the age of the vertisol is estimated as less than years and this vertisol is fertile because a balance between soil erosion and soil creation is maintained excessive erosion removes the topsoil causing desertification but where soil erosion is much less than soil creation over the long term it eluviates and dissipates soil nutrients forming aged soils oxisols under the rainfall categorization it is primarily part of region iv annual aridity index of or more and summer aridity index of or more and has made the development of north europeantype agriculture possible