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Q: Which type of soils are formed by decomposition of rock, removal of bases and silica and accumulation of iron oxide and aluminium oxide? Deep brown soil of cellular structure, easy to excavate but gets hardened on exposure to air owing to the formation of hydrated iron oxides is called as
  • A. Desert soils
  • B. Lateritic soils
  • C. Black cotton soils
  • D. Alluvial soils
Correct Answer: Option B - Laterites and laterite soils– Laterization mainly due to the decomposition of rock, removal of silica and bases, and accumulation of aluminium oxide and iron oxide. ● The red, pink or brown colour of laterites is mainly due to iron oxide. Black cotton soil– This soil is expansive in nature due to the presence of montmorillonite and illite clay minerals. • These soil are residual deposists from basalt or trap rocks. Desert soils– These soil are wind blown deposits generally present in the form of sand dunes. Alluvial soils– Soils deposited by surface water along rivers. Loam– Mixture of sand, silt and clay size particles approximately in equal properties, sometimes contains organic matter. Bentonite– Decomposed volcanic ash containing a high percentage of clay mineral montomorillonite. • It exhibits high degree of shrinkage and swelling.
B. Laterites and laterite soils– Laterization mainly due to the decomposition of rock, removal of silica and bases, and accumulation of aluminium oxide and iron oxide. ● The red, pink or brown colour of laterites is mainly due to iron oxide. Black cotton soil– This soil is expansive in nature due to the presence of montmorillonite and illite clay minerals. • These soil are residual deposists from basalt or trap rocks. Desert soils– These soil are wind blown deposits generally present in the form of sand dunes. Alluvial soils– Soils deposited by surface water along rivers. Loam– Mixture of sand, silt and clay size particles approximately in equal properties, sometimes contains organic matter. Bentonite– Decomposed volcanic ash containing a high percentage of clay mineral montomorillonite. • It exhibits high degree of shrinkage and swelling.

Explanations:

Laterites and laterite soils– Laterization mainly due to the decomposition of rock, removal of silica and bases, and accumulation of aluminium oxide and iron oxide. ● The red, pink or brown colour of laterites is mainly due to iron oxide. Black cotton soil– This soil is expansive in nature due to the presence of montmorillonite and illite clay minerals. • These soil are residual deposists from basalt or trap rocks. Desert soils– These soil are wind blown deposits generally present in the form of sand dunes. Alluvial soils– Soils deposited by surface water along rivers. Loam– Mixture of sand, silt and clay size particles approximately in equal properties, sometimes contains organic matter. Bentonite– Decomposed volcanic ash containing a high percentage of clay mineral montomorillonite. • It exhibits high degree of shrinkage and swelling.