निम्नलिखित कथनों पर विचार कीजिए : कथन I. शैलों पर जल के प्रभाव के संदर्भ में, चॉक एक अत्यंत पारगम्य शैल के रूप में ज्ञात है, जबकि मृत्तिका एक नितांत अपारगम्य या न्यूनतम पारगम्य शैल के रूप में ज्ञात है। कथन II. चॉक सरंध्र होता है, अतः जल अवशोषित कर सकता है। कथन III. मृत्तिका बिल्कुल ही सरंध्र नहीं है। उपर्युक्त कथनों के संदर्भ में, निम्नलिखित में से कौन-सा एक सही है?

(a) कथन II और कथन III दोनों सही हैं तथा वे दोनों कथन I की व्याख्या करते हैं

(d) न तो कथन II और न ही कथन III सही है

निम्नलिखित कथनों पर विचार कीजिए : कथन I. वैज्ञानिक अध्ययन यह सुझाते हैं कि पृथ्वी के घूर्णन और अक्ष में परिवर्तन हो रहा है। कथन II. सौर संस्फुरों (फ्लेयर्स) और उससे संबद्ध किरीटी द्रव्यमान निष्कासनों ने पृथ्वी के सबसे बाहरी वायुमंडल पर विशाल ऊर्जा-राशि की बौछार कर दी है। कथन III. जैसे-जैसे पृथ्वी का ध्रुवीय हिम पिघलता है, जल की प्रवृत्ति विषुवत्-वृत्त की ओर जाने की होती है। उपर्युक्त कथनों के बारे में, निम्नलिखित में से कौन-सा एक सही है?

(a) कथन II और कथन III दोनों सही हैं तथा वे दोनों कथन I की व्याख्या करते हैं

(d) न तो कथन II और न ही कथन III सही है

निम्नलिखित कथनों पर विचार कीजिए : कथन-I. चट्टानों के अपक्षय के कारणों में से एक कारण वर्षा है । कथन-II. वर्षा जल में घोल के रूप में कार्बन डाइऑक्साइड विद्यमान होता है । कथन-III. वर्षा जल में वायुमंडलीय ऑक्सीजन विद्यमान होता है । उपर्युक्त कथनों के संबंध में, निम्नलिखित में से कौन-सा सही है ?

(b) कथन-II और कथन-III दोनों सही हैं, किंतु उनमें से केवल एक, कथन-I की व्याख्या करता है

(c) कथन-II और कथन-III में से केवल एक सही है और वह कथन-I की व्याख्या करता है

(d) न तो कथन-II, न ही कथन-III सही है

निम्नलिखित युग्मों पर विचार कीजिए : 1. सेफीड — अंतरिक्ष में धूल और गैस के विशाल बादल 2. नीहारिकाएँ — तारे जो आवर्ती रूप से जलते-बुझते हैं 3. पल्सर — न्यूट्रॉन तारे जो तब बनते हैं जब विशाल तारों का ईंधन खत्म हो जाता है और उनका निपात हो जाता है उपर्युक्त युग्मों में से कितने सही सुमेलित हैं?

(d) कोई भी नहीं

निम्नलिखित कथनों पर विचार कीजिए : कथन–I. उष्णकटिबंधीय वर्षावनों की मृदा पोषक तत्त्वों से भरपूर होती है। कथन–II. उष्णकटिबंधीय वर्षावनों के उच्च ताप और आर्द्रता के कारण मृदा में विद्यमान मृत जैव पदार्थ का द्रुत अपघटन होता है। उपर्युक्त कथनों के बारे में, निम्नलिखित में से कौन-सा एक सही है?

(a) कथन–I और कथन–II दोनों सही हैं तथा कथन–II, कथन–I की सही व्याख्या है

(b) कथन–I और कथन–II दोनों सही हैं तथा कथन–II, कथन–I की सही व्याख्या नहीं है

(c) कथन–I सही है किन्तु कथन–II गलत है

निम्नलिखित कथनों पर विचार कीजिए : 1. भूकम्प-लेखी (सीस्मोग्राफ) में S तरंगों से पूर्व P तरंगें अभिलिखित की जाती हैं। 2. P तरंगों में, अलग-अलग कण तरंग प्रसार की दिशा में आगे-पीछे कंपन करते हैं, जबकि S तरंगों में कण तरंग प्रसार की दिशा के समकोणीय ऊपर-नीचे कंपन करते हैं। उपर्युक्त कथनों में से कौन-सा/से सही है/हैं?

(d) न तो 1 और न ही 2

पृथ्वी ग्रह पर जल के संदर्भ में, निम्नलिखित कथनों पर विचार कीजिए : 1. नदियों और झीलों में जल की मात्रा, भू-जल की मात्रा से अधिक है। 2. ध्रुवीय हिमच्छद और हिमनदों में जल की मात्रा, भू-जल की मात्रा से अधिक है। उपर्युक्त कथनों में से कौन-सा/कौन-से सही है/हैं?

(d) न तो 1 और न ही 2

प्रश्न यूपीएससी के हिंदी प्रश्नपत्र से · व्याख्या अभी अंग्रेज़ी में

English हिंदी

Geography

Prelims · Geography · 19 questions

Earth, landforms & geomorphology

Every UPSC Prelims question on this topic, 2016–2026, newest first. Tap an option to check yourself; the answer and explanation open below it.

Asked in 6 of 11 years · most in 2024 (4)

Practising Geography? Take it as timed sets of 25 →

UPSC syllabus: “Indian and World Geography-Physical, Social, Economic Geography of India and the World.” Sub-topics in the detailed syllabus →

Prelims 2025 · Q22

X-Ray · Core #4 Easy

निम्नलिखित देशों पर विचार कीजिए :

I.बोलीविया
II.ब्राज़ील
III.कोलंबिया
IV.इक्वाडोर
V.पराग्वे
VI.वेनेजुएला

एन्डीज़ पर्वत-शृंखला उपर्युक्त देशों में कितनों में से होकर गुजरती है?

Read this question in English

Consider the following countries:

I. Bolivia

II. Brazil

III. Colombia

IV. Ecuador

V. Paraguay

VI. Venezuela

Andes mountains pass through how many of the above countries?

(a) Only two · (b) Only three · (c) Only four · (d) Only five

उत्तर और व्याख्या · explanation in English

Answer: (c) केवल चार

The Andes run along South America's western side through seven countries: Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile and Argentina. From the list, Bolivia, Colombia, Ecuador and Venezuela lie on the chain; Brazil and Paraguay lie wholly to the east.

✓ I Bolivia is one of the countries with large portions of the Tropical Andes.
✗ II Brazil is not one of the Andean countries; it lies east of the chain, in the Amazon basin and the Brazilian Highlands.
✓ III Colombia includes large portions of the Tropical Andes; the northern Andes split into several ranges (cordilleras) there.
✓ IV Ecuador includes large portions of the Tropical Andes; its Andean cordilleras carry volcanoes such as Chimborazo and Cotopaxi.
✗ V Paraguay is a landlocked lowland country of the Paraná–Paraguay basin and the Gran Chaco, with no Andean ranges.
✓ VI The Andes hotspot extends from western Venezuela, where the northernmost Andes (the Venezuelan or Caribbean cordillera) lie.

Remember · Andes countries (7), north to south: Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile, Argentina. Not Brazil, Paraguay, Uruguay or the Guianas.

Sources

Critical Ecosystem Partnership Fund (CEPF; World Bank, GEF, EU, AFD, Government of Japan and others), Tropical Andes Biodiversity Hotspot ↗ · reference work “the Tropical Andes Biodiversity Hotspot extends from western Venezuela to northern Chile and Argentina, and includes large portions of Colombia, Ecuador, Peru and Bolivia.”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2025 · Q25

Easy

निम्नलिखित में से कौन-से महाद्वीपीय विस्थापन की घटना के साक्ष्य हैं?

I.ब्राज़ील तट की प्राचीन शैलों की मेखला, पश्चिमी अफ्रीका तट की प्राचीन शैलों की मेखला से मिलती है।
II.घाना के स्वर्ण-निक्षेप ब्राज़ील पठार से व्युत्पन्न होते हैं, जब ये दोनों महाद्वीप अगल-बगल अवस्थित होते हैं।
III.यह ज्ञात है कि भारत के गोंडवाना अवसाद तंत्र के प्रतिरूप दक्षिणी गोलार्ध के छः विभिन्न भूखंडों में मिलते हैं।

नीचे दिए गए कूट का प्रयोग कर सही उत्तर चुनिए।

Read this question in English

Which of the following are the evidences of the phenomenon of continental drift?

I. The belt of ancient rocks from Brazil coast matches with those from Western Africa.

II. The gold deposits of Ghana are derived from the Brazil plateau when the two continents lay side by side.

III. The Gondwana system of sediments from India is known to have its counterparts in six different landmasses of the Southern Hemisphere.

Select the correct answer using the code given below.

(a) I and III only · (b) I and II only · (c) I, II and III · (d) II and III only

उत्तर और व्याख्या · explanation in English

Answer: (c) I, II और III

All three are classic evidences Wegener's supporters used to show the southern continents were once joined: matching ancient rock belts on either side of the South Atlantic, placer gold in Ghana whose source veins lie in Brazil, and the same glacial Gondwana sediments in India and five other southern landmasses.

✓ I Rocks about 2,000 million years old on the Brazilian coast match those of western Africa, and the oldest marine deposits along both coasts are only Jurassic, so the ocean between them is young.
✓ II Ghana has rich placer gold but no source rock; the gold-bearing veins are in Brazil, so the deposits must have come from the Brazil plateau when the continents touched.
✓ III The Gondwana sediments of India, with thick glacial tillite at the base, are matched in Africa, the Falkland Islands, Madagascar, Antarctica and Australia.

Remember · Continental drift evidence: jig-saw fit, matching rocks across the Atlantic (Brazil–West Africa), Ghana's placer gold from Brazil, Gondwana tillite in six southern landmasses, fossils like Mesosaurus and Glossopteris.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 4 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 4 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 4 (practise this chapter)

Sources

NCERT Class 11 · Fundamentals of Physical Geography, Chapter 4 “The belt of ancient rocks of 2,000 million years from Brazil coast matches with those from western Africa.”
NCERT Class 11 · Fundamentals of Physical Geography, Chapter 4 “The gold bearing veins are in Brazil and it is obvious that the gold deposits of the Ghana are derived from the Brazil plateau when the two continents lay side by side.”
NCERT Class 11 · Fundamentals of Physical Geography, Chapter 4 “The Gondawana system of sediments from India is known to have its counterparts in six different landmasses of the Southern Hemisphere.”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2025 · Q28

Medium

निम्नलिखित कथनों पर विचार कीजिए :

कथन I: शैलों पर जल के प्रभाव के संदर्भ में, चॉक एक अत्यंत पारगम्य शैल के रूप में ज्ञात है, जबकि मृत्तिका एक नितांत अपारगम्य या न्यूनतम पारगम्य शैल के रूप में ज्ञात है।
कथन II: चॉक सरंध्र होता है, अतः जल अवशोषित कर सकता है।
कथन III: मृत्तिका बिल्कुल ही सरंध्र नहीं है।

उपर्युक्त कथनों के संदर्भ में, निम्नलिखित में से कौन-सा एक सही है?

Read this question in English

Consider the following statements:

Statement I. In the context of effect of water on rocks, chalk is known as a very permeable rock whereas clay is known as quite an impermeable or least permeable rock.

Statement II. Chalk is porous and hence can absorb water.

Statement III. Clay is not at all porous.

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

(a) Both Statement II and Statement III are correct and both of them explain Statement I · (b) Both Statement II and Statement III are correct but only one of them explains Statement I · (c) Only one of the Statements II and III is correct and that explains Statement I · (d) Neither Statement II nor Statement III is correct

उत्तर और व्याख्या · explanation in English

Answer: (c) कथन II और कथन III में से केवल एक सही है तथा वह कथन I की व्याख्या करता है

Porosity is how much empty space a rock holds; permeability is how easily water passes through it. Chalk is a soft limestone, and limestone is porous and gives up its pore water freely, which explains Statement I. Clay is actually highly porous (USGS puts it at about 50%), but its pores are so tiny that water barely moves, so Statement III ('not at all porous') is wrong.

✓ Statement I Chalk is a variety of limestone (Britannica), and USGS shows limestone yielding most of its pore water freely, while groundwater moves very slowly through relatively impermeable materials such as clay and shale.
✓ Statement II Chalk, as a limestone, is porous: USGS lists limestone at 20% porosity with 18% specific yield, so it takes up and releases water readily. That is why chalk is permeable, so II explains I.
✗ Statement III Clay is not free of pores: USGS lists its porosity at 50%, but only 2% of that drains freely because the pores are tiny. Britannica notes that permeability falls as the average pore size becomes smaller.

Remember · Porosity = pore space; permeability = ease of water flow. Chalk (limestone): porous and permeable. Clay: highly porous but nearly impermeable because its pores are minute.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter)

Sources

U.S. Geological Survey, Water Science School: Aquifers and Groundwater (copy of the USGS page) ↗ “Groundwater moves very slowly through relatively impermeable materials such as clay and shale.”
Encyclopaedia Britannica: Permeability (geology) ↗ · reference work “The porosity of a soil horizon increases as its texture becomes finer, whereas the permeability decreases as the average pore size becomes smaller.”
NCERT Class 11 · Fundamentals of Physical Geography, Chapter 5 “If the rocks are permeable and soluble and water is available only then karst topography develops.”
U.S. Geological Survey, Water-Supply Paper 2220: Basic Ground-Water Hydrology (Heath, 1983): porosity, specific yield and specific retention ↗ “Clay ----------------------- 50 2 48 Sand ---------------------- 25 22 3 Gravel --------------------- 20 19 1 Limestone ------------------ 20 18 2”
Encyclopaedia Britannica: Chalk ↗ · reference work “chalk , soft, fine-grained, easily pulverized, white-to-grayish variety of limestone .”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink ·

Prelims 2025 · Q33

Hard

निम्नलिखित कथनों पर विचार कीजिए :

कथन I: वैज्ञानिक अध्ययन यह सुझाते हैं कि पृथ्वी के घूर्णन और अक्ष में परिवर्तन हो रहा है।
कथन II: सौर संस्फुरों (फ्लेयर्स) और उससे संबद्ध किरीटी द्रव्यमान निष्कासनों ने पृथ्वी के सबसे बाहरी वायुमंडल पर विशाल ऊर्जा-राशि की बौछार कर दी है।
कथन III: जैसे-जैसे पृथ्वी का ध्रुवीय हिम पिघलता है, जल की प्रवृत्ति विषुवत्-वृत्त की ओर जाने की होती है।

उपर्युक्त कथनों के बारे में, निम्नलिखित में से कौन-सा एक सही है?

Read this question in English

Consider the following statements:

Statement I. Scientific studies suggest that a shift is taking place in the Earth’s rotation and axis.

Statement II. Solar flares and associated coronal mass ejections bombarded the Earth’s outermost atmosphere with tremendous amount of energy.

Statement III. As the Earth’s polar ice melts, the water tends to move towards the equator.

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

उत्तर और व्याख्या · explanation in English

Answer: (b) कथन II और कथन III दोनों सही हैं किन्तु उनमें से केवल एक, कथन I की व्याख्या करता है

Both Statement II and Statement III are true, but only Statement III explains Statement I. Melting polar ice moves mass from the poles towards the equatorial ocean, and such shifts of mass change Earth's rotation and axis. A solar storm heats the upper atmosphere but does not shift the planet's mass, so it cannot explain a change in rotation or axis.

✓ I NASA-funded studies show Earth's spin axis drifts (polar motion) and its rotation slows, as mass is redistributed on and within the planet.
✓ II Solar flares and coronal mass ejections do hit Earth's upper atmosphere with charged particles and energy and can heat it. This is a space-weather effect and does not move Earth's mass, so it does not explain Statement I.
✓ III Faster melting of ice sheets has shifted mass from the poles towards the equatorial ocean. This redistribution of mass is the cause of the change in rotation and axis, so it explains Statement I.

Remember · Ice melt shifts mass from the poles to the equatorial oceans, changing Earth's spin axis and lengthening the day; solar storms only affect the upper atmosphere.

Sources

NASA-Funded Studies Explain How Climate Is Changing Earth’s Rotation (NASA, Internet Archive copy) ↗ “In recent decades, the faster melting of ice sheets has shifted mass from the poles toward the equatorial ocean. … These resulting shifts in mass cause the planet to wobble as it spins and its axis to shift location — a phenomenon called polar motion.”
Solar Storms and Flares (NASA Science, Internet Archive copy) ↗ “temporarily heat up Earth’s upper atmosphere, causing it to swell and increase drag on some Earth-orbiting satellites, which makes the satellites slow down and lose altitude.”

Question and answer: UPSC's official GS Paper I (2025, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2024 · Q3

Easy

निम्नलिखित पर विचार कीजिए :

1.ज्वलखंडाश्मी (पाइरोक्लास्टी) मलबा
2.राख और धूल
3.नाइट्रोजन यौगिक
4.सल्फर यौगिक

उपर्युक्त में से कितने ज्वालामुखी उद्गारों के उत्पाद हैं ?

Read this question in English

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?

(a) Only one · (b) Only two · (c) Only three · (d) All four

उत्तर और व्याख्या · explanation in English

Answer: (d) सभी चार

An eruption brings out solid, liquid and gaseous material: lava, fragments of rock, fine ash and dust, and gases. The gases include nitrogen and sulphur compounds, so all four listed items are volcanic products.

✓ 1. Pyroclastic debris — rock fragments blown out by the explosion — is thrown out along with lava flows and volcanic bombs.
✓ 2. Fine ash and dust are ejected in eruptions and can spread over large areas.
✓ 3. Nitrogen compounds are among the gases released by volcanoes.
✓ 4. Sulphur compounds are also released as volcanic gases, alongside small amounts of chlorine, hydrogen and argon.

Remember · Volcanic output: lava, pyroclastic debris, volcanic bombs, ash and dust, and gases (nitrogen and sulphur compounds, minor chlorine, hydrogen, argon).

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 3 (practise this chapter)

Sources

NCERT Class 11 · Fundamentals of Physical Geography, Chapter 3 “The material that reaches the ground includes lava flows, pyroclastic debris, volcanic bombs, ash and dust and gases such as nitrogen compounds, sulphur compounds and minor amounts of chlorene, hydrogen and argon.”

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2024 · Q7

Medium

निम्नलिखित कथनों पर विचार कीजिए :

कथन-I: चट्टानों के अपक्षय के कारणों में से एक कारण वर्षा है ।
कथन-II: वर्षा जल में घोल के रूप में कार्बन डाइऑक्साइड विद्यमान होता है ।
कथन-III: वर्षा जल में वायुमंडलीय ऑक्सीजन विद्यमान होता है ।

उपर्युक्त कथनों के संबंध में, निम्नलिखित में से कौन-सा सही है ?

Read this question in English

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?

(a) Both Statement-II and Statement-III are correct and both of them explain Statement-I · (b) Both Statement-II and Statement-III are correct, but only one of them explains Statement-I · (c) Only one of the Statements II and III is correct and that explains Statement-I · (d) Neither Statement-II nor Statement-III is correct

उत्तर और व्याख्या · explanation in English

Answer: (a) कथन-II और कथन-III दोनों सही हैं तथा दोनों, कथन-I की व्याख्या करते हैं

Chemical weathering works through water, oxygen and carbon dioxide. Falling rain dissolves both gases from the air: the dissolved carbon dioxide forms a weak acid that attacks rocks (carbonation), and the dissolved oxygen oxidises minerals such as iron. So both II and III are true and each explains why rain weathers rock.

✓ Statement-I Rainwater drives chemical weathering processes such as solution, carbonation, hydration and oxidation.
✓ Statement-II Rain dissolves atmospheric carbon dioxide and becomes weakly acidic; this acid dissolves minerals, especially in limestone (carbonation). It explains Statement-I.
✓ Statement-III Rain also carries dissolved oxygen, which oxidises iron-bearing minerals and weakens the rock. It too explains Statement-I.

Remember · Chemical weathering needs water plus air — oxygen (oxidation) and carbon dioxide (carbonation). Rainwater brings both.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter)

Sources

NCERT Class 11 · Fundamentals of Physical Geography, Chapter 5 “A group of weathering processes viz; solution, carbonation, hydration, oxidation and reduction act on the rocks to decompose, dissolve or reduce them to a fine clastic state through chemical reactions by oxygen, surface and/or soil water and other acids.”
NCERT Class 11 · Fundamentals of Physical Geography, Chapter 5 “Water and air (oxygen and carbon dioxide) along with heat must be present to speed up all chemical reactions.”

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2024 · Q10

Medium

निम्नलिखित सूचना पर विचार कीजिए :

	क्षेत्र	पर्वत शृंखला का नाम	पर्वत का प्रकार
1.	मध्य एशिया	वॉसजेस	वलित पर्वत
2.	यूरोप	आल्प्स	भ्रंशोत्थ (ब्लॉक) पर्वत
3.	उत्तर अमेरिका	अप्लेशियन	वलित पर्वत
4.	दक्षिण अमेरिका	एंडीज़	वलित पर्वत

उपर्युक्त सूचना में से कितनी पंक्तियाँ सही सुमेलित हैं ?

Read this question in English

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?

(a) Only one · (b) Only two · (c) Only three · (d) All four

उत्तर और व्याख्या · explanation in English

Answer: (b) केवल दो

Rows 3 and 4 are right: the Appalachians and the Andes are fold mountains raised where plates converged. Row 1 is wrong twice over — the Vosges are in Europe (France) and are a block mountain beside the Rhine rift valley; row 2 is wrong because the Alps are young fold mountains, not block mountains.

✗ 1. The Vosges are in north-eastern France, west of the Rhine Graben — a sunken block of crust. They are a classic block (horst) mountain of Europe, not a fold range of Central Asia.
✗ 2. The Alps belong to the young zone of continental collision that runs from the Himalayas to Europe; they are fold mountains, not block mountains.
✓ 3. The Appalachians formed in continental collisions 500–300 million years ago; their sedimentary layers were folded and faulted. They are old, worn-down fold mountains.
✓ 4. The Andes were raised as the oceanic Nazca Plate pushed under the South American Plate — a convergent-boundary fold range.

Remember · Fold: Himalayas, Alps, Andes, Rockies (young); Appalachians, Aravallis, Urals (old). Block: Vosges and Black Forest on either side of the Rhine rift valley.

Sources

NASA MODIS Image Gallery: The Vosges Mountains, the Black Forest, and the Rhine Valley ↗ “The Rhine River Valley in that area is known to geologists as the Rhine Graben. A graben is an elongated block of Earth’s crust that has sunk relative to the surrounding blocks.”
US National Park Service: Convergent Plate Boundaries — Collisional Mountain Ranges ↗ “The Appalachian Mountains formed during a collision of continents 500 to 300 million years ago. In their prime they probably had peaks as high as those in the modern zone of continental collision stretching from the Himalayas in Asia to the Alps in Europe.”
USGS: This Dynamic Earth — Understanding plate motions ↗ “In turn, the overriding South American Plate is being lifted up, creating the towering Andes mountains, the backbone of the continent.”

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2024 · Q15

Easy

प्रत्येक वर्ष 21 जून को, निम्नलिखित में से किस अक्षांश/किन अक्षांशों पर 12 घंटे से अधिक समय तक सूर्य का प्रकाश विद्यमान रहता है ?

1.भूमध्यरेखा (इक्वेटर)
2.कर्क रेखा
3.मकर रेखा
4.उत्तर ध्रुवीय (आर्कटिक) वृत्त

नीचे दिए गए कूट का प्रयोग कर सही उत्तर चुनिए :

Read this question in English

On June 21 every year, which of the following latitude(s) experience(s) a sunlight of more than 12 hours?

1. Equator

2. Tropic of Cancer

3. Tropic of Capricorn

4. Arctic Circle

Select the correct answer using the code given below:

(a) 1 only · (b) 2 only · (c) 3 and 4 · (d) 2 and 4

उत्तर और व्याख्या · explanation in English

Answer: (d) 2 और 4

21 June is the summer solstice of the northern hemisphere, when the North Pole is tilted towards the Sun. Every place north of the equator then gets more than 12 hours of daylight, the equator gets exactly 12, and the southern hemisphere gets less. So the Tropic of Cancer and the Arctic Circle qualify.

✗ 1. The equator has about 12 hours of daylight and 12 hours of darkness throughout the year, never more.
✓ 2. The Tropic of Cancer is in the northern hemisphere, where days are longer than 12 hours in June; on 21 June the Sun is overhead there at noon.
✗ 3. The Tropic of Capricorn is in the southern hemisphere, where June is winter and daylight is shorter than 12 hours.
✓ 4. On 21 June the Arctic Circle has its longest day — the Sun stays above the horizon for about 24 hours.

Remember · 21 June: longest day north of the equator (24-hour day at and beyond the Arctic Circle); equator always ~12 hours; southern hemisphere has short winter days.

📘 Read it in NCERT: Class 7 Curiosity, Ch 12 (practise this chapter) · Class 7 Curiosity, Ch 12 (practise this chapter) · Class 7 Curiosity, Ch 12 (practise this chapter)

Sources

NCERT Class 7 · Curiosity, Chapter 12 “Places in this hemisphere receive sunlight for more than 12 hours during the 24 hour rotation of the Earth. The North Pole receives sunlight for all 24 hours in June”
NCERT Class 7 · Curiosity, Chapter 12 “The seasons and length of daytime are reversed in the Southern Hemisphere as compared to the Northern Hemisphere. There, it is winter in June and summer in December”
NCERT Class 7 · Curiosity, Chapter 12 “On the equator, there is always 12 hours of sunlight and 12 hours of darkness.”

Question and answer: UPSC's official GS Paper I (2024, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2023 · Q5

X-Ray · Core #51 Medium

निम्नलिखित में से कौन-सा एक, समुद्र स्तर में पुनरावर्ती गिरावट का सर्वोत्तम उदाहरण है, जिससे वर्तमान समय की सुविस्तृत कच्छभूमि उत्पन्न हुई है?

Read this question in English

Which one of the following is the best example of repeated falls in sea level, giving rise to present-day extensive marshland?

(a) Bhitarkanika Mangroves · (b) Marakkanam Salt Pans · (c) Naupada Swamp · (d) Rann of Kutch

उत्तर और व्याख्या · explanation in English

Answer: (d) कच्छ का रण

The Rann of Kachchh was once a shallow part of the Arabian Sea. A geological shift closed off its connection with the sea, leaving a vast seasonal marshy salt desert that fills with water in the monsoon and dries into a white salt flat in summer.

✓ (d) The Rann was a shallow part of the Arabian Sea until a geological shift closed its connection with the sea; it is now a huge seasonal marshy salt desert in Gujarat, made up of the Great Rann and the Little Rann.
✗ (a) Bhitarkanika in Odisha is a mangrove forest. NCERT notes that mangroves grow along coasts in salt marshes, tidal creeks, mud flats and estuaries, so it is a coastal tidal wetland, not marshland left behind by a retreating sea.
✗ (b) Marakkanam in Tamil Nadu is known for its coastal salt pans, where salt is made from seawater; these are small human-made works, not a vast natural marshland.

Remember · Rann of Kutch: former shallow part of the Arabian Sea, cut off by a geological shift; now a seasonal marshy salt desert (Great Rann and Little Rann) in Gujarat.

📘 Read it in NCERT: Class 11 India: Physical Environment, Ch 5 (practise this chapter)

Sources

Encyclopaedia Britannica: Rann of Kachchh ↗ · reference work “The Rann was a once a shallow part of the Arabian Sea , until a geological shift closed off the connection with the sea. The region became a seasonal marshy salt desert over the years. … During the monsoons, the area fills with water, creating a wetland. In the summer, the water evaporates, leaving a white, salty land.”
NCERT Class 11 · India: Physical Environment, Chapter 5 “Mangroves grow along the coasts in the salt marshes, tidal creeks, mud flats and estuaries.”

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 1 Oct 2026 (how we verify). Permalink ·

Prelims 2023 · Q56

Medium

निम्नलिखित युग्मों पर विचार कीजिए :

	अंतरिक्ष में पिंड	वर्णन
1.	सेफीड	अंतरिक्ष में धूल और गैस के विशाल बादल
2.	नीहारिकाएँ	तारे जो आवर्ती रूप से जलते-बुझते हैं
3.	पल्सर	न्यूट्रॉन तारे जो तब बनते हैं जब विशाल तारों का ईंधन खत्म हो जाता है और उनका निपात हो जाता है

उपर्युक्त युग्मों में से कितने सही सुमेलित हैं?

Read this question in English

Consider the following pairs:

1. Cepheids — Giant clouds of dust and gas in space

2. Nebulae — Stars which brighten and dim periodically

3. Pulsars — Neutron stars that are formed when massive stars run out of fuel and collapse

How many of the above pairs are correctly matched?

(a) Only one · (b) Only two · (c) All three · (d) None

उत्तर और व्याख्या · explanation in English

Answer: (a) केवल एक

Only pair 3 is correctly matched. Pairs 1 and 2 have their descriptions swapped: Cepheids are stars whose brightness varies in a regular cycle, and nebulae are giant clouds of gas and dust. Pulsars are indeed neutron stars left when a massive star runs out of fuel and collapses.

✗ 1. Cepheids are pulsating variable stars, not clouds. Their regular changes in brightness are used to measure distances to galaxies.
✗ 2. A nebula is a very large cloud of gas (and dust), the place where stars form. It is not a star that brightens and dims.
✓ 3. A neutron star forms when a massive star runs out of fuel and its core collapses. Pulsars are neutron stars that spin fast and sweep a beam of radiation across space.

Remember · Cepheids are stars that brighten and dim in a regular cycle; nebulae are clouds of gas and dust; pulsars are spinning neutron stars.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 2 (practise this chapter)

Sources

NCERT Class 11 · Fundamentals of Physical Geography, Chapter 2 “A galaxy starts to form by accumulation of hydrogen gas in the form of a very large cloud called nebula.”
Cepheid Variables: Brightness Over Time (NASA Science, Hubble) ↗ “shows a class of pulsating star called a Cepheid Variable. Though rare, these stars are reliable distance indicators to galaxies.”
Neutron Stars (NASA Imagine the Universe) ↗ “Neutron stars are formed when a massive star runs out of fuel and collapses. The very central region of the star – the core – collapses, crushing together every proton and electron into a neutron.”

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2023 · Q63

Easy

निम्नलिखित कथनों पर विचार कीजिए :

कथन–I: उष्णकटिबंधीय वर्षावनों की मृदा पोषक तत्त्वों से भरपूर होती है।
कथन–II: उष्णकटिबंधीय वर्षावनों के उच्च ताप और आर्द्रता के कारण मृदा में विद्यमान मृत जैव पदार्थ का द्रुत अपघटन होता है।

उपर्युक्त कथनों के बारे में, निम्नलिखित में से कौन-सा एक सही है?

Read this question in English

Consider the following statements:

Statement-I. The soil in tropical rain forests is rich in nutrients.

Statement-II. The high temperature and moisture of tropical rain forests cause dead organic matter in the soil to decompose quickly.

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 is the correct explanation for Statement-I · (b) Both Statement-I and Statement-II are correct and Statement-II is not the correct explanation for Statement-I · (c) Statement-I is correct but Statement-II is incorrect · (d) Statement-I is incorrect but Statement-II is correct

उत्तर और व्याख्या · explanation in English

Answer: (d) कथन–I गलत है किन्तु कथन–II सही है

The soil of a tropical rain forest is poor, not rich, in nutrients. Heat and moisture make bacterial action intense, so dead plant matter is oxidised quickly and very little humus builds up in the soil; heavy rain also leaches nutrients out of tropical soils.

✗ Statement-I Fast decay leaves the soil with very low humus content, and heavy rain leaches away nutrients; lateritic soils of heavy-rain tropical areas are generally deficient in plant nutrients.
✓ Statement-II In humid tropical and equatorial climates bacterial growth and action is intense, so dead vegetation is rapidly oxidised. This is the reason the humus content of the soil stays low, not a sign of richness.

Remember · Fast decay plus heavy rain leave tropical rain forest soil low in humus and nutrients; in cold climates decay is slow, so humus and peat accumulate.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 5 (practise this chapter) · Class 10 Contemporary India – II, Ch 1 (practise this chapter)

Sources

NCERT Class 11 · Fundamentals of Physical Geography, Chapter 5 “In humid tropical and equatorial climates, bacterial growth and action is intense and dead vegetation is rapidly oxidised leaving very low humus content in the soil.”
NCERT Class 10 · Contemporary India – II, Chapter 1 “This soil is the result of intense leaching due to heavy rain. Lateritic soils are mostly deep to very deep, acidic (pH<6.0), generally deficient in plant nutrients”

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2023 · Q65

Easy

निम्नलिखित कथनों पर विचार कीजिए :

1.भूकम्प-लेखी (सीस्मोग्राफ) में S तरंगों से पूर्व P तरंगें अभिलिखित की जाती हैं।
2.P तरंगों में, अलग-अलग कण तरंग प्रसार की दिशा में आगे-पीछे कंपन करते हैं, जबकि S तरंगों में कण तरंग प्रसार की दिशा के समकोणीय ऊपर-नीचे कंपन करते हैं।

उपर्युक्त कथनों में से कौन-सा/से सही है/हैं?

Read this question in English

Consider the following statements:

1. In a seismograph, P waves are recorded earlier than S waves.

2. In P waves, the individual particles vibrate to and fro in the direction of wave propagation whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation.

Which of the statements given above is/are correct?

(a) 1 only · (b) 2 only · (c) Both 1 and 2 · (d) Neither 1 nor 2

उत्तर और व्याख्या · explanation in English

Answer: (c) 1 और 2 दोनों

Both statements are correct. P-waves travel faster, so a seismograph records them first, and they vibrate along the direction of travel. S-waves arrive later and vibrate at right angles to that direction.

✓ 1. P-waves are the primary waves: they move faster and are the first to reach the surface. S-waves, the secondary waves, arrive after a time lag, so they are recorded later.
✓ 2. P-waves vibrate parallel to the direction of the wave, pushing and squeezing the material to and fro. S-waves vibrate perpendicular to the wave direction in the vertical plane, so they create troughs and crests.

Remember · P-waves: primary, fastest, particles move to and fro along the path, pass through solids, liquids and gases. S-waves: secondary, slower, particles move up and down, only through solids.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 3 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 3 (practise this chapter)

Sources

NCERT Class 11 · Fundamentals of Physical Geography, Chapter 3 “P-waves move faster and are the first to arrive at the surface. These are also called 'primary waves'.”
NCERT Class 11 · Fundamentals of Physical Geography, Chapter 3 “The direction of vibrations of S-waves is perpendicular to the wave direction in the vertical plane. Hence, they create troughs and crests in the material through which they pass.”

Question and answer: UPSC's official GS Paper I (2023, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2022 · Q24

X-Ray · Core #52 Easy

दक्षिण भारत की गंडिकोटा घाटी (कैन्यन) निम्नलिखित नदियों में से किस एक से निर्मित हुई है ?

Read this question in English

Gandikota canyon of South India was created by which one of the following rivers?

(a) Cauvery · (b) Manjira · (c) Pennar · (d) Tungabhadra

उत्तर और व्याख्या · explanation in English

Answer: (c) पेन्नार

The Gandikota gorge in Kadapa district, Andhra Pradesh, is cut by the Pennar (Penna) river through the Erramala hills. The name itself joins the Telugu words for gorge ('gandi') and fort ('kota'), after the medieval fort perched above the canyon.

✓ (c) The Kadapa district administration describes the Penna river gorge, about 200 metres wide, flowing between the cliffs of the Erramala hills at Gandikota.
✗ (d) The Tungabhadra is a Krishna tributary flowing past Hampi in Karnataka; it does not flow through Kadapa district.
✗ (b) The Manjira is a tributary of the Godavari in Maharashtra, Karnataka and Telangana, far north of Gandikota.

Remember · Gandikota ('gorge fort'), Kadapa district, Andhra Pradesh: canyon of the Pennar/Penna river through the Erramala hills — often called India's Grand Canyon.

Sources

District YSR (Kadapa), Government of Andhra Pradesh: Gandikota ↗ “The viewpoint offers breathtaking panoramic views of the Penna river gorge flowing between the cliffs of Erramala hills, with a width of around 200 metres, forming one of the finest gorges in South India.”

Question and answer: UPSC's official GS Paper I (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2022 · Q29

Easy

उत्तरी गोलार्ध में, वर्ष का सबसे लंबा दिन आम तौर पर कब होता है ?

Read this question in English

In the northern hemisphere, the longest day of the year normally occurs in the:

(a) First half of the month of June · (b) Second half of the month of June · (c) First half of the month of July · (d) Second half of the month of July

उत्तर और व्याख्या · explanation in English

Answer: (b) जून महीने का दूसरा पखवाड़ा

The Northern Hemisphere's longest day is the summer solstice, around 21 June, when the North Pole is tilted most towards the Sun and the Sun is overhead at the Tropic of Cancer. 21 June falls in the second half of June.

✓ (b) The summer solstice falls on 20, 21 or 22 June; after it, days in the Northern Hemisphere grow shorter and nights longer.
✗ (a) Days are still lengthening through the first half of June; the maximum comes only at the solstice around 21 June.
✗ (c) July is often the hottest month because of the lag in heating, but day length is already decreasing by then.

Remember · Summer solstice ~21 June: Sun overhead at the Tropic of Cancer, longest day in the Northern Hemisphere; winter solstice ~22 December: shortest day.

📘 Read it in NCERT: Class 7 Curiosity, Ch 12 (practise this chapter)

Sources

NCERT Class 7 · Curiosity, Chapter 12 “In the Northern Hemisphere, the longest day occurs around 21 June—this is known as summer solstice. After the summer solstice, the duration of a day becomes shorter while that of a night becomes longer.”

Question and answer: UPSC's official GS Paper I (2022, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2021 · Q62

Easy

पृथ्वी ग्रह पर जल के संदर्भ में, निम्नलिखित कथनों पर विचार कीजिए :

1.नदियों और झीलों में जल की मात्रा, भू-जल की मात्रा से अधिक है।
2.ध्रुवीय हिमच्छद और हिमनदों में जल की मात्रा, भू-जल की मात्रा से अधिक है।

उपर्युक्त कथनों में से कौन-सा/कौन-से सही है/हैं?

Read this question in English

With reference to the water on the planet Earth, consider the following statements:

1. The amount of water in the rivers and lakes is more than the amount of groundwater.

2. The amount of water in polar ice caps and glaciers is more than the amount of groundwater.

Which of the statements given above is/are correct?

(a) 1 only · (b) 2 only · (c) Both 1 and 2 · (d) Neither 1 nor 2

उत्तर और व्याख्या · explanation in English

Answer: (b) केवल 2

Only statement 2 is correct: ice caps and glaciers hold about 2 per cent of Earth's water, well above the 0.68 per cent held as groundwater, while rivers and lakes together hold only about 0.009 per cent.

✗ 1. NCERT's table gives fresh water lakes 0.009 per cent and rivers 0.0001 per cent of all water, far less than groundwater at 0.68 per cent.
✓ 2. The same table gives ice caps 2.0 per cent (glaciers are counted with them), which is roughly three times the groundwater share of 0.68 per cent.

Remember · Earth's water: oceans 97.3%, ice caps and glaciers 2.0%, groundwater 0.68%, lakes 0.009%, atmosphere 0.0019%, rivers 0.0001%.

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2021 · Q64

Easy

भारत में काली कपास मृदा की रचना, निम्नलिखित में से किसके अपक्षयण से हुई है?

Read this question in English

The black cotton soil of India has been formed due to the weathering of

(a) brown forest soil · (b) fissure volcanic rock · (c) granite and schist · (d) shale and limestone

उत्तर और व्याख्या · explanation in English

Answer: (b) विदरी (फिशर) ज्वालामुखीय चट्टान

Black cotton soil (regur) forms from the weathering of the basalt lava that poured out of fissures to make the Deccan Traps, so the parent rock is fissure volcanic rock.

✓ (b) NCERT calls black soil typical of the Deccan trap (basalt) region and says it is made up of lava flows. The Deccan Traps are a flood basalt province built by lava outpourings through cracks in the crust.
✗ (c) Granite and schist are crystalline rocks; NCERT links red soil, not black soil, with crystalline igneous rocks on the Deccan plateau.
✗ (a) Brown forest soil is itself a soil, not a rock, so it cannot be the rock whose weathering produces black soil.
✗ (d) Shale and limestone are sedimentary rocks; black soil forms from volcanic basalt.

Remember · Black (regur) soil comes from Deccan Trap basalt, which erupted from fissures; it holds moisture well and suits cotton.

📘 Read it in NCERT: Class 10 Contemporary India – II, Ch 1 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 3 (practise this chapter) · Class 10 Contemporary India – II, Ch 1 (practise this chapter)

Sources

NCERT Class 10 · Contemporary India – II, Chapter 1 “This type of soil is typical of the Deccan trap (Basalt) region spread over northwest Deccan plateau and is made up of lava flows.”
NCERT Class 11 · Fundamentals of Physical Geography, Chapter 3 “The Deccan Traps from India, presently covering most of the Maharashtra plateau, are a much larger flood basalt province.”
NCERT Class 10 · Contemporary India – II, Chapter 1 “Red soil develops on crystalline igneous rocks in areas of low rainfall in the eastern and southern parts of the Deccan plateau.”

Question and answer: UPSC's official GS Paper I (2021, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2019 · Q20

Easy

जून की 21वीं तारीख को सूर्य

Read this question in English

On 21st June, the Sun

(a) does not set below the horizon at the Arctic Circle · (b) does not set below the horizon at Antarctic Circle · (c) shines vertically overhead at noon on the Equator · (d) shines vertically overhead at the Tropic of Capricorn

उत्तर और व्याख्या · explanation in English

Answer: (a) उत्तरध्रुवीय वृत्त पर क्षितिज के नीचे नहीं डूबता है

21 June is the June (northern summer) solstice: the North Pole is tilted towards the Sun, the noon Sun is overhead at the Tropic of Cancer, and every place on or north of the Arctic Circle (about 66½° N) has the Sun above the horizon for the full 24 hours.

✓ (a) The Arctic Circle is defined as the southern limit of the zone where the Sun does not set on at least one day a year — the June solstice.
✗ (b) On the same day the Antarctic Circle has the opposite: the Sun does not rise, giving 24 hours of night.
✗ (c) The noon Sun is overhead at the Equator only at the equinoxes (around 21 March and 23 September).
✗ (d) The Sun is overhead at the Tropic of Capricorn at the December solstice (around 22 December); on 21 June it is over the Tropic of Cancer.

Remember · 21 June: Sun overhead at Tropic of Cancer; midnight sun at and north of the Arctic Circle; polar night at the Antarctic Circle. Reversed around 22 December.

📘 Read it in NCERT: Class 7 Curiosity, Ch 12 (practise this chapter)

Sources

National Snow and Ice Data Center: Arctic weather and climate ↗ · reference work “The Arctic Circle marks the latitude above which the sun does not set on the summer solstice, on or about June 21, and does not rise on the winter solstice, on or about December 21.”
US National Weather Service (NOAA), Cleveland: The Seasons, the Equinox, and the Solstices ↗ “The summer solstice occurs when the sun is directly over the Tropic of Cancer, which is located at 23.5° latitude North”
NCERT Class 7 · Curiosity, Chapter 12 “In the Northern Hemisphere, the longest day occurs around 21 June—this is known as summer solstice.”

Question and answer: UPSC's official GS Paper I (2019, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2018 · Q57

Medium

निम्नलिखित कथनों पर विचार कीजिए :

1.पृथ्वी का चुम्बकीय क्षेत्र हर कुछ सौ हजार सालों में उत्क्रमित हुआ है ।
2.पृथ्वी जब 4000 मिलियन वर्षों से भी अधिक पहले बनी, तो ऑक्सीजन 54% थी और कार्बन डाइऑक्साइड नहीं थी ।
3.जब जीवित जीव पैदा हुए, उन्होंने पृथ्वी के आरंभिक वायुमण्डल को बदल दिया ।

उपर्युक्त कथनों में से कौन-सा/से सही है/हैं ?

Read this question in English

Consider the following statements:

1. The Earth's magnetic field has reversed every few hundred thousand years.

2. When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.

3. When living organisms originated, they modified the early atmosphere of the Earth.

Which of the statements given above is/are correct?

(a) 1 only · (b) 2 and 3 only · (c) 1 and 3 only · (d) 1, 2 and 3

उत्तर और व्याख्या · explanation in English

Answer: (c) केवल 1 और 3

Statements 1 and 3 are correct. The Earth's magnetic field has flipped repeatedly in the geological past, and early life released oxygen that changed the atmosphere. Statement 2 is false because the early atmosphere had carbon dioxide and very little free oxygen.

✓ 1. Rocks record past polarity flips of the magnetic field. NASA describes a history of flipping every few hundred thousand years, though the flips are irregular and the last was about 780,000 years ago.
✗ 2. The early atmosphere was mostly water vapour, nitrogen, carbon dioxide, methane and ammonia, with very little free oxygen. It was not 54% oxygen and it did contain carbon dioxide.
✓ 3. Once life evolved in the oceans, photosynthesis added oxygen to the water and later the air. About 2,000 million years ago oxygen began to flood the atmosphere.

Remember · Early atmosphere: water vapour, nitrogen, CO2, methane, ammonia, almost no free oxygen. Oxygen came from photosynthesis by early life.

📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 2 (practise this chapter) · Class 11 Fundamentals of Physical Geography, Ch 2 (practise this chapter)

Sources

NCERT Class 11 · Fundamentals of Physical Geography, Chapter 2 “The early atmosphere largely contained water vapour, nitrogen, carbon dioxide, methane, ammonia and very little of free oxygen.”
NCERT Class 11 · Fundamentals of Physical Geography, Chapter 2 “Oceans began to have the contribution of oxygen through the process of photosynthesis. Eventually, oceans were saturated with oxygen, and 2,000 million years ago, oxygen began to flood the atmosphere.”
NASA Science: Earth's Poles & Magnetic Reversal ↗ “Earth's magnetic poles and their history of flipping every few hundred thousand years.”

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

Prelims 2018 · Q85

Easy

निम्नलिखित कथनों पर विचार कीजिए :

1.बैरेन द्वीप ज्वालामुखी एक सक्रिय ज्वालामुखी है जो भारतीय राज्य-क्षेत्र में स्थित है ।
2.बैरेन द्वीप, ग्रेट निकोबार के लगभग 140 किमी पूर्व में स्थित है ।
3.पिछली बार बैरेन द्वीप ज्वालामुखी में 1991 में उद्गार हुआ था और तब से यह निष्क्रिय बना हुआ है ।

उपर्युक्त कथनों में से कौन-सा/से सही है/हैं ?

Read this question in English

Consider the following statements:

1. The Barren Island volcano is an active volcano located in the Indian territory.

2. Barren Island lies about 140 km east of Great Nicobar.

3. The last time the Barren Island volcano erupted was in 1991 and it has remained inactive since then.

Which of the statements given above is/are correct?

(a) 1 only · (b) 2 and 3 · (c) 3 only · (d) 1 and 3

उत्तर और व्याख्या · explanation in English

Answer: (a) केवल 1

Only statement 1 is correct: Barren Island, in the Andaman Sea, is India's only active volcano. It lies north-east of Port Blair, not east of Great Nicobar, and it has erupted again after 1991, most recently in 2017 as of the exam.

✓ 1. NCERT calls Barren Island, in the Andaman and Nicobar Islands, the only active volcano in India.
✗ 2. The island is about 138 km north-east of Port Blair (now Sri Vijaya Puram), the capital of the Andaman and Nicobar Islands. Great Nicobar is at the far southern end of the island chain, much farther away.
✗ 3. The volcano did not stay quiet after 1991; the Ministry of Tourism's page says it last erupted in 2017.

Remember · Barren Island, about 138 km north-east of Port Blair, is India's only active volcano and has erupted as recently as 2017.

📘 Read it in NCERT: Class 11 India: Physical Environment, Ch 2 (practise this chapter)

Sources

NCERT Class 11 · India: Physical Environment, Chapter 2 “Barren island, the only active volcano in India is also situated in the Andaman and Nicobar islands.”
Barren Island, Incredible India (Ministry of Tourism, Government of India) ↗ “Barren Island is approximately 138 kilometres northeast of Sri Vijaya Puram, the capital city of the Andaman and Nicobar Islands. It is renowned for being South Asia's only active volcano, which last erupted in 2017.”

Question and answer: UPSC's official GS Paper I (2018, Series A) — paper ↗ · answer key ↗. Explanation: Minimalist IAS, checked 30 Sept 2026 (how we verify). Permalink ·

The Syllabus X-Ray of this topic

2 of its 7 sub-topics are High

0 Core · 2 High · 3 Steady · 2 Rare

HighRocks, weathering & soils · 3 questions
HighEarth's motions, seasons & solstices · 3 questions

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