Waterfalls

·         The landform that I have studied is waterfalls.

·         An example of a waterfall is Torc Waterfall, Co. Kerry.

·         The processes that take place are Hydraulic Action, Eddying, Abrasion and Solution.

·         A waterfall is a feature of fluvial erosion that forms in the upper course of a river.

·         It is most likely to occur where the river course slopes downwards and the river flows over a band of hard, resistant rock eg. Granite with a layer of softer, less resistant rock underneath, eg. Chalk.

·         The river bed will be subjected to vertical erosion, leading to deepening of the bed rock.

·         As a result of differential erosion, the water quickly erodes the softer rock through the processes of hydraulic action (the erosion caused by the power of the flowing water which will loosen and remove material from the river bed), abrasion, (the impact of the rivers load hitting against the soft bedrock) and solution, (the dissolving effect of acids in the water on the materials of the soft rock).

·         The river continues to cut downwards (vertical erosion) into the softer rock, steepening the gradient of the river, resulting in the formation of a small fall in the river bed.

·         The erosive power of the falling water creates a plunge pool at the base of the waterfall. Eddying is now present, where the swirling motion of the water and turbulence uses the load to widen the plunge pool.

·         The falling water also begins to undercut the less resistant rock of the water, mainly by hydraulic action and solution (dissolving of rock) to create an overhang.

·         Over time, the band of hard rock becomes unstable as a result of continual erosion and eventually breaks off and collapses into the plunge pool, increasing the height of the waterfall. The collapsed rock is broken down by attrition and is transported downstream by solution, suspension, saltation and traction.

·         The repeated process of undercutting and collapsing results in headward erosion of the waterfall.

·         It gradually retreats upstream to leave a steep-sided gorge. Eg. Niagara Falls, USA.

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·         However, a waterfall is a temporary feature, as headward erosion will eventually undermine all the resistant rock.

·         The river will then once again begin to develop a regular profile.

·         Though waterfalls are usually found in the youthful stage of a river, they can sometimes be formed on the lower stage as a result of river rejuvenation due to a drop in river base level.

·         Faulting can also lead to the formation of waterfalls. At a normal fault, the land slips downwards, and if a river was flowing down this, it will now have changed.

·         Waterfalls can also be found in Glaciated regions where hanging valleys occur.