Many deserts ... water

On our planet, Zacat in northern Africa is the number one desert and also the third largest desert (after Antarctica and the Arctic). When it comes to deserts, we often think first of all about sand and chronic drought.

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The sand covering the Xaak surface has an average thickness of 150 meters, where the sand is the largest in the pile, its peak is as high as the pressure of Chi-phen Tower in France. Some people have calculated that, to remove all the sand in Xa-ra, all humanity must join their hands, and with the current population of about 7.2 billion people, each person must carry more than three million buckets. New sand.

But in fact, in Jerusalem, only 20% is sand, 10% is sand mixed with pebbles and rock salt, while most, about 70%, are rough rocks.

Desert Saharan

With an area of ​​more than nine million square kilometers, Desert Hadiah spread the territory of many countries: Egypt, Sudan, Libya, Algeria, Sat, and Ri Turin, Morocco, Mauritania, Morocco, Nigeria, Tunisia, Western Jakarta. There are about 2.5 million people living here, most of them are two ethnic groups of Turks, Arabs and groups of black people like Tu-bu, Nu-bi-an, Da Nang, Nigeria, Pe-un or Phuket, Hau-xa, Xong-hai . They take care of goats, donkeys, camels and - due to the harsh climate, always lack of grass - often live a nomadic life.

In the ethnic groups that had long lived, it was the Arabs who brought camels into this region, forming a commercial network across the desert, effectively off-Saharan . That "Silk Road" has existed for centuries, until the development of maritime technology allowed ships - originally from Portugal, but soon after, from all Western Europe-to-be close. Ships have many water around the desert and collect resources to sell to other places. By 500 BC, due to lack of water and the market, human footsteps had never exceeded southern Morocco today.

In the valley in the center of Hashah, there existed an urban civilization that developed thanks to the canals connecting the valleys to the mountains and leading water into the fields. The civilization became crowded and powerful, conquering the surrounding areas and capturing many slaves to use in expanding the canal system. But, finally, after the underground water was no longer exploitable, so it was impossible to continue to expand its canal system deep into the mountain, the civilization had to collapse.

Scientists have identified the "desert" desert desert to 2.5 million years old, about 5,400 years ago as the beginning of the process of deserting this territory. The relics found by archaeologists prove that: Thousands of years ago, this place was home to vast amounts of dry grass, with numerous rivers and lakes. Now those places are still valleys, when heavy rains can become rivers full of water, but only a few hours are inundated.

But the water is still crowded in the heart, for example in the territory of Libya.

But, the creator did not want to leave the desert of Dakar to fall into disrepair. On hot summer days like roasting, sand here is 80 ^° C hot, so the amount of evaporation is much larger than the amount of rain falling. Each year, rainfall is usually only about 100mm, while steam rises from 2,500 to 5,500mm. Meet the sunny day, falling rain from the sky and not touch the ground yet . dissolved.

Yet the desert of Saharan has not dried up! The sand here is much less than . water. Scientists surveyed in the dry desert is a great groundwater sea, estimated at 375,000 km ³ while a famous Bai-Bai lake in Russia contains only 23,600 km ³ of fresh water. This is the largest underground lake in the world, right under the territory of Egypt, Libya, Police and Sudan.