Where is the Sahara Desert located?

The Sahara Desert is the largest SANDY desert on our planet and is located in the northern part of the continent of Africa. It also ranks second as the largest desert in the world by area, behind the Antarctic Desert. The area of ​​the Sahara covers about 8.6 million km2 and partially occupies the territory of 10 states. From west to east its length is 4800 m, and from south to north its length ranges from 800 to 1200 meters. Moreover, the size of the desert is not constant; it grows annually by 6-10 km from south to north.

Sahara desert landscape

The landscape of the Sahara consists of 70% plains and 30% of the Tibesti and Ahaggar highlands, the stepped plateaus of Adrar-Iforas, Air, Ennedi, Tademait, etc., as well as cuesta ridges.

Sahara desert climate

The desert climate is divided into subtropical in the north and tropical in the south of the desert. In the northern part of the desert there are large temperature fluctuations, both average annual and average daily. In winter, temperatures in the mountains can drop to -18 degrees. Summer, on the other hand, is very hot. The soil can warm up to 70-80 degrees Celsius.

In the southern part of the desert, temperature fluctuations are slightly less, but also in winter, temperatures in the mountains can drop below zero degrees Celsius. Winter is milder and drier.

The desert is characterized by large temperature fluctuations at night and daytime. This figure is expressed by up to 30-40 degrees difference between night and day temperatures! Therefore, sometimes you can’t do without warm clothes there at night, as the temperature can drop below zero. Also in the desert there are often sandstorms, in which winds can reach up to 50 meters per second. Central parts of the desert may not see rain for years, and other parts may even experience heavy downpours. In other words, the Sahara Desert is full of surprises when it comes to weather.

The Sahara Desert is an amazing place. It is incredible how animals, plants, and people were able to adapt to life in this part of the earth, given the constant drought and heat.

1) The size of the desert is as big as half of Russia, or the whole of Brazil!
The Sahara Desert is the largest desert in the world, covering 30% of Africa. But this is half Russian Federation, or the entire area of ​​Brazil, which is the fifth largest country on Earth.

2) “A sea without water.” In Arabic, the Sahara is a desert, and some people called it the “Sea without Water” because once upon a time there were many rivers and lakes in its place.

3) Mars on Earth. Desert dunes move from a couple of centimeters to hundreds of meters per year, and the dunes themselves resemble the landscapes of Mars! Sometimes they reach a height of 300 meters!

4) There are fewer and fewer oases. Villages and towns usually appear near oases, but every year there are fewer and fewer oases.

5) The average temperature in the desert is about 40 degrees Celsius! The sand itself heats up to 80 degrees Celsius! But at night the temperature can drop to -15 degrees Celsius.

6) Over the past fifty years, storms have begun to appear more and more often, in some places their occurrence has increased forty times!

7) 3 million people live in the Sahara. However before people there was more, once upon a time, caravans of traders passed through the desert, carrying various riches. But crossing the entire desert took 1.5 years!

8) The roots of some plants are at a depth of 20 meters! In this way, plants try to get water for themselves in order to retain it for a long time and use it carefully.

9) There are about 4 thousand in the Sahara various types animals and plants.

10) Camels live without water for 14 days, and without food for as many as 30! They can smell moisture from 50 kilometers away, and drink one hundred liters of water at a time! And they don't sweat at all! Their humps are fat, thanks to which they can survive for a long time without food.

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Geography

20% of the earth's surface is desert. The idea that the desert is a place where there is a lot of sand and is always very hot does not correspond to reality. Most deserts are rocky, covered with flat gravel. With temperature, too, not everything is as is commonly believed. Very high daytime temperatures can drop below zero at night.

Temperate deserts occupy vast areas in the interior of Europe and Asia. From the Caspian Sea through Central Asia to the southern regions of the Gobi, they almost completely cover flat areas. The desert zone is located east of the Caspian Sea between 34° and 48° N. w. The total area of ​​the CIS deserts is 3 million km 2. The relief of deserts is predominantly flat. On the territory of the CIS countries, the largest deserts are the Karakum and Kyzylkum, whose area is 350 thousand and 300 thousand km, respectively.

In North America, deserts occupy intermountain depressions in the west of the continent.

Subtropical and tropical deserts are located in western India, Pakistan, Iran, in the central part of the Asia Minor peninsula,

In Africa there are deserts - in the north of the continent - the Sahara, in the southwest - the Namib.

In South America - in northern Chile and northwestern Argentina.

In Australia - the central and northern parts of the continent.

The largest desert in the world is the Sahara (7 million km), located in North Africa. The Gobi and Libyan deserts occupy 2 million km each. Of the semi-desert areas of the world, the largest is the South African Kalahari, its territory is about 1 million km.

Currently, the area of ​​all deserts is constantly increasing. The Sahara is increasing the fastest. Every year its southern border advances by almost 50 km.

Deserts arise where the quantity atmospheric precipitation is less than 80 mm per year. The main reserves of water are located in the soil at considerable depth.

Summer is hot with average temperatures in the warmest months up to 30-40° and with a maximum of 58" (Arabia). The soil heats up to +70" C. Large daily and annual amplitudes of air and soil temperatures are characteristic. In summer, temperatures close to 0° are often observed at night, and in winter frosts are observed even in the Sahara.

Most deserts are characterized by strong winds(over 10 m/sec), often having a constant direction (Afghan, Shamsin).

The climate of the deserts of Central Asia is sharply continental and dry. Annual precipitation is less than 200 mm. Evaporation is 7-10 times higher than the annual amount of precipitation. Number sunny days reaches 200 per year. Relative humidity in the summer months during the daytime is 10% or less, at night - up to 25%. In winter, northeastern winds predominate in deserts, and in summer, northwestern winds.

In summer, the average air temperature in the north of the zone reaches +25...+29° C, in the south - up to +32° C. Maximum daytime temperatures can approach +45...+50° C. The soil heats up to +70° C .

Winter in the desert is warmer than in the semi-desert zone, but at times air temperatures can drop to - 25... - 30 ° C. The average January temperature in the north of the desert zone is 12 ° C, in the south - about zero. The height of the snow cover is no more than 10 cm. Snow is not found in the south. Falls in spring most of annual precipitation.

There are almost no purely mechanical obstacles to movement across rocky deserts; all difficulties are related to the climate. Movement in sandy deserts is really difficult. Sand is still not asphalt, but after our off-road experience you will successfully cope with this problem. I advise you to pay attention to your shoes.

Despite such a harsh climate, even the Sahara is inhabited, although sparsely. Vegetation does not form a continuous cover, in some places it is completely absent. There are many ephemeral plants, perfectly adapted to desert conditions. Their seeds germinate almost a day after rain falls. Perennial xerophytes are widely developed, in which a dense network of long roots extracts moisture from great depths. Some plants are adapted to storing large reserves of water in their bodies - cacti, milkweed, etc.

The desert fauna is characterized by relatively large ungulates and rodents: antelopes, wild horses, kulans, ground squirrels, gerbils, jerboas, etc. There are quite a lot of reptiles (lizards, snakes and turtles), insects (diptera, hymenoptera) and arachnids (phalanxes, tarantulas) in the desert , Scorpios).

I did not have to eat pasture in the desert. IN African deserts An oasis with a grove of date palms can be an salvation. The Taureg, who have lived in the Sahara for thousands of years, have learned to make do with a handful of dried dates a day, while walking up to 50 km under the sun. I don’t know how they manage to do this, probably, if you train for 500 years in a row, then you will be able to do the same.

Dates do not grow in Central Asia. But, if you believe the Bible, then the righteous, having retired to the desert, ate grasshoppers (locusts). So practice catching grasshoppers or carefully think through each desert crossing.

Life in the desert concentrates near water sources - rivers, canals, springs, artesian wells, wells, filling wells or in mining sites. The most likely encounter is with shepherds. It is possible to find the camp using fresh prints car tires on the ground, in the tracks of ungulates and their droppings. Sheep grazing is usually carried out at a distance not exceeding a daily journey from a water source (well, well).

In the desert, death is most likely from dehydration, heat and sunstroke, and rarely from bites of poisonous snakes and arachnids.

Long-term survival in summer in the absence of significant supplies of fresh water is impossible!

The desert climate is characterized by hot summers and cold winters. The average annual temperature varies from +16°C in the northern part to +20°C in the south of the zone. Summer temperatures in the western and eastern parts do not differ significantly, amounting to 26-30°C. [...]

Synonym: desert climate with cold winters.[...]

The division of climates into 9 main groups listed below; these 9 groups contain 30 types. Main groups: warm climates without a dry period (equatorial), warm climates with a dry period (tropical), monsoon climates, warm temperate climates without a frosty period (subtropical), temperate climates with a cold season, hot desert climates, cold desert climates, cold climates with temperate summers, cold climates without warm seasons. For climate groups, numerical characteristics of temperature and precipitation regimes are indicated. Certain climate types are named geographically according to the areas where they are most pronounced (Bengal climate, Norwegian climate, etc.).[...]

A. z. Irrigated agriculture is typical. A soils are formed in arid climates of deserts, semi-deserts, dry steppes and desertified savannas, where the evaporation of moisture significantly exceeds its supply with precipitation. A-i climate - a dry climate in which the amount of evaporation greatly exceeds the amount of precipitation falling during the year; characterized by clear skies, high level condensation, preventing the formation of clouds, large daily temperature fluctuations. Characteristic of deserts and semi-deserts.[...]

Our observations of benthos suggest that plant communities might be more diverse in stable environments. The climate of the Sonoran Desert is distinctly unstable with alternating two wet and two dry periods per year and with high variability in total precipitation in different years. However, some parts of the Soyora Desert are quite rich in species (see Figure 3-10). It turns out that in this desert the instability of natural conditions does not so much limit diversity as it turns into an aspect of the environment to which plants respond with niche differentiation (see Fig. 3-7) and, as a consequence, species diversity. The vegetation of the Middle East has been greatly disturbed by humans, subject to fires, logging, and heavy and varied grazing pressure from sheep, goats, cattle, and camels. But the structure of open forests and shrubs, altered by grazing, is nevertheless very rich in species that have adapted to these disturbances, especially species of annual and bulbous plants. The fact that warm-climate plant communities in Sonora, the Middle East, and elsewhere are so rich in species despite drought and environmental instability suggests that temperature, rather than moisture or stability, is the major factor that determines the species diversity of vascular plants. One more observation about terrestrial plant communities can be mentioned, namely, broad-leaved deciduous forests are, on average, noticeably richer in species than evergreen coniferous forests under similar environmental conditions. The type of dominant species, which determine the nature of leaf litter and the chemical composition of soil organic matter, significantly influences the species diversity of terrestrial plant communities.[...]

The influence of greater or less air humidity on an animal organism can be expressed in some changes in metabolism and the acquisition in the process of evolution of a number of adaptations to climate characteristics. A dry climate is more favorable for the body. The healing effect of mountain, steppe and semi-desert air is partly explained by its low humidity. The dry climate has a particularly beneficial effect on the wool of sheep (merino sheep breeding); on the strength, energy and performance of horses (for example, Eastern, Arabian, Akhal-Teke). Over the centuries, animals of dry climates (desert and semi-desert zones) have developed exceptional adaptation to these conditions (camel, antelope, some breeds of sheep, donkeys, etc.). Countries with high rainfall and high air humidity are more suitable for the development of dairy farming (forage crops and pasture plants grow well here). However, excessive air humidity has a detrimental effect on the health of animals, as well as on some types of their productivity. Animals living in low, damp places are more often exposed to pulmonary, helminthic and some other diseases. Low temperature at high air humidity causes catarrhs respiratory tract and intestines, especially in representatives of breeds unaccustomed to such a climate (for example, in steppe sheep when they are transferred to damp areas). In addition, in humid climates, the coat and quality of sheep's wool often deteriorates.[...]

Evaporative geochemical barriers / are areas where an increase in concentration chemical elements occurs as a result of evaporation processes. They are most common in regions with arid climates (deserts, dry steppes and savannas), but are also found in black soil steppes and even in the taiga and tundra. However, in this case, during the rainy period, the soil is washed out and the abnormal concentrations of chemical elements on the evaporation barriers may disappear.[...]

Anthropogenic activity significantly influences climatic factors, changing their regimes. The destruction of forests and other vegetation, the creation of large artificial reservoirs on former land areas increases the reflection of energy, and dust pollution, for example, of snow and ice, on the contrary, increases absorption, which leads to their intensive melting. Thus, the mesoclimate can change dramatically under human influence: it is clear that the climate of North Africa in the distant past, when it was a huge oasis, was significantly different from the climate of the Sahara Desert today.

Today we will continue our acquaintance with the natural areas of our planet. The theme of our excursion will be the places where camels slowly walk, and the wind and the scorching sun are the undivided masters. It's about about deserts.

Here, among the sands and heat, there is its own plant and animal world, people live and work. What are features this zone?

Where are the deserts

Deserts are areas with a continental climate and sparse vegetation. Such places can be found on all continents, with the exception of Europe. They extend across the temperate zone of the Northern Hemisphere and the subtropics and tropics of both hemispheres.

The largest deserts are the Sahara, Victoria, Karakum, Atacama, Nazca, and the Gobi Desert.

Russian deserts are located in the east of Kalmykia and in the south of the Astrakhan region.

Climate Features

The main features of the climate of this zone are high daytime temperatures and extreme dry air. During the day, the water vapor content in the atmosphere is 5–20%, which is several times lower than normal. The driest deserts are the deserts of South America. The main reason - almost complete absence of rain. In some places they occur no more than once every few months or even several years. Sometimes heavy rainfall falls on the dried, heated ground, but instantly evaporates without having time to saturate the soil.

It is often observed in these places "dry rain" Ordinary raindrops fall from the forming rain clouds, but when they collide with heated air, they evaporate without ever reaching the ground. Precipitation in the form of snow is very rare here. Only in some cases does the snow cover reach a thickness of more than 10 cm.

In this natural zone, daytime temperatures can rise to +50°C, while at night they can drop to 0°C. In the northern regions, the thermometer can drop to minus 40 °C. For these reasons, the climate of deserts is considered continental.

Often residents and tourists witness amazing optical phenomena - mirages. At the same time, tired travelers see in the distance oases with life-giving moisture, wells with drinking water…. But all this is an optical illusion caused by the refraction of sunlight in the heated layers of the atmosphere. As these objects approach, they move away from the observer. You can get rid of these optical illusions by starting a fire. The smoke creeping along the ground quickly dispels this obsessive vision.

Relief features

Most of the desert surface is covered with sand and the strong wind becomes the “culprit” of sandstorms. At the same time, they rise above the surface of the earth huge masses of sand. The sandy curtain erases the horizon line and obscures the bright sunlight. Hot air mixed with dust makes breathing difficult.

After 2-3 days the sand settles. And the renewed surface of the desert appears before the eyes of those around you. In some places, rocky areas are exposed, or, conversely, new dunes appear against the backdrop of frozen sand waves. The relief of deserts contains small hills, alternating with plains, ancient river valleys and depressions from once existing lakes.

Characteristic of deserts light soil color, thanks to the lime accumulated in it. Soil surface areas containing an excess amount of iron oxides have a reddish color. The fertile layer of soil - humus is almost absent. In addition to sandy deserts, there are zones with rocky, clayey and saline soil.

Vegetable world

In most deserts precipitation occurs in spring and winter. Moistened soil is literally transformed. Within a few days it becomes colored with a wide variety of colors. The duration of flowering depends on the amount of precipitation and the soil of the area. Local residents and tourists come to admire the bright, beautiful flower carpet.

The heat and lack of moisture soon return the desert to its normal appearance, where only the most resilient plants can grow.

Tree trunks are most often severely curved. The most common plant in this area is saxaul bushes. They grow in groups, forming small groves. However, do not look for shade under their crowns. Instead of the usual foliage, the branches are covered with small scales.

How does this shrub survive in such arid soils? Nature has provided them with powerful roots that go into the ground to a depth of 15 meters. And another desert plant - camel-thorn its roots can reach moisture from a depth of up to 30 meters. The spines or very small leaves of desert plants allow them to use moisture very economically through evaporation.

Among the various cacti growing in the desert is Echinocactus Gruzoni. The juice of this one and a half meter plant perfectly quenches thirst.

In the South African desert there is a very amazing flower - fenestraria. Only a few of its leaves are visible on the surface of the earth, but its roots are like a tiny laboratory. This is where the nutrients are produced, thanks to which this plant even blooms underground.

One can only be amazed at the adaptability of plants to extreme desert conditions.

Animal world

In the heat of the day, the desert truly seems devoid of all life. Only occasionally do we see a nimble lizard, and some bug hurries about its business. But With the onset of cool night, the desert comes to life. Small and fairly large animals crawl out of their hiding places to replenish food supplies.

How do animals escape the heat? Some bury themselves in the sand. Already at a depth of 30 cm, the temperature is 40°C lower than on the ground. This is exactly how the kangaroo jumper behaves, which manages not to crawl out of its underground shelter for several days. Its burrows contain reserves of grains that absorb moisture from the air. They quench his hunger and thirst.

Close “canine relatives” of jackals and coyotes from the heat Frequent breathing and sticking out your tongue saves you.

The saliva evaporating from the tongue cools these curious animals quite well. African foxes and hedgehogs emit excess heat with their large ears.

Long legs Ostriches and camels help escape from the hot sand, since they are high enough above the ground, and there the temperature is lower.

In general, the camel is more adapted to life in the desert than other animals. Thanks to its wide, calloused feet, it can walk on hot sand without getting burned or falling through. And its thick and dense coat prevents moisture evaporation. The fat accumulated in the humps is converted into water if necessary. Although he can easily live without water for more than two weeks. And these giants are not picky when it comes to food - they chew camel thorn, and twigs of saxaul or acacia are already a luxury in a camel’s diet.

Desert insects “thought of” reflecting the scorching rays of the sun the surface of your body.

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Winter in deserts, although warmer than in the semi-desert zone, it is still unusually cold for these low latitudes. The average January temperature in the north of the zone is about -12°, in the south – close to 0°, the average absolute minimum air temperature is –35-20°. Lake Balkhash and the Aral Sea are frozen in winter; Freeze-up lasts 2.5-3.0 months at the mouths of the Amu Darya and Syrdarya rivers. Snow cover about 10 cm high lies for 100 days in the north of the zone and 20-30 days in the southwest. Little snow and short duration of snow cover make it possible to graze livestock in deserts in winter. The non-grazing period for sheep in the deserts of Kazakhstan lasts only 30-60 days, and in the Central Asian deserts it is practically absent, except for the relatively rare days with ice and snowstorms here.

Spring- a season of the year that refutes the usual ideas about the desert. At this time, there is a rapid increase in air temperature, unusual for other zones. In the Kzyl-Orda region, the transition of the average daily air temperature through 10° occurs on April 11, and already a decade later or a little later, the transition of the average daily air temperature through 15° occurs in the same place. May in the zone in its temperature conditions (16-20°) resembles the height of summer middle zone Russia - July. Moderate positive air temperatures in spring are combined with the annual maximum precipitation, which occurs in May in the north of the zone and April in the south.

Atmospheric precipitation, together with winter reserves of soil moisture, is sufficient for short-term but lush development of vegetation. It is at this time that there is an outbreak of vegetation of ephemerals and ephemeroids, especially characteristic of sandy and foothill loess deserts. The animal world is becoming very active. For some desert inhabitants, spring is the only period of the year active life. So, for example, the steppe tortoise is active only from March to May; after the ephemerals burn out, it buries itself in the ground and lies there until next spring. The sand squirrel leads a similar lifestyle.

It is significant that the lambing of the goitered gazelle and domestic Karakul sheep coincides with the development of ephemeral-ephemeroid vegetation. At the same time, the growth of Karakul lamb is very intense in the first month. “The meaning of this phenomenon is that a lamb in the desert must be prepared for the early dry summer, for eating dry, hard grasses in the summer, and must have time to gain a sufficient supply of fat.”

Summer in the deserts of the temperate zone it is even hotter, sunny and dry than in the semi-desert zone. The average temperature in July is about 25-29°, on some days the air temperature in the shade rises above 40°, and the surface of the bare soil heats up to 70°. The hot period in the zone is characterized by stability and duration: the number of days with an average daily air temperature above 20° in the north is 90, in the south – 140. The entire territory of the zone in summer serves as an arena for the formation of local continental tropical air, which differs not only high temperatures, but also very low humidity and high dust levels.

The sweltering heat is aggravated by the insignificant amount of precipitation, the amount of which quickly decreases in a southerly direction. During all three summer months, 30 mm of precipitation falls in Irgiz, 19 mm in Kazalinsk, and 11 mm in Turkestan. For comparison, we point out that Moscow, with its moderately warm summers, receives 192 mm of precipitation over the same period. Due to an acute lack of moisture, ephemerals and ephemeroids disappear from the grass cover even before the beginning of summer, and the most undemanding shrub wormwood and solyanka, which are in a state of semi-dormancy, stop growing. At the beginning of summer, cotton budding occurs, in July it begins to flower, and at the end of August - beginning of September, ripening occurs.

Autumn the first half is very reminiscent of summer: in September, as in previous months, hot and dry cloudless weather prevails, favorable for the ripening and harvesting of cotton and fruit crops. In the southern half of the zone, the transition of the average daily temperature through 15° occurs around October 1. In the second half of autumn, cloudiness increases, the amount of precipitation increases, which, at low air temperatures, creates conditions for repeated vegetation (greening) of many plants. The first frosts in most of the zone appear in October.

Literature.

1. Milkov F.N. Natural areas USSR / F.N. Milkov. - M.: Mysl, 1977. - 296 p.