UPSC CSE Prelims
World Geography Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 2 — 1, 3 and 4 only

This question tests knowledge of the geographical boundaries of major seas and their bordering countries. Out of five pairs, three are correctly matched while two contain geographical errors.

✅ Pair 1 – Correct: Albania borders the Adriatic Sea, which separates the Italian Peninsula from the Balkan Peninsula.
❌ Pair 2 – Incorrect: Croatia does not border the Black Sea; it borders the Adriatic Sea. The Black Sea is bordered by Bulgaria, Georgia, Romania, Russia, Turkey, and Ukraine.
✅ Pair 3 – Correct: Kazakhstan is one of the five littoral states of the Caspian Sea (along with Russia, Turkmenistan, Iran, and Azerbaijan).
✅ Pair 4 – Correct: Morocco borders the Mediterranean Sea along its northern coast.
❌ Pair 5 – Incorrect: Syria does not border the Red Sea; it has a Mediterranean coastline. The Red Sea is bordered by Saudi Arabia, Yemen, Egypt, Sudan, Eritrea, and Djibouti.

📝 Short Notes: Major Seas and Their Littoral States

Detailed Explanation:

Answer: Option 2 — Clouds reflect back the Earth's radiation.

Dewdrops form when the Earth's surface cools below the dew point through radiation heat loss on clear nights. On cloudy nights, clouds act as a blanket by reflecting the Earth's longwave radiation back to the surface, preventing sufficient cooling. This keeps the temperature above the dew point, thus preventing dew formation.

📝 Short Notes: Dew Formation and Radiation

• Dew Formation: Dew forms when water vapor in the air condenses on cool surfaces when the surface temperature drops to or below the dew point.
• Radiational Cooling: On clear nights, the Earth's surface radiates heat (longwave infrared radiation) into space, causing surface temperatures to drop rapidly.
• Role of Clouds: Clouds contain water droplets that absorb and reflect back the Earth's outgoing longwave radiation, acting as an insulating blanket.
• Greenhouse Effect: This reflection by clouds is similar to the greenhouse effect, where certain atmospheric components trap heat near the surface.
• Clear vs Cloudy Nights: Clear nights experience maximum cooling and dew formation, while cloudy nights remain warmer with minimal or no dew.
• Dew Point: The temperature at which air becomes saturated (100% relative humidity) and water vapor begins to condense.

Detailed Explanation:

Answer: Option 4 — 1, 2 and 3

All three statements about coral reefs are correct. Coral reefs are predominantly found in tropical waters where conditions are optimal for their growth. The distribution of coral reefs is highly concentrated, with Australia, Indonesia, and the Philippines together hosting more than one-third of the world's coral reefs. Remarkably, coral reefs exhibit exceptional biodiversity not just in terms of species numbers but also in phyletic diversity, hosting 32 out of 34 animal phyla compared to only 9 phyla in tropical rainforests.

✅ Statement 1 – Correct: Coral reefs primarily thrive in warm, shallow, clear tropical waters between 30°N and 30°S latitudes, where sea surface temperatures typically remain between 20°C and 30°C.
✅ Statement 2 – Correct: These three countries (Australia, Indonesia, and the Philippines) account for over 40% of the world's coral reef area, with Indonesia holding approximately 18%, Australia 17%, and the Philippines 9%.
✅ Statement 3 – Correct: While rainforests have a higher number of species, coral reefs have greater phyletic diversity, hosting 32 of the 34 recognized animal phyla compared to only about 9 phyla found in tropical rainforests.

📝 Short Notes: Coral Reefs

• Definition: Coral reefs are underwater structures made from calcium carbonate secreted by corals, which are marine invertebrates belonging to the class Anthozoa.
• Geographic Distribution: Found primarily in tropical and subtropical waters between 30°N and 30°S latitudes, covering less than 0.1% of the ocean floor but supporting 25% of marine species.
• Optimal Conditions: Require warm water (20-30°C), shallow depth (less than 50m for sunlight penetration), clear water with low turbidity, normal salinity (32-42 ppt), and minimal pollution.
• Major Coral Reef Regions: Great Barrier Reef (Australia - largest), Coral Triangle (Indonesia, Philippines, Malaysia, Papua New Guinea), Caribbean Sea, Red Sea, and Indian Ocean islands.
• Biodiversity Hotspots: Host 32 out of 34 animal phyla (highest phyletic diversity on Earth), support over 4,000 fish species, 800 coral species, and countless invertebrates.
• Ecological Importance: Provide coastal protection from waves and storms, support fisheries, generate tourism revenue, and are sources of medicinal compounds.
• Threats: Climate change and ocean warming (causing coral bleaching), ocean acidification, overfishing, pollution, destructive fishing practices, and coastal development.

Detailed Explanation:

Answer: Option 1 — Bengaluru

Delhi is located at approximately 77.10°E longitude, and among the given options, Bengaluru (77.59°E) lies closest to this longitude with a difference of only about 0.49°. Hyderabad (78.49°E), Nagpur (79.09°E), and Pune (73.86°E) are all farther away from Delhi's longitude.

📝 Short Notes: Longitudes of Major Indian Cities

• Bengaluru and Delhi nearly share the same longitudinal line, making them closest in east-west positioning.
• Pune lies significantly west of Delhi, while Hyderabad and Nagpur lie progressively east.
• Understanding longitude positions helps in determining time zones and relative geographical positioning of cities.

Detailed Explanation:

Answer: Option 3 — 1 and 3 only

This question tests knowledge about Earth's magnetic field reversals and the evolution of Earth's atmosphere. Statements 1 and 3 are scientifically accurate, while Statement 2 contains factual errors about the early Earth's atmospheric composition.

✅ Statement 1 – Correct: The Earth's magnetic field undergoes geomagnetic reversals approximately every few hundred thousand years, a phenomenon recorded in volcanic rocks and ocean floor sediments.

❌ Statement 2 – Incorrect: The early Earth's atmosphere (over 4 billion years ago) had virtually no free oxygen and was dominated by carbon dioxide, water vapor, nitrogen, and methane—not 54% oxygen.

✅ Statement 3 – Correct: Living organisms, particularly cyanobacteria through photosynthesis during the Great Oxygenation Event (~2.4 billion years ago), fundamentally transformed Earth's atmosphere by adding oxygen.

📝 Short Notes: Earth's Atmospheric Evolution

• Primordial Atmosphere: Early Earth (4+ billion years ago) had no free oxygen; atmosphere consisted mainly of hydrogen, helium, water vapor, methane, ammonia, and carbon dioxide.
• Secondary Atmosphere: Formed through volcanic outgassing, releasing CO₂, nitrogen, water vapor, and sulfur compounds.
• Great Oxygenation Event (GOE): Around 2.4 billion years ago, cyanobacteria began photosynthesis, gradually increasing atmospheric oxygen from ~0% to ~21% today.
• Geomagnetic Reversals: Earth's magnetic poles switch positions irregularly; last reversal occurred ~780,000 years ago (Brunhes-Matuyama reversal).
• Evidence of Reversals: Preserved in magnetized minerals in volcanic rocks (paleomagnetism) and oceanic crust spreading from mid-ocean ridges.
• Impact on Life: The oxygen revolution caused mass extinction of anaerobic organisms but enabled evolution of complex aerobic life forms.

Detailed Explanation:

Answer: Option 3 — 3 only

This question tests knowledge about mining regulations and mineral distribution in India. Among the three statements, only Statement 3 about Rajasthan having iron ore mines is correct.

❌ Statement 1 – Incorrect: State Governments have the power to auction non-coal mines under the Mines and Minerals (Development and Regulation) Amendment Act, 2015.

❌ Statement 2 – Incorrect: Both Andhra Pradesh (Anantapur district) and Jharkhand (several districts) have gold deposits and active mining operations.

✅ Statement 3 – Correct: Rajasthan has significant iron ore reserves, particularly in districts like Jaipur, Udaipur, and Jhunjhunu.

📝 Short Notes: Mineral Distribution in India

• Iron Ore: Major states include Odisha (largest producer), Chhattisgarh, Karnataka, Jharkhand, and Rajasthan. Rajasthan has deposits in Jaipur, Udaipur, Dausa, and Jhunjhunu districts.
• Gold: Found in Karnataka (Kolar Gold Fields, Hutti), Andhra Pradesh (Anantapur), Jharkhand (Singhbhum), Chhattisgarh, and Madhya Pradesh. Kolar Gold Fields were once among the deepest mines in the world.
• Mining Regulation: The MMDR Amendment Act 2015 empowered state governments to conduct auctions for mining leases of non-coal minerals through competitive bidding, replacing the earlier discretionary allocation system.
• Constitutional Provisions: Minerals are covered under Entry 23 of State List (Concurrent List after amendments), while regulation of mines and mineral development falls under Union List Entry 54.
• Major Mineral Producing States: Jharkhand (coal, iron ore, copper, mica), Odisha (iron ore, bauxite, chromite), Chhattisgarh (coal, iron ore, bauxite), Karnataka (iron ore, gold, manganese), Rajasthan (zinc, lead, marble, granite, sandstone, iron ore).

Detailed Explanation:

Answer: Option 3 — 3 and 4 only

The Mediterranean Sea borders several countries in Southern Europe, North Africa, and Western Asia. Among the given options, only Lebanon and Syria have coastlines along the eastern Mediterranean Sea.

❌ Statement 1 – Incorrect: Jordan does not border the Mediterranean Sea; it is separated from it by Israel and has only a short coastline on the Gulf of Aqaba (Red Sea).

❌ Statement 2 – Incorrect: Iraq does not border the Mediterranean Sea; it is located further east with maritime access only through the Persian Gulf.

✅ Statement 3 – Correct: Lebanon is a Levantine country with its entire western border formed by the Mediterranean Sea coastline.

✅ Statement 4 – Correct: Syria has a coastline along the eastern Mediterranean Sea, located between Turkey to the north and Lebanon to the south.

Detailed Explanation:

Answer: Option 3 — Chandipur

Chandipur Beach in Balasore district of Odisha is famous for its unique phenomenon where the sea recedes up to 2-5 kilometers during low tide, exposing the sea floor for several hours. This extraordinary tidal behavior occurs twice daily due to the beach's exceptionally shallow gradient and flat sea bed, allowing visitors to literally walk on the sea floor. The water returns during high tide, making it one of the most distinctive coastal features in India.

Detailed Explanation:

✅ Statement 1 – Correct: The Sun's gravitational force contributes to tidal generation, producing a tidal force approximately 46% as strong as the Moon's despite its greater mass but larger distance.

✅ Statement 2 – Correct: The Moon's gravitational pull is the primary cause of tides, creating a tidal bulge on the side of Earth facing the Moon due to stronger gravitational attraction on ocean water.

✅ Statement 3 – Correct: Centrifugal force from the Earth-Moon system's rotation around their common barycenter creates a second tidal bulge on the side of Earth opposite to the Moon.

Detailed Explanation:

The North and South Equatorial Currents flow westward due to Trade Winds, causing water to accumulate on the western sides of ocean basins and creating a higher sea level in the west.

This convergence and water pile-up generates a pressure gradient that drives the Equatorial Counter-Current to flow eastward between the two equatorial currents in the Doldrums region (where surface winds are weak), restoring oceanic equilibrium.

Detailed Explanation:

❌ Statement 1 – Incorrect: Westerlies blow between 30° and 60° latitudes in both hemispheres (i.e., 30°–60° N and 30°–60° S separately), not between 30° N and 60° S as stated.

✅ Statement 2 – Correct: Western disturbances originating over the Mediterranean region bring winter rains to North-Western India and are carried by westerlies.

Detailed Explanation:

Jordan is the only country among the four that does not have a coastline on the Mediterranean Sea.

Syria, Lebanon, and Israel all have direct access to the Mediterranean, while Jordan is bordered by Israel to the west, which separates it from the sea; Jordan's only coastline is on the Gulf of Aqaba (Red Sea).

Detailed Explanation:

✅ Option 2 – Correct: The Inter-Tropical Convergence Zone (ITCZ) remains predominantly north of the equator and seldom migrates into the South Atlantic and South Eastern Pacific regions, depriving them of the necessary low-level atmospheric instability and converging trade winds required for cyclone genesis.

❌ Option 1 – Incorrect: While cold ocean currents (Benguela Current in South Atlantic, Humboldt Current in South Eastern Pacific) do lower temperatures, sea surface temperatures are not the primary limiting factor.

❌ Option 3 – Incorrect: Coriolis force is adequate at these tropical latitudes (generally above 5° latitude) for cyclone formation; it is not too weak.

❌ Option 4 – Incorrect: Presence or absence of land does not prevent cyclone origination over ocean basins; cyclones form over open waters.

Detailed Explanation:

The passage describes the Equatorial climate which experiences convectional rainfall with a predictable daily pattern.

Morning: Clear, bright weather with sea breeze due to proximity to oceans and low pressure.

Afternoon: Intense solar heating causes rapid convection currents, forming cumulonimbus clouds that produce short, intense thunderstorms with lightning.

Evening: Rain clears quickly, returning to calm conditions — this daily convectional cycle repeats year-round in regions near the Equator (between 5°N and 5°S), unlike Savannah (distinct wet/dry seasons), Monsoon (seasonal wind reversal), or Mediterranean (dry summers, wet winters).

Detailed Explanation:

Golan Heights is a 1,200 sq-km rocky plateau located in the Middle East, strategically positioned between Syria, Israel, Lebanon, and Jordan.

Originally Syrian territory, it was occupied by Israel in 1967 during the Six-Day War and later annexed in 1981 (not internationally recognized).