Major Physiographic Divisions of the World: CBSE Class 6 Geography Notes

The surface of our planet is not a uniform, flat expanse; it rises into towering peaks, extends into wide flat plains, and elevates into rugged tablelands. In geography, these major physical features are called landforms or physiographic divisions, sculpted over millions of years by powerful natural processes. Understanding these landforms helps us see why human cultures, agriculture, transport networks, and climatic zones vary dramatically across the globe.

How Landforms are Created: Internal and External Forces

The Earth's crust is dynamic and constantly changing through two fundamental processes: internal processes and external processes.

Internal processes originate deep within the Earth. The intense heat inside causes tectonic plates to move, leading to the gradual upliftment or sinking of the Earth's surface. These movements are responsible for building immense structures like mountain ranges and deep ocean trenches.

External processes take place on the surface of the Earth. They continuously wear down and rebuild the landscape through two main actions:

• Erosion: The natural wearing away of the land surface by running water, wind, and moving ice (glaciers).
• Deposition: The process of dropping or laying down eroded rock particles, silt, and soil in lower areas, rebuilding new surfaces.

Together, these two continuous actions ensure that the Earth's surface is constantly being sculpted into distinct elevations and depressions.

Mountains: Types, Anatomy, and Importance

A mountain is any natural elevation of the Earth's surface that rises significantly higher than the surrounding area. Mountains typically have a broad base, steep slopes, and a small, pointed summit or peak. Because temperature drops as altitude increases, very high mountains remain permanently covered in snow and ice, harboring vast frozen rivers known as glaciers.

Mountains are classified into three major types based on their mode of origin:

• Fold Mountains: Formed when two tectonic plates push against each other, causing the rock strata of the Earth's crust to crumple and fold upwards. Young Fold Mountains, such as the Himalayas in Asia and the Alps in Europe, have rugged relief and sharp, conical peaks. Old Fold Mountains, such as the Aravalli Range in India and the Urals in Russia, have gentle slopes and rounded tops because millions of years of erosion have worn them down.
• Block Mountains: Created when large crustal areas are broken and displaced vertically along fault lines. The elevated blocks are called horsts, while the sunken, lowered blocks are known as graben. Examples include the Rhine Valley and the Vosges Mountain system in Europe.
• Volcanic Mountains: Formed by the accumulation and cooling of molten magma, ash, and lava thrown out during volcanic eruptions. Prominent examples include Mount Kilimanjaro in Africa and Mount Fujiyama in Japan.

Mountains act as the world's water towers. Major perennial rivers originate from mountain glaciers, providing fresh water for drinking, irrigation, and hydroelectric power generation downstream.

Plateaus: Elevated Tablelands and Mineral Storehouses

A plateau is an elevated, flat-topped landform that rises abruptly above the surrounding terrain. It has one or more sides with steep slopes and resembles a large, raised table on the Earth's surface. Plateaus can vary in height from a few hundred meters to several thousand meters.

The Deccan Plateau in India is one of the oldest geological plateaus on Earth. The highest plateau in the world is the Tibetan Plateau, often referred to as the 'Roof of the World', with an impressive altitude ranging between 4,000 and 6,000 meters above sea level.

Plateaus are of immense economic importance:

• Rich Mineral Deposits: Most of the world's major mining areas are situated in plateau regions. The African plateau is globally renowned for gold and diamond extraction, while India's Chota Nagpur Plateau holds vast reserves of iron ore, coal, and manganese.
• Waterfalls: Because rivers plunge down the steep edges of plateaus, these regions contain striking waterfalls, such as the Hundru Falls on the Subarnarekha River and the Jog Falls in Karnataka.
• Fertile Lava Soils: Many plateaus, including parts of the Deccan Traps, are composed of weathered volcanic black soil, which retains moisture exceptionally well and is ideal for growing cotton and sugarcane.

Plains: Low-Lying Basins and Cradles of Civilization

Plains are vast stretches of relatively flat, low-lying land, generally rising no more than 200 meters above mean sea level. While some plains are extremely level, others are gently rolling or undulating.

Most extensive plains are formed by the action of rivers and their tributaries. As rivers cascade down mountains, they erode rock and soil. When the slope flattens out, the river loses velocity and deposits its carried load of sand, silt, and clay (collectively known as alluvium) along riverbanks and valley floors. Over thousands of years, these repeated flood deposits form flat, nutrient-rich floodplains.

Plains are the most densely populated regions on Earth for three distinct reasons:

• Agricultural Productivity: Deep alluvial soils combined with abundant water supply make plains exceptionally fertile for intensive farming.
• Ease of Transport and Construction: Flat terrain makes laying railway tracks, building highways, and constructing urban infrastructure far simpler and cheaper than in mountainous terrain.
• Favourable Living Conditions: Moderate climate and easy access to water have historically made plains, such as the Indo-Gangetic Plains in India and the Yangtze River Basin in China, the centers of human civilization.

Landforms and Human Life: Adapting to Diverse Relief

Human lifestyles, settlements, and occupations are directly shaped by the physiographic division people inhabit. Life in rugged mountain regions is physically demanding due to harsh weather, steep slopes, thin soil covers, and limited transport connectivity. Mountain communities often practice terrace farming, carving stepped fields into hillsides to cultivate crops and prevent soil erosion.

In contrast, plains offer ideal conditions for large-scale urbanisation, industrial development, and mechanized agriculture. However, high population density in plains often leads to acute challenges, such as pollution, loss of agricultural land to concrete infrastructure, and flood vulnerability.

Understanding landforms teaches us the importance of sustainable living—conserving fragile mountain ecosystems, protecting fertile plain soils from degradation, and responsibly mining plateau minerals without destroying local biodiversity.

Key takeaways

• Landforms are continuously shaped by internal tectonic forces (uplift and sinking) and external surface forces (erosion and deposition).
• Mountains are classified into Fold, Block, and Volcanic types, and serve as vital reservoirs of fresh water via glacial river sources.
• Young Fold Mountains have steep, pointed peaks, whereas Old Fold Mountains have rounded summits due to long-term weathering.
• Plateaus are elevated, flat-topped tablelands that contain rich mineral deposits, fertile black lava soils, and major waterfalls.
• Plains are flat, alluvium-rich river deposits that host the highest human population densities due to ease of transport, construction, and fertile farmland.

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