waves and the coast
waves and coast
definitions
coast
waves
the transition zonebetween the land and the sea
factors affecting the coast can be
human activity
sea
weather and climate
land
a long body of water curling into an arched form and breaking on the shore. They erode, transport and deposit materials
waves are created by winds, the wind makes friction with the sea creating a wave, this is why the power of the wave is the power of the wind, it as well depends on the length and time it has been affected by the wind, this factors are called fetch
terminology of waves
wave length
wave height
wave frequency
velocity
fetch
swash
backwash
the distance between 2 successive waves
distance between the through and the crest
crest
through
lowest point of the wave
highest point of the wave
the movement of water down the beach
the amount of water over which a wave has passed
number of waves per minute
the speed of the traveling wave
the movement of water up the beach
constructive and destructive waves
destructive waves
steep gradients
wind strendth, rainfall
settlement, development
water depth, ecosystem
ecosystem, river sediment
there are 4 main processes happening along the coast
erosion
the wearing away of rocks by wind and rain
types of costal erosion
hydrolic action ( wave hit wall)
attrition (rock hit rock)
abrasion(Rock scratch rock)
solution (dissolve rock)
the sheer power of the waves repeatedly forcing water and air bubbles into cracks in the rock
longshore drift
when a rock becomes eroded off a cliff or a rock the waves can move it along the beach, this is called longshore drift. (the smaller the material the faster it will move)
diagram in comments
when the sand particles and stones hit against each other and are broken into smaller particles
weathering
mass movement
when the salt and chemicals in the seawater dissolve away the rocks that the shoreline is made up of
when the stones in breaking waves wear against rocks
types of weathering
physical
biological
chemical
onion skin weathering
when a rock repeatedly gets heated and cooled causing it to break down
freeze thaw weathering
happens when rainfall gets acumulated inside rock cracks, this water then freezes and makes the crack expand. This repeated process will cause the rock to break down.
weathering that is caused by plants or animals, for example a seed falling into a crack expanding the crack as the plant grows
physical and biological weathering are types of mechanical weathering
a chemical reaction that changes the nature of the rock causing it to break down
the removal of cliff based materials by gravity
landslide
mudslide
rock fall
slumping
the downslope movement of discrete blocks of rock down a flat/linear slip plane, maintaining contact with the cliff surface throughout
a rock fall involves fragments of rock breaking away from the cliff face, often due to freeze-thaw weathering
occur when saturated soil and weak rock flow down a slope.
Slumping is a rapid movement of a mass of earth or rock sliding along a concave surface.
constructive waves
elliptical orbit
the movement of material along a coast by waves which approach at an angle to the shore but recede directly away from it.
Process of transportation
Suspension
Solution
Saltation
Traction
prevailing wind
a wind from the direction that is predominant or most usual at a particular place or season.
large heavy material dragged along the coast
small material bounces along the sea
small material bounces along the coast
Dissolved material carried in water
Wave action
waves will
transport
deposit
erode
Hight and strenght of the wave is determined by
strength of wind
amount of time with wind
fetch
low wave height
shallow gradients
long wavelength
deposits sediment
strong swash
weak backswash
carries a lot f sediment
removes very little material
remove sediment from the beach. They have a short wave length, normally occur on steep gradients and have a circular orbit. High wave height. Weak swash, brings little material, strong backswash which removes a lot of sediment.
circular orbit
high wave height
short wave length
Removes sediment from the beach
weak swash
strong backswash
Carries little material
Removes a lot of sediment
Process of a wave
Why do waves deposit material
wave looses energy
little/ no wind
shallow waters
wave aporaches the coast and enters shallow water
friction with the sea bed makes the wave lean forward
The wave crests and break onto the beach
Rates of erosion
eriosion is affected by 3 things
material
Shore geometry
energy
More energy in the wave means more material will get eroded
More energy is available when
destructive waves
waves break onshore
steep gradients
strong tidal currents
rip currents
Narrow fast moving currents
more wind
The type and mount of material affects the rate of erosion
More erosion happens when
large amounts of material increase abrasion
less resistance rocks (soft rock) erode more easily
Less erosion happens
Large beaches absorb wave energy, reducing erosion
More resistant rocks erode more slowly
If more material goes into the wave the system deposits more material, leading to larger beaches
Steeper gradients lead to destructive waves
destructive waves cause more erosion
shallow gradients lead to constructiv waves
Constructive deposit more material
Eroded material comes from
Longshore drift
Constructive waves
Eroded cliffs
RIvers discharge
Longshore drift
Main process of deposition and transportation in the coast
Process
the prevailing wind pushes the waves at an angle
The waves break and the swash carries the material up the beach
The backwash carries the sediment back to the sea at a 90º angle
The process repeats, resulting in the sediment moving with a zigzag motion
Deposition happens when
increased friction between water and seabed
large amounts of sediment is being carried by the water
wave energy decreases
the water encounters an obstacle which means the wave breaks, depositing the sediment it is carring
Does not shape the coastline, it only changes the shape of the rocks
more fetch
Sediment being transported in the coast
Deposition
COstal deposition is when sediment is deposited in the coast
This happens when the flow of water flow slows down
This happens because there is a decrease in energy so sediment can't be carried by the waves
Wave refraction
When a line of waves changes shape due to the change of the shaoe of the coast
Happens comonly in headlands and bays
In bays
In headlnads
The energy converges on headlands to have more energy
There is more friction and the wave diverges