UPSC Prelims 2020
World Geography Previous Year Questions (PYQs)

Detailed Explanation:

Answer: Option 3 — 3 and 4 only

This question tests the knowledge of major world rivers and their drainage systems. Out of the four pairs, only pairs 3 and 4 are correctly matched, while pairs 1 and 2 contain errors regarding the water bodies into which these rivers flow.

❌ Pair 1 – Incorrect: The Mekong River flows into the South China Sea, not the Andaman Sea. It originates in the Tibetan Plateau and passes through China, Myanmar, Laos, Thailand, Cambodia, and Vietnam.

❌ Pair 2 – Incorrect: The Thames River flows into the North Sea, not the Irish Sea. It flows entirely within England.

✅ Pair 3 – Correct: The Volga River, Europe's longest river, originates in Russia and correctly flows into the Caspian Sea.

✅ Pair 4 – Correct: The Zambezi River originates in Zambia and flows through several countries before emptying into the Indian Ocean via Mozambique.

📝 Short Notes: Major World Rivers and Their Drainage

Detailed Explanation:

Answer: Option 2 — 2 only

Ocean Mean Temperature (OMT) is measured up to the depth of the 26°C isotherm and serves as a reliable indicator of upper ocean heat content for monsoon prediction. Statement 1 is incorrect because the depth of the 26°C isotherm in the south-western Indian Ocean during January-March is approximately 59 meters, not 129 meters. Statement 2 is correct as OMT data collected during January-March can indeed be used to assess whether Indian Summer Monsoon Rainfall (ISMR) will be above or below the long-term mean.

❌ Statement 1 – Incorrect: The depth of 26°C isotherm is approximately 59 meters in the south-western Indian Ocean during January-March, not 129 meters.
✅ Statement 2 – Correct: OMT collected during January-March is used to predict whether ISMR will be above or below the long-term mean, making it a valuable forecasting tool.

📝 Short Notes: Ocean Mean Temperature (OMT)

• Definition: OMT is the average temperature of the ocean water column from the surface down to the depth of the 26°C isotherm (D₂₆).
• Significance: OMT is a more stable and reliable indicator of upper ocean heat content compared to Sea Surface Temperature (SST) alone.
• Monsoon Prediction: Research by Indian Institute of Tropical Meteorology (IITM) shows that OMT data from January-March in the south-western Indian Ocean can predict Indian Summer Monsoon Rainfall with greater accuracy.
• Depth Measurement: The 26°C isotherm depth varies spatially and temporally; in the south-western Indian Ocean during January-March, it is approximately 59 meters.
• Advantage over SST: Unlike SST which can fluctuate rapidly due to surface processes, OMT represents the integrated heat content of the upper ocean layer.
• Predictive Value: Higher OMT values generally indicate favorable conditions for above-normal monsoon rainfall over India.

Detailed Explanation:

Answer: Option 3 — 2 only

Only statement 2 is correct. Jet streams occur in both hemispheres, not just the Northern Hemisphere. The eye of a cyclone is warmer than its surroundings due to adiabatic heating from subsiding air, not cooler. Only strong tropical cyclones develop a well-defined eye structure.

✅ Statement 1 – Incorrect: Jet streams occur in both the Northern and Southern Hemispheres at high altitudes (10-15 km), not exclusively in the Northern Hemisphere.
✅ Statement 2 – Correct: Only some cyclones, particularly intense tropical cyclones (hurricanes/typhoons), develop a well-defined eye at their center.
❌ Statement 3 – Incorrect: The eye of a cyclone is warmer (2-10°C higher) than the surroundings due to adiabatic heating from subsiding air, not cooler.

📝 Short Notes: Tropical Cyclones and Jet Streams

Detailed Explanation:

Answer: Option 4 — 2, 3 and 4 only

In India, major minerals are those specified in the First Schedule of the Mines and Minerals (Development and Regulation) Act, 1957. Bentonite is classified as a minor mineral, while Chromite, Kyanite, and Sillimanite are all major minerals.

1. Bentonite – Minor Mineral: Bentonite is a clay mineral used in drilling mud, foundry sand, and civil engineering applications. It is listed under minor minerals.

2. Chromite – Major Mineral ✅: Chromite is the only ore of chromium and is essential for manufacturing stainless steel and various alloys. It is a major mineral.

3. Kyanite – Major Mineral ✅: Kyanite is a refractory mineral used in ceramics and high-temperature industrial applications. It is classified as a major mineral.

4. Sillimanite – Major Mineral ✅: Sillimanite is another refractory mineral with applications in metallurgy and industrial furnaces. It is a major mineral.

📝 Short Notes: Major vs Minor Minerals in India

• Refractory Minerals: Kyanite and Sillimanite are aluminum silicate minerals with high heat resistance, crucial for refractory (heat-resistant) materials.
• Chromite in India: India has significant chromite reserves, mainly in Odisha (about 98% of national reserves).
• MMDR Amendment 2015: Provided greater transparency in mineral allocation through auction mechanism for major minerals.