The Earth Contents

5. Soils

Soils take time, typically thousands of years, to form

Soils are formed by the weathering of rocks, and the resulting particles are then distributed by gravity, water and ice (and in the case of the smaller particles, by wind). Loose rocks and stones gradually erode to produce a soil with more smaller particles, and the different size-bands of particles become arranged in horizons. Freezing and thawing cycles, and the physical movement of the particles, increases the weathering process, until eventually there is a suitable structure to support plant life. These particles are called the parent material, the mineral base on which soils are formed. The characteristics of this parent material have a profound effect on the soil, as their size and chemical properties will influence the physical and chemical processes which are essential to soil formation.

Soils are formed by the weathering of rocks

How does soil form?