Question

Soil particles size in suspension phenomenon during wind erosion is

• A. $<0.1$ mm
• B. $0.1 - 0.5$ mm
• C. $0.5 - 1.0$ mm
• D. $>1.0$ mm

Hint:

Mnemonic for Wind Movement:
Suspension (Smallest) $<$ Saltation (Small-Medium) $<$ Creep (Coarse).
Saltation is the "engine" of wind erosion that triggers the other two.

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The question asks for the specific diameter range of soil particles that move through the air via the "suspension" mechanism during wind erosion.
Detailed Explanation:

• Mechanisms of Wind Erosion:
Wind moves soil particles in three distinct ways depending on their size and weight:
Saltation: Medium-sized particles ($0.1$ to $0.5$ mm) "bounce" or "jump" along the surface. This is the most dominant form of movement ($50-75\%$ of total erosion).
Surface Creep: Larger particles ($0.5$ to $2.0$ mm) are too heavy to be lifted. They roll or slide along the ground.
Suspension: Very fine particles are lifted high into the atmosphere and can travel thousands of kilometers.

• Characteristics of Suspension:
Particles in this category are generally smaller than $0.1$ mm in diameter (often cited as $<0.05$ mm for silt and clay).
Once lifted by the wind or kicked up by saltating particles, these fines remain airborne because the upward force of air turbulence exceeds their settling velocity (gravity).
While suspension only accounts for about $3-15\%$ of total soil loss by weight, it is the most visible form (dust storms) and represents the loss of the most fertile particles (clay and organic matter).

• Size Thresholds:
Particles $>0.1$ mm are generally too heavy to stay suspended for long periods without falling back to the surface.

Step 2: Final Answer:
Suspension involves the movement of the finest soil particles, typically characterized by a size of less than $0.1$ mm.