LESSON 23: WAVE ACTION IN COASTAL AREAS
Definition: a wave is an oscillation of water particles in the sea or ocean caused by friction between wind and water.
Major processes of wave erosion
- By corrosion or abrasion: waves armed with rock debris such as sand, shingles and boulders hurt against the cliff which results to breaking.
- BY HYDRAULIC ACTION: water thrown against a cliff face by breaking waves into cracks.
- By attrition: boulders and pebbles carried by waves collide against each other.
Features produced by wave erosion:
- Capes and bays: a cape is the portion of the land that projects into the sea. It is usually made of resistant rocks. Where rocks are different in there, indentations occur. The more resistant rocks will project in the sea while the less resistant rocks will be eroded to produce small indentations called CAVES.
Bays: a bay is a curved break in the coastline; it is the portion of the land that projects into the sea.
- Cave, blow hole and geo:
A Cave is a large hole or tunnel on the rock face of a cliff. It develops from a small crack due to hydraulic action.
A blow hole is a vertical tunnel which links the sea cave with the surrounding inland.
A geo is a long narrow steep sided inlet running along the edge of a cliff.
Other erosional features are cliff, arch, stack and stump.
Wave deposition features:
Some wave deposition features are; beach, spit, bar, tombolo, mudflat.
- Beach: a beach is gently sloping plat form of mud, sand and pebbles which lies between the low and high levels of water. Different types of beaches can be identified; storm, sand, bay head, and shingle beach are some types of beaches.
- Spit: it is a long narrow accumulation of sand and shingle with end attach to the land and the other end projecting to the sea. A cliff is formed by long shore drift. When the wave reaches a curve on the coast, the material carried is deposited to form a ridge of sand.
- A bar: it is a ridge of sand or bank of mud, sand, and shingle deposited in the water parallel to the coast.
A bar starts like a spit, but with time becomes attach to the mainland at both side.