Deccan traps 465 10.3 Climate 466

Tropical rainy climatic group 466 Tropical monsoon rainforest 466 Tropical wet and dry climate 466 Dry climate group 466 Tropical semi-arid steppe climate 466 Tropical and sub-tropical desert 467 Tropical and sub-tropical steppe 467 Humid sub-tropical climate group 467 Humid sub-tropical with dry winter 467 Mountain climate 467

10.4 Distribution of residual soils 468 Black soils 468 Red soils 469 Laterites 469

10.5 Physico-chemical properties 469 Black soils 469 Red soils 471 Laterites 473

10.6 Geotechnical engineering data 473 Black soils 473 Red soils 473 Laterites 481

References 488


India lies to the north of the equator between 8◦4′ and 37◦6′ North latitude and 68◦7′ and 97◦25′ East longitude. The geography of India is diverse and can be divided into three distinct regions, (a) the peninsular region lying to the south of the Indo-Gangetic plains, (b) the Indo-Gangetic alluvial plains stretching across northern India from Assam and Bengal on the east, through Bihar and Uttar Pradesh to Punjab on the west, and (c) the Extra-peninsula, comprising the Himalayan ranges. The peninsular region consists of basaltic rocks of various types, granites and metamorphic rocks derived from the granites. The basaltic Deccan traps are associated with the most extensive occurrence of black soil formation. In the areas occupied by Archaean gneisses and Deccan traps, extensive deposits of red soils are encountered. Large deposits of laterites are found as cappings over the Deccan traps. The geology of the soil-forming rocks is briefly considered as a prelude to soil characteristics.