The Sahara Desert is located in the northern part of Africa and covers about 9，600，000 square kilometers or roughly 32% of the continent. It is bounded in the east by the Red Sea and it stretches west to the Atlantic Ocean.To the north， the Sahara Desert’s northern boundary is the Mediterranean Sea， while in the south it ends at the Sahel， an area where the desert landscape transforms into a semi-arid tropical savanna.
Since the Sahara Desert makes up nearly 32% of the African continent， the Sahara is often cited as the world’s largest desert. This is not entirely true， however， as it is only the world’s largest hot desert. Based on the definition of a desert， as an area receiving less than 250mm of precipitation per year， so the world’s largest desert is actually the continent of Antarctica.
Although hot and extremely dry today， it is believed that the Sahara Desert has undergone various climatic shifts for the last few hundred thousand years. For example， during the last glaciation， it was larger than it is today because precipitation in the area was low. But from 8000 BC to 6000 BC， precipitation in the desert increased because of the development of low pressure over ice sheets to its north. Once these ice sheets melted， however， the low pressure shifted and the northern Sahara dried out but the south continued to receive moisture due to the presence of a monsoon.
Most of the people living in the Sahara today do not live in cities; instead， they are nomads who move from region to region throughout the desert.Because of this， there are many different nationalities and languages in the region and Arabic is most widely spoken. For those who do live in cities or villages on fertile oases， crops and the mining of minerals like iron ore and copper are important industries that have allowed population to grow.
stretch /stretʃ/ v. 绵延;伸展;延续
Fields and hills stretched out as far as we could see.
precipitation /prɪ'sɪpɪ'teɪʃn/ n. 降水量（包括雨、雪、冰等）;沉淀
moisture /'mɔɪstʃər/ n. 水汽;水分
nomad /'noʊmæd/ n. 游牧民;游牧生活英语阅读