Soil profiles develop distinct vertical layers called horizons as physical, chemical, and biological processes alter earth materials over time. How should each master soil horizon designation be matched to its primary defining characteristic?
- O HorizonComposed predominantly of undecomposed and partially decomposed organic matter and leaf litter at the surface.
- A Horizon (Topsoil)Rich in dark organic humus mixed with mineral particles; primary zone of biological activity and root growth.
- B Horizon (Subsoil)Zone of accumulation (illuviation) where leached fine clays, iron oxides, and soluble minerals collect.
- C Horizon (Substratum)Composed of partially weathered parent rock fragments with minimal organic matter and very little biological alteration.
Answer
The O Horizon matches the surface organic and leaf litter layer; the A Horizon (Topsoil) matches the humus-rich mineral layer with active biological growth; the B Horizon (Subsoil) matches the zone of accumulated leached clays and minerals; and the C Horizon (Substratum) matches the partially weathered parent rock layer.
Soil profiles develop vertically through weathering, leaching, and biological processes. The O Horizon is the organic layer at the surface, the A Horizon is the nutrient-dense topsoil with humus, the B Horizon is the subsoil where leached clays and minerals collect, and the C Horizon contains partially weathered fragments of parent material.
Step-by-Step Solution
Key Concept
Soil Profile Stratification and Horizon Characteristics
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