Some important MCQs related to Geological works by River with detailed explanations -3

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1. What is the primary factor responsible for the formation of meanders in a river?

a) High gradient and fast flow
b) Lateral erosion and deposition
c) Vertical erosion and low gradient
d) Sediment load only

Answer: b) Lateral erosion and deposition
Explanation:
Meanders form due to lateral erosion on the outer bends and deposition on the inner bends of a river, typically in its mature stage. This creates the characteristic winding pattern.


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2. Which of the following is a depositional feature formed at the foot of a slope?

a) Levee
b) Alluvial fan
c) Gorge
d) Waterfall

Answer: b) Alluvial fan
Explanation:
Alluvial fans form when rivers lose velocity and deposit sediment at the base of a slope. They are common in arid regions or mountainous areas.

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3. A distributary is:

a) A branch of a river flowing into the sea
b) A tributary joining the main river
c) A type of floodplain feature
d) A gorge formed by river erosion

Answer: a) A branch of a river flowing into the sea
Explanation:
Distributaries form when a river splits into smaller channels as it deposits sediment at its mouth, typically in a delta region.


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4. Which of these factors does NOT directly influence river erosion?

a) Gradient of the riverbed
b) Velocity of the water
c) Amount of dissolved oxygen in water
d) Sediment load

Answer: c) Amount of dissolved oxygen in water
Explanation:
While oxygen levels impact aquatic ecosystems, they do not directly affect the erosional capacity of a river. Erosion depends on gradient, velocity, and sediment load.


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5. A natural levee is:

a) An artificial embankment built to prevent flooding
b) A raised deposit of sediment along riverbanks
c) A feature formed due to tectonic uplift
d) A deep channel in a river valley

Answer: b) A raised deposit of sediment along riverbanks
Explanation:
Natural levees form during floods when rivers deposit heavier sediments close to their banks, creating elevated ridges.


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6. What is the primary cause of river rejuvenation?

a) Increase in sediment load
b) Sea level rise
c) Change in base level due to tectonic uplift
d) Widening of the river valley

Answer: c) Change in base level due to tectonic uplift
Explanation:
River rejuvenation occurs when a river's base level is lowered, often due to tectonic uplift or a drop in sea level. This gives the river renewed erosional power.





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7. What is the term for a fan-shaped deposit formed where a river meets an ocean?

a) Alluvial fan
b) Delta
c) Point bar
d) Lagoon

Answer: b) Delta
Explanation:
Deltas form where rivers meet oceans or lakes, losing energy and depositing sediments in a fan-like shape. Examples include the Ganges-Brahmaputra Delta.



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8. Which process is responsible for the formation of potholes in a riverbed?

a) Abrasion
b) Hydraulic action
c) Solution
d) Attrition

Answer: a) Abrasion
Explanation:
Potholes are circular depressions formed in the riverbed due to the grinding action of pebbles and sediments in swirling water. This process is a type of abrasion.



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9. Which of the following features is NOT associated with river deposition?

a) Ox-bow lake
b) Point bar
c) Floodplain
d) Gorge

Answer: d) Gorge
Explanation:
A gorge is an erosional feature formed by the vertical cutting of a river into the bedrock, unlike the other features, which are depositional.


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10. The process by which a river reactivates its erosional activity due to base level change is called:

a) Aggradation
b) Rejuvenation
c) Deposition
d) Lateral erosion

Answer: b) Rejuvenation
Explanation:
Rejuvenation happens when the river's base level drops, leading to renewed vertical erosion. This can create terraces and incised meanders.


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