Authentic Classroom Explanation by IAS Monk

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📍 The Question

Consider the following statements:

Statement-I:
Thickness of the troposphere at the equator is much greater as compared to the poles.

Statement-II:
At the equator, heat is transported to great heights by strong convectional currents.

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 incorrect
(d) Statement-I is incorrect, but Statement-II is correct

Correct Answer: (a) Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

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🎯 Theme of the Question

Physical Geography | Atmosphere | Troposphere | Convection & Heat Transport

This question tests conceptual clarity about vertical temperature structure and latitudinal variation of the troposphere.

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🧠 Classroom Explanation

Let us analyse both statements carefully.

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🔹 Statement-I: Thickness of the troposphere at the equator is much greater than at the poles. ✅

• The troposphere is the lowermost layer of the atmosphere
• Its thickness varies with latitude:
  • ~18 km at the equator
  • ~8 km at the poles
• Hence, the troposphere is thickest at the equator

✔️ Statement-I is correct

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🔹 Statement-II: At the equator, heat is transported to great heights by strong convectional currents. ✅

• Equatorial regions receive maximum insolation
• Intense surface heating causes:
  • Strong convectional uplift
  • Vertical transport of heat and moisture
• This upward movement pushes the upper boundary of the troposphere to greater heights

✔️ Statement-II is correct

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🔗 Relationship between the statements

• Strong convection at the equator is the direct reason for greater tropospheric thickness
• Therefore, Statement-II explains Statement-I

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📊 Final Assessment

Statement	Status
Troposphere thicker at equator	✅ Correct
Strong convection at equator	✅ Correct
Explanation relationship	✅ Yes

👉 Correct answer: (a)

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❌ UPSC Elimination Logic

• UPSC checks:
  • Whether aspirants know latitudinal variation of atmospheric layers
  • Whether they understand cause–effect relationships
• Mere correctness of both statements is insufficient
• Explanatory linkage is the key

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🧩 Memory Hook

“Hot air rises higher — so the equator wears a thicker sky.”

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🧠 Prelims Strategy Insight

For atmosphere-related assertion–reason questions:

• Always ask:
  • Why does thickness vary?
• Convection is the master mechanism in tropical regions

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🧭 IAS Monk Whisper

Where heat rises freely, the sky stretches higher.