Deserts and semi-deserts are waterless, dry regions of the planet where no more than 25 cm of precipitation falls per year. The most important factor in their formation is the wind. However, not all deserts experience hot weather; on the contrary, some of them are considered the coldest regions of the Earth. Representatives of flora and fauna have adapted to the harsh conditions of these areas in different ways.
How do deserts and semi-deserts arise?
There are many reasons why deserts appear. For example, the Atacama Desert receives little rainfall because it is located at the foot of mountains that shield it from rain with their ridges.
Icy deserts formed for other reasons. In Antarctica and the Arctic, the main snow mass falls on the coast; snow clouds practically do not reach the interior regions. Precipitation levels generally vary greatly, for one snowfall, for example, an annual norm can fall. Such snow driftsformed over hundreds of years.
Hot deserts are distinguished by the most diverse relief. Only some of them are completely covered with sand. The surface of most is littered with pebbles, stones and other miscellaneous rocks. Deserts are almost completely open to weathering. Strong gusts of wind pick up fragments of small stones and hit them against the rocks.
In sandy deserts, the wind carries the sand across the area, creating undulating sediments called dunes. The most common type of dunes are dunes. Sometimes their height can reach 30 meters. Ridge dunes can be up to 100 meters high and stretch for 100 km.
Temperature conditions
The climate of deserts and semi-deserts is quite diverse. In some regions, daytime temperatures can reach 52 oC. This phenomenon is due to the absence of clouds in the atmosphere, thus, nothing saves the surface from direct sunlight. At night, the temperature drops dramatically, again due to the lack of clouds that can trap the heat radiated from the surface.
In hot deserts, rain is rare, but sometimes there are heavy downpours. After rain, water does not soak into the ground, but rapidly flows from the surface, washing away soil particles and pebbles into dry channels called wadis.
Location of deserts and semi-deserts
On the continents, which are located in the northern latitudes, there are deserts and semi-deserts of the subtropical and temperate zones. Sometimes tropical ones are also found - in the Indo-Gangeticlowlands, in Arabia, in Mexico, in the southwestern United States. In Eurasia, extratropical desert regions are located in the Caspian lowland, on the Central Asian and South Kazakh plains, in the basin of Central Asia and in the Near Asian highlands. The Central Asian desert formations are characterized by a sharply continental climate.
In the southern hemisphere, deserts and semi-deserts are less common. Desert and semi-desert formations such as the Namib, Atacama, desert formations on the coast of Peru and Venezuela, Victoria, Kalahari, Gibson Desert, Simpson, Gran Chaco, Patagonia, the Great Sandy Desert and the Karoo semi-desert in southwest Africa are located.
Polar deserts are located on the mainland islands of the near-glacial regions of Eurasia, on the islands of the Canadian archipelago, in northern Greenland.
Animals
Animals of deserts and semi-deserts for many years of existence in such areas have managed to adapt to harsh climatic conditions. From cold and heat, they hide in underground burrows and feed mainly on underground parts of plants. Among the representatives of the fauna there are many types of carnivores: fennec fox, reed cats, cougars, coyotes and even tigers. The climate of deserts and semi-deserts has contributed to the fact that many animals have perfectly developed a thermoregulation system. Some desert dwellers can tolerate up to a third of their weight in fluid loss (e.g. geckos, camels), and among invertebrates there are species that can lose up to two thirds of their weight in water.
In North America and Asia there is a massreptiles, especially lizards. Snakes are also quite common: ephs, various poisonous snakes, boas. Of the large animals, there are saiga, kulans, camels, pronghorn, the Przewalski horse has recently disappeared (it can still be found in captivity).
The animals of the deserts and semi-deserts of Russia are a wide variety of unique representatives of the fauna. The desert regions of the country are inhabited by sandstone hares, hedgehogs, kulan, ceyman, poisonous snakes. In the deserts that are located on the territory of Russia, you can also find 2 types of spiders - karakurt and tarantula.
Polar bear, musk ox, arctic fox and some species of birds live in the polar deserts.
Vegetation
If we talk about vegetation, then in deserts and semi-deserts there are various cactus, hard-leaved grasses, psammophyte shrubs, ephedra, acacia, saxaul, soap tree, date palm, edible lichen and others.
Deserts and semi-deserts: soil
The soil, as a rule, is poorly developed, water-soluble s alts predominate in its composition. Among the soil-forming rocks, ancient alluvial and loess-like deposits predominate, which are processed by winds. Gray-brown soil is inherent in elevated flat areas. Deserts are also characterized by saline soils, that is, soils that contain about 1% of easily soluble s alts. In addition to deserts, s alt marshes are also found in steppes and semi-deserts. Groundwater, which contains s alts, when it reaches the soil surface, is deposited in its upper layer, resulting in soil salinization.
Completely different types of soils are characteristic of such climatic zones as subtropical deserts and semi-deserts. The soil in these regions has a specific orange and brick red color. Noble for its shades, it received the appropriate name - red soil and yellow soil. In the subtropical zone in northern Africa and in South and North America there are deserts where gray soils have formed. Red-yellow soils have formed in some tropical desert formations.
The natural zones of deserts and semi-deserts are a huge variety of landscapes, climatic conditions, flora and fauna. Despite the harsh and cruel nature of the deserts, these regions have become home to many species of plants and animals.
