COASTS Flashcards
what is a closed system?
transfers energy both into and beyond the system. NOT A TRANSFER OF MATTER
what is an open system?
matter and energy can be transferred from the system across the boundary into the surrounding environment.
what is positive feedback?
when an effect of an action are amplified or multiplied by its knock on effects
what is negative feedback?
where the effects of an action are nullified by its knock on effects.
inputs into coastal system
- tidal energy
- wind energy
- sediment
- changing of sea levels
- current energy
- humans
- tsunamis
- storm surge
outputs into coastal system
- kinetic energy
- sand
- depositional landforms
- erosional lanforms
what are depositional landforms?
- beaches
- mudflats
- sand dunes
- coral reefs
Erosional landforms?
- cliffs
- shore platforms
processes of the coastal system
- erosion
- transport
- deposition
crest definition
highest point of a wave
trough definition
lowest point of a wave
backwash
any water returning down to the sea
wave height
distance between the crest and the trough, rarely exceeds 6 metres unless storm conditions.
swell
waves of low height, gentle steepness, long wavelength and period.
wave velocity
speed of movement of a crest in a given period
wave steepness
is the ratio of wave height to wavelength
swash
the body of foaming water rushing up the beach
wave length
the distance between two successive crests
what does the energy obtained by the waves depend on?
- wind velocity
- length of fetch
- period of time during which the wind has blown
- depth of water
what are waves?
the main input into the coastal system
what does the size of a wave depend on?
it’s fetch
what are constructive waves?
depositional waves as they lead to sediment build up
destructive waves
destroy beaches
features of constructive waves…
- low waves
- strong swash
- weak backwash
- break on the shore and deposit material
- associated with calm weather
- less powerful waves
features of destructive waves…
- waves are high and frequent
- backwash has less time to soak into sand
- destructive waves create steep narrow beaches
- associated with storm weather
what are longshore currents?
occur as most waves hit the coast at an angle. they transport material along the coast
what are rip currents?
strong currents moving away from the coast, they develop when seawater is piled up along the coastline.
what is upwelling?
the movement of cold water from the deep ocean towards the surface.
what are tides the result of?
gravitational pull of the moon and the sun
what has the greatest influence over tides
the moon
what is tidal range?
the difference between high tide and succeeding low tide
what does the gravitational pull of the moon do?
the moon pulls water towards it creating a high tide and there is a compensatory bulge on the opposite side
what is spring tide?
the moon and sun are aligned which means you get the highest high tide and the lowest low tide - greatest tidal range
what is neap tide?
the moon and sun are proportional at 90 degrees lowest high tide and the highest low tide- smallest tidal range
where are tidal ranges high and where are they low?
mediterranean sea- low
british isles - high
what influence does the tidal range have?
a wide zone of wave attack which results in wave cut platforms being formed
what are the sources of coastal sediment?
seabed beaches river channels/estuaries erosion from cliffs material from biological origin
what are the inputs of sediment cells?
from the river, coastal erosion and offshore sources such as banks and bars
what are the transfers of sediment cells?
longshore drift and rip currents
what are the outputs of sediment cells?
beach
sand dunes
offshore deposits
what is wave refraction?
- shallow water around headland which increases friction
- causes waves to break at headland
- waves refract into bays
- energy is dissipated into the bays
what is a sediment cell?
`the length of coastline within which the movement of sediment is largely self-contained
high energy coastline
often have high wave power for most of the year
what is longshore drift?
longshore drift occurs when waves approach the beach at an angle material is pushed up the beach in the swash in the direction of the dominant wind and is then pushed back out to sea in the backwash due to gravity. this is the zig zag effect
what are the four strategies for coastal management?
do nothing
hold the line
managed retreat
advanced the line
what are groynes?
wooden barrier built at right angles to the beach they prevent the movement of material along the coast by longshore drift
4 types of erosion
hydraulic action
abraision
solution
attrition
4 types of transportation
solution
saltation
suspension
traction
what is a sub areal process?
a non-marine process
example of a sub-areal process?
weathering
mass movement
what is aeolian deposition?
an important process where wind transports sediment
what is a concordant coast?
exist where rock structure is parallel to the coast
straight coastal plans resulting in a steep cliff face
what is a discordant coastline?
alternating bands of less resistant and more resistant rock
how are sea cliffs and wave cut platforms formed?
when high and steep waves break at foot of cliff energy gets concentrated to a small area of the rock face
- this eventually leads to the cliff being undercut forming a feature called a wave cut notch.
- continued activity at this point increases stress on the cliff and in time it collapses
- the cliff begins to retreat and leaves a gently sloping wave cut platform
factors which encourage deposition
lots of sediment
shallow water
weak current
constructive waves
favourable conditions for growth of spits and bars
bend or change in the direction of the coastline
plentiful load
active long shore drift
environments favouring constructive waves
factors for reducing or stopping growth
reduction in the supply of sand or shingle
deeper water
stronger river or tidal currents
more exposure to storm waves
longshore drift
zig zag movement of material on beach
prevailing wind determines angle of swash
backwash brought back down beach at a 90 degree angle under the influence of gravity
how is a cliff and wave cut platform formed?
destructive waves attack lines of weakness
creates wave cut notch
creates overhang and the cliff collapses into the sea
sediment is removed leaves a wave cut platform
Describe what a spit is…
band of sand and shingle attached to the headland at one end
long ridge of sand extended into the sea/estuary
hooked or curved ends
sand dunes on it
salt marsh behind it
what is a headland?
a cliff which protrudes out into the sea with an alternating band of hard rock and soft rock.
what is a bay?
next to headland an inlet into the coastline wave energy is dissipated into here
where are mudflats found?
found in estuaries where rivers meet the sea or on the landward side of a spit
where do mudflats develop?
they develop on sheltered shorelines that are not exposed to powerful waves
saltmarsh development…
in sheltered areas
where salt and fresh water meet in an estuary
where there are no strong tides or currents to prevent sediment and deposition
explain he formation of a sea stack
Also use this description for cave arch stack and stump
1) destructive waves attack lines of weakness in the rock
2) rock then gets broken down due to erosion
3) explain a type of erosion
4) sea attacks weak points in headland and caves are formed
5) caves are eroded right through the headland to form natural arches
6) over time pressure on the arch due to FTW (explain) causes them to collapse leaving an isolated piece of rock left on its own called a stack
7) between the high and low water marks are eroded on the stack leaving a stump.
describe a spit?
a spit is an elongated band of sand and shingle attached to the headland at one end
explain how a spit forms…
1) form due to LSD (explain)
2) at the headland there is a change in the direction of the coastline and LSD continues in the same direction
3) deposition occurs if 4 factors are present: large load, shallow water, weak current and constructive waves this causes a spit to form.
4) the hooked ends are formed due to a change in the direction of the dominant wind.
5) eventually stops growing due to current strength and depth.
explain how a bar forms…
1) form due to LSD (explain)
2) at the headland there is a change in the direction of the coastline and LSD continues in the same direction
3) deposition occurs if 4 factors are present: large load, shallow water, weak current and constructive waves this causes a bar to form.
4) conditions needed for deposition are always present and therefore doesn’t stop growing
what is sub-areal weathering?
when the weather on the land has an impact on the coastline making removal of material easier and quicker
describe a sea cliff?
A steep cliff at the edge of a coastline which marks the boundary between the land and the sea
describe a wave cut platform?
a rocky wave cut platform which protrudes out into the sea at a 20 degree angle
optimum conditions for sand dunes:
flat land strong onshore winds plentiful supplied of sand vegetation to colonise beach ideally has a low gradient and high tidal range
how do headland and bays form?
- commonly formed when rocks of diffrent strengths are exposed at a coastline- alternating bands of hard and soft rock - discordant coastline
tougher more resistant rocks- headland
weaker rocks eroded to form bays - once formed headland and bays interfere with incoming waves
- make the waves refract which focuses energy on headland waves energy is spread out and reduced in bays which results in formation of beaches
what is wave refraction?
shallow water is present around the headland. friction becomes increased this causes waves to break at the headland and energy gets dissipated into the bays.
what is a concordant coastline?
exist where rock structure is paralell to the coast.
straight coastal plans resulting in a steep cliff face
what is a discordant coastline?
form irregular coastlines.
alternating bands of hard rock and soft rock along the coastline
how do tombolos develop?
develop where a spit joins an island to the mainland deposition occurs where waves lose their energy
what is flocculation?
as seawater and riverwater meet the fine particles settle out of suspension by the process of flocculation
where the individual clay particles aggregate together to form larger heavier particles which are more difficult to erode and transport
what are the conditions needed for sand dunes to form?
flat land strong onshore winds plentiful supplies of sand vegetation to collonise dunes beach ideally has a low gradient and high tide
what are the threats to dune systems?
over-grazing
recreation is a major land use on sand dunes
sea level change due to global warming leading to an isostatic increase in sea levels is a threat to sand dune environments
what are the actions which can be taken to take care of sand dunes?
cordoning off areas
restricting public access
stabilization of dunes by planting things
giving tourist information about potential damage
the transforming of potentially bio diverse stretches of dunes into nature reserves
what are aeolian processes?
the action of wind
natural causes of eustatic sea level change?
climate cools
climate warms
steric effect
human causes of eustatic sea level change?
climate warms
steric effect
natural causes of isostatic sea level change?
tectonic activity
glacial rebound
river and wetland modification
human causes of isostatic sea level change?
extraction of resources
why does sea level fall?
interglacial periods
water is stored on land as ice
land emerging
why does sea level rise?
ice melting due to increased temperature/global warming
thermal expansions of the oceans because its warmer
subsidence of the land
what is eustatic?
global change
what is isostatic?
local change
what are erosional landforms?
headland and bays wave cut platforms blowhole geo sea cliffs
what are depositional landforms?
spit bars tombolo mudflats and salt marshes beaches sand dunes
what are the three types of sea level change?
eustatic
isostatic
tectonic
what causes coastal flooding?
global warming
storm surges
tsunamis
human= global warming
coastal management
what is eustatic sea level change?
result of global sea level change
when ice melts the volume of water increases so sea level rises global warming is increasing sea levels due to thermal expasions of the ocean as the water gets warmer.
what is isostatic sea level change?
occur on a regional/local scale. result of the weight of ice when large ice sheets cover the land the land sinks. when the ice melts the land rises back up as the weight is removed. this is called isostatic reajustment
what are landforms of a eustatic fall in sea level and isostatic reajustment?
raised beaches
relict cliff lines
marine platforms
what are the landforms of a eustatic rise in sea level and an isostatic fall in land
rias
fjords
dalamation coastlines
what are the 5 aims of coatal management?
- to provide defence against and mitigate the impactts of flooding
- to provide protection against and mitigate the impacts of coastal erosion
- stabilising beaches affected by LSD
- stabilising sand dune areas
- protecting fragile esturine landcapes
hard engineering strategies?
cliff fixing revetments offshore reefs barrages sea wall gabions groynes rock armour/rip rap
soft engineering strategies?
beach nourishment dune regeneration managed retreat land use management do nothing
