Test: Landforms And Their Evolution - UPSC MCQ

• Statement i: Correct. Limestone pavement consists of blocks (clints) and fissures (grikes) formed by erosion.
• Statement ii: Correct. Karst topography is characterized by features like sinkholes and caves, formed by the dissolution of soluble rocks.
• Statement iii: Correct. An alluvial fan is formed when a stream's velocity decreases, depositing sediments in a fan shape.
• Statement iv: Correct. Potholes are circular depressions in rock beds formed by the swirling action of water and sediment.

• Assertion correctly describes the process of valley formation through the progression from small rills to wide valleys.
• Reason is also accurately highlights the pattern of erosion in streams with steep gradients, emphasizing erosion concentration at the channel bottom. However, Reason does not directly explain the Assertion. 

• A barrier bar is a ridge of sand and shingle that forms parallel to the coastline.
• Typically, these formations become exposed during low tide.
• Barrier bars often occur at river mouths or bay entrances.
• They act as natural barriers that can protect coastal areas from wave action.
• Barrier bars play a crucial role in coastal dynamics.
• They help to create lagoons and significantly influence sediment deposition patterns.
• Interestingly, barrier bars serve as vital buffers against storm surges.
• They absorb much of the wave energy during extreme weather events.

• Landforms progress through three distinct stages: youth, mature, and old.
• In the youth stage, landforms are typically characterized by sharp features and steep gradients.
• In the mature stage, they often have more rounded features due to erosion.
• In the old stage, landforms may appear flat and exhibit minimal change.
• This classification helps geologists and geomorphologists understand the lifecycle of various landforms and the processes that shape them.

• Incised or entrenched meanders are formed as streams cut deeply into their valleys.
• They often develop over original gentle surfaces.
• This process can lead to the formation of deep gorges and canyons.
• This is particularly notable in hard rock areas.
• Streams experience significant vertical erosion.
• This contrasts with meanders in low-gradient streams.
• Low-gradient streams typically develop through lateral erosion.
• An interesting fact is that the presence of these entrenched meanders provides insights into historical geological processes.
• These processes shaped the landscape.

• Statement I is true as glaciers erode the land through processes like plucking and abrasion, creating U-shaped valleys.
• However, Statement II is false because U-shaped valleys are primarily formed by glaciers, not rivers, which typically form V-shaped valleys in softer sediments.

• Assertion is correctly defines river terraces as surfaces indicating old valley floor or floodplain levels.
• This results from erosion caused by vertical erosion by the stream into its own depositional floodplain. This aligns with the information provided in the text about river terraces.
• Reason describes alluvial fans as deposits formed when streams carrying coarse load break into low-gradient foot slope plains. .

• Running water is identified as the primary geomorphic agent in regions characterized by high humidity and heavy rainfall.
• This process occurs through two main types of water flow:
  • Overland flow, which spreads across the surface,
  • Linear flow, which occurs in streams and rivers.
• The continuous movement of water facilitates erosion and deposition, shaping the landscape over time.
• Interestingly, the rate of erosion and deposition can significantly alter the topography,
• leading to features like flat plains, valleys, and various landforms.

• Statement i: Correct. Braided channels are indeed formed by the deposition of coarse materials in a network of channels.
• Statement ii: Incorrect. Stalactites hang from the ceiling of caves, not rise from the floor (that would be stalagmites).
• Statement iii: Correct. Sinkholes are depressions typically formed by the collapse of surface layers in limestone regions.
• Statement iv: Correct. A peneplain is a nearly level plain formed through prolonged erosion.

The correct sequence follows the progressive evolution of landforms: rills form first, which then develop into gullies, eventually leading to valley formation. With continued erosion and deposition, these features can eventually result in the formation of a peneplain.

Both the assertion and the reason are correct. Groundwater erodes limestone primarily through solution, and this is due to the solubility of calcium carbonate (the main component of limestone) in carbonated water, leading to the formation of caves.

The assertion is true; unpaired terraces can indeed form on only one side of the river. However, the reason is false because unpaired terraces are often due to uneven uplift or differential erosion, not uniform tectonic uplift.

• Statement i: Correct. A peneplain is a nearly level plain formed by prolonged erosion over a large area.
• Statement ii: Correct. A gorge is a deep valley with steep sides, often formed by river erosion.
• Statement iii: Correct. A plunge pool is a deep hole at the base of a waterfall formed by the impact of water.
• Statement iv: correct. A canyon is a large, deep valley with steep sides, usually wider at the top and narrower at the bottom, often formed by river erosion.

• Peneplain corresponds to a nearly flat landform formed by prolonged erosion (ii).
• Canyon is a deep valley with steep sides formed by river erosion (i).
• Sinkhole is a circular depression formed due to the collapse of a cave (iii).
• Alluvial Fan is a cone-shaped deposit formed at the base of a mountain slope by streams (iv).

• Statement i: Correct. Stalactites hang from the ceiling of caves, formed by the deposition of calcium carbonate.
• Statement ii: Correct. Sinkholes are depressions caused by the collapse of a surface layer, typically in limestone regions.
• Statement iii: Correct. Braided channels consist of a network of small channels separated by islands.
• Statement iv: Incorrect. While a monadnock is an isolated hill, it is not necessarily related to peneplains as described.