Cycle of Erosion

William Morris Davis proposed a concept of Geographical cycle of erosion in 1889. This theory is also known as peneplanation or slope decline theory.It is a most popular theory of land development. He provided Genetic classification and systematic description of land forms. Davis introduced the idea of recognizable landscape and their stages of evolution in his cyclic mode stating that

“ Landscape is a function of structure, process and stages”

1. Structure : which include ‘nature’(hardness, permeability) and attitude(fold, fault and joints) of rocks.
2. Process: process implies the factors or agents responsible for weathering and erosion.
3. Time: Implies the stage at which the cycle is – Youth, Maturity and old age.

Basic principle of Davis theory

1. Land forms like organic forms shall be studied in view of their evolution.
2. The land forms initial uplift is the chief source of energy in the form of potential energy
3. Throughout the land form assemblage, leading ultimately to a spatially uniform terrain which Davis called Peneplain.
4. While the landmass is being uplifted there is very little or no erosion.
5. Uniform Lithology
6. Davis divided stages into Youth, mature and old.

Davis defined a geographical cycle as that, “ The sequence if changes which an uplifted block has to undergo before it gets reduced to base level or peneplane.”

Youthful stage

• Erosion starts after completion of uplift for landmass
• It is a vertical erosion
• The top surfaces or summits of water divided are not affected by erosion
• because the rivers are small.
• Small rivers and short tributaries are engaged in head ward erosion due to
• which they extend their length
• Because of steep slope and steep channel gradient rivers actively deepen
• their valleys through vertical erosion
• The valley becomes deep and narrow

Maturity stage

• It has lateral erosion
• Lateral erosion leads to valley widening
• Youth will turn into Mature depends to a large extent on the texture
• of the drainage
• The marked reduction in the valley deepening is due to substantial
• decrease in channel gradients, flow velocity and transporting capacity of rivers.

Old age

• Gentle gradient accentuated by horizontal action and deposition,
• reduces the erosion intensity
• Absence of valley incision but lateral erosion and valley widening is
• still active process.
• Water divides are more rapidly eroded
• rapid decrease in absolute height.