Fig. 1 shows a wave-tank enquiry carried out by students investigating a model coastal cliff made from compacted sand and a harder clay cap. A paddle produc...
Question 1 Report
Fig. 1 shows a wave-tank enquiry carried out by students investigating a model coastal cliff made from compacted sand and a harder clay cap. A paddle produced waves of equal size for five minutes. The students noticed that a hollow developed at the foot of the cliff and that the cap later collapsed. The study figure is not to scale, but it represents processes that can affect a rocky coastline. Use the figure and your geographical knowledge in your answer.
(a) Identify the coastal erosion feature shown as the hollow at the foot of the cliff. [1]
(b) Describe two ways in which waves can enlarge this feature. [2]
(c) State two conditions that would make the waves in this investigation more erosive. [2]
(d) Explain why the hard cap may eventually collapse after the hollow has formed. [3]
Answer Details
(a) The hollow is a wave-cut notch. [1]
(b) Hydraulic action forces water and compressed air into cracks, weakening the cliff. Abrasion occurs when sand or pebbles carried by waves scrape and hit the rock, enlarging the notch. [2]
(c) More erosive conditions include greater wave height, more frequent waves, a longer fetch, or a larger sediment load. Any two gain credit. [2]
(d) Erosion in the notch removes support from the cliff base. The hard cap becomes an unstable overhang, so gravity causes it to fall or collapse. [3]
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