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.
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← Understanding Society: India and Beyond – I — all chaptersShaping of the Earth’s Surface
Start here: why this chapter matters
In simple wordsThink of the Earth's surface as a sculpture with two artists. One works from inside — pushing, lifting, cracking (mountains, earthquakes, volcanoes). The other works from outside — rain, rivers, ice, wind and waves slowly sanding it down and carrying the dust elsewhere. Every hill, valley and beach you see is their joint work, still in progress.
This is Chapter 2 of the new integrated Grade 9 book: 26 pages (13–38) built round five ‘Big Questions’ — what shapes the surface, what plate tectonics is, how landforms form and are classified, how living beings are connected to them, and how landform-linked disasters affect people. Its parts: plate tectonics and the Earth's interior; weathering and erosion; the agents of gradation — running water, waves and currents, glaciers, wind and underground water; and four disasters. It has 30 figures (two world maps, an interior diagram, a heat-flow diagram, labelled landform drawings paired with photographs, and disaster photographs), a dozen boxes (Let's Map, Let's Explore, Don't Miss Out, Think About It), a Before we move on summary and 15 questions and activities, with an NDMA landslide poster. We use ten concept sections. Every number is recomputed; our additions are marked †.
- Matching live chapters (for depth): kegy203 (Interior of the Earth — seismic waves, volcanoes), kegy204 (Distribution of Oceans and Continents — continental drift, sea-floor spreading, plate tectonics), kegy205 (Geomorphic Processes — endogenic and exogenic forces, weathering, mass movements), kegy206 (Landforms and their Evolution — every landform here in detail), kegy102 (Structure and Physiography of India — the Himalaya) and kegy106 (Natural Hazards and Disasters). Class 10: jess101 (soil erosion and conservation).
- In this book: iest103 (Atmosphere and Climate) follows; Part 2 adds waves and currents, as the book says.
- UPSC, honestly: geomorphology is a steady Prelims and GS1 topic, but questions were set from the senior books above, so most of them sit there. We link ten questions whose core this chapter genuinely teaches (most also sit on a Class 11 or Class 10 chapter): what causes earthquakes (1981), the 1991 Garhwal earthquake (1992), the mark of a mature river (1990), the barchan (1991), contour bunding (1982, 2013), rain and chemical weathering (2024), and Mains on Himalayan landslides (2016), fjords (2023) and wind processes in desertification (2026).
| Word | What it means here |
|---|---|
| Landform | A natural feature of the surface — mountain, valley, plateau, plain, dune, delta (margin glossary, p. 13) |
| Endogenic / exogenic forces † | Forces from inside the Earth (folding, faulting, quakes, volcanoes) / acting on the surface (weathering, erosion, deposition) |
| Lithosphere | The rigid outer shell: crust + upper mantle, about 100 km thick, broken into plates |
| Asthenosphere | The hot, weak, partly molten layer below the lithosphere on which plates move |
| Tectonic plate | A huge slab of lithosphere moving a few centimetres a year |
| Subduction † | One plate sinking beneath another at a convergent boundary |
| Ring of Fire | The belt of frequent earthquakes and volcanoes round the Pacific Ocean |
| Weathering | Breaking of rock in place — physical, chemical, biological |
| Erosion | Wearing away and carrying of material by water, wind, ice or waves |
| Agents of gradation | Running water, glaciers, wind, waves and groundwater, which wear down highs and fill lows |
| Meander / oxbow lake | A loop in a river / a loop cut off as a curved lake |
| Moraine (till) | Unsorted rock and soil dumped by a glacier |
| Karst | Limestone country shaped by solution: caves, sinkholes, underground rivers |
| GLOF | Glacial Lake Outburst Flood — sudden release of a glacial lake when its ice or moraine dam fails |
Reading the chapter opening and the Landforms margin box (page 13)The page opens with the five Big Questions in a list and a QR code to e-content; a margin box defines a landform as a natural surface feature formed by weathering, erosion, deposition and crustal movement, with examples (mountains, valleys, plateaus, plains, deserts, coastal features). The point: the chapter will explain landforms by the processes that make them, and link them to people and disasters.
At a glance — the six ideas to carry away
- Interior: crust (30–40 km under continents, 5–7 km under oceans) → mantle (mostly solid) → liquid outer core → solid inner core. Lithosphere (≈ 100 km) = crust + upper mantle, broken into plates; they move on the partly molten asthenosphere, a few cm a year.
- Plate boundaries: convergent (land–land → fold mountains, the Himalaya; ocean–land → subduction, volcanoes, earthquakes), divergent (new crust, Mid-Atlantic Ridge), transform (San Andreas). Seven major plates; most quakes and volcanoes on boundaries — Ring of Fire round the Pacific.
- Weathering breaks rock in place (physical, chemical, biological); erosion moves it (water, wind, ice, waves). Traditional conservation: contour trenches, bunding, terracing, Nagaland's Zabo, check dams.
- Running water: upper — V-valleys, waterfalls, rapids; middle — meanders, oxbow lakes, floodplains; lower — deltas, levees (and, in the book's list, alluvial fans). Sundarbans delta. Waves: beaches, bars; cliffs, platforms, caves, arches, stacks.
- Glaciers: U-shaped valleys, cirques, aretes, hanging valleys, fjords; moraines — lateral, medial, terminal. Wind: yardangs, ventifacts, deflation hollows, desert pavements; dunes — barchan, longitudinal, star, parabolic. Groundwater: karst — caves, stalactites, stalagmites, sinkholes, underground rivers.
- Disasters tied to landforms: landslides (rain, quakes, steep loose slopes, deforestation, road-cutting), avalanches, GLOFs (moraine-dammed lakes bursting), dust storms (drought, bare soil, strong winds).
1. Inside the Earth: crust, mantle, core — and the plates on top
In simple wordsPicture a boiled egg with a cracked shell. The shell is the crust, broken into pieces; the white is the thick mantle; the yolk is the core. Now imagine the white is not quite solid just under the shell, so the shell pieces can slide very slowly. That slippery zone is the asthenosphere.
The book's account: the Earth has three main layers. The crust is the thin outer layer we live on — 30–40 km thick under continents and 5–7 km under oceans. The mantle below is very thick and hot, and (in Fig. 2.1's note) mostly solid. The core is innermost, extremely hot and heavy: a fluid outer core of mainly iron and nickel and a solid inner core, the densest part. The crust plus the upper part of the mantle forms the rigid lithosphere, which is broken into tectonic plates. Below it lies the asthenosphere, semi-molten, which lets the plates move.
| Layer | NCERT (Fig. 2.1, ‘approximate’) | Standard reference (Beyond NCERT †) | State |
|---|---|---|---|
| Crust | continental 30 km (text 30–40); oceanic 5 km (text 5–7) | continental ≈ 35 km on average, up to ≈ 70 km under high mountains; oceanic ≈ 7 km | solid |
| Lithosphere | 100 km | ≈ 100 km, thinner under ridges, thicker under old continents | rigid solid |
| Asthenosphere | 200 km | from ≈ 100 km to a few hundred km; base varies | hot, partly molten, can flow |
| Mantle | 2,900 km | to ≈ 2,890 km depth | mostly solid; flows very slowly |
| Outer core | 2,200 km | 2,890 → 5,150 km = 2,260 km thick | liquid iron–nickel |
| Inner core | 1,250 km | 5,150 → 6,371 km = radius 1,221 km | solid iron–nickel |
| Radius | 6,375 km | mean radius 6,371 km | — |
Reading Fig. 2.1 ‘The Earth's interior’ (page 14)A cut-away globe shows the crust, mantle, outer core and inner core as nested colours; beside it a wedge from surface to centre (marked 6,375 km) is labelled with boxes — oceanic crust 5 km, continental crust 30 km, lithosphere 100 km, asthenosphere 200 km, mantle 2,900 km, outer core 2,200 km, inner core 1,250 km — and six short definitions run below. The point: thin brittle skin, thick hot mantle, metal core. Our check: 30 + 2,900 + 2,200 + 1,250 = 6,380 km, 5 km more than the printed radius — fine for ‘approximate’ values; use the standard 6,371 km if asked.
Reading Fig. 2.2 ‘Movement of material below the crust’ (page 15)A wedge-shaped section from the surface to the core: a big yellow arrow marked ‘Total Interior Heat Flow’ with shares beside each layer — crust 24%, upper mantle 22%, lower mantle 32%, core 22% (our sum: 100%); curving red-and-blue loops in the mantle and smaller ones in the outer core show convection; red blobs near the top are ‘magma zones’; a key names three ways heat moves — conduction, convection and advection (material carrying heat upward, as magma does). The point: heat from inside drives slow circulation that moves plates. The percentages are the figure's own and undated — quote them as NCERT's.
Read carefully — interior
- The book first says plates move ‘over the molten mantle’ (p. 13), then that the mantle is ‘mostly solid’ and only the asthenosphere is semi-molten (p. 14). Safe line: ‘the rigid lithosphere moves over the weak, partly molten asthenosphere; the mantle as a whole is solid rock that flows very slowly’.
- Outer core = liquid; inner core = solid (enormous pressure keeps it solid despite the heat).
- Lithosphere ≠ crust: the lithosphere includes the top of the mantle.
2. Plate tectonics: plates, what moves them, and where they meet
In simple wordsLay crackers on a pot of thick soup that is gently simmering. The soup rises in the middle and sinks at the sides, and the crackers drift — some bump and pile up, some pull apart, some scrape past each other. Plates do the same, about as fast as your fingernails grow.
Plate tectonics says the outer layer is not one piece but several large and small plates moving slowly over the layer beneath, making mountains, earthquakes and volcanoes. Plates are massive slabs of solid rock moving a few centimetres a year; the book groups them as continental, oceanic and mixed (carrying both). Its seven major plates: Pacific, Eurasian, African, North American, South American, Indo-Australian and Antarctic. The book's driver is convection currents in the mantle: heat from the core makes material rise while cooler material sinks, pushing and pulling the plates. Where plates meet are plate boundaries — convergent (towards each other: continent–continent collision builds fold mountains such as the Himalaya; an oceanic plate meeting a continental one sinks beneath it, bringing volcanoes and earthquakes), divergent (apart: magma rises and forms new crust, as at the Mid-Atlantic Ridge) and transform (sliding past, crust neither made nor destroyed: mainly earthquakes, as on the San Andreas Fault in the United States).
⤵ From inner heat to a mountain range (the book's chain, with one Beyond-NCERT link)
Heat inside the Earthleft over from its formation and made by radioactive decay (Beyond NCERT)
Mantle convectionhot rock rises, cool rock sinks — very slowly, in the solid state
Plates movea few centimetres a year; sinking slabs also pull their plates (Beyond NCERT)
Convergefold mountains, trenches, volcanoes
Divergeridges, rift valleys, new crust
Slide pasttransform faults, earthquakes
Landforms and hazardsmountains, ocean basins, earthquake and volcano belts
| Major plate (Fig. 2.3, map described in words) | Continents on it (Let's Map) | Ocean floor on it | Motion shown by the map's arrows (broad) |
|---|---|---|---|
| Pacific | almost none (small coastal slivers †) | most of the Pacific Ocean floor | north-west, towards Asia's island arcs |
| Eurasian | Europe and most of Asia | parts of the Atlantic and Arctic floors | slow; others converge on it |
| African | Africa | parts of the Atlantic and Indian Ocean floors | north towards Eurasia |
| North American | North America, Greenland | western North Atlantic | west, away from the Mid-Atlantic Ridge |
| South American | South America | western South Atlantic | west, against the Pacific-side plates |
| Indo-Australian | India, Australia | much of the Indian Ocean floor | north to north-east, into Eurasia (the Himalaya) |
| Antarctic | Antarctica | the Southern Ocean floor | slow; ringed by ridges |
Reading Fig. 2.3 and the Let's Map box (page 16) — the world map described in words, not redrawnFig. 2.3 is a world map with each major plate in a pale colour (legend: North American, African, Eurasian, South American, Indo-Australian, Pacific, Antarctic) and minor plates in grey — small slabs such as those off western Central and South America, in the Caribbean, around Arabia and near the Philippines (names Beyond NCERT: Nazca, Cocos, Caribbean, Arabian, Philippine Sea, among others). Black arrows show directions: the Indo-Australian plate arrows point north into Asia; arrows either side of the mid-Atlantic point away from each other. Let's Map asks you to pick two plates and fill a table of their continents and oceans — our table above does it for all seven. The point: plates are not continents; most carry both land and ocean floor.
Positions side by side: who gave plate tectonics, and what drives the plates
- Authorship: the book credits W.J. Morgan. Historians of geology credit several near-simultaneous papers — Dan McKenzie and Robert Parker (1967), W. Jason Morgan (1968) and Xavier Le Pichon (1968) — building on Wegener's drift (1912–15), Holmes's mantle convection (1920s–30s) and Hess's sea-floor spreading (early 1960s) (kegy204 sets out the same list). Safe line: ‘plate tectonics emerged in 1967–68 (McKenzie and Parker, Morgan, Le Pichon)’.
- Driving force: the book's account is mantle convection (Arthur Holmes's idea). Many geophysicists since the 1970s (for example Forsyth and Uyeda, 1975) argue that slab pull — the weight of a sinking oceanic plate — and ridge push do most of the work, with convection as the larger system they belong to. Both are taught; an answer can name all three.
Read carefully — plates
- Seven major plates in the book, with Indo-Australian as one plate; many modern maps split it into Indian and Australian plates (kegy204). Say which you use.
- ‘Continental, oceanic, mixed’ is the book's grouping; in practice most big plates are mixed.
- Transform = no crust made or destroyed; divergent = made; convergent = destroyed (subducted) or crumpled.
- The Himalaya is a continent–continent collision — so it has few volcanoes but many earthquakes.
3. Earthquakes and volcanoes: where and why
In simple wordsBend a stick slowly: nothing happens, then — snap — and your hands jolt. Rocks along a plate edge bend and store strain for years, then slip in seconds: that jolt is an earthquake. Where a plate dives down and melts, the molten rock finds a way up: that is a volcano.
Plate movement forms mountains, valleys, ocean basins, volcanoes and earthquakes and explains how continents and oceans are arranged. Most earthquakes and volcanoes occur along plate boundaries, especially round the Pacific — the Ring of Fire. So the theory helps identify earthquake- and volcano-prone regions and manage the disasters. The book asks whether India faces earthquake risk: it has had major earthquakes with thousands of deaths, and a large one in a densely populated country can do severe damage (Fig. 2.5: Gujarat, 2001). A Don't Miss Out box adds that earthquakes were known in early India as bhūkampa (‘earth-shaking’), and that Varāhamihira's Bṛhatsaṃhitā gave a section to them.
| Belt on Fig. 2.4 (described in words) | Plate setting | What you see on the map |
|---|---|---|
| Ring of Fire (round the Pacific) | subduction of ocean plates under continents and island arcs | a near-continuous ring of black volcano triangles and red quake dots down the Americas' western side and from Alaska through Japan and the Philippines to Indonesia and New Zealand |
| Alpine–Himalayan belt † | continent–continent collision (Africa, Arabia and India into Eurasia) | a broad scatter of red quake dots from the Mediterranean through Iran and the Himalaya to Myanmar, with few volcanoes |
| Mid-ocean ridges | divergence | thin lines of quake dots down the middle of the Atlantic and through the Indian Ocean |
| East African Rift † | a continent starting to split | a short north–south chain of volcanoes and quakes in eastern Africa |
Reading Fig. 2.4, the three Let's Explore boxes and Fig. 2.5 (pages 16–17) — the map described in words, not redrawn
- Fig. 2.4: a world map with red dots (earthquake origins) and black triangles (active volcanoes). They crowd in narrow belts — round the Pacific rim, across the Mediterranean–Himalayan zone, along the mid-ocean ridges — and are sparse in the middle of continents. Compared with Fig. 2.3 (the first Let's Explore), the belts trace the plate boundaries — the correlation the book wants you to see. Our table above lists the belts.
- Second Let's Explore: name the continents and countries round the Ring of Fire — outline in the in-text section.
- Third Let's Explore and Fig. 2.5 ‘The extensive damage caused by the major earthquake in Gujarat in 2001’: rubble of flattened buildings beside cracked multi-storey blocks. The point: buildings, not shaking itself, kill people; India's risk is real. (Bhuj, 26 January 2001, magnitude 7.7; the USGS lists about 20,000 deaths — Beyond NCERT, verify the figure you quote.)
Reading the Varāhamihira box, Fig. 2.6 and Fig. 2.7 with its box (pages 18–19)
- Don't Miss Out — bhūkampa: Varāhamihira (6th century CE †) in the Bṛhatsaṃhitā noted changes in wind, rain, clouds, animal behaviour and planetary positions as signs of earthquakes, and grouped them under four forces — Vāyu (wind), Agni (fire), Indra (heaven/thunder) and Varuṇa (water) — each tied to constellations and regions. The book calls it an early attempt to blend observation with cosmological reasoning.
- Fig. 2.6 ‘Photograph showing the deposition by volcanic eruption’: a hill village of wooden houses, leafless trees and a lane, all coated in thick grey dust. The Let's Explore asks what caused it, what the grey powder is, and what it says about internal forces — answers in the in-text section.
- Fig. 2.7 ‘India's only mud volcano in Baratang in the Andaman and Nicobar Islands’ and its box: a low grey cone of dried mud inside a wooden fence, with mud bubbling out because of underground gas and pressure. The point: not every ‘volcano’ is fiery. See the trap below on ‘only’.
Positions side by side: early ideas and modern seismology
- The book: Varāhamihira's chapter shows early Indian observation of earthquake signs blended with cosmology.
- Modern seismology (for example the USGS and India's National Center for Seismology): earthquakes come from sudden slip on faults as plates move; animal behaviour and weather have not proved reliable predictors, and planetary positions are not used. No method can yet predict the time, place and size of an earthquake; scientists map hazard zones and some systems give seconds of early warning once shaking starts.
- Both can be stated: one as history of ideas, the other as present science.
Beyond NCERT — India's seismic setting, dated (check the latest)
- The Bureau of Indian Standards' code IS 1893 (Part 1): 2002 divides India into seismic zones II–V; zone V — the most severe — covers the north-east, parts of the Himalaya, Kachchh and the Andaman and Nicobar Islands. A revised zonation has been reported since — check the latest BIS code before quoting zones.
- Barren Island (Andaman Sea) is India's only confirmed active volcano (UPSC 2018 asked about it); the Baratang mud volcano is a different thing — gas-driven mud, not magma.
- Mount Everest's height: 8,848.86 m, announced jointly by Nepal and China in December 2020 — a reminder that the Himalaya is young and still rising, as India keeps pushing north (a few centimetres a year — the exact rates vary between studies).
Read carefully — earthquakes and volcanoes
- Magnitude (Richter or moment scale) measures energy released, on a logarithmic scale; intensity (Mercalli) measures shaking and damage at a place. +1 magnitude ≈ 31.6 × energy.
- ‘India's only mud volcano’ at Baratang: Baratang is the best known, but mud volcanoes have also been reported elsewhere in the Andaman Islands (for example near Diglipur — verify). Safe line: ‘the best-known mud volcano in India’.
- Earthquakes are caused by sudden movement along faults; landslides, eruptions and cyclones are not their usual cause (UPSC 1981).
- The 1991 Garhwal (Uttarkashi) earthquake came from the Indian plate pushing against Eurasia; UPSC 1992's key option says ‘Chinese plate’ — loose wording for the Eurasian plate, but still the right choice among the options.
4. Weathering and erosion — breaking and carrying
In simple wordsA clay pot left out in sun and rain cracks and crumbles where it stands — that is weathering. A stream then washes the crumbs downhill — that is erosion. One breaks; the other moves.
Weathering breaks rock at the surface into smaller pieces without moving them. Three kinds: physical (temperature changes, frost, wind), chemical (minerals change by reacting with water, air or acids, making new substances) and biological (plants, animals, micro-organisms — roots prising cracks apart). It shapes the surface and forms soil. Erosion wears away and carries soil and rock by water, wind, ice or waves: water erosion (rivers, rain, waves), wind erosion (dry, sandy areas), glacial erosion (ice scraping) and coastal erosion (waves on shores). Together they wear down mountains, carve valleys, form plains and create caves, cliffs and deltas. Erosion hits livelihoods: farmers lose fertile topsoil and yields; river and coastal dwellers lose land, homes and roads; construction and mining face unstable ground; tourism and fishing lose beaches and rivers.
⤵ The surface conveyor belt (the book's processes in order)
Weatheringrock breaks in place: physical, chemical, biological
Erosionan agent picks the pieces up: water, wind, ice, waves
Transportcarried downslope, downstream or downwind
Depositiondropped where the agent slows: floodplains, deltas, dunes, moraines, beaches
Gradationhighs lowered, lows filled — the surface is levelled over time
| Type of weathering (Fig. 2.8) | How it works | Example † |
|---|---|---|
| Physical | heating and cooling, water, wind, ice expansion split rock | frost wedging in Himalayan crags; onion-peel exfoliation of granite in hot deserts |
| Chemical | reactions with water, air, acids form new substances | rain with dissolved CO₂ dissolves limestone; iron in rock rusts (oxidation) |
| Biological | plants, animals, microbes break rock | a peepal tree splitting an old wall; burrowing animals; lichens |
Reading Fig. 2.8, Fig. 2.9 and the Let's Explore (pages 20–21)
- Fig. 2.8 ‘Types of weathering’: three round illustrations — a mushroom-shaped rock pillar with a cracked boulder (physical: heating and cooling, water, wind, ice expansion), a worn stone statue with a corroded face (chemical: substances in air and rain), and a tree whose roots grip and split a boulder (biological: plants and animals).
- Fig. 2.9 ‘Erosion caused by (a) water and (b) wind’: (a) a deep, raw gully cut into soil with a strip of grass; (b) trees half-hidden in a haze of blowing dust over bare ground. The point: water cuts channels; wind strips loose soil.
- Let's Explore: how are farmers affected by water and wind erosion? Outline in the in-text section.
Reading the Don't Miss Out box on traditional conservation and the three margin glossaries (page 21)The box says the Sindhu-Sarasvatī civilisation used contouring, bunding, terracing, dams and canals for water management; that Sanskrit texts — the Vedas, Kṛṣiparāśara, Kauṭilya's Arthaśāstra and treatises such as Vṛkṣāyurveda — document such practices, the Arthaśāstra grading land by fertility; and that the Zabo system of Nagaland uses earthen bunds on hillslopes, with check dams on small streams to slow water, trap sediment and recharge groundwater. Margin glossaries define contouring (continuous contour trenches dug along a hillside to hold rainwater and stop erosion), bunding (earthen embankments along contour lines to slow run-off) and terracing (level steps cut into a slope). The point: soil and water conservation is old, local knowledge as well as modern practice.
Read carefully — weathering, erosion and conservation
- Weathering = no movement; erosion = movement. Don't swap them.
- Contour bunding is for sloping and hilly land (UPSC 1982); UPSC 2013 offered only desert margins, flood plains and scrublands, so the key was ‘none of the above’.
- Rain and chemical weathering (UPSC 2024): rainwater carries dissolved carbon dioxide (carbonic acid → carbonation) and dissolved oxygen (→ oxidation). The stored key says both are true but only one explains the weathering; since both drive chemical weathering, many argue both explain it — the key is debatable. Strategy: know both mechanisms; follow the official key if one is published.
- Chronology in the box: the box sets Harappan practices beside Sanskrit texts, but those texts are far later than the Sindhu-Sarasvatī (Harappan) civilisation (mature phase c. 2600–1900 BCE, lehs101); the Kṛṣiparāśara and Vṛkṣāyurveda are usually dated to the 1st millennium CE or later (dates debated). Safe line: ‘archaeology shows Harappan water management (for example Dholavira's reservoirs †); later Sanskrit texts describe farming and soil practices of their own times’.
5. Running water — valleys, waterfalls, meanders and deltas
In simple wordsA river is like a delivery truck. In the hills it races downhill, chipping at the road (erosion). On the plains it slows and swerves, dropping a few parcels on the bends. At the sea it stops and unloads everything — a delta.
The book lists five agents of gradation that wear down, carry and deposit material and so level the surface: running water (valleys and plains), glaciers (U-shaped valleys), wind (deserts), sea waves (cliffs, beaches, bays) and groundwater (caves, sinkholes in limestone). Rivers work by erosion, transport and deposition. In the upper course, steep gradients and strong erosion form V-shaped valleys, waterfalls and rapids. In the middle course the river meanders, forms oxbow lakes and floodplains as it loses energy. In the lower course it slows further and deposits deltas, levees and alluvial fans (the book's list — see the trap). A waterfall forms where hard rock resists and softer rock below is worn away, making a sudden drop; falls draw tourists, can generate hydroelectricity and often have cultural or religious meaning. A meander is a bend made by lateral erosion and deposition: the outer bank is eroded, the inner bank built up; meanders leave fertile soil for farming, shape settlements and serve navigation, irrigation and tourism — the Grand Anicut (Kallanai) in Tamil Nadu is the book's example of river irrigation. A delta is a fan or triangle of sediment at a river's mouth: very fertile (rice, jute), rich in fish where fresh and salt water mix, densely settled and busy with trade — but flood-prone.
⤵ How a meander becomes an oxbow lake (Fig. 2.11, in steps)
Bendwater swings to the outer bank
Outer bank eroded, inner bank builtthe loop grows and the neck between two loops narrows
Flood breaks through the neckthe river takes the short, straight path
Ends silt upthe old loop is sealed off
Oxbow lakea curved lake on the floodplain
Reading Figs 2.10–2.13 and the landforms-and-history box (pages 22–25)
- Don't Miss Out — landforms and history: river plains (Ganga, Nile, Brahmaputra, Indus) cradled farming and early cities; mountains were barriers and protectors yet allowed exchange through passes ‘like the Khyber’; deserts such as the Thar limited big settlements but ‘encouraged trade routes such as the Silk Route’; coasts and harbours helped south Indian kingdoms flourish. See the trap below on two slips.
- Fig. 2.10 ‘Waterfall’: a labelled drawing (1 river, 2 hard rock, 3 gap, 4 plunge pool, 5 river) beside a photograph of a tall fall dropping down a forested cliff. Point: hard cap, soft base, plunge pool.
- Fig. 2.11 ‘Meander’: a drawing of a looping river (1 oxbow lake, 2 steep bank, 3 river, 4 bar) beside an aerial photo of a river winding through green plains. Point: erosion outside, deposition inside, cut-off loops.
- Fig. 2.12 ‘Delta’: a drawing of a river splitting into distributaries around islands and bars before the sea (1 river, 2 distributary, 3 islands/bars, 4 sea). Point: a river drops its load and divides.
- Fig. 2.13 ‘Sundarbans delta’ and its Let's Explore: a satellite view of a dark-green, finely branching maze of channels and islands meeting a turquoise sea. Point: the world's great mangrove delta — outline in the in-text section.
Beyond NCERT — Indian examples, dated
- Sundarbans: the delta of the Ganga–Brahmaputra(–Meghna), shared by India and Bangladesh; the largest mangrove forest; home of the Royal Bengal tiger. Indian Sundarbans National Park: UNESCO World Heritage Site 1987; Sundarban Biosphere Reserve 1989; Ramsar site 2019.
- Grand Anicut (Kallanai): a stone weir across the Kaveri near Tiruchirappalli, traditionally attributed to the Chola king Karikala and commonly dated to about the 2nd century CE (dates vary); remodelled in the 19th century under the British engineer Arthur Cotton.
- Falls: Jog (Sharavati), Dhuandhar (Narmada, near Jabalpur), Hundru (Subarnarekha). Oxbow-type lake: Kanwar (Kabar) Taal, Bihar, linked to the Gandak's meanders.
Read carefully — rivers and the history box
- Alluvial fans form where a stream leaves steep hills for a plain and its slope suddenly drops — at the foot of the mountains, not in the lower course near the sea (kegy206). Safe line: ‘fans at the break of slope; deltas at the mouth’.
- Maturity of a river is recognised by meanders, not V-valleys or gorges (UPSC 1990).
- Khyber Pass is not in the Himalaya: it crosses the Spin Ghar (Safed Koh) range on the Afghanistan–Pakistan border, west of the Indus. And the north-western passes were routes for invaders as well as traders, so ‘shielded from invasions’ needs care.
- Silk Route: its main overland routes crossed the deserts of Central Asia (Taklamakan, Gobi), not the Thar; the Thar had its own caravan routes. Safe line: ‘deserts limited settlement but caravan trade crossed them — the Silk Routes in Central Asia’.
6. Waves and currents — beaches, cliffs, arches and stacks
In simple wordsWaves are like a sculptor with a hammer and a broom. The hammer (breaking waves, flung pebbles) cuts caves and cliffs into hard headlands; the broom (gentle waves, currents) sweeps sand into quiet bays to make beaches.
Waves and currents reshape the coastal zone. Deposition builds beaches (sand, pebbles or rocks along a shore) and sand bars; beaches draw tourists, support fishing, supply sand and shells, and act as natural barriers that protect settlements from waves. Erosion makes cliffs (steep faces as waves undercut the base), wave-cut platforms (flat rock left as cliffs retreat), caves (in weak rock), arches (where caves on opposite sides of a headland meet) and stacks (pillars left when arches collapse). Some coasts are tourist draws; others need protection. Waves and currents return in Part 2 of the book.
Reading Figs 2.14–2.16 (pages 26–27)
- Fig. 2.14 ‘Beach’: a drawing of a bay between headlands with a beach, a river entering, and a sand bar curving out with a ‘free end’ (labels 1 beach, 2 bay, 3 sea, 4 headland, 5 sand bar, 6 free end, 7 river), beside a photo of a curving sandy shore and wooded headland.
- Fig. 2.15 ‘Sea arch and sea stack’: a drawing of a headland with an arch and a separate stack, high- and low-tide levels marked, beside a photo of a rock arch standing in the sea.
- Fig. 2.16 ‘Sea cliff and shore platform’: a drawing of a headland with a cliff, a sea cave at its foot and a flat platform exposed at low tide, beside a photo of a rocky ledge at the sea's edge. Point: erosion forms and deposition forms sit side by side.
⤵ Cave → arch → stack (the book's sequence)
Waves find weak rockjoints and faults at the base of a headland
Sea cavehollowed out by pounding and abrasion
Archcaves on both sides of the headland meet
Stackthe arch roof falls, leaving a pillar
Stump †the stack is worn down to a low rock, covered at high tide
Read carefully — coasts
- A sand bar joined to the land at one end with a free end in the sea (Fig. 2.14) is usually called a spit; a bar can also run across a bay (a bay-bar) or lie offshore (Beyond NCERT, kegy206).
- Cave, arch and stack are erosional; beach, bar and spit are depositional.
- The wave-cut platform marks where the cliff used to be.
7. Glaciers — U-shaped valleys, cirques and moraines
In simple wordsA glacier is a river of ice that moves a few metres a year but carries rocks frozen into its base like sandpaper. A river cuts a narrow V; a glacier sands the whole valley into a wide U — and dumps the scraped rubble where it melts.
Glaciers erode as they move. The book's erosional landforms: U-shaped valleys (river valleys widened and deepened), cirques (bowl-shaped hollows at a glacier's head), aretes (sharp ridges between valleys), hanging valleys (where smaller glaciers met larger ones) and fjords (deep, narrow inlets where the sea floods glacial valleys). People use them for trekking, skiing and mountaineering; fjords for harbours and fishing; some valley soils for farming; and glaciers feed rivers that sustain populations downstream. Moraines are deposits of rock, soil and debris (till) left as a glacier melts: lateral along the sides, terminal at the furthest point of advance, medial where two glaciers' lateral moraines join. They give fertile soil and can dam lakes used for water, irrigation and sometimes hydropower.
Reading Figs 2.17–2.20 and the Think About It box (pages 27–29)
- Fig. 2.17 ‘Glacial landforms’: a drawing of snowy peaks (1 arete, 2 cirque, 3 pass) beside a photo of a sharp pyramid peak above a lake.
- Fig. 2.18 ‘U-shaped valley’: a drawing (1 hanging valley, 2 U-shaped valley, 3 glacier, 4 glacial ice) beside a photo of a broad ice-filled valley.
- Fig. 2.19 ‘Moraines’: a drawing of two glaciers joining with dark debris stripes (1 lateral, 2 glacier, 3 mid moraine, 4 glacier, 5 terminal moraine, 6 river) beside a photo of a glacier streaked with debris bands.
- Think About It and Fig. 2.20: a photograph of a narrow Himalayan valley choked with grey debris-laden water, a road and buildings on the slopes; the box recalls the February 2021 Chamoli flood in Uttarakhand — lives and livestock lost, buildings, roads, bridges and hydel projects damaged — and asks for its causes. See the debate below.
Positions side by side: what caused the Chamoli flood of 7 February 2021?
- Early reports spoke of a ‘glacier burst’ or a glacial lake outburst.
- Detailed studies — notably an international team led by Dan Shugar (Science, 2021) — concluded that a huge rock-and-ice avalanche broke from Ronti peak above the Rishiganga valley and turned into a debris flow; no large glacial lake burst. It damaged the Rishiganga and Tapovan–Vishnugad hydropower projects; about 200 people were killed or went missing (verify the figure you quote).
- Contributing factors argued by different researchers: steep, fractured rock weakened by freeze–thaw and warming; heavy snow days before; and, in some views, the scale of construction in a fragile valley. NDMA and state agencies stress early warning and hazard mapping. Present these side by side; don't assign blame.
Read carefully — glaciers
- ‘Mid moraine’ in Fig. 2.19 = medial moraine in the text.
- Fjord = a drowned glacial valley (Norway, Chile, New Zealand) — not a drowned river valley (that is a ria †). UPSC Mains 2023 asked how fjords form and why they are so scenic.
- Hanging valleys often end in waterfalls into the main U-valley.
- Eskers and drumlins (UPSC 1990) are other glacial deposits — not in this book; see kegy206.
8. Wind — yardangs, dunes and oases
In simple wordsWind is a sandblaster with no off switch. It lifts loose sand and fine soil, scours soft rock, polishes stones and piles sand into dunes that crawl across the desert.
Strong winds pick up loose sand and soil and shape erosional landforms: yardangs (streamlined rock ridges), ventifacts (rocks polished and shaped by sandblasting), deflation hollows or blowouts (shallow depressions where loose material is removed) and desert pavements (flat stony surfaces left when fine particles blow away). They shape settlement and farming in dry lands and draw tourists and geologists. Dunes are hills or ridges of wind-blown sand: barchan (crescent-shaped; limited sand, one wind direction), longitudinal (long ridges parallel to the wind), star (several arms; winds from many directions) and parabolic (U-shaped, often anchored by vegetation). The book says dunes act as natural barriers against desertification and wind erosion, give space for tourism and adventure sports, shelter coastal settlements from sea winds and waves, and supply construction sand.
| Dune | Shape | Wind and sand | Where it is in the book |
|---|---|---|---|
| Barchan | crescent, horns pointing downwind | one steady wind, limited sand | text and Fig. 2.23 |
| Transverse † | long ridges across the wind | one wind, plenty of sand | Fig. 2.23 only |
| Longitudinal (seif †) | long ridges along the wind | less sand, winds converging | text only |
| Star | central peak with several arms | winds from many directions | text and Fig. 2.23 |
| Parabolic | U-shape, arms pointing upwind, held by plants | vegetation anchors the arms | text only |
Reading Figs 2.21–2.23 (pages 29–30)
- Fig. 2.21 ‘Yardang’: a drawing of a ridge with alternating hard and soft rock bands and the wind direction (1 yardang, 2 wind, 3 hard rock, 4 soft rock, 5 hard rock), beside a photo of a desert plain studded with low, flat-topped ridges.
- Fig. 2.22 ‘Oasis’: a drawing of a deflation hollow scooped down to the water table, with a pool and palms (1 wind, 2 oasis, 3 blown sand, 4 water table), beside a photo of a green pool among sand dunes.
- Fig. 2.23 ‘Dunes’: three small block drawings — barchan (with ‘horn’, ‘wind’ and ‘dune’ labels), transverse and star dunes — above three photographs of each. Point: dune shape follows wind direction and sand supply.
Read carefully — wind
- Barchan (Barkhan) = crescent dune; its horns point downwind (UPSC 1991). Parabolic dunes are the opposite — arms point upwind.
- The text names longitudinal and parabolic dunes; the figure shows transverse instead. Learn all five.
- ‘Dunes are barriers against desertification’: vegetated, stable dunes protect land; moving dunes bury fields and roads and spread desert conditions. Safe line: ‘stabilised dunes protect; shifting dunes encroach’.
- An oasis forms where wind deflation lowers the ground to the water table.
9. Underground water — karst caves and sinkholes
In simple wordsDrop a piece of chalk into lemon juice and watch it fizz away. Rainwater is very weakly acidic, and limestone is chemically like chalk. Over thousands of years it eats out caves, and as it drips inside, it rebuilds icicles of stone.
In limestone and other soluble rocks, underground water makes karst topography by chemical weathering and erosion. Its landforms: caves (hollows dissolved by acidic water), stalactites (icicle-shaped, hanging from the roof), stalagmites (rising from the floor), sinkholes or dolines (depressions where the ground collapses into a cavity) and underground rivers flowing through cave systems. They supply fresh water, attract tourists and adventurers, interest geologists, and some caves have cultural or religious significance. A Let's Explore asks you to identify which agent shaped the landforms near your school or home.
Reading Figs 2.24–2.26 and the Let's Explore boxes (pages 31–32)
- Fig. 2.24 ‘Cave’: a drawing of a cave in rock (1 stalactite, 2 pillar, 3 cave, 4 stalagmite, 5 cave mouth) beside a photo of a lit cave with a person among glistening columns.
- Fig. 2.25 ‘Sinkholes’: a block drawing of a surface pitted with round hollows beside a photo of a red, gullied landscape with pits.
- Fig. 2.26 ‘Underground river’: a photo of a huge, green-walled cave passage with a path and tiny figures, daylight at the far end.
- Two Let's Explore boxes: identify the agent behind landforms near you; and complete the disaster exercises with newspapers, atlases and books, listing disaster-prone areas of India and the world with mitigation measures and recent examples (our table in section 10).
Read carefully — karst
- Stalactites hang from the ceiling; stalagmites rise from the ground; together they make a pillar (column).
- Karst is named after the Kras/Karst limestone plateau on the Slovenia–Italy border (Beyond NCERT).
- Indian karst examples (Beyond NCERT): Borra Caves (Andhra Pradesh), Belum Caves (Andhra Pradesh) and the long cave systems of Meghalaya.
10. Landforms and disasters — landslides, avalanches, GLOFs, dust storms
In simple wordsA heap of wet sand on a slope stays put until you add one more bucket of water or give it a kick — then it slides. Hills, snowfields, glacial lakes and dry fields all hold stored energy or loose material; a trigger releases it as a disaster.
The book links four disasters to landforms. Landslides: heavy, continuous rain soaks slopes, adding weight and cutting friction; earthquakes and eruptions shake slopes; steep slopes and loose, weathered rock add risk; deforestation, mining, road-building and unplanned hillside construction, poor drainage and bad land use make it worse. Avalanches: heavy snow in a short time overloads a snowpack, especially on weak layers; sudden warming melts and loosens it; wind piles snow unevenly; earthquakes, vibrations, skiing, trekking and construction can trigger it. GLOFs: warming melts glaciers, swelling lakes behind dams of ice or loose moraine; heavy rain or snow adds water; earthquakes, avalanches or landslides strike or weaken the dam, which collapses and releases a sudden flood downstream. Dust storms: strong winds lift loose, dry soil; drought and low rain dry it; sparse cover from deforestation, overgrazing or poor farming exposes it; climate change and extreme weather may make storms more frequent and intense.
⤵ Anatomy of a GLOF (the book's chain)
Warmingglaciers melt faster
Lake growsbehind a dam of ice or loose moraine
Extra loadheavy rain or snow fills it further
Triggerearthquake, avalanche or landslide hits the lake or dam
Dam failswater released all at once
Flood downstreamroads, bridges, dams and villages swept away
⤵ Landslide causes — the book's two groups
Naturalheavy, continuous rain; earthquakes; eruptions; steep slopes; loose, weathered rock
Humandeforestation; mining; road-cutting; unplanned hillside building; poor drainage; bad land use
Slope loses its gripmore weight, less friction, no roots to hold soil
Slope failssudden slide of rock, soil and debris
| Disaster (book's activity) | Prone areas (Beyond NCERT †) | Mitigation measures † | Recent examples (Beyond NCERT — verify details) |
|---|---|---|---|
| Landslides | Himalaya (Uttarakhand, Himachal, J&K, Sikkim), north-eastern hills, Western Ghats and the Nilgiris | hazard mapping; drainage; retaining walls; afforestation; no building on steep or drainage paths; early warning; NDMA's landslide guidelines | Malin, Pune, July 2014; Wayanad, Kerala, 30 July 2024 |
| Avalanches | snow-bound Himalaya — J&K, Ladakh, Himachal, Uttarakhand, Sikkim | avalanche forecasting; snow fences and barriers; closing routes in danger periods; training for troops and trekkers | Siachen, February 2016; Draupadi ka Danda-II, Uttarakhand, October 2022 |
| GLOFs | high Himalayan valleys with glacial lakes — Sikkim, Uttarakhand, Himachal, Ladakh, Arunachal | lake monitoring by satellite; lowering lake levels; early-warning sirens downstream; siting dams and roads with care | Kedarnath (Chorabari lake), June 2013; South Lhonak lake, Sikkim, 3–4 October 2023, which destroyed the Teesta-III dam at Chungthang |
| Dust storms | Thar desert and margins — Rajasthan, Gujarat, Punjab, Haryana, western Uttar Pradesh, Delhi | shelterbelts and windbreaks; stabilising dunes with grasses; controlling overgrazing; weather warnings | Rajasthan and Uttar Pradesh, early May 2018 (over 100 deaths reported — verify) |
Reading Figs 2.27–2.30 and the four activity frames (pages 33–36)
- Fig. 2.27 ‘A landslide’: a steep slope of broken rock and boulders spilling onto a mountain road with stopped vehicles. Fig. 2.28 ‘An avalanche’: a cloud of snow pouring down a white mountain face beside a photo of rescuers in snow gear carrying a person. Fig. 2.29 ‘A GLOF’: an aerial view of a mountain town surrounded by a broad grey spread of boulders and debris. Fig. 2.30 ‘A dust storm’: trees fading into a thick orange-brown haze.
- Each page ends with blank lines for prone areas, mitigation measures and recent examples — our table above fills them (Beyond NCERT; check details).
Beyond NCERT — the legal frame, as bare factsThe Disaster Management Act, 2005 set up the National Disaster Management Authority (NDMA), state and district authorities and the National Disaster Response Force. NDMA issues hazard-wise guidelines (including on landslides and on glacial lake outburst floods) and public posters such as the chapter's landslide poster. Check NDMA's website for the current versions.
Read carefully — disasters
- A GLOF needs a lake behind an ice or moraine dam; a cloudburst flood or a rock–ice avalanche (Chamoli 2021) is different.
- The summary says ‘glacial lake outflows’ and ‘sandstorms’; the section titles say GLOFs and dust storms — use the section terms.
- Himalayan landslides: young, fractured, tectonically active rock + steep slopes + monsoon or cloudburst rain + road-cutting and deforestation (UPSC Mains 2016).
In-text questions and activities — answer outlines
One Let's Map table, nine Let's Explore prompts and one Think About It. Outlines below.
Let's Map (p. 16): Pick any two plates from Fig. 2.3 and fill in their continents and oceans.
Example: Indo-Australian — continents India and Australia; ocean floor of much of the Indian Ocean. South American — South America; western South Atlantic. All seven are in our table in section 2.
Let's Explore (p. 16): Compare the plate map (Fig. 2.3) with the earthquake and volcano map (Fig. 2.4). What correlation do you observe?
The dots and triangles fall mainly along plate edges: round the Pacific (subduction — the Ring of Fire), along the Alpine–Himalayan collision belt (many quakes, few volcanoes), and down mid-ocean ridges (divergence). Plate interiors are quiet. So plate movement explains where quakes and volcanoes occur.
Let's Explore (p. 17): Which continents and countries lie around the Ring of Fire?
North America (USA — Alaska and the west coast; Canada), Central America (Mexico, Guatemala and neighbours), South America (Colombia, Ecuador, Peru, Chile), and Asia–Oceania (Russia's Kamchatka, Japan, the Philippines, Indonesia, Papua New Guinea, New Zealand), plus Antarctica's Pacific margin. Check with an atlas or globe.
Let's Explore (p. 17): Does India have a risk of earthquakes? Which region is more vulnerable, and why are lives at risk?
Yes. Most vulnerable: the Himalayan belt and north-east, Kachchh and the Andaman and Nicobar Islands (highest seismic zone), where the Indian plate pushes into Eurasia or subducts. Lives are at risk because of dense population, weak or unreinforced buildings, unplanned construction on slopes and soft soils, and low preparedness — buildings kill, not the shaking itself.
Let's Explore (p. 18, Fig. 2.6): What caused this situation? What could the grey powder be? What does it tell us about the Earth's internal forces?
A volcanic eruption; the powder is volcanic ash (fine fragments of rock and glass thrown out and carried by wind); it shows that heat and pressure inside the Earth can force molten rock and gas out violently and cover whole landscapes.
Let's Explore (p. 21): How are farmers affected by erosion due to water and wind (Fig. 2.9)?
Water: gullies cut fields, topsoil and fertiliser wash away, yields fall, silt chokes tanks and canals. Wind: fine fertile soil blows away, seedlings are buried or sand-blasted, dust spoils crops; in both cases land may have to be abandoned. Remedies: bunding, terracing, cover crops, shelterbelts.
Let's Explore (p. 25): What is unique about the Sundarbans delta, and why is it popular with tourists?
It is the delta of the Ganga–Brahmaputra(–Meghna), shared by India and Bangladesh; the world's largest mangrove forest; a maze of tidal channels and islands; home of the Royal Bengal tiger, estuarine crocodiles and many birds; a UNESCO World Heritage Site (1987). Tourists come for boat safaris, tigers, birds and the mangrove landscape.
Think About It (p. 29): Find out the reasons that led to the sudden flood in Chamoli district in February 2021.
On 7 February 2021 a massive rock-and-ice avalanche fell from Ronti peak into the Rishiganga valley and became a fast debris flood; it hit the Rishiganga and Tapovan–Vishnugad hydro projects. Background factors: steep, fractured rock, freeze–thaw, warming, recent snow; some researchers also point to construction in a fragile valley. Early reports called it a glacier burst or GLOF; detailed studies found no lake outburst.
Let's Explore (p. 32): Observe the landforms around your school or residence and identify the agent that made them.
Example: a gully on a slope → running water; sand ridges near the coast → wind and waves; a rounded hill with boulders → weathering; river terraces or a floodplain → river deposition. Note the landform, the agent, and the evidence.
Let's Explore (p. 32): Complete the disaster exercises — prone areas, mitigation and recent examples for India and the world.
See the table in section 10 for India. World examples †: landslides — Kerala-type rain-triggered slides worldwide, Hong Kong's slope programme; avalanches — the Alps, Himalaya; GLOFs — Nepal and Bhutan Himalaya, Peru's Andes; dust storms — the Sahel, Arabia, northern China. Quote the year with each.
Questions and activities (pages 37–38) — answer outlines
Fifteen questions and activities, after a five-point Before we move on summary. Try first, then open.
1. What are the sources of energy that are required to cause movements associated with the internal forces of the Earth?
The Earth's internal heat: heat left over from the planet's formation (primordial heat) and heat from the decay of radioactive elements (uranium, thorium, potassium) in the crust and mantle, plus heat released as the core slowly crystallises (Beyond NCERT). This heat drives mantle convection, and gravity pulls sinking slabs (slab pull) — moving plates and causing folding, faulting, earthquakes and volcanoes.
2. Relate the physiographic divisions you have studied in earlier grades with the endogenic forces responsible for their origin.
Himalaya — folding and thrust faulting as the Indian plate collides with Eurasia. Northern Plains — a down-warped trough (foredeep) in front of the rising Himalaya, filled by river deposits. Peninsular Plateau — an old, stable block of the Gondwana landmass, uplifted and faulted; the Deccan Traps from fissure volcanism; rift valleys of the Narmada and Tapi from faulting. Coastal plains — faulting and sea-level change along the plateau's edges. Islands — the Andaman and Nicobar chain from plate convergence (with Barren Island's volcano); Lakshadweep from coral growth (kegy102).
3. Why and where do earthquakes occur frequently? Is it possible to predict earthquakes?
Why: plates lock and store strain at their edges, then slip suddenly along faults. Where: plate boundaries — the Ring of Fire round the Pacific, the Alpine–Himalayan belt (including India's Himalaya and north-east), mid-ocean ridges and transform faults such as San Andreas. Prediction: no method can yet reliably predict the exact time, place and size; scientists estimate long-term probabilities, map hazard zones, and some systems give a few seconds' warning after a quake begins. So preparedness — safe buildings and drills — matters most.
4. “Plate movements are responsible for the distribution of earthquakes and volcanoes.” Explain.
Compare Figs 2.3 and 2.4: quakes and volcanoes cluster on boundaries. Convergent: subduction melts the sinking plate → volcanic arcs and deep quakes (Ring of Fire); continent–continent collision → many quakes, few volcanoes (Himalaya). Divergent: magma rises → ridge volcanoes and shallow quakes (Mid-Atlantic, Iceland). Transform: plates grind past → quakes, no volcanoes (San Andreas). Exceptions such as hotspots (Hawaii †) are few. Hence the belts trace the plate edges.
5. Draw and label a diagram of a meander and a delta.
Meander: a looping channel; label the outer bank (steep, eroded — river cliff), inner bank (gentle — bar/point bar), the direction of flow, the narrowing neck, and an oxbow lake where a loop has been cut off. Delta: a river splitting into distributaries; label the main river, distributaries, islands/bars and the sea; show the fan or triangle shape. Draw your own in the notebook (our cross-section and flow in section 5 help).
6. How are deforestation and erosion associated with each other? Explain.
Trees and their roots bind soil, their canopy breaks raindrops, leaf litter soaks up water and roots let it sink in. Remove them and rain hits bare soil, run-off speeds up, gullies form, topsoil washes away; on slopes, landslides increase; in dry areas, wind blows away loose soil (dust storms). Eroded silt then fills rivers and reservoirs, worsening floods. So deforestation causes and speeds erosion; afforestation reverses it.
7. Develop a plan to protect the land in your local area from erosion.
Survey: where is soil being lost (slopes, riverbanks, bare plots)? Measures: plant trees and grasses; contour bunding and trenches on slopes; terracing; check dams on small streams; mulching and cover crops; windbreaks in dry areas; stop overgrazing; repair drains. People: who does what (school, panchayat, farmers); timeline; how to check results (photos before and after).
8. Which disasters might you experience in your region? Discuss a mitigation plan in class.
Identify local hazards (floods, landslides, cyclones, earthquakes, heatwaves, dust storms). Plan: risk map of the locality drawn in your notebook; safe spots and evacuation routes; emergency kit; warning sources (IMD, NDMA apps, radio); roles in school; drills; long-term steps (drainage, safe construction, tree cover).
9. Prepare a model of landforms created by underground water.
Use a box with layered clay or plaster as limestone: hollow out a cave with stalactites (hanging) and stalagmites (rising), one pillar, a sinkhole at the surface and a blue channel for an underground river; label each and add a card on how acidic water dissolves limestone.
10. What precautionary measures will you take if you are staying in an earthquake-prone region?
Before: earthquake-resistant building (follow the BIS code), fix heavy furniture, know safe spots, keep an emergency kit, practise drills. During: Drop, Cover, Hold under a sturdy table; keep away from windows; if outdoors, move to open ground away from buildings and wires; don't use lifts. After: check for injuries and gas leaks, expect aftershocks, follow official advice.
11. Prepare a map showing landform-associated disasters that happened in the current calendar year.
Draw your own outline in the notebook; mark each event with a symbol (landslide, avalanche, GLOF, dust storm, flood), date and place from newspapers; add a legend and a short table. Note which landforms (steep slopes, glacial valleys, deserts) the events cluster on.
12. Create a poster showing landforms considered sacred or important in your region, with associated folk stories.
Pick 3–4 landforms (a hill, river confluence, cave, waterfall, lake); draw or photograph each; write the folk story in a few lines, the landform's type and how it formed; add how people protect or use it.
13. Document a case of a disaster that hit your region in the past, highlighting its effects on human activities.
Frame: what, when, where (date); cause (natural and human); effects on homes, farming, transport, schools, health, jobs, migration; response (relief, rebuilding); lessons learnt. Use interviews, newspapers and official reports.
14. Translate the landslide poster into your native language and display it at home.
The NDMA poster ‘Landslide — Ready Now to stay secure’ gives Before (grow trees, follow alerts, keep drains clean, watch for cracks and muddy water, don't build near steep slopes), During (stay calm, stay together, move away from the slide path quickly, inform the tehsil) and After (avoid loose material and wires, move away from the slide path, help the injured safely, don't drink contaminated water). Translate each point.
15. Group projects on water, wind and glacier: causes, impact on human life and environment, and mitigation.
Each group: landforms and processes of its agent; hazards (floods and erosion; dust storms and desertification; avalanches and GLOFs); impacts on people, farming, infrastructure and ecosystems with an Indian example and year; mitigation (structural and non-structural); a poster or model and a two-minute presentation.
Reading ‘Before we move on’ and the landslide poster (pages 37–38)
- Before we move on: five points — layers; internal forces (earthquakes, volcanoes, folding, faulting) ‘responsible for the movement of the crust’; external forces carving smaller landforms; agents of gradation; four disasters. Note: earthquakes and volcanoes are results of crustal movement as well as forces that reshape land — the energy behind them is internal heat (Q1).
- Poster (NDMA): a photo of a hill road buried by rockfall above a three-column Before / During / After checklist and the slogan ‘Be Smart, Be Prepared’. The point: preparedness saves lives.
⤵ Answer frame for any landform question
Definewhat the landform is, in one line
Agent and processwhich agent; erosion or deposition; why there
Diagrama labelled cross-section or sketch
Examplean Indian and a world example, with care over names
Human linkuses (farming, water, tourism) and hazards, with mitigation
What to remember
Numbers
Crust30–40 km under continents, 5–7 km under oceans (book)
Lithosphere≈ 100 km = crust + upper mantle; asthenosphere below (Fig. 2.1: 200 km)
Fig. 2.1 layersmantle 2,900; outer core 2,200; inner core 1,250; radius 6,375 km (approx.) — standard radius 6,371 km †
Standard depths †core–mantle boundary ≈ 2,890 km; inner core from ≈ 5,150 km
Fig. 2.2 heat sharescrust 24%, upper mantle 22%, lower mantle 32%, core 22% (= 100%)
Plates7 major; move a few cm a year; 3 boundary types
Plate tectonics †1967–68: McKenzie & Parker, Morgan, Le Pichon (book credits Morgan)
Bhuj earthquake †26 Jan 2001, magnitude 7.7 (USGS)
Largest Indian-region quakes †Assam–Tibet 1950, 8.6; Sumatra–Andaman 2004, 9.1
Magnitude step †+1 ≈ 10 × amplitude, ≈ 31.6 × energy
Weathering / erosion / agents3 kinds / 4 kinds / 5 agents
River coursesupper: V, falls, rapids; middle: meanders, oxbows, floodplains; lower: deltas, levees
Moraineslateral, medial, terminal
Dunesbarchan, longitudinal, star, parabolic (text) + transverse (figure)
Disasters4: landslides, avalanches, GLOFs, dust storms
Chamoli †7 Feb 2021 — rock-and-ice avalanche; South Lhonak GLOF, Sikkim, Oct 2023
Everest †8,848.86 m (Nepal–China, Dec 2020)
One-liners
- Rigid lithosphere rides on a weak asthenosphere — plates.
- Convergent destroys or crumples, divergent creates, transform slides.
- Quakes and volcanoes trace plate edges — the Ring of Fire most of all.
- Weathering breaks in place; erosion carries away.
- Rivers erode in the hills, swing in the middle, build at the mouth.
- Waves cut cave, arch, stack; sweep beaches into bays.
- Glaciers turn V into U and drop moraines.
- Wind carves yardangs, piles barchans, scoops oases.
- Acidic water dissolves limestone into karst.
- Landslides, avalanches, GLOFs and dust storms are landform hazards — triggers plus human pressure.
Traps to avoid
- Plates move over the partly molten asthenosphere, not a ‘molten mantle’.
- Plate tectonics: McKenzie–Parker, Morgan, Le Pichon (1967–68), not Morgan alone.
- Indo-Australian may be split into Indian and Australian plates.
- Baratang is India's best-known mud volcano; Barren Island is the active volcano.
- Alluvial fans form at the foot of hills, not in the lower course.
- The Khyber Pass is not in the Himalaya; the Silk Routes crossed Central Asian deserts, not the Thar.
- Barchan horns point downwind; parabolic arms point upwind.
- Sand bar with a free end = spit.
- Chamoli 2021 was a rock-and-ice avalanche, not a lake outburst.
- UPSC 2024 rain–weathering key is debatable (CO₂ and O₂ both act).
How to strategise
Prelims — what UPSC asks
- From this chapter: causes of earthquakes (1981), the 1991 Garhwal earthquake (1992), meanders as the mark of maturity (1990), the barchan (1991), contour bunding (1982, 2013) and rain and chemical weathering (2024). Learn each landform with its agent, process and one example; pair erosional and depositional forms.
- Numbers change or vary by source (crust thickness, layer depths, earthquake tolls, seismic zones): quote the book's figure, then the standard value with its source and year.
Mains — where it appears and how to answer
- GS1: Himalayan landslides — causes and mitigation (2016); how fjords form and why they are scenic (2023); wind processes in desertification and land degradation (2026). Use the chapter's processes, a labelled sketch and Indian examples with years; give NDMA and the 2005 Act as bare facts.
- On contested points — what drives plates, Chamoli 2021, early earthquake theories — present positions with their authors; avoid assigning blame for disasters.
Self-check
Tap an option. NCERT's own exercise questions come first; the rest test the figures and common confusions.
1. The lithosphere consists of:
2. At which kind of boundary is crust neither created nor destroyed?
3. The Himalaya was formed mainly by:
4. Which landform is typical of a river's middle course?
5. A crescent-shaped dune with horns pointing downwind is a:
6. Stalagmites are found:
7. A Glacial Lake Outburst Flood happens when:
8. Increasing magnitude by 1 on the moment-magnitude scale releases roughly how much more energy?
UPSC questions from this chapter
Open any question to attempt it in the Question bank — your attempt is saved to your progress.