Terra & Time

Physiography refers to the physical geography or natural features of the Earth’s surface, including landforms, terrain types, and the processes that shape them. In the context of India, physiography reflects the country’s diverse landscape shaped by complex geological and geomorphological processes.

India’s physical landscape is a diverse mosaic sculpted over millions of years by geological processes, including tectonic movements and erosion. These processes have created distinctive landforms across the subcontinent, leading to a classification of India into six major physiographic divisions:

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This region comprises the vast Himalayan Mountain system and the Northeastern hills. The Himalayas are a young fold mountain chain, tectonically active and rich in geological diversity. These ranges stretch approximately 2,500 km from northwest to southeast, forming a formidable natural barrier between the Indian subcontinent and Central and East Asia. Their width varies between 160 to 400 km.

The Himalayan ranges include:

• Greater Himalayas (Himadri): The innermost and most continuous range with an average elevation of over 6,000 meters. It houses some of the world’s tallest peaks, including Mount Everest and Kanchenjunga.
• Lesser Himalayas (Himachal): Situated south of the Himadri, these ranges are lower in elevation (average 3,500–5,000 meters) and include valleys such as the Kangra and Kullu.
• Shiwalik Hills: The outermost range composed of unconsolidated sediments brought by rivers. These hills are prone to landslides and erosion.

The orientation of these ranges’ changes across regions:

• East-West in Darjeeling and Sikkim
• Southwest-Northwest in Arunachal Pradesh
• North-South in Nagaland, Manipur, and Mizoram

The Himalayas influence India’s climate by obstructing cold winds and facilitating monsoon rainfall. They also act as a drainage divide, with numerous rivers like the Indus, Ganga, and Brahmaputra originating from their glaciers.

The Northeastern Hills, extensions of the Himalayan ranges, include the Patkai, Naga, Lushai, and Mizo Hills. These are rich in biodiversity and feature complex terrain, making connectivity and infrastructure development challenging but ecologically significant.

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These vast alluvial plains were formed by the deposition of sediments brought by the Indus, Ganga, and Brahmaputra River systems. They extend about 3,200 km from east to west and 150–300 km in width, with alluvial depths ranging from 1,000–2,000 meters.

Subdivisions of the Northern Plains:

• Bhabar: A porous zone of coarse sediments at the Himalayan foothills where rivers disappear underground.
• Tarai: Marshy land just south of Bhabar where rivers re-emerge and create a fertile, vegetated landscape.
• Alluvial Plains:
  • Khadar: Newer deposits, closer to river courses, highly fertile.
  • Bhangar: Older alluvium, higher and less fertile than Khadar.

The plains are characterized by high fertility and flatness, making them ideal for agriculture and dense settlements. Landforms like ox-bow lakes, levees, and braided streams are common. The Brahmaputra plains have distinctive riverine islands and are prone to frequent flooding and shifting river channels.

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This ancient landmass, composed mainly of igneous and metamorphic rocks, rises from 600–900 meters and slopes gently from west to east. It has experienced tectonic stability but also witnessed faulting, which led to the formation of rift valleys like the Narmada and Tapi.

Key Subdivisions:

• The Deccan Plateau: Enclosed by the Western Ghats (steep and continuous) and Eastern Ghats (discontinuous and eroded). Rivers like Godavari, Krishna, and Kaveri originate here. The Nilgiri Hills, where the Eastern and Western Ghats meet, host the peak Dodabetta.
• The Central Highlands: Include the Malwa Plateau, Bundelkhand, and Baghelkhand. The region contains mineral-rich formations and features ravines (e.g., Chambal) and gorges.
• The Northeastern Plateau: Includes the Meghalaya and Karbi-Anglong Plateaus, formed due to faulting and uplift. The Garo, Khasi, and Jaintia Hills are rich in rainfall and minerals. The plateau experiences intense erosion, particularly in Cherrapunji.

Features like tors, dykes, spurs, and scarped edges are common, reflecting a complex geological history.

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Also known as the Thar Desert, it lies northwest of the Aravalis. This arid region is characterized by:

• Longitudinal sand dunes and barchans shaped by wind activity
• Sparse vegetation and low precipitation (below 150 mm annually)
• Ephemeral rivers, such as the Luni, which often vanish in inland basins
• Oases and playas with brackish water used for salt extraction

Fossils and marine deposits suggest that this region was under the sea during the Mesozoic era. The landforms are the result of wind erosion, creating features like mushroom rocks and deflation hollows.

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India’s coastline stretches over 7,500 km and is divided into:

• Western Coastal Plains: A narrow and submerged coastal strip with natural harbours like Mumbai, Marmagao, and Cochin. It includes the Konkan coast, Goan coast, and Malabar coast. The kayals or backwaters of Kerala support fishing, tourism, and navigation.
• Eastern Coastal Plains: A broad and emergent coast with major river deltas of the Mahanadi, Godavari, Krishna, and Kaveri. These regions are fertile but have fewer harbors due to a wide continental shelf. Prominent deltas like the Godavari delta are agriculturally rich.

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India’s islands fall into two main groups:

• Andaman and Nicobar Islands (Bay of Bengal): Made up of about 572 islands, these are largely volcanic and tectonic in origin. The Ten Degree Channel separates the Andamans from the Nicobars. The only active volcano in India, Barren Island, is located here. Peaks like Saddle Peak and Mount Thuiller rise from these islands. These areas also host coral reefs and equatorial vegetation.
• Lakshadweep Islands (Arabian Sea): Comprising 36 coral islands, these are located 220–440 km off the Kerala coast. Formed by coral atolls, they are flat and low-lying. Divided by the Nine Degree Channel, Minicoy is the largest island. These islands have unique ecosystems and are prone to storms and erosion.

From snow-capped mountains to sun-drenched deserts, fertile plains to lush islands, India’s physiographic divisions reflect its rich geological past and diverse natural heritage. Each region plays a vital role in shaping the country’s environment, economy, and culture.

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