Black soil
Explanation
Lava plateaus are extensive, flat-topped highlands formed by the accumulation of highly fluid basaltic lava during fissure eruptions. The soil character of a region is heavily influenced by the parent rock material. In the case of lava plateaus, the parent rock is solidified basalt.
Detailed Analysis
- Formation of Black Soil: The weathering and erosion of basaltic lava rocks over thousands of years result in the formation of Black soil (also known as Regur soil).
- Chemical Composition: Basalt is rich in iron, magnesium, and alumina. Consequently, the resulting soil is rich in nutrients like calcium carbonate, magnesium, potash, and lime, but generally poor in phosphorous.
- Physical Characteristics: This soil is clayey, deep, and impermeable. It is well-known for its high moisture-retention capacity and self-ploughing characteristic (developing cracks during dry spells).
- Geographical Example: The Deccan Trap in India is a prime example of a lava plateau. It covers a major part of Maharashtra, Madhya Pradesh, Gujarat, Andhra Pradesh, and parts of Karnataka, which corresponds directly to the distribution of black soil in the country.
Comparison with Other Options
- Red soil: Typically develops on crystalline igneous rocks (like granite and gneiss) in areas of low rainfall, not specifically from basaltic lava flows.
- Alluvial soil: This is a depositional soil transported by rivers and streams, found in river basins and deltas, rather than being formed in situ on volcanic plateaus.
- Laterite soil: Develops in areas with high temperature and high rainfall due to intense leaching. While it can be found on the summits of some plateaus, it is not the primary soil characterizing the basaltic lava plains.
Key Takeaway: Lava plateaus are composed of basaltic rocks, the weathering of which produces Black soil (Regur), which is highly suitable for cotton cultivation.