Deserts and semi-deserts are waterless, dry areas of the planet where no more than 25 cm of precipitation falls annually. The most important factor in their formation is the wind. However, not all deserts have hot weather, some of them, on the contrary, are considered the coldest regions of the Earth. Representatives of flora and fauna have differently adapted to the harsh conditions of these areas.
How do deserts and semi-deserts arise?
There are many reasons why deserts arise. For example, in the Atacama desert there is little rainfall because it is located at the foot of the mountains, which with its crests cover it from rain.
Ice deserts formed for other reasons. In Antarctica and the Arctic, the bulk of the snow falls on the coast, with virtually no snow clouds reaching the interior. The level of precipitation mainly varies greatly, for one snowfall, for example, the annual norm may fall. Such snow deposits form over hundreds of years.
Hot deserts have the most diverse terrain. Only some of them are completely covered with sand. The surface of the majority is dotted with pebbles, stones and other different rocks. Deserts are almost completely exposed to weathering. Strong gusts of wind pick up fragments of small stones and hit them on the rocks.
In sandy deserts, wind carries sand across the territory, creating undulating sediments called dunes. The most common type of dune is dunes. Sometimes their height can reach 30 meters. Ridge dunes can be up to 100 meters high and extend over 100 km.
Temperature mode
The climate of deserts and semi-deserts is quite diverse. In some regions, daytime temperatures can reach 52 o C. This phenomenon is associated with the absence of clouds in the atmosphere, thus, nothing saves the surface from direct sunlight. At night, the temperature drops dramatically, which again is explained by the absence of clouds that can trap the heat radiated by the surface.
In hot deserts, rains are a rare occurrence, but sometimes heavy rains occur here. After rain, water is not absorbed into the soil, but rather drains from the surface, washing away particles of soil and pebbles into dry canals called Wadi.
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-Gangetic lowland, 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. Central Asian desert formations are characterized by a sharply continental climate.
Deserts and semi-deserts are less common in the southern hemisphere. Here are desert and semi-desert formations such as 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 Carru semi-desert in southwestern Africa.
The polar deserts are located on the mainland islands of the adjacent regions of Eurasia, on the islands of the Canadian archipelago, in the north of Greenland.
Animals
Animals of deserts and semi-deserts over many years of existence in such areas have managed to adapt to harsh climatic conditions. They hide from the cold and heat in underground burrows and feed mainly on the underground parts of plants. Among the representatives of the fauna there are many species 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 developed a thermoregulation system. Some desert inhabitants can withstand fluid loss up to a third of their weight (for example, geckos, camels), and among invertebrates there are species that can lose water up to two-thirds of their weight.
In North America and Asia, there are many reptiles, especially many lizards. Snakes are also quite common: ephs, various poisonous snakes, stranglers. Of the large animals, saigas, kulans, camels, and pronghorn are found, the Przhevalsky horse has recently disappeared (you can still see it in captivity).
Animal deserts and semi-deserts of Russia are a wide variety of unique representatives of the fauna. In the desert regions of the country live sandstone hares, hedgehogs, kulan, jaman, poisonous snakes. In the deserts that are located on the territory of Russia, you can also meet 2 types of spiders - karakurt and tarantula.
Polar deserts are inhabited by a polar bear, musk ox, arctic fox and some species of birds.
Vegetation
If we talk about vegetation, then in the deserts and semi-deserts there are various cactus, hard-leaved cereals, shrub-psammophytes, ephedra, acacia, saxaul, soap tree, date palm, edible lichen and others.
Deserts and semi-deserts: soil
Soil, as a rule, is underdeveloped; water-soluble salts prevail in its composition. Among parent rocks , ancient alluvial and loesslike deposits, which are processed by winds, predominate. Gray-brown soil is inherent in the elevated lowlands. Deserts are also characterized by salt marshes, that is, soils that contain about 1% of readily soluble salts. In addition to deserts, salt marshes are also found in steppes and semi-deserts. Ground water, which contains salt, is deposited in its upper layer when it reaches the surface of the soil, resulting in soil salinization.
Completely different types of soils are characteristic of climatic zones such as subtropical deserts and semi-deserts. The soil in these regions has a specific orange and brick red color. Noble to its shades, it received the corresponding name - red earth and yellow earth. In the subtropical zone in northern Africa and in South and North America, there are deserts where serozems formed. Red tropical yellow soils formed in some tropical desert formations.
Natural zones of deserts and semi-deserts are a huge variety of landscapes, climatic conditions, flora and fauna. Despite the severe and cruel nature of the deserts, these regions have become home to many species of plants and animals.