South America experiences a wide range of climates — from equatorial rainforests to cold deserts and high-altitude tundra. This diversity is due to its latitudinal span, ocean currents, and mountains.

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🌍 9.1 Climate Zones of South America

1. Equatorial Climate

• Region: Amazon Basin (Brazil, Peru, Colombia, Venezuela).
• Features:
  • Hot & wet throughout the year.
  • Dense tropical rainforest.
  • Heavy convectional rainfall.

2. Tropical Savanna (Wet & Dry)

• Region: Llanos (Venezuela, Colombia), Campos & Cerrado (Brazil).
• Features:
  • Distinct wet and dry seasons.
  • Tall grasses, scattered trees.

3. Desert Climate

• Region: Atacama (Chile, Peru), Sechura (Peru), Patagonian Desert (Argentina).
• Features:
  • Extremely dry due to rain shadow of Andes & Humboldt Current.

4. Temperate Climate

• Region: Pampas (Argentina, Uruguay).
• Features:
  • Mild climate, fertile soils.
  • Wheat, maize, cattle grazing.

5. Mediterranean Climate

• Region: Central Chile (Santiago, Valparaíso).
• Features:
  • Hot, dry summers and mild, wet winters.
  • Grapes, wine industry.

6. Cool/Cold Climate

• Region: Patagonia (southern Argentina, Chile).
• Features:
  • Cold steppe and tundra.
  • Sheep grazing, sparse population.

7. Highland Climate (Altitudinal Zonation)

• Region: Andes Mountains.
• Features:
  • Tierra caliente (Hot land): up to 1,000 m → bananas, sugarcane.
  • Tierra templada (Temperate land): 1,000–2,000 m → coffee, maize.
  • Tierra fría (Cold land): 2,000–3,500 m → potatoes, barley.
  • Tierra helada (Frozen land): above 3,500 m → grazing, snow.

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🌊 9.2 Major Ocean Currents

1. Humboldt Current (Peru Current)

• Cold current along west coast (Peru, Chile).
• Causes: Desert climate (Atacama, Sechura).
• Creates rich fishing grounds (anchovies, sardines).

2. Brazil Current

• Warm current flowing south along Brazil’s coast.
• Warms the southeast coast, increases humidity.

3. Falkland (Malvinas) Current

• Cold current from south Atlantic, flows northward along Argentina.
• Meets Brazil Current → rich fishing zones.

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🌍 9.3 El Niño & La Niña

🔹 El Niño

• Periodic warming of central & eastern Pacific Ocean.
• Effects in South America:
  • Peru, Ecuador → heavy rainfall, floods.
  • Fisheries collapse (anchovy industry).
  • Atacama Desert blooms (rare).
• Global Effects: Droughts in Australia/India, floods in North America, disrupted monsoons in India.

🔹 La Niña

• Opposite of El Niño → cooling of Pacific waters.
• Effects in South America:
  • Heavy rainfall in Amazon & northern South America.
  • Drier conditions in west coast (Peru, Chile).
• Global Effects: Stronger Indian monsoon, floods in South Asia, drought in South America.

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📌 UPSC Key Pointers

1. Equatorial Climate → Amazon Basin (hot & wet year-round).
2. Mediterranean Climate → Central Chile (wine industry).
3. Atacama Desert → driest place on Earth due to Andes + Humboldt Current.
4. Humboldt Current → rich fisheries, cold; Brazil Current → warm; Falkland Current → cold.
5. Altitudinal zonation in Andes → Tierra caliente, templada, fría, helada.
6. El Niño → floods in Peru & Ecuador; collapse of fisheries.
7. La Niña → heavy rains in Amazon, dry Peru/Chile.