The ravines, locally called bihad, that have destroyed farmland in Bhind, Morena and Sheopur were cut by which river system?

The Tropic of Cancer crosses Madhya Pradesh almost through the middle, running past Ratlam, Ujjain, Bhopal, Vidisha, Sagar, Jabalpur and Shahdol, so the state is divided nearly in half by it and more districts of Madhya Pradesh are touched by the line than in any other state.

The Deccan trap basalt underlies a very large part of the state, from the Malwa plateau through the Narmada valley to Nimar and the Satpura, and its weathering has given black soil, also called regur or cotton soil, the largest share of the state's area.

The lava flows that spread over central and western India at the end of the Cretaceous left thick sheets of basalt, and when basalt weathers in a monsoon climate it yields a fine clay rich in iron, lime and magnesium, which is exactly the black soil of Malwa, the Narmada…

There the old crystalline rocks, gneiss and granite, lie at the surface, and the iron released by their weathering gives the soil its red colour, turning yellow where the iron is hydrated by heavier rain.

The reason is that the state's rain comes mostly from the Bay of Bengal branch of the monsoon, which enters from the east and weakens as it travels inland, so the farthest north-western corner is driest.