South America: position, relief, climate and waters

South America’s climate is shaped by solar radiation, relief, air masses and ocean currents. There are six climate zones; from north to south: subequatorial, equatorial, subequatorial, tropical, subtropical and temperate; in the mountains there are altitudinal belts. The equatorial zone is very humid: over 3 500 mm of rain a year, with temperature +24…+25 °C all year. In the subequatorial zone summer is humid and winter dry. Trade winds bring 1 500–2 000 mm to the east of the Brazilian Plateau but only 250–500 mm near the Andes. On the Pacific coast the cold Peru Current brings no rain: so one of the world’s driest deserts, the Atacama, formed, and plants get moisture from fog and dew. In the south the Pacific coast has heavy rain all year (2 000–3 000 mm), while the east has a dry temperate-continental climate. South America is the wettest continent. The Amazon is the biggest river in the world by basin (about 7 million km²) and volume, about 6 400–7 000 km long (depending on how it is measured), with over 500 tributaries; because of ocean tides water flows upstream in the lower course (the pororoca). On a tributary of the Paraná lie Iguazú Falls, about 2 700 m wide, and on the Churún River in the Orinoco basin the world’s highest waterfall, Angel Falls (979 m). The largest lake is Maracaibo; Titicaca in the Andes (3 812 m) is one of the highest large freshwater lakes.