Cycle_of_erosion_after_WM_Davis-Study_Probe

Geomorphology is basically related with the discussion of development and evolution of physical features of earth surface, in terms of landforms and the related topics. It is a sub-discipline of geography.

ADVERTISEMENT

What is erosion cycle?

‘Erosion cycle’ or ‘cycle of erosion’ as it is generally called and as the name depicts, is a cyclic process through which various endogenic and exogenic forces take part to the chronological development and evolution of landforms in a sequential manner.

In the words of eminent British geographer Richard J. Chorley,
The cyclic concept of evolution implied an inevitable, continuous and broadly irreversible progress of change producing an orderly sequence of landform transformation.

A brief history of the theory postulated by Davis


William_Morris_Davis
William Morris Davis
Image courtesy : Wikimedia

In 1859, famous book of Charles Darwin ‘On the Origin of Species by Means of Natural Selection’ was published. That was based on the theme of change or evolution of living species over time. Being highly influenced by Darwin’s theory, in 1884, William Morris Davis first formulated the concept of geomorphic cycle, and this theory was published in the International Geographical Congress in 1889, entitled as ‘Theory of Cycle of Erosion’.

Assumptions

To develop his theory ‘Geographical Cycle of Erosion’, Davis mentioned some basic assumptions.

  • The lithology of the whole area must be homogeneous in type.
  • Upliftment of land occurs rapidly, and erosion process does not take place until the completion of the upliftment process.
  • Davis presumed the notion of crust stability for a long period of time, so that the erosion process could complete in a sequential manner.
  • The area must be pluvial and many rivers must cover the whole land, which will act as the major exogenic force in the process of erosion.

A basic line-out of the Cycle of Erosion Theory by Davis

Davis presented his theory as a genetic classification and a sequential transformation of landforms.

According to him,
Geographical cycle is a period of time during which an uplifted landmass undergoes its transformation by the process of land sculpture ending into low featureless plain called peneplain or peneplane... Three factors viz., structure, process, and stage play important role in the origin and development of landforms of a particular place.

These three factors of landform transformation are basically known as ‘Trio of Davis’.

ADVERTISEMENT

Davis explained his whole cyclic theory through three stages.

1. Youth Stage

In this stage, potential energy (m×g×h) maximises due to the maximum upliftment of the landscape. Some consequent streams and their tributaries primarily take part in the erosion process and develops ‘V’-shaped river valley. There exists no flood-land, and water-divider is one of the most prominent features in this stage. In this primary stage, cascades may develop within the way of river-flow. River meander is a rare feature that develops based on the primary ridges and slopes. Bottom erosion of river is the main erosional process in the youth stage.

Cycle_of_erosion_by_Davis-Study_Probe
Fig.: Graphical presentation of Geographical Cycle presented by W.M. Davis

2. Mature Stage

Gradually the landscape evolves towards the mature stage. Surface roughness maximises and various drainage patterns become prominent in this stage, and accordingly side erosion by river majorly takes part rather than the bottom erosion. Wide flood-plain develops in the mature stage which results the water-dividers to become less prominent. The width of the valley floor almost resembles with the width of the meander belt.

Stages_of_erosion_by_Davis-Study_Probe
 Fig.: Stages of Erosion of a Landscape

3. Old Stage

Chronologically the landform get to its old stage when the river valley floor becomes extremely wide and develops almost a plain land, which Davis identified as ‘Peneplain’. In this stage the landscape comes to its base level of erosion. Two most important and prominent features of old stage of erosion are ‘Monadnock’ and ‘Oxbow Lake’. Monadnock are the remaining part of the eroded water-dividers, and in the other side, oxbow lake develops when a river intersects its well-formed curves and flows in a straight line.

Criticism of the Davisian Model of Geographical Cycle

Though Davis was the first to explain the erosion cycle of landforms by a simplified model, critiques have highlighted some negative points of his theory.

  • First of all, theory of  Davis was highly criticized because of its excessive generalization.
  • Previously mentioned second assumption of Davis that land uplifts rapidly and erosion does not take place until its completion –is quite baseless. There is no assurance about this assumption. Landscape may uplift during the erosion process, that means both of upliftment and erosion can take part in the evolution of landforms at the same time.
  • Davis stressed upon the closed system of entropy (En = Inside, Trope = Transformation) maximization. But geomorphic process is a part of open system.
  • Davis did not illuminate in his theory about the meteorological disturbances in the way of erosion cycle, as well as the dynamism of the landscapes.


Thus further developed theories of landscape evolution by Chorley, Schumm, Hack and others, quite obscured the Davisian theory of erosion, as they stressed on the functional equilibrium, which is much more realistic and rational, rather than that of the stages mentioned by Davis.




Related Article

Study Probe | Theory of Landscape Evolution by Penck – Main Theory | Evaluation

Post a Comment

Please do not enter any spam link in the comment box

Previous Post Next Post