UPSC Prelims 2025 Q26: Geography – Atmosphere & Climatology
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
Answer: (c) Statement I is correct but Statement II is not correct
Explanation
Dust particles in the atmosphere — where and why
| Region | Dust level | Reason |
|---|---|---|
| Equatorial | Low | Heavy convectional rain washes dust out of the air |
| Subtropical | High | Hot deserts (Sahara, Arabia, Thar) and dry trade winds lift loose soil |
| Temperate | High | Continental interiors and steppes; dry westerlies carry dust |
| Polar | Low | Snow and ice cover; no loose dry soil to lift |
Statement I — correct. NCERT notes that dust is concentrated in subtropical and temperate regions.
Statement II — not correct. These areas have more dry winds, not less, and that is exactly why they are dusty.
Answer: (c) Statement I is correct but Statement II is not correct.
Why each option is right or wrong
- (a) Incorrect. Statement II is false, so it cannot explain Statement I.
- (b) Incorrect. Both are not correct; subtropical and temperate areas have more, not fewer, dry winds.
- (c) CORRECT. Dust is higher in subtropical and temperate belts because of their dry winds; Statement II reverses this.
- (d) Incorrect. Statement I is correct; it is Statement II that is wrong.
Key point
Dust is highest in subtropical and temperate belts because of dry winds; equatorial and polar air is cleaner.
Remember
More dry winds = more dust: subtropical and temperate belts are the dustiest.
Common mistakes
- Assuming hot equatorial air is dusty; daily convectional rain keeps it clean.
- Accepting Statement II without noticing the reversal — the true reason is more dry wind.
- Forgetting that dust particles act as hygroscopic nuclei for cloud and fog formation.
Exam tip
In 'Statement I/II' questions, check each statement alone first. Only if both are true ask whether II explains I.
Sources
- NCERT Class XI — Fundamentals of Physical Geography, Ch 8 (Composition and Structure of Atmosphere)
- G.C. Leong — Certificate Physical and Human Geography (The Atmosphere)