Key Points at a Glance

These key points summarise the landform facts most likely to appear in RPSC Geography answers on mountains, plateaus, plains and deserts.

1. Fold Mountains

   • Most common and highest mountain type
   • Formed when tectonic plates collide, compressing sedimentary strata into folds
   • Himalayas - India-Eurasia collision, ~50 Ma
   • Andes - Nazca-South American plates, ~25 Ma
   • Alps - Africa-Eurasia, ~35 Ma; Rockies - Farallon-North American, ~85-55 Ma

2. Block Mountains / Horsts

   • Form when land between parallel faults is uplifted
   • Raised block = Horst; sunken block = Graben
   • Vosges and Black Forest flank Rhine Graben, Germany
   • Vindhyas and Satpura (India); Sierra Nevada (USA)

3. Volcanic Mountains

   • Form by accumulation of lava, ash, and volcanic material
   • Shield volcanoes - broad, gentle slopes, basaltic lava: Mauna Loa (Hawaii, 4,170 m summit; Earth's largest active volcano by volume) and Mauna Kea (10,210 m from ocean floor, Earth's tallest mountain if measured from base)
   • Composite/Strato volcanoes - steep-sided, explosive, andesitic: Mt. Fuji (Japan, 3,776 m), Mt. St. Helens (USA)

4. Plateaus

   • Elevated flatlands with steep sides - often called "tablelands"
   • Intermontane - surrounded by mountains: Tibetan Plateau avg 4,500 m (world's highest)
   • Continental/Lava - basaltic flows: Deccan Plateau (600 m avg), Columbia Plateau (USA)
   • Piedmont - at mountain foothills: Appalachian Plateau, Malwa Plateau (India)

5. Plains

   • Low-lying, flat or gently undulating land
   • Structural - flat rock beds: Great Plains (USA, Canada)
   • Depositional/Alluvial - river sediments: Indo-Gangetic Plain, Mississippi Delta
   • Erosional - peneplains, pediplains (worn-down landscapes)
   • Coastal - Atlantic Coastal Plain, USA

6. Deserts

   • Cover ~33% of Earth's land surface when arid and semi-arid desert environments are counted together
   • Hot deserts (subtropical, 20°-30° lat.): Sahara (9.2 million km², world's largest hot desert), Arabian Desert (2.3 million km²), Thar (Rajasthan, 0.2 million km²)
   • Cold deserts: Gobi (Mongolia-China, 1.3 million km²), Patagonia (South America), Ladakh (India, rain shadow)

7. Australian Deserts - 2023 PYQ (2 marks)

   • RPSC asked the six major Australian deserts; Geoscience Australia lists 10 mainland deserts, with the top six forming the standard exam set
   • Great Victoria Desert - largest, 348,750 km²
   • Great Sandy (267,250 km²), Tanami (184,500 km²), Simpson (176,500 km²)
   • Gibson Desert (156,000 km²), Little Sandy Desert (111,500 km²)
   • All located in the interior and western regions, with the Simpson extending into the eastern interior

8. Rocky Mountains - PYQ 2021 (5 marks)

   • Extend 4,800 km from northern British Columbia (Canada) to New Mexico (USA)
   • Fold and thrust mountain system - formed during Laramide Orogeny (85-55 Ma)
   • Highest peak: Mount Elbert (4,399 m)
   • Form the Continental Divide - separates Pacific drainage from Atlantic/Gulf of Mexico drainage

9. Himalayan Mountain System

   • Spans ~2,400 km; contains 10 of the world's 14 peaks above 8,000 m
   • Himadri (Greater Himalayas, avg 6,000 m+; Mt. Everest 8,848.86 m at Nepal-China border)
   • Himachal (Lesser Himalayas, 3,700-4,500 m)
   • Shiwaliks (Outer Himalayas, 900-1,200 m)

10. Andes Mountains

    • World's longest continental mountain range - approximately 7,000 km along South America's western coast
    • Highest peak: Aconcagua (6,961 m) in Argentina - highest point in Western and Southern Hemispheres
    • Formed by subduction of the Nazca Plate under the South American Plate

11. Tibetan Plateau

    • World's highest and largest plateau - elevation averaging 4,500 m, area ~2.5 million km²
    • Called the "Roof of the World" and "Third Pole" because it contains extensive high-altitude glaciers and snowfields outside the polar regions
    • Source of major Asian rivers: Yangtze, Yellow River, Brahmaputra, Mekong, Indus, Salween

12. Desert Formation Mechanisms

    • Subtropical high pressure (Hadley Cell subsidence) - Sahara, Arabian Desert
    • Rain shadow effect - Gobi (blocked by Himalayas/Tibetan Plateau), Patagonia (Andes), Thar (Aravalli partially)
    • Cold ocean currents (coastal deserts) - Namib (Benguela Current, Africa), Atacama (Humboldt Current, Chile - world's driest non-polar desert; some areas have gone centuries without measurable rainfall)
    • Continental interiors (distance from oceanic moisture) - Central Asian steppes