Examkin

Question

Difficulty: EasySoil Formation, Profiles, and Major Vegetation Types

Arrange the following soil profile horizons in the correct sequential order from the surface layer down toward the bedrock:

  1. 1O Horizon (Organic layer consisting of fresh and decomposing leaf litter and humus)
  2. 2A Horizon (Topsoil composed of mineral matter mixed with humified organic matter)
  3. 3B Horizon (Subsoil containing accumulated silicate clays, iron, or aluminum from illuviation)
  4. 4C Horizon (Partially altered parent material consisting of unweathered to weakly weathered rock fragments)

Answer

The correct vertical sequence from top to bottom is: O Horizon, A Horizon, B Horizon, and C Horizon.
A fully developed soil profile forms distinct vertical layers called horizons. Starting at the ground surface, the sequence begins with the organic O Horizon, followed by the nutrient-rich A Horizon (topsoil), the mineral-accumulating B Horizon (subsoil), and finally the partially weathered C Horizon (parent material) overlying bedrock.

Step-by-Step Solution

1
Identify the top surface layer accumulated from plant debris
O Horizon (Organic layer)
Decomposing organic matter accumulates directly at the ground surface.
2
Identify the topsoil layer beneath the surface organic layer
A Horizon (Topsoil)
Soluble nutrients and organic matter mix with fine mineral grains in this upper zone.
3
Identify the zone of illuviation (subsoil accumulation)
B Horizon (Subsoil)
Leached minerals transported downward from upper layers accumulate in the subsoil.
4
Identify the weathered substrate layer above consolidated rock
C Horizon (Weathered parent material)
Parent rock is broken into rock fragments forming the base substrate above bedrock.

Key Concept

Soil Profile Horizons
Rate this question

Topics

Soil Formation, Profiles, and Major Vegetation Types

More questions from this topic