Soils develop from geological materials called parent materials at the earth‚s surface through their interaction with climate, biota, and topography over time. Parent material, climate, biota, topography, and time are referred to as factors of soil formation.
The parent material from which soils form consists of unconsolidated and more or less chemically changed (weathered) mineral or accumulated organic particles. Climate influences soil development through temperature and precipitation, which control the weathering rate, the movement of substances through the profile and the type of vegetation that becomes established. Biota, including plants, animals and micro-organisms, contribute to soil formation by adding organic matter and altering biochemical properties of the profile. Topography refers to relief, aspect and slope. These properties influence soil development by controlling the distribution of water in the landscape, the amount of sun received and the susceptibility to erosion. Finally, the time elapsed since the beginning of soil formation controls how far soil development has progressed and how different the soil has become from the underlying parent material.