MC_A Concise History of Africa

A Concise History of Africa

plains, and salt flats, with large sand dunes forming only a minor part. The topography ranges from the Tibesti Massif of northern Chad (at 11,000 feet/3350 meters) to the Qattara Depression of Egypt (at 436 feet/133 meters). Scattered, fertile oases usually lie in depressions, punctuating the ancient caravan routes which, over time, have been adapted into modern roads. Here, water is present where the water table comes to the surface, and at greater depths lies in huge underground aquifers. These are believed to be filled with water

dating from the Pleistocene period, when the Sahara was much wetter than it is today; the more than 20 lakes or chotts in the north, and the areas of salt flats and boggy salt marshes, are also thought to be remnants of this pluvial age. We know that rivers once ran through the Sahara, because dried- up riverbeds, known as wadis , still exist, which fill up with water and become active streams for a short time. The Nile and the Niger are the only permanent rivers in the region, being fed by rainfall outside the area.

Natural Resources Important discoveries of minerals, oil, and gas

have been made in the Sahara, but in most cases inaccessibility has delayed their exploitation. Salt is still mined, as in the past, at Taoudenni in Mali, and at Bilma in Niger, and it is transported, as in the days of the great medieval kingdoms of West Africa, by camel caravans across the desert.

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