Interlocking spurs are areas of high ground that jut out on either side of the river and appear to lock together.
Examples can be seen in the upper course of the River Slaney.
Waterfalls
A waterfall occurs where a river flows over a vertical slope. Waterfalls are a feature of erosion.
An example of a waterfall can be seen at Powerscourt, Co. Wicklow.
Formation 1
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River flows over an area where hard rock lies on top of an area of soft rock.
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.
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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.
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Powerscourt Waterfall, Co. Wicklow
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.
2 hard rock hard rock soft rock Working with others:
Mark the interlocking spurs on this image (use a pencil). Now compare your work with a classmate to see if your markings match up.
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1. Describe the formation of a V-shaped valley, using a labelled diagram to support your answer.
2. What are interlocking spurs? 3. Explain with the aid of labelled diagrams how waterfalls form. Where in Ireland might you find a waterfall?
