SAHARA - World's Biggest Desert

Wednesday, November 4, 2009

The Sahara, with a size of 8.6 million km²(3,500,000 sq mi), is the world's largest desert. It covers most of Northern Africa, making it almost as large as the United States or the continent of Europe. Around 4 million people live here. Its maximum length is 4,800 km, running from west to east, and up to 1,200 km from north to south. Sahara covers most of Mauritania, Western Sahara, Algeria, Libya, Egypt, Sudan, Chad, Niger and Mali, and touches Morocco and Tunisia.To the north, Sahara is bordered by the Atlas Mountains and the Mediterranean Sea; in the west by the Atlantic Ocean; in the south, the desert zone reaches 16º northern latitude; in the east it is bordered by the Nile. Still the desert continues to the east of the river until it reaches the Red Sea, but this is not considered a part of the Sahara.

Sand sheets and dunes represent about 25% of the Sahara; the other parts are mountains, stoney steppes and oases. Pyramidal dunes can be as high as 150 metres, while mountainous sand ridges as high as 350 metres.
There are several rivers running through the Sahara, of which the Nile River and Niger River are the only permanent ones. The rest being seasonal, involves that most of the time, there is only a dry river bed, which may carry water for brief periods following uncommon rainfalls. There may be years in between this happening.

Amazing Facts Of Sahara Desert:
  • World's largest Hot desert covering around 9,00,000 square km.
  • Although being a desert area, one can notice annual rainfall in many regions of this vast land area. There are different climates witnessed in different regions.
  • This hot desert has annual temperatures. Some of the hottest months have temperatures exceeding 50 degrees C. In the winters, the temperatures drop below freezing points. This itself explains the diverse climates of this hot desert.
  • Observations made with the help of satellite photographs have proven this desert can shrink or even grow in size. 
  • This desert has some of the tallest sand dunes and these can reach 189 meters in height. The land area also has stone plateaus, large gravel plains, dry valleys and even sand flats. 
  • The Sahara desert has around 500 species of flora.
  • Emi Koussi is the highest peak that is seen in the Tibesti Mountains. This peak has a height of 3415 m.
  • This mysterious and vast place also has some of the most magnificent landscapes and despite harsh weather, it has attracted people to study details associated with the Sahara desert. This desert is more than a hot and dry place, it is one of the most remarkable areas known to man!

Climate History of Sahara: How it was formed

The climate of the Sahara has undergone enormous variation between wet and dry over the last few hundred thousand years. During the last glacial period, the Sahara was even bigger than it is today, extending south beyond its current boundaries. The end of the glacial period brought more rain to the Sahara, from about 8000 BC to 6000 BC, perhaps due to low pressure areas over the collapsing ice sheets to the north.

Once the ice sheets were gone, northern Sahara dried out. But in southern Sahara, the drying trend was soon counteracted by the monsoon, which brought rain further north than it does today. The monsoon is due to heating of air over the land during summer. The hot air rises and pulls in cool, wet air from the ocean, which causes rain. Thus, though it seems counterintuitive, the Sahara was wetter when it received more solar insulation in the summer. This was caused by a stronger tilt in Earth's axis of orbit than today, and perihelion occurred at the end of July.
By around 3400 BC, the monsoon retreated south to approximately where it is today, leading to the gradual desertification of the Sahara. The Sahara is now as dry as it was about 13,000 years ago. These conditions are responsible for what has been called the Sahara pump theory. Half of the Sahara receives less than 2 centimetres (0.79 in) of rain per year, and the rest receives up to 10 cm (3.9 in) per year.


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