Waves Flashcards
What is a coast?
A dynamic area where the sea meets the land
What is the length of the uk coastline?
7723 miles
how far does the coast line extend inland and offshore?
Inland: settlements (such as seaside resorts), natural environments (such as sand dunes and salt marshes)
Offshore: several hundred meters- the various processes affecting the waves and the movement of sediment
what percentage of sediment found at the coast comes from rivers?
90%
what are the four main types of zone at the coast
onshore zone, backshore zone, intertidal and nearshore zone, offshore and subtidal zone
what are the three zones found inside the intertidal and nearshore zone?
swash zone, surf zone, beaker zone
what is the tidal range?
the maximum and minimum heights of the waves that the waves can be among at one time
what is the intertidal zone?
the area of seabed which is exposed to the air at low tide but submerged at high tide
which zone is only affected by waves in stormy conditions?
backshore zone
what is the wave length?
the distance between the crests of the waves
what is the wave height?
the distance between the crest and trough
what is the depth of the wave?
the distance between the seabed and the still water level
what is the fetch?
the distance the wind has traveled uninterrupted over the sea
what do swell waves look like?
lower height and longer wave length
what waves affect coasts which face open oceans?
swell waves
what waves affect coasts which do not face open oceans?
sea waves
why bare sea waves more choppy than swell waves?
they haven’t had time to separate so waves of several lengths arrive at the shore together eg. north sea
describe how a wave changes as it approaches the shore?
- wave becomes more elliptical in shape due to the shelving (steeper) sea bed causing the base of the wave to slow down due to friction
- The crest isn’t affected so continues at the same speed which is faster than the new speed of the base. This means that the crest rises
- the wave continues the steepen until it reaches a ratio of 1:7 (wave height to wave length) after which it breaks and water rushes up the beach as swash
what are waves which reach the shore known as?
waves of translation
describe a spilling breaker
occur on gentle beach gradients with steep waves. the gradual peaking of the wave leads to the crest becoming unstable. gentle spilling of wave crest
describe a plunging breaker
occur on steeper beach gradients with medium height waves. waves peak to vertical height appearance, curls over and plunges forwards and downwards
describe a surging wave
occur on very steep beach gradients with gentle waves. waves don’t break and slide up the beach in a smooth motion
give some examples of characteristics of destructive waves
- usually created due to long fetch and powerful sustained windy periods
- short wave length and steep waves
- backwash is stronger than swash so material is eroded of the beach
- creates a steep beach profile
- has a plunging spill onto the beach
- ridge of shingle deposited at the rear of the beach
what is the wave frequency of a destructive wave?
10.14 per minute
give some examples of characteristics of constructive waves
- low waves with long wave length (can be upto to 100m)
- gentle spill onto the beach ]
- gentle beach profile
- berms are created via swash
- strong swash and weak backwash
what is the wave frequency of constructive waves?
6-8 per min
describe the process of wave refraction
where waves approach a irregular coastline they are refracted. Waves slow down in the shallow water in front of a headland because of friction with the sea bed so waves in deeper water move ahead
what are orthogonals?
lines which are drawn at right angles to the wave crests and show how wave energy is concentrated upon a headland, enhancing erosion
how does wave refraction help to maintain bay beaches?
sets up longshore currents that move sediment from the headlands into the bays forming bay beaches
what is the wave period?
the time taken for one wave to travel through one wave length
what is wave velocity and how do you calculate it?
speed of movement of the wave crest. It can be calculated by dividing the average wave length by the average wave period
what is wave frequency?
the number of waves that break on the beach in a given time
how do you calculate wave steepness?
wave height/wave length however it cant exceed 1:7 because this is when it breaks
