NDA (II) 2021 GAT Q85: Which one of the following features is the result of

Q: What is the answer to NDA (II) 2021 GAT Q85?

B. Correct — B, oxbow lake. An oxbow lake is the classic feature made by BOTH erosion and deposition of a river: as a meander loop grows, the river erodes through the narrow neck of the loop, and deposition then seals off the abandoned bend, leaving a crescent-shaped lake beside the channel. A pothole and a rapid are cut purely by erosion, while a levee is built purely by deposition — only the oxbow lake needs the two processes working together.

NDA (II) 2021 General Ability Test · Question 85 of 149

Question text verified against the official NDA question paper.

Which one of the following features is the result of erosion and deposition work of a river?

(a)Pothole
(b)Oxbow lake
(c)Levee
(d)Rapid

Answer

Why

Correct — B, oxbow lake. An oxbow lake is the classic feature made by BOTH erosion and deposition of a river: as a meander loop grows, the river erodes through the narrow neck of the loop, and deposition then seals off the abandoned bend, leaving a crescent-shaped lake beside the channel. A pothole and a rapid are cut purely by erosion, while a levee is built purely by deposition — only the oxbow lake needs the two processes working together.

Why the others are wrong

(a)Pothole — A pothole is a bowl-shaped hollow drilled into the river bed by abrasion — an erosional feature only.
(c)Levee — A levee is a raised bank built along a river by sediment deposited during floods — a depositional feature only.
(d)Rapid — A rapid is a turbulent, fast stretch formed where the river erodes hard and soft rock unevenly — erosional, not depositional.

Concept

A river shapes landforms by erosion (cutting and removing rock and sediment) and by deposition (dropping sediment where its energy falls). Most landforms are the work of one process; the oxbow lake is special because it needs both — erosion to cut off a meander neck and deposition to seal the loop into a standalone lake.

The question asks for the ONE feature that combines both processes. Classify each option as erosional (pothole, rapid), depositional (levee) or both (oxbow lake).

Key facts

An oxbow lake is a cut-off meander loop, crescent-shaped.
It forms when erosion breaches the meander neck and deposition seals off the loop.
It is also called a cut-off lake or mortlake, common on the floodplains of mature rivers.
Potholes and rapids are erosional; levees and floodplains are depositional.

Aerial view of a meandering river with a looping bend and cut-off oxbow lake on a floodplain — A cut-off meander loop — formed by a river's erosion of the neck and deposition sealing the bend.Image: Anthony Stevenson · Wikimedia Commons (CC BY-SA 2.0)

Study next

Meanders and lateral erosion of riversFloodplains and natural leveesRiver deltas and depositional landformsWaterfalls, gorges and potholesYouthful, mature and old stages of a river

Common traps

Calling an oxbow lake purely depositional or purely erosional.
Confusing a levee (deposition) with an oxbow lake (both processes).

Asked as the landform produced by both the erosion and the deposition work of a river — the oxbow lake.

Related PYQs

No directly related past PYQ was found.

Practice

practice — not a real PYQ
An oxbow lake is formed by the
- (a)deposition of a glacier
- (b)cutting off of a river meander
- (c)action of sea waves
- (d)wind erosion in a desert
Answer(b) cutting off of a river meander — erosion breaches the neck and deposition seals the loop.
practice — not a real PYQ
Which one of the following is a purely depositional landform of a river?
- (a)Pothole
- (b)Rapid
- (c)Natural levee
- (d)Gorge
Answer(c) Natural levee — a raised bank built up by sediment deposited during floods.