Tropical deserts and semi-deserts of Africa
Where the dry period lasts sometimes year-round, and short-term rains fall irregularly, lies the natural zone of tropical deserts and semi-deserts. The largest area in Africa, it occupies the Northern Hemisphere. Here, from the Atlantic Ocean to the Red Sea for 5000 km wide stripe from west to east extends the Sahara desert. In southern Africa, the deserts occupy significantly smaller areas. Here a narrow strip along the Atlantic coast stretches the severe Namib Desert. In the interior of the continent is the semi-desert Kalahari.
The Sahara is the largest desert in the world. In its internal areas, rain does not happen for years, and even decades. And the rain often does not reach the surface of the earth: it evaporates in the air because of the high temperature. Strong heat during the day is replaced by a piercing cold at night, while sandy and dusty brown sweep away all life on their way. The surface of the rocks during the day is heated to +70 ° C, and at night the temperature
Due to the different degree of destruction of the surface, three types of deserts have formed in the Sahara: rocky, sandy and clayey. Stony deserts are common on the highlands, plateaus and elevated plains, consisting of hard rock. Sand deserts occupy mostly lowland plains and hollows. They amaze with the boundless “sea” of sand dunes and sand dunes, which are transported by the wind. Clayey deserts are less common.
A small amount of precipitation led to the fact that there are no constant streams in the desert, and dry riverbeds – wadi are preserved. They fill with water only during the rain, but not for long. The sun quickly evaporates the water, and after a few hours the river disappears.
Since the desert is poor
All life in the Sahara is concentrated in oases. They arise where groundwater flows close to the surface of the earth. There are wells or springs, temporary lakes formed in the basins. In the oases, acacias grow, ducks, turtledoves, pigeons, hazel grouses, desert lark, runners, falcons are found. Hospitable “mistress” of desert oases is a date palm, giving people a cozy shade and delicious fruits. From the notch of the trunk follows a cool juice. From the leaves of the tree weaving baskets and shoes.
But oases are extremely rare. There is almost no vegetation on the vast expanses of the Sahara. Ephemeral plants adapted to the harsh climate of the desert with a short period of active existence. Rain will rachet and leaves and flowers immediately appear on them. The ephemera ripens, fades and fades so quickly that their seeds ripen before the next rain and just wait for the water to quickly germinate.
Due to the long root system from the groundwater receives the moisture of the camel thorn. Its leaves to reduce the evaporation of water are modified into short needles.
Animals survive those who are able to quickly move from one oasis to another, accumulate water in their body, or some predators that almost do not drink water, receiving it with the blood of their victims. Best to life in the desert are adapted reptiles: snakes, lizards, turtles. They have dry scaly skin, evaporating little water. From the sun these animals hide in sand or cracks, and eat insects.
In the southern part of Africa, the coastal Namib Desert extends. The climate here is extremely harsh. The very name of the desert says about this: “what is bypassed”. Rains are extremely rare, so most of the desert is devoid of vegetation – only rocks, stone, sand and salt. The high sand dunes not fixed by the plant roots move in the direction of the prevailing wind. Only along the rivers grow acacia and tamarisk. The most amazing plant of the Namib desert is Velvichia. This tree has a short and thick trunk, from which two leathery sheets with a length of up to 3 m go away. With moisture, Velichy is supplied with sheets absorbing it from the fog. The plant lives up to 2000 years and never dumps leaves that grow all the time.
The most severe is the nature of the ocean coast of the desert. It is no accident that this area was called the Skeleton Coast. From thirst, diamond seekers and shipwrecked people have been killed many times.
The Kalahari semi-desert is covered with huge sand dunes, which one after another, like giant waves, run across its surface. The dunes are painted pink, red and dark red, almost brown, since the soil contains a lot of iron. There are more precipitations than in the Namib Desert, so in Kalahari there is a vegetation cover. In some places, the desert resembles a steppe. At the tops of the dunes grows a hard grass, which during the rains turns green, and in a drought becomes faded.
On the slopes of the dunes, low shrubs with spines can grow. In Kalahari there are milk sprouts, aloe and other plants that accumulate moisture in stems, leaves, trunks. Kalahari is the birthplace of watermelons. Wild watermelons are still replacing water for humans and animals.
The animal world of deserts and semi-deserts in southern Africa is represented by lizards, snakes, turtles. Many insects: various species of beetles, locusts, scorpions, etc. There are lions, cheetahs, jackals. Escaping from poachers, sometimes even elephants come to the Namib desert.
The population of the desert zone of Africa is engaged in nomad livestock, in oases – farming. Appear industrial settlements for mining. The trans-Sakhar motor road was laid, caravan routes between oases were preserved.
Man’s economic activity leads to the expansion of the desert zone at the expense of semi-deserts and savannas.
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