Essay - Upper Course Landforms (Waterfall)

Q. Discuss with the aid of a labelled diagram, the formation of one landform of erosion you have studied

Q. Examine the role of the process of erosion on the formation of one fluvial or one coastal/marine or one glacial landform you have chosen

The landform of erosion I have studied is the waterfall.
A waterfall is an interruption in the river profile with the water taking a significant vertical drop.
They are the most obvious feature of erosion in the upper course of a river
Begin to form as a result of differential erosion (the relatively greater rates of erosion in some areas as opposed to others due to differences in rock resistance)
When a river encounters a band of softer rock, it begins to erode it, primarily by hydraulic action
The harder, more resistant rock is left behind
This forms a slight drop in the river’s profile causing an increase in velocity.
The hard rock is eventually undercut by hydraulic action, abrasion/corrasion and solution
The rock at the base of the waterfall is quickly eroded
Over time, the height of the drop increases once again, as well as the velocity
A plunge pool is gouged out at the bottom of the waterfall
The plunge pool gets bigger over time and further undercuts the hard rock, forming an overhang
This overhang becomes unstable due to its lack of support and eventually collapses
The entire process is hence repeated again, with the waterfall retreating upstream (this process is known as headward erosion)
When the cycle is repeated again and again, a steep-sided gorge is created
Waterfalls are temporary features
Irish example: Powerscourt