Penck’s Erosion Cycle
According to Penck, “The phase and rate of upliftment of landforms and the sum of mutual relations in degradation are intertwined.” Mr. Penck has observed upliftment occurring at different rates and has divided the stages of evolution of landforms into three parts, as follows:
- Afasti Jinde Intiwak Lung – In this stage, the topography uplifts rapidly, making it the first stage.
- Gleikhpharming Intivac Lung – In this stage, upliftment occurs at a uniform speed, hence its name as the middle stage.
- Anbasti Jinde Intiwak Lung – The rate of upliftment decreases in this stage, as shown by the last condition.
Penck’s erosion cycle begins with upliftment and continues until the end of the process of erosion, even after the upliftment has ended. Mr. Penck has identified erosion occurring in the following five situations:
- In the first stage, both upliftment and erosion occur simultaneously, but upliftment is more pronounced, resulting in flat doabs between the rivers that are rarely eroded.
- In the second stage, upliftment and erosion are predominant, causing valleys to flatten quickly. Although the upliftment of the doab and the erosion of the valley occur in this stage, the vertical erosion of the valley remains slow due to the difference between the deepening of the valley and the slow rise of the doab.
- The third stage is a competition between upliftment and erosion, resulting in upliftment being more than erosion and erosion being more than upliftment. There is no significant difference between the processes of upliftment and erosion in this stage.
- In the fourth stage, the speed of upliftment decreases significantly, and the rate of erosion remains the same, causing river valleys to deepen and the land in the doab of the rivers to become more low-lying due to erosion.
- The fifth and last stage of Penck’s erosion cycle is characterized by a slowing of both upliftment and erosion. In the valleys of the rivers, hilly mounds become raised pointed parts and rounded sunken parts, resulting in a decrease in both height and depth. This stage is known as old age.
Mr. Penck illustrated this erosion cycle by drawing two curves on a graph, with the upper and maximum mean height and the lower curve crossing the minimum mean height. The baseline represents time, and the vertical line represents height. The entire Rekhachakra is described in five stages, revealing the conditions of relief development.