Pedogenesis involves progressive biochemical and physical alterations of parent material over extended periods. Which sequence correctly places the following stages of soil development in chronological order, from initial bedrock weathering to the establishment of a mature zonal soil profile?
- 1Physical disaggregation and chemical disintegration of solid bedrock, creating a layer of loose mineral regolith
- 2Colonization by pioneer micro-organisms and plants, leading to organic decay and humification in upper layers
- 3Percolation of acidic water causing active eluviation (leaching) of clay minerals and soluble bases from the topsoil
- 4Subsurface illuviation resulting in the accumulation of translocated iron oxides and silicate clays in the B horizon
- 5Establishment of a mature, quasi-equilibrium zonal profile exhibiting distinct, well-defined soil horizons
Answer
The correct chronological sequence of soil formation is: bedrock breakdown into regolith, pioneer organism colonization and humification, topsoil eluviation, subsoil illuviation, and final zonal profile stabilization.
The correct sequence follows the natural progression of soil development: primary weathering creates parent regolith, biological colonization adds organic material, downward percolating water removes fine minerals via eluviation, these leached materials accumulate in the subsoil via illuviation, and sustained pedogenic action produces a mature zonal profile with distinct horizons.
Step-by-Step Solution
Key Concept
Chronological stages of pedogenesis and soil profile differentiation