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Q74 (IAS/2021) Geography › Indian Physical Geography › Indian soil types Official Key

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

Result
Your answer: —  ·  Correct: B
Explanation

The correct answer is Option 2: fissure volcanic rock.

Black cotton soil, also known as Regur soil, is primarily found in the Deccan Trap region of India. Its formation is attributed to the weathering of basaltic rocks formed by lava flows during fissure-type volcanic eruptions millions of years ago. These volcanic rocks are rich in iron, magnesium, and aluminum, which contribute to the soil's characteristic dark color and high fertility.

  • Option 1: Brown forest soil is found in Himalayan regions and is unrelated to the volcanic Deccan plateau.
  • Option 3: Weathering of granite and schist typically results in Red and Yellow soils, which are more acidic and less moisture-retentive.
  • Option 4: Shale and limestone are sedimentary rocks; their weathering does not produce the specific mineralogical composition found in black soil.

Therefore, the distinct clayey texture and moisture-holding capacity of black soil are direct results of the disintegration of fissure volcanic (basaltic) rocks.

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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. The black cotton soil of India has been formed due to the weathering of [A] brown forest soil [B] fissure volcanic rock [C] granite an…
At a glance
Origin: From standard books Fairness: High fairness Books / CA: 10/10 · 0/10

This is a 'reward' question for reading NCERTs line-by-line. It validates the strategy that Physical Geography fundamentals (specifically the Rock-Soil linkage) must be mastered from Class IX and XI. If you missed this, you are neglecting the absolute basics of the syllabus.

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
What parent rock type(s) formed the black cotton soil (regur) of India through weathering?
Origin: Direct from books Fairness: Straightforward Book-answerable
From standard books
NCERT. (2022). Contemporary India II: Textbook in Geography for Class X (Revised ed.). NCERT. > Chapter 1: The Rise of Nationalism in Europe > Black Soil > p. 9
Presence: 5/5
“These soils are black in colour and are also known as regur soils. Black soil is ideal for growing cotton and is also known as black cotton soil. It is believed that climatic condition along with the parent rock material are the important factors for the formation of black soil. This type of soil is typical of the Deccan trap (Basalt) region spread over northwest Deccan plateau and is made up of lava flows. They cover the plateaus of Maharashtra, Saurashtra, Malwa, Madhya Pradesh and Chhattisgarh and extend in the south east direction along the Godavari and the Krishna valleys.”
Why this source?
  • Identifies the Deccan Trap (basaltic lava flows) as the typical region/source of black (regur) soil.
  • Explicitly links parent rock material with the formation of black soil.
Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 6: Soils > 3. Black or Regur Soils > p. 11
Presence: 5/5
“Black soils, also known as Regur (cotton-soil) and internationally as 'tropical chernozems', are the third largest soil group in India. They sprawl over about 50 million hectares accounting for 15% of the total reporting area of the country. They get their parent material from the weathered rocks of Cretaceous lava. They are mature soils. Over the greater parts of the black earth soil, the average annual rainfall varies between 50 and 75 cm. The colour of these soils varies from deep black to light black. In general, these soils have clayey texture. Moreover, these soils have a high water retaining capacity.”
Why this source?
  • States that black soils get their parent material from weathered rocks of Cretaceous lava.
  • Describes soil properties (clayey, high water retention) consistent with weathering of basaltic lava.
CONTEMPORARY INDIA-I ,Geography, Class IX . NCERT(Revised ed 2025) > Chapter 2: Physical Features of India > The Peninsular Plateau > p. 13
Presence: 5/5
“Eastern Ghats. Locate the famous hill stations of Udagamandalam, popularly known as Ooty and the Kodaikanal. One of the distinct features of the Peninsular plateau is the black soil area known as Decean Trap. This is of volcanic origin, hence, the rocks are igneous. Actually, these rocks have denuded over time and are responsible for the formation of black soil. The Aravali Hills lie on the western and northwestern margins of the Peninsular plateau. These are highly eroded hills and are found as broken hills. They extend from Gujarat to Delhi in a southwest-northeast direction.”
Why this source?
  • Describes the Deccan Trap as volcanic in origin and the igneous rocks have denuded to form black soil.
  • Specifies that these igneous/volcanic rocks are responsible for black soil formation on the peninsular plateau.
Pattern takeaway: UPSC often tests the *process* behind a geographic feature, not just its location. The question bridges Geology (Volcanism) and Agriculture (Soil). The options (Granite vs Basalt vs Shale) required knowing the specific lithology of the Deccan Trap.
How you should have studied
  1. [THE VERDICT]: **Sitter**. Directly lifted from NCERT Class X (Ch 1, p.9) and Class IX (Ch 2, p.13). The phrase 'Deccan trap (Basalt)... made up of lava flows' is explicit text.
  2. [THE CONCEPTUAL TRIGGER]: **Soil Genesis (Pedology)**. Specifically, the role of 'Parent Material' as a passive factor in soil formation.
  3. [THE HORIZONTAL EXPANSION]: **Map Parent Rocks to Soils**: 1. **Red Soil**: Weathering of crystalline igneous rocks (Granite/Gneiss) in low rainfall areas. 2. **Laterite Soil**: Intense leaching (Desilication) in high temp/high rain areas. 3. **Alluvial Soil**: Depositional (transported), not residual. 4. **Arid Soil**: Kankar layer formation due to Calcium accumulation. 5. **Karewas**: Lacustrine deposits (Saffron cultivation).
  4. [THE STRATEGIC METACOGNITION]: Don't just memorize 'Black Soil = Cotton'. Ask *Why?* The 'Why' is the Basaltic lava. Always study the chain: **Geological Event (Fissure Eruption) → Parent Rock (Basalt) → Weathering Process → Soil Type (Regur) → Crop (Cotton)**.
Concept hooks from this question
📌 Adjacent topic to master
S1
👉 Deccan Traps (Basalt) as Parent Rock
💡 The insight

Black cotton (regur) soils are formed by weathering of the basaltic lava flows of the Deccan Traps.

High-yield for questions on soil types and distribution: links geology (Deccan Traps) with soil occurrence and crop suitability. Helps answer queries on regional soil maps, agricultural patterns (cotton belt), and links physiography with economic geography.

📚 Reading List :
  • NCERT. (2022). Contemporary India II: Textbook in Geography for Class X (Revised ed.). NCERT. > Chapter 1: The Rise of Nationalism in Europe > Black Soil > p. 9
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 6: Soils > 3. Black or Regur Soils > p. 11
  • CONTEMPORARY INDIA-I ,Geography, Class IX . NCERT(Revised ed 2025) > Chapter 2: Physical Features of India > The Peninsular Plateau > p. 13
🔗 Anchor: "What parent rock type(s) formed the black cotton soil (regur) of India through w..."
📌 Adjacent topic to master
S1
👉 Weathering of Igneous/Volcanic Parent Rock
💡 The insight

Chemical and physical weathering of igneous (volcanic) rocks produces the regolith that becomes black soils.

Essential for process-based questions on soil formation and properties; connects geomorphic processes (weathering, denudation) with soil characteristics and maturity. Enables answers that integrate geomorphology, climate influence, and soil science.

📚 Reading List :
  • FUNDAMENTALS OF PHYSICAL GEOGRAPHY, Geography Class XI (NCERT 2025 ed.) > Chapter 5: Geomorphic Processes > Parent Material > p. 44
  • Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 4: Weathering, Mass Movement and Groundwater > CHEMICAL WEATHERING > p. 36
🔗 Anchor: "What parent rock type(s) formed the black cotton soil (regur) of India through w..."
📌 Adjacent topic to master
S1
👉 Soil–Crop Relationship: Black Soil and Cotton
💡 The insight

Black (regur) soils derived from basaltic parent rock are especially suitable for cotton cultivation.

Useful for questions on agricultural geography and crop distribution; links soil type to crop suitability, regional economy, and land use planning. Helps in explaining why certain crops dominate specific physiographic regions.

📚 Reading List :
  • NCERT. (2022). Contemporary India II: Textbook in Geography for Class X (Revised ed.). NCERT. > Chapter 1: The Rise of Nationalism in Europe > Black Soil > p. 9
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 6: Soils > 3. Black or Regur Soils > p. 11
  • Geography of India ,Majid Husain, (McGrawHill 9th ed.) > Chapter 2: Physiography > Significance of the Peninsular Plateau > p. 62
🔗 Anchor: "What parent rock type(s) formed the black cotton soil (regur) of India through w..."
🌑 The Hidden Trap

The 'Self-Ploughing' Characteristic: Black soil swells when wet and shrinks when dry, developing deep cracks. **Next Logical Question:** Which soil requires tilling *immediately* after the first shower? (Answer: Black Soil, otherwise it becomes too sticky/plastic to work). Also, the black colour is due to 'Titaniferous Magnetite'.

⚡ Elimination Cheat Code

Use **Geographic Common Sense**:
1. 'Black Cotton' = Deccan Plateau.
2. Deccan Plateau = Volcanic origin (everyone knows this).
3. Volcanoes produce Lava/Magma.
4. Look at options: Granite (Intrusive), Shale (Sedimentary), Limestone (Sedimentary), **Fissure Volcanic Rock** (Extrusive).
5. Only Option B matches the volcanic origin story.

🔗 Mains Connection

Link to **GS3 Agriculture (Fertilizers)**: Black soils are chemically rich in Lime, Iron, Magnesia, and Alumina but **poor in Nitrogen, Phosphorus, and Organic matter**. This explains why farmers in the Deccan cotton belt are heavily dependent on N and P fertilizers (Urea/DAP), impacting the fertilizer subsidy bill.

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SIMILAR QUESTIONS

CDS-I · 2011 · Q86 Relevance score: 0.35

Consider the following statements about black soil of India : 1. Black soil becomes sticky when it is wet. 2. Black soil contains adequate nitrogen as well as phosphorus required for the growth of plants. Which of the statements given above is/are correct?

IAS · 2010 · Q101 Relevance score: 0.27

Tamil Nadu is a leading producer of mill-made cotton yarn in the country what could be the reason? 1. Black cotton soil is the predominant type of soil in the State. 2. Rich pool of skilled labour is available. Which of the above is/are the correct reasons?

IAS · 2010 · Q121 Relevance score: -0.40

Which one of the following is the appropriate reason for considering the Gondwana rocks as most important of rock systems of India ?

CAPF · 2013 · Q45 Relevance score: -0.57

Which one among the following is not correct regarding the black soils of Peninsular India?

NDA-II · 2015 · Q34 Relevance score: -3.23

The term 4Regur' is used to mean: