Question

The upper limit of clay sized particles and the lower limit of gravel across both the USDA and IUSS classification systems is:
(A). 0.002 mm
(B). 0.005 mm
(C). 5.0 mm
(D). 2.0 mm
Choose the correct answer from the options given below:

• A. A and B only.
• B. B and C only.
• C. B and D only.
• D. A and D only.

Hint:

Remember the universal agreement between classification systems (USDA, IUSS, ISSS):
Upper limit of clay = \( 0.002 \text{ mm} \).
Upper limit of sand (lower limit of gravel) = \( 2.0 \text{ mm} \).

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Different soil classification systems (such as USDA - United States Department of Agriculture, and IUSS - International Union of Soil Sciences) define specific particle diameter limits to classify sand, silt, clay, and gravel.
Detailed Explanation:
Let us look at the standard grain size limits defined by both USDA and IUSS:
- Clay-sized particles: Both the USDA and IUSS systems define the upper limit of clay as ______0.002 mm______.
Any particle smaller than $0.002 \text{ mm}$ is classified as clay.
This corresponds to Statement (A).
- Silt-sized particles: Defined from $0.002 \text{ mm}$ to $0.05 \text{ mm}$ (USDA) or $0.002 \text{ mm}$ to $0.02 \text{ mm}$ (IUSS).
- Sand-sized particles: Defined from $0.05 \text{ mm}$ to $2.0 \text{ mm}$ (USDA) or $0.02 \text{ mm}$ to $2.0 \text{ mm}$ (IUSS).
- Gravel: Particles larger than the sand limit are classified as gravel.
Therefore, the lower limit of gravel (which is the upper limit of sand) is ______2.0 mm______ in both systems.
This corresponds to Statement (D).
Thus, Statements (A) and (D) represent the correct limits across both systems.

Step 2: Final Answer:
The correct option is (D), which includes A and D only.