Question map
The black cotton soil of India has been formed due to the weathering of
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.
PROVENANCE & STUDY PATTERN
Guest previewThis 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.
This question can be broken into the following sub-statements. Tap a statement sentence to jump into its detailed analysis.
- 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.
- 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.
- 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.
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