Question

Given below are two statements:
Statement (I): The composition and relative content of clay minerals depend on the parent material, climate and micro-topography.
Statement (II): Kaolinite is the dominant clay mineral in subtropical and tropical areas with high air temperature
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Both Statement (I) and Statement (II) are correct.
• B. Both Statement (I) and Statement (II) are incorrect.
• C. Statement (I) is correct but Statement (II) is incorrect.
• D. Statement (I) is incorrect but Statement (II) is correct.

Hint:

- High Weathering Leaching (Tropics) \(\rightarrow\) 1:1 Clays (Kaolinite) dominate.
- Moderate Weathering (Arid/Semi-arid) \(\rightarrow\) 2:1 Clays (Montmorillonite/Smectite) dominate.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Clay minerals are secondary hydrous aluminosilicates formed in the soil through the chemical weathering of primary minerals.
Their formation pathways, structural types (e.g., 1:1, 2:1), and spatial distribution are determined by soil-forming factors.

Step 2: Detailed Explanation:
Let us evaluate both statements:
- Statement (I):
The chemical weathering processes that synthesize secondary clay minerals are heavily influenced by the composition of the parent rock, ambient climate (temperature and precipitation), and local micro-topography (which governs water drainage and leaching intensity).
For example, under similar parent materials, a humid climate will produce different clays compared to an arid climate.
Therefore, Statement (I) is correct.
- Statement (II):
In tropical and subtropical regions characterized by high temperatures and abundant rainfall, intense chemical leaching of silica (desilication) and basic cations occurs.
This advanced weathering environment favors the formation of stable, low-silica 1:1 type clay minerals, principally kaolinite.
Conversely, in drier or less weathered environments, 2:1 expanding clays like smectite/montmorillonite dominate.
Therefore, Statement (II) is correct.
Both statements are correct.

Step 3: Final Answer:
Both Statement (I) and Statement (II) are correct (Option A).