Waterfalls Sample Answer

Question:

Examine the orle of the processes of erosion on the formation of one fluvial landform that you have studied.

I have studied the role of the processes of erosion on the formation of a waterfall.

A waterfall is a vertical interruption in the river profile that occurs due to vertical erosion in the youthful stage of the river.

An Irish example is Torc Waterfall in Killarney, Co. Kerry

In the youthful stage of the river, the river has a very high velocity. This means that it flows very fast so it is very powerful, therefore, vertical or downward erosion occurs into the river bed.

Soft and hard rock lies across the riverbed. Soft rock such as sandstone erodes faster than hard rock such as granite. This is called differential erosion.

The power and force of the river carve out hollows in the river bed through hydraulic action. process named then occurs as broken rocks become trapped in these hollows.  

This causes the hollows in the river bed to widen and become deeper. The hollows eventually spread out to form a vertical drop or notch in the river bed which the river plunges over.

Hydraulic action continues to occur as the impact and force of the water flowing over the drop breaks and wears away the rock at the base, eventually creating a plunge pool. 

Abrasion combined with hydraulic action widens and deepens the plunge pool. The falling water forces stones and pebbles to swirl around the plunge pool. This deepens it which is a process called eddying.

Splashes from the falling water erode into the back wall of the waterfall. This is called undercutting.

This undercutting creates an overhang because the soft rock is eroded and the hard rock is left elevated above the plunge pool. Eventually, the overhang collapses into the plunge pool.

Abrasion occurs as the hard rock falls into the plunge pool, further eroding it. As the pieces of rock in the plunge pool swirl around in the water, they collide with each other and break into smaller pieces. This is where attrition occurs.

The water in the plunge pool can spray onto the undercutting which erodes it further through solution. This is the process whereby water reacts with minerals in the rock, causing them to crumble.

The undercutting and collapsing repeat over time, causing the river to retreat upstream in a process called headward erosion. Eventually, a steep-sided valley known as a gorge is created downstream.

A famous example of a waterfall is Niagara Falls in Canada.