3.1.3.2 Coastal Landscapes in the UK Flashcards
How are waves formed?
- waves are formed by the wind blowing over the sea
- friction with the surface of the water and the transfer of energy from the wind blowing over the surface to the sea causes ripples to form and these develop into waves
- waves can also be formed when earthquakes or volcanic eruptions shake the seabed - these waves called a tsunami
Example of a tsunami:
- in March 2011 a wall of water up to 40m high crashed into the Japanese coast north of Tokyo destroying several coastal settlements and killing over 20,000 people
Fetch:
- the distance the wind blows across the water
- the longer the fetch the more powerful the wave
Swash:
part of wave that crashes onto the shore when a wave breaks
Backwash:
part of wave sweeping back into the sea under the force of gravity after a wave break
Wave frequency:
number of waves that pass a certain point per second
Wave crest:
top of the wave
Wave trough:
bottom of the wave
Wave length:
distance between 2 successive crests on 2 waves
What affects the size of a wave?
- wind duration - how consistently and the length of time the wind blows for
- distance of sea over which the wind has blown
- strength of the wind - greater the wind the greater the frictional drag and therefore the greater the size of the wave
- wind speed
- fetch - distance the wave travels across the water
Sea waves:
waves that travel short distances and are the result of local waves
Swell:
waves that formed from distant storms and travel large distance
Which part of England has waves with an incredibly long fetch and why?
- the South West of Britain is affected by waves that have an incredibly long fetch, as the South Westerly wind (prevailing winds) which blow the sea there travel uninterrupted for thousands of miles across the Atlantic Ocean
- due to this waves are large in Cornwall and generally great for surfing
What is the fetch from Brazil to SW England?
9,000km
What would be the ideal conditions for erosion in England
- onshore SW winds with frequent gusts 160+ km/hr
- long fetch over Atlantic Ocean = storm conditions e.g. Cornwall 4-5 January 1998
Constructive waves:
able to build the beach as swash is stronger than backwash
Characteristics of constructive waves:
- low waves (but have long wavelength - up to 100m) that surge up the beach and ‘spill’ with a strong swash
- carry and deposit large amounts of sand and pebbles and ‘construct’ the beach making it more extensive due to strong swash - beach material moved upwards
- surfers prefer constructive waves because they give longer rides
- strong swash however it rapidly loses E as water percolates through beach material leaving a weaker backwash so no material is removed
- these waves are formed by storms often 100km’s away
- wave crests fare apart
- gently sloping wave front
- low frequency approx. 6-8 waves/min
- breaking wave spills forward
- associated with gentler beach profiles
Destructive waves:
destroy the beach as backwash stronger than swash so material taken back out to sea with the wave
Characteristics of destructive waves:
- formed by local storms close to coast and can ;destroy’ the beach
- waves closely spaced and often interfere with each other producing chaotic swirling mass of water
- high wave height and steep wave front (bit shorter wavelength) - become high and steep before plunging down onto beach
- little forward motion (swash) when destructive wave breaks but powerful backwash - explains removal of sand and pebbles and gradual destruction of beach
- on steep beach
- high frequency approx. 10-14 waves/min
What causes water tor rise up and break on the beach?
- water becoming shallower (friction with the sea bed) causes waves to rise upwards and break
Why when waves break on a sandy/pebbly beach the amount of backwash is often less than the amount of swash?
water soaks into a sandy/pebbly beach, so there is less backwash than swash
Why are larger pebbles found at the top of the beach with smaller pebbles found at the bottom?
- swash carries a mixture of pebble sizes up the beach and only has the energy to pull back the smaller pebbles
- over time, the sorting process results in larger pebbles being left at the top of a beach with smaller pebbles deposited at the bottom of the beach
Where did the Jurassic coast landslip take place and what happened?
- process of mass movement occurred near Seatown in West Dorset on the Jurassic coast in 2021
- such events occur frequently along this stretch of the coast where the cliffs are loose and unstable
- processes like this combine with the action of waves to shape the coastline
What happened as a result of the Jurassic Coast landslip?
the South West Coast Path was diverted away from the cliff edge to keep walkers safe