Teacher – The Sahara is the world’s largest hot desert and third largest desert, after Antarctica and the Arctic. At over 9,400,000 square kilometers, it covers most of North Africa, making it almost as large as China or the United States. The Sahara stretches from the Red Sea, including parts of the Mediterranean coasts, to the outskirts of the Atlantic Ocean. To the south, it is delimited by the Sahel – a belt of semi-arid, tropical savanna that composes the northern region of central and western sub-Saharan Africa. Some of the sand dunes can reach 180m in height. The name comes from the Arabic word for desert. Have you ever been to the Sahara? Oh yes, Judy? Okay…And when did you go, and why?
Student – Um..I was in Egypt, um, and I spent two days in the Sahara last year.
Teacher – Wonderful! And..um..can you tell me about the boundaries of the Sahara desert? Do you remember what the boundaries of the Sahara desert are?
Student – Um..I think I can..um..the Sararas..sorry, the Sahara’s boundaries are the Atlantic Ocean on the west, the Atlas Mountains and the Mediterranean on the north, the Red Sea on the east, and the region of Sudan and the valley of the Niger River on the south.
Teacher – Exactly! Very good, and the Sahara is divided into Western Sahara, the central Hoggar Mountains, the Tibesti Mountains, the Air Mountains, Tenere Desert, and the Libyan Desert. The highest peak in the Sahara is “Emi Koussi” in the Tibesti Mountains, in northern Chad. The Sahara is the largest desert on the African continent. The southern border of the Sahara is marked by a band of semi-arid Savanna, called the Sahel. South of the Sahel lies southern Sudan and the Congo river basin. Most of the Sahara consists of rocky hamada – ergs – like large areas covered with sand dunes. People lived on the edge of the desert thousands of years ago, since the Ice Age – the Sahara was then a much wetter place than today. Over 30,000 petroglyphs of river animals, such as crocodiles, survived, with half found in the Tassili n’Ajjer in southeast Algeria. Fossils of dinosaurs, including many that you don’t even know, have also been found there. The modern Sahara though, is not lush in vegetation except the Nile Valley and a few oases, and in the northern highlands where Mediterranean plants such as the olive tree are found to grow. The region has been this way since about 1600 B.C.E, after shifts in the Earth’s axis increased temperatures and decreased precipitation. Then, due to climate change, the savanna changed into the sandy desert as we know it now. Dromedary camels and goats are the domesticated animals most commonly found in the Sahara. Because of its qualities of endurance and speed, the dromedary is the favorite animal used by nomads. The death stalker scorpion can be about 10cm long and you can find it everywhere in the Sahara. Its venom contains large amounts of agitoxin and scyllatoxin, and is very dangerous; however, a sting from this scorpion rarely kills a healthy adult. The addax is also a specific species you can find in the Sahara, which is a large white antelope, and it can go nearly a year in the desert without drinking. The Dorcas gazelle is a North African gazelle that can also go for a long time without water. The central Sahara is estimated to include 500 species of plants, which is extremely low, considering the huge extent of the area. Plants, such as Acacia trees, palms, succulents, spiny shrubs, and grasses have adapted to the arid conditions by growing lower to avoid water loss by strong winds, and by storing water in their thick stems, to use it in dry periods. Human activities are more likely to affect the habitat in areas of permanent water, oases, or where water comes close to the surface. Here, the local pressure on natural resources can be intense. The remaining populations of large mammals have been greatly reduced by hunting for food and recreation. In recent years, development projects have started in the deserts of Algeria and Tunisia, using irrigated water, pumped from underground aquifers. These schemes often lead to soil degradation and salinization.
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