Which countries does the Sahara desert cover?
Good answers, but the Sahara desert (Tenere in Tamasheq) covers also the very most Northern tip of Nigeria and Burkina Faso.Thus, the countries that are in the Sahara are:AlgeriaLibyaEgyptWestern Sahara (If you consider it a country)MoroccoMauritaniaMaliNiger RebpulicChadParts of SudanHuge part of ChadSmall part of Nigeria where the Sahel meets the Sahara.Small part of Burkina Faso
Why is there so much sand in the Sahara desert?
Sand and bare rock cover only about one-fifth of the Sahara Desert. More than half of the Sahara is made up of soil known as yermosols that are shallow deposits over gravels and pebbles. These soils are no older than 50 million years. As recently as 5000 years ago the Sahara was probably not a desert, and may have supported vegetation such as savanna woodlands now present in eastern Africa. Prior to that wetter period it was probably a desert, according to some recent work on dating paleodunes in Chad. It is a large region so it is easy to over generalize when trying to describe the geology. Much of the sand has originated from weathering of exposed Mesozoic and Paleozoic basement rocks. Several mountain ranges cut through the Sahara. In late Eocene the Tethys Sea had regressed from much of this area, likely leaving behind large deposits of sand and Cretaceous age sandstone that had been laid down while the area was beneath the sea. This probably accounts for much of the sand. Sedimentary deposits of sandstone have been once again eroded, reworked, and recycled. Most of the aeolian sand in the Sahara is considered to be Pleistocene and Holocene in age. The sand is considered superficial by geologists working on understanding the underlying geomorphology. In the studies of the Selima Sand Sheet in the eastern Sahara, the sand was measured as from 1 to 6 meters in depth. In other areas where dunes have accumulated there are likely to be depths of sand of several hundred meters, however typical dunes are generally about ten meters in height, with some reaching 100 meters.
How Long did it take Muslim Merchants to cross the Sahara Desert in the 13th century?
The Sahara and Islam: The Bonds Unifying Northern Africa The geography of the northern half of Africa is dominated by the Sahara desert. Throughout its vast area, 2,800 km (1,700 miles) from north to south and nearly 8,000 km (5,000 miles) from east to west, rainfall is less than 13 cm (5 inches) a year. Except around a few oases where underground supplies of water reach the surface, agriculture is impossible, and the desert’s only inhabitants have been nomadic herdsmen, breeding camels and moving their animals seasonally from one light grazing ground to another. To the north of the desert lies the temperate Mediterranean coastland – its rainfall concentrated between January and March, with wheat and barley as its main cereal crops and sheep, the main stock of its highland pastures. Southward are the tropics, the land of the summer rains, favouring a different set of food crops from those grown around the Mediterranean. In the desert and northward live Berbers and Arabs, fair-skinned peoples speaking languages of the Afroasiatic family. South of the desert begins the ‘land of the blacks’ – to the Greeks; ‘Ethiopia’, to the Berbers, ‘Akal n’Iguinawen’ (Guinea); and to the Arabs, ‘Bilad as-Sudan’. The desert has always been a formidable obstacle to human communication, but for two thousand years at least – since the introduction of the horse and the camel made travel easier – people have persevered in overcoming its difficulties. Before the days of the motorcar and the aeroplane, it took two months or more to cross. Nevertheless,
How does sand get into the deserts?
Deserts aren't defined on the basis of sand. As a matter of fact, some people have said that Antarctica is the largest desert on Earth and there's no sand there (only snow and ice)! The reason for this is that deserts are defined by how dry they are. A typical definition is that deserts are simply areas which receive less than 10 inches (25 cm) of precipitation (rain or snow) per year. A more sophisticated definition of deserts takes into account not just the average amount of precipitation but also the average temperature (hot climates will evaporate more water and be drier) and the frequency of precipitation (a tiny bit of rain every couple of weeks is better than all of the rain in a large once-a-year soaking). Anyway, deserts are simply arid (dry) areas and are more often rocky with scattered vegetation like you see in the southwestern United States than areas with large sand dunes which is what people commonly imagine when thinking about, for example, the Sahara desert. In reality, areas of drifting sand dunes only occupy about 10% of the Sahara desert. Sand dunes aren't only found in deserts either. Beaches in places like Cape Cod, the southern shore of Long Island, the eastern shore of New Jersey, etc. all consist of fairly large areas of sand with drifting dunes. These aren't desert areas. When sand dunes do occur in deserts, they formed because there was a source for the sand (eroding nearby sandstone, for example) which accumulated by the action of blowing winds into a local depression. Over time, large accumulations may result and their movement by blowing wind and the arid climate keeps vegetation from rooting the sand into place. Desert areas generally form by a process called desertification. In the past, before people existed, this resulted from global climate changes primarily due to plate tectonics (the movement of the Earth's continents over geologic time). In recent times, deserts have increased in size due to the actions of people who live in and near deserts. When people overgraze animals (like cattle, sheep, and goats) and cut trees for firewood or for farming, desert areas are able to increase in size because these actions destroy the vegetation which makes it easier for the soil to blow away (especially during times of drought). This is a big problem today in Africa south of the Sahara Desert.
How did the Sahara desert protect Egypt from any invasions?
The Sahara desert has less than 1 inch rainfall a year; almost nothing lives or grows there, and water sources are extremely few and far between.Anyone wanting to invade Egypt from the south or southwest would have to cross hundreds of miles of barren desert, and would have to carry all their food and water for the march with them, highly impractical for an invading army.