Question

Partially weathered bedrock is _______ horizon

• A. R
• B. C
• C. Biomantle
• D. D

Hint:

Remember the order of master horizons: Solum is A + B (active soil). Beneath the solum is C (partially weathered parent rock), and at the very bottom is R (hard, unweathered bedrock).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
A soil profile consists of several master horizons (O, A, E, B, C, R) developed over time.
These horizons reflect different stages of weathering, organic matter accumulation, and mineral transformation.

Step 2: Detailed Explanation:
Let us analyze the relevant soil horizons:
C Horizon (B): This horizon lies beneath the solum (A and B horizons).
It consists of partially weathered parent bedrock that has undergone minimal pedogenic alteration.
It lacks the structural features of the A and B horizons but represents the raw parent material from which the upper soil horizons develop.
Therefore, the C horizon represents partially weathered bedrock.
R Horizon (A): This is the lowermost layer of the soil profile, consisting of unweathered, consolidated solid bedrock (such as granite, basalt, or limestone). It cannot be dug easily with a spade.
D Horizon (D): An older term occasionally used to represent underlying material unlike the parent material, now replaced by more specific designations.
Therefore, partially weathered parent rock is classified as the C horizon.

Step 3: Final Answer:
Partially weathered bedrock is represented by the C horizon, which corresponds to option (B).