Geomorphic Cycle – UGC NET Geography Notes

Geomorphic Cycle: The geomorphic cycle, also known as the cycle of erosion, is a fundamental concept in geomorphology that explains the progressive transformation of landforms due to exogenic and endogenic forces. Proposed by William Morris Davis, this model classifies landscape evolution into three stages: youth, maturity, and old age, driven by fluvial, glacial, aeolian, and marine processes. The concept helps in understanding how denudation, erosion, and deposition shape the Earth’s surface over geological time.

For UGC NET Geography aspirants, mastering the geomorphic cycle is essential, as it forms a key part of physical geography. While Davis’ model remains influential, alternative theories such as Walther Penck’s slope evolution model and Julius Büdel’s polycyclic landscape theory offer different perspectives on landscape development. This article covers the stages, factors, and criticisms of the geomorphic cycle, providing a comprehensive resource for UGC NET exam preparation.

What is the Geomorphic Cycle?

• The geomorphic cycle, or cycle of erosion, is a concept by William Morris Davis that explains the systematic evolution of landforms through youth, maturity, and old age under the influence of erosional and depositional forces.
• It highlights how landscapes undergo continuous transformation due to internal (endogenic) and external (exogenic) processes over geological time.

Exogenic vs. Endogenic Processes

• Exogenic Processes: External forces like erosion, weathering, and deposition, driven by rivers, glaciers, wind, and waves, gradually reshape the land.
• Endogenic Processes: Internal forces such as tectonic uplift, volcanic activity, and folding, create landforms that later undergo modification by exogenic agents.
• Major Geomorphic Agents
  • Rivers erode valleys and form floodplains.
  • Glaciers carve U-shaped valleys and deposit moraines.
  • Wind sculpts deserts through deflation and dune formation.
  • Waves shape coastal features like cliffs and beaches.

This cycle plays a key role in UGC NET Geography, providing insights into landform development and the interaction of geomorphic forces.

Stages of the Geomorphic Cycle (Cycle of Erosion)

The geomorphic cycle, proposed by William Morris Davis, describes how landforms evolve through three sequential stages under the influence of erosional processes.

1. Youth Stage

• Characterized by high relief, steep slopes, and deep valleys.
• Rivers actively erode, creating V-shaped valleys, waterfalls, and rapids.
• Land is rugged with minimal deposition.

2. Mature Stage

• Erosion reduces slope steepness, forming wider valleys and floodplains.
• Rivers develop meanders, and landscape stability increases.
• Landforms begin approaching dynamic equilibrium between erosion and deposition.

3. Old Age

• Low relief with gentle slopes and extensive floodplains.
• Slow erosion leads to the formation of a peneplain (almost levelled landform).
• Features like oxbow lakes, deltas, and meandering rivers dominate.

Also Check: Denudation and Weathering

Theories of Geomorphic Cycle

Several theories explain landscape evolution, with notable contributions from William Morris Davis, Walther Penck, and Julius Büdel. These models differ in their emphasis on erosion, tectonics, and climatic influences.

William Morris Davis’ Geomorphic Cycle

• Proposed the Cycle of Erosion, explaining landform evolution through youth, maturity, and old age.
• Highlights the role of tectonic uplift, followed by gradual erosion shaping the landscape.
• Assumes a sequential and time-dependent evolution under uniform climatic conditions.

Walther Penck’s Slope Evolution Model (secondary keyword)

• Criticized Davis’ model for being too rigid and ignoring continuous uplift.
• Emphasized endogenic forces (tectonics) as a dominant factor in landform development.
• Proposed that landforms evolve through waxing, steady-state, and waning slopes, focusing on simultaneous uplift and erosion.

Julius Büdel’s Polycyclic Landscape Theory (secondary keyword)

• Argued that landforms undergo multiple erosion cycles rather than a single sequential cycle.
• Stressed climatic variations as a key factor in landscape evolution.
• Explained that polycyclic landforms result from repeated cycles of uplift and erosion under changing environmental conditions.

Factors Influencing the Geomorphic Cycle

The evolution of landforms in the geomorphic cycle is influenced by several key factors, including climate, rock structure, and tectonic activity. These factors determine the rate and nature of erosion, deposition, and landform development over time.

1. Climatic Conditions

• Temperature fluctuations affect weathering (e.g., frost action in cold regions).
• Precipitation controls the intensity of fluvial erosion and sediment transport.
• Wind plays a major role in aeolian processes, shaping deserts and coastal landscapes.

2. Lithology and Rock Structure

• Harder rocks like granite resist erosion, forming highlands, while softer rocks like limestone erode faster, creating valleys and karst landscapes.
• Rock fractures, joints, and bedding planes influence the formation of ridges, cliffs, and plateaus.

3. Tectonic Activity and Base Level Changes

• Tectonic uplift rejuvenates landscapes, increasing erosion rates and creating youthful landforms.
• Subsidence leads to sediment deposition and the formation of coastal plains.
• Changes in base level (sea level rise or fall) influence river incision, terrace formation, and delta development.

Criticism and Limitations of the Geomorphic Cycle

While Davis’ Geomorphic Cycle was a pioneering theory in landform evolution, it has faced several criticisms from modern geomorphologists due to its static approach and oversimplifications.

1. Static Nature of Davis’ Model

• Assumes a linear, sequential evolution of landscapes, ignoring ongoing tectonic activity.
• Does not account for continuous uplift or erosion occurring simultaneously, as suggested by Penck’s model.

2. Lack of Consideration for Climate Variability

• Treats climate as a constant factor, failing to incorporate climatic changes over geological time.
• Büdel’s polycyclic theory highlighted how landforms undergo multiple cycles due to climate shifts.

3. Alternative Perspectives in Modern Geomorphology

• Dynamic equilibrium concept suggests that landforms evolve in response to balancing forces of uplift and erosion rather than fixed stages.
• Tectonic geomorphology and process-based models focus on real-time landscape changes rather than long-term hypothetical cycles.

Despite its limitations, the geomorphic cycle remains a foundational concept in UGC NET Geography, helping understand the basics of landform evolution.

Also Learn: Concept of Continental Drift Theory

Importance of the Geomorphic Cycle in UGC NET Geography

The geomorphic cycle is a crucial topic in UGC NET Geography, as it forms the foundation for understanding landform evolution, erosion, and geomorphic processes. Questions related to this topic often appear in both conceptual and applied formats in the exam.

Expected UGC NET Exam Questions

• Conceptual Questions: Definitions, stages of the geomorphic cycle (youth, maturity, old age), and theories by Davis, Penck, and Büdel.
• Applied Questions: Role of climate, tectonics, and rock structure in landform development.
• Comparative Questions: Differences between Davis’ model and alternative theories like Penck’s slope evolution model.

How to Approach MCQs Related to Geomorphic Processes?

• Focus on key terminologies like peneplain, equilibrium, uplift, exogenic, and endogenic processes.
• Understand cause-effect relationships, such as how tectonic uplift influences erosion rates.
• Analyze diagram-based questions, which often test knowledge of landform evolution stages.
• Practice previous year UGC NET Geography papers to identify frequently asked patterns.

Also Check: UGC NET Geography Previous Year Questions Papers

Geomorphic Cycle Conclusion

The geomorphic cycle remains a foundational concept in geomorphology, explaining the evolution of landforms through erosion, deposition, and tectonic processes. While Davis’ model provides a structured framework, modern theories by Penck and Büdel offer alternative perspectives, incorporating tectonic activity and climatic variations.

For UGC NET Geography, understanding the stages, factors, and criticisms of the geomorphic cycle is essential. Exam questions often test conceptual clarity, theoretical comparisons, and application-based scenarios. A strong grasp of geomorphic processes enhances performance in physical geography sections, ensuring better accuracy in tackling MCQs and analytical questions.