SS2 First Term Geography Lesson Note – Action of Waves

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WEEK 6                                                       

TOPIC: ACTION OF WAVES
CONTENT:  

1. Definition of Waves, Tides and Ocean Currents and their Characteristics.
2. Erosional Processes of Waves
3. Erosional Features of Wave Action
4. Features of Coastal Deposition

SUB-TOPIC 1: DEFINITION OF WAVES, TIDES AND OCEAN CURRENTS

Waves are formed by winds blowing over the ocean surface which cause the surface water to move towards the coast in ripples or waves. In other word wave can be defined as an oscillatory movement of a large body of water approaching the coast. It is the most powerful and important agent of marine erosion.

Tide is the alternate rise and fall of the surface of the sea, approximately two times a day.

Ocean current is the regular movement of the surface water of the ocean from one part of the ocean to another.

SUB – TOPIC 2: EROSIONAL PROCESSES OF WAVES (MECHANISM OF WAVE EROSION)

1. Corrosion: It is the wearing down of the base of the cliff by mass of fragments carried by wave action.
2. Attrition: It is the breaking down of materials like pebbles, boulders, etc. when they hit cliff faces and each other, as the wave continues its activities, into smaller particles. This results in relatively fine pieces of fragments which are well polished.
3. Solution/Solvent action: It involves the disintegration of rock materials such as limestone and chalk in the coast by chemical action of the sea.
4. Hydraulic action: In this process, fast moving waves force themselves into cracks and cavities within the base of the cliff under pressure and enlarge the cracks.

SUB – TOPIC 3: EROSIONAL FEATURES OF WAVE ACTION

The features produce by wave action include:

• Cape: – A cape is a prominent projection, headland or cliff protruding into the sea. Capes are made up of hard rock and are usually resistant to wave actions. Examples of cape in West Africa are Cape Three Points in Ghana, Cape Verde in Senegal etc.
• Bay: – A bay is a wide curved inlet of sea or a wide opening carrying indentation of the sea or lake into the land. Bays are less steep than capes, they are inlets made up of relatively soft rocks, bays usually contain water and they are used as harbour.

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