📘 IAS Prelims 2025 — GS-I Q.26 | Classroom Explanation

📌 Question

Q.26) Consider the following statements:

Statement I: The amount of dust particles in the atmosphere is more in subtropical and temperate areas than in equatorial and polar regions.

Statement II: Subtropical and temperate areas have less dry winds.

Which one of the following is correct in respect of the above statements?

(a) Both Statement I and Statement II are correct and Statement II explains Statement I
(b) Both Statement I and Statement II are correct but Statement II does not explain Statement I
(c) Statement I is correct but Statement II is not correct
(d) Statement I is not correct but Statement II is correct

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✅ Correct Answer: (c)

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🧑‍🏫 Classroom Explanation

This question tests understanding of atmospheric dust distribution, linked with wind systems, aridity, and climatic zones.

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🔍 Key Concept: Atmospheric Dust Particles

• Dust particles are solid aerosols suspended in the lower atmosphere
• Sources include:

• Deserts
• Dry soils
• Volcanic eruptions
• Human activities
  • Though concentrated near the surface, they can be lifted to higher altitudes by strong convection and winds

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🔍 Statement-wise Analysis

✅ Statement I: Correct

• Subtropical and temperate regions show higher dust concentration because:

• Presence of arid and semi-arid belts
• Frequent dry winds capable of lifting dust
• Large deserts located near subtropics (Sahara, Arabian, Australian)

• In contrast:

• Equatorial regions receive heavy rainfall → dust is washed out
• Polar regions are ice-covered → minimal loose material

➡️ Hence, Statement I is correct.

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❌ Statement II: Incorrect

• Subtropical and temperate regions do not have less dry winds
• In fact, they experience:

• Trade winds
• Westerlies
• Hot desert winds (e.g., Harmattan, Sirocco, Santa Ana)

• These dry winds are responsible for higher dust load, not lower

➡️ Hence, Statement II is incorrect.

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🧮 Logical Elimination (UPSC Style)

• Statement I → True
• Statement II → False

➡️ Correct option: (c)

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🎯 Final Answer

✅ Correct Answer: (c)

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📦 Info Box — Extra Points (Prelims Value Add)

• Maximum dust concentration is found between 20°–40° latitudes
• Rainfall acts as a dust cleanser by wet deposition
• Dust affects:

• Cloud formation (condensation nuclei)
• Solar radiation balance
• Monsoon dynamics

• Major global dust sources:

• Sahara Desert (largest contributor)
• Arabian Desert
• Australian deserts

• Polar regions have cleaner air due to:

• Snow cover
• Low wind velocity
• Minimal human activity

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🔗 Bridge Points (Future Questions)

• Aerosols and climate change
• Dust storms and monsoon variability
• Global atmospheric circulation and aridity belts

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📍 GS Mapping

GS Paper I
Subject: Geography
Theme: Climatology — Atmosphere
Nature: Conceptual + Reasoning

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