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NEXUS / 2024 / GS1
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UPSC 2024: Nexus 01—10

Atmospheric Thermodynamics, Volcanic Geochemistry & Fluvial Confluences. [Set A]

Question 01

Atmospheric Heat Budget

Consider the following statements:

Statement-I:

The atmosphere is heated more by incoming solar radiation than by terrestrial radiation.

Statement-II:

Carbon dioxide and other greenhouse gases in the atmosphere are good absorbers of long wave radiation.

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

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

The Core Concept: The atmosphere is largely transparent to incoming shortwave solar radiation (insolation). Once solar energy reaches the Earth's surface, the land and oceans absorb it and radiate it back upward as longwave terrestrial radiation. Greenhouse gases like carbon dioxide, water vapor, and methane are exceptional absorbers of this longwave energy (Statement-II is true). Consequently, the atmosphere is heated primarily from below by terrestrial radiation, not directly by incoming solar radiation (Statement-I is false).

Tethered to: REALM 65: Heat Balance & Earth's Budget

Insolation GHG Absorption Layer (CO₂) Earth Surface Longwave IR Heated from Below, Not Insolation!
Pole (8 km) Equator (18 km) Pole (8 km) Tropopause Boundary Intense Convection

Question 02

Atmospheric Structure

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?

Official Verdict: (a) Both Statement-I and Statement-II are correct and Statement-II explains Statement-I

The Core Concept: The troposphere extends up to approximately 18 km at the equator, but only about 8 km at the poles (Statement-I is true). Because solar insolation is strongest and most concentrated at the equator, powerful convectional updrafts transport heated air parcels to towering altitudes, physically stretching and pushing the tropopause higher (Statement-II is true and provides the causal explanation). Additionally, strong centrifugal force at the equator aids in ballooning the atmospheric column.

Tethered to: REALM 63: Structure of Atmosphere

Question 03

Volcanology & Geochemistry

Consider the following:

  1. Pyroclastic debris
  2. Ash and dust
  3. Nitrogen compounds
  4. Sulphur compounds

How many of the above are products of volcanic eruptions?

Official Verdict: (d) All four

The Core Concept: Volcanic eruptions expel solids, liquids, and volcanic gases. Solid ejecta include pyroclastic debris (blocks, bombs, lapilli) and fine ash and dust. Gaseous emissions are dominated by water vapor, carbon dioxide, and sulphur compounds ($SO_2$, $H_2S$), accompanied by minor but notable amounts of nitrogen compounds ($N_2$, $NH_3$), carbon monoxide, and hydrogen halides. All four are textbook eruption byproducts.

Tethered to: REALM 31: Volcanoes

Ash & Dust (2) Pyroclasts (1) SO₂ / H₂S (4) N₂ / NH₃ (3) All 4 Ejection Products
North America N. Atlantic Ocean Eurasia Bends North (Warm Ocean) Bends South (Cold Land) Gulf Stream is WARM, not Cold!

Question 04

Climatology & Isothermal Mapping

Which of the following is/are correct inference/inferences from isothermal maps in the month of January?

  1. The isotherms deviate to the north over the ocean and to the south over the continent.
  2. The presence of cold ocean currents, Gulf Stream and North Atlantic Drift make the North Atlantic Ocean colder and the isotherms bend towards the north.

Select the answer using the code given below:

Official Verdict: (a) 1 only

The Core Concept: In January (Northern Hemisphere winter), continents cool much faster than oceans due to differential heat capacity. Isotherms bend equatorward (south) over the cold landmasses and poleward (north) over the warmer oceans (Statement 1 is true). Statement 2 is a factual contradiction: the Gulf Stream and North Atlantic Drift are warm ocean currents (not cold currents); their warm waters make the North Atlantic unusually mild, causing isotherms to curve northward.

Tethered to: REALM 66: Temperature Distribution

Question 05

Commercial Crop Geography

Which of the following countries are well known as the two largest cocoa producers in the world?

  • (a) Algeria and Morocco
  • (b) Botswana and Namibia
  • (c) Côte d'Ivoire and Ghana
  • (d) Madagascar and Mozambique

Official Verdict: (c) Côte d'Ivoire and Ghana

The Core Concept: West Africa produces nearly 60% of the world's cocoa supply. Côte d'Ivoire (Ivory Coast) is the global number-one producer by a wide margin, followed by neighboring Ghana in second place. Both countries sit along the humid equatorial Gulf of Guinea, offering the high rainfall, uniform warmth, and canopy shade required by Theobroma cacao trees.

Tethered to: REALM 36: Cocoa

Côte d'Ivoire Ghana >55% Global Cocoa Supply
Prayagraj Ganga → 1. Gomati 2. Ghaghara 3. Gandak 4. Kosi Sequence: Gomati → Ghaghara → Gandak → Kosi

Question 06

River Confluences of India

With reference to the Himalayan rivers joining the Ganga downstream of Prayagraj from West to East, which one of the following sequences is correct?

  • (a) Ghaghara - Gomati - Gandak - Kosi
  • (b) Gomati - Ghaghara - Gandak - Kosi
  • (c) Ghaghara - Gomati - Kosi - Gandak
  • (d) Gomati - Ghaghara - Kosi - Gandak

Official Verdict: (b) Gomati - Ghaghara - Gandak - Kosi

The Core Concept: Moving chronologically downstream of Prayagraj along the Ganga's left bank: the Gomati joins near Saidpur/Ghazipur; the Ghaghara (Karnali) joins near Chhapra (Bihar); the Gandak enters near Sonpur/Patna; and the Kosi joins further downstream near Kursela/Katihar. The precise West-to-East sequence is Gomati → Ghaghara → Gandak → Kosi.

Tethered to: REALM 17: Ganga River System

Question 07

Geomorphic Weathering Processes

Consider the following statements:

Statement-I:

Rainfall is one of the reasons for weathering of rocks.

Statement-II:

Rain water contains carbon dioxide in solution.

Statement-III:

Rain water contains atmospheric oxygen.

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

Official Verdict: (a) Both Statement-II and Statement-III are correct and both of them explain Statement-I

The Core Concept: Rainwater is a potent geochemical weathering agent. As raindrops fall, they dissolve atmospheric $CO_2$ to form weak carbonic acid ($H_2CO_3$), driving chemical carbonation that dissolves limestone and decomposes feldspar into clay (Statement-II explains Statement-I). Rainwater also carries dissolved atmospheric oxygen, driving oxidation reactions that rust and disintegrate iron-rich minerals in rocks (Statement-III explains Statement-I). Both chemical mechanisms explain why rainfall causes rock weathering.

Tethered to: REALM 40: Mechanical & Chemical (Weathering)

+CO₂ +O₂ Carbonic Acid (H₂CO₃) Oxidation (Fe₂O₃) Dual Chemical Weathering
NORTH SEA Norway (3) ✅ Germany (2) ✅ Finland (Baltic) Russia (Baltic/Barents) Only Two Countries Bordered

Question 08

European Littoral Geography

Consider the following countries:

  1. Finland
  2. Germany
  3. Norway
  4. Russia

How many of the above countries have a border with the North Sea?

Official Verdict: (b) Only two

The Core Concept: The North Sea is bordered by the UK, France, Belgium, the Netherlands, Germany (northwest coastline), Denmark, and Norway (southwest coast). Finland borders only the Gulf of Bothnia and the Gulf of Finland (Baltic Sea), having no access to the North Sea. Russia borders the Baltic Sea, Black Sea, and Arctic waters (Barents, Kara), but has zero coastline on the North Sea. Therefore, only two countries qualify.

Tethered to: REALM 61: Global Landform Atlas

Question 09

Indian Drainage & Waterfalls

Consider the following information:

  • 1. Dhuandhar: Malwa | Narmada
  • 2. Hundru: Chota Nagpur | Subarnarekha
  • 3. Gersoppa: Western Ghats | Netravati

In how many of the above rows is the given information correctly matched?

Official Verdict: (a) Only one

The Core Concept: Row 1 is mismatched: Dhuandhar Falls is on the Narmada River at Bhedaghat near Jabalpur (Mahakoshal / Narmada Valley region, not the Malwa plateau). Row 3 is mismatched: Gersoppa (Jog Falls) is located in the Western Ghats (Shivamogga, Karnataka) on the Sharavathi River, not the Netravati River. Row 2 is correctly matched: Hundru Falls drops 98 meters on the Subarnarekha River in the Ranchi district of the Chota Nagpur Plateau. Thus, only one row is correct.

Tethered to: REALM 45: Fluvial Erosional Landforms

Chota Nagpur Plateau Hundru Falls ✅ (Subarnarekha) Dhuandhar: Malwa ❌ (Mahakoshal) Gersoppa: Netravati ❌ (Sharavathi)
Appalachians ✅ (Fold • N. America) Andes ✅ (Fold • S. America) Vosges = Block in Europe (Not Fold / Central Asia) ❌ Alps = Young Fold (Not Block) ❌ Rows 3 & 4 Correct

Question 10

Orogeny & Global Ranges

Consider the following information:

  • 1. Central Asia: Vosges | Fold mountain
  • 2. Europe: Alps | Block mountain
  • 3. North America: Appalachians | Fold mountain
  • 4. South America: Andes | Fold mountain

In how many of the above rows is the given information correctly matched?

Official Verdict: (b) Only two

The Core Concept: Row 1 is completely wrong: the Vosges is a classic block mountain (horst) bordering the Rhine graben in eastern France (Europe), not a fold mountain in Central Asia. Row 2 is wrong: the Alps are the textbook young tertiary fold mountain chain of Europe, not a block mountain. Row 3 is correctly matched: the Appalachians are ancient Paleozoic fold mountains in North America. Row 4 is correctly matched: the Andes are the world's longest continental young fold mountain belt in South America. Exactly two rows are correct.

Tethered to: REALM 59: Mountains