Test: Landforms And Their Evolution - UPSC MCQ

Cirques are defined as deep, long troughs or basins found at the heads of glacial valleys. They are characterized by steep, concave walls and often contain small lakes known as tarns, which form after the glacier melts. An interesting fact about cirques is that they can lead to the formation of multiple cirques in a stepped sequence, creating stunning visual landscapes in mountainous regions.

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

• 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. 

1. Youth Stage of Landform - Initial Stage of Development
This is correctly matched. In the youth stage, the landform is in its initial stage of development.

2. Mature Stage of Landform - Peak of Erosional Activities
This is correctly matched. In the mature stage, erosional activities are at their peak, and the landscape is more defined with valleys and hills.

3. Old Stage of Landform - Formation of New Landforms
This is incorrectly matched. The old stage is characterized by reduced erosion and more deposition leading to flatter terrains, not the formation of new landforms.

4. Running Water - Primary Agent in Arid Regions
This is incorrectly matched. Running water is a primary agent in regions with high humidity and heavy rainfall, not in arid regions where wind is more dominant.

Geomorphology is the scientific discipline dedicated to understanding landforms and the processes that create and modify them. It examines various agents of change, such as water, wind, ice, and tectonic activity. By studying these elements, geomorphologists can reveal how landscapes evolve, the factors influencing these changes, and the resulting erosional and depositional features. This knowledge is crucial for environmental management and predicting geological hazards.

• 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: Incorrect. A canyon is typically a deep, narrow valley with steep sides, but it is not typically described as having step-like sides.

Explanation: In regions with high humidity and heavy rainfall, running water is the primary agent responsible for the erosion and shaping of land surfaces through processes like overland flow and stream erosion.

Alluvial fans are primarily characterized as broad, cone-shaped deposits formed when streams carrying coarse materials break onto low-gradient plains. This type of landform occurs as the streams lose energy and deposit their load in a fan-like shape. In humid areas, these fans typically have gentle slopes, while they appear steeper in arid regions. An interesting fact about alluvial fans is that they can evolve over time as streams shift their courses, creating a complex network of distributary channels.

Drumlins are primarily composed of glacial till, which is a mixture of clay, silt, sand, gravel, and boulders that have been deposited by glacial action. Their oval shape and alignment indicate the direction of glacial movement, as the ice pushes the till into streamlined ridges. An interesting fact about drumlins is that they can vary significantly in size and shape, which helps geologists understand past glacial activity and the dynamics of ice flow.

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

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, and 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.

• 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. .

Statement 1: Stalactites are indeed icicle-shaped formations that hang from the ceilings of limestone caves. When carbonated water, rich in dissolved calcium carbonate, seeps through the ceiling of a cave and evaporates, it leaves behind calcium carbonate deposits that form stalactites. This statement is correct.

Statement 2: Stalagmites are formations that rise from the floor of a cave, typically forming directly beneath stalactites. They are created by the dripping of water from the ceiling, which deposits calcium carbonate as it evaporates on the ground. This statement is correct.

Statement 3: While glaciers do experience some melting at their bases, their primary movement is due to the force of gravity acting on the mass of ice, causing it to flow slowly downhill. This statement oversimplifies the process and is not entirely accurate. Therefore, this statement is incorrect.

Thus, the correct answer is Option B: 1 and 2 Only.

1. Statement 1 is correct. During the youth stage of landscape development in running water regimes, streams do indeed have poor integration and flow over original slopes. This stage typically features shallow V-shaped valleys and minimal floodplains.
2. Statement 2 is incorrect. In the mature stage, the stream divides are sharp and not broad and flat. Broad and flat stream divides with marshes, swamps, and lakes are characteristics of the youth stage, not mature.
3. Statement 3 is correct. The old stage of landscape development is indeed characterized by streams meandering freely over vast floodplains, creating features such as natural levees and oxbow lakes. At this stage, the landscape is mostly at or slightly above sea level.
Thus, the correct statements are 1 and 3, making Option C: 1 and 3 Only the correct answer.

Landforms progress through three distinct stages: youth, mature, and old. In the youth stage, landforms are typically characterized by sharp features and steep gradients, while 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.