Temperate deserts. Message about the desert. Geographical features of deserts

home

The report “Deserts” for children on the subject of the world around us will help you prepare for the lesson.

Message on the topic “Desert”
Desert is a natural zone characterized by a flat surface, sparseness or absence of flora and specific fauna.

Most often, in deserts, the annual precipitation is less than 200 mm, in extraordinary areas - less than 50 mm, and in some deserts there is no precipitation for decades.

Deserts 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

- these are the Sahara, Victoria, Karakum, Atacama, Nazca, and the Gobi Desert.

• Deserts usually come in five types: sandy
• (vegetation is very rare, mostly thorny bushes, with roots going deep into the ground, this is necessary for water supply),
• clay,
• saline,
• rocky snowy deserts

(located beyond the polar circles and inhabited by animals resistant to cold).

The type of climate found in deserts is usually hot and arid. 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.

Life in deserts is concentrated mainly near oases - places with dense vegetation and bodies of water, as well as in river valleys.

Desert flora

The peculiarity of desert plants is that they must evaporate moisture as little as possible and obtain water at great depths or have their own supply of water. The plants have small, hard leaves or spines instead of leaves. The roots penetrate deep into the ground. Plants in the desert do not form a continuous cover. They are solitary, often growing in small groups among sand or cracked clay. Tree trunks are most often severely curved. The most common desert plant is saxaul bushes.
They grow in groups, forming small groves. Instead of foliage, their 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 - 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, there 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.

In the heat of the day, the desert seems uninhabited. Only occasionally do you see a lizard or some kind of bug. But as night falls, the desert comes to life. Animals crawl out of their hiding places to replenish their 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. Kangaroo jumper, may not come 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.

Jackals and coyotes Frequent breathing and sticking out your tongue save you from the heat.

African foxes, hares, hedgehogs Excess heat is emitted by large ears.

Long legs of ostriches and camels help to escape from the hot sand.
And the camel is more adapted to life in the desert than others. Thanks to its wide, calloused feet, it can walk on hot sand. 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.
Desert insects “thought of” reflecting the scorching rays of the sun with the surface of their bodies.
Some animals ( turtles, jerboas, toads, frogs) can spend the entire hot summer in hibernation.
In the summer, to avoid getting burned, desert snakes crawl sideways on the sand, and lizards run so fast that their paws do not have time to warm up.
To find food in the desert, animals must move quickly, have good hearing and vision, and be able to camouflage themselves.
Desert snakes lie in wait for their prey, completely buried in the sand, only their head with closely spaced ears and eyes peeks out.

You can write a report on deserts using this information.

The desert may seem like a lifeless area only at first glance. In fact, it is inhabited by unusual representatives of the animal and plant world, who have 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.

The relief features of the Desert natural complex include:

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

This type of natural zone 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:

TOP 1 articlewho are reading along with this

• 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.

Even the word “desert” itself evokes associations of emptiness and lack of life, but for the people who live on these lands, it seems beautiful and unique. The natural desert zone is a very complex territory, but it is alive. There are sandy, clayey, rocky, saline and snowy (yes, in the Arctic and Antarctica there is an Arctic desert) deserts. The most famous is the Sahara, it is also the largest in area. In total, deserts occupy 11% of the land, and if you count Antarctica - more than 20%.

See the geographical location of the natural desert zone on the map of natural zones.

Deserts are located in the temperate zone of the Northern Hemisphere and the subtropical and tropical zones of the Northern and Southern Hemispheres (they are characterized by special moisture conditions - the amount of precipitation per year becomes less than 200 mm, and the moisture coefficient is 0-0.15). Most deserts were formed on geological platforms, occupying the most ancient land areas. Like other landscapes of the Earth, deserts arose naturally, thanks to the peculiar distribution of heat and moisture over the earth's surface. In simple terms, deserts are located in places that receive very little or no moisture. The reasons for this are mountains that close the deserts from the oceans and seas or the proximity of the desert to the equator.

The main feature of semi-desert and desert lands is drought. Dry, arid zones include lands where the life of people, plants and animals is completely dependent on it. Arid lands make up almost a third of the planet's total land mass.

The relief of the desert zone is very diverse - complex highlands, small hills and island mountains, strata plains, ancient river valleys and closed lake depressions. The most common are aeolian landforms, which were formed under the influence of wind.

Sometimes the territory of deserts is crossed by rivers (Okavango - a river flowing into the desert, Yellow River, Syr Darya, Nile, Amu Darya, etc.), there are many drying up watercourses, lakes and rivers (Chad, Lop Nor, Air).

Soils are poorly developed - water-soluble salts predominate over organic substances.
Groundwater is often mineralized.

Features of the climate.

The climate in deserts is continental: winters are cold and summers are very hot.

Rain falls once a month or only once in several years, in the form of heavy downpours. Small rains simply do not reach the surface of the earth, evaporating under the influence of high temperatures. The deserts of South America are recognized as the driest areas in the world.

More deserts receive the bulk of their rainfall in spring and winter, and only a few deserts receive maximum rainfall in the summer in the form of showers (the great deserts of Australia and the Gobi).

The air temperature in this natural area can fluctuate greatly - during the day it rises to +50°C, and at night it drops to 0°C.
In the northern deserts, winter temperatures drop to -40 °C.

One of the most important features is the dryness of the air - during the day the humidity is 5-20%, and at night within 20-60%.

Winds play a big role in deserts. Each of them has its own name, but they are all hot, dry, carrying dust and sand.

The sandy desert is especially dangerous during a hurricane: the sand turns into black clouds and obscures the sun, the wind carries the sand over long distances, destroying absolutely everything in its path.
Another feature of deserts are mirages created by the sun's rays, which, when refracted, create very amazing pictures on the horizon.

Deserts and semi-deserts of Eurasia extend from the Caspian lowland to China. In Russia, this occupies the territory of the southeastern regions of the country. The Arctic desert is located in the northern territories. A distinctive feature of deserts and semi-deserts is the high fluctuation of winter and summer temperatures. Semi-deserts are located in the northern part of the natural zone. The climate here is milder, so they are characterized by a steppe landscape. Closer to the south, where it becomes arid and the vegetation cover practically disappears, there is a desert zone.

Geographical location and natural conditions

Arctic desert, as well as deserts and semi-deserts on the map of Russia

In the area of ​​the left bank of the Volga, deserts and semi-deserts stretch to Kazakhstan. The lands from the right bank of the river extend to the foothills of the Caucasus. The territories lie on the Caspian lowland, which is a flat area. Millions of years ago there was a seabed here. Most of the deserts are flat land, and only in the west are there steep slopes.

Climate

The natural zone is located in an area of ​​sharply continental climate. Rain and snow fall infrequently, making the climate dry but harsh. Most precipitation occurs in spring and summer. The level of evaporation exceeds the amount of precipitation.
The desert experiences strong daily and annual temperature ranges. During the day, the temperature difference can reach thirty degrees Celsius. In winter, the thermometer drops to -30°C and the winds rage. Their gusts blow away the snow cover from the soil, causing it to take on a black tint. Summer temperatures exceed +40°C. It rains rarely, but dust storms and dry winds often occur.

Vegetable world

The soils in semi-deserts are saline because they are based on ancient marine rocks. Wormwood-grass vegetation grows in semi-deserts. The lands contain little humus, and as a result of human economic activity they turn into shifting sands, and therefore are infertile. Nevertheless, the vegetation cover of the natural area is variegated. Feather grass, fescue, white wormwood, black wormwood, desert wheatgrass, and viviparous bluegrass grow here. From April to November, semi-desert lands are used as pastures. In June, with the onset of the dry period, the vegetation disappears, and the semi-desert becomes like a desert.

Closer to the south, the climate becomes arid, and the lands turn into a real desert. It is usually divided into two subzones: northern and southern. In the northern part the climate is mild. Subshrubs dominate here: saltmarsh barnacle, gray quinoa, and redberry. adapt to living conditions, many of them are leafless to reduce moisture evaporation. Vegetation in one form or another is located throughout the desert. In the southern part there are small trees and shrubs: sand acacia, Richter's solyanka, white saxaul. These areas also serve as pastures.

Animal world

In the zone of semi-deserts and deserts there are many that have adapted to harsh conditions. Animals dig deep holes to wait out the heat of the day in them. Jerboas, gophers, mice and voles have developed optimal conditions for existence in the harsh conditions of the natural zone.

During the polar night, which lasts 90 days, winter begins. Summer comes with a polar day. There are no transitional seasons. Winter temperatures are low, down to -60°C. There is little precipitation. Winds blow snow cover off the soil. Summer doesn't last long. The air temperature in July is +3°C. During the polar day, the sun does not warm the air well. The snow does not melt for 300 days a year, and winter comes overnight.

Trees and bushes are completely absent. In summer the lands are covered with lichens and mosses. Sedge and cereals grow on rocky soil. In the Arctic desert in summer you can find green oases with polar poppy, saxifrage, buttercup and Arctic pike.

The soil thaws to a depth of 40 cm. Iron oxides accumulate in the upper part, causing the soil to acquire a brown tint. There is sand and stones on the surface. Spherical formations, spherulites, are a landmark of cold deserts.

The fauna is scarce. Animals living in the Arctic desert feed on seafood. Polar bears, leading a semi-aquatic lifestyle, breed off the coast of Chukotka, on Franz Josef Land. In the Wrangel Island Arctic Nature Reserve, dens have been created for them. Arctic foxes, lemmings, hares, and reindeer come from here in the summer. Seals and walruses set up their rookeries on the coast. Birds are considered the most numerous class. Bird markets are organized by eider ducks, gulls, tundra partridges, guillemots, and terns. When the polar day arrives, snow geese, geese, plovers and dunlins flock to the Arctic.

Ecological problems of deserts and semi-deserts of Russia

The main threat to deserts turning into wastelands is human intervention. Recent scientific research has shown that these areas contain deposits of oil and natural gas. Due to technological progress, the need for them is constantly growing. Oil production pollutes nearby areas more than others. The entry of “black gold” into the environment entails an environmental disaster.

The desert and semi-desert zones of Russia are home to many different species of animals, some of which are listed in the Red Book. Poaching puts the survival of valuable animals into question. The process of desertification itself causes damage to agriculture. The number of pastures is decreasing.

Due to anthropogenic influence, ice in the Arctic is melting, as a result of which the Arctic desert zone itself is shrinking. If it disappears, a large number of flora and fauna will disappear from the face of the Earth. Snowmobiles and other ground vehicles pollute with exhaust emissions. Ozone holes negatively affect animal life. destroys mining, waste, . Large fish species are under threat of extinction. Their food, small fish and seafood, is caught on an industrial scale.

Deserts and semi-deserts need our protection. Already today there are nature reserves in the territories, but this is not enough. Work to protect natural areas must be controlled at the state level. Every effort should be made to resolve existing problems so that new ones do not arise.

Deserts are a specific geographical phenomenon, a landscape that lives its own special life, has its own patterns, has features and forms of change that are unique to it.

Deserts are areas of the earth's surface where, due to the too dry and hot climate, evaporation exceeds precipitation by many times, and therefore there is only a very sparse plant and animal life; These are usually areas of low population density, and sometimes even unpopulated. This term also refers to areas unfavorable for life due to a cold climate (so-called cold deserts).

What are the causes of deserts? Deserts are located in places where moisture does not reach. Many are either located far from the seas and oceans and are protected from them by mountains; or are close to the equator. The spiers of the mountains prevent rain clouds from reaching these lands and watering them with moisture. Near the equator, the climate is very dry due to the constant heat, which burns everything and requires much more moisture than usual.

It is drought that is a sign of desert or semi-desert lands. And such lands are called arid, that is, dry, zone. It does not include all areas of land where droughts occur, but only those where the life of humans, plants and animals is under their influence and depends on them. This is a geographical area of ​​the earth where the features of aridity (aridity) are expressed to the most extreme extent and reach such an extreme, beyond which the complete destruction of the biological life of the landscape begins. Almost one-third of the total land surface on our planet is arid. And this is 48 million km. sq. But less than 23% of the earth's surface is considered true deserts.

general characteristics

Deserts are common in the temperate zone of the Northern Hemisphere, subtropical and tropical zones of the Northern and Southern Hemispheres. All of them are characterized by humidification conditions (annual precipitation is less than 200 mm, and in extra-arid areas - less than 50 mm; the humidification coefficient, reflecting the ratio of precipitation and evaporation, is 0-0.15). The relief of deserts is varied: there is a complex combination of highlands, small hills and island mountains with structural strata plains, ancient river valleys and closed lake basins. The erosional type of relief formation is greatly weakened; aeolian landforms (landforms formed under the influence of wind) are widespread. For the most part, the territory of the deserts is drainless, sometimes they are crossed by transit rivers (Syr Darya, Amu Darya, Nile, Yellow River and others); There are many drying up lakes and rivers, often changing their shape and size (Lop Nor, Chad, Eyre), and periodically drying up watercourses are typical. Groundwater is often mineralized. The soils are poorly developed, characterized by a predominance of water-soluble salts over organic substances in the soil solution; salt crusts are common. The vegetation cover is sparse (the distance between neighboring plants is from several tens of centimeters to several meters or more) and usually covers less than 50% of the soil surface; in extra-arid conditions it is practically absent.

Huge drainless depressions are found almost everywhere in deserts. Some of them have enormous depth, for example, the Turfan Basin - 154 m below the level of the World Ocean, Akchakaya in the north of the Karakum Desert - 81 m, Karagiye on Mangyshlak - 132 m.

Climate

The main difference between deserts and other places is the almost complete absence of water: rivers, streams, fresh lakes. Rain falls very rarely - once a month or once every few years, mostly in the form of heavy downpours. Due to the high temperature, light rain does not reach the surface of the earth - the water evaporates on the way to it. Large intermountain depressions and basins are particularly dry. But the driest areas of the world are the deserts of South America.

Most of the world's deserts receive the bulk of their rainfall in winter and spring, and only a few - the Gobi and the great deserts of Australia - receive their maximum rainfall in the summer in the form of showers. In deserts, air temperatures can fluctuate within very wide limits. During the day up to +50°C in the shade, and at night - almost up to 0°C. In winter, the temperature in the northern deserts even drops to -40 °C. The air of deserts is extremely dry, and this is one of their most important features. During the day, humidity ranges from 5-20%, and at night - from 20 to 60%.

The soil heats up more than the air during the day, and then cools down more. The climate in deserts is continental: summers are very hot and winters are relatively cold.

Extratropical deserts are distinguished, first of all, by cold, very severe, but practically snowless winters, without thaws with frosts down to -40 ° C.

The climate is more favorable in the deserts located along the coasts of the Atlantic and Pacific Oceans, the Persian Gulf, where it softens somewhat, and therefore the humidity increases to 80-90%, and the range of daily fluctuations decreases. From time to time in such deserts there is dew and fog in the mornings.

Wind plays a big role in deserts. Desert winds have their own names, like this: in the Sahara - sirocco, in the Libyan and Arabian deserts - gabli and khamsin, in Australia - brickfielder, Afghan - in Central Asia. All winds are dry, hot, carrying sand or dust. They are distinguished by an enviable constancy of direction, its duration and frequency, which plays a positive role in the problems of orientation and maintaining the direction of movement.

The sandy desert is especially scary during a hurricane. Black clouds of sand rush through the air and obscure the light. Air vortices carry sharp grains of sand and hit all protruding objects with enormous force. The wind lifts huge masses of sand into the air, transporting them over long distances. The air temperature at this time rises to +50 °C, accompanied by a sharp drop in humidity.

It happens that the sand raised by the wind stands in the air in such a dense wall that the sun is not visible. And sometimes it twists into a spiral, rising to a great height in the form of a rotating funnel, expanding upward. There are terrible legends about Saharan sandstorms - “samum”, which means “poison”.

It is mortally dangerous for a person to get caught in sandy winds. Small hot grains of sand, raised by the wind, painfully cut the skin, get into all the cracks - into clothes, shoes, seep under the glasses of dust-proof glasses and watches. They grind your teeth, hurt your eyes, and clog your skin pores. People try to protect themselves in all sorts of ways. But they rarely return from sandstorms alive.

Another feature of deserts is mirages. As a rule, this happens in deserts of all types in the afternoon, when the soil is as hot as possible, and layers of air with different densities form in the surface atmosphere. The sun's rays, when refracted, create the most amazing pictures on the horizon. Mirages also occur in the early morning, before sunrise, when the air is saturated with fine dust. In the trembling, as if tangible, air, an image appears of either a lake, or a city, or the domes of minarets, or mountains, or alluring palm trees. Pictures of mirages can be so vivid and realistic that they can confuse even an experienced traveler and direct him in the other direction from the chosen direction of travel.

Desert types

Based on surface types, all deserts in the world can be divided into:

• sandy (erg);
• sandy-gravelly;
• crushed stone-gypsum (serir, reg);
• rocky (hamada, gobi);
• loess-clayey (takyr);
• salt marshes (dayi, sebkhi, shotty).

But each of the listed types of deserts is almost never found in its pure form. Most often, the desert is a combination of rocky and clayey plateaus, sand dunes, drainless basins, isolated table-shaped hills, salt marshes and takyrs (this is a landform formed when saline soils dry out). In some places, difficult-to-pass areas of fine, flour-like dust, called powder, form. And yet, each type of desert has its own unique characteristics.

Sandy deserts (ergs)

Many people imagine vast expanses of sand. Sandy deserts indeed - they have taken over more than half of all arid territories of the world. True, they are also diverse. Some of them are long dune chains devoid of any vegetation, others, on the contrary, are covered with rather dense herbaceous and shrub vegetation.

Each sandy desert has its own wind regime, which determines the construction features of sand massifs, which can take different forms. Where the direction of the winds is changeable and chaotic, the dunes take on bizarre shapes, terrifying travelers with their impassability.

Where winds prevail in one direction, the dunes are higher than in those areas where winds often change direction. The main type of such sandy relief in deserts is large parallel sand ridges several hundred meters long, 10 m to 1 km wide and an average height of 5 to 60 m. In some deserts, the height of the dunes exceeds 300 m. Sometimes the ridges are connected by bridges and , when viewed from above, resemble a honeycomb. But it happens that sand produces not ridges, but randomly located mounds.

Where there are no plants, sand, driven by the wind, sometimes moves over long distances. Loose sands are dangerous not only in motion, but also at rest. While moving in such sand, your feet get stuck, each step requires enormous effort, and literally after just half an hour, if you don’t have the habit and ability to walk on them, a person is not able to walk further. Cars also have difficulty making their way through the sand, and even then only with front and rear driving wheels and wide cylinders - they have a larger support area, and the car does not get stuck in the sand so much.

The largest sand desert in the world is Taklamakan in northwestern China, located between the Tien Shan and Tibet. Its length is 1200 km and its width is up to 400 km.

In other deserts of the world, sand does not occupy a dominant place. The sands of the Sahara occupy only 10% of its area, and the rest are rocky plateaus - hammads, separated by shallow valleys and depressions. Desert areas with fine rubble, often covered with so-called desert tan (black shiny crust), are called serir.

The Arabian deserts are only 25% covered with sand, and the rest of the territory is characterized by rocky areas and takyrs.

Clay deserts

Clay deserts are widespread on all continents. These are huge, lifeless spaces stretching for many tens of kilometers, covered with a smooth, table-like, hard clay layer, cracked into four- and hexagonal tiles and similar to a honeycomb.

They differ from sandy ones by much less mobility and worse water properties. Their surface greedily absorbs precipitation, but the upper layers, when moistened, quickly swell and stop letting water through. Only the top layer of 2-5 cm is moistened. With the onset of drought, it dries out quickly. But if clay sediments contain sand, then the water permeability of such soils increases and a larger supply of water is formed in them.

Such areas in Central Asia are called takyrs, and in the Gobi - toyrims. After rain falls or snow melts, the clay swells and becomes almost waterproof. At this time, the takyrs turn into shallow muddy lakes. On small takyrs in the spring you can often find small small puddles of fresh water - “kakk”. But with the onset of a hot period, the water becomes filled with various putrefactive bacteria and becomes unsuitable for drinking. With the onset of dry and hot weather, the water in them evaporates.

As a rule, large takyrs are surrounded by high dune ridges. And on the border of takyr and sand, small villages of shepherds appear; in Central Asia they are called “charva”.

Rocky deserts

Some of the most common types of deserts are stony, gravelly, rubble-pebble and gypsum deserts. They are united by roughness, hardness and surface density. The water permeability of rocky soils varies. The largest pebble and rubble fragments are located quite loosely. They easily allow water to pass through, and precipitation quickly seeps to great depths inaccessible to plants. But more common are surfaces where pebbles or crushed stone are cemented with sand or clay particles. In such deserts, rocky debris lies densely, forming the so-called desert pavement.

The relief of rocky deserts varies. Among them there are areas of smooth and flat plateaus, slightly sloping or flat plains, slopes, gentle hills and ridges (elongated hills with a flat, slightly convex or wavy top and gentle slopes). Gullies and gullies form on the slopes.

The rocky deserts of the Sahara (hamads), occupying up to 70% of its area, are often devoid of higher vegetation. Cushion-shaped freodolia and limonastrum bushes are established only on isolated stone screes. The more humid deserts of Central Asia, although sparsely, are evenly covered with wormwood and solyanka. Low-growing saxaul thickets are common on the sandy-pebble plains of Central Asia.

In tropical deserts, succulents settle on rocky surfaces. In South Africa, these are cissus with thick barrel-shaped trunks, milkweed, and “tree lily”; in the tropical part of America - a variety of cacti, yuccas and agaves. In rocky deserts there are many different lichens that cover stones and color them white, black, blood red or lemon yellow.

Scorpions, phalanges, and geckos live under the stones. Cottonmouth is found here more often than in other places.

Salt marshes

Almost all desert soils are saline to one degree or another. They are usually located along the shores and bottoms of salty, drying lakes or in places where groundwater emerges. Where the concentration of salts is especially high, a hard, sometimes cracked, crust of salt forms on the surface of the salt marsh. Its thickness reaches 10-15 cm.

In addition to table salt (sodium chloride), you can find calcium and potassium salts, mirabilite and gypsum here. The largest salt marshes of this type are common in the Dasht-Kevir desert in Iran (“kevir” is translated from Iranian as “salt marsh”). Here, salt layers form thick layers, split by cracks into polygons up to 50 m across, separated by salt hummocks and partitions up to 1 m high.

Depending on the concentration of the saline solution and the depth of its occurrence under the surface, salt marshes can be covered with a dense salty crust, cracked like takyrs, or they can be a quagmire in which your feet get stuck deeply (it can completely suck in a person or animal). Such salt marshes are usually impassable at any time of the year. Cortical salt marshes become limp only during the rainy season, and in the dry season their surface is smooth and hard.

Flora and fauna

The vegetation is diverse, which is due to the structure of the desert surface, the diversity of soils, and frequently changing moisture conditions. The nature of desert vegetation on different continents has many common features that arise in plants in similar living conditions: severe sparseness, poor species composition.

For inland deserts of temperate zones, plant species of the xerophilic type are typical (xerophiles are organisms that live in conditions of extremely low humidity and cannot tolerate high humidity), including leafless shrubs and subshrubs (saxaul, juzgun, ephedra, solyanka, wormwood, etc.). An important place in the phytocenoses of the southern subzone of deserts of this type is occupied by herbaceous plants - ephemerals (an ecological group of herbaceous annual plants with a very short growing season (some complete the full cycle of their development in just a few weeks)) and ephemeroids (an ecological group of perennial herbaceous plants with a very short growing season). period falling at the most favorable time of year).

The subtropical and tropical inland deserts of Africa and Arabia are also dominated by xerophilous shrubs and perennial herbs, but succulents also appear here. Massifs of dune sands and areas covered with a salt crust are completely devoid of vegetation.

The vegetation cover of the subtropical deserts of North America and Australia is richer (in terms of the abundance of plant mass, they are closer to the deserts of Central Asia) - there are almost no areas devoid of vegetation here. The clayey depressions between the sand ridges are dominated by low-growing acacia and eucalyptus trees; The pebble-crushed stone desert is characterized by semi-shrub hodgepodges - quinoa, prutnyak, etc. In subtropical and tropical oceanic deserts (Western Sahara, Namib, Atacama, California, Mexico) succulent-type plants dominate.

There are many common species in the salt marshes of temperate, subtropical and tropical deserts. These are halophilic and succulent subshrubs and shrubs (tamarix, saltpeter, etc.) and annual saltworts (solyanka, sweda, etc.).

The phytocenoses of oases, tugai (a specific mini-ecosystem that arises along never-drying river banks), large river valleys and deltas differ significantly from the main vegetation of deserts. The valleys of the desert-temperate zone of Asia are characterized by thickets of deciduous trees - turango poplar, jida, willow, elm; for river valleys in subtropical and tropical zones - evergreens - palm, oleander.

Deserts are inhabited mainly by specialized forms (with adaptations both morpho-physiological and in lifestyle and behavior).

Deserts are characterized by fast-moving animals, which is associated with the search for water and food, as well as protection from persecution. Due to the need for shelter from enemies and harsh climatic conditions, a number of animals have highly developed adaptations for digging in the sand (brushes made of elongated elastic hair, spines and bristles on the legs, used for raking and throwing away sand; incisors, as well as sharp claws on the front paws - in rodents). They build underground shelters, or are able to quickly burrow into loose sand. Many animals are capable of running fast.

The fauna of deserts is characterized by “desert” coloring - yellow, light brown and gray tones, which makes many animals inconspicuous. Most of the desert fauna is nocturnal in summer. Some hibernate, and in some species (for example, ground squirrels) it begins at the height of the heat (summer hibernation, directly turning into winter) and is associated with burning of plants and lack of moisture.

Lack of moisture, especially drinking water, is one of the main difficulties in the life of desert inhabitants. Some of them drink regularly and a lot and, therefore, move long distances in search of water (grouse) or move closer to the water during the dry season (ungulates). Others rarely use watering holes or do not drink at all, limiting themselves to moisture obtained from food. Metabolic water, formed during the metabolic process (large reserves of accumulated fat), plays a significant role in the water balance of many representatives of the desert fauna.

The desert fauna is characterized by a relatively large number of species of mammals (mainly rodents, ungulates), reptiles (especially lizards, agamas and monitor lizards), insects (Diptera, Hymenoptera, Orthoptera) and arachnids.

Amazing deserts

Deserts are characterized by amazing phenomena:

• "dry fog"
• "sound of the sun"
• "singing sands"
• "dry rain"
• mirages, etc.

“Dry fog” occurs when the desert is calm and the air is filled with dust and visibility completely disappears.

“Dry rain” occurs when precipitation evaporates due to high temperatures before reaching the ground.

“Singing sands” occur when tons of moving sand emit enchanting sounds: high, melodious, with a strong metallic tint.

The “sound of the sun” occurs at 40 degrees of heat, when stones burst in the desert, making a special sound.

“Whisper of stars” occurs at 70-80 degrees below zero, when water vapor exhaled by a person instantly turns into ice crystals. Colliding with each other, they begin to rustle.