World Physical Geography — Mountains, Oceans, Plains, Rivers & Natural Regions

Overview

World physical geography forms the structural backbone of GS1 — it provides the framework for understanding climate, biomes, resource distribution, geopolitics, and human settlements. This chapter covers the major physiographic features of the world: mountain systems, ocean basins, plains, rivers, and natural regions, along with the distribution of critical resources.

Major Mountain Systems

1. The Himalayas (Asia)

• Type: Fold mountains — formed by collision of the Indian Plate and the Eurasian Plate
• Formation: Began ~50 million years ago (Eocene epoch); still rising at ~5 mm/year
• Length: ~2,400 km; spans India, Nepal, Bhutan, Pakistan, China
• Highest peak: Mount Everest — 8,849 m (remeasured by China-Nepal survey, 2020)
• Significance: Source of major rivers (Ganga, Brahmaputra, Indus, Yangtze, Mekong); climatic barrier blocking cold Central Asian winds; orographic rainfall on windward side

2. The Andes (South America)

• Type: Fold mountains (subduction of Nazca Plate under South American Plate)
• Length: ~7,000 km — longest continental mountain range in the world
• Highest peak: Aconcagua — 6,961 m (Argentina); highest peak outside Asia
• Key features: "Ring of Fire" volcanism (Cotopaxi, Chimborazo); source of Amazon River tributaries; Atacama Desert rain shadow on western flank; Lithium Triangle in the Puna plateau

3. The Rockies (North America)

• Type: Fold and thrust mountains (subduction of Pacific plates under North America)
• Length: ~4,800 km; stretches from British Columbia (Canada) to New Mexico (USA)
• Highest peak: Mount Elbert — 4,401 m (Colorado)
• Significance: Continental divide — rivers flow either to the Pacific or Atlantic; source of Colorado, Columbia, and Missouri rivers

4. The Alps (Europe)

• Type: Fold mountains — formed by collision of African and Eurasian plates
• Length: ~1,200 km across France, Switzerland, Italy, Austria, Germany, Slovenia
• Highest peak: Mont Blanc — 4,808 m (France/Italy border)
• Significance: Divides Mediterranean Europe from northern Europe; Rhine, Rhône, Po, and Danube river systems originate here; major centre of winter tourism

5. The Urals (Russia/Kazakhstan)

• Type: Old fold mountains (ancient Hercynian orogeny — ~300 million years ago)
• Orientation: North-South; serves as the conventional boundary between Europe and Asia
• Height: Low, worn down by erosion; highest — Mount Narodnaya — 1,895 m
• Significance: Rich mineral deposits — iron ore, copper, chromium, gold, coal

6. The Atlas Mountains (North Africa)

• Type: Fold mountains (African and Eurasian plate interaction)
• Location: Morocco, Algeria, Tunisia
• Highest peak: Toubkal — 4,167 m (Morocco)
• Significance: Barrier between Sahara Desert and Mediterranean coastal belt; separates Atlantic-Mediterranean climate from Saharan arid zone

Ocean Basins

1. Pacific Ocean — World's Largest and Deepest

• Area: ~165 million km² — covers about one-third of Earth's surface
• Deepest point: Challenger Deep, Mariana Trench — 10,935 m (Greenaway et al., 2021 measurement; earlier surveys placed it at 10,984 m; both values appear in sources)
• Key features: "Ring of Fire" — 75% of world's volcanoes; tectonically most active ocean; Pacific Ocean currents (ENSO — El Niño/La Niña); major fishing grounds (Peru/Humboldt Current)
• Straits: Bering Strait (connects Pacific to Arctic); Drake Passage (connects Pacific to Atlantic)

2. Atlantic Ocean

• Area: ~106 million km²; second largest
• Key feature: Mid-Atlantic Ridge — the world's longest mountain chain (~16,000 km), running north-south through the Atlantic; marks diverging tectonic plates; active volcanism (Iceland sits on the ridge)
• Currents: Gulf Stream (warm, northward) — moderates Western Europe's climate; Labrador Current (cold, southward)
• Strategic chokepoints: Strait of Gibraltar (Mediterranean access), Strait of Dover, English Channel

3. Indian Ocean

• Area: ~70.5 million km²; third largest
• Key characteristics: Only ocean entirely in the Eastern Hemisphere; warmest ocean; strongly influenced by monsoon winds — reversal of winds between summer (SW monsoon) and winter (NE monsoon)
• Key basins: Arabian Sea, Bay of Bengal, Red Sea, Persian Gulf
• Significance: ~80% of world's seaborne oil trade passes through; Strait of Hormuz, Strait of Malacca, and Bab-el-Mandeb are critical chokepoints

Major Plains

Continental Shelves and Their Resources

Continental shelf = submerged extension of a continent, typically to ~200 m depth.

• Resources: Oil and natural gas (70% of offshore production from shelves); fisheries (90% of world's marine fish caught on shelves); sand, gravel, and heavy minerals; potential manganese nodules on deeper slopes
• UNCLOS definition: A coastal state's continental shelf extends 200 nautical miles (nm) under EEZ, and potentially up to 350 nm if the shelf extends beyond
• Key shelves: North Sea (major European oil/gas); Persian Gulf shelf (Saudi Arabia, UAE, Iran); India's western shelf (Mumbai High — major oil field)

Major World Rivers

Natural Regions of the World

Distribution of Fossil Fuel Reserves

Oil Reserves

• Middle East share: Approximately 48% of world proven oil reserves (OPEC and US EIA data — OPEC member countries hold ~79% of world reserves and the Middle East constitutes ~60% of OPEC production capacity; the ~48% figure refers specifically to the Middle East sub-region)
• Top countries: Venezuela (~18%), Saudi Arabia (~17%), Canada (~10%), Iran (~9%), Iraq (~9%)
• Key note: The "Middle East" is often used loosely — precise % varies by source and whether gas condensates are included

Natural Gas Reserves

• Russia: World's largest proven natural gas reserves (~19% of global total) — Siberian fields (Urengoy, Yamburg, Bovanenkovo)
• Iran & Qatar: Share the South Pars/North Dome gas field — world's largest single gas field
• USA: World's largest gas producer (shale gas revolution via hydraulic fracturing)

Coal Reserves

• USA: Largest proven coal reserves (~22% of world total)
• Russia: Second (~15%); followed by Australia (~14%), China (~13%), India (~10%)
• India's coal: Jharkhand, Odisha, Chhattisgarh — Gondwana coal (the best quality)

Global Freshwater Distribution

• Total freshwater: Only 2.5% of all water on Earth is freshwater (97.5% is saline)
• Of that 2.5% freshwater:
  • 68.7% is locked in glaciers and ice caps (Antarctic ice sheet, Greenland)
  • 30.1% is underground (groundwater in aquifers)
  • Only ~0.3% is surface freshwater (lakes, rivers, swamps)
  • Rivers hold just ~2% of surface freshwater
• India's freshwater stress: India has 4% of world's freshwater but 18% of world's population
• Transboundary rivers: 276 international river basins covering 60% of Earth's land area — source of water geopolitics (Nile, Mekong, Indus)

Exam Strategy

For Prelims:

• Mariana Trench depth: ~10,935 m to 10,984 m depending on survey (Challenger Deep)
• Longest mountain range: Andes (~7,000 km) — continental; Mid-Atlantic Ridge is longest submarine range
• Largest ocean: Pacific; deepest: Pacific (Mariana Trench); warmest: Indian Ocean
• Amazon: largest by discharge; Nile: longest river
• Freshwater: 2.5% of total water; 68.7% of freshwater in glaciers; rivers hold ~0.3% of total freshwater
• Coal reserves: USA > Russia > Australia; Oil: Middle East ~48%; Gas: Russia > Iran > Qatar

For Mains:

• Link mountain formation to plate tectonics — Alpine-Himalayan belt vs. Circum-Pacific belt
• Ocean basins: connect to trade routes, monsoon, fisheries, and geopolitics
• Indo-Gangetic Plain: agriculture, groundwater depletion, population density — connect to food security
• Freshwater scarcity: glaciers (climate change), groundwater (over-extraction), transboundary rivers (geopolitics)
• River system: link Nile to GERD dispute (GS2), Mekong to China's dam diplomacy, Amazon to deforestation