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← Exploring Society: India and Beyond — all chaptersOceans and Continents
Start here: why this chapter matters
In simple wordsIf you took a photograph of the Earth from far away, most of it would look blue, with brown and green patches and white swirls. The blue is ocean, the patches are continents, and the swirls are clouds carrying ocean water to the land as rain. This chapter is about those three things and how they shape life — including yours.
This is Chapter 2 of Exploring Society: India and Beyond (Class 6, the new 2024 book under NCF-SE 2023), in Theme A, ‘India and the World: Land and the People’. Chapter 1 (fees101) taught how to locate places with maps, the globe, latitude and longitude; this chapter uses those tools to look at the big divisions of the Earth’s surface — oceans and continents — and asks two ‘Big Questions’: what they are, with their names and distribution, and how they affect life on Earth, including human life. Chapter 3 (Landforms and Life) follows. It is a short chapter — about eleven pages of reading — so this page has six concept sections, not more. The book’s maps are turned into tables; no continent outline or globe is drawn here.
Reading the chapter opener — the Jules Verne quotation, Fig. 2.1 and The Big Questions (page 27)
- Quotation: Jules Verne (1870) calls the ocean ‘everything’, covering seven-tenths of the globe, a vast reservoir of Nature where life stirs all around. (Beyond NCERT: from his novel Twenty Thousand Leagues Under the Seas.) The book says such quotations are meant to inspire, not to be examined.
- Fig. 2.1: a colour photograph of the whole Earth taken by the Lunar Reconnaissance Orbiter — deep blue ocean with white cloud swirls, brownish land at the edges, a white cap at the bottom; the caption says it is centred on the Indian Ocean, with Africa to the left, India and part of Asia at the top, Australia to the right and Antarctica at the bottom.
- The Big Questions and a QR code to NCERT’s e-content.
- Links in this book: fees101 (globe, hemispheres, latitude and longitude — needed for Fig. 2.2’s ‘circular lines’ and ‘radiating lines’).
- Deeper pages: gess205 (Class 7: water, the water cycle, ocean movements); gess203 (earthquakes, the sea’s work); iest201 (the new Class 7 book: oceans and life); kegy212 (Class 11: water in the oceans); kegy204 (continental drift); kegy106 (natural hazards and disasters); hess402 (water resources and scarcity). This page links them and does not re-teach them.
- UPSC: Prelims asked the order of continents by share of the Earth’s land (2005), what Dakshin Gangotri was (1988) and whether oceans make about half the world’s oxygen (2025). The 2004 tsunami (GS3 2017) and freshwater scarcity (GS1 2015, 2023) are taught more fully in the deeper pages.
| Word | What it means here |
|---|---|
| Ocean | One of the largest water bodies on the globe |
| Sea, bay, gulf | Smaller extensions of the oceans (the book’s Glossary defines them) |
| Landmass | A large body of land |
| Continent | A large continuous expanse of land |
| Island | A smaller piece of land surrounded by water on all sides (continents are too large to be called islands) |
| Hemisphere | Half of the Earth — Northern or Southern, divided by the equator (fees101) |
| Freshwater; groundwater | Water that is not salty; freshwater stored underground |
| Marine | Related to or found in the oceans and seas (side box) |
| Flora; fauna | The plant life; the animal life of a particular region or period (side boxes) |
| Algae | Tiny plants of the oceans (as the book describes them) |
| Cyclone | A violent storm from the ocean with extreme rain or very strong winds |
| Tsunami | A huge, powerful wave usually caused by a strong earthquake or volcanic eruption under the ocean |
| Disaster management | Handling events that cause loss of life and property |
| Eurasia | Europe and Asia taken as one continent |
| Overfishing | Excessive fishing |
At a glance — the six ideas to carry away
- Blue planet: water ≈ almost three-fourths of the surface, land a little over one-fourth; ocean = largest water body; continent = large continuous expanse of land; Northern Hemisphere has more land.
- Water: oceans hold most of it, but it is salty; freshwater is a very small share — glaciers, rivers, lakes, atmosphere, groundwater.
- Five oceans by size: Pacific > Atlantic > Indian > Southern > Arctic; boundaries are conventions. Indian Ocean: Asia (N), Africa (W), Australia (E), Southern Ocean (S); Arabian Sea (W) and Bay of Bengal (E) of India.
- Disasters: cyclones; tsunami — a huge wave from an undersea earthquake or eruption; 26 Dec 2004, India + 13 countries, >2 lakh deaths; Indian Ocean Tsunami Warning System; NDMA.
- Continents: 4, 5, 6 or 7 by grouping (Eurasia, America, Africa-Eurasia); seven usual — Asia > Africa > N. America > S. America > Antarctica > Europe > Australia; Olympic rings = five inhabited continents.
- Islands and life: Greenland largest island; India >1,300 islands; Antarctic programme 1981, Dakshin Gangotri 1983; oceans give >half the oxygen, rain, food, trade, culture; World Oceans Day 8 June; plastic and overfishing.
1. The blue planet: how water and land are shared
In simple wordsCut a round chapati into four equal pieces. Colour three of them blue and one brown. That is roughly the Earth’s surface: three parts water, one part land. Now notice that the brown piece is not spread evenly — most of it sits on the northern half.
Rotate a globe, or look at the Earth from the Moon: the most widespread colour is blue — water. Almost three-fourths of the Earth’s surface is covered by water, which is why early astronauts lovingly called it the ‘blue planet’. The largest water bodies are oceans. The other colour, brown, is land, covering a little over one-fourth of the globe; a large body of land is a landmass, and a large continuous expanse of land is a continent. Both oceans and continents shape the Earth’s climate and so all plant, animal and human life — in our history, culture and daily lives. Oceans and continents are not shared equally between the hemispheres: the polar maps of Fig. 2.2 show that the Southern Hemisphere holds more water and the Northern Hemisphere more land. The oceans hold most of the planet’s water, but it is salty and unfit for most land animals, including humans; freshwater is a very small share, found in glaciers, rivers, lakes, the atmosphere and underground (groundwater).
Reading the ‘Don’t miss out’ on the Indian Navy’s emblem (page 28)The box shows the Navy’s crest — the national emblem above a golden anchor on a dark blue shield, with a Devanagari motto scroll below — and explains the motto Sham no Varunah, ‘Be auspicious to us, O Varuna’, an invocation to Varuṇa, a Vedic deity of the oceans, the sky and water in general. The point: the sea has long had a place in India’s culture and imagination, and still does in a modern institution. (Beyond NCERT: the phrase comes from a peace invocation in the Taittiriya Upanishad.)
Reading Fig. 2.2 (the two polar maps) and its ‘Let’s explore’ box (page 29) — as a tableTwo round maps of the Earth, one seen from above the North Pole, one from above the South Pole, in blue (water) and pale yellow (land), with circles and radiating lines. They are not redrawn; what they show is listed below. The ‘Let’s explore’ box asks: what are the circular and radiating lines called; which hemisphere holds more water; what the water-to-land proportion might be in each; and whether the oceans are connected. A side note says sea, bay and gulf are defined in the Glossary. The point: looking from the poles makes the unequal hemispheres obvious. Answers are in the in-text section.
| Fig. 2.2 | What it shows |
|---|---|
| Left: seen from above the North Pole | the pole at the centre with lines radiating from it; much of the disc is land — the northern continents crowd around a small central ocean |
| Right: seen from above the South Pole | Antarctica at the centre, surrounded by a wide ring of ocean; only the southern tips of other continents reach the edge |
| On both | circular lines (parallels of latitude) and lines radiating from the pole (meridians of longitude); blue = oceans and their extensions (seas, bays, gulfs) |
Reading the ‘Think about it’ box on water (page 31)It asks why, if there is so much water, people talk of a ‘water scarcity’ or ‘water crisis’, and what ways of saving water you have seen at home, school and in your town or village. The point: abundance of water is not abundance of usable freshwater — the theme of hess402 and gess205. Outline in the in-text section.
Beyond NCERT — water and land in numbers
- Standard references put the ocean share of the surface at about 71% — so ‘almost three-fourths’ (75%) and Verne’s ‘seven-tenths’ (70%) are both round approximations.
- Freshwater is usually given as about 2.5–3% of all water, most of it locked in ice (UPSC 1987, 2010, 2013 — taught in gess205, kegy212 and hess402).
Blue planet: exam lines
- Water ≈ three-fourths; land ≈ one-fourth (a little over).
- Continent = large continuous expanse of land; landmass = any large body of land.
- Northern Hemisphere: more land; Southern: more water.
- Most water is salty; freshwater is a very small share — glaciers, rivers, lakes, atmosphere, groundwater.
2. The five oceans — and one connected sea
In simple wordsThink of a big house with one open hall. People put up curtains and call the parts ‘living room’, ‘dining room’ and ‘study’ — useful names, but the air and the people move freely between them. The five oceans are like that: named parts of one connected body of water.
The world map (Fig. 2.3) shows five oceans — the Pacific, Atlantic, Indian, Arctic and Southern (or Antarctic) Oceans. They are not really separate: the dividing lines are conventions, and the natural world does not follow them. Seawater constantly flows across the oceans, sustaining a rich diversity of marine life, and many species are found in several oceans. Marine flora includes tiny plants called algae and all kinds of seaweeds; marine fauna includes thousands of species of colourful fish, dolphins, whales and countless deep-sea creatures. Each part of the ocean, from the sunlit surface to the dark depths, has its own life. By size, the Pacific is the largest, followed by the Atlantic, the Indian (third), the Southern (fourth), and the Arctic, the smallest. The Indian Ocean is bounded by Asia to the north, Africa to the west, Australia to the east and the Southern Ocean to the south; on either side of India lie two of its parts — the Arabian Sea to the west and the Bay of Bengal to the east.
Reading Fig. 2.3, the world map of oceans and continents, and its ‘Let’s explore’ table (page 32) — as tablesAn oval world map, ‘not to scale’, in shades of blue and yellow, labels each ocean and continent, draws the oceans’ conventional boundaries as solid lines and the equator as a dashed line. It is not redrawn; its labels are in the first table. The ‘Let’s explore’ asks you to mark which hemisphere(s) each ocean belongs to — answered in the second table, read from the map’s equator. The point: three oceans cross the equator; only the Southern and Arctic lie wholly in one hemisphere.
| Ocean (Fig. 2.3) | Beside it on the map | Size rank (p. 32) |
|---|---|---|
| Pacific Ocean | between Asia and Australia on one side and North and South America on the other; shown at both edges of the map | 1 (largest) |
| Atlantic Ocean | between the Americas and Europe and Africa | 2 |
| Indian Ocean | Asia to the north, Africa to the west, Australia to the east, the Southern Ocean to the south (p. 33) | 3 |
| Southern Ocean | around Antarctica; its northern limit drawn as a line | 4 |
| Arctic Ocean | at the top, between North America, Europe and Asia | 5 (smallest) |
| Ocean | Northern Hemisphere | Southern Hemisphere |
|---|---|---|
| Pacific | ✓ | ✓ |
| Atlantic | ✓ | ✓ |
| Indian | ✓ | ✓ |
| Southern | — | ✓ |
| Arctic | ✓ | — |
Reading the ‘Ocean Life’ photo page (page 30)A full page of nine colour photographs: a coral reef; a red starfish on a sea anemone; a shark over a sandy floor; a sperm whale mother and baby; two dolphins leaping from a wave; a shallow coral reef full of colourful tropical fish; green algae; two emperor penguins on ice; and a Bonaire sea turtle. The point: the oceans hold life from tiny algae to the largest animals, from tropical reefs to polar ice — the ‘rich diversity of marine life’ of the text.
Reading the side boxes ‘Marine’, ‘Flora’ and ‘Fauna’ (page 31)Three definitions: marine — related to or found in the oceans and seas; flora — the plant life of a particular region or period; fauna — its animal life. The point: three words you need for any answer on ocean life.
Reading the ‘Don’t miss out’ on the Indian Ocean and Fig. 2.4 (page 33) — as a tableThe box gives the Indian Ocean’s limits (Asia, Africa, Australia, the Southern Ocean) and names the Arabian Sea and Bay of Bengal. Fig. 2.4 repeats the map of India from Chapter 1 (Fig. 1.6), adding the two seas and India’s two island groups; it is ‘not to scale’ and is not redrawn here. The point: India is a peninsula facing an ocean on three sides — its seas and islands are listed below.
| Water body (Fig. 2.4) | Position | Indian island group in it |
|---|---|---|
| Arabian Sea | to the west of India | Lakshadweep (India) |
| Bay of Bengal | to the east of India | Andaman and Nicobar Islands (India) |
| Indian Ocean | to the south | — |
Conventions, not a verdict: how many oceans?The book says the five oceans are conventions. Bodies that set names for the world’s waters have counted them differently. All entries except NCERT’s are Beyond NCERT; none is presented as the only correct count.
| Count | Who uses it | Reasoning |
|---|---|---|
| Five | NCERT (this chapter) | Pacific, Atlantic, Indian, Southern, Arctic — with the boundaries ‘no more than conventions’ |
| Four | Many older atlases and textbooks | no separate Southern Ocean; the waters around Antarctica are treated as the southern parts of the Pacific, Atlantic and Indian Oceans |
| Five, with a Southern Ocean | International Hydrographic Organization draft (2000); National Geographic (2021) | the waters around Antarctica form a distinct ocean, defined by a current that circles the continent |
| One World Ocean | Oceanographers’ usage | all the oceans are one connected body of water — the book’s own point about seawater flowing across them |
Oceans: exam lines
- Size order: Pacific > Atlantic > Indian > Southern > Arctic — Arctic smallest; Indian is third.
- Boundaries between oceans are conventions; the oceans are interconnected.
- Indian Ocean: Asia N, Africa W, Australia E, Southern Ocean S; Arabian Sea west and Bay of Bengal east of India.
- Lakshadweep — Arabian Sea; Andaman and Nicobar — Bay of Bengal. Don’t swap them.
- Southern Ocean = also called the Antarctic Ocean.
3. Oceans and disasters: cyclones and tsunamis
In simple wordsThe ocean is like a giant kettle and a giant bathtub at once. Its warm water rises as steam that falls on the land as the rain farmers wait for — but the same heat can whip up violent storms. And if the floor of the bathtub suddenly jerks, the water sloshes into a wave that can rush far up the shore.
The white shapes in Fig. 2.1 are clouds. They bring rain to the continents — the monsoon rains India expects every summer originate in the ocean, and without them agriculture and all life would suffer. But oceans also give rise to storms — violent events with extreme rainfall or very strong winds, such as cyclones, which can cause widespread damage to coastal regions. A tsunami is another natural disaster from the ocean: a huge and powerful wave, generally caused by a strong earthquake or a volcanic eruption at the bottom of the ocean. Tsunamis can travel thousands of kilometres and submerge coastal areas. On 26 December 2004, India and 13 other countries around the Indian Ocean were struck by a powerful tsunami caused by an earthquake in Indonesia; more than two lakh people lost their lives. In India the Andaman and Nicobar Islands and the coasts of Tamil Nadu and Kerala were severely affected. Such tsunamis are rare but very destructive; they can often be detected before they hit a coast, and many countries collaborate in early warning systems — in particular the Indian Ocean Tsunami Warning System, to which India contributes. Events that cause loss of life and property are handled under disaster management; India has its own National Disaster Management Authority (NDMA).
⤵ From ocean to monsoon rain (NCERT pages 33, 37–38)
Oceanholds most of the Earth’s water
Cloudslarge masses of cloud form over the oceans (the white swirls of Fig. 2.1)
Monsoon rainclouds bring rain to the continents every summer
Life on landagriculture and all life depend on it — part of the water cycle (Science)
⤵ A tsunami and the response to it (NCERT pages 33–34)
Shock under the seaa strong earthquake or volcanic eruption on the ocean floor
Huge wavetravels thousands of kilometres across the ocean
Coast struckcoastal areas submerged; 2004: Andaman and Nicobar, Tamil Nadu, Kerala
Early warningdetected before it hits; Indian Ocean Tsunami Warning System
Disaster managementIndia’s National Disaster Management Authority
Reading the ‘Don’t miss out’ on the 2004 tsunami (page 34)Three points: the 26 December 2004 tsunami from an earthquake in Indonesia struck India and 13 other countries, killing more than two lakh people, with severe damage in the Andaman and Nicobar Islands, Tamil Nadu and Kerala; tsunamis are rare but can often be detected early through shared early warning systems, including the Indian Ocean Tsunami Warning System; and India’s National Disaster Management Authority deals with all kinds of disasters (more in Chapter 3). The point: oceans connect countries in danger as well as trade — and cooperation and preparedness save lives.
Beyond NCERT — the 2004 tsunami and India’s response
- The earthquake struck off northern Sumatra, with a magnitude usually given as about 9.1.
- The Indian Ocean Tsunami Warning System was set up under UNESCO’s Intergovernmental Oceanographic Commission after 2004; India’s tsunami warning centre is run by INCOIS, Hyderabad.
- The NDMA was set up under the Disaster Management Act, 2005; it is chaired by the Prime Minister.
- Mangroves reduced damage on some coasts in 2004 (UPSC 2011; kegy206).
Disasters: exam lines
- Monsoon rains originate in the ocean.
- Cyclones = ocean storms with extreme rain or very strong winds.
- Tsunami cause: undersea earthquake or volcanic eruption — not wind.
- 2004: 26 December; earthquake in Indonesia; India + 13 = 14 countries; >2 lakh deaths; India — Andaman and Nicobar, Tamil Nadu, Kerala.
- Warning: Indian Ocean Tsunami Warning System; management: NDMA.
4. Continents: how many, and how big?
In simple wordsHow many ‘rooms’ does a flat have if the kitchen opens into the dining area? Some say one, some say two. Counting continents is like that: the land is what it is, but where you draw the line between ‘one’ and ‘two’ is a choice people make — for reasons of geography, history or habit.
How many continents can you count on Fig. 2.3? The answer is not simple: depending on our choice, anything from four to seven. North and South America are generally two continents, but as one landmass they can be one. Europe and Asia are generally two, though the map shows they form a single landmass; for historical and cultural reasons Europe’s evolution differed from Asia’s, but geologists often treat them as one continent, Eurasia. Africa and Eurasia are generally two, but sometimes one. The book’s table gives four counts; the list of seven — Africa, Antarctica, Asia, Australia, Europe, North America, South America — is the one most widely adopted. A diagram of coloured squares (not their shapes, only their relative sizes) shows that Asia is the largest and Australia the smallest.
| Count (p. 35) | Continents (alphabetical, as in the book) |
|---|---|
| 4 | Africa-Eurasia, America, Antarctica, Australia |
| 5 | Africa, America, Antarctica, Australia, Eurasia |
| 6 | Africa, Antarctica, Australia, Eurasia, North America, South America |
| 7 | Africa, Antarctica, Asia, Australia, Europe, North America, South America |
Reading the squares diagram and its ‘Let’s explore’ box (page 36)A blue panel with seven blocks of coloured squares, roughly placed as on a world map but deliberately not shaped like the continents: pink for North America and Asia, green for Europe and South America, yellow for Africa and Australia, teal for a long single row for Antarctica. Counting the squares in the PDF gives Asia 51, Africa 30, North America 21, South America 18, Antarctica 13, Europe 11, Australia 8 (152 in all). The box asks you to name the largest and smallest; compare North and South America, Africa and North America, Antarctica and Australia; recolour Europe and Asia as ‘Eurasia’ and compare it with South America; and list the continents from smallest to largest. The point: relative size can be shown without drawing shapes — and Asia and Europe together dwarf every other continent. Answers in the in-text section.
Reading the ‘Don’t miss out’ on the Olympic rings (page 35)The five interlocked Olympic rings, a symbol of the Games, stand for sportspeople gathering from all over the world; they were chosen to represent five inhabited continents — Africa, America, Asia, Australia and Europe. The point: a five-continent count in everyday use — with ‘America’ as one and Antarctica (uninhabited) left out.
Conventions, not a verdict: how many continents?The book itself sets the counts side by side. Who uses which count, and why, is listed here. All entries except NCERT’s are Beyond NCERT; none is endorsed, and the book’s own most common count is seven.
| Count | Who uses it | Reasoning |
|---|---|---|
| Seven | NCERT (most widely adopted); most English-language schools | Europe and Asia, and North and South America, are kept separate for historical, cultural and geographical reasons |
| Six (Eurasia) | Geologists often (NCERT); some school systems | Europe and Asia are one continuous landmass with no sea between them |
| Six (one America) | Schools in many Spanish- and Portuguese-speaking countries | the Americas are taught as one continent; Europe and Asia kept apart |
| Five | The Olympic rings (NCERT); NCERT’s five-count lists Eurasia and America | inhabited continents only, or the largest groupings |
| Four | NCERT’s table (Africa-Eurasia) | Africa and Eurasia joined by land as one ‘Afro-Eurasia’ |
Beyond NCERT — sizes
- Standard area rankings follow the same order as the book’s squares: Asia, Africa, North America, South America, Antarctica, Europe, Australia (often listed as Australia/Oceania).
- UPSC 2005 asked this order for four of them: Africa – North America – South America – Europe.
Continents: exam lines
- Counts run from 4 to 7; 7 is the most widely used.
- Eurasia = Europe + Asia (geologists often count it as one).
- Largest → smallest: Asia, Africa, North America, South America, Antarctica, Europe, Australia.
- North America > South America; Africa > North America; Antarctica > Australia; South America > Europe (UPSC 2005).
- Olympic rings = five inhabited continents: Africa, America, Asia, Australia, Europe — Antarctica is not among them.
5. Islands — and India in the oceans and Antarctica
In simple wordsPour water on a lumpy floor: the big dry patches are ‘continents’, the little dry spots left everywhere are ‘islands’. Some islands are tiny rocks; one is so big you would have to add up ten of India’s largest states to match it. India has hundreds of its own — and its scientists even live and work on the frozen continent at the bottom of the globe.
The continents do not include all land. Smaller pieces of land surrounded by water on all sides are islands; continents are also surrounded by water, but are too large to be called islands. There are lakhs of islands, of very different sizes. Greenland is the largest island in the world — you would have to add the areas of India’s 10 largest states to reach its size. India has more than 1,300 small islands, including two major groups — the Andaman and Nicobar Islands in the Bay of Bengal and the Lakshadweep Islands in the Arabian Sea. Since 1981, the Indian Antarctica Programme has explored Antarctica, a continent with a very cold climate and harsh environment (the white expanse at the bottom of Fig. 2.1, mostly ice). In 1983 India set up its first scientific base station there, Dakshin Gangotri; two more bases were set up later. About 40 teams of Indian scientists have researched there, especially on the evolution of climate and environment; the settlement has a library and even a post office.
Reading the ‘Don’t miss out’ on islands and Antarctica (page 37)Three points: Greenland is the largest island (as big as India’s 10 largest states together); India has more than 1,300 islands, with two major groups; and the Indian Antarctica Programme (since 1981), with Dakshin Gangotri (1983) and two later bases, about 40 research teams, and a library and post office. The point: India is not only a land country — it has an island territory and a scientific presence on the southernmost continent.
| India’s 10 largest states (Beyond NCERT) | Area, km² |
|---|---|
| Rajasthan | 342,239 |
| Madhya Pradesh | 308,252 |
| Maharashtra | 307,713 |
| Uttar Pradesh | 240,928 |
| Gujarat | 196,024 |
| Karnataka | 191,791 |
| Andhra Pradesh | 162,968 |
| Odisha | 155,707 |
| Chhattisgarh | 135,191 |
| Tamil Nadu | 130,058 |
| Total | 2,170,871 |
| Greenland (Beyond NCERT) | about 2,166,086 |
Beyond NCERT — islands and Antarctic bases
- The table checks the book’s comparison: the ten largest states add up to about 21.7 lakh km², within 1% of Greenland’s area (states only; Union Territories such as Ladakh are left out).
- India’s two later Antarctic stations are Maitri (1989) and Bharati (2012). Dakshin Gangotri was later buried by ice and used as a supply base.
- Port Blair is the capital of the Andaman and Nicobar Islands; Kavaratti of Lakshadweep (UPSC 2008 asked about a desalination plant at Kavaratti — legy204).
Islands and Antarctica: exam lines
- Greenland = largest island (Australia is counted as a continent, not an island).
- India: more than 1,300 islands; Andaman and Nicobar (Bay of Bengal), Lakshadweep (Arabian Sea).
- Antarctic programme 1981; Dakshin Gangotri 1983 — India’s first Antarctic base; two more later.
- UPSC 1988 called Dakshin Gangotri an ‘unmanned station … for continuous weather and scientific recordings’. The book calls it a scientific base station; (b) is the only sensible option and the stored key, but ‘unmanned’ is the question’s wording — disputed wording, not a wrong key.
6. Oceans and life — and our duty to them
In simple wordsEvery second breath you take carries oxygen made in the sea; the rain on your village came from it; the fish on many plates, the ships that bring goods, the stories of sea gods your grandparents tell — all come from the ocean. And every plastic bag that ends up in a drain may end up there too.
Oceans and continents are vital parts of the environment. Oceans send rain to the continents as part of the water cycle (studied in Science) — without oceans, says the book, there would be no rainfall and the Earth would be a desert. More than half of the world’s oxygen is produced by the oceans’ flora, which is why they are called ‘the planet’s lungs’. Oceans therefore help regulate the climate and sustain life. From early times people have used the seas to migrate, to trade, to conduct military campaigns, and for food through fishing; oceans have nourished the cultures of coastal peoples, almost all of whom have tales of the sea, sea gods and goddesses, sea monsters and treasures. But scientific studies show the oceans are polluted by human activity: we throw several million tonnes of plastic into them every year, choking marine life; there are other forms of pollution; and overfishing also reduces marine life. Protecting the oceans is a collective responsibility.
⤵ How plastic harms the ocean — and what can break the chain (NCERT page 38)
Waste on landplastic and other waste from human activity
Into the seaseveral million tonnes of plastic each year
Marine life chokedwith other pollution and overfishing, marine life declines
Collective protectionreduce, reuse, recycle; fish responsibly; keep coasts clean
Reading the ‘Don’t miss out’ on World Oceans Day (page 38)The United Nations has made 8 June World Oceans Day, to remind everyone of the ocean’s role in daily life — the lungs of our planet, a major source of food and medicine, and a critical part of the biosphere. The box adds the threats — plastic, other pollution, overfishing — and ends with our collective responsibility. The point: the ocean is a shared resource that only shared action can protect.
Reading ‘Before we move on …’ (pages 38–39)Three summary points: oceans (vast water bodies) and continents (large landmasses) cover the Earth’s surface, the oceans are interconnected, and continents can be counted in various ways — most commonly seven; the Northern Hemisphere has more land than the Southern; and oceans support marine life and the world’s climate but are now seriously affected by human activity and need collective protection. The point: the chapter’s three take-aways in one place — learn them as stated.
Beyond NCERT — ocean oxygen and Oceans Day
- Most ocean oxygen comes from phytoplankton — tiny drifting algae and photosynthetic bacteria (such as cyanobacteria); scientists usually estimate about 50% of the Earth’s oxygen (UPSC 2025). Strictly, bacteria are not ‘flora’, so ‘ocean phytoplankton’ is the safe term.
- The UN General Assembly recognised World Oceans Day in 2008; it has been observed since 2009.
Oceans and life: exam lines and NCERT simplifications
- Oceans make more than half of the world’s oxygen — ‘the planet’s lungs’. Not the rainforests (UPSC 2025: ‘rainforests produce more oxygen than oceans’ is false).
- ‘Without oceans there would be no rainfall’ is the book’s simplification — some rain comes from water evaporated over land and lakes, but most moisture comes from the oceans. Safe line: ‘oceans are the main source of rain’.
- World Oceans Day: 8 June (UN).
- Threats named: plastic (several million tonnes a year), other pollution, overfishing.
‘Let’s explore’ and ‘Think about it’ — short answers
The chapter’s activity boxes, in page order.
Page 29: What are the circular lines in each map called? And the lines radiating out of the two poles?
The circles are parallels of latitude (seen from a pole they appear as rings around it); the radiating lines are meridians of longitude, which all meet at the poles (fees101).
Page 29: Which hemisphere holds more water?
The Southern Hemisphere — seen from the South Pole, Antarctica sits in a wide ring of ocean; seen from the North Pole, land crowds around a small ocean. So the Northern Hemisphere has more land.
Page 29: What could be the approximate proportion of water to land in the Northern Hemisphere? And in the Southern Hemisphere?
A discussion — the book gives no figures. Estimate from Fig. 2.2: the Northern disc has much more land (perhaps a little under half is land), the Southern disc is mostly water. (Beyond NCERT: standard estimates are roughly 60% water and 40% land in the north, and about 80% water and 20% land in the south.)
Page 29: Are all the oceans connected with one another, or are there separations between them?
They are all connected; the boundaries drawn between them are conventions, and seawater and marine life move across them (p. 31).
Page 31 (Think about it): If there is such abundance of water on the planet, why is there so much talk of ‘water scarcity’ or a ‘water crisis’?
Most water is salty seawater, unfit for drinking or farming; freshwater is a very small share, and much of it is locked in glaciers or underground; rain is uneven across places and seasons; growing population, farming and industry use more; and pollution and over-pumping of groundwater spoil or exhaust supplies (hess402, gess205).
Page 31 (Think about it): What ways of saving water are you aware of? Which ones have you seen practised at home, school, and in your village, town or city?
Closing taps, fixing leaks, using a bucket instead of a running hose, reusing washing water for plants, rainwater harvesting on roofs, recharge pits, drip irrigation, keeping ponds and wells clean, and community rules for tanks. Note which you have seen and who organises them.
Page 32: Locate the five oceans and mark the hemisphere or hemispheres they belong to.
Pacific, Atlantic, Indian — both Northern and Southern; Southern Ocean — Southern only; Arctic Ocean — Northern only (table in section 2).
Page 36: Counting the squares, name the largest continent and the smallest.
Asia is the largest (51 squares); Australia the smallest (8).
Page 36: Which is larger — North America or South America? Africa or North America? Antarctica or Australia?
North America (21 v 18); Africa (30 v 21); Antarctica (13 v 8).
Page 36: Re-colour Europe and Asia as ‘Eurasia’. Compare its size with South America’s.
Eurasia = 51 + 11 = 62 squares against South America’s 18 — more than three times as large.
Page 36: Write the list of continents from the smallest to the largest.
Australia (8), Europe (11), Antarctica (13), South America (18), North America (21), Africa (30), Asia (51).
Questions, activities and projects (pages 39–40) — answer outlines
1. Explain the following terms: (a) Continent (b) Ocean (c) Island.
(a) Continent: a large continuous expanse of land — usually seven are counted (Asia, Africa, North America, South America, Antarctica, Europe, Australia), though counts vary from four to seven. (b) Ocean: one of the largest water bodies on the Earth — five are named (Pacific, Atlantic, Indian, Southern, Arctic), all interconnected. (c) Island: a smaller piece of land surrounded by water on all sides, e.g. Greenland (the largest), or India’s Andaman and Nicobar and Lakshadweep groups.
2. Let us draw — Without looking at the maps in this chapter, draw the continents free hand on a sheet of paper and colour them. Then compare your drawing with the map of oceans and continents in the chapter.
An activity (we do not draw maps here). Tips: place them by position first — the Americas on one side; Europe, Africa and Asia in the middle; Australia to the lower right of Asia; Antarctica along the bottom — then check sizes against the squares (Asia biggest, Australia smallest) and compare with Fig. 2.3.
3. Let us do — On the outline map of the world given below, label all the continents and oceans.
An activity on the book’s outline map (page 39; not reproduced). Use the Fig. 2.3 table in section 2: label the seven continents and the five oceans — the Pacific at both ends of the map, the Atlantic between the Americas and Europe–Africa, the Indian Ocean south of Asia, the Arctic at the top and the Southern Ocean around Antarctica at the bottom.
4. Solve this crossword.
Across: 1 OXYGEN, 3 CONTINENT, 6 EURASIA, 8 PLASTIC, 10 ANTARCTICA. Down: 2 GREENLAND, 4 TSUNAMI, 5 AUSTRALIA, 7 PACIFIC, 9 ISLAND. (Every answer fits its cell count and every crossing letter in the grid.)
Reading the outline map (page 39) and the crossword (page 40)The outline map is an oval world map with blank white continents on a blue ocean and dashed lines for the equator and tropics — for you to label; it is not redrawn here. The crossword is a green grid of ten words, five across and five down, with clues on oxygen, continents, Eurasia, plastic, Antarctica, Greenland, tsunami, Australia, the Pacific and islands. The point: the chapter’s ten key ideas, practised two ways.
What to remember
Numbers
Water on the Earth’s surfacealmost three-fourths (Verne: seven-tenths)
Landa little over one-fourth
Oceans5 — Pacific, Atlantic, Indian, Southern, Arctic (largest to smallest)
Continents4 to 7 by count; 7 most common
Squares in the book’s size diagramAsia 51, Africa 30, N. America 21, S. America 18, Antarctica 13, Europe 11, Australia 8
Eurasia in squares62
Olympic rings5 (inhabited continents)
Indian Ocean tsunami26 December 2004
Countries struck in 2004India + 13 = 14
Lives lost in 2004more than two lakh
India’s islandsmore than 1,300
Greenland’s size≈ India’s 10 largest states together
Indian Antarctic Programmesince 1981
Dakshin Gangotri1983 (first base; two more later)
Indian research teams in Antarcticaabout 40
Oxygen from the oceansmore than half
World Oceans Day8 June
One-liners
- Early astronauts called the Earth the ‘blue planet’.
- A continent is a large continuous expanse of land.
- The Northern Hemisphere has more land than the Southern.
- Freshwater is found in glaciers, rivers, lakes, the atmosphere and underground.
- The lines dividing the oceans are conventions.
- Algae and seaweeds are marine flora.
- The Arabian Sea lies west of India, the Bay of Bengal east.
- Monsoon rains originate in the ocean.
- A tsunami is generally caused by a strong undersea earthquake or volcanic eruption.
- India contributes to the Indian Ocean Tsunami Warning System.
- India’s National Disaster Management Authority deals with all kinds of disasters.
- Geologists often treat Europe and Asia as one continent, Eurasia.
- Greenland is the largest island in the world.
- Lakshadweep is in the Arabian Sea; Andaman and Nicobar in the Bay of Bengal.
- The oceans are called ‘the planet’s lungs’.
- The Indian Navy’s motto invokes Varuna, a Vedic deity of the oceans.
Traps to avoid
- Ocean sizes: Pacific > Atlantic > Indian > Southern > Arctic — the Indian Ocean is third, not second.
- Only the Southern (south) and Arctic (north) lie in one hemisphere; the other three cross the equator.
- Northern Hemisphere = more land; Southern = more water.
- Continent sizes: Africa > North America > South America > Europe (UPSC 2005).
- Antarctica is larger than Australia — and larger than Europe.
- Olympic rings: five inhabited continents — America counted as one, Antarctica left out.
- Greenland, not Australia, is the largest island; Australia counts as a continent.
- Lakshadweep — Arabian Sea; Andaman and Nicobar — Bay of Bengal.
- Tsunami: earthquake or undersea eruption, not a storm; cyclones are the storms.
- 2004 tsunami: earthquake in Indonesia; 14 countries in all (India + 13).
- Dakshin Gangotri (1983) was India’s first Antarctic base; the programme began in 1981.
- More than half of the world’s oxygen comes from the oceans, not the rainforests.
How to strategise
Prelims — what UPSC asks
- From this chapter: the order of continents by area (2005 — Africa, North America, South America, Europe; learn the full order from the squares diagram); Dakshin Gangotri (1988 — India’s first Antarctic station; the question’s ‘unmanned’ is its own wording); ocean oxygen (2025 — marine phytoplankton and bacteria make about half the world’s oxygen; rainforests do not out-produce the oceans).
- Elsewhere: freshwater shares (1987, 2010, 2013) on gess205, kegy212 and hess402 (cap reached); mangroves and the 2004 tsunami (2011) on kegy206; continental drift and Gondwana (1995, 2008, 2014, 2025) on kegy204; Antarctica’s high mean elevation (1995) and the ‘mirror-image’ continents (1986) go beyond this chapter.
- Method: learn three ordered lists (oceans by size, continents by size, the four counts), the hemisphere facts, the two Indian island groups and their seas, and the dates 1981, 1983, 26 December 2004 and 8 June.
Mains — where it appears and how to answer
- This chapter gives the base for GS1 and GS3 answers taught in the deeper pages: the 2004 tsunami and NDMA guidelines (GS3 2017; tsunamis GS1 2025) — kegy203, kegy106, iest201; freshwater scarcity (GS1 2015, 2023) — hess402, legy204. Use the book’s points as an introduction: three-fourths water but little freshwater; 14 countries struck in 2004; early warning and the NDMA.
Self-check
Tap an option. NCERT's own exercise questions come first; the rest test the figures and common confusions.
1. According to NCERT, which ocean is the third largest?
2. Which ocean lies wholly in the Northern Hemisphere?
3. Arrange in decreasing order of area: Europe, Africa, South America, North America.
4. Geologists often treat which two continents as one?
5. Lakshadweep lies in the:
6. A tsunami is generally caused by:
7. India’s first scientific base station in Antarctica, set up in 1983, was:
8. Why are the oceans called ‘the planet’s lungs’?
UPSC questions from this chapter
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