Second-largest continent (after Asia), straddling the equator and lying largely within the tropics. Land Africa forms a plateau between the Atlantic and Indian Oceans. Its highest features include the Atlas and Ahaggar mountains in the NW, the Ethiopian Highlands in the E, the Drakensberg Mountains in the S, and Mount Kilimanjaro. Lake Assal in the Afar Depression of Djibouti is the lowest point at -153m (-502ft). The huge sunken strip in the E is the African section of the Great Rift Valley. The Sahara stretches across the N, while the Kalahari and Namib are smaller deserts in the S and SW. Madagascar lies off the SE coast. Structure and geology Africa is composed largely of ancient metamorphic rocks overlain with Tertiary, Mesozoic and Palaeozoic sediments. The mountains of the NW are folded sedimentary material, roughly contemporaneous with the Alps. The Great Rift Valley, formed by the progressive movement of the Arabian Peninsula away from Africa, is mainly igneous in the N and older Precambrian in the S. Lakes and rivers The Rift Valley contains Lakes Albert, Malawi, and Tanganyika. Victoria to the E is Africa's largest lake; Lake Chad which shrinks to a salt pan in dry periods, lies in the S Sahara. Rivers include the Nile, Niger, Congo, and Zambezi. Climate and vegetation Much of the continent is hot and (outside the desert areas) humid. The belt along the Equator receives more than 250cm (100in) of precipitation a year and is covered by rainforest. The forest gives way both in the N and S to areas of acacia and brush, and then through savanna to desert. The N strip of the continent and the area around the Cape have a Mediterranean climate. Peoples Africa is home to more than 13% of the world's population, divided into more than 700 distinct tribes and groups. North of the Sahara Arabs and Berbers predominate, while to the S tribes include the Fulani, Galla, Hausa, Hottentots, Igbo, Masai, Mossi, San, Yoruba, and Zulu. Indians and Europeans also form significant minorities. Africa is relatively thinly populated and c.75% of the population is rural. Economy Agriculture is restricted in central Africa by the large expanse of rainforest, although cash crops such as cocoa, rubber, and peanuts are grown on plantations. Along the N coast, crops such as citrus fruits, olives, and cereals are grown. The Sahara is largely unproductive, supporting only a nomadic herding community. East and S Africa are the richest agricultural areas. Apart from South Africa, the continent is industrially underdeveloped. Mining is the most important industry. Zambia has the world's largest deposits of copper ore. Bauxite is extracted in W Africa, and oil is produced in Nigeria, Libya, and Algeria. South Africa is rich in minerals: gold, diamonds, and coal being the most important. Recent History Before the 1880s, Europeans were, except in South Africa, largely confined to the coastal regions. By the end of the 19th century, the whole continent, except for Liberia and Ethiopia, was under foreign domination either by European powers, or (in the N) by the Ottoman Empire. Starting in the 1950s the colonies rapidly secured their independence, but this process brought unrest and instability to much of Africa. A major cause of unrest was, and continues to be, the artificial boundaries created by colonialism. Lasting democracy proved difficult to achieve in many countries and military rule is prevalent. Area: c.30 million sq km (11.7 million sq mi) Highest mountain Kilimanjaro (Tanzania) 5895m (19,340ft) Longest river Nile 6670km (4140mi) Population 812 million Largest cities Lagos (8,029,200); Cairo (7,764,700); Kinshasa (6,301,100); Alexandria (3,328,196); Casablanca (3,595,100); Algiers (2,562,428) See also articles on individual countries.