SkillBuilder discussion Geographical inquiry 1. Use the compass shown in FIGURE7 to answer the following questions. a. Identify the direction of the swash. b. Identify the direction of the backwash. c. Identify the direction of longshore drift. 2. If this pattern continues, predict what feature might
FIGURE7 The process of longshore drift
0
250
500 m
Longshore drift
Wave direction
develop at the southern end of the beach. Give a reason for your answer.
Wave direction
3. Is this an example of
constructive or destructive wave action? Explain.
Sea
KEY
Beach
Movement of wave onto beach (swash)
Backwash
Direction beach material is moved
CASESTUDY CapePeron
Cape Peron in Western Australia’s Shoal Islands Marine Park is a prime example of a tombolo — a landform created when a sand spit joins one island to another or the mainland. At the end of the last ice age, some 10 000 years ago, Cape Peron was part of a limestone ridge which created high points along the coast. Rising sea levels created a chain of islands and wave action moved sand between the islands, forming a cuspate spit . Over the last 2000 years, this process has created a tombolo, connecting Cape Peron to the mainland. Today, the same process is joining Penguin Island to the coast by a sandbar. A tombolo typically forms in areas with constructive waves that are sheltered from prevailing winds, resulting in sandy beaches such as those along the eastern shore of Cape Peron. Erosion is evident in other parts of the marine park. Cape Peron’s western shore includes erosional landforms such as cliffs, arches and collapsed bridges. These locations are exposed to prevailing winds and destructive waves. Reefs and offshore stacks are also present in the west ( FIGURE8 ).
TOPIC13 Landforms and landscapes – diversity, significance and management 297
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