UPSC Prelims 2025
World Geography Previous Year Questions (PYQs)

Detailed Explanation:

Scientific studies confirm that the Earth's rotational axis is gradually shifting, a phenomenon known as polar drift. Melting polar ice redistributes mass from the poles toward the equator, changing the Earth's moment of inertia and affecting its rotation. Solar flares and CMEs do impact the upper atmosphere, but they do not significantly alter the Earth's rotational axis.

✅ Statement I is Correct: Satellite observations show that Earth's rotational axis is drifting and its rotation rate is changing slightly.

✅ Statement II is Correct: Solar flares and CMEs transfer large amounts of energy to the thermosphere and magnetosphere.

✅ Statement III is Correct: Melted polar ice redistributes water toward lower latitudes, especially near the equator.

❌ Statement II does NOT explain Statement I: Solar activity affects the atmosphere and satellites but not the Earth's rotational axis significantly.

✅ Statement III explains Statement I: Redistribution of mass from poles to equator changes Earth's moment of inertia, causing polar drift and slight rotational changes.

Concept Note:

Moment of Inertia is the resistance of a rotating object to changes in its rotation. When mass moves away from the rotational axis (toward the equator), the moment of inertia increases, leading to changes in rotational speed and axis orientation.

Detailed Explanation:

All three statements are important geological evidences supporting Alfred Wegener’s Continental Drift Theory. Matching rock formations, similar mineral deposits, and identical sedimentary sequences across widely separated continents indicate that these landmasses were once part of a single supercontinent.

✅ Statement I is Correct: The ancient rock belts of Brazil and Western Africa match in age and structure, showing that the two continents were once connected.

✅ Statement II is Correct: Ghana's gold placer deposits are linked to gold-bearing source rocks found in Brazil, suggesting the continents were previously joined.

✅ Statement III is Correct: Gondwana sediments found in India have matching counterparts in Africa, South America, Antarctica, Australia, Madagascar, and the Falkland Islands.

Short Notes : Continental Drift Theory

• Proposed by Alfred Wegener in 1912.

• Continents were once part of Pangaea.

• Matching rock formations across continents support continental drift.

• Similar mineral deposits indicate former land connections.

• Gondwana sediments occur across several Southern Hemisphere continents.

• Geological evidence is one of the strongest proofs of continental drift.

Detailed Explanation:

The concentration of atmospheric dust is generally higher in subtropical and temperate regions because these areas contain large deserts, semi-arid lands, sparse vegetation, and stronger dry winds that can easily lift dust particles into the atmosphere. Therefore, Statement I is correct. However, Statement II is incorrect because these regions experience more dry winds, not less.

✅ Statement I is Correct: Subtropical and temperate regions have higher dust content due to dry conditions, deserts, sparse vegetation, and wind action.

❌ Statement II is Incorrect: These regions experience more dry winds, which help transport dust particles over long distances.

Concept Note:

Dust particles (Aerosols) in the atmosphere originate from deserts, dry soils, volcanic eruptions, sea salts, and human activities. The world's major dust sources, such as the Sahara Desert, are located in subtropical regions, making these areas dust-rich.

Detailed Explanation:

In January (Northern Hemisphere winter), land cools much faster than oceans because land has a lower heat capacity. As a result, continents become much colder than nearby oceans at the same latitude. This temperature contrast causes isotherms to bend equatorward over land and poleward over oceans.

✅ Statement I is Correct: In January, isotherms dip southward over cold landmasses and curve northward over relatively warm oceans in the Northern Hemisphere.

✅ Statement II is Correct: Oceans retain heat longer than land, making oceanic areas warmer than continental areas during winter.

✅ Statement II explains Statement I: The temperature difference between colder land and warmer oceans is the direct reason for the bending of isotherms.

Short Notes: Isotherms

• Isotherms are lines joining places with equal temperature.

• In January, Northern Hemisphere continents are colder than oceans.

• Land heats and cools faster because it has lower specific heat than water.

• Oceans act as heat reservoirs and lose heat slowly.

• Isotherms bend equatorward over land and poleward over oceans in winter.

• In July, the pattern is generally reversed in the Northern Hemisphere.

• The greatest isotherm deviations occur over large landmasses such as Eurasia and North America.

Detailed Explanation:

Correct Answer: ✅ Option 3 (I, II and III)

All three statements correctly describe the role of the atmosphere in maintaining Earth's temperature. The atmosphere acts like a thermal blanket by absorbing and trapping heat, preventing the Earth from becoming extremely cold. Greenhouse gases such as carbon dioxide, methane, and water vapour are especially effective in trapping outgoing infrared radiation.

✅ Statement I is Correct: Without the atmosphere, Earth would lose most of its heat to space, and average surface temperatures would be well below freezing.

✅ Statement II is Correct: The atmosphere absorbs and retains heat, maintaining a habitable average temperature through the natural greenhouse effect.

✅ Statement III is Correct: Greenhouse gases such as carbon dioxide, methane, and water vapour efficiently absorb and trap infrared radiation.

Short Notes: Greenhouse Effect

• The natural greenhouse effect keeps Earth warm enough to support life.

• Earth's average temperature is about 15°C with the atmosphere.

• Without the atmosphere, the average temperature would be around –18°C.

• Carbon dioxide (CO₂), methane (CH₄), and water vapour are major greenhouse gases.

• Greenhouse gases absorb outgoing infrared radiation emitted by Earth's surface.

• The greenhouse effect is a natural process, but excessive greenhouse gases enhance global warming.

• Water vapour is the most abundant natural greenhouse gas.

Detailed Explanation:

Correct Answer: ✅ Option 4 (None)

The Equator does not pass through any of the three given water bodies. Although Lake Tanganyika is located in East Africa near the Equator, it lies entirely south of it. Tonlé Sap is located in Cambodia in Southeast Asia, while Patos Lagoon is situated in southern Brazil, both far from the Equator.

❌ Statement I is Incorrect: Lake Tanganyika lies south of the Equator and does not cross it.

❌ Statement II is Incorrect: Tonlé Sap is located in Cambodia, north of the Equator.

❌ Statement III is Incorrect: Patos Lagoon is located in southern Brazil, well south of the Equator.

Short Notes: Important Lakes and Lagoons of the World

• Lake Tanganyika is one of the world's deepest freshwater lakes.

• Tonlé Sap is Southeast Asia's largest freshwater lake.

• Tonlé Sap is known for its seasonal reversal of river flow.

• Patos Lagoon is the largest lagoon in Brazil.

• The Equator passes through countries such as Brazil, Ecuador, Colombia, Kenya, Uganda, and Indonesia.

• Major equatorial lakes include parts of Lake Victoria, but not Lake Tanganyika.

• Location-based questions are common in UPSC Geography.

Detailed Explanation:

Correct Answer: ✅ Option 3

Chalk and clay differ mainly in permeability, not simply in porosity. Chalk contains many interconnected pores, allowing water to pass through easily. Clay also has pores, but they are extremely small and poorly connected, so water movement is very slow. Therefore, Statement II is correct and explains Statement I, while Statement III is incorrect.

✅ Statement I is Correct: Chalk is highly permeable, whereas clay is one of the least permeable rocks/soils.

✅ Statement II is Correct: Chalk is porous and can absorb and transmit water through its interconnected pore spaces.

❌ Statement III is Incorrect: Clay is not non-porous; it is porous but has very tiny pores that restrict water movement.

Short Notes: Porosity and Permeability

• Porosity is the percentage of pore spaces in a rock or soil.

• Permeability is the ability of water to move through those pore spaces.

• A rock can be porous but impermeable if pores are not well connected.

• Chalk is both porous and permeable.

• Clay is porous but largely impermeable due to tiny pore size.

• Groundwater is commonly stored in porous and permeable rocks called aquifers.

• Sandstone and chalk are common aquifer rocks.

Detailed Explanation:

Correct Answer: ✅ Option 3 (Only Four)

The Andes Mountains, the world's longest continental mountain range, extend along the western edge of South America. Among the given countries, the Andes pass through Bolivia, Colombia, Ecuador, and Venezuela. They do not pass through Brazil or Paraguay.

✅ Statement I is Correct: The Andes pass through Bolivia and include the famous Altiplano Plateau.

❌ Statement II is Incorrect: Brazil lies mainly on the Brazilian Highlands (Brazilian Plateau), not in the Andes region.

✅ Statement III is Correct: In Colombia, the Andes split into three parallel mountain chains (Cordilleras).

✅ Statement IV is Correct: The Andes run through Ecuador from north to south.

❌ Statement V is Incorrect: Paraguay lies in the interior lowlands east of the Andes.

✅ Statement VI is Correct: The Venezuelan Andes (Cordillera de Mérida) form the northern extension of the Andes.

Short Notes: Andes Mountains

• Andes are the longest continental mountain range in the world.

• Length: approximately 7,000 km.

• Highest peak: Aconcagua (6,961 m) in Argentina.

• The Andes extend through Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile, and Argentina.

• The Altiplano Plateau lies mainly in Bolivia and Peru.

• Formed by the subduction of the Nazca Plate beneath the South American Plate.

• Rich in minerals such as copper, silver, and tin.

Detailed Explanation:

Correct Answer: ✅ Option 2 (Only Four)

When counting all official time zones, including overseas territories and external territories, the United Kingdom, Denmark, New Zealand, and Australia each have more than four time zones. Brazil, however, has exactly four time zones, not more than four.

✅ Statement I: United Kingdom – Correct

• The UK has 9 time zones when overseas territories are included.

• Territories such as the Falkland Islands, Gibraltar, Bermuda, and Pitcairn Islands contribute to multiple time zones.

✅ Statement II: Denmark – Correct

• Denmark has more than four time zones due to Greenland and the Faroe Islands.

• Greenland alone spans several time zones.

✅ Statement III: New Zealand – Correct

• New Zealand has 5 time zones when including territories such as the Chatham Islands, Tokelau, and the Ross Dependency (Antarctica).

✅ Statement IV: Australia – Correct

• Australia has 8–9 time zones when all external territories are counted.

• These include territories such as Norfolk Island, Christmas Island, and Cocos (Keeling) Islands.

❌ Statement V: Brazil – Incorrect

• Brazil officially has 4 time zones, not more than four.

Short Notes: World Time Zones

• The Earth is divided into 24 standard time zones.

• Each time zone generally covers 15° of longitude.

• Countries with large territories often have multiple time zones.

• Russia has the highest number of time zones (11).

• France has the most time zones globally (12) when overseas territories are included.

• Overseas territories significantly increase the number of time zones for some countries.

• India follows a single time zone: IST (UTC +5:30).

Detailed Explanation:

Correct Answer: ✅ Option 1 (I only)

Anadyr (Russia) and Nome (Alaska, USA) are located on opposite sides of the International Date Line (IDL). Although they are geographically close, crossing the IDL results in a change of calendar date. Therefore, people in these cities can experience the same part of the day but on different dates.

✅ Statement I is Correct: Anadyr and Nome are separated by the International Date Line, so they can have similar clock times but different calendar dates.

❌ Statement II is Incorrect: Anadyr is ahead of Nome. If it is Monday in Anadyr, it would still be Sunday in Nome, not Tuesday.

Short Notes: International Date Line (IDL)

• The International Date Line lies roughly along 180° longitude.

• Crossing the IDL from west to east subtracts one day.

• Crossing the IDL from east to west adds one day.

• The IDL is not perfectly straight; it bends to avoid splitting countries and island groups.

• Russia and Alaska are separated by the Bering Strait and the IDL.

• Places close to each other geographically can have different calendar dates due to the IDL.

• The IDL is important for global travel, communication, and timekeeping.

Detailed Explanation:

Correct Answer: ✅ Option 4 (None)

All three pairs are incorrectly matched. The question tests knowledge of important regions and islands of Europe and their respective countries.

❌ Pair I is Incorrect: Mallorca is part of Spain, not Italy. It is the largest island of the Balearic Islands in the Mediterranean Sea.

❌ Pair II is Incorrect: Normandy is a historic and administrative region of France, not Spain.

❌ Pair III is Incorrect: Sardinia is an island belonging to Italy, not France.

Short Notes: Important Regions of Europe

• Mallorca is the largest island of Spain's Balearic Islands.

• Normandy is located in northwestern France along the English Channel.

• Normandy is famous for the D-Day Landings (1944) during Normandy Landings.

• Sardinia is the second-largest island in the Mediterranean Sea after Sicily.

• Sardinia is an autonomous region of Italy.

• The Balearic Islands include Mallorca, Menorca, Ibiza, and Formentera.

• European map-based questions are common in UPSC examinations.

Detailed Explanation:

Correct Answer: ✅ Option 3 (All the three)

All three pairs are correctly matched. These countries are globally known for their abundant reserves and production of strategically important minerals that are essential for modern industries, renewable energy technologies, and manufacturing.

✅ Pair I is Correct: Botswana is one of the world's leading diamond-producing countries, and diamonds are the backbone of its economy.

✅ Pair II is Correct: Chile possesses vast lithium reserves, especially in the Atacama Desert, making it a major global lithium supplier.

✅ Pair III is Correct: Indonesia is the world's largest producer of nickel, a critical mineral for batteries and stainless steel production.

Short Notes: Critical Minerals of the World

• Diamonds are important for both jewelry and industrial applications.

• Botswana is among the world's top diamond exporters.

• Lithium is a key component in electric vehicle (EV) batteries.

• Chile, Australia, and Argentina form the famous "Lithium Triangle" region (Chile and Argentina directly; Bolivia is also a major reserve holder).

• Nickel is essential for battery manufacturing and stainless steel production.

• Indonesia holds some of the world's largest nickel reserves.

• Demand for lithium and nickel is increasing due to the global transition to clean energy.