The district lies towards the eastern boundary of the Deccan trap area and hence the soils of the District are either true black cotton soil or  else formed from a basis of cotton soil modified by intermixture with soils derived from the gneissic formation which surrounds it. This black cotton soil or regur determines to a large extent the nature of the agriculture of the District. There is no general agreement as to how this wide expanse of regur has been formed. Its character is that of an alluvial back water or lake deposit, but it is difficult to see how such a formation can have occurred on the Deccan plateau. In many places there is no doubt that the soil is derived by the disintegration of other argillaceous rocks. That the process of regur formation is superficial one can be well seen in the undulating country of the Nagpur district. On the tops of the flat hills where the surface suffers less from erosion that the sides, the soil is dark brown in colour. That upon the sides of these hills being more decently formed is reddish brown, while in the valleys below, where the rain-wash gradually accumulates, the soil becomes of a true black cotton-soil colour. It is largely as a result of this erosion and subsequent accumulation that the agricultural value of the land of this District varies so enormously.