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This revised chapter on NCERT Class 11 Geography India Physical Environment Chapter 2: Structure and Physiography Notes provides a clear overview of India’s geological formations, physiographic divisions, and landform evolution. These notes simplify complex concepts into easy-to-understand pointers. It is basically designed for exam preparation and quick revision of India’s structure, relief features, and geomorphological processes. You can also download a free PDF for effective exam preparation.
Contents
- 1 Introduction
- 2 Geological Structure of India
- 3 Physiography of India
- 4 The Northern and Northeastern Mountains
- 5 The Northern Plain
- 6 The Peninsular Plateau
- 7 The Indian Desert
- 8 The Coastal Plains
- 9 The Islands
- 10 Characteristics of India’s Structure and Physiography
- 11 Importance of India’s Structure and Physiography
- 12 Important Definitions in NCERT Notes Class 11 Geography India Physical Environment Chapter 2: Structure and Physiography
- 13 FAQs
Explore Notes of Class 11 India Physical Environment
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Introduction
The earth, including India, has a long geological history spanning about 460 million years, shaped by endogenic and exogenic forces. The Indian plate, once part of a larger Indo-Australian plate south of the equator, moved northward, influencing the subcontinent’s physical environment. This movement continues, interacting with plate tectonics to form current geological structures and active geomorphological processes.
Geological Structure of India
India’s geological structure results from ancient forces and plate movements, dividing the country into three main regions: the Peninsular Block, the Himalayas and other Peninsular mountains, and the Indo-Ganga-Brahmaputra Plain. These divisions align with physical features and reflect variations in rock types, age, and tectonic activity, impacting relief and landforms across the subcontinent.
- The Peninsular Block: An ancient, rigid complex of gneisses and granites, stable since the Cambrian period, with northern boundary from Kachchh to Rajmahal Hills; includes extensions like Meghalaya Plateau and Rajasthan desert; features rift valleys (Narmada, Tapi, Mahanadi), block mountains (Satpura), and residual hills (Aravali, Nallamala); shallow river valleys with low gradients; east-flowing rivers form deltas (Mahanadi, Krishna, Godavari, Kaveri).
- The Himalayas and Other Peninsular Mountains: Young, weak, and tectonically active, unlike the stable Peninsula; subjected to faults, folds, and thrusts; dissected by fast-flowing youthful rivers forming gorges, V-shaped valleys, rapids, and waterfalls.
- Indo-Ganga-Brahmaputra Plain: A geo-synclinal depression formed 64 million years ago during the Himalayan uplift; filled with sediments from the Himalayan and Peninsular rivers; average alluvial depth 1,000-2,000 m; influences fertile plains and relief variations.
Physiography of India
Physiography reflects structure, processes, and development stages, showing India’s diversity from the northern mountains to the southern plateaus and the central plains. Influenced by geological variations, it includes macro divisions like mountains, plains, plateaus, deserts, coasts, and islands, each with unique relief features shaped by erosion, deposition, and tectonics.
- Diverse relief: Northern rugged topography with mountains, valleys, gorges; southern stable tablelands with dissected plateaus and scarps; central vast plains.
- Major divisions: Northern and Northeastern Mountains, Northern Plain, Peninsular Plateau, Indian Desert, Coastal Plains, and Islands.
The Northern and Northeastern Mountains
The Northern and Northeastern Mountains comprise the Himalayas and the northeastern hills; these form parallel ranges acting as physical, climatic, drainage, and cultural barriers. They are stretching 2,500 km east-west with widths of 160-400 km, and they influence South Asia’s geoenvironment through orientation variations from northwest-southeast to north-south in different regions.
- Himalayas: Include Greater Himalayas, Trans-Himalayas, and Shiwaliks; central axial range; orientations vary (east-west in Darjiling-Sikkim, southwest-northeast in Arunachal Pradesh, north-south in Nagaland-Manipur-Mizoram).
- Role: Separate the Indian subcontinent from Central and East Asia; impact climate, drainage, and culture.
The Northern Plain
The Northern Plains are formed by alluvial deposits from the Indus, Ganga, and Brahmaputra rivers and extend 3,200 km east-west with widths of 150-300 km and depths up to 2,000 m. They are divided into Bhabar, Tarai, and alluvial plains (Bhangar, Khadar). They feature mature fluvial landforms and support dense populations due to fertile soils. Let’s understand about the northern plains more.
- Zones: Bhabar (8-10 km narrow belt with rock deposits where rivers disappear); Tarai (10-20 km marshy, swampy with re-emerging streams and dense vegetation); Alluvial plains (old Bhangar, new Khadar with sand bars, meanders, oxbow lakes).
- Brahmaputra specifics: Riverine islands, sand bars, periodic floods, braided streams; flows northeast-southwest then south into Bangladesh.
- Features: Featureless plain at 50-150 m elevation; fertile for crops like wheat, rice, sugarcane, jute; large deltas at river mouths (e.g., Sunderbans).
The Peninsular Plateau
An irregular triangle rising 150-900 m above plains, it’s an ancient stable landmass with plateau-like landforms like Hazaribagh, Ranchi, and Malwa. They slope west to east, featuring tors, rift valleys, rocky structures, and black soil in the northwest; divided into the Deccan Plateau, Central Highlands, and Northeastern Plateau based on relief. Let’s understand more about the Peninsula Plateau.
- General characteristics: Oldest landmass; recurrent uplift, submergence, faulting (e.g., Bhima fault); diverse relief with ravines, gorges (Chambal); east-flowing rivers form deltas, west-flowing lack them.
- Deccan Plateau: Bordered by Western Ghats (Sahyadri, Nilgiri, Anaimalai, Cardamom; average 1,500 m, higher south; peaks Anaimudi 2,695 m, Dodabetta 2,637 m), Eastern Ghats (discontinuous, eroded; Javadi, Nallamala, Mahendragiri), Satpura-Maikal-Mahadeo in the north; rivers originate in the Western Ghats.
- Central Highlands: West bounded by Aravali; Satpura scarped plateaus (600-900 m); relict mountains to Jaisalmer with barchans; elevation 700-1,000 m sloping north-northeast; Yamuna tributaries from Vindhyan-Kaimur; Banas from Aravali; eastern extension Rajmahal hills with minerals.
- Northeastern Plateau: Extension of Peninsula; fault between Rajmahal-Meghalaya from Himalayan forces; depression filled by rivers; Meghalaya subdivided into Garo, Khasi, Jaintia hills; Karbi Anglong in Assam; rich in coal, iron, sillimanite, limestone, uranium; highly eroded, bare surfaces (e.g., Cherrapunji).
The Indian Desert
Northwest of Aravali, also known as the Great Indian Desert or Marusthali are undulating with dunes, barchans, and an arid climate from low rainfall (<150 mm/year). Mesozoic sea origin evidenced by fossils; underlying Peninsular extension shaped by weathering, wind, and water deficit with ephemeral rivers.
- Features: Longitudinal dunes, barchans; mushroom rocks, shifting dunes, oases; northern slopes to Sindh, and southern slopes to Rann of Kachchh.
- Drainage: Luni River significant; streams disappear into lakes/playas with brackish water for salt.
- Climate: Low vegetation; high evaporation.
The Coastal Plains
India’s long coastline divides into western (submerged) and eastern (emergent) plains, shaped by geomorphological processes. Western narrow with ports, and the eastern is broader with deltas, providing navigation, fishing, and tourism opportunities. Here is more about the western coastal plains and eastern coastal plains.
- Western Coastal Plains: Submerged, narrow (broader north-south); natural ports (Kandla, Marmagao, Mangalore, Cochin); divisions: Kachchh-Kathiawar (Gujarat), Konkan (Maharashtra), Goan, Malabar (Karnataka-Kerala); no deltas; Kayals (backwaters) in Malabar for fishing, navigation (e.g., Nehru Trophy boat race).
- Eastern Coastal Plains: Emergent, broader, well-developed deltas (Mahanadi, Godavari, Krishna, Kaveri); fewer ports due to 500 km continental shelf; harbours like those on the east coast.
The Islands
The Indian Islands have two groups: the Bay of Bengal (Andaman-Nicobar) and the Arabian Sea (Lakshadweep). They are formed by submarine mountains or coral; they feature coral deposits, beaches, equatorial vegetation, and convectional rain.
- Bay of Bengal Islands: 572 islands/islets between 6°N-14°N, 92°E-94°E; groups Ritchie’s archipelago, Labyrinth; divided into Andaman (north), Nicobar (south) by Ten Degree Channel; elevated submarine portions, some volcanic (Barren Island active volcano); peaks Saddle (738 m), Diavolo (515 m), Koyob (460 m), Thuiller (642 m); coral beaches.
- Arabian Sea Islands: Lakshadweep-Minicoy between 8°N-12°N, 71°E-74°E; 36 coral islands, 11 inhabited; Minicoy is the largest (453 sq km); divided by Eleven Degree Channel (Amini north, Canannore south); storm beaches with pebbles, shingles.
Characteristics of India’s Structure and Physiography
Here are some of the key characteristics of India’s structure and physiography mentioned below:
- Geological diversity: Three divisions reflecting ancient stability (Peninsula) vs. young tectonics (Himalayas).
- Relief variations: High mountains north, stable plateaus south, fertile plains centre.
- River influences: Himalayan rivers are youthful with gorges; Peninsular rivers are shallow with deltas to the east.
- Tectonic impacts: Northward Indian plate movement forms the Himalayas and affects the filling of the plains.
- Climate roles: Mountains as barriers; plateaus with eroded surfaces; arid.
- Coastal contrasts: Submerged west for ports; emergent east for deltas.
Importance of India’s Structure and Physiography
India’s structure and physiography have shaped its environment, economy, and history. Geological stability provides mineral resources, while tectonic activity creates diverse landforms influence climate, agriculture, and settlements. Plains support population and farming, mountains protect and source rivers, plateaus offer resources, and deserts and coasts enable unique ecosystems and trade.
Important Definitions in NCERT Notes Class 11 Geography India Physical Environment Chapter 2: Structure and Physiography
Here we have explained the key concepts and terms of this chapter to make it easy for you to understand.
- Endogenic Forces: Internal Earth forces causing vertical movements, folds, and faults.
- Exogenic Forces: External forces like weathering and erosion shape surface features.
- Peninsular Block: Ancient rigid landmass of gneisses, granites, stable with residual mountains.
- Geo-synclinal Depression: A trough filled with sediments forming the Indo-Ganga-Brahmaputra Plain.
- Bhabar: A narrow belt of rock deposits where rivers disappear.
- Tarai: Marshy zone south of Bhabar with re-emerging streams.
- Bhangar/Khadar: Old/new alluvial deposits in plains.
- Kayals: Backwaters in the Malabar coast for navigation and fishing.
- Ten Degree Channel: A water body separating Andaman and Nicobar.
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FAQs
India is divided into the Peninsular Block (ancient stable), the Himalayas and other Peninsular Mountains (young tectonic), and the Indo-Ganga-Brahmaputra Plain (sedimentary depression).
The divisions are the Northern and Northeastern Mountains, the Northern Plain, the Peninsular Plateau, the Indian Desert, the Coastal Plains, and the Islands.
It is an ancient, stable landmass subjected to uplift, submergence, and faulting, with plateau landforms and an east-west slope influencing river flow.
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