Junior Cycle Geography CYCLONE Working with others
With a partner, point to where you think the interlocking spurs are on this photo.
Feature: Waterfalls
A waterfall occurs where a river flows over a vertical slope. Waterfalls are a feature of erosion.
Example: A waterfall can be seen at Powerscourt, Co. Wicklow.
hard rock hard rock
hard rock
soft rock soft rock
soft rock
How a Waterfall Forms
1 1
1
1 The river flows over an area where hard rock lies on top of an area of soft rock.
2 The river erodes the soft rock faster. This develops a vertical drop where the hard rock and soft rock meet. This drop is called a waterfall.
2 2
hard rock hard rock
2 hard rock 3
3 3
3 At the base, a plunge pool develops due to the force of the falling water (hydraulic action) along with its load swirling around at the base which wears away the base by abrasion.
4 4
4
4 The rock above the plunge pool is undercut and left hanging. It eventually collapses into the plunge pool below. As this process continues, the waterfall slowly erodes its way upstream.