Question

The diameter of fine particle in sand fraction according to USDA is:

• A. 0.25-0.10 mm
• B. 0.50-0.25 mm
• C. 0.05-0.002 mm
• D. 2.00-1.00 mm

Hint:

Rank the USDA sand subclasses by size from coarse to fine.

Answer 1

The Correct Option is A

This question is testing the USDA particle size scale used to name the sand subclasses in soil texture work.

1. 0.25-0.10 mm: this is exactly the size window the USDA assigns to fine sand, so this is the answer.
2. 0.50-0.25 mm: this range belongs to medium sand, one step coarser than fine sand.
3. 0.05-0.002 mm: particles this small no longer count as sand at all, this is the silt range.
4. 2.00-1.00 mm: this is the coarsest sand subclass, very coarse sand, far from the fine end of the scale.

Running down the USDA scale from largest to smallest gives very coarse sand, coarse sand, medium sand, fine sand and very fine sand, with fine sand sitting at 0.25 mm to 0.10 mm.

Let's summarize:

• The USDA scale grades sand into five subclasses purely by particle diameter.
• Fine sand is defined as 0.25 mm to 0.10 mm, smaller than medium sand and larger than very fine sand.

So the correct diameter range for fine sand is 0.25-0.10 mm, option 1.