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

Answer: B. The BLACK COTTON SOIL (Regur / Black soil) of India formed by the weathering of FISSURE VOLCANIC ROCK (basalt). The BLACK SOIL or REGUR (also called BLACK COTTON SOIL because of its suitability for cotton) is one of India's major soil types. It covers about 16% of the country's area, primarily across the DECCAN PLATEAU — Maharashtra, Gujarat, Madhya Pradesh, Chhattisgarh, parts of Andhra Pradesh, Karnataka, Tamil Nadu. **GEOLOGICAL ORIGIN:** Black soil is the WEATHERING PRODUCT OF THE DECCAN TRAPS — extensive BASALTIC LAVA FLOWS that erupted as FISSURE VOLCANISM AT THE END OF THE CRETACEOUS (~66 million years ago, around the time of the K-Pg mass extinction). These fissure eruptions covered an estimated 500,000 sq km in successive horizontal basalt flows up to 2 km thick. The basalt weathers in the warm semi-arid Indian climate to produce: - Dark, heavy, CLAYEY soil rich in MONTMORILLONITE / SMECTITE clays. - High in iron, magnesium, calcium, alumina, potash. - Develops DEEP CRACKS in dry season (self-mulching property). - Moisture-retaining when wet — ideal for COTTON cultivation. - Low in nitrogen, phosphorus, organic matter. Why other options are WRONG: (A) Brown forest soil — distinct soil type found in temperate forest mid-latitude regions, not parent material for regur. (C) Granite and schist — produces RED SOIL, NOT black soil. Red soils dominate the southern Peninsula (Karnataka, Tamil Nadu) on granitic-gneissic parent rocks. (D) Shale and limestone — gives rise to other soil types but not the Deccan regur. Source: syllabus India: Physical Environment 'Soils' chapter / GSI Deccan Traps geology.