Time

Generally, the length of time the soil forming processes operate, determines maturation of soils and profile development. However, it is difficult to be precise about the role of time in soil formation, since soils vary greatly in their rates of development. On porous materials such as sandstones, soil formation is much more rapid than on impermeable materials, at least initially. On glacial hills, a few hundred years may be enough to form a soil; on dense basalt very much longer is likely to be required. Renewed evolution takes place in soils when climate or other factors change, causing the soil to adjust. In practice, many soils in mid-latitude regions are polycyclic.