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# Aqa A Coasts 1

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### Aqa A Coasts 1

1. 1. Coasts
2. 2. Lesson objectives <ul><li>To understand how waves form </li></ul><ul><li>To describe what happens when waves reach the coast </li></ul><ul><li>To describe the two types of wave: </li></ul><ul><ul><li>Destructive wave </li></ul></ul><ul><ul><li>Constructive wave </li></ul></ul><ul><ul><li>NT pg 144 – 145 </li></ul></ul><ul><ul><li>B&P pg 116 </li></ul></ul><ul><ul><li>CGP pg 64 </li></ul></ul><ul><ul><li>NTb pg 14 - 15 </li></ul></ul>
3. 3. What causes waves? <ul><li>Waves are caused by the WIND dragging on the surface of the water. The friction of the wind on the water creates ripples which will grow into waves if the wind continues to grow. </li></ul><ul><li>Within a wave each water particle moves in a circular motion and returns to its starting point. </li></ul><ul><li>When the wave reaches shallow water it is slowed by friction between the sea and the sea bed. As the water begins to ‘pile up’ the wave loses its regular pattern and breaks. Now the wave moves forward. </li></ul>
4. 4. <ul><li>The stretch of open water over which the wind blows is called the FETCH </li></ul><ul><li>The height and strength of the wave is affected by wind strength and fetch: </li></ul><ul><ul><li>The stronger the wind </li></ul></ul><ul><ul><li>The longer the wind blows for </li></ul></ul><ul><ul><li>The longer the fetch </li></ul></ul><ul><ul><li>=> THE LARGER THE WAVES –> MORE ENERGY </li></ul></ul>
5. 5. What happens when the wave reaches the coastline?
6. 6. As waves reach the coast the base of the wave is in frictional contact with the seabed. The crest of the wave breaks because it is moving faster than its base.
7. 7. <ul><li>The energy of the breaking wave pushes it up the beach as SWASH </li></ul><ul><li>When all of the energy has been used the wave has reached its highest point up the beach. It then runs back down the beach as </li></ul><ul><li>BACKWASH </li></ul>
8. 10. <ul><li>These build up the beach by depositing material </li></ul><ul><li>The swash is stronger than the backwash </li></ul><ul><li>Waves are long in relation to height </li></ul>
9. 11. <ul><li>These remove material from a beach. </li></ul><ul><li>Backwash is stronger than swash. </li></ul><ul><li>Waves are high in relation to length. </li></ul>
10. 12. Constructive and Destructive waves <ul><li>Constructive waves build beaches. </li></ul><ul><li>Each wave is low. As the wave breaks it carries material up the beach in its swash. The beach material will then be deposited as the backwash soaks into the sand or slowly drains away. These waves are most common in summer. </li></ul><ul><li>Destructive waves destroy beaches. The waves are usually very high and very frequent. The back wash has less time to soak into the sand. As waves continue to hit the beach there is more running water to transport the material out to sea. these waves are most common in winter. </li></ul>