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Q2 (IAS/2024) Geography › World Physical Geography › Atmospheric structure Official Key

Consider the following statements : Statement-I : Thickness of the troposphere at the equator is much greater as compared to 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 ?

Result
Your answer: —  ·  Correct: A
Explanation

The correct answer is option A because both statements are accurate and Statement-II correctly explains Statement-I.

The troposphere extends to about 8 km at the poles and approximately 18 km at the[1] equator[2], confirming that Statement-I is correct—the troposphere is indeed much thicker at the equator.

The thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents[2], which validates Statement-II and establishes the causal relationship. The greater thickness at the equator occurs because heated air rises to greater heights[1], demonstrating that the strong convectional currents mentioned in Statement-II directly cause the increased thickness described in Statement-I.

Therefore, both statements are factually correct, and Statement-II provides the scientific explanation for the phenomenon described in Statement-I, making option A the appropriate choice.

Sources
  1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 274
  2. [2] FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
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Don’t just practise – reverse-engineer the question. This panel shows where this PYQ came from (books / web), how the examiner broke it into hidden statements, and which nearby micro-concepts you were supposed to learn from it. Treat it like an autopsy of the question: what might have triggered it, which exact lines in the book matter, and what linked ideas you should carry forward to future questions.
Q. Consider the following statements : Statement-I : Thickness of the troposphere at the equator is much greater as compared to poles. St…
At a glance
Origin: From standard books Fairness: High fairness Books / CA: 10/10 · 0/10

This is the definition of a 'Sitter'. It is a verbatim copy-paste from NCERT Class XI Fundamentals of Physical Geography. If you missed this, you are neglecting the absolute basics in favor of complex materials. Stop chasing current affairs until your NCERT geography is bulletproof.

How this question is built

This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.

Statement 1
Is the thickness of the Earth's troposphere at the equator significantly greater than the troposphere thickness at the poles?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 274
Presence: 5/5
“• The altitude of the troposphere is 8 km at the poles and 18 km at the equator. The troposphere ends with tropopause (the topmost layer of the troposphere marked by constant temperatures). The thickness is greater at the equator because of the heated air that rises to greater heights.”
Why this source?
  • Gives numeric altitudes: 8 km at the poles and 18 km at the equator.
  • Explicitly attributes greater thickness at the equator to heated air rising to greater heights.
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
Presence: 5/5
“The atmosphere consists of different layers with varying density and temperature. Density is highest near the surface of the earth and decreases with increasing altitude. The column of atmosphere is divided into five different layers depending upon the temperature condition. They are: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The troposphere is the lowermost layer of the atmosphere. Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator. Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents.”
Why this source?
  • States average troposphere height (13 km) and specific extents: ~8 km near poles and ~18 km at equator.
  • Explains greatest thickness at equator results from heat-driven convection transporting air to greater heights.
Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Structure of the Atmosphere > p. 7
Presence: 5/5
“Near the equator, because of intense heating from below, the tropopause (upper limit of troposphere) occurs at 18 km; in the middle latitudes, it occurs at 13 km and at the North and South Poles it is only 8 km or less above Earth's surface. In the troposphere, temperatures decrease with increasing altitude at an average rate of 6.4°C per km which is known as the normal lapse rate. In terms of temperature the upper limit of troposphere is –57°C (Fig.1.2).• 2. Stratosphere and Ozonosphere: A layer of the Earth's atmosphere, above the troposphere, extends from about 20 to 50 kms above the sea level.”
Why this source?
  • Specifies tropopause altitude: 18 km at equator, 13 km in mid-latitudes, ~8 km at poles.
  • Links intense equatorial heating to a higher tropopause (thus thicker troposphere).
Statement 2
In the Earth's troposphere at the equator, are strong convectional currents transporting heat to much greater heights than at higher latitudes or the poles?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
Presence: 5/5
“The atmosphere consists of different layers with varying density and temperature. Density is highest near the surface of the earth and decreases with increasing altitude. The column of atmosphere is divided into five different layers depending upon the temperature condition. They are: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The troposphere is the lowermost layer of the atmosphere. Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator. Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents.”
Why this source?
  • Explicitly links greatest troposphere thickness at the equator to heat being transported to great heights by strong convectional currents.
  • Gives numerical bounds (about 18 km at equator vs 8 km at poles) that support a large latitudinal difference in vertical heat transport.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 274
Presence: 4/5
“• The altitude of the troposphere is 8 km at the poles and 18 km at the equator. The troposphere ends with tropopause (the topmost layer of the troposphere marked by constant temperatures). The thickness is greater at the equator because of the heated air that rises to greater heights.”
Why this source?
  • States troposphere altitude is ~18 km at the equator and ~8 km at the poles.
  • Attributes greater equatorial thickness to heated air rising to greater heights, consistent with stronger convective uplift.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Hadley Cell > p. 316
Presence: 4/5
“• The air at the equatorial low-pressure belt rises because of the convection currents. The air reaches the top of the troposphere up to an altitude of 14 km and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high.”
Why this source?
  • Describes air at the equator rising because of convection currents and reaching the top of the troposphere (around 14 km) before moving poleward.
  • Provides a dynamical mechanism (equatorial uplift feeding poleward flow) that supports greater vertical transport at low latitudes.
Statement 3
Do strong convectional currents and associated heat transport at the equator cause the troposphere to be thicker at the equator than at the poles?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
Presence: 5/5
“The atmosphere consists of different layers with varying density and temperature. Density is highest near the surface of the earth and decreases with increasing altitude. The column of atmosphere is divided into five different layers depending upon the temperature condition. They are: troposphere, stratosphere, mesosphere, thermosphere and exosphere. The troposphere is the lowermost layer of the atmosphere. Its average height is 13 km and extends roughly to a height of 8 km near the poles and about 18 km at the equator. Thickness of the troposphere is greatest at the equator because heat is transported to great heights by strong convectional currents.”
Why this source?
  • Explicitly links greatest troposphere thickness at the equator to heat transported to great heights by strong convectional currents.
  • Gives numerical contrast (about 18 km at equator vs ~8 km at poles) supporting the spatial pattern invoked by the statement.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 274
Presence: 5/5
“• The altitude of the troposphere is 8 km at the poles and 18 km at the equator. The troposphere ends with tropopause (the topmost layer of the troposphere marked by constant temperatures). The thickness is greater at the equator because of the heated air that rises to greater heights.”
Why this source?
  • Directly states the troposphere is thicker at the equator because heated air rises to greater heights.
  • Provides the same equator-vs-pole height contrast that the statement asks about.
Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Hadley Cell > p. 316
Presence: 4/5
“• The air at the equatorial low-pressure belt rises because of the convection currents. The air reaches the top of the troposphere up to an altitude of 14 km and moves towards the poles. This causes accumulation of air at about 30° N and S. Part of the accumulated air sinks to the ground and forms a subtropical high.”
Why this source?
  • Describes equatorial air rising due to convection and reaching the upper troposphere before moving poleward, explaining the mechanism that elevates tropospheric top at low latitudes.
  • Connects convective ascent at the equator to broader circulation (Hadley cell) that affects tropospheric structure.
Pattern takeaway: The examiner is returning to the classic 'Assertion-Reasoning' format by lifting causal statements directly from standard textbooks. Do not just memorize facts (heights); memorize the *mechanism* (convection) that causes the fact.
How you should have studied
  1. [THE VERDICT]: Absolute Sitter. Direct verbatim lift from NCERT Class XI Fundamentals of Physical Geography, Chapter 7 (Page 65).
  2. [THE CONCEPTUAL TRIGGER]: Vertical Structure of the Atmosphere & Heat Transfer Mechanisms (Convection vs. Advection).
  3. [THE HORIZONTAL EXPANSION]: Memorize the layer fingerprints: 1) Troposphere (8km Poles/18km Equator, Normal Lapse Rate 6.5°C/km). 2) Stratosphere (Ozone 15-35km, Temp Inversion, Mother of Pearl clouds). 3) Mesosphere (Coldest layer -100°C, Meteors burn). 4) Thermosphere (Ionosphere D/E/F layers, ISS orbit).
  4. [THE STRATEGIC METACOGNITION]: UPSC loves converting NCERT 'explanatory sentences' into Statement-I/Statement-II questions. Whenever you see the word 'because' or 'due to' in NCERT (e.g., 'Thickness is greatest... because heat is transported...'), highlight it as a potential Assertion-Reasoning question.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Latitudinal variation of troposphere thickness
💡 The insight

Troposphere altitude varies by latitude, being much greater at the equator (~18 km) than at the poles (~8 km).

High-yield for physical geography and atmosphere questions; connects to climate zonation, vertical structure of atmosphere, and interpretation of figures/diagrams. Mastering this helps answer questions on atmospheric layers, tropopause altitude, and latitude-linked climate differences.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 274
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
🔗 Anchor: "Is the thickness of the Earth's troposphere at the equator significantly greater..."
📌 Adjacent topic to master
S1
👉 Tropopause altitude and lapse rate
💡 The insight

Tropopause height and the normal lapse rate determine the vertical extent and thermal structure of the troposphere.

Important for questions on temperature profiles, weather/meteorology, and comparisons between latitudes; links to topics like convection, jet streams, and tropopause-related phenomena. Understanding lapse rate aids in explaining why the troposphere ends at different heights.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 275
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Structure of the Atmosphere > p. 7
🔗 Anchor: "Is the thickness of the Earth's troposphere at the equator significantly greater..."
📌 Adjacent topic to master
S1
👉 Convection and equatorial heating
💡 The insight

Stronger equatorial heating drives stronger convection, which lifts air higher and produces a thicker troposphere at low latitudes.

Crucial for explaining mechanisms behind latitudinal differences in atmospheric structure and for questions on atmospheric circulation, jet streams, and weather patterns. This concept connects thermodynamics of air parcels to large-scale circulation and pressure belts.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 274
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 27: Jet streams > Why Do Polar Jets and Subtropical Jets Flow At Different Altitudes? > p. 385
🔗 Anchor: "Is the thickness of the Earth's troposphere at the equator significantly greater..."
📌 Adjacent topic to master
S2
👉 Latitudinal variation in troposphere thickness
💡 The insight

Troposphere depth increases toward the equator (≈18 km) and decreases toward the poles (≈8 km), reflecting stronger vertical heating at low latitudes.

High-yield for physical geography questions on atmospheric structure and climate zones; connects to lapse rate, tropopause height, and regional weather patterns. Mastery enables clear answers on why convection and weather phenomena vary with latitude.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 274
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
  • Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 1: BASIC CONCEPTS OF ENVIRONMENT AND ECOLOGY > Structure of the Atmosphere > p. 7
🔗 Anchor: "In the Earth's troposphere at the equator, are strong convectional currents tran..."
📌 Adjacent topic to master
S2
👉 Convection as vertical heat transport in the troposphere
💡 The insight

Convection in the troposphere is the primary process moving heat upward; stronger convection at the equator carries heat to much greater heights.

Key for explaining temperature profiles, cloud formation, and why the troposphere is the active weather layer; links to diurnal heating, lapse rate, and meteorological processes frequently asked in UPSC mains and prelims.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > HEATING AND COOLING OF ATMOSPHERE > p. 68
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 20: Earths Atmosphere > Troposphere (0 to 12 km) > p. 275
🔗 Anchor: "In the Earth's troposphere at the equator, are strong convectional currents tran..."
📌 Adjacent topic to master
S2
👉 Equatorial uplift and Hadley cell transport
💡 The insight

Air rises strongly near the equator and then moves poleward aloft, forming part of the Hadley cell that redistributes heat from low to subtropical latitudes.

Essential for questions on general circulation, precipitation belts, and subtropical highs; understanding this enables explanation of tropical rainfall patterns, trade winds, and global heat redistribution.

📚 Reading List :
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 23: Pressure Systems and Wind System > Hadley Cell > p. 316
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 9: Atmospheric Circulation and Weather Systems > General circulation of the atmosphere > p. 80
  • Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 21: Horizontal Distribution of Temperature > Explanation: > p. 293
🔗 Anchor: "In the Earth's troposphere at the equator, are strong convectional currents tran..."
📌 Adjacent topic to master
S3
👉 Convectional vertical heat transport in the troposphere
💡 The insight

Strong convection at low latitudes drives upward heat transport that raises the top of the troposphere.

High-yield for atmospheric dynamics questions: explains why tropospheric processes concentrate weather and why tropopause height varies. Links to topics on lapse rate, weather systems, and energy transfer.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 7: Composition and Structure of Atmosphere > STRUCTURE OF THE ATMOSPHERE > p. 65
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 8: Solar Radiation, Heat Balance and Temperature > HEATING AND COOLING OF ATMOSPHERE > p. 68
🔗 Anchor: "Do strong convectional currents and associated heat transport at the equator cau..."
🌑 The Hidden Trap

The 'Tropopause Break'. The tropopause is not a continuous layer; it breaks at the latitudes where Jet Streams occur (Subtropical and Polar Jets). This break allows stratospheric ozone to sometimes leak into the troposphere.

⚡ Elimination Cheat Code

Apply 'Kitchen Physics'. Hot air expands and rises (Convection). Cold air contracts and sinks. Equator = Hot = Air rises high = Thicker layer. Poles = Cold = Air compresses = Thinner layer. Since Statement II describes the *mechanism* of heat rising (convection), it must be the correct explanation for Statement I.

🔗 Mains Connection

Mains GS-3 (Environment/Disaster Mgmt): A warming climate expands the troposphere (tropopause rising). This alters the 'service ceiling' for aviation and intensifies convective storms (Cloudbursts), linking basic physics to Disaster Management.

✓ Thank you! We'll review this.

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