O, A, B, C, and R soil layers — composition and formation
Hover layer for info · Click to take soil sample
O Horizon: Organic litter (leaves, decomposing material). A Horizon (Topsoil): Humus-rich, dark, root zone. B Horizon (Subsoil): Clay/mineral accumulation from leaching. C Horizon: Weathered parent material (rocks). R Horizon: Unweathered bedrock. Water percolates down, carrying minerals (eluviation → illuviation). Organisms mix organic matter into soil.