Learn first: The biosphere and natural zones, The World Ocean and the oceans
The three continents of the Southern Hemisphere — Africa, Australia and Antarctica — were once parts of a single supercontinent, Gondwana. That is why ancient platforms form their base. Yet their nature differs greatly, mainly because of position: Africa lies around the equator, Australia around the tropic and Antarctica around the South Pole. Exams ask you to identify a continent from a description and to know its records and natural zones. Study each continent with the same plan: position → structure and relief → climate → waters → zones → population.
Africa covers about 30 million km², making it the second largest continent after Eurasia. The equator crosses it almost through the middle, and both the Tropic of Cancer and the Tropic of Capricorn pass over it. So Africa is the hottest continent, and its natural zones repeat symmetrically north and south of the equator. In the north the Mediterranean and the Strait of Gibraltar separate it from Europe; in the north-east the Suez Canal and the Red Sea separate it from Asia.
Relief. The base of the continent is the ancient African platform, so high plateaus dominate — lower in the north-west and higher in the south-east ("High Africa"). In the north-west are the young fold Atlas mountains. In the east is the East African Rift System, giant cracks in the crust holding deep lakes (Tanganyika) and volcanoes. The highest point is the extinct volcano Kilimanjaro (5,895 m).
Minerals: gold and diamonds (South Africa and others), copper (Zambia, DR Congo), bauxite (Guinea), oil and gas (Nigeria, Libya, Algeria).
Africa’s northernmost point is at about 37° N and its southernmost at about 35° S. Roughly how long is the continent from north to south?
Climate. Africa lies in seven climate belts: equatorial, two subequatorial, two tropical and two subtropical. The Sahara is the world’s largest hot desert: dry tropical air dominates all year, sinks, and no rain forms. On the south-west coast the cold Benguela Current has produced the coastal Namib Desert.
Waters. The Nile is the longest river in the world; it crosses the Sahara and forms a delta where it enters the Mediterranean. The Congo has the greatest flow in Africa and crosses the equator twice, so it is full all year. Other rivers are the Niger, the Zambezi (with Victoria Falls) and the Orange. Lakes: Victoria is Africa’s largest lake; Tanganyika is tectonic and very deep; Chad is shallow and changes in area.
Natural zones (arranged symmetrically):
Population. Africa’s population is growing fast; its natural increase is the highest in the world. Arabs and Berbers live in the north, Negroid peoples south of the Sahara. The most populous country is Nigeria.
Description: "The continent stretches almost equally north and south of the equator, its zones are symmetrical, and savanna covers the largest area." Which continent is it?
Position. The smallest continent (about 7.7 million km²), wholly in the Southern and Eastern hemispheres; the Tropic of Capricorn crosses its middle. The continent holds one state, the Commonwealth of Australia.
Relief. Mostly plains and plateaus (an ancient platform); in the east the low-to-medium Great Dividing Range; the highest point is Mount Kosciuszko (2,228 m). The area around Lake Eyre lies below sea level. Resources: iron ore, coal, bauxite, gold, uranium.
Climate. Australia is the driest continent. The reasons: most of it lies in the tropical belt under subtropical high pressure; the eastern mountains block moist trade winds from the Pacific; and the cold West Australian Current flows along the west coast. Deserts occupy the centre.
Waters. There are few rivers; the main one is the Murray with its tributary the Darling. Many rivers dry up in the dry season — these are called creeks. The continent is rich in artesian water, used for livestock.
Wildlife. Australia was isolated from other continents for a very long time, so it has many endemics — species found nowhere else: kangaroo, koala, platypus, echidna, eucalyptus. Along the north-east coast runs the world’s largest coral structure, the Great Barrier Reef.
Oceania is the group of islands in the central and south-western Pacific. It is divided into Melanesia ("black islands"), Micronesia ("small islands") and Polynesia ("many islands"). By origin islands are continental (New Guinea, New Zealand), volcanic (Hawaii) or coral (atolls). New Zealand is a mountainous island country with volcanoes and geysers.
Position and nature. Antarctica covers about 14 million km² around the South Pole. It is the coldest continent and the highest on average, because it is covered by a thick ice sheet (more than 2 km on average, over 4 km in places). Most of the world’s fresh water is stored in this ice. The highest point is the Vinson Massif. The lowest temperature was recorded at Vostok Station (−89.2 °C). Strong cold katabatic winds blow from the centre of the continent towards the coast.
Life is poor: mosses and lichens on the coast; animals — penguins, seals and birds — find their food in the ocean.
Discovery. In 1820 by the expedition of F. Bellingshausen and M. Lazarev. R. Amundsen was the first to reach the South Pole (1911); R. Scott arrived about a month later.
Legal status. Under the 1959 Antarctic Treaty the continent belongs to no state and is used only for peaceful and scientific purposes; there is no permanent population, only research stations.
At the foot of Kilimanjaro (about 1,000 m) it is +25 °C. What is the temperature at the summit (5,895 m) if it falls by 6 °C per km?