CAPF AC 2025 Q75: Geography – Physical Geography & Geomorphology
Which one of the following is the main method by which potholes are created in bedrocks by the flowing stream?
- (a) Abrasion
- (b) Attrition
- (c) Corrosion
- (d) Solifluction
Answer: (a) Abrasion
Explanation
How potholes form in a stream bed
How to think: a pothole is a round hollow cut in the rock of a stream bed.
Stones and pebbles are whirled round by eddies and grind the bedrock; this grinding by the stream's load is abrasion.
| Process | Meaning |
|---|---|
| Abrasion | Rock load scraping and drilling the bed and banks |
| Attrition | Pebbles wearing each other down into smaller, rounder pieces |
| Corrosion | Chemical solution of rock by water |
| Solifluction | Slow flow of soil over frozen ground, not a stream process |
Answer: (a) Abrasion.
Why each option is right or wrong
- (a) CORRECT. Abrasion by swirling stones carves potholes.
- (b) Incorrect. Attrition wears the load itself, not the bedrock.
- (c) Incorrect. Corrosion is chemical solution, not grinding.
- (d) Incorrect. Solifluction is a slope process in cold regions.
Key point
Stream erosion: hydraulic action, abrasion (corrasion), attrition, solution (corrosion). Potholes and plunge pools are made by abrasion; deep gorges, V-shaped valleys and waterfalls by vertical erosion.
Remember
Potholes come from abrasion: whirling stones drill the bed.
Common mistakes
- Choosing corrosion because it sounds like cutting.
- Mixing up abrasion (of the bed) and attrition (of the load).
- Picking solifluction, a mass-movement term.
Exam tip
Educated guess: solifluction is not a stream process. Of the other three, only abrasion describes a stream tool that drills the bedrock.
Sources
- NCERT Class XI Fundamentals of Physical Geography, Chapter 7 (Landforms and their Evolution: fluvial landforms, potholes)
- Savindra Singh, Geomorphology, chapter on Fluvial Processes and Landforms