Tropical desert definition. Where are the tropical deserts located and which ones are worth seeing? Patagonian desert region

Unbearable heat during the day, very cold at night. There is only dried earth, sand or cracked stones around. Not a single green tree nearby. Instead of trees there are dry trunks or “swaying” bushes. How and what does the desert live on? More precisely, how do plants and animals survive in these harsh desert conditions?

There are areas in nature where there is little or no vegetation and very few animals. Such natural areas are called deserts. They are found on all continents of the globe and occupy about 11% of the land surface (about 16.5 million sq. km).

A prerequisite for the formation of a desert on the surface of the earth is the uneven distribution of heat and moisture. Deserts form where there is little rainfall and dry winds prevail. Many are located nearby or are already surrounded by mountains, which prevent precipitation.

The desert is characterized by:

• - Aridity. The amount of precipitation per year is approximately 100-200 mm, and in some places it does not happen for decades. Often, even these small precipitations, evaporating, do not have time to reach the surface of the earth. And those precious drops that fall into the soil will replenish groundwater reserves;
• - Winds arising from excessive heating and associated air flows that reach 15 - 20 m/s or more;
• - Temperature, which depends on where the desert is located.

Desert climate

The climate in Putin is influenced by geographical location. There can be either a warm or dry climate. When the air is dry, it practically does not protect the surface from solar radiation. During the day the air warms up to + 50 °C, and at night it quickly cools down. During the day, the sun's rays, without lingering in the air, quickly reach the surface and heat it. Due to the lack of water, there is no heat transfer, which is why it is so hot during the day. And at night it’s cold for the same reason - lack of moisture. There is no water in the soil, therefore there are no clouds to retain heat. If daily temperature fluctuations in the desert of the tropical zone are 30-40 ° C, then in the temperate zone it is 20 ° C. The latter are characterized by hot summers and cold winters (up to - 50 ° C with a light cover of snow).

Desert flora and fauna

Few plants and animals can survive in such difficult climatic conditions. They are characterized by:

• - Long roots to extract moisture in deep layers of soil;
• - Small, hard leaves, and in some they are replaced by needles. Everything for less moisture evaporation.

Desert inhabitants vary depending on the location of the desert. Wormwood, saxaul, solyanka, brassica, and juzgun are characteristic of the temperate desert; succulents (cacti) are added to the subtropical and tropical deserts of Africa and Arabia. Lots of light, poor soil, lack of a lot of water - that's all cacti need. Cacti have adapted perfectly: the spines do not allow unnecessary waste of moisture, the developed root system collects morning dew and night soil moisture.

The deserts of North America and Australia are much richer and more diverse (low-growing acacia, eucalyptus, quinoa, twig, etc.). In oases and large river valleys in the temperate zone of Asia, trees grow: jida, willow, elm, turango poplar; in subtropical and tropical - evergreen palm, oleander. And this small list is very valuable in the desert. The plants serve as food for camels and for warmth on cold nights.

The fauna is not picky about food and water, and the color is close to the color of the earth's surface. Characteristic for many night life, during the day they sleep.

The most famous and widespread is the camel, the only one that can eat camel thorn and survive for a long time without water. All thanks to its hump, which contains a supply of nutrients.

Reptiles also live: lizards, agamas, and monitor lizards. The length of the latter can reach one and a half meters. A variety of insects, arachnids, and mammals (jerboas, gerbils) make up the desert fauna.

What is the secret of scorpion survival in deserts?

Scorpions are representatives of the arachnid species. And this is surprising, since they are not at all like spiders. Scorpions prefer dry, hot deserts, but even some species have adapted to tropical rainforests. These arachnids also live in Russia. For example, the yellow scorpion can be found in the forests of Dagestan and Chechnya. In the Lower Volga region, the motley scorpion lives in wastelands and dried desert areas, and the Italian and Crimean scorpion is found on the Black Sea coasts.

Since the respiratory system of these arachnids is poorly adapted to a dry and hot climate, this feature forces the insect to take refuge from the heat in various gorges, cracks, under stones, and bury itself in sand or soil. There they find at least some moisture. That is why scorpions are nocturnal animals: during the day they sleep, waiting out the heat, and at night they are good-natured. Desert scorpions can do practically without water, feeding on various insects, and large individuals can eat a lizard or a small rodent. Cases have been recorded where a scorpion survives after starvation for 0.5 to 1.5 years. In the desert, scorpions mainly obtain moisture from food, but sometimes suck it from wet sand.

For any animal and plant in the desert, the main difficulty is the lack of moisture, the lack of water. It is this feature that gives the world such bizarre forms of life. Some people have adapted not to drink, but to limit themselves to moisture obtained from food. Some people often change their location in search of water. Some people move closer to the water during the dry season. Some people produce metabolic water during their metabolism. Somehow, desert animals have found a way to survive in the harsh desert climate.

In addition, see documentary BBC from the Forces of Nature series, the film explains in detail the features of desert branding

Geographical features of deserts

Most of the world's deserts were formed on geological platforms and occupy the oldest land areas. Deserts in Asia, Africa and Australia are usually located at altitudes from 200-600 m above sea level, in Central Africa and North America– at an altitude of 1 thousand m above sea level.

Deserts are one of the landscapes of the Earth that arose as naturally as all others, thanks primarily to the peculiar distribution of heat and moisture over the earth’s surface and the associated development of organic life and the formation of biogeocenotic systems. A desert is a specific geographical phenomenon, a landscape that lives its own special life, has its own patterns, and, during development or degradation, has its own inherent features and forms of change.

Speaking about the desert as a planetary and naturally occurring phenomenon, this concept should not mean something monotonous and of the same type. Most deserts are surrounded by mountains or, more often, bordered by mountains. In some places, deserts are located next to young high mountain systems, in others - with ancient, heavily destroyed mountains. The first include the Karakum and Kyzylkum deserts Central Asia– Alashan and Ordos, South American deserts; The latter should include Northern Sahara.

Mountains and deserts are areas of formation of liquid runoff, which comes to the plain in the form of transit rivers and small, “blind” mouths. Underground and sub-channel flow, which feeds their groundwater, is also of great importance for deserts. Mountains are areas from which destruction products are removed, for which deserts serve as a place of accumulation. Rivers supply a lot of loose material to the plain. Here it is sorted, ground into even smaller particles and lines the surface of deserts. As a result of centuries-old work of rivers, the plains are covered with a multi-meter layer of alluvial sediments. The rivers of the sewage areas carry a huge mass of blown and debris material into the World Ocean. Therefore, the deserts of drainage areas are characterized by an insignificant distribution of ancient alluvial and lacustrine sediments (Sahara, etc.). On the contrary, drainage-free regions (Turanian Lowland, Iranian Plateau, etc.) are distinguished by thick thicknesses of sediments.

Surface deposits of deserts are unique. They owe this geological structure territory and natural processes. According to M.P. Petrov (1973), surface deposits of deserts are of the same type everywhere. This is “rocky and gravelly eluvium on Tertiary and Cretaceous conglomerates, sandstones and marls that make up the structural plains; pebbly, sandy or loamy-clayey proluvial sediments of piedmont plains; sandy strata of ancient deltas and lake depressions and, finally, aeolian sands” (Petrov, 1973). Deserts are characterized by some similar natural processes that are prerequisites for morphogenesis: erosion, water accumulation, blowing and aeolian accumulation of sand masses. It should be noted that similarities between deserts are found in a large number of features. The differences are less noticeable and are limited to a few examples, quite sharply.

The differences are most related to geographical location deserts in various thermal zones of the Earth: tropical, subtropical, temperate. The first two zones contain the deserts of North and South America, the Near and Middle East, India, and Australia. Among them are continental and oceanic deserts. In the latter, the climate is moderated by the proximity of the ocean, which is why the differences between heat and water balances, precipitation and evaporation are not similar to the corresponding values ​​that characterize continental deserts. However, for oceanic deserts, the ocean currents washing the continents - warm and cold - are of great importance. The warm current saturates the air masses coming from the ocean with moisture, and they bring precipitation to the coast. The cold current, on the contrary, intercepts the moisture of air masses, and they arrive on the mainland dry, increasing the aridity of the coasts. Oceanic deserts are located off the western coasts of Africa and South America.

Continental deserts are located in the temperate zone of Asia and North America. They lie inside continents (deserts Central Asia) and are characterized by arid and extra-arid conditions, a sharp discrepancy between the thermal regime and precipitation, high evaporation, and contrasts in summer and winter temperatures. The differences in the nature of deserts are also influenced by their altitude.

Mountain deserts, like those located in intermountain depressions, are usually characterized by increased climate aridity. The variety of similarities and differences between deserts is primarily due to their location at different latitudes of both hemispheres, in the hot and temperate zones of the Earth. In this regard, the Sahara may have more similarities with the Australian desert and more differences with the Karakum and Kyzylkum in Central Asia. Equally, deserts formed in the mountains may have a number of natural anomalies among themselves, but there are even more differences with the deserts of the plains.

Differences occur in average and extreme temperatures during the same season of the year, in the timing of precipitation (for example, the eastern hemisphere of Central Asia receives more precipitation in the summer from monsoon winds, and the deserts of Central Asia and Kazakhstan - in the spring). Dry riverbeds are a prerequisite for the nature of deserts, but the factors of their occurrence are different. The sparseness of the cover largely determines the low humus content in desert soils. This is also facilitated by dry air in the summer, which prevents active microbiological activity (in winter, fairly low temperatures slow down these processes).

Patterns of desert formation

The “mechanism” of the formation and development of deserts is subject, first of all, to the uneven distribution of heat and moisture on Earth, the zonality of the geographical envelope of our planet. The zonal distribution of temperatures and atmospheric pressure determines the specifics of the winds and the general circulation of the atmosphere. Above the equator, where the greatest heating of land and water occurs, ascending air movements dominate.

An area of ​​calms and weak variable winds forms here. Warm air rising above the equator, cooling somewhat, loses a large number of moisture falling in the form of tropical showers. Then, in the upper atmosphere, the air flows north and south, towards the tropics. These air currents are called anti-trade winds. Under the influence of the rotation of the earth in the northern hemisphere, the antitrade winds bend to the right, in the southern hemisphere - to the left.

Approximately above latitudes of 30-40° C (near the subtropics), their deviation angle is about 90° C, and they begin to move along parallels. At these latitudes, air masses descend to the heated surface, where they heat up even more, and move away from the critical saturation point. Due to the fact that in the tropics there is high atmospheric pressure all year round, and at the equator, on the contrary, it is low, a constant movement of air masses (trade winds) occurs at the surface of the earth from the subtropics to the equator. Under the influence of the same deflecting influence of the Earth, trade winds move from northeast to southwest in the northern hemisphere, and from southeast to northwest in the southern hemisphere.

Trade winds cover only the lower layer of the troposphere - 1.5-2.5 km. The trade winds that dominate in equatorial-tropical latitudes determine the stable stratification of the atmosphere and prevent vertical movements and the associated development of clouds and precipitation. Therefore, cloudiness in these belts is very insignificant, and the influx of solar radiation is the greatest. As a result, the air here is extremely dry (relative humidity in the summer months averages about 30%) and extremely high summer temperatures. average temperature air on continents in the tropical zone in summer exceeds 30-35° C; here the highest air temperature on the globe occurs - plus 58 ° C. The average annual amplitude of air temperature is about 20 ° C, and the daily temperature can reach 50 ° C; the soil surface sometimes exceeds 80 ° C.

Precipitation occurs very rarely, in the form of showers. In subtropical latitudes (between 30 and 45° C northern and southern latitudes), the amount of total radiation decreases, and cyclonic activity contributes to moistening and precipitation, confined mainly to the cold period of the year. However, sedentary depressions of thermal origin develop on the continents, causing severe aridity. Here, the average temperature in the summer months is 30° C or more, and the maximum can reach 50° C. In subtropical latitudes, intermountain depressions are the driest, where the annual precipitation does not exceed 100-200 mm.

In the temperate zone, conditions for the formation of deserts occur in inland regions such as Central Asia, where precipitation falls less than 200 mm. Due to the fact that Central Asia is fenced off from cyclones and monsoons by mountain uplifts, a pressure depression forms here in the summer. The air is very dry, high temperature (up to 40° C or more) and very dusty. Rarely penetrating here with cyclones, air masses from the oceans and the Arctic quickly warm up and dry out.

Thus, the nature of the general circulation of the atmosphere is determined by planetary features, and local geographical conditions create a unique climatic situation that forms a desert zone to the north and south of the equator, between 15 and 45 ° C latitude. Added to this is the influence of cold currents of tropical latitudes (Peruvian, Bengal, Western Australian, Canary and Californian). By creating a temperature inversion, cool, moisture-laden maritime air masses and easterly persistent wind pressure highs lead to the formation of coastal cool and foggy deserts with even less rainfall.

If land covered the entire surface of the planet and there were no oceans or high mountain rises, the desert belt would be continuous and its boundaries would exactly coincide with a certain parallel. But since land occupies less than 1/3 of the area of ​​the globe, the distribution of deserts and their size depend on the configuration, size and structure of the surface of the continents. For example, Asian deserts spread far to the north - up to 48° N latitude. In the southern hemisphere, due to the vast water expanses of the oceans, the total area of ​​the continents' deserts is very limited, and their distribution is more localized. Thus, the emergence, development and geographical distribution of deserts on the globe are determined by the following factors: high values ​​of radiation and radiation, low amounts of precipitation or their complete absence. The latter, in turn, is determined by the latitude of the area, the conditions of the general circulation of the atmosphere, the peculiarities of the orographic structure of the land, and the continental or oceanic position of the area.

Aridity of the territory

In terms of the degree of aridity - aridity, many territories are not the same. This gave grounds to divide arid lands into extra-arid, arid and semi-arid, or extremely arid, arid and semi-arid. At the same time, areas where the probability of constant droughts is 75-100% are considered extra-arid, arid – 50-75% and semi-arid – 20-40%. The latter include savannas, pampas, pashtos, and prairies, where organic life occurs in a natural environment in which, except for some years, drought is not a determining condition for development. Rare droughts with a probability of 10-15% are also characteristic of the steppe zone. Consequently, the arid zone does not include all areas of land where droughts occur, but only those where organic life is largely under their influence for a long time.

According to M.P. Petrov (1975), deserts include territories with an extremely arid climate. Precipitation falls less than 250 mm per year, evaporation exceeds precipitation many times, agriculture is impossible without artificial irrigation, the movement of water-soluble salts predominates and their concentration on the surface, there is little organic matter in the soil.

The desert is characterized by high summer temperatures, low annual precipitation - usually from 100 to 200 mm, lack of surface runoff, often the predominance of sandy substrate and the large role of aeolian processes, groundwater salinity and migration of water-soluble salts in the soil, uneven amount of precipitation, which determines the structure , yield and feeding capacity of desert plants. One of the features of the distribution of deserts is the island, local nature of their geographical location. On no continent do desert lands form a continuous strip, like the Arctic, tundra, taiga or tropical zones. This is due to the presence within the desert zone of large mountain structures with their greatest peaks and significant expanses of water. In this respect, deserts do not completely obey the law of zonation.

In the northern hemisphere, the desert areas of the African continent lie between 15° C and 30° N latitude, where the world's largest desert, the Sahara, is located. In the southern hemisphere, they are located between 6 and 33° S, covering the Kalahari, Namib and Karoo deserts, as well as the desert areas of Somalia and Ethiopia. In North America, deserts are confined to the southwestern part of the continent between 22 and 24° N, where the Sonoran, Mojave, Gila, and other deserts are located.

Large areas of the Great Basin and the Chihuahuan Desert are quite close in nature to the conditions of the arid steppe. In South America, deserts, located between 5 and 30° S, form an elongated strip (more than 3 thousand km) along the western, Pacific coast of the continent. Here the Sechura, Pampa del Tamarugal, Atacama deserts stretch from north to south, and beyond mountain ranges Patagonian. The deserts of Asia are located between 15 and 48-50° N and include such large deserts, like Rub al-Khali, Greater Nefud, Al-Hasa on the Arabian Peninsula, Dasht-e-Kevir, Dasht-e-Lut, Dashti-Margot, Registan, Haran in Iran and Afghanistan; Karakum in Turkmenistan, Kyzylkum in Uzbekistan, Muyunkum in Kazakhstan; Thar in India and Thal in Pakistan; Gobi in Mongolia and China; Taklamakan, Alashan, Beishan, Tsaidasi in China. Deserts in Australia occupy a vast area between 20 and 34° N latitude. and are represented by the Great Victoria, Simpson, Gibson and Great Sandy deserts.

According to Meigl, the total area of ​​arid territories is 48,810 thousand square meters. km, that is, they occupy 33.6% of the earth's land, of which extra-arid accounts for 4%, arid - 15 and semi-arid - 14.6%. The area of ​​typical deserts, excluding semi-deserts, is about 28 million square meters. km, that is, about 19% of the earth's land area.

According to Shants (1958), the area of ​​arid territories, classified according to the nature of vegetation cover, is 46,749 thousand square meters. km, that is, about 32% of the earth's land area. At the same time, the share of typical deserts (extra-arid and arid) falls on about 40 million square meters. km, and the share of semi-arid lands is only 7044 thousand square meters. km per year, arid (21.4 million sq. km) - with precipitation from 50 to 150 mm and semi-arid (21.0 million sq. km) - with precipitation from 150 to 200 mm.

In 1977, UNESCO compiled a unified new picture on a scale of 1: 25,000,000 in order to clarify and establish the boundaries of the world's arid regions. Four bioclimatic zones are highlighted on the map.

Extra-arid zone. Precipitation less than 100 mm; deprived of vegetation cover, excluding ephemeral plants and shrubs along the beds of watercourses. Agriculture and animal husbandry (except in oases) is impossible. This zone is a pronounced desert with possible droughts for one or several years in a row.

Arid zone. Precipitation 100-200 mm. Sparse, sparse vegetation, represented by perennial and annual succulents. Rain-fed agriculture is impossible. Nomadic cattle breeding zone.

Semi-arid zone. Precipitation 200-400 mm. Shrub communities with intermittent herbaceous cover. Area of ​​cultivation of rain-fed agricultural crops (“dry” farming) and livestock raising.

Zone of insufficient moisture (subhumid). Precipitation 400-800 mm. Includes some tropical savannas, Mediterranean communities such as maquis and chaparral, and black soil steppes. Zone of traditional rain-fed farming. To conduct highly productive agriculture, irrigation is necessary.

According to this map, the area of ​​arid territories is about 48 million square meters. km, which is equal to 1/3 of the entire land surface, where moisture is the decisive factor determining the biological productivity of arid lands and the living conditions of the population.

Desert classification

In arid territories, despite their apparent monotony, there is not at least 10-20 square meters. km of area, within which natural conditions would be exactly the same. Even if the topography is the same, the soils are different; if the soil is the same type, then the water regime is not the same; if there is a single water regime, then different vegetation, etc.

Due to the fact that the natural conditions of vast desert territories depend on a whole complex of interrelated factors, the classification of desert types and their zoning is a complex matter. There is not yet a unified and satisfactory from all points of view classification of desert territories, compiled taking into account all their geographical diversity.

There are many works in Soviet and foreign literature devoted to the classification of desert types. Unfortunately, in almost all of them there is no uniform approach to solving this issue. Some of them base their classification on climatic indicators, others on soil, others on floristic composition, others on lithoedaphic conditions (i.e. the nature of the soil and conditions for vegetation growing on them), etc. Rarely do any researchers base their classification on from a complex of characteristics of desert nature. Meanwhile, based on a generalization of the components of nature, it is possible to correctly identify the ecological features of the region and quite reasonably evaluate its specific natural conditions and natural resources from an economic point of view.

M.P. Petrov in his book “Deserts of the Globe” (1973) proposes ten lithoedaphic types for the deserts of the world on a multi-stage classification:

* sandy on loose sediments of ancient alluvial plains;

* sand-pebble and pebble on gypsum tertiary and lilac structural plateaus and piedmont plains;

* crushed stones, gypsum on tertiary plateaus;

* gravelly on foothill plains;

* rocky in low mountains and small hills;

* loamy on low-carbonate cover loams;

* loess on piedmont plains;

* clayey ones in low mountains, composed of salt-bearing marls and clays of various ages;

* solonchaks in saline depressions and along sea coasts.

Various classifications of types of arid territories of the globe and individual continents are also available in foreign literature. Most of them are compiled on the basis of climate indicators. There are relatively few classifications for other elements of the natural environment (relief, vegetation, wildlife, soils, etc.).

Desertification and nature conservation

Behind last years Alarming signals are heard from different parts of the globe about the increasing advance of desert into human-inhabited territories. For example, according to the UN, in North America alone, the desert annually robs people of about 100 thousand hectares of usable land. The most likely causes of this rather dangerous phenomenon are considered to be unfavorable weather conditions, destruction of vegetation, irrational environmental management, mechanization of agriculture, and transport without compensation for damage caused to nature. In connection with the intensification of desertification processes, some scientists talk about the possibility of an aggravation of the food crisis.

According to UNESCO, over the past 50 years, an area of ​​just under half of South America has been turned into barren deserts. This happened as a result of excessive grazing of pastures, predatory deforestation, unsystematic farming, construction of roads and other engineering structures. The rapid growth of population and technology also leads to intensifying desertification processes in some areas of the world.

There are many different factors leading to desertification in arid regions of the globe. However, among them there are common ones that play a special role in intensifying desertification processes. These include:

extermination of vegetation cover and destruction of soil cover during industrial and irrigation construction;

degradation of vegetation cover due to overgrazing;

destruction of trees and shrubs as a result of fuel procurement;

deflation and soil erosion due to intensive rainfed agriculture;

secondary salinization and waterlogging of soils under irrigated farming conditions;

destruction of the landscape in mining areas due to industrial waste, discharge of waste and drainage water.

Among the natural processes leading to desertification, the most dangerous are:

climatic – an increase in aridity, a decrease in moisture reserves caused by changes in macro- and microclimate;

hydrogeological – precipitation becomes irregular, groundwater recharge becomes episodic;

morphodynamic – geomorphological processes become more active (erosion, deflation, etc.);

soil – drying out of soils and their salinization;

phytogenic – degradation of soil cover;

zoogenic - reduction in the population and number of animals.

The fight against desertification processes is carried out in the following directions:

early identification of desertification processes in order to prevent and eliminate them, focusing on the formation of conditions for rational environmental management;

creation of protective forest strips along the edges of oases, field boundaries and along canals;

creation of forests and green “umbrellas” from local species - psamophytes in the depths of deserts to protect livestock from strong winds, scorching rays of the sun and strengthen the food supply;

restoration of vegetation cover in areas of open-pit mining, along the construction of an irrigation network, roads, pipelines and all places where it has been destroyed;

consolidation and afforestation of moving sands in order to protect against sand drifts and blowing out of irrigated lands, canals, settlements, railways and highways, oil and gas pipelines, industrial enterprises.

The main lever for successfully solving this global problem is international cooperation in the field of nature conservation and combating desertification. The life of the Earth and life on Earth largely depends on how timely and urgently the tasks of monitoring and managing natural processes are solved.

The problem of combating adverse events observed in the arid zone has existed for a long time. It is generally accepted that of the 45 identified causes of desertification, 87% are due to irrational human use of water, land, vegetation, wildlife and energy, and only 13% are due to natural processes.

Nature conservation is a very broad concept. It includes not only measures to protect specific areas of the desert or individual species of animals and plants. In modern conditions, this concept also includes measures to develop rational methods of environmental management, restoration of ecosystems destroyed by humans, forecasting physical and geographical processes during the development of new territories, and the creation of controlled natural systems.

firstly because its plant and animal world unique. Preserving the desert intact means leaving its indigenous inhabitants outside of economic progress, and the national economy without many, including unique, types of raw materials and fuel.

Secondly, because the desert itself is wealth, in addition to what is hidden in its depths or in the fertility of irrigated land.

Rich in various natural resources, the desert is very attractive, especially in early spring, when its short-lived plants bloom, and in late autumn, when cold rains and wind pour almost everywhere in our country, and there are warm sunny days in the desert. The desert is attractive not only for geologists and archaeologists, but also for tourists. It is also healing, its dry air, long warm period, medicinal mud and hot mineral springs make it possible to treat kidney diseases, rheumatism, nervous and many other diseases.

The desert and its inhabitants

Deserts belong to the arid zone. In summer the desert is extremely hot and there is very little rainfall. Because of this, there is little moisture there. Air temperature in the shade is 40-45 0 C, and the sand heats up to 70 0 WITH.

Usually the desert is covered with sand. Its surface is made up of dunes - sand waves that move slowly

Among the hot dunes, they are very rarely found " paradises", shady palm trees and some clean cool water - "Oases".

Desert animals include mammals, reptiles and birds. All of them are adapted to live in its climate.

Camel 1. Thick coat (protects against overheating, maintaining body temperature). 2 Fat reserves in the humps (helps to go without water for a long time)

3. Rough digestive system (camel eats thorns).

5. 4. Narrow foot (helps you move easily on the sand and not get burned). 5.Large nostrils (help cool the air). 6.Filters in the nose (protect from sand).

6 . Jerboa .

Has a long tail. To escape the heat, he leads a twilight lifestyle

7. Dancing lizard Membranous lizard.

This small lizard often dances to lower its temperature. During intense heat, hides in the sand

8. African pygmy viper

What is a desert without snakes? This small viper (25 cm) hides from the sun in the sand. Only the eyes remain visible. She can wait like this for many days until her victim approaches her.

9. Birds also live in deserts: desert sparrows, larks, nightjars, and predators.

10. Lamb vulture. This bird has learned to break skeletons. She climbs to a height and throws bones onto flat stones so that they break. And then it eats the bone marrow, which contains a lot of water.

11. Plants live in any ecosystem. Desert inhabitants: saxaul, camel thorn, seline. They have adapted to life in the desert

They acquired long roots, turned the leaves into thorns or covered them with wax, and stored water in thick stems. This is such an amazing living world in the desert. Over millions of years, all its inhabitants have learned to survive in its climate and obtain water for themselves.

Thank you for your attention

Secondary comprehensive multidisciplinary school No. 44 named after. V. Kudzoeva

"The Desert and Its Inhabitants"

2015

Despite the fact that its very name “desert” comes from words such as “empty”, “emptiness”, this amazing natural object filled with diverse life. The desert is very diverse: in addition to the sand dunes that our eyes usually draw, there are saline, rocky, clayey, and also snowy deserts of Antarctica and the Arctic. Taking into account snow deserts, this natural zone accounts for one fifth of the entire surface of the Earth!

Geographical object. The meaning of deserts

The main distinguishing feature of the desert is drought. Desert topography is very diverse: island mountains and complex highlands, small hills and stratified plains, lake depressions and dried out centuries-old river valleys. On the formation of desert relief big influence the wind is exerting.

People use deserts as pastures for livestock and areas for growing some crops. Plants for feeding livestock develop in the desert thanks to the horizon of condensed moisture in the soil, and desert oases, flooded with sun and fed with water, are exclusively good place for growing cotton, melons, grapes, peach and apricot trees. Of course, only small desert areas are suitable for human activity.

Characteristics of deserts

Deserts are located either next to mountains or almost on the border with them. High mountains prevent the movement of cyclones, and most of the precipitation they bring falls in the mountains or foothill valleys on one side, and on the other side - where the deserts lie - only small remnants of rain reach. The water that manages to reach the desert soil flows through surface and underground watercourses, collecting in springs and forming oases.

Deserts are characterized by various amazing phenomena that are not found in any other natural zone. For example, when there is no wind in the desert, tiny grains of dust rise into the air, forming the so-called “dry fog.” Sandy deserts can “sing”: the movement of large layers of sand generates a high and loud slightly metallic sound (“singing sands”). Deserts are also known for their mirages and terrible sandstorms.

Natural areas and types of deserts

Depending on the natural areas and type of surface, there are the following types of deserts:

• Sand and sand-crushed stone. They are distinguished by great diversity: from chains of dunes devoid of any vegetation to areas covered with shrubs and grass. Traveling through the sandy desert is extremely difficult. Sands do not occupy the largest part of deserts. For example: the sands of the Sahara make up 10% of its territory.

• Rocky (hamads), gypsum, gravelly and gravelly-pebble. They are combined into one group according to a characteristic feature - a rough, hard surface. This type of desert is most common in Globe(Saharan hamadas occupy 70% of its territory). Succulents and lichens grow in tropical rocky deserts.

• Salt marshes. In them, the concentration of salts prevails over other elements. Salt deserts can be covered with a hard, cracked crust of salt or a salt bog that can completely “suck in” a large animal and even a person.

• Clayey. Covered with a smooth clay layer stretching for many kilometers. They are characterized by low mobility and low water properties (the surface layers absorb moisture, preventing it from passing deeper, and quickly dry out during the heat).

Desert climate

Deserts occupy the following climatic zones:

• temperate (Northern Hemisphere)
• subtropical (both hemispheres of the Earth);
• tropical (both hemispheres);
• polar (ice deserts).

Deserts have a continental climate (very hot summers and cold winters). Precipitation falls extremely rarely: from once a month to once every few years and only in the form of showers, because... small precipitation does not reach the ground, evaporating while still in the air.

Daily temperature in a given climatic zone varies greatly: from +50 o C during the day to 0 o C at night (tropics and subtropics) and to -40 o C (northern deserts). Desert air is particularly dry: from 5 to 20% during the day and from 20 to 60% at night.

The largest deserts in the world

Sahara or Queen of the Desert- the largest desert in the world (among hot deserts), the territory of which occupies over 9,000,000 km 2. Located in North Africa, it is famous for its mirages, which occur here on average 150 thousand per year.

Arabian desert(2,330,000 km 2). It is located on the territory of the Arabian Peninsula, also covering part of the land of Egypt, Iraq, Syria, and Jordan. One of the most capricious deserts in the world, known for particularly sharp fluctuations in daily temperature, strong winds and dust storms. From Botswana and Namibia to South Africa it extends over more than 600,000 km 2 Kalahari, constantly increasing its territory due to alluvium.

Gobi(more than 1,200,000 km 2). It is located in the territories of Mongolia and China and is the largest desert in Asia. Almost the entire desert territory is occupied by clay and rocky soils. In the south of Central Asia lie Karakum(“Black Sands”), occupying an area of ​​350,000 km 2.

Victoria Desert- occupies almost half the territory of the Australian continent (over 640,000 km 2). Famous for the Reds sand dunes, as well as a combination of sandy and rocky areas. Also located in Australia Great Sandy Desert(400,000 km 2).

Two South American deserts are very noteworthy: Atacama(140,000 km 2), which is considered the driest place on the planet, and Salar de Uyuni(more than 10,000 km 2) is the largest salt desert in the world, whose salt reserves amount to more than 10 billion tons.

Finally, the absolute champion in terms of territory occupied among all the world’s deserts is Ice desert Antarctica(about 14,000,000 km 2).

The desert may seem like a lifeless area only at first glance. In fact, it is inhabited by unusual representatives of the animal and flora who managed to adapt to difficult climatic conditions. The desert natural zone is very vast and occupies 20% of the world's landmass.

Description of the Desert natural area

The desert is a vast flat area with a monotonous landscape, poor soil, flora and fauna. Such land areas are found on all continents, with the exception of Europe. The main feature of the desert is drought.

To the features of the relief natural complex Desert includes:

• plains;
• plateaus;
• arteries of dry rivers and lakes.

This kind natural area extends over most of Australia, a relatively small part of South America, and is located in the subtropical and tropical zones of the Northern Hemisphere. On the territory of Russia, deserts are located in the south of the Astrakhan region in the eastern regions of Kalmykia.

The largest desert in the world is the Sahara, which is located in ten countries of the African continent. Life here is found only in rare oases, and on an area of ​​over 9,000 thousand square meters. There is only one river flowing km, communication with which is not accessible to everyone. It is characteristic that the Sahara consists of several deserts, similar in their climatic conditions.

Rice. 1. The Sahara Desert is the largest in the world.

Desert types

Depending on the type of surface, deserts are divided into 4 classes:

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• Sand and sand-crushed stone . The territory of such deserts is distinguished by a variety of landscapes: from sand dunes without a single hint of vegetation, to plains covered with small bushes and grass.