Waterfalls

What you need to do:

• Name the landform.

• Name an Irish example of that landform.

• Draw a well-labelled diagram.

• Explain the formation of the landform focusing on the processes of erosion.

• You must name and explain at least 2 processes of erosion.

Waterfalls

This answer will examine the processes involved in the formation of waterfalls, landforms formed by river erosion. Irish example: Torc Waterfall, County Kerry.

The river erosion processes involved in the formation of a waterfall are hydraulic action, abrasion and solution.

Hydraulic action is the force of moving water on the land. Fast-flowing water forces out loose rock and soil from the riverbed and banks. Over time the banks collapse. Soft rocks are eroded faster than harder ones. (Differential erosion)

Abrasion is the wearing away of the riverbed by its load. Stones carried by the river scrape away and smooth the river channel as they move along, deepening and widening the river channel.

Solution occurs when river water dissolves the soft rock over which it flows.

The erosion process as mentioned above combine to form waterfalls in the youthful stage of a river's course. Waterfalls occur where a band of hard rock, example granite, lies across the river's bed. Soft rock (e.g. shale) is eroded more quickly. Gradually a small fall forms in the river bed. The hydraulic force of water and abrasion combine to deep in the fall. A plunge pool forms at the base of the waterfall due to erosion caused by the weight of the water and the stones carried by the river over the hard rock. Water also splashes against the back wall of the waterfall and the road is it by the process of solution. Eventually the overhanging piece of rock collapses and slowly the waterfall moves or retreats upstream. Sometimes a steep sided gorge is formed if headward erosion forms very quickly undersides of the valley have not had time to be widened by mass movement.