Question

The soil erosion in which soil matrix is lost but remain undetected for long time.

• A. Rill erosion
• B. Gully erosion
• C. Tunnel erosion
• D. Sheet erosion

Hint:

The key term "remains undetected for a long time" or "silent killer of soil" is the standard diagnostic description for sheet erosion.
It is the most damaging form of water erosion because it targets the organic-matter-rich surface layer.

Answer 1

The Correct Option is D

Water-induced soil erosion is a multi-stage process that removes topsoil through the action of raindrops and surface runoff.
As water moves across a landscape, it strips soil particles away in different patterns.
Some forms of erosion are highly visible, while others occur uniformly across a wide area without leaving distinct physical scars, making them difficult to observe immediately.

Step 2: Detailed Explanation:
Let us analyze the distinct characteristics of the different types of soil erosion:
- Sheet Erosion: This is the uniform, gradual removal of a thin, continuous layer of fertile topsoil from the land surface.
It is triggered by the kinetic energy of raindrop impact (which detaches soil particles) combined with shallow, non-concentrated overland flow (which transports the particles).
Because the soil is removed evenly across the entire field without forming distinct channels or incisions, there are no immediate structural changes visible to the naked eye.
Farmers often do not notice sheet erosion until significant quantities of topsoil are lost, resulting in a gradual, unexplained decline in crop yields and soil fertility.
For this reason, sheet erosion is widely referred to as the "silent killer" of soil resources.
Let us compare this with the other options:
- Rill Erosion: This occurs when overland flow concentrates in micro-channels, carving out small, well-defined channels (rills) that are visible but can be easily removed by normal tillage operations.
- Gully Erosion: This is an advanced stage where rills coalesce and deepen into large, steep-sided ravines (gullies) that cannot be smoothed by ordinary farm machinery. It is highly conspicuous.
- Tunnel Erosion: This is a subsurface erosion process where water percolates through dispersible subsoils, washing away fine particles and forming underground tunnels, which eventually collapse to form sinkholes.

Step 3: Final Answer:
Therefore, sheet erosion is the specific type of soil erosion where the soil matrix is lost uniformly and remains undetected for long periods.