1. O Horizon (Organic Layer)
* Location: The uppermost layer.
* Characteristics: Composed of decaying plant and animal matter, typically dark in color.
* Sublayers:
* O1: Mostly undecomposed plant material (leaves, twigs, etc.).
* O2: Partially decomposed organic matter.
* O3: Highly decomposed organic matter, resembling humus.
2. A Horizon (Topsoil)
* Location: Below the O horizon.
* Characteristics: Rich in organic matter, mineral particles, and living organisms. Supports plant life. Often darker than lower layers.
* Formation: Formed by the mixing of mineral soil from lower layers with organic matter from the O horizon.
3. E Horizon (Eluviated Layer)
* Location: Found beneath the A horizon in some soils.
* Characteristics: Lighter in color due to the leaching of minerals and organic matter.
* Formation: Minerals and organic matter are transported downward (eluviated) by water.
4. B Horizon (Subsoil)
* Location: Below the E horizon (if present) or the A horizon.
* Characteristics: Enriched with minerals and materials leached from upper layers. Often has a distinctive color and texture due to the accumulation of clay, iron oxides, or carbonates.
* Formation: The B horizon is the zone of accumulation.
5. C Horizon (Parent Material)
* Location: The layer below the B horizon.
* Characteristics: Unweathered or slightly weathered parent material from which the soil formed. Can be bedrock, glacial till, or other deposits.
* Formation: This layer is the starting point for soil development.
6. R Horizon (Bedrock)
* Location: The solid, unweathered rock layer below the C horizon.
* Characteristics: Resistant to weathering and soil formation.
Important Notes:
* Not all soils have all of these horizons. The presence and prominence of specific horizons depend on factors like climate, vegetation, parent material, and time.
* Soil profiles can be complex and vary greatly across different locations and types of soils.
Understanding soil horizons is crucial for:
* Agriculture: Determining the suitability of land for different crops and understanding nutrient availability.
* Environmental Science: Assessing soil health, water infiltration, and erosion potential.
* Engineering: Evaluating soil stability and suitability for construction projects.
