Waves Aim To know the difference between constructive

Waves! Aim : To know the difference between constructive and destructive waves.

Reminder Info on waves (no need to re-copy this!) • The size of a wave depends on its fetch. • The fetch is the distance a wave travels. • The greater the fetch, the larger the wave. • Wind also has a significant effect on the size of waves. - The stronger the wind the larger the wave.

Let’s watch a clip to show us what happens to waves as they approach the coast. Understanding Waves!

So what do waves do to the coast? • As a wave approaches a beach it slows. • This is the result of friction between the water and the beach. • This causes a wave to break.

• So what happens to the shape of the wave? The size of the wave on the water’s surface gets bigger In deep water the wave is round and small The wave breaks on the shore The water gets shallower, friction on the sea bed slows it down and the wave becomes more elliptical ( squashed)

Let’s see that in animation: (pay particular attention how the shape of the wave changes as it approaches the shore) Wave Motion!!

Any more new terms I need to know? YES these! Wave length: the distance between the top of one wave and the next Swash: water moving UP the beach Backwash: water moving back down the beach to the sea

So what is a constructive wave? • Constructive waves build beaches. 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.

What about a destructive wave? • Destructive waves destroy beaches. The waves are usually very high and very frequent. The backwash 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

Another animation (watch carefully to see how the waves change shape) Constructive and Destructive waves

A quick revision of today’s key words. Do you know what they all mean? friction elliptical Destructive waves Constructive waves Waves! backwash Wave length swash

Well done! • You now know; • The difference between constructive and destructive waves. • What causes a wave to break on the beach. • How beaches are formed. • How beaches are destroyed. • (and if you don’t then re-read the slides and check your notes!)