gen-define-soil-horizons-and-give-one-short-worked-example-4bc6

Define soil horizons and give one short worked example.

# Soil Horizons **Soil horizons** are distinct, roughly parallel layers that form in soil as a result of soil-forming processes over time. Each horizon has characteristic physical, chemical, and biological properties that differ from the layers above and below it. ## Main Horizons (from top to bottom): - **O Horizon**: Organic layer of decomposing plant/animal material - **A Horizon**: Topsoil; dark, mineral soil mixed with organic matter - **E Horizon**: Eluviation (leaching) layer; lighter colored, minerals washed out - **B Horizon**: Subsoil; accumulation zone for clays, minerals, and nutrients - **C Horizon**: Weathered parent material; partially broken-down rock - **R Horizon**: Bedrock; unweathered solid rock --- ## Worked Example: Forest Soil Profile **Location**: Temperate deciduous forest **Profile description** (top to bottom): 1. **O Horizon** (0-5 cm): Dark brown leaf litter and humus 2. **A Horizon** (5-20 cm): Dark brown, rich in organic matter, crumbly texture 3. **E Horizon** (20-30 cm): Light gray, sandy, heavily leached 4. **B Horizon** (30-60 cm): Reddish-brown, clay accumulation, denser structure 5. **C Horizon** (60-100 cm): Pale brown weathered rock fragments 6. **R Horizon** (100+ cm): Solid granite bedrock This profile shows typical development where organic matter accumulates at the surface, minerals leach from the E horizon, and accumulate in the B horizon below.