BharatNotes Why this chapter matters for UPSC: The four domains are the vocabulary of physical geography and of environment questions in GS3: continents and oceans, the layers of the atmosphere, the share of fresh water, and how human activity disturbs the balance between them. In the rationalised 2023-24 edition this is still Chapter 5, "Major Domains of the Earth"; the only change is that India's Antarctic stations are now named as Maitri and Bharati (the 2020 print said Maitri and Dakshin Gangotri).
Contemporary hook: The air NCERT describes is changing measurably. Carbon dioxide at Mauna Loa, Hawaii averaged 432.34 parts per million in May 2026, the highest monthly mean in NOAA's record; the 2025 global annual mean was 425.62 ppm (NOAA Global Monitoring Laboratory). NCERT's "1 per cent" for "other gases" hides the one that matters most for climate.
🧠 First Principles — Read This First
NCERT starts from the first chapter: the Earth is the only planet with life, because land, water and air are present together. The surface of the Earth is a complex zone where three components of the environment meet, overlap and interact:
- the lithosphere, the solid portion on which we live;
- the atmosphere, the layers of gas around the Earth (oxygen, nitrogen, carbon dioxide and others);
- the hydrosphere, water in all its forms (ice, water and water vapour).
The biosphere is the narrow zone where land, water and air meet, and which contains all forms of life. The names come from Greek: lithos (stone), atmos (vapour), hudor (water) and bios (life).
The chapter's lesson is balance: the domains act on one another, and cutting forests, polluting water or burning fuel in one domain shows up in the others.
PART 1 — Quick Reference
The Four Domains (NCERT)
| Domain | What it is |
|---|---|
| Lithosphere | The rocks of the Earth's crust and the thin layers of soil with nutrients that sustain organisms; divided into continents and ocean basins |
| Hydrosphere | Water in all forms: oceans, rivers, lakes, ice in glaciers, underground water, water vapour |
| Atmosphere | A thin blanket of air extending up to about 1,600 km; five layers |
| Biosphere | The narrow zone of contact between land, water and air, where life exists |
Highest and Deepest
| Feature | NCERT | Current figure |
|---|---|---|
| Mt Everest | 8,848 m above sea level | 8,848.86 m, announced jointly by China and Nepal on 8 December 2020 (Xinhua) |
| Deepest point | 11,022 m, Mariana Trench (Pacific Ocean) | Challenger Deep, at the southern end of the Mariana Trench, about 10,935 m (NOAA) |
NCERT's point stands either way: the sea is deeper than the highest mountain is high.
Continents and Oceans (NCERT)
- Seven continents: Asia, Europe, Africa, North America, South America, Australia, Antarctica. The greater part of the land lies in the Northern Hemisphere.
- Five oceans, in order of size: Pacific, Atlantic, Indian, Southern, Arctic.
- Water and land: more than 71% of the Earth is covered with water and 29% with land. More than 97% of the Earth's water is in the oceans and too salty for human use; NCERT's figure shows oceans 97.5%, fresh water 2.5%.
PART 2 — Concepts & Narrative
The Lithosphere: Continents
The level of sea water is the same everywhere, so elevation on land is measured from sea level, taken as zero.
- Asia, the largest continent, covers about one-third of the Earth's land. It lies in the Eastern Hemisphere; the Tropic of Cancer passes through it; the Ural mountains separate it from Europe. Europe and Asia together are Eurasia.
- Europe is much smaller, west of Asia; the Arctic Circle passes through it, and it is bounded by water on three sides.
- Africa, the second largest, is the only continent crossed by the Tropic of Cancer, the Equator and the Tropic of Capricorn. It has the Sahara, the world's largest hot desert, and the Nile, which NCERT calls the world's longest river.
- North America, the third largest, lies wholly in the Northern and Western Hemispheres and is linked to South America by the narrow Isthmus of Panama.
- South America lies mostly in the Southern Hemisphere; the Andes, the world's longest mountain range, run its length, and it has the world's largest river, the Amazon.
- Australia, the smallest continent, lies entirely in the Southern Hemisphere and is called an island continent.
- Antarctica, wholly in the Southern Hemisphere, has the South Pole almost at its centre and is permanently covered with thick ice sheets; there are no permanent human settlements, but many countries, including India, have research stations there.
Everest firsts (NCERT). Edmund Hillary (New Zealand) and Tenzing Norgay Sherpa (India) were the first to climb Everest, on 29 May 1953. Junko Tabei (Japan) was the first woman to reach the summit, on 16 May 1975, and Bachendri Pal the first Indian woman, on 23 May 1984.
How the continents got where they are. NCERT Class XI (Fundamentals of Physical Geography) tells the story. In 1912 the German meteorologist Alfred Wegener put forward the continental drift theory: all continents once formed a single mass, Pangaea ("all earth"), surrounded by a mega-ocean, Panthalassa ("all water"). Around 200 million years ago Pangaea began to split, first into Laurasia in the north and Gondwanaland in the south, which later broke into today's continents. The evidence includes the jig-saw fit of the facing coasts of Africa and South America, tillite (glacial rock) of the Gondwana system found in India and five other southern landmasses, gold placers on the Ghana coast whose source veins lie in Brazil, and fossils of the small reptile Mesosaurus found only in South Africa and Brazil, 4,800 km apart.
The Hydrosphere: Oceans
Oceans are the major part of the hydrosphere. They are all interconnected and always moving; the three chief movements are waves, tides and ocean currents.
| Ocean | NCERT's description |
|---|---|
| Pacific | The largest, spread over one-third of the Earth; almost circular; surrounded by Asia, Australia and the Americas; holds the Mariana Trench |
| Atlantic | Second largest; S-shaped; highly indented coastline with natural harbours; the busiest ocean for commerce |
| Indian | The only ocean named after a country, India; almost triangular; bounded by Asia, Africa and Australia |
| Southern | Encircles Antarctica and extends north to 60° S |
| Arctic | Within the Arctic Circle, around the North Pole; joined to the Pacific by the shallow Bering Strait |
Why a blue planet faces water shortage. Most of the remaining water is in ice sheets and glaciers or under the ground, and only a very small share is fresh water available for human use (NCERT).
The Southern Ocean is now officially recognised
The International Hydrographic Organization (IHO) had once listed a Southern Ocean (1937) and then dropped it (1953). At its Third Assembly in 2023, the IHO approved Resolution 02/2023 recognising the Southern Ocean, with its northern limit at the parallel of 60° S; the southern limits of the Atlantic, Indian and Pacific Oceans now meet it there (IHO report to the UN Group of Experts on Geographical Names, 2025). NCERT's five oceans and its 60° S limit agree with this.
Antarctica and the treaty that governs it. The Antarctic Treaty (1959) declares that Antarctica "shall be used for peaceful purposes only" and prohibits "any measures of a military nature", such as bases and fortifications. The ban on mining is in a later instrument: Article 7 of the Protocol on Environmental Protection (Madrid, signed 4 October 1991, in force 1998) prohibits all activities relating to Antarctic mineral resources except scientific research. India acceded to the Treaty on 19 August 1983 and became a consultative party on 12 September 1983 (Antarctic Treaty Secretariat). India's stations, per NCERT's 2023-24 edition, are Maitri and Bharati.
The Atmosphere
Composition (NCERT): nitrogen and oxygen make up about 99% of clean, dry air: nitrogen 78%, oxygen 21%, and carbon dioxide, argon and other gases 1% by volume. Oxygen is the breath of life; nitrogen helps the growth of living organisms; carbon dioxide, though present in minute amounts, absorbs heat radiated by the Earth and keeps the planet warm, and is essential for plants.
Density and pressure: density is greatest at sea level and falls rapidly with height, which is why mountaineers carry oxygen cylinders. Temperature also falls as we go up. The atmosphere exerts pressure; air moves from high to low pressure, and moving air is wind.
| Layer (NCERT Class XI) | Height | Key facts |
|---|---|---|
| Troposphere | Average 13 km: about 8 km at the poles, 18 km at the equator | All weather and climate changes happen here; temperature falls by 1 °C for every 165 m |
| Stratosphere | Up to 50 km | Contains the ozone layer, which absorbs ultraviolet radiation |
| Mesosphere | Up to 80 km | Temperature falls again, to about −100 °C at 80 km |
| Thermosphere (with the ionosphere, 80–400 km) | Above 80 km | Charged particles reflect radio waves back to Earth; temperature rises with height |
| Exosphere | The top | Extremely rarefied; merges with outer space |
NCERT Class XI places ozone between 10 and 50 km above the surface. Its troposphere is thickest at the equator because strong convection carries heat to great heights.
The atmosphere in numbers and policy (dated)
Carbon dioxide (NOAA Global Monitoring Laboratory):
| Measure | Value |
|---|---|
| Global annual mean, 2024 | 422.79 ppm |
| Global annual mean, 2025 | 425.62 ppm |
| Mauna Loa annual mean, 2025 | 427.35 ppm |
| Mauna Loa monthly mean, May 2025 | 430.51 ppm |
| Mauna Loa monthly mean, May 2026 | 432.34 ppm |
The ozone layer. The Montreal Protocol, signed in 1987 and in force from 1989, phases out the production and consumption of ozone-depleting substances. Its Kigali Amendment (2016) added the phase-down of hydrofluorocarbons (HFCs), which replaced some of those substances and, though harmless to ozone, are powerful greenhouse gases (UN Environment Programme Ozone Secretariat).
India's climate targets (Nationally Determined Contributions):
- Updated NDC, approved by the Cabinet on 3 August 2022: reduce the emissions intensity of GDP by 45% by 2030 from the 2005 level, and reach about 50% of cumulative electric power installed capacity from non-fossil sources by 2030.
- NDC for 2031–2035, approved by the Cabinet on 25 March 2026: reduce emissions intensity by 47% by 2035 from the 2005 level; reach 60% non-fossil installed capacity by 2035; and create a carbon sink of 3.5 to 4.0 billion tonnes of CO₂ equivalent through forest and tree cover (PIB).
The Biosphere: the Domain of Life
The biosphere holds organisms from microbes and bacteria to huge mammals, broadly divided into the plant and animal kingdoms, all linked to one another and to the biosphere for survival (NCERT).
How the domains act on each other (NCERT):
- Cutting forests or clearing land for farming can strip soil from slopes quickly.
- Natural calamities change the surface: in the tsunami, parts of the Andaman and Nicobar Islands were submerged.
- Waste discharged into lakes and rivers makes the water unusable and harms other life.
- Emissions from industries, power plants and vehicles pollute the air; more CO₂ raises global temperatures, which is global warming.
So, NCERT concludes, we need to limit our use of the Earth's resources to keep the balance between the lithosphere, atmosphere and hydrosphere.
India's biodiversity (dated)
India is one of the world's 17 mega-biodiverse countries. With 2.4% of the world's land it accounts for about 8% of recorded species, including over 96,000 animal and 47,000 plant species (PIB, 7-Apr-2026). It holds 4 of the 36 global biodiversity hotspots: the Himalaya, the Western Ghats, Indo-Burma and Sundaland (PIB, 9-Oct-2025). Its protected-area network had 1,014 areas, including 106 national parks and 573 wildlife sanctuaries, as of 27 November 2023 (PIB).
Globally, the Kunming-Montreal Global Biodiversity Framework (2022) sets targets for 2030, including Target 2: at least 30% of degraded ecosystems under effective restoration, and Target 6: cutting the introduction and establishment of other invasive alien species by at least 50% (Convention on Biological Diversity).
PART 3 — UPSC Integration
The chapter's domains reappear across the syllabus. Continents, oceans and the Southern Ocean are Prelims geography; the layers of the atmosphere and the ozone layer lead into climatology; continental drift is a Mains staple. The interaction NCERT describes is the logic of GS3 environment: the same CO₂ that keeps the Earth warm is now at record levels, and India's 2035 targets are its answer within the Paris framework. Antarctica shows how a whole continent is governed by treaty, and why India's research stations there matter. In answers, give the domain, the mechanism and a dated figure.
Exam Strategy
Prelims traps:
- Africa is the only continent crossed by both Tropics and the Equator.
- Australia is the smallest continent and lies wholly in the Southern Hemisphere; Antarctica too lies wholly in the south.
- Indian Ocean is the only ocean named after a country.
- Southern Ocean: recognised by the IHO in 2023 (Resolution 02/2023), northern limit 60° S.
- Deepest point: NCERT's 11,022 m vs NOAA's about 10,935 m for Challenger Deep.
- Troposphere about 8 km at the poles, 18 km at the equator; ozone layer in the stratosphere.
- Antarctic Treaty (1959) bans military measures; the mining ban is in the Madrid Protocol (1991).
- India's NDC: 45% by 2030 (2022 NDC); 47% by 2035 and 60% non-fossil capacity (2026 NDC).
Mains angle: Explain how the four domains interact, with one human example for each, and connect rising CO₂ to India's climate commitments.
Practice Questions
Practice (UPSC-pattern, not past papers). Real UPSC questions on this chapter are listed in the PYQ box above.
Prelims:
Which continent is crossed by the Tropic of Cancer, the Equator and the Tropic of Capricorn?
(a) South America
(b) Africa
(c) Asia
(d) AustraliaThe Isthmus of Panama links:
(a) Asia and Africa
(b) Europe and Asia
(c) North America and South America
(d) Asia and North AmericaConsider the following statements:
- The International Hydrographic Organization recognised the Southern Ocean in 2023.
- The northern limit of the Southern Ocean is the parallel of 60° S.
- The Arctic Ocean is connected to the Atlantic by the Bering Strait.
Which of the statements given above are correct?
(a) 1 and 2 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
- The International Hydrographic Organization recognised the Southern Ocean in 2023.
The ban on mineral resource activities in Antarctica is contained in:
(a) the Antarctic Treaty, 1959
(b) the Protocol on Environmental Protection to the Antarctic Treaty (Madrid, 1991)
(c) UNCLOS, 1982
(d) the Montreal Protocol, 1987According to NCERT Class XI, the height of the troposphere is greatest at the equator because:
(a) gravity is weakest there
(b) strong convection carries heat to great heights
(c) the ozone layer is thickest there
(d) the Earth bulges at the equatorUnder the NDC for 2031–2035 approved in March 2026, India aims to reduce the emissions intensity of its GDP from the 2005 level by:
(a) 33–35% by 2030
(b) 45% by 2030
(c) 47% by 2035
(d) 60% by 2035
Mains:
- "The domains of the Earth are interdependent." Illustrate with examples of how human activity in one domain affects the others. (150 words)
📦 Revision Capsule
Hard Facts
- Domains: lithosphere (crust and soil), hydrosphere (water in all forms), atmosphere (to about 1,600 km; five layers), biosphere (zone of life).
- Continents: 7; Asia largest (one-third of land), Australia smallest; Africa crossed by both Tropics and the Equator.
- Oceans: Pacific > Atlantic > Indian > Southern > Arctic; Southern Ocean to 60° S, recognised by the IHO in 2023.
- Water: 71% of the surface; oceans 97.5%, fresh water 2.5%.
- Air: nitrogen 78%, oxygen 21%; CO₂ 425.62 ppm (global mean, 2025).
- Everest 8,848 m (NCERT) / 8,848.86 m (China–Nepal, Dec 2020); deepest 11,022 m (NCERT) / about 10,935 m (NOAA).
Core Concepts
- Life exists where land, water and air meet.
- The domains interact; human use of one changes the others.
- Continents drifted from Pangaea (Wegener, 1912; split began about 200 million years ago).
Confused Pairs
- Lithosphere (solid) vs hydrosphere (water) vs atmosphere (air) vs biosphere (life)
- Isthmus (land linking two landmasses) vs strait (water linking two seas)
- Antarctic Treaty (1959, no military) vs Madrid Protocol (1991, no mining)
- Troposphere (weather) vs stratosphere (ozone)
PYQ Pattern
- Mains GS1 asked about the theory of continental drift and the evidence for it (2013). See the PYQ box.
Sources
Sources
- NCERT, The Earth: Our Habitat (Class VI), ch. 5 "Major Domains of the Earth" (2020-21 print), and the Rationalised 2023-24 edition, ch. 5: NCERT's book archives as captured by the Wayback Machine, 2020 copy and 2023-24 copy.
- NCERT, Fundamentals of Physical Geography (Class XI): ch. 4 "Distribution of Oceans and Continents", kegy204; ch. 7 "Composition and Structure of Atmosphere", kegy207.
- Xinhua, "8,848.86 meters: China, Nepal jointly announce new height of Mt. Qomolangma", 8-Dec-2020.
- NOAA Global Monitoring Laboratory, CO₂ data files (read 2-Oct-2026): global annual means, Mauna Loa annual means, Mauna Loa monthly means. NOAA National Ocean Service, How deep is the ocean?
- IHO Secretariat, report to the UN Group of Experts on Geographical Names, 4th session, 2025 (CRP.157, Southern Ocean): unstats.un.org PDF.
- Antarctic Treaty Secretariat: The Antarctic Treaty (text); Protocol on Environmental Protection; Parties.
- UNEP Ozone Secretariat, The Montreal Protocol.
- PIB (Cabinet): Updated NDC, 3-Aug-2022; NDC 2031–2035, 25-Mar-2026. PIB (MoEFCC): India's Green Pathway, 7-Apr-2026; IUCN World Conservation Congress, 9-Oct-2025; India's Wildlife Conservation Milestones, 3-Mar-2025.
- Convention on Biological Diversity, Kunming-Montreal GBF: Target 2, Target 6.
