Q71 (IAS/2004) Geography › World Physical Geography › Atmospheric structure Answer Verified

Assertion (A) : The thickness of the atmosphere is maximum over the Equator. Reason (R) : High insolation and strong convection currents occur over the Equator.

Both A and R are individually true and R is the correct explanation of A

Both A and R are individually true but R is not the correct explanation of A

A is true but R is false

A is false but R is true

Result

Your answer: — · Correct: A

Explanation

Both Assertion and Reason are true, and Reason correctly explains the Assertion. Observations show the troposphere is ~18 km high at the equator and only about 8 km at the poles; thus tropospheric thickness is maximum over the equator [1]. This larger thickness is attributable to intense solar heating in the tropical belt which warms the column, producing strong convectional updrafts that transport heat and moist air to much greater heights; textbooks explicitly note heat is carried to great heights by strong convectional currents at the equator, raising the tropopause altitude [2]. The Inter-Tropical Convergence Zone (ITCZ) exemplifies this process: maximal insolation drives convergence and deep convection, lifting the tropospheric top over the equator [3].

Sources

[1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 274
[2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
[3] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 9: Atmospheric Circulation and Weather Systems > General circulation of the atmosphere > p. 80

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Assertion (A) : The thickness of the atmosphere is maximum over the Equator. Reason (R) : High insolation and strong convection currents occur over the Equator.

Explanation

SIMILAR QUESTIONS

Assertion (A): The salinity of oceans is relatively higher near the equator than at other regions. Reason (R): Equator region has heavy rainfall, high relative humidity and calm air.

Assertion (A) : Areas lying within five to eight degrees latitude on either side of the equator receive rainfall throughout the year. Reason (R) : High temperatures and high humidity cause convectional rain to fall mostly in the afternoons near the equator.

Assertion (A) : The Equatorial regions bulge outwards by about 21 kilometre compared to Poles. Reason (R) : Earth’s slow rotation reduces the effect of gravity around the Equator.

Assertion (A) : Areas near the equator receive rainfall throughout the year. Reason (R) : High temperatures and high humidity cause convectional rain in most afternoons near the equator. In the context of the above two statements, which one of the following is correct ?