Ch 6: Major Landforms of the Earth
UPSC tests landform classification (mountains, plateaus, plains), formation processes, and their geographical distribution across continents with emphasis on structural vs. erosional features.
6.1 Introduction: What are Landforms?
Establishes foundational definition: landforms as natural features of Earth's surface shaped by internal (tectonic) and external (erosional) forces. UPSC rarely asks direct definition questions at Prelims, but this underpins understanding of subsequent sections. Focus on the dual classification framework (endogenic vs. exogenic processes) rather than memorizing the intro verbatim. No traps here, but skipping this leaves conceptual gaps in answering 'why do landforms exist' questions.
6.2 Major Landforms: Mountains
Directly testable: fold mountains (Alps, Himalayas, Rockies), block mountains (Vosges, Rhine Valley), and volcanic mountains with their formation mechanisms. UPSC has tested mountain classification and examples (e.g., distinguishing fold from block mountains). Key facts: fold mountains form from compression, block mountains from faulting, volcanic mountains from lava accumulation. Trap: confusing 'young fold mountains' (Himalayas, still rising) with 'old fold mountains' (Appalachians, eroded). Specific terms to master: horsts, grabens, rift valleys. Know at least 3 examples per type and their continents.
Horsts are elevated crustal blocks bounded by faults; grabens are depressed blocks between parallel faults. The Rhine Valley is a graben; the Vosges Mountains form a horst. These structures define block mountain topography.
Young fold mountains (Himalayas, Alps, Andes, Rockies): still rising, highly folded, steep slopes, frequent earthquakes. Old fold mountains (Appalachians, Urals, Scottish Highlands): eroded, rounded peaks, low relief. Formation time differs by hundreds of millions of years.
6.3 Major Landforms: Plateaus
UPSC frequently tests plateau identification and classification (structural/tectonic plateaus vs. erosional plateaus). Key examples: Tibetan Plateau, Deccan Plateau (India), Colorado Plateau. Distinguishing features: elevated, flat-topped, escarpments. Trap: many students confuse plateaus with mountains; the difference is the flat top and internal structure. Deccan Plateau is especially important for Indian geography context (basaltic composition, monsoon impact). Learn formation: uplift of large crustal blocks, lava outpouring, or erosion. At least 2–3 global examples with their characteristics.
The Deccan Plateau covers approximately 500,000 km² of peninsular India; formed by massive basaltic lava flows 65–66 million years ago during the Cretaceous-Paleogene boundary. Thickness exceeds 2,000 metres in places.
6.4 Major Landforms: Plains
Plains are extensively tested because they have high human population density and agricultural significance. UPSC asks about plain formation (river depositional plains, glacial plains, wind-formed plains) and their distribution. Key examples: Indo-Gangetic Plain, Amazon Plain, North European Plain. Distinguish between structural plains (formed by tectonic uplift) and depositional/erosional plains. Trap: assuming all plains are flat—some have gentle slopes. Know the role of rivers, glaciers, and wind in shaping plains. This section directly impacts UPSC questions on agriculture, settlement, and civilizations tied to plains.
The Indo-Gangetic Plain extends 2,400 km from Indus to Brahmaputra; width varies 240–320 km; depositional plain formed by three major river systems; supports over 1 billion people, highest population density globally.
6.5 Landforms and Human Activities
Low direct testability at Prelims but useful context for mains and optional answers. Covers how humans exploit landforms (mining in mountains, agriculture in plains, irrigation on plateaus). Not a priority for pure geography Prelims but valuable for answering 'why' questions in longer-format sections. Skip detailed memorization; focus on understanding the relationship between landform type and economic activity (e.g., steep mountains → forestry, plains → agriculture).
6.6 Distribution of Landforms across Continents
UPSC frequently tests continental landform distributions and their geological explanations. Key facts: Asia has the highest mountains (Himalayas, Rocky Mountains in North America), Africa has large plateaus, Europe has old fold mountains. Map-based questions are common—know major mountain ranges, plateaus, and plains by continent and their approximate locations. Trap: mixing up Andes (South America) with Rockies (North America) or confusing mountain ranges across Asia. This section often appears in map-based Prelims questions. Practice identifying landforms by continent and relating to tectonic plate boundaries.
Asia: Himalayas (10 highest peaks), Tibetan Plateau, Amazon Plain. Africa: East African Plateau, Rift Valley system. Europe: Alps, Carpathians (young folds), Scandinavian Shield (old platform). Americas: Rockies, Andes, Great Plains.