Desert - a natural area

In the temperate zone of all the plains of Asia from the Caspian Sea in the west to central China in the east are almost entirely desert areas. In North America, some deserted lowering intermountain west on the mainland. Subtropical and tropical deserts are located in northwest India, Pakistan, Iran, Asia Minor. They cover the entire Arabian Peninsula and North Africa, the west coast of South America for almost 3500 kilometers, as well as the central part of Australia. On the outskirts of the desert surrounded by a zone of semi-desert. Natural conditions in the desert is such that summer, there is very hot and dry. Daytime air temperature in the shade rises to 4-40 ° and above, as in tropical deserts even more-up to +58 °. At night, heat falls often to 0 °. From such temperature changes in a person unaccustomed to such conditions occur fever, chills begins. Imagine if, in European terms in the summer when daytime temperature-f-20 ° in the evening she had sunk to the level of -20 °. Likewise, you feel a summer night in the desert. Well, there come the winter cold, and even in the Sahara at this time occasional frosts. Rain and snow in the desert does not happen, or are they rare visitors. For a whole year they fall less than 180 millimeters. And in the Atacama Desert, which is located in Chile (South America), this figure is even smaller. It is 10 millimeters of rain per year. The most well-known phenomenon of the desert - sand dunes. They are - an integral part of the desert landscape. Probably, if you hold a poll and ask the question: what is wilderness and what it remarkable? - Most will reply that the desert - vast sea of ??sand in the form of dunes. But it's not quite true. There are deserts and rocky, and clayey sites. Even the largest desert in the world - the Sahara, which occupies one third of the African continent - is composed of sand, only 20 percent. While the remainder consists of desert detritus (called hamada), pebble (regi) and clay (seriry). The sandy part is called Ergi. Dunes - "sand waves" - reach a height of 12 meters. The shape of their sex or crescent moon. One of its steep slope, like concave and one flat. That is because blowing in one direction and thus "cuts" the dunes with any one party. Often, the dunes are connected at their ends and form a whole chain of dunes. Under the action of wind, they move at speeds of several tens of centimeters to hundreds of meters per year from one place to another. Usual representation of the desert, are more correlated with its title - is the absence of any life, lifeless. But this is not true. Some plants and animals are very well adapted to survival in a dry climate and high temperatures. In the deserts of Central Asia is growing black and white saxaul. Large Haloxylon sometimes reaches a height of five meters! Leaves him in the form of twigs, which is adapted by nature to preserve moisture. From a distance the summer seems like it withered trees that dropped leaves in the winter and never turned green. But under the black haloxylon happens even shade in the summer heat saving people and animals. The same transformation is happening with the leaves of desert sagebrush. Her big "spring" leaves in summer give way to fluffy. In some plants the leaves have turned into thorns, like the sand acacia. In the deserts of the western hemisphere is growing all sorts of cactuses. This is a wonderful plant in their own way to adapt to life in the desert. In its fleshy stems and leaves accumulate much water that it can survive the long dry summer. North American cactus Carnegie giant reaches a height of 15 meters. In its stem, it contains 2-3 thousand gallons of water! Another important adaptation of plants of the desert is their root system. It allows you to extract moisture from deep soil layers. In animals, the desert also have their device. First of all, a color painting. Grayish-yellow hues allow animals to hide from the enemy or, conversely, to sneak up production quickly. All the inhabitants of the desert trying to escape from the scorching sun. Pigeons, sparrows and owls manage to nest and rest in the walls of the wells. Predators - eagles, falcons, crows - arrange their nests on the hills and the ruins of buildings, choosing in this seamy side. Many animals hide in holes or simply buried deep in the sand. Therefore, the day the desert becomes motionless and dead. But once the sun come over the horizon, as the temperature drops and the desert begins its life. On the surface of various crawling insects, reptiles, of which there are many. These are various snakes, lizards (including a very large - goannas) turtles. There agama lizard, which escape the heat and the enemies are not buried in the sand, but on the contrary, climbs on bushes - higher on hot sand. And one more feature of desert animals. In hibernation, they do not fall into the winter and summer, to bring the hottest time of year and experience the lack of moisture. But the gopher tonkopaly do without water, because he lacks that moisture contained in plants, serving him food. Many animals of the desert - great runners. Range over great distances in search of food and water wild asses kulan. They can reach speeds of up to 70 kilometers per hour. Even faster running cheetah - wild cats. Very good condition takes desert camel. Domesticated by man for more than four thousand years ago, he might eat grass, which is not absorbed by the body of other animals, few drinks. He was even able to drink salt water. In addition, the camel is well tolerated long-term hunger. Many people know that it is possible to him by the humps, which are deposited in fat stores. And the camel's body and his legs have toes that allow him to go on holiday, even on hot sand. But still, the desert is uninhabited. Although in our time of research scientists show that in some desert areas once upon a time there were human settlements, and even whole civilizations. But due to wars, natural disasters, people have left this place and moved to the other. As a result of neglect sands absorb these oases of life and turned them into the desert.