coasts Flashcards
features of destructive waves
high frequency
high
steep
features of constructive waves
low frequency
low
long
destructive waves
backwash is more powerful than swash so material is removed
how do constructive waves build beaches
swash is more powerful than backwash so material is deposited
mechanical weathering
breakdown of rock without changing it’s chemical composition
e.g. freeze thaw weathering
chemical weathering
breakdown of rock by changing its chemical composition
e.g. carbonation weathering
process of freeze-thaw weathering (mechanical)
- water enters rock that has cracks
- it freezes overnight which makes the crack bigger
- in the day, it melts and more water fills into the crack
- the water freezes again making the crack bigger
- this repeats until the rock breaks
process of chemical weathering
- rainwater has carbon dioxide dissolved in it —> makes it a weak carbonic acid
- carbonic acid reacts with limestone —> so rocks break
define hydraulic action
waves crash against rock and pushes air into cracks —> the force of this causes bits of rock to break off
define abrasion
loose rocks (sediment) are thrown against the cliff by waves. this wears away at the cliff and chips bits of rock
define attrition
eroded particles in water collide and knock into each other to become smaller and more rounded
define solution
seawater dissolves material from the rock
what is mass movement
shifting of rocks and loose material down a slope e.g. a cliff
why does mass movement happen
it happens when the force of gravity acting on a slope is greater than the force supporting it
define slide
material shifts in a straight line along a slide plane
define slump
material rotates along a curved slip plane
define rockfall
material breaks up and falls down a slope
3 types of mass movement
slides
slumps
rockfall
describe longshore drift
- waves follow the direction of the prevailing wind and approach beach at an angle
- swash carries material up the beach at the same angle
- backwash carries material straight back down the beach at right angles
- overtime, material moves along beach in zigzag pattern
define deposition
when water loses energy and drops the material it is carrying
when does deposition on an area of a coast increase?
there’s lots of erosion elsewhere (so more material is available)
how do headlands and bays form
- alternating bands of resistant and less resistant rock
- less resistant rock is eroded faster, forming a bay
- resistant rock erode more slowly and forms a headland which sticks out
forms along discordant coastlines
how is a wave cut platform formed
- sea attacks base of cliff forming a wave cut notch
- repeated erosion causes rock above notch to become unstable and it eventually collapses
- collapsed material is washed away and a new wave cut notch starts to form
- repeats, the cliff retreats, leaving a wave cut platform
how do caves, arches, stacks and stumps form
- resistant rock headland have cracks
- abrasion and hydraulic action widens the cracks
- repeated erosion of cracks causes cave to form
- continued erosion deepens the cave until it breaks through the headland to form an arch
- arch is eroded until the roof collapses leaving a stack
- stack eventually collapses leaving a stump
example of hard rock and soft rock
hard rock - granite
soft rock - sandstone
define discordant coastlines
alternating bands of hard and soft rock at right angles to the coast
define concordant coastline
alternating hands of hard and soft rock that are parallel to the coast
how are sand beaches formed
constructive waves build up beaches as they have a strong swash and a weak backwash
form in sheltered areas like bays where waves have limited energy
how are shingle beaches formed
high energy waves and are steep and narrow
sand particles are washed away but larger shingle left behind
what is a bar
a bar forms when a spit joins 2 headlands together
how is a bar formed
- a bar forms when a spit joins 2 headlands together
- bay between headlands gets cut off from the sea
- lagoon forms behind the bar
what feature lays behind a bar
lagoon
why do spits have a hooked or recurved end
strong winds and waves can change the direction of it
what are spits
long narrow ridges of sand and shingle stretching out from the coast
how is a spit formed
- longshore drift transports sand and shingle past the bend and deposits it in the sea
- strong winds and waves can curve the end of a spit (forming recurved end)
- area behind the spit is sheltered from waves so material accumulates and plants are able to grow
- overtime, the sheltered area can become a mud flat or a salt marsh
what feature lies behind a spit
salt marsh and mud flats
what 3 features are formed by deposition
spits, bars, sand dunes
how are sand dunes formed
- Sand is blown over an obstacle like a dead animal or a rock by wind
- When the sand comes into contact with the obstacle, the wind slows down and the sand is deposited
- This forms an embryo dune
- Over time, plants like Marram Grass stabilise the sand and encourage more sand to accumulate there
- The dunes steadily get bigger as you move back from the coast because the amount of vegetation increases.
- d’une slacks can form in hollows between dunes
what grass grows on sand dunes and holds them in place
marram grass
coast
A part of land that joins the sea.
what causes waves to form
Wind blowing over the sea
What does the size and strength of waves depend on?
• How strong the wind is
• How long it blows for
• How far it travels
swash
Water rushing up the beach
backwash
Water draining back down the beach
fetch
The distance a wave has travelled
constructive waves
Waves that have a very strong swash and a weak backwash
They build up the beach
marine processes
The base of cliffs being eroded by hydraulic action and abrasion
waves associated with coastal erosion
Destructive waves
erosion
Wearing away of rocks by water, weather or ice
4 types of erosion
- Hydraulic action
- Abrasion
- Attrition
- Solution
How is sediment transported along the coastline?
longshore drift
define landform
A feature in the landscape that has been formed by erosion, transportation and/
or deposition.
What factors influence the landforms found along a coastline?
Hard rock (resistant rock) - does not erode easily - likely to find headlands
Soft rock (less resistant rock) - erodes easily - more likely to be a bay
coastal landforms that result from erosion
- Headlands and bays
- Cliffs
- Wave cut platforms
- Caves, arches, stacks and stumps
coastal landforms that form as a result of deposition
- Beaches
2 Sand dunes - Spits
- Bars