Waves and Tides
- The stronger the wind the longer it blows, the longer the fetch the larger the waves will be and more energy they'll have.
- Swash - the water that rushes up the beach when a wave breaks.
- Backwash - the water that rolls back down a beach after a wave has broken.
- Backwash more energy than the awash = the waves eat at the land.
- Swash more energy then the backwash = materials left on the land.
- The moon attracts the sea and pulls it upwards and the rise and the fall of the sea gives us the tides.
- High tide - is when the tide is in at the coastal town
- Low tide - is when the tide is out, leaving the boats resting on mud.
- High tides occur about every twelve and a half hours, with low tides in between.
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The waves at work
- Waves erode the coast
- Waves deposit in sheltered areas
- Waves transport eroded material
- Waves hammer against the rock over time this breaks the rock up.
- Hydraulic action - waves force water into cracks in the rock under pressure, this breaks the rock up.
- Solution - Water dissolves soluble materials from the rock.
- Abrasion - Waves fling sand pebbles and large stones against the rock. They wear it away like sandpaper.
- Atrtrition - Chunks of rock get knocked together and worn into smaller bits.
- Deposition - if waves carry more material on the land a beach forms.
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Landforms created by the wave
- Headland - hard rock erodes more slowly than soft rock, forming an headland.
- Bay - softer rock has been eroded away.
- Eroded material is carried along the coast by longshore drift. If longshore drift is interrrupted you get a spit.
- Salt marsh - Silt and mud build up in a sheltered area.
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- Cliffs are eroded by waves and weakened by weathering.
- It winter the ice makes the cracks bigger.
- Heavy rain means the cliffs are full of water.
- The more water in cliffs the weaker they are.
- Clay cliffs are the worst, huge blocks of clay slide down the slope.
- One way to solve the problem is to bury pipes in them so they carry the water away.
- This is expensive and pipes don't last forever.
- You can use rock armour to stop the cliffs from collapsing.
How can we stop the coast eroding?
- Sea walls
- rock armour (Soak up the waves energy)
- Build barriers out at sea to make the waves break away from the shore
- Build groynes to stop sand being carried away because the sand protects the coast
- Beach replenishment by adding more sand
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