Black soil in Madhya Pradesh is formed by which rock?

Question

UnlockIAS · Accepted Answer

Correct — C, Basalt. Black soil (regur / black cotton soil) is a residual soil formed in situ by the prolonged weathering of basalt — the fissure-eruption lava rock of the Deccan Trap. Iron, magnesium and clay minerals (chiefly montmorillonite) released during this weathering give the soil its dark colour, high moisture retention, and characteristic self-ploughing (cracking) behaviour when dry. Madhya Pradesh's Malwa and Nimar plateaus, built on this basalt-capped Deccan Trap, are the state's principal black-soil tracts.

Why the other options are wrong — (a) Sandstone, a sedimentary rock, typically weathers into sandy, often reddish or yellowish soils — not the clay-rich black soil.  (b) Limestone weathers into calcium-rich (calcareous) soils, distinct from basalt-derived black soil.  (d) Gneiss, a metamorphic rock common across peninsular India's older shield areas, is associated with red and lateritic soils, not black soil.

Concept: Black soil (regur / black cotton soil) is a residual soil formed in situ by the prolonged chemical weathering of basalt — the fissure-eruption lava rock that makes up the Deccan Trap. Its clay-rich, moisture-retentive, self-ploughing nature (from a high proportion of montmorillonite clay minerals) makes it well suited to cotton and other rain-fed crops.

State PCS 2024 Q55 — Madhya Pradesh GK PYQ with Answer

State PCS 2024 Q55 — Madhya Pradesh GK PYQ with Answer