Landform Development #1

B

(i) Explain with the aid of a labelled diagram(s) the formation of one landform of erosion that you have studied.

Landform caused by erosion.

A waterfall is an example of a landform formed by means of erosion which I have studied. Waterfalls are found in the upper course of a river during the youthful stage of the river’s life cycle. During this stage of the river’s life the river is flowing at high velocity and so is quite powerful and erosive.

Waterfalls occur where an area of hard rock meets an area of softer rock. As the river flows down the steep gradient accustomed to that of a river in the youthful stage the riverbed is eroded by means of vertical erosion. The area of soft rock is eroded at a faster rate than that of the hard rock by means of hydraulic action, as the sheer physical strength of the flowing water erodes into the bed and removes any areas of weakness. Abrasion is the process whereby the river’s load is used to scrape and scratch against the bed and removes any excess material, further deepening the river depth and highlighting the difference in height between the area of soft and hard rock. This results in a sudden vertical drop in the river bed, creating a mini waterfall.

As the falling water strikes the area of soft rock, further vertical erosion occurs through hydraulic action. Constant falling water wears away the river bed quite efficiently and results in the formation of a plunge pool. As the river flows down into the plunge pool from a height it is forced to swirl by the natural shape of the plunge pool. This swirling water is full of energy due to the immediate vertical drop and uses its load to further erode the plunge pool and deepen the undercut resulting in an overhang above. Over time, as the plunge pool deepens and the undercut enlarges the overhang becomes increasingly unstable. The force of gravity coupled with its own weight forces the overhang to fall. This causes the plunge pool to deepen and the waterfall to retreat upstream....

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