Sample Solution

BGGCT-131 Solved Assignment 2024

Part-A All Questions are compulsory and carries 10 marks each. 1) Discuss the different layers of Earth's interior with the help of a neat sketch.

Answer:

The Earth's interior is composed of several distinct layers, each with its own composition, properties, and behavior. These layers are differentiated based on their chemical composition, physical state, and depth from the surface. The main layers of Earth's interior are the crust, mantle, outer core, and inner core.

1. Crust:

   • The crust is the outermost layer of the Earth and is composed primarily of solid rock.
   • It is divided into two types: continental crust, which is thicker and less dense, and oceanic crust, which is thinner and more dense.
   • The crust is the thinnest layer, ranging from about 5 to 70 kilometers thick.

2. Mantle:

   • The mantle is the layer beneath the crust and extends to a depth of about 2,900 kilometers.
   • It is composed mainly of solid rock but can flow over long periods of time due to high temperature and pressure.
   • The mantle is divided into the upper mantle and the lower mantle, with the boundary between them known as the mantle transition zone.

3. Outer Core:

   • The outer core is a layer of molten iron and nickel that surrounds the inner core.
   • It is responsible for generating Earth's magnetic field through the process of convection and the movement of electrically conductive materials.
   • The outer core is about 2,300 kilometers thick and extends from a depth of about 2,900 kilometers to 5,150 kilometers.

4. Inner Core:

   • The inner core is the innermost layer of the Earth and is composed primarily of solid iron and nickel.
   • It is under immense pressure, causing it to remain solid despite the high temperatures.
   • The inner core is about 1,200 kilometers in radius and is surrounded by the outer core.

These layers are dynamic and interact with each other in complex ways, influencing the Earth's geological processes, magnetic field, and surface features. The study of Earth's interior layers provides valuable insights into the planet's history, formation, and ongoing evolution.

2) Critically discuss the concept of Cycle of erosion of Penck.

Answer:

1. Introduction to Penck's Cycle of Erosion

The cycle of erosion, developed by Walther Penck in the early 20th century, is a geomorphological model that describes the long-term evolution of landscapes through a series of stages. Penck proposed that landscapes undergo a cyclical process of erosion and deposition, driven by tectonic uplift, weathering, and erosion. The model suggests that landscapes progress from a youthful stage to a mature stage, then to an old age stage, before rejuvenating and starting the cycle again.

2. Stages of Penck's Cycle of Erosion

Youth Stage:

• In the youth stage, a landmass experiences tectonic uplift, leading to the formation of a peneplain, a nearly flat, low-relief surface.
• Erosional processes, such as rivers and glaciers, start to dissect the peneplain, forming valleys and other landforms.

Maturity Stage:

• As erosion continues, the landscape becomes more dissected, and relief increases.
• Rivers and other erosional agents continue to shape the landscape, forming a more complex network of valleys and hills.

Old Age Stage:

• In the old age stage, the landscape becomes highly dissected, with steep valleys and rugged terrain.
• The peneplain is transformed into a highly varied landscape, with significant relief and distinct landforms.

Rejuvenation:

• Rejuvenation occurs when tectonic forces uplift the landmass again, starting a new cycle of erosion.
• The landscape begins to evolve once more, progressing through the stages of youth, maturity, and old age.

3. Criticisms of Penck's Cycle of Erosion

Simplistic Nature:

• Critics argue that the cycle of erosion model is overly simplistic and fails to account for the complexity of geomorphic processes.
• The model assumes a linear progression through stages, which may not accurately represent how landscapes evolve.

Neglect of External Factors:

• Penck's model neglects the influence of external factors such as climate, vegetation, and human activity on landscape evolution.
• These factors can significantly impact erosion rates and landform development, leading to deviations from the idealized cycle.

4. Modern Perspectives on Landscape Evolution

Non-Cyclical Models:

• Modern geomorphological research has shown that landscapes do not always follow a cyclical pattern of erosion and deposition.
• Landscapes can evolve in a non-linear fashion, with multiple factors influencing their development.

Importance of Variability:

• The variability of landscapes is now recognized as a key aspect of their evolution, with different regions experiencing unique patterns of erosion and deposition.
• Factors such as climate change, tectonic activity, and human intervention can all play significant roles in shaping landscapes.

5. Conclusion

In conclusion, while Penck's cycle of erosion has been influential in shaping our understanding of landscape evolution, it is now viewed as a simplified model that does not fully capture the complexity of geomorphic processes. Modern geomorphological research emphasizes the variability and non-linearity of landscape evolution, highlighting the importance of considering a wide range of factors in understanding how landscapes change over time.