Topic 74: Mountains, Plateaus, Plains & Deserts

Study Material

Paper Paper II

Unit 3

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, 10,210 m from ocean floor — Earth's largest by volume) - 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 - 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) - Australia has six major deserts covering ~44% of its land - Great Victoria Desert — largest, 424,400 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
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" — stores 37% of world's freshwater in glaciers - 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; some areas no rainfall in 400 years) - Continental interiors (distance from oceanic moisture) — Central Asian steppes

Key facts

Fold Mountains — Most common and highest mountain type — Formed when tectonic plates collide, compressing sedimentary strata into folds — Himalayas
Volcanic Mountains — Form by accumulation of lava, ash, and volcanic material — Shield volcanoes
Plateaus — Elevated flatlands with steep sides — often called "tablelands" — Intermontane
Deserts — Cover ~33% of Earth's land surface
Australian Deserts — 2023 PYQ (2 marks) — Australia has six major deserts covering ~44% of its land — Great Victoria Desert — largest, 424,400 km²

Key Points at a Glance

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, 10,210 m from ocean floor — Earth's largest by volume)
- 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
- 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)
- Australia has six major deserts covering ~44% of its land
- Great Victoria Desert — largest, 424,400 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
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" — stores 37% of world's freshwater in glaciers
- 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; some areas no rainfall in 400 years)
- Continental interiors (distance from oceanic moisture) — Central Asian steppes

Introduction and Syllabus Scope

Mountains, plateaus, plains and deserts form the core landform portion of RPSC Geography, and the examiner expects classification, formation process, distribution and precise examples. According to the RPSC official Mains scheme 2018, General Studies Paper II carries 200 marks.

Exam Importance

Topic 74 is the most persistently tested landform topic in Paper II Geography. It appeared in all five exam years (2013, 2016, 2018, 2021, 2023) with a cumulative 22 marks at 4.4 marks/year average.

The topic covers four major landform types - mountains, plateaus, plains, and deserts - focusing on types, formation mechanisms, and global distribution. In the RPSC syllabus, this belongs to Paper II, Unit III, Earth Science (Geography & Geology), where the world and India sections both include broad physical features such as mountains, plateaus, plains, lakes and glaciers, and the Rajasthan section includes broad physical features, major physiographic regions, rivers and lakes.

PYQ Pattern

RPSC has favoured two specific sub-areas:

Specific mountain ranges with geographic features (Rocky Mountains, 2021, 5 marks)
Specific distribution questions (six deserts of Australia, 2023, 2 marks)

The 2026 pattern eliminates 2-mark questions, so expect 5-mark and 10-mark questions requiring descriptions with examples and distributions. A 5-mark answer should still carry enough location data, formation logic and one or two measurements to look grounded rather than generic.

Exam Strategy

5-mark answers: Define the landform type -> state formation mechanism -> give 3-4 specific examples with locations and measurements
10-mark answers: Cover all sub-types with classification, formation process, distribution pattern, and economic significance

For GEO, the answer must also be quotable: begin with the direct classification or mechanism, then add examples such as Himalayas, Rockies, Tibetan Plateau, Indo-Gangetic Plain, Sahara, Gobi, Thar and Australian deserts. Avoid writing a loose paragraph that names landforms without showing why they belong to a particular type.

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PREDICTED Predicted RAS Questions

Based on PYQ trends and 2026 syllabus analysis

1 5M Describe the major geographical features of the Rocky Mountains. 5 marks · 50 words

Model Answer

The Rocky Mountains extend 4,800 km from British Columbia (Canada) to New Mexico (USA), formed 85–55 Ma during the Laramide Orogeny. Highest peak: Mount Elbert (4,399 m). They form the Continental Divide separating Pacific drainage (Columbia, Colorado rivers) from Atlantic/Gulf drainage (Missouri, Arkansas). Rich in gold, silver, molybdenum; Yellowstone supervolcano located within the system.

~50 words • 5 marks