COASTSCOASTS

Lesson 1Lesson 1

• Aim: To understand the Aim: To understand the processes that lead to coastal processes that lead to coastal erosion.erosion.

A coast is found where A coast is found where the land meets the the land meets the sea. Coasts undergo sea. Coasts undergo change due to coastal change due to coastal processes and (as with processes and (as with rivers) there are three rivers) there are three main processes at main processes at work:work:

•erosion erosion

•transportation, and transportation, and

•deposition deposition

Each of these Each of these processes involves the processes involves the power of the sea and power of the sea and the effect of waves the effect of waves that are carried to that are carried to shore. However, other shore. However, other factors also change factors also change and shape our coasts:and shape our coasts:

Introduction to Introduction to CoastsCoasts

How can it How can it change?change?

WAVESWAVES

Waves• The power of waves is one of The power of waves is one of

the most significant forces of the most significant forces of coastal change. Waves are coastal change. Waves are created by wind blowing over created by wind blowing over the surface of the sea. As the the surface of the sea. As the wind blows over the surface of wind blows over the surface of the sea, friction is created - the sea, friction is created - producing a swell in the water. producing a swell in the water. The energy of the wind causes The energy of the wind causes water particles to rotate inside water particles to rotate inside the swell. This moves the the swell. This moves the wave forward.wave forward.

The size and energy of a wave The size and energy of a wave is influenced by:is influenced by:

• The length of time that the The length of time that the wind has been blowing wind has been blowing

• The strength of the wind The strength of the wind • How far the wave has travelled How far the wave has travelled

(called the fetch) (called the fetch)

Click on the surfer to start short video on waves 1.14

Waves• The power of waves is one of the most significant forces of The power of waves is one of the most significant forces of

coastal change. Waves are created by wind blowing over coastal change. Waves are created by wind blowing over the surface of the sea. As the wind blows over the surface the surface of the sea. As the wind blows over the surface of the sea, friction is created - producing a swell in the of the sea, friction is created - producing a swell in the water. The energy of the wind causes water particles to water. The energy of the wind causes water particles to rotate inside the swell. This moves the wave forward.rotate inside the swell. This moves the wave forward.

The size and energy of a wave is influenced by:The size and energy of a wave is influenced by:• The length of time that the wind has been blowing The length of time that the wind has been blowing • The strength of the wind The strength of the wind • How far the wave has travelled (called the fetch) How far the wave has travelled (called the fetch)

Constructive Constructive WavesWaves

•operate in calm weather •are less powerful waves •break on the shore and tend to deposit material, building up beaches •are responsible for transporting material . •swash is stronger than the backwash.

Destructive WavesDestructive Waves

•operate in storm conditions operate in storm conditions •are created from big, strong waves when are created from big, strong waves when the wind is strong and has been blowing for a the wind is strong and has been blowing for a long time long time •occur when fetch is greatest.occur when fetch is greatest.•tend to remove material from the coast and tend to remove material from the coast and associated with associated with erosion

•backwash is stronger than the swash.backwash is stronger than the swash.

Processes of coastal Processes of coastal erosionerosion

•The constant force of waves crashing on the shore damages it. This is called hydraulic action.

•Waves bring with them bits of rock and sand. These help to grind down cliffs. This is called abrasion or corrasion

•Waves cause rocks and pebbles on the shore to smash into each other and break down. This is called attrition.

•Acids contained in sea water will slowly dissolve certain types of rock. This is called corrosion or solution.