Mature soil has gone through the natural soil formation process. It has clearly developed genetic horizons and become stabilized to be in equilibrium with its environment.
Soil is formed when rocks and parent materials are acted upon by weathering forces under the influence of soil-forming factors. However, the formed soil is a loose, disorganized and unconsolidated mass of particles of various sizes. The age of soil is determined by the level of weathering and the extent to which parent material is stratified into horizons or soil layers. Mature soils tend to have more and thicker horizons and are classified as older as there are more differences in the properties of soil between two adjacent horizons.