Deserts of the semi-desert are waterless, dry areas.planets where not more than 25 cm of precipitation falls annually. The most important factor in their formation is the wind. However, not all the deserts have hot weather, some of which, on the contrary, are considered the coldest regions of the Earth. Representatives of flora and fauna have adapted themselves differently to the harsh conditions of these areas.
How do deserts and semi-deserts arise?
The causes by which deserts arise,there are many. For example, there is little rainfall in the Atacama Desert because it is located at the foot of the mountains, which with its crests cover it from the rain.
Ice deserts were formed for other reasons.In Antarctica and the Arctic, the bulk of the snow mass falls on the coast, almost no snow clouds reach the interior. Rainfall mainly varies greatly, for one snowfall, for example, the annual norm can fall. Such snow deposits are formed over hundreds of years.
Hot deserts differ the most diverserelief. 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 open to weathering. Strong gusts of wind pick up the fragments of small stones and hit them on the rocks.
In the sandy deserts the wind carries sand alongterritory, creating a wavy sediment, which is called the dunes. The most common type of dunes - dunes. Sometimes their height can reach 30 meters. The ridge dunes can have a height of up to 100 meters and extend for 100 km.
Temperature conditions
The climate of deserts and semi-deserts is quite diverse. In some regions, daytime temperatures can go as high as 52 aboutWITH.This phenomenon is due to the absence of clouds in the atmosphere, thus, nothing saves the surface from direct sunlight. At night, the temperature is greatly reduced, which again is due to the absence of clouds that are able to trap the heat emitted by the surface.
In hot deserts, rain is a rare occurrence, howeversometimes there are strongest downpours. After the rain, the water is not absorbed into the soil, but rapidly drains from the surface, washing away particles of soil and pebbles into dry canals, which are called wadis.
Location of deserts and semi-deserts
On the continents, which are located in the northernlatitudes, there are deserts and semi-deserts of the subtropical and temperate zones. Sometimes also found tropical - in the Indo-Gangetic Lowland, in Arabia, in Mexico, in the south-west of the United States. In Eurasia, extratropical desert areas are located in the Caspian lowland, on the Central Asian and South Kazakh plain, in the basin of Central Asia and in the Near Eastern highlands. The Central Asian desert formations have a sharply continental climate.
In the southern hemisphere of the desert and semi-desertare less common. There are such desert and semi-desert formations 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 Karoo semi-desert in southwestern Africa.
The polar deserts are located on the continental islands of the glacier regions of Eurasia, on the islands of the Canadian Archipelago, in the north of Greenland.
Animals
Desert and semi-desert animals for many yearsexistence in such areas managed to adapt to the 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 species of carnivores: Fenek 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 an excellent thermal control system. Some desert dwellers can tolerate fluid loss of up to one third of their weight (for example, geckos, a camel), and among invertebrates there are species that can lose water up to two thirds of their weight.
Mass is found in North America and Asiareptiles, especially many lizards. Snakes are also quite common: efy, various poisonous snakes, strangers. Of the large animals, there are saiga, kulans, camels, pronghorn, the Przewalski horse has just disappeared (you can still see it in captivity).
Animals of the desert and semi-desert of Russia area wide variety of unique fauna. In the desert regions of the country there are hares, sandstones, hedgehogs, kulan, jaiman, 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 deserts are inhabited by polar bears, musk oxen, arctic fox and some species of birds.
Vegetation
If we talk about vegetation, then in the deserts andsemi-desert there are various cactus, stiff-leaved cereals, shrubs, psammophytes, ephedra, acacia, saxaul, soap tree, date palm, edible lichen and others.
Deserts and semi-deserts: soil
The soil is usually poorly developed, in its compositiondominated by water soluble salts. Among the soil-forming rocks, ancient alluvial and loess-like sediments predominate, which are processed by winds. Gray-brown soil is inherent to elevated plain areas. 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. Groundwater that contains salt, when it reaches the surface of the soil, is deposited in its upper layer, resulting in salinization of the soil.
Completely different soil types are characteristic of suchclimatic zones like subtropical deserts and semi-deserts. The soil in these regions has a specific orange and brick red color. Due to its shades, it received the appropriate name - red and yellow. In the subtropical zone in northern Africa and in South and North America there are deserts where serozems have formed. Red-yellow soils have formed in some tropical desert formations.
Desert and semi-desert natural areas area huge variety of landscapes, climatic conditions, flora and fauna. Despite the harsh and cruel temper of the desert, these regions have become home to many species of plants and animals.
