(d) The black soil, also known as Regur soil, is formed by the weathering of lava (igneous rocks)and cooling of lava after a volcanic eruption. The soil in the Deccan Plateau consists of black basalt soil, which is rich in humus, iron and also contains high quality of magnesia, lime and alumina. The texture and composition of this soil is formed by lava – the breakdown of igneous rocks during the volcanic action.