A strong wind and long fetch create powerful destructive waves , which can strip beaches and erode the landscape. A gentle wind with a small fetch will create less powerful constructive waves , whichmay deposit sand on the coast and create depositional landforms. If the swash is more powerful than the backwash , the waves are constructive, and depositional landforms will be present. On the other hand, if the backwash is more powerful than the swash, the waves will be destructive, and erosion will be evident ( FIGURE2 ).
SkillBuilder discussion Geographical inquiry 1. Look at FIGURE2 . Explain the difference between constructive and destructive waves. 2. Why are sandbars associated with beaches that have destructive waves? 3. Will a sandy beach be
FIGURE2 Comparing constructive and destructive waves
A destructive wave exerts significant force down onto the beach as its small but powerful swash hits the sand.
created by constructive or destructive waves? Justify your answer.
Steep gradient
Sandbars cause the waves to break and are often present on beaches with destructive waves.
Its strong backwash takes sand away from the beach and back into the ocean.
The strong swash of a constructive wave carries a significant amount of sand onto the beach as it breaks.
As a result of the gentle gradient of the beach, the swash often percolates into the sand, depositing material as it loses energy.
Gentle gradient
The wave’s weak backwash cannot carry the sand back into the ocean, leaving it on the beach and helping to extend the beach area.
294 Jacaranda Humanities Alive 8 Victorian Curriculum Third Edition
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