Waves and their energy
Most waves are created by wind blowing over the sea surface. Their size depends on wind speed, how long the wind blows, and the fetch (the distance of open water the wind crosses). Like rivers, waves do work by erosion, transportation and deposition along the coast.
Key idea
Strong destructive waves erode the coast, while gentle constructive waves build it up by deposition. The type of coastline depends on which process dominates.
Processes of wave erosion
- Hydraulic action — the force of water compressing air in cracks breaks the rock.
- Abrasion — waves hurl sand and pebbles against the cliff, wearing it away.
- Attrition — rock fragments knock together and become smaller and rounder.
- Solution — sea water slowly dissolves soluble rock such as limestone.
Coastal landforms
Erosion creates cliffs, wave-cut platforms, caves, arches, stacks and headlands. Deposition creates beaches, spits and sand bars. Material is moved along the shore by longshore drift, in which waves push sand up the beach at an angle and gravity pulls it straight back.
Example
Sandy tourist beaches such as those in Port Dickson and Langkawi are depositional features, while rocky headlands and sea stacks show active wave erosion.
Remember
- Waves are mainly formed by wind; energy depends on fetch.
- Erosion: hydraulic action, abrasion, attrition, solution.
- Coasts can be protected with sea walls, breakwaters, groynes and planting mangroves.