Learn first: Africa, Australia and Antarctica
North and South America are the two continents of the Western Hemisphere. Their nature follows a common "plan": young high mountains in the west, old low mountains and plateaus in the east, and broad plains in between. The differences come mainly from position: South America lies around the equator, while North America stretches up to the Arctic. Exams ask you to recognise the continents from a description, to know the records (longest mountain system, river with the greatest flow, driest desert) and to explain cause and effect.
South America covers about 18 million km². The equator crosses its northern part, so most of the continent lies in the Southern Hemisphere. The Tropic of Capricorn crosses its middle. In the north the narrow Isthmus of Panama joins it to North America; the Panama Canal cut through the isthmus links the Atlantic and Pacific oceans.
North America covers about 24 million km² including islands. It lies wholly in the Northern and Western hemispheres and runs from the Arctic to the tropics, so it has almost every climate belt from arctic to tropical. The world’s largest island, Greenland, belongs geographically to this continent.
For Europe both continents were "discovered" after the voyage of Christopher Columbus in 1492. The name "America" honours Amerigo Vespucci, who argued that these lands were a new continent. Before that they were home to Native American peoples and to ancient civilisations such as the Maya, the Aztecs and the Incas.
A city lies at 23° S, 43° W. In which hemispheres and on which continent is it?
In the west are the Andes, the longest mountain system in the world (about 9,000 km). They are young fold mountains formed as the Pacific plate sinks beneath the continent, so volcanoes and strong earthquakes are common. The highest peak is Aconcagua (6,961 m), which is also the highest point of the Western Hemisphere.
In the east, on an ancient platform, lie the Brazilian and Guiana Highlands; between them is the Amazon Lowland (one of the largest in the world), together with the Orinoco and La Plata lowlands.
Minerals follow the structure: non-ferrous metals in the Andes (copper in Chile, tin and silver in Bolivia), iron ore on the platform shields (Brazil) and oil in sedimentary basins (Venezuela).
South America is the wettest continent. The reasons: much of it lies in equatorial and subequatorial latitudes; the trade winds bring moisture from the Atlantic; and the Andes hold this air back so that the moisture falls over the whole continent.
On the west coast the cold Peru (Humboldt) Current chills the air from below, the air does not rise and there is almost no rain. This produced the Atacama, the driest desert in the world.
Waters: the Amazon has the greatest flow and the largest basin of any river; others are the Paraná, the Orinoco and the Uruguay. Angel Falls is the highest waterfall in the world (979 m). Lake Titicaca is one of the highest navigable lakes in the world (about 3,800 m).
Natural zones:
On the coast the air is +22 °C. Lake Titicaca is at about 3,800 m. Using the lapse-rate rule, what is the temperature above the lake?
In the west are the Cordillera — young fold mountains with volcanoes and earthquakes. The highest peak is Denali (6,190 m, in Alaska; also known as McKinley). Inside the Cordillera lie plateaus; the Colorado River has cut the Grand Canyon into the Colorado Plateau. Death Valley lies below sea level and is one of the hottest places on Earth.
In the east are the old, worn-down, low Appalachians, with coal deposits. In the centre are the Central Plains, the Great Plains and the Mississippi Lowland, and in the north the Canadian Shield with many traces of ancient glaciation.
Minerals: non-ferrous metals and gold in the Cordillera, coal in the Appalachians, oil and gas on the Gulf of Mexico coast and in Alaska, iron and nickel ores on the Canadian Shield.
The Cordillera block Pacific air, so the interior is continental. The relief runs north–south, with no east–west barrier: Arctic and tropical air masses enter freely and collide. The results are sudden weather changes, tornadoes and blizzards. Hurricanes arrive from the Atlantic and the Gulf of Mexico. The warm Gulf Stream flows off the east coast, the cold Labrador Current in the north-east and the cold California Current in the west.
Waters: the Mississippi with its tributary the Missouri forms the continent’s longest river system; others are the Mackenzie, Yukon, Colorado and Columbia. The Great Lakes — Superior (one of the largest freshwater lakes in the world), Michigan, Huron, Erie and Ontario — were formed by glacial and tectonic processes. Niagara Falls lies between Erie and Ontario.
Natural zones from north to south: Arctic desert → tundra → taiga → mixed and broadleaf forest → prairies (grassland) → deserts (south-west) → subtropical and tropical forest (Florida, Central America). In the interior the zones also change along the meridians, because moisture decreases from east to west.
Description: "The longest mountain system in the west, plateaus in the east; the wettest continent; the river with the greatest flow." Which continent is it?