CAPF AC 2021 Q39: Geography – Physical Geography & Geomorphology
In the course of a river, in time, which one of the following features is formed when the old meander is closed off by deposition?
- (a) Pothole
- (b) Levee
- (c) Oxbow lake
- (d) Flood plain
Answer: (c) Oxbow lake
Explanation
How an oxbow lake forms
How to think: the question describes a meander that gets cut off.
A cut-off meander holds water and looks like a horseshoe.
That is an oxbow lake.
Steps:
| Step | What happens |
|---|---|
| 1 | In the plains the river swings in big loops called meanders |
| 2 | Erosion on the outer bank brings the two ends of a loop closer |
| 3 | In a flood the river cuts straight through the narrow neck |
| 4 | Deposition seals off the old loop, leaving an oxbow lake |
The other features:
| Feature | How it forms |
|---|---|
| Pothole | Drilled into the rocky bed by pebbles in the upper course |
| Levee | Raised bank built by deposits during floods |
| Flood plain | Flat land covered with silt when the river overflows |
Answer: (c) Oxbow lake.
Why each option is right or wrong
- (a) Incorrect. A pothole is an erosional hollow in the rocky bed of a young river.
- (b) Incorrect. A levee is a natural embankment along the river bank.
- (c) CORRECT. A cut-off meander sealed by deposition forms an oxbow lake.
- (d) Incorrect. A flood plain is the wide flat area of silt on both sides of the river.
Key point
Meander → narrow neck → cut-off → oxbow lake. Erosional features: V-shaped valley, gorge, waterfall, pothole. Depositional features: flood plain, levee, delta. Oxbow lake is linked with meanders.
Remember
Cut-off meander = oxbow lake.
Common mistakes
- Mixing up a levee (raised bank) with an oxbow lake (cut-off loop).
- Thinking an oxbow lake is made only by erosion; deposition seals it off.
- Placing oxbow lakes in the mountain course; they belong to the plains.
Exam tip
Educated guess: the clue word is meander. Among the options only the oxbow lake is a meander that has been left behind.
Sources
- NCERT Class VII Geography — Our Changing Earth (work of a river)
- NCERT Class XI Geography — Fundamentals of Physical Geography (Landforms and their Evolution: running water)