Libya there are areas where the heat reaches fifty-eight degrees! And in some areas of Ethiopia, even mean annual temperature does not fall below plus thirty-five.

The sun governs all life in the Sahara. Its radiation, taking into account rare cloudiness, low air humidity and lack of vegetation, reaches very high values. The daily temperatures here are characterized by large jumps. The difference between day and night temperatures reaches thirty degrees! Sometimes frosts occur at night in February, and on Ahaggar or Tibesti the temperature can drop to minus eighteen degrees.

Of all atmospheric phenomena The most difficult thing in the Sahara is for the traveler to endure prolonged storms. The desert wind, hot and dry, causes hardship even when it is transparent, but it is even more difficult for travelers when it carries dust or fine grains of sand. Dust storms are more common than sandstorms. The Sahara is perhaps the dustiest place on earth. These storms look from afar like fires quickly covering everything around, clouds of smoke from which rise high into the sky. With furious force they rush through the plains and mountains, blowing dust from the destroyed rocks on their way.

Storms in the Sahara have extraordinary strength. The wind speed sometimes reaches fifty meters per second (remember that thirty meters per second is already a hurricane!). Caravaneers say that sometimes heavy camel saddles are carried away by the wind for two hundred meters, and stones, the size of a chicken egg, roll along the ground like peas.

Quite often, tornadoes occur when the very heated air from the earth heated by the sun rapidly rises, capturing fine dust and carrying it high into the sky. Therefore, such whirlwinds are visible from afar, which, as a rule, allows the rider to save his life by avoiding a meeting with the "desert genie", as the Bedouins call the tornado. A gray column rises into the air to the very clouds. Pilots met dust devils sometimes at a height of one and a half kilometers. It happens that the wind carries Saharan dust across the Mediterranean Sea to Southern Europe.

On the vast Saharan plains, the wind almost always blows. It is estimated that there are only six calm days in the desert for a hundred days. Especially notorious are the hot winds of the Northern Sahara, which can destroy the entire crop in the oasis in a few hours. These winds - sirocco - blow more often in early summer. In Egypt, such a wind is called khamsin (literally - "fifty"), since it usually blows for fifty days after spring equinox. During his almost two-month rampage, the window glass, not closed by the shutters, becomes dull - this is how grains of sand carried by the wind scratch it.

And when there is calm in the Sahara and the air is filled with dust, there is a "dry fog" known to all travelers. At the same time, visibility completely disappears, and the sun seems to be a dull spot and does not give a shadow. Even wild animals lose their bearings at such moments. They say that there was a case when, during the "dry fog", usually very shy gazelles calmly walked in a caravan, walking between people and camels.

Sahara likes to be reminded of herself unexpectedly. It happens that the caravan sets off when nothing foretells bad weather. The air is still clean and calm, but some strange heaviness is already spreading in it. Gradually, the sky on the horizon begins to turn pink, then takes on a purple hue. It is somewhere far away that the wind has picked up and drives the red sands of the desert towards the caravan. Soon, the cloudy sun barely breaks through the rapidly rushing sandy clouds. It becomes difficult to breathe, it seems that the sand has displaced the air and filled everything around. hurricane wind rushes at speeds up to hundreds of kilometers per hour. Sand burns, chokes, knocks down. Such a storm sometimes lasts a week, and woe to those whom it caught on the way.

But if the weather is calm in the Sahara and the sky is not covered with wind-blown dust, it is difficult to find a more beautiful sight than a sunset in the desert. Perhaps only the aurora borealis makes a greater impression on the traveler. The sky in the rays of the setting sun each time strikes with a new combination of shades - it is both blood-red and pink-pearl, imperceptibly merging with pale blue. All this is piled up on the horizon in several floors, it burns and sparkles, growing into some kind of bizarre, fabulous forms, and then gradually fades away. Then, almost instantly, an absolutely black night sets in, the darkness of which even the bright southern stars cannot dispel.

Of course, the most desirable and most picturesque places in the Sahara are the oases.

The Algerian oasis of El Ouedd lies in the golden yellow sands of the Great East Erg. FROM outside world it is connected by an asphalt highway, but it only appears as such on the map. In many places, the wide roadbed is thoroughly covered with sand. A good two-thirds of the telegraph poles are buried in it, and teams of workers with shovels and whisks are constantly raking drifts, first in one area, then in another. After all, the wind blows here all year round. And even a weak breeze, tearing off the tops of sandy dune hills, steadily moves sandy waves from place to place. With a strong wind, traffic on the roads of the desert sometimes stops completely, and not for one day.

Like all oases of the Sahara, El Ouedd is surrounded by a palm grove. Date palms are the basis of life for the locals. In other oases, in order to give them water to drink, irrigation systems are arranged, but in El Ouedd it is easier. In the dry bed of the river flowing through the oasis, they dig deep funnel holes and plant palm trees in them. Water always flows under the rusdom at a depth of five or six meters, so that the roots of palm trees planted in this way easily reach the level of the underground stream, and they do not need irrigation.

In each funnel grows from fifty to one hundred palms. The sinkholes are arranged in rows along the channel, and all of them are threatened common enemy- sand. To prevent the slopes from sliding, the edges of the funnels are strengthened with wattle from palm branches, but the sand still seeps down. You have to take it all year round on donkeys or carry it on yourself in baskets. In the summer, in the heat, this hard work can only be done at night, by the light of torches or in the radiance full moon. Water wells are also dug in these funnels. It is enough for drinking and for watering gardens. Camel droppings serve as fertilizer.

Dates and camel milk are the main food of fellah farmers. A valuable nutmeg variety of dates is sold and even exported to Europe.

The capital of the Algerian Sahara - the oasis of Ouargla - differs from other oases in that it has ... a real lake. This tiny town in the middle of the desert has a reservoir of four hundred hectares, huge by local standards. It was formed from water discharged from palm plantations after irrigation. Water is always supplied to the fields and date groves in excess, otherwise evaporation will lead to the accumulation of salts in the soil. Excess water, along with salts, is discharged into a depression next to the oasis. This is how artificial lakes appear in the Sahara.

True, most of them are not as large as in Ouargla, and do not withstand a deadly struggle with sand and sun. Most often, these are just swampy depressions, the surface of which is covered with a dense, transparent, like glass, layer of salt.

But oases in the Sahara are rare, and one has to get from one "island of life" to another along the endless roads of the desert, overcoming the heat of the sun, hot wind, dust and ... the temptation to turn off the road. Such a temptation often arises among travelers both on ancient caravan trails and on modern paved highways in these inhospitable lands.

When the desired outlines of an oasis appear on the horizon in front of a traveler exhausted by a long journey, the Arab guide only shakes his head negatively. He knows that there are still tens of kilometers to the oasis under scorching sun, and what the traveler sees "with his own eyes" is just a mirage.

This optical illusion sometimes misleads even experienced people. Experienced travelers who have passed through the sands on more than one expeditionary route and have studied the desert for more than one year have also become victims of mirages. When you see palm groves and a lake, white clay houses and a mosque with a high minaret at a short distance, it is hard to believe that in reality they are several hundred kilometers away. Experienced caravan guides sometimes fell under the power of a mirage. One day, sixty people and ninety camels died in the desert, following a mirage that carried them sixty kilometers away from the well.

AT old times travelers, to make sure, a mirage in front of them or reality, kindled a fire. If even a small breeze blew in the desert, then the smoke creeping along the ground quickly dispersed the mirage. For many caravan routes, maps have been drawn up, which indicate places where mirages are often found. These maps even mark what exactly is seen in one place or another: wells, oases, palm groves, mountain ranges, and so on.

And yet, in our time, when two modern highways ran through the great desert from north to south, when multi-colored autocaravans of the Paris-Dakar rally rush through it every year, and artesian wells drilled along the roads allow, in case of anything, to walk to the nearest source of water, the Sahara gradually passes to be that fatal place that European travelers feared more than the Arctic snows and the Amazonian jungle.

Increasingly, inquisitive tourists, fed up with beach idleness and contemplation of the ruins of Carthage and other picturesque ruins, go by car or on a camel into the depths of this unique region of the planet to inhale a sip of the night wind on the slopes of Ahaggar, hear the rustle of palm crowns in the green coolness of the oasis, see the graceful run gazelles and admire the colors of the Sahara sunsets. And next to their caravan, the mysterious guardians of the peace of this hot, but beautiful land, dusty-gray, whirled by the wind, "desert genies" are running along the roadside with a quiet rustle.