NCERT
Every NCERT book that matters for UPSC — open a book, then a chapter. Learn each chapter's concepts, then how UPSC tests them — with diagrams, flowcharts and the past questions to attempt.
0% read
← India: Physical Environment — all chaptersStructure and Physiography
Start here: why this chapter matters
In simple wordsChapter 1 gave India's address. This chapter is the tour of the house: a high, rugged wall of mountains along the north, a huge flat courtyard of river mud in front of it, an old, worn, raised platform in the south, a sandy corner in the west, a seafront on both sides, and two sets of islands offshore. And it explains why each part looks the way it does — because each was built at a different time, from different rock.
Structure means the rocks and how they were built and deformed; physiography means the surface shapes — mountains, plains, plateaus — that result. NCERT puts it as: physiography is the outcome of structure, process and stage of development. The earth is about 4,600 million years old, and the shapes we see were made by endogenic (inner) and exogenic (surface) forces and by the movement of plates.
- Comes after Chapter 1 (location and extent) and leads into Chapter 3 (Drainage System): the mountains and the plateau tilt decide where every river flows.
- Sets up Chapter 4 (Climate) — the Himalaya and the Western Ghats steer the monsoon — and Chapter 6 (Hazards): earthquakes in the young Himalaya, floods in the plains, tsunamis on the coasts.
- Builds on the Physical Geography book: plate tectonics and the Indian plate's journey (Chapter 4), the earth's interior and volcanoes (Chapter 3), and rivers, wind and coastal landforms (Chapter 6).
- UPSC: GS1 Geography (physiography is the base of almost every India-geography answer); Prelims love hills, peaks, passes, channels and their order on the map.
| Word | What it means here |
|---|---|
| Structure / geology | The kinds of rock in a region and how they were formed, folded or broken |
| Physiography / relief | The shape and height of the land surface |
| Gneiss, granite | Very old, hard crystalline rocks that make up the Peninsula's base |
| Fold mountain | Mountains made when layers of rock are squeezed and buckled — the Himalayas |
| Relict / residual mountain | The worn-down stump of an old mountain range, e.g. the Aravali |
| Rift valley | A long trough that sank between two faults — the Narmada and Tapi valleys |
| Alluvium | Sand, silt and clay laid down by rivers |
| Geosyncline | A long, sinking trough in the crust that fills up with sediment |
| Delta / estuary | A delta is a fan of sediment at a river mouth; an estuary is a mouth where the sea flushes the sediment away |
Reading the unit page and the opening questions (pages 1–2)
- Unit II, Physiography, covers this chapter (structure, relief, physiographic divisions) and the next (drainage and watersheds).
- The opening asks you to map the phases of the Indian plate's movement: it lay south of the equator, was once joined to the Australian plate, broke away and moved north while Australia moved south-east. That story is told in detail in the live Physical Geography Chapter 4 — this chapter uses its consequences.
At a glance — the six ideas to carry away
- Three geological divisions: Peninsular Block (old, rigid) · Himalayas (young, folded) · Indo-Ganga-Brahmaputra Plain (alluvium).
- Six physiographic divisions: mountains · northern plain · peninsular plateau · desert · coastal plains · islands.
- Himalayas: parallel ranges, ≈ 2,500 km long, 160–400 km wide — a physical, climatic, drainage and cultural divide.
- Northern plain from north to south: Bhabar → Tarai → Bhangar (old) and Khadar (new) alluvium.
- The Deccan tilts east; the Western Ghats are high and continuous, the Eastern Ghats low and broken; they meet at the Nilgiris.
- West coast submerged (narrow, ports, no deltas); east coast emergent (broad, deltas). A&N separated by the Ten Degree Channel.
1. Three geological divisions
In simple wordsImagine an old, hard table (the Peninsula) being slowly pushed against a rug (the sea-floor sediments to the north). The rug crumples into folds — the Himalayas. The dip between the table and the crumpled rug fills with crumbs swept off both — the northern plain.
The northward movement of the Indian plate still continues and keeps shaping the subcontinent. Through the interplay of endogenic and exogenic forces and plate movement, India divides into three geological divisions that broadly follow its physical features: (i) the Peninsular Block, (ii) the Himalayas and other Peninsular mountains, (iii) the Indo-Ganga-Brahmaputra Plain.
| Peninsular Block | Himalayas and other mountains | Indo-Ganga-Brahmaputra Plain | |
|---|---|---|---|
| Rocks | Very ancient gneisses and granites | Young, folded sedimentary rocks | River alluvium, 1,000–2,000 m deep |
| Nature | Rigid and stable since the Cambrian | Young, weak and flexible | Once a geosynclinal depression, now filled |
| Movements | Vertical movements and block faulting: rift valleys of the Narmada, Tapi and Mahanadi; the Satpura block mountains; part of the west coast submerged | Still active: faults, folds and thrust plains | Gradually filled by Himalayan and Peninsular rivers |
| Mountains | Relict and residual: Aravali, Nallamala, Javadi, Veliconda, Palkonda, Mahendragiri | Tectonic in origin | — |
| Rivers | Shallow valleys, low gradients; east-flowing rivers form deltas (Mahanadi, Krishna, Kaveri, Godavari) | Fast, youthful: gorges, V-shaped valleys, rapids, waterfalls | Mature: meanders, ox-bow lakes, braided channels |
Where does the Peninsular Block end in the north? NCERT draws its boundary as an irregular line from Kachchh along the western flank of the Aravali near Delhi, then roughly parallel to the Yamuna and Ganga to the Rajmahal hills and the Ganga delta. Karbi Anglong and the Meghalaya plateau in the north-east and Rajasthan in the west are extensions of it; the north-eastern part is cut off from the Chotanagpur plateau by the Malda fault in West Bengal, and in Rajasthan desert sand covers the block.
Reading NCERT Figure 2.1 — A Gorge (page 9)
- A narrow, deep valley with near-vertical rocky walls and a white, rushing stream far below; terraced fields cling to the slope on the left.
- It illustrates the text's point that Himalayan rivers are in a youthful stage — cutting down fast because the land is still rising. Gorges, V-shaped valleys, rapids and waterfalls are the evidence (UPSC 2012 asked exactly which features prove the Himalaya are young).
⤵ Physiography = structure + process + stage
Structureold rigid block · young folded belt · sediment-filled trough
Processendogenic uplift, folding, faulting + exogenic erosion and deposition
Stageyouthful Himalayan rivers · mature plains · old, worn plateau
Northrugged mountains, peaks, deep gorges
Middlevast flat plain
Southdissected tableland, scarps, denuded rocks
NCERT check — the ‘64 million years’ dateNCERT says the plain's trough reached its maximum development during the third phase of Himalayan formation, about 64 million years ago. That date sits awkwardly with the live Physical Geography Chapter 4, where India meets Asia only 40–50 million years ago, and the third uplift phase is usually placed far more recently. Quote ‘the third phase of Himalayan uplift’ and the 1,000–2,000 m alluvium; don't build an answer on the 64 Ma figure.
Beyond NCERT (asked by UPSC)
- The Aravali are India's oldest fold mountains (UPSC 1979), Pre-Cambrian in age — UPSC 2001's answer key put them at about 670 million years — use that in the exam, but note that geologists date the Aravali–Delhi mountain building far earlier, to the Proterozoic (well over a billion years ago). Its highest point is Guru Shikhar (≈ 1,722 m) on Mount Abu.
- UPSC 1997 matched ages: Aravali — Pre-Cambrian; Deccan Traps — Cretaceous–Eocene; Narmada–Tapi alluvium — Pleistocene.
- The Himalayas rose from sediments of the Tethys Sea (UPSC 1991).
2. Six physiographic divisions
In simple wordsIf you flew from Kashmir to Kanniyakumari you would see the land change like chapters in a book: snowy mountains, then endless flat fields, then rocky uplands, with a desert off to the right, beaches on both sides, and islands far out at sea. NCERT names these six chapters.
The north has a vast expanse of rugged mountains with peaks, valleys and deep gorges; the south is a stable tableland of dissected plateaus, denuded rocks and scarps; between them lies the vast north Indian plain. On these macro differences India has six physiographic divisions: (1) the Northern and North-eastern Mountains, (2) the Northern Plain, (3) the Peninsular Plateau, (4) the Indian Desert, (5) the Coastal Plains, (6) the Islands.
Reading NCERT Figure 2.2 — India: Physical (page 10)
- A relief map with four height classes: above 900 m, 600–900 m, 300–600 m and 0–300 m, plus peak triangles and grey bands for mountain ranges. The circled numbers 1–6 mark the six physiographic divisions.
- North (1): the Pamir Knot, Hindu Kush and Kunlun beyond the border; inside, the Karakoram (K2), Ladakh and Zaskar ranges (the Trans-Himalaya), the Great Himalaya and the Shiwalik. Peaks: K2, Kamet, Nanda Devi, Dhaulagiri, Annapurna, Everest, Makalu, Kanchenjunga, Namcha Barwa, and Kailash in Tibet. In the north-east: Patkai Bum, Naga hills, Mizo hills, and the Garo, Khasi and Jaintia hills.
- Plain (2): the ‘Northern Plain’ lettering follows the Indus–Ganga–Brahmaputra lowland, with the Yamuna, Ganga, Son, Kosi and the Brahmaputra (the Tsangpo in Tibet).
- Plateau (3): Malwa plateau, Bundelkhand, Baghelkhand, Chota Nagpur plateau, Ramgarh hills, Kaimur hills, Vindhya, Satpura, Mahadeo hills, Maikala, Ajanta range, Satmala hills, Garhjat hills, Malaygiri, the Chhattisgarh basin, the Telangana plateau and Nallamala. Spot heights: Kalsubai 1,646 m, Mahendragiri 1,501 m, Anai Mudi 2,695 m. Most land above 600 m lies along the Western Ghats and in the south.
- Desert (4): the ‘Great Indian Desert’ west of the Aravali with the Luni river and the Rann of Kachchh; the Gir range and Kathiawar peninsula to the south.
- Coasts (5): Konkan and Malabar on the west, Northern Circars and Coromandel on the east, with Chilika Lake, the Gulfs of Khambhat and Mannar.
- Islands (6): Lakshadweep in the Lakshadweep Sea; the Andaman & Nicobar Islands with the Andaman Sea to their east.
3. The Northern and North-eastern Mountains
In simple wordsPush a tablecloth from one end and it wrinkles into several parallel folds, the highest in the middle of the pile. The Himalayas are such a set of parallel wrinkles, and like a wall around a garden they block cold winds, catch rain, divide rivers and separate peoples.
These mountains are the Himalayas and the north-eastern hills. The Himalayas are a series of parallel ranges, the most important being the Great Himalaya and the Shiwalik. The Great Himalayan range — the central axial range — is about 2,500 km long from east to west, and the system is 160–400 km wide from north to south. It stands like a long, strong wall between the subcontinent and Central and East Asia.
NCERT check — which ranges?The reprint says the important ranges are ‘the Greater Himalayan range, which includes the Great Himalayas and the Shiwalik’ — a garbled sentence. The standard division (Beyond NCERT, and in older NCERT editions) is three parallel ranges: the Greater Himalaya (Himadri), the Lesser Himalaya (Himachal) and the Shiwalik (Outer Himalaya), with the Trans-Himalaya (Karakoram, Ladakh, Zaskar) to the north. The Great Himalaya is the oldest and highest; the Shiwalik is the youngest (UPSC 1994).
Orientation changes along the arc. In north-western India the ranges run north-west to south-east; in Darjiling and Sikkim they run east–west; in Arunachal Pradesh they swing south-west to north-east; and in Nagaland, Manipur and Mizoram they run north–south.
NCERT check — a direction misprintThe reprint says that in Arunachal Pradesh the ranges run ‘from south-west to the north-west’. That is impossible for one line; the ranges there run south-west to north-east, which is how this page gives it.
Reading NCERT Figure 2.3 — The Himalayas (page 11)
- A snow-covered, sharp-crested peak rising far above dark lower ridges, with a long ridge sweeping down to the left.
- Points to notice: permanent snow at the top, very steep slopes, and knife-edge ridges — the signs of young, high fold mountains still being uplifted and carved by ice and rivers.
More than a barrier. NCERT calls the Himalayas a physical, climatic, drainage and cultural divide. They block cold Central Asian winds and force the monsoon to drop its rain; they separate the rivers that flow into India from those flowing to Central Asia and Tibet, and feed perennial rivers; and they kept the cultures on either side distinct.
Beyond NCERT (asked by UPSC)
- Nanda Devi lies in the Kumaon Himalaya (UPSC 2003, 2022); Namcha Barwa is at the eastern end, where the Tsangpo–Brahmaputra makes its great bend; the north-eastern ranges continue into Myanmar as the Arakan Yoma (UPSC 1995).
- The Brahmaputra's U-turn into India follows the syntaxial bend of the young Himalaya at their eastern end (UPSC 2011).
- Jammu & Kashmir (now Ladakh) is the area lying partly north of the Himalayas (UPSC 1989) — the Trans-Himalaya, a cold desert (exercise Q2-ii).
- Without the Himalayas, India would get Siberian cold waves, far less alluvium in the plains and a different monsoon (UPSC 2010).
4. The Northern Plain
In simple wordsPour muddy water down a slide into a tray. The heavy stones stop at the bottom of the slide, the water seeps away and pops up again a little further on as puddles, and the fine mud spreads across the tray. That is exactly the order of the northern plain: Bhabar (stones), Tarai (puddles and marsh), and the wide alluvial plain (mud).
The northern plains are built from alluvium brought by the Indus, the Ganga and the Brahmaputra. They stretch about 3,200 km east–west and are on average 150–300 km wide, with alluvium up to 1,000–2,000 m deep. The general elevation is only 50–150 m above sea level — a ‘featureless’ plain. From north to south they split into the Bhabar, the Tarai and the alluvial plains, and the alluvial plains into Bhangar and Khadar.
| Belt | Width / position | What happens there |
|---|---|---|
| Bhabar | 8–10 km, parallel to the Shiwalik foothills at the break of slope | Rivers drop heavy boulders and pebbles; small streams disappear into the gravel |
| Tarai | 10–20 km, south of the Bhabar | Streams re-emerge without clear channels → marshy, swampy land with luxuriant vegetation and varied wildlife |
| Bhangar | South of the Tarai, above flood level | Old alluvium |
| Khadar | Along the rivers | New alluvium, renewed by floods |
⤵ From mountain stream to delta
Fast stream leaves the Shiwalikslope suddenly flattens
Bhabarboulders dropped; water sinks underground
Taraiwater seeps out → swamps and tall grass
Bhangar and Khadarmature river: sand bars, meanders, ox-bow lakes, braided channels
Deltas at the mouthse.g. the Sunderbans delta
- The plains show mature-stage river landforms — sand bars, meanders, ox-bow lakes and braided channels — and the Brahmaputra plains are known for riverine islands and sand bars, periodic floods and shifting courses.
- Haryana and Delhi form the water divide between the Indus and Ganga systems.
- The Brahmaputra flows north-east to south-west, then turns almost 90° south at Dhubri to enter Bangladesh.
- Fertile alluvium grows wheat, rice, sugarcane and jute and supports a very large population.
Reading NCERT Figure 2.4 — Northern Plain (page 11)
- People bent over transplanting seedlings in flooded, level fields divided by low bunds, with a line of trees on the horizon.
- It shows two things at once: the plain is dead flat, and its fertile, water-holding alluvium supports intensive farming such as wet rice — the reason so many people live here.
Exam trapBhangar = old alluvium (higher, away from the river); Khadar = new alluvium (floodplain). It is easy to swap them. And in the Bhabar the streams vanish; in the Tarai they reappear.
5. The Peninsular Plateau
In simple wordsPicture a huge, ancient table tilted slightly towards the east, its edges raised into hills and its top cracked and worn. Rain that falls near the high western edge runs across the whole table to the Bay of Bengal. That is the Peninsular plateau.
Rising from about 150 m above the river plains to 600–900 m, the plateau is an irregular triangle. Its outer edges are the Delhi ridge (an extension of the Aravali) in the north-west, the Rajmahal hills in the east, the Gir range in the west and the Cardamom hills in the south; the Shillong and Karbi Anglong plateau extends it to the north-east. It is made of patland plateaus — Hazaribagh, Palamu, Ranchi, Malwa, Coimbatore, Karnataka — and is one of India's oldest and most stable landmasses. Its general slope is from west to east, as the rivers show.
- Typical features: tors, block mountains, rift valleys, spurs, bare rocky surfaces, hummocky hills and wall-like quartzite dykes that make natural sites for water storage.
- Black soil is prominent in the western and north-western parts.
- Recurrent uplift and submergence, faulting and fractures — the Bhima fault is notable for repeated earthquakes.
- The north-west has ravines and gorges — the Chambal, Bhind and Morena ravines.
Reading NCERT Figure 2.5 — A Part of Peninsular Plateau (page 12)
- A wall of steep, stepped cliffs with near-vertical columns of rock falling into a forested valley, and a flat top above.
- This is the scarped, flat-topped look of the plateau: layered rock (like the lava sheets of the Deccan) eroded into steps and scarps, with a level ‘table’ surface on top.
Three groups. On the basis of relief, the plateau divides into the Deccan Plateau, the Central Highlands and the North-eastern Plateau.
| Deccan Plateau | Central Highlands | North-eastern Plateau | |
|---|---|---|---|
| Bounded by | Western Ghats (W), Eastern Ghats (E), Satpura, Maikal range and Mahadeo hills (N) | Aravali on the west; Satpura scarps on the south | Separated from the main block by a fault between the Rajmahal hills and the Meghalaya plateau |
| Height | Western Ghats ≈ 1,500 m; plateau 600–900 m | 700–1,000 m, sloping north and north-east; Satpura 600–900 m | Meghalaya: Garo, Khasi and Jaintia hills; Karbi Anglong in Assam |
| Key facts | Most peninsular rivers rise in the Western Ghats; Eastern Ghats are cut through by rivers | Satpura is a classic relict range; metamorphic rocks (marble, slate, gneiss); extends to Jaisalmer under the sand | Rich in coal, iron ore, sillimanite, limestone and uranium; heavy SW-monsoon rain → highly eroded; bare rock at Cherrapunji |
| Western Ghats | Eastern Ghats | |
|---|---|---|
| Continuity | Continuous | Discontinuous, low, highly eroded by rivers |
| Height | Higher — average ≈ 1,500 m, rising north to south | Lower |
| Local names / ranges | Sahyadri (Maharashtra) · Nilgiri (Karnataka–Tamil Nadu) · Anaimalai and Cardamom (Kerala) | Javadi hills · Palkonda range · Nallamala hills · Mahendragiri hills |
| Highest | Anaimudi 2,695 m (Anaimalai) — highest in the Peninsula; then Dodabetta 2,637 m (Nilgiri) | Mahendragiri 1,501 m (on Figure 2.2) |
| Rivers | Source of most peninsular rivers | Cut by the Mahanadi, Godavari, Krishna, Kaveri |
Exam traps
- The Western Ghats are higher in the south, not the north (UPSC 2005 used ‘higher in the northern region’ as the wrong statement).
- The two Ghats meet at the Nilgiris (UPSC 2008) — not the Anaimalai or Cardamom hills.
- Banas is the only significant Chambal tributary that rises in the Aravali; most Yamuna tributaries rise in the Vindhyan and Kaimur ranges.
⤵ How the North-eastern Plateau got cut off
Indian plate pushes north-eastwhile the Himalayas were forming
A great fault opensbetween the Rajmahal hills and the Meghalaya plateau
Rivers fill the depressionwith sediment
Meghalaya and Karbi Anglong stand detachedbut are still part of the old Peninsular block
Beyond NCERT (asked by UPSC)
- North → south hills: Nallamala → Javadi → Nilgiri → Anaimalai (UPSC 2005); Mahadeo → Satpura → Sahyadri (UPSC 2004).
- The Palghat gap, the easy route between the two coasts, lies between the Nilgiri and Anaimalai hills (UPSC 1990).
- The Ajanta range lies wholly in Maharashtra (UPSC 1995); the Western Ghats run through six states — Gujarat, Maharashtra, Goa, Karnataka, Kerala, Tamil Nadu (UPSC 2017).
- Amarkantak is where the Vindhya, Satpura and Maikal meet — not the Sahyadri; Biligirirangan hills link the Eastern and Western Ghats; Seshachalam hills are part of the Eastern Ghats (UPSC 2023: all three statements false).
- Dhupgarh (≈ 1,350 m, Mahadeo hills) is the Satpura's highest point.
6. The Indian Desert
In simple wordsUnderneath the sand of Rajasthan lies the same old rock as the Deccan — like a stone floor covered with a thick sandy carpet. The carpet was shaped by wind, not water, because hardly any rain falls.
North-west of the Aravali lies the Great Indian Desert, or Marusthali: undulating land dotted with longitudinal dunes and barchans, rainfall below 150 mm a year, an arid climate and little vegetation. In the Mesozoic era it lay under the sea — shown by the wood fossils park at Aakal (fossils about 180 million years old) and marine deposits around Brahmsar near Jaisalmer. Its rock base is an extension of the Peninsular plateau, but its surface has been carved by physical weathering and wind.
- Landforms: mushroom rocks, shifting dunes and oases (mostly in the south).
- Slope: the northern part slopes towards Sindh, the southern towards the Rann of Kachchh.
- Rivers are ephemeral; the Luni in the south is the significant one. Some streams end in a lake or playa — inland drainage. Playa water is brackish and a source of salt.
- Low rain plus high evaporation make it a water-deficit region.
Reading NCERT Figure 2.6 — The Indian Desert (page 14)
- A line of riders on camels crossing a smooth, high sand dune with fine wind ripples on its surface and a sharp crest.
- The box asks: which type of dune is this? Most guides answer barchan (crescent-shaped dune). Look for the tell-tale sign: a barchan has a gentle windward slope, a steep slip face and two horns pointing downwind; a longitudinal dune is a long ridge running along the wind. The photo shows only part of one dune, so either answer needs that reason.
⤵ From sea floor to sand sea
Mesozoic: under the seamarine deposits at Brahmsar
Land with forestswood fossils at Aakal (≈ 180 million years old)
Climate turns aridrain below 150 mm
Wind and physical weathering ruledunes, mushroom rocks, playas
Beyond NCERTThe Rann of Kachchh marshland owes its form to repeated falls in sea level over a former sea inlet (UPSC 2023). The Luni ends in the marshes of the Rann rather than reaching the open sea.
7. The Coastal Plains
In simple wordsIf the land along a coast sinks, the sea floods into the valleys and leaves a narrow strip with deep water close to shore — perfect for parking big ships. If the land rises, the old sea floor appears as a wide, flat plain with shallow water offshore. India's west coast is the first kind, the east coast the second.
| Western coastal plain | Eastern coastal plain | |
|---|---|---|
| Type | Submerged — Dwaraka is believed to lie under the sea | Emergent |
| Width | Narrow, broader towards north and south | Broader |
| Rivers | No deltas | Well-developed deltas: Mahanadi, Godavari, Krishna, Kaveri |
| Ports | Many natural ports: Kandla, Mazagaon, JLN Port Nhava Sheva, Marmagao, Mangalore, Cochin | Fewer ports and harbours |
| Divisions | Kachchh and Kathiawar (Gujarat), Konkan (Maharashtra), Goan, Malabar (Karnataka and Kerala) | Northern Circars and Coromandel (named on Figure 2.2) |
| Special | Kayals (backwaters) on the Malabar coast: fishing, inland navigation, tourism; the Nehru Trophy Vallamkali boat race on Punnamada Kayal | Continental shelf said to extend up to 500 km |
Reading NCERT Figure 2.7 — Coastal Plains (page 14)
- A long line of people walking across a flat, green, grassy field fringed with coconut palms.
- It conveys the flat, low, palm-lined look of a coastal plain with a humid climate — the kind of setting found along the Kerala and Konkan coasts.
NCERT check — the 500 km shelfNCERT says the eastern continental shelf extends up to 500 km, hindering ports. Standard data put India's widest shelf off the west coast — off South Gujarat and Mumbai — and UPSC 1991 accepted ‘South Gujarat coast’ as where the shelf is widest. Use NCERT's reasoning (an emergent, shallow coast has fewer natural harbours) but be careful repeating the 500 km figure in Prelims.
Beyond NCERT
- Major east-coast ports (NCERT's ‘name some ports’): Kolkata–Haldia, Paradip, Visakhapatnam, Chennai, Ennore (Kamarajar), Tuticorin (V.O. Chidambaranar). Most were developed artificially or at river mouths and lagoons.
- West-flowing rivers make no deltas because they are short and swift, fall steeply from the Ghats over hard rock, carry relatively little sediment to a narrow plain, and meet a sinking coast where tides flush the mouth — not because they carry no sediment at all (UPSC 2004 A–R; Mains 2013).
8. The Islands
In simple wordsThe Andaman and Nicobar Islands are the tops of a drowned mountain range poking out of the sea. The Lakshadweep islands are built by tiny coral animals — rings of reef and sand on the sea surface.
| Bay of Bengal (Andaman & Nicobar) | Arabian Sea (Lakshadweep and Minicoy) | |
|---|---|---|
| Number | About 572 islands/islets | About 36 islands, 11 inhabited |
| Position | 6°N–14°N, 92°E–94°E | 8°N–12°N, 71°E–74°E; 220–440 km off the Kerala coast |
| Origin | Elevated parts of submarine mountains; some small ones volcanic — Barren Island, India's only active volcano | Entirely coral deposits |
| Groups and channels | Andaman (north) and Nicobar (south), separated by the Ten Degree Channel; principal islet groups Ritchie's archipelago and Labyrinth island | Divided by the Nine Degree Channel (see the note below); Amini to the north, Cannanore to the south |
| Relief and coast | Peaks: Saddle Peak 738 m (North Andaman), Mt Diavolo 515 m, Mt Koyob 460 m, Mt Thuillier 642 m (Great Nicobar); coral deposits, fine beaches | Low; storm beaches of loose pebbles, shingle, cobbles and boulders on the eastern side |
| Climate and vegetation | Convectional rainfall, equatorial vegetation | — |
Reading NCERT Figure 2.8 — An Island (page 15)
- A small, low island covered in dense trees, edged by a curving white sand beach and surrounded by calm, shallow water.
- Notice how little the land rises above the sea — typical of coral islands and small islets, and the reason they are so exposed to storm surges, tsunamis and sea-level rise.
Reading the 26 December 2004 box (page 15)The calamity was the Indian Ocean tsunami caused by an undersea earthquake off Sumatra. It also hit Indonesia, Sri Lanka, Thailand, the Maldives, Malaysia and the Tamil Nadu, Andhra, Kerala and Puducherry coasts. Major consequences: huge loss of life and coastal destruction; in India it led to the Indian Tsunami Early Warning Centre at INCOIS, Hyderabad (2007) (Beyond NCERT). The live Physical Geography Chapter 3 has the full story.
NCERT checks — two island figures
- ‘Minicoy is the largest island with an area of 453 sq km’ cannot be right: the whole of Lakshadweep covers only about 32 sq km (Beyond NCERT). Learn that the islands are tiny coral islands; don't quote 453 sq km.
- NCERT says the Nine Degree Channel divides the group with Amini to the north and Cannanore to the south. In standard atlases the Nine Degree Channel separates Minicoy from the rest of Lakshadweep, and the Eight Degree Channel separates Minicoy from the Maldives; Amindivi and Cannanore are the northern and southern sub-groups of the main islands.
Beyond NCERT (asked by UPSC)
- The Duncan Passage lies between South Andaman and Little Andaman (UPSC 1982); the Ten Degree Channel between the Andaman and the Nicobar groups (UPSC 2014).
- Saddle Peak is in North Andaman (UPSC 1996). The land closest to Great Nicobar is Sumatra, across the Great Channel (UPSC 2017).
- Barren Island lies in the Andaman Sea east of the main Andaman group (UPSC 2018).
NCERT's in-text questions — short answers
Can you map the different phases in the movement of the Indian plate?
Part of Gondwana south of the equator, joined to Australia → split away and drifted north across the equator → collided with Asia, raising the Himalayas → still moving north. See the live Physical Geography Chapter 4 for the stages and dates.
Name some important consequences of the northward movement of the Indian plate.
The rising Himalayas; the Indo-Ganga trough that became the northern plain; earthquakes along the Himalaya and the north-east; faulting and uplift in the Peninsula; the detached Meghalaya plateau; the Himalaya's climatic barrier and the monsoon pattern.
Calculate and compare the gradients of Himalayan and Peninsular rivers.
Gradient = fall in height ÷ horizontal distance. Himalayan rivers fall several thousand metres in their first few hundred km (steep, youthful), then barely 50–150 m across the whole plain; Peninsular rivers flow across an old, worn plateau with low gradients and shallow valleys.
Identify the impact of the Himalayas on the geo-environment of South Asia. Find other examples of such divides.
Climatic barrier (blocks cold winds, traps monsoon rain), source of perennial rivers and alluvium, drainage divide between South and Central Asia, and a cultural boundary. Other divides (Beyond NCERT): the Alps between Mediterranean and Central Europe; the Andes and Rockies, which create rain-shadow deserts on their lee sides.
Name peninsular rivers draining to the Bay of Bengal and to the Arabian Sea; which landforms are typical of the east-flowing rivers but absent in the west-flowing ones?
To the Bay: Mahanadi, Godavari, Krishna, Kaveri. To the Arabian Sea: Narmada, Tapi (and the short Western Ghats rivers). East-flowing rivers form deltas and broad floodplains; west-flowing ones end in estuaries.
Can you identify the type of sand dunes shown in Figure 2.6?
Usually answered as barchans (crescent dunes) — give the reason: gentle windward side, steep lee face, horns downwind. (See section 6.)
Name some ports on the eastern coast.
Kolkata–Haldia, Paradip, Visakhapatnam, Chennai, Ennore, Tuticorin (Beyond NCERT).
26 December 2004: name the calamity, other areas hit and its major consequence.
The Indian Ocean tsunami; also Indonesia, Sri Lanka, Thailand, the Maldives and India's south-east coast; massive loss of life and property, and the setting up of tsunami early warning in the Indian Ocean.
NCERT exercise — answer outlines
Try each question yourself first, then open the outline to compare. These are the points an examiner looks for.
1(i) Which one of the water bodies separates the Andaman from the Nicobar? (a) 11° Channel (b) Gulf of Mannar (c) 10° Channel (d) Andaman Sea
(c) The Ten Degree Channel.
1(ii) On which of the following hill ranges is the ‘Dodabeta’ peak situated? (a) Nilgiri hills (b) Anaimalai hills (c) Cardamom hills (d) Nallamala hills
(a) Nilgiri hills — Dodabetta, 2,637 m, second only to Anaimudi (Anaimalai) in the Peninsula.
2(i) If a person is to travel to Lakshadweep, from which coastal plain does he prefer and why? (30 words)
The Malabar coast (Kerala), e.g. from Kochi — the islands lie only 220–440 km off the Kerala coast, so this is the shortest crossing, with port and air links.
2(ii) Where in India will you find a cold desert? Name some important ranges of this region. (30 words)
In Ladakh — the Trans-Himalayan region north of the Great Himalaya, lying in the rain shadow (Beyond the reprint's text). Ranges: Karakoram, Ladakh and Zaskar (all on Figure 2.2).
2(iii) Why is the western coastal plain devoid of any delta? (30 words)
West-flowing rivers are short and swift, falling steeply from the Western Ghats over hard rock; they bring little sediment to a narrow, submerged coastal plain where waves and tides carry it away — so they form estuaries, not deltas.
3(i) Make a comparison of the island groups of the Arabian Sea and the Bay of Bengal. (125 words)
Number: ≈ 572 vs ≈ 36 (11 inhabited).
Location: A&N 6–14°N, 92–94°E in the Bay of Bengal; Lakshadweep 8–12°N, 71–74°E, 220–440 km off Kerala.
Origin: A&N — raised submarine mountains, some volcanic (Barren Island, India's only active volcano); Lakshadweep — coral.
Relief: A&N hilly (Saddle Peak 738 m); Lakshadweep low, with storm beaches of shingle and boulders.
Divisions: Andaman and Nicobar by the Ten Degree Channel; Lakshadweep sub-groups and Minicoy by the Nine Degree Channel.
Climate and vegetation: A&N — convectional rain, equatorial forest; both have coral and beaches.
Significance: strategic location, tourism, fisheries; both vulnerable to cyclones, tsunamis and sea-level rise.
Location: A&N 6–14°N, 92–94°E in the Bay of Bengal; Lakshadweep 8–12°N, 71–74°E, 220–440 km off Kerala.
Origin: A&N — raised submarine mountains, some volcanic (Barren Island, India's only active volcano); Lakshadweep — coral.
Relief: A&N hilly (Saddle Peak 738 m); Lakshadweep low, with storm beaches of shingle and boulders.
Divisions: Andaman and Nicobar by the Ten Degree Channel; Lakshadweep sub-groups and Minicoy by the Nine Degree Channel.
Climate and vegetation: A&N — convectional rain, equatorial forest; both have coral and beaches.
Significance: strategic location, tourism, fisheries; both vulnerable to cyclones, tsunamis and sea-level rise.
3(ii) What are the important geomorphological features found in the river valley plains? (125 words)
Belts: Bhabar (boulders, streams vanish), Tarai (marshy re-emergence), Bhangar (old alluvium), Khadar (new alluvium, floodplain).
Mature fluvial forms: meanders, ox-bow lakes, sand bars, braided channels, floodplains and natural levees (Beyond NCERT).
Brahmaputra: riverine islands and sand bars, frequent floods, shifting courses.
Mouths: large deltas such as the Sunderbans.
Overall: a flat plain only 50–150 m above sea level; a water divide over Haryana–Delhi; fertile soils supporting dense population. A labelled N–S profile adds marks.
Mature fluvial forms: meanders, ox-bow lakes, sand bars, braided channels, floodplains and natural levees (Beyond NCERT).
Brahmaputra: riverine islands and sand bars, frequent floods, shifting courses.
Mouths: large deltas such as the Sunderbans.
Overall: a flat plain only 50–150 m above sea level; a water divide over Haryana–Delhi; fertile soils supporting dense population. A labelled N–S profile adds marks.
3(iii) If you move from Badrinath to the Sunderbans delta along the course of the Ganga, what major geomorphological features will you come across? (125 words)
Upper course (Great Himalaya): Badrinath on the Alaknanda — glaciers and snowfields upstream, deep gorges, V-shaped valleys, rapids and waterfalls; the Alaknanda joins the Bhagirathi at Devprayag to form the Ganga (Beyond NCERT).
Shiwalik and foothills: the river leaves the hills near Haridwar — Bhabar gravels and Tarai marsh.
Middle course (plain): Bhangar uplands and Khadar floodplains; meanders, ox-bow lakes, sand bars, braided channels, levees.
Lower course: very gentle gradient, many distributaries, the Sunderbans delta with tidal creeks and mangroves.
Conclude: the journey shows a river passing from youth to maturity to old age.
Shiwalik and foothills: the river leaves the hills near Haridwar — Bhabar gravels and Tarai marsh.
Middle course (plain): Bhangar uplands and Khadar floodplains; meanders, ox-bow lakes, sand bars, braided channels, levees.
Lower course: very gentle gradient, many distributaries, the Sunderbans delta with tidal creeks and mangroves.
Conclude: the journey shows a river passing from youth to maturity to old age.
Project (i): Make a list of major Himalayan peaks from west to east with the help of an atlas.
Starting from Figure 2.2: K2 → Kamet → Nanda Devi → Dhaulagiri → Annapurna → Everest → Makalu → Kanchenjunga → Namcha Barwa (heights in the diagram in section 3). Note which lie in India, Nepal or China.
Project (ii): Identify the major landforms of your state and analyse the major economic activity in each.
Method: list the state's physiographic divisions (hills, plateau, plain, coast, desert), then match activities — e.g. plains → intensive farming; plateau → mining and dry farming; hills → horticulture, forestry, tourism; coasts → fishing, ports, tourism; desert → pastoralism, salt. This is exactly the link UPSC asked about in Mains 2025 (non-farm primary activities and physiography).
What to remember
Numbers
Age of the earth≈ 4,600 million years
Great Himalayan range — length≈ 2,500 km east–west
Himalayan width160–400 km
Northern plain — length / width≈ 3,200 km / 150–300 km
Alluvium depth in the plains1,000–2,000 m
Plain elevation50–150 m above sea level
Bhabar / Tarai width8–10 km / 10–20 km
Peninsular plateau heightfrom 150 m to 600–900 m
Central Highlands700–1,000 m
Western Ghats average≈ 1,500 m (rising north → south)
Anaimudi / Dodabetta2,695 m / 2,637 m
Desert rainfallbelow 150 mm a year
Aakal wood fossils≈ 180 million years old
Andaman & Nicobar≈ 572 islands · 6–14°N, 92–94°E
Lakshadweep≈ 36 islands (11 inhabited) · 8–12°N, 71–74°E · 220–440 km off Kerala
Saddle Peak / Mt Thuillier738 m / 642 m
One-liners
- Peninsula = old and rigid; Himalayas = young and folded; plain = filled trough.
- Himalayas: a physical, climatic, drainage and cultural divide.
- Bhabar (pebbles, streams vanish) → Tarai (marsh) → Bhangar (old) / Khadar (new).
- The Deccan slopes west → east, so most rivers flow to the Bay of Bengal.
- Western Ghats continuous and high; Eastern Ghats broken and low; they meet at the Nilgiris.
- Haryana–Delhi = Indus–Ganga water divide; Brahmaputra turns south at Dhubri.
- West coast submerged (ports, kayals); east coast emergent (deltas).
- Ten Degree Channel: Andaman | Nicobar. Barren Island: India's only active volcano.
Traps to avoid
- Bhangar is old alluvium, Khadar new.
- Western Ghats are higher in the south (Anaimudi), not the north.
- The Ghats meet at the Nilgiris, not the Cardamom hills.
- Oldest Himalayan range = Great Himalaya; youngest = Shiwalik. Oldest mountains in India = Aravali.
- Lakshadweep is coral; the Andamans are raised submarine mountains.
- West-coast rivers make no deltas because they are short, swift and steep — not because they carry no sediment.
- NCERT's Arunachal orientation ‘SW to NW’ is a misprint — it is SW to NE.
- Minicoy is not 453 sq km — the whole of Lakshadweep is only about 32 sq km.
- The Meghalaya plateau is part of the Peninsular block, not of the Himalayas.
How to strategise
Prelims — what UPSC asks
- Order and location are the favourite format: hills north → south (2004, 2005), the Palghat gap (1990), where the Ghats meet (2008), a range in only one state (1995), states over which the Himalaya and the Western Ghats spread (2017), hills and regions matched (2014), Amarkantak/Biligirirangan/Seshachalam (2023). Practise with a blank outline map and Figure 2.2.
- Himalaya: arc shape (1986), oldest range (1994), Tethys origin (1991), Arakan Yoma (1995), Nanda Devi in Kumaon (2003, 2022), the Brahmaputra's syntaxial U-turn (2011), evidence for young fold mountains (2012), the ‘no Himalaya’ thought-experiment (2010), the state partly north of the Himalaya (1989).
- Peninsula and structure: oldest mountains — Aravali (1979), its age (2001), rock ages matched (1997), Chambal ravines and gully erosion (1983, 1994), Banas–Luni cutting the Aravali (1989), the eastward tilt (2007), Western Ghats statements (2005), the Peninsular Block features lifted almost word for word from NCERT (2026).
- Coasts and islands: Duncan Passage (1982), Saddle Peak (1996), Ten Degree Channel (2014), Sumatra nearest to Great Nicobar (2017), Barren Island (2018), the widest continental shelf (1991), the Rann of Kachchh (2023).
Mains — where it appears and how to answer
- GS1: why Western Ghats rivers form no deltas (2013); how non-farm primary activities relate to physiographic features (2025). Physiography is the opening paragraph of almost every India-geography answer — learn to sketch the six divisions in 30 seconds.
- Answer frame: structure (which geological division) → process (folding, faulting, deposition, wind) → resulting landform with NCERT numbers → human use (farming, ports, minerals, tourism) → hazard or conservation angle.
- Useful sketches: the S–N Himalayan cross-section, the Bhabar–Tarai–Bhangar–Khadar profile, and the W–E Deccan profile.
Self-check
Tap an option. NCERT's own exercise questions come first; the rest test the figures and common confusions.
1. Which one of the water bodies separates the Andaman from the Nicobar?
2. On which of the following hill ranges is the ‘Dodabeta’ peak situated?
3. In the northern plain, the belt where streams re-emerge and create marshy conditions is the…
4. Which statement about the Western and Eastern Ghats is correct?
5. The western coastal plain is an example of a…
6. The Meghalaya plateau is best described as…
7. Wood fossils at Aakal and marine deposits at Brahmsar near Jaisalmer suggest that the Thar region…
UPSC questions from this chapter
Open any question to attempt it in the Question bank — your attempt is saved to your progress.