A vast region of layered basaltic lava flows in west-central India, formed by massive volcanic eruptions near the end of the Cretaceous, that gives the Deccan its stepped topography and black cotton soil.
- Formed by enormous fissure (flood) eruptions of fluid basaltic lava about 66 million years ago, around the Cretaceous-Palaeogene boundary, as India drifted over the Reunion hotspot.
- The word "trap" comes from a Scandinavian term for "step", reflecting the step-like (terraced) hills produced by successive horizontal lava sheets.
- Cover a large part of Maharashtra, with extensions into Gujarat, Madhya Pradesh, and Karnataka; once far more extensive before erosion.
- Weather into the fertile black cotton soil (regur), which is clayey and moisture-retentive and ideal for cotton.
- The eruptions are linked in scientific debate to the mass extinction (including the dinosaurs) at the end of the Cretaceous, alongside the asteroid impact theory.
The Cretaceous fissure-eruption origin, the link to black cotton soil, the stepped topography, and the States covered are recurring physical-geography and soils facts.
Deccan Traps are basaltic (fissure, flood basalt) volcanism, not the explosive cone-building type; "trap" means step, not a trapping of anything. The black soil is the weathering product of this basalt.
Cretaceous flood-basalt lava flows of the Deccan; stepped topography, source of black cotton soil.