Classification of Landforms
Major and Minor Landforms
Earth's landforms are classified into two broad categories:
- Major Landforms: Mountains, Plateaus, and Plains
- Minor Landforms: Buttes, Canyons, Valleys, Basins, Gorges, and Dunes
Extreme Landforms on Earth
- Highest Point: Mount Everest (8,850 meters / 29,035 feet) - Located on the Nepal-Tibet border in the Great Himalayas
- Lowest Point (Land): Dead Sea shore (-430 meters below sea level) - Border of Jordan and Israel
- Deepest Point: Mariana Trench (11,034 meters deep) - Located in the South Pacific Ocean
I. Mountains and Hills
Definition and Characteristics
An uplifted portion of the Earth's surface that rises prominently above the surrounding area is called a hill or mountain.
Distinction between Hills and Mountains:
- Hill: A land surface that rises higher than surrounding area, typically with elevation less than 600 meters
- Mountain: A steep elevated landform with an elevation generally exceeding 600 meters above the surrounding terrain
General Characteristics of Mountains:
- Steep slopes and considerable height
- Narrow summit compared to base
- Form continuous ranges or chains
- Influence climate by blocking wind and moisture
- Source of rivers and streams
- Rich in forest resources and minerals
- Less suitable for agriculture due to steep slopes
Types of Mountains
1. Fold Mountains
Fold mountains are formed by the folding of Earth's crust due to compressive forces when two tectonic plates collide. These are the most common and highest mountain ranges on Earth.
Formation Process:
- Formed at convergent plate boundaries
- Sedimentary rocks in geosynclines (large depressions) are compressed
- Layers of rock fold into wave-like patterns (anticlines and synclines)
- Process takes millions of years
Examples:
- The Himalayas (Asia) - Youngest and highest fold mountains, formed by collision of Indian and Eurasian plates
- The Andes (South America) - Longest continental mountain range (7,000 km)
- The Alps (Europe) - Major mountain system extending across 8 countries
- The Rockies (North America) - Extends from Canada to New Mexico
- The Atlas Mountains (Africa) - Separates the Mediterranean from the Sahara
The Himalayas - World's Youngest Fold Mountains
The Himalayas were formed approximately 50 million years ago when the Indian plate collided with the Eurasian plate. They are still rising at a rate of about 5mm per year due to ongoing tectonic activity.
2. Block Mountains (Horst) and Rift Valleys (Graben)
Block mountains are formed when great blocks of Earth's crust are raised or lowered by vertical movement along faults during the final stages of mountain building. These are also called Fault-Block Mountains.
Formation Process:
- Formed by tensional forces that cause faulting
- Blocks of crust move vertically along fault lines
- Uplifted blocks form horsts (block mountains)
- Lowered blocks form grabens (rift valleys)
Examples of Block Mountains:
- Vosges Mountains (France)
- Black Forest (Germany)
- Sierra Nevada (USA)
- Vindhya and Satpura (India)
Examples of Rift Valleys:
- Rhine Valley (Europe) - Between Vosges and Black Forest
- East African Rift Valley - Extends from Jordan to Mozambique
- Narmada Valley (India)
3. Volcanic Mountains
Volcanic mountains are formed by the accumulation of volcanic material (lava, ash, and other debris) ejected from the Earth's interior. They are also called Mountains of Accumulation.
Formation Process:
- Magma rises through cracks in Earth's crust
- Repeated eruptions deposit layers of lava and ash
- Material accumulates around the vent
- Forms cone-shaped mountains
Types of Volcanic Mountains:
- Active Volcanoes: Currently erupting or showing signs of eruption
- Dormant Volcanoes: Not currently erupting but may erupt again
- Extinct Volcanoes: No longer capable of erupting
Examples:
- Mount Mauna Loa (Hawaii, USA) - World's largest active volcano by volume
- Mount Popa (Myanmar) - Extinct volcano, sacred pilgrimage site
- Mount Fuji (Japan) - Dormant stratovolcano and Japan's highest peak
- Mount Vesuvius (Italy) - Famous for destroying Pompeii in 79 AD
- Mount Kilimanjaro (Tanzania) - Africa's highest peak, dormant volcano
- Barren Island (India) - India's only active volcano in Andaman Sea
4. Residual or Relict Mountains
These are remnants of ancient mountains that have been worn down by erosion over millions of years. They are also called Mountains of Circumdenudation or Dissected Mountains.
Formation Process:
- Originally tall fold or block mountains
- Eroded by wind, water, ice, and temperature changes
- Only the resistant core remains
- Usually have rounded tops due to extensive weathering
Characteristics:
- Old and worn-down mountains
- Rounded peaks and gentle slopes
- Rich in minerals due to exposure of ancient rocks
- Lower elevation compared to other mountain types
Examples in India:
- Aravalli Range - World's oldest mountain range (over 1.8 billion years old)
- Nilgiri Mountains (Tamil Nadu) - Part of Western Ghats
- Rajmahal Hills (Jharkhand)
- Eastern Ghats - Discontinuous range along east coast
- Western Ghats - UNESCO World Heritage Site, biodiversity hotspot
- Parasnath Hills (Jharkhand) - Highest peak of Chota Nagpur Plateau
Note on Aravalli Range
The Aravalli Range is the oldest fold mountain range in India and one of the oldest in the world. It runs for approximately 692 km from Gujarat to Delhi through Rajasthan and Haryana.
II. Plateaus
Definition and Characteristics
A plateau is an elevated flat-topped landform that rises sharply above the surrounding area on at least one side. Plateaus are also called tablelands.
Key Features:
- Elevated flat or gently rolling surface
- Height varies from few hundred to several thousand meters
- Surrounded by steep slopes or cliffs (escarpments)
- Cover about 33% of Earth's land surface
- Often older than mountains in geological age
Types of Plateaus
1. Intermontane Plateaus:
Enclosed by mountain ranges on all sides
- Tibetan Plateau - Highest plateau in the world, called "Roof of the World"
- Bolivian Plateau (South America)
- Mexican Plateau
2. Piedmont Plateaus:
Situated at the foot of mountains, bordered by plains on one side
- Malwa Plateau (India)
- Piedmont Plateau (USA)
3. Continental Plateaus:
Large plateaus rising from plains or sea
- Deccan Plateau (India) - Oldest plateau in India
- African Plateau - Covers most of Africa
- Arabian Plateau
- Western Plateau (Australia)
4. Volcanic Plateaus:
Formed by successive volcanic eruptions
- Deccan Traps (India) - Formed by volcanic activity
- Columbia Plateau (USA)
Famous Plateaus of the World
Tibetan Plateau
- Highest plateau in the world
- Average elevation: 4,500 meters above sea level
- Known as "The Roof of the World"
- Area: Approximately 2.5 million square kilometers
- Source of major Asian rivers (Indus, Brahmaputra, Yangtze, Mekong)
Important Plateaus in India:
- Deccan Plateau - Triangular plateau in southern India
- Chota Nagpur Plateau - Rich in minerals (iron, coal, manganese, mica)
- Malwa Plateau - Between Aravalli and Vindhya ranges
- Marwar Plateau - In western Rajasthan
- Bundelkhand Plateau - In Madhya Pradesh
- Meghalaya Plateau - Part of Peninsular Plateau
Economic Importance of Plateaus
Plateaus are highly valuable for human civilization due to various reasons:
Mineral Resources:
- Extremely rich in mineral deposits
- African Plateau: Famous for gold and diamond mining
- Chota Nagpur Plateau (India): Huge reserves of iron ore, coal, manganese, mica, and bauxite
- Deccan Plateau: Rich in manganese and iron ore
- Many major mining areas worldwide are located in plateau regions
Other Benefits:
- Hydroelectric Power: Rivers descending from plateaus ideal for power generation
- Agriculture: Volcanic plateaus have fertile soil (black soil in Deccan)
- Tourism: Scenic beauty attracts visitors
- Grazing Lands: Suitable for livestock rearing
- Climate Moderation: Pleasant climate at higher elevations
III. Plains
Definition and Characteristics
Plains are large stretches of flat or gently rolling land with very gentle slopes. They are the most extensive landforms on Earth's surface.
Key Features:
- Generally not more than 200 meters above mean sea level
- Gentle gradient (slope less than 5 degrees)
- Uniform elevation with minimal relief
- Cover about 55% of Earth's land surface
- Most densely populated landforms
Formation of Plains
1. Depositional Plains (Aggradational):
Formed by deposition of materials by various agents
- Alluvial Plains: Formed by river deposits
- Indo-Gangetic Plain (India)
- Mississippi Plain (USA)
- Yangtze Plain (China)
- Tigris-Euphrates Plain (Iraq)
- Glacial Plains: Formed by glacial deposits
- North European Plain
- Great Plains of North America
- Lacustrine Plains: Formed by lake deposits
- Coastal Plains: Formed along sea coasts
- Eastern Coastal Plain (India)
- Western Coastal Plain (India)
- Atlantic Coastal Plain (USA)
- Loess Plains: Formed by wind-blown deposits
- Loess Plateau (China)
2. Erosional Plains (Degradational):
Formed by erosion and wearing down of highlands
- Peneplains: Nearly flat surfaces formed by long-term erosion
- Pediplains: Plains formed in arid regions
- Glacial Plains: Plains carved by glaciers
3. Structural Plains:
Formed by Earth movements (tectonic activity)
- Result of uplift or subsidence of land
- Often have horizontal rock strata
- Example: Great Plains of USA
Formation Process of Alluvial Plains (Most Common)
Alluvial plains are the most extensive and important type of plains:
Step 1: Rivers flow down mountain slopes
Step 2: Water erodes rocks and soil from mountains (erosion)
Step 3: Rivers carry eroded material (stones, sand, silt) downstream (transportation)
Step 4: As river velocity decreases in plains, materials are deposited (deposition)
Step 5: Repeated flooding deposits layers of alluvium over thousands of years
Step 6: Extensive flat plains are formed with fertile soil
Famous Plains of the World
Asian Plains:
- Indo-Gangetic Plain - Formed by Indus, Ganga, and Brahmaputra rivers; one of the most densely populated regions
- Yangtze Plain (China) - Major rice-growing region
- Mesopotamian Plain (Iraq) - Cradle of civilization
- Manchurian Plain (China)
- Coastal Plains of India - Eastern and Western coastal plains
Other Continents:
- Mississippi-Missouri Plain (North America)
- Great Plains (North America) - Grassland region
- Pampas (South America) - Grassland plains in Argentina
- Amazon Basin (South America)
- North European Plain (Europe)
- Canterbury Plains (New Zealand)
Importance of Plains
Plains are the most useful landforms for human habitation and economic activities:
Agricultural Importance:
- Most fertile regions with deep alluvial soil
- Flat land suitable for mechanized farming
- Adequate water supply from rivers
- Major food-producing regions of the world
- Support intensive agriculture and high crop yields
Human Settlement:
- Most densely populated regions globally
- Easy construction of houses and buildings
- Flat land facilitates transportation and communication
- Development of cities and industries
- Availability of water resources
Economic Activities:
- Development of transport networks (roads, railways)
- Industrial centers due to flat land and connectivity
- Trade and commerce hubs
- Tourism and recreational activities
Comparison of Major Landforms
| Feature | Mountains | Plateaus | Plains |
|---|---|---|---|
| Elevation | Very high (>600m) | Moderate to high (300-1000m+) | Low (<200m) |
| Surface | Steep, rugged peaks | Flat top, steep sides | Flat or gently rolling |
| Slope | Very steep | Steep at edges, flat on top | Gentle or no slope |
| Agriculture | Limited due to slope | Moderate; terracing needed | Highly suitable |
| Population | Sparsely populated | Moderately populated | Densely populated |
| Resources | Forests, water, minerals | Rich in minerals | Fertile soil, water |
| Climate | Cold at peaks, varies with altitude | Moderate, cooler than plains | Generally warm, varies by latitude |
| Transport | Difficult, requires tunnels/bridges | Moderate difficulty | Easy and cost-effective |