Question

Which of the following events is/are generally associated with the formation of Dun valleys?

• A. Formation of a temporary lake due to the accumulation of water when a river encounters an obstacle
• B. The river may find weak rocks in the mountain that erode and provide a gap for the water to pass
• C. The water which was accumulated due to obstacle flows forward leaving behind a dry lake
• D. Tropical cyclones, developed in the Bay of Bengal, advance towards northern plains

Answer 1

Answer: (A), (B), (C)

The correct options are
A Formation of a temporary lake due to the accumulation of water when a river encounters an obstacle
B The river may find weak rocks in the mountain that erode and provide a gap for the water to pass
C The water which was accumulated due to obstacle flows forward leaving behind a dry lake

When a river encounters an obstacle in its course, for instance, a mountain, may cause the river water to accumulate on one side of the mountain, forming a temporary lake. Overtime, sediments like thick gravel and alluvium will accumulate at the bottom of such lakes. Eventually, the river may find weak rocks in the mountain that erode and provide a gap for the water to pass. Then, the accumulated water will flow forward again leaving behind a dry lake or a dun valley in its place.