booklet two

• what causes wind? - movement of air from one place to another, from high to low pressure

  - in UK, prevailing wind is from the SW, these blow over the Atlantic and have potential to transfer great deal of energy to the waves that approach UK
• how can waves be created? - mainly from wind

  - can be generated by tectonic activity or underwater landslides, creating a tsunami
• waves: - created by transfer of energy from wind blowing over surface of the sea

  - as strength of wind increases, so does the frictional drag and size of wave
• factors affecting wave energy: - strength of wind

  - duration of wind ~ longer wind blows, more powerful wave becomes

  - fetch ~ distance of open water over which the wind blows
• longest fetch in UK: - extends over 3000km across Atlantic Ocean to Brazil
• characteristics of a wave
• crest


  top of the wave
• wavelength


  distance between two crests
• wave height


  difference between the crest and trough
• trough


  bottom of the wave
• wave period


  time between each wave
• why do waves break? - waves move energy (not water) far distances

  - kinetic energy moves THROUGH the water

  - the water is moving but only in a circular motion
• what happens when waves reach the coast? - sea becomes shallower when waves hit the coast, meaning there's more friction in water, slowing them down

  - creates smaller waves

  - when there's less friction on sea bed, waves are larger as orbital motion isn't disrupted as much
• constructive waves: - break gently with low frequencies (6 - 8 a min)

  - material deposited along coast

  - material moved up beach forming ridges (berms)

  - form spits, sand bars and tombolos
• destructive waves: - steeper beach

  - high proportion to length of wave

  - erodes coastline

  - rapidly steepen when approaching beach, then plunge down

  - wave cut platforms, bays, headlands, arches, stacks, stumps
• wave refraction: overtime headlands are more eroded than bays. this is because:

  - in bays, wave crests curve (diverge) to fill bay and wave height decreases

  - at headlands, it becomes shallow and wave height increases

  - the waves refract, concentrating their power on the headlands
• how does wave refraction demonstrate negative feedback? - the softer rock is eroded faster to form bays, leaving a headland

  - wave refraction is concentrated on the headland, eroding it faster