Davisian Theory of Cycle of Erosion

Davis Cycle of Erosion:

                    The term cycle of erosion of landform first popularised by American Geomorphologist WM Davis. According to Davis "the geographical cycle is a period of time during which an uplifted landmass undergoes transformation by the process of denudation ending into low featureless plain or peneplain. He propounded the model of complete cycle of river life in his essay 'Rivers and Valleys of Pennsylvania (1889). Under the concept of complete cycle of river life he postulated the cycle concept of progressive development of erosional stream valleys.

According to Davis, three factors play an important role in origin and development of landforms of a particular region. These three factors are called "Trio of Davis". These are-

(a). Sture:

                Rock types, faults, joints inside the rocks, hardness of rocks and permeability of rocks indicates the structure of rock

(b). Process:

                 It includes all the agents of denudation like weathering and erosion, work of water, wind etc.

(b). Time:

               Time was used both in temporal sense and a process, which lead to progression and development of landforms.

Assumptions:

(i). Landforms are evolved and developed by the interaction of endogenetic forces and exogenetic forces.

(ii). There is a short period of rapid upliftment during which the landform is tectonically stable.

(iii). Initial uplift of landform is main sources of potential energy and during the uplift there is no erosion.

(iv). Fluvial erosion erodes the river valleys rapidly and graded is achieved.

(v). Erosion can not occur below the base level, which is the lowest limit of erosion.

Stages of Landform Development:

              Davis presented three stages of landform development. These are discussed below-

(A). Youthful Stage:

                 In the youthful Stage, potential energy is high and river is involved in vertical erosion which increases the depth of river valleys. This stage is actively involved headward erosion. The youthful stage is characterized by rapid rate of vertical erosion and velley depending because..

* Channel gradient is very steep,

* Steep channel gradient increases the velocity and the kinetic energy of the river flow 

* Increased channel gradient and flow velocity increases the eroding and transporting capacity of the river.

         This stage is characterized by V shaped valley, water falls, rapid cataracts, potholes etc.

(B). Mature Stage:

              At the mature Stage, vertical erosion slow down and lateral erosion becomes important. During this stage, mountain tops are eroded first and their heights reduced actively. The floor of the valley however lowered slowly.

               The lateral erosion changes the V shaped valley to U shaped valley (valley widening). A graded profile is formed as most of the streams are reduced and graded to the base level of erosion.

              Meander, U shaped Valleys etc are common landforms of mature Stage.

(C). Old Stage:

               At this stage valley depending is absence totally. But lateral erosion and velley widening dominates. Water divide is quickly eroded and the available potential, kinetic energy is considerably reduced. Extension flood plains are developed in river valleys.

               Thus the valleys become almost flat with convex- concave slopes, graded profiles, broad and gentle sloping valleys and residual hills known as Monadnocks. The entire landscape is known as peneplain, which is a spatially uniform terrains and the end product of Davis Cycle of Erosion.