Images and ideas: how do we delimit South America?
Many people picture South America as football, carnival, rainforest and the Andes. These images are true in part but too simple. Geographers try to describe a region with facts.
A region is an area that is similar in some way. To delimit (draw the edges of) South America we can combine several features:
- Physical: one landmass south of the Isthmus of Panama, between the Pacific and Atlantic Oceans.
- Cultural: most people speak Spanish or Portuguese, a result of European colonisation from the 1500s; many Indigenous languages survive (Quechua, Guaraní, Aymara).
- Economic: many countries export raw materials (soy, beef, copper, oil, iron ore).
Each feature gives a slightly different edge. For example, "Latin America" also includes Mexico and Central America because of language. Choosing features is a decision, so different maps of "the region" can be correct.
Size: about 17.8 million km² (roughly 5 times India), about 430 million people.
Relief of South America (and North America)
The relief has three bands from west to east:
- The Andes: young fold mountains, about 7,000 km long, the longest range on land. They form where the Nazca plate (an ocean plate) sinks under the South American plate. The squeeze folds and lifts rock, and causes earthquakes and volcanoes. Highest peak: Aconcagua, about 6,960 m.
- Central lowlands and plains: the huge Amazon basin, the Orinoco plains (llanos) in the north and the Pampas and Gran Chaco in the south. Big rivers: Amazon, Paraná, Orinoco.
- Old highlands in the east: the Guiana Highlands and the Brazilian Highlands, worn down over very long times. Angel Falls, the highest waterfall (about 980 m), drops from the Guiana Highlands.
Same pattern in North America
North America also has young western mountains (the Rocky Mountains and coast ranges), central plains (the Great Plains and Mississippi lowland) and older, lower eastern mountains (the Appalachians). In the far north lies the very old Canadian Shield.
Climate zones and spatial patterns
Climate changes with latitude (distance from the equator), height and ocean currents:
- Equatorial rainforest (Amazon): hot (about 27 °C) and rainy all year, more than 2,000 mm rain.
- Savanna (llanos, Brazilian cerrado): a wet and a dry season, grass with scattered trees.
- Atacama Desert: one of the driest places on Earth. A cold ocean current (Humboldt) cools the air so it gives little rain, and the Andes block rain from the east.
- Pampas: mild, temperate grassland with rich soil, good for wheat and cattle.
- Patagonia: cold, dry and windy, in the rain shadow of the southern Andes.
- Mountain climate: in the Andes it gets about 6 °C colder for every 1,000 m. Farmers grow different crops at different heights (vertical zones).
Where people live
The pattern of people is the opposite of the forest: most live near the coasts and in a few huge cities (São Paulo, Buenos Aires, Rio de Janeiro, Lima, Bogotá). More than 80% of people are urban. Fast growth led to informal settlements (favelas) on city edges. The Amazon interior has few people.
Amazonia: economic use versus deforestation
The Amazon rainforest covers about 5.5 million km² and the Amazon River carries more water than any other river. The forest:
- stores huge amounts of carbon, slowing climate change;
- recycles water: trees release vapour that falls again as rain, even far away;
- is home to about one in ten known species and many Indigenous peoples.
Economic use: cattle ranching (the biggest cause of clearing), soybean farms, logging, gold and iron mining, oil, roads and hydroelectric dams. These bring jobs, food and export income.
Deforestation: about 17–20% of the original forest is already gone. Results: loss of species, more carbon dioxide, soil erosion, less rain, and conflicts over land. Scientists warn that near 20–25% loss some parts may dry into savanna (a tipping point).
Solutions: protected areas, Indigenous land rights, satellite monitoring of fires and clearing, agroforestry and sustainable harvesting (nuts, fruit), and buyers refusing products from newly cleared land.
Tornadoes and tropical cyclones: effects
A tropical cyclone (called a hurricane in the Atlantic, a cyclone in the Indian Ocean, a typhoon in the West Pacific) is a huge spinning storm, hundreds of km wide, that forms over warm sea (above about 26–27 °C). In the Americas they mostly hit the Caribbean, Central America and the south-east of the USA; South America is rarely hit. Effects: winds above 119 km/h, heavy rain and floods, a storm surge (sea pushed onto land), landslides, broken power and water supplies, crop loss.
A tornado is a small (often under 1 km wide) but extremely strong spinning column of air from a thunderstorm. It lasts minutes, but winds can exceed 300 km/h. Tornadoes are most common where warm, wet air meets cold, dry air over flat plains: the US "Tornado Alley" and the Pampas. Effects: houses torn apart along a narrow path, flying debris, injuries.
Along the Andes, earthquakes, volcanoes and tsunamis are the main hazards (for example the 2010 Chile earthquake). Warnings, strong buildings and shelters reduce the damage.
Key formulas and definitions
- Relief west → east: young fold mountains (Andes) → lowlands/plains → old highlands
- Fold mountains form where plates push together (Nazca plate under South American plate)
- Temperature falls about 6 °C per 1,000 m of height
- Cold current + rain shadow → desert (Atacama)
- Cyclone: forms over warm sea (> 26 °C), hundreds of km wide; tornado: over land, < 1 km wide, stronger winds
- Deforestation → less carbon storage, less rain, fewer species
Worked examples
1. Why are the Andes high and still growing, while the Brazilian Highlands are low?
The Andes are young fold mountains on an active plate edge: the Nazca plate keeps pushing under South America and lifts them. The Brazilian Highlands are very old rock far from any plate edge, worn down by rain and rivers for hundreds of millions of years.
2. Why is the Atacama so dry even though it is next to an ocean?
The cold Humboldt current cools the air above it, so the air cannot hold much moisture and rarely rises to form rain clouds. The Andes block moist winds from the east. Both together create a desert.
3. La Paz is at about 3,600 m. If the lowland at sea level nearby is 26 °C, estimate the temperature at La Paz.
Fall ≈ 6 °C per 1,000 m × 3.6 = about 21.6 °C. So 26 − 21.6 ≈ 4.4 °C. (Real average is about 8–10 °C because of local effects, but the rule shows why high cities are cool.)
4. Compare a tropical cyclone and a tornado.
Cyclone: forms over warm sea, hundreds of km wide, lasts days, causes storm surge and wide floods. Tornado: forms over land from a thunderstorm, under 1 km wide, lasts minutes, but has stronger winds along a narrow path.
5. Give two reasons why farmers clear the Amazon and two reasons to protect it.
Clear: grazing land for cattle; land for soybeans (both earn export money). Protect: the forest stores carbon and makes rain for farms far away; it holds a huge number of species and is home to Indigenous peoples.
6. Why do most South Americans live near the coast and not in the Amazon?
Colonial ports and trade grew on the coast; the coast has milder climate, flatter land and transport links. The rainforest is hot, wet, hard to build in and far from markets, so few people live there.
Common mistakes
- Thinking the whole continent is hot. The south (Patagonia) and the high Andes are cold.
- Saying the Atacama is dry because it is hot. It is dry because of a cold current and a rain shadow; it can be quite cool.
- Mixing up cyclones and tornadoes. A cyclone is huge and forms over the sea; a tornado is small and forms over land.
- Thinking all of the Amazon is untouched. About a fifth is already cleared, mostly for cattle and soy.