coastal systems and landscapes

give a costal example of stores/components

- beaches
- sand dunes

define an input

material or energy moving into the system from outside

give a coastal example of an input

- precipitaion
- wind

define an output

material or energy moving from the system to the outside

give a coastal example of an output

- ocean currents
- rip tides
- sediment transfer
- evaporation

define energy

power or driving force

give a coastal example of energy

- wind
- waves
- tides
-currents

define stores/ components

the individual elements or parts of a system

define flow/transfers

the links or relationships between the components

give a costal example of flow/transfers

-wind blown sand
-mass movement
- longshore drift

define positive feedback

where a flow or transfer leads to increase or growth

give a costal example of positive feedback

coastal management can lead to an increase in erosion
- groynes trap sediment, depriving areas further down drift of beach replenishment
- seawalls transfer high energy waves elsewhere

define negative feedback

where a flow or transfer leads to decrease or decline

give a coastal example of negative feedback

when the rate of weathering and mass movement exceeds the rate of cliff- foot erosion a scree slope is formed. over time, this material extends up the cliff face protecting the cliff face from subaerial processes leading to a reduction in the effectiveness of weathering and mass movement.

define dynamic equillibrium

a state of balance within a constantly changing system

give a coastal example of dynamic equilibrium

- constructive waves build up a beach, making it steeper, encouraging the formation of destructive waves that plunge rather than surge
- redistribution of sediment offshore by destructive waves reduces the beach gradient which then encourages the waves to become more constructive.
- this is a state of constant dynamic equilibrium between the type of wave and the angle of the beach

what source of energy produce wave and what direction does it come from in the UK

- wind
- from the south-west

what are the 3 factors affecting wave size/energy

- wave strength/speed
- wave duration
- fetch (the distance of open water over which the wind blows)

explain how waves are formed

- waves have a circular orbit, when the water becomes shallower it changes to an elliptical orbit
- wavelength and velocity decrease and wave height increases causing water to back up from behind and rise until it breaks
- it rushes up the shore as swash and then flows back as backwash

what are the top and bottom of a wave called

crest and trough

give the characteristics of constructive waves

- caused by distant weather systems
- long wavelength, lower frequency
- strong swash, weak backwash
- doesn't reach foot of cliff
- wave energy absorbed by beach

give the characteristics of destructive waves

- caused by local storms
- short wavelength, higher frequency
- weak swash, strong backwash
- upper part of cliff attacked by spray
- little wave energy absorbed by beach

define tides

change in water level of seas and oceans caused by gravitational pull

explain a neap tide

- lower high tides, higher low tides (gravitational pull against)
- small tidal range (energy concentrated on small section of cliff for a longer amount of time)

explain a spring tide

- higher high tides, lower low tides (gravitational pull act together)
- large tidal range (erosion of cliff is spacially concentrated at a specific level for shorter amount of time)

define a rip current

strong localised underwater currents that occur on some beaches bringing possible danger to swimmers and surfers

how are rip currents formed

- a series of plunging waves cause a temporary build up of water at the top of the beach.
- meets with resistance from breaking waves, backwash is forced just below the surface, following holes in sandbanks

explain high energy coastlines

- stretches of coastline where waves are powerful
- rate of erosion exceeds rate of deposition
- landforms include headlands, cliffs and wave cut platforms

eg cornwall and scotland

explain low energy coastlines

- stretches of coastline where waves are not powerful
- rate of deposition exceeds rate of erosion
- landforms include beaches and spits

eg lincolnshire

explain wave refraction

- the distortion of wave fronts as they approach indented shorelines
- energy is concentrated at headlands (high wave energy and erosion) and dissipated in bays (low wave energy and disposition)

sources of sediment

-rivers
-cliff erosion
-longshore drift
-wind
-glaciers
-offshore (waves tides currents)

define a sediment cell

a stretch of coastline, usually bordered by 2 prominent headlands, where the movement of sediment is more or less contained

give the inputs, transfers and stores (sinks) of sediment cells

input - rivers, coastal erosion, offshore sources
transfers - longshore drift, rip currents
sinks - beach, sand dunes, offshore deposits

explain sediment budgets

the balance between inputs and outputs with losses and gains
- losses involves deposition in sediment sinks
- gains involve coastal erosion or sediment brought in through rivers and offshore sources

what is weathering

the breakdown or disintergration of rock in situ (its original place) at or close to the ground surface relentlessly

describe how positive feedback could occur from weathering

if the rate of debris removal exceeds the rate of weathering and mass movment as weathering and mass movement would increase

describe how negative feedback could occur from weathering

if debris removal is slow and ineffective, there would be a build up of debris that reduces exposure of a cliff face, weathering and mass movement would decrease

define mechanical/physical weathering

the breakup of rocks without any chemical changes taking place

what are the 3 types of mechanical weathering

frost shattering, salt crystillisation and wetting and drying

what is frost shattering

- when water enters rock cracks, freezes and expands by 10%
- expansion widens the cracks causing rock fragments to break away and collect at the base of cliffs
- used by the sea in marine erosion

what is salt crystallisation

when salt water evaporates it leaves salt crystals behind which can grow over time and exert stresses in the rock breaking it up

what is wetting and drying

when rocks rich in clay expand when they get wet and contract as they dry, causing them to crack and break up

define biological weathering

the breakdown of rocks by organic activity

explain biological weathering

- when plants grow roots into small cracks in a cliff face and widen the cracks at they grow, breaking up the rock
- water running through decaying vegetation becomes acidic, which leads to increased chemical weathering

define chemical weathering

involves a chemical reaction where salts may be dissolved or form a clay like deposit which is then eroded

what are the 3 types of chemical weathering

carbonation, oxidation, solution

explain carbonation

rainwater absorbs carbon dioxide, forming weak carbonic acid, which reacts with calcium carbonate in rocks like limestone and chalk to create soluble calcium bicarbonate

explain oxidation

the reaction of rock minerals with oxygen to form rusty red powder leaving rocks more vulnerable to weathering

explain solution

the dissolving of rock minerals

define mass movement

the downslope movement of soil and rock due to gravity, can be slow or fast

what are the 5 types of mass movement

creep, mudflow, landslides, rockfall, slumps

explain creep

• common in humid climates with movement of less than 1cm per year 

• soil expands when it freezes, gets wet or is heated up in the sun

• as the soil expands, it lifts at right angles to the slope

• when the soil shrinks, it falls straight back down

• leads to bent trees, cracked roads, leaning poles etc

explain mudflow

• quite rapid movement caused by heavy rain that moves large amounts of material to move down steep slopes

• usually involves saturated slopes where there are weak rocks such as clay

• water gets trapped within the rocks, increasing pore water pressure leading to slope failure, vegetation is flattened and carried away

explain landslides

• rapid movement of material which remains together until hitting the bottom of a slope

• triggered by earthquakes of heavy rainfall that causes the land to be lubricated (less friction)

• can be dangerous eg Holbeck hall Hotel 1993

explain rockfall

• the sudden rapid collapse or breaking away of individual rock fragments at a cliff face, on steep slopes

• triggered by

  • freeze-thaw (loosens rocks becoming unstable)

  • rainfall (softens surface leading to collapse)

  • earthquakes (dislodge unstable rocks)

  • hot weather (dries out soil causing it shrink, allowing rocks to fall)

explain slumps (landslips)

• usually found on weaker rock types (i.e. clay), that become saturated and heavy

• involves a large area of land moving down the slope in one piece

• leaves behind a curved indented surface

define marine erosion processes and give the 6 types of it

it is the wearing away of the land surface and removal of materials by water and sea

• hydraulic action

  • cavatation

  • wave quarrying

• abrasion (corrasion)

• attrition

• corrosion (solution)

explain hydraulic action

• when sea water forces air into cracks and joints in the rock

• the pressure from the waves on this air causes the cracks and joints to expand and weaken, causing pieces to break off

explain cavitation

• bubbles formed in the water may implode under high pressure generating tiny jets of water which over time erode the rock

explain wave quarrying

• the action of waves breaking against unconsolidated large material such as sands and gravels and scooping out the loose material

explain abrasion (corrasion)

• when material in the water crashes against the coastline

• sediment is dragged across the shoreline, eroding and smoothing rocky surfaces

explain attrition

• when rocks in the water bash against each other and break up, gradually becoming rounder and smoother

explain corrosion (solution)

• a chemical process where weak acids in sea water wear away and dissolve alkaline rocks and cement that bond rock particles together

what are the four methods of marine transportation explain each one

• traction - large boulders and rocks rolled along the riverbed

• saltation - small pebbles and stones bounced along the river bed

• solution - minerals dissolved in water

• suspension - fine light material carried by the river

explain longshore drift

• prevailing winds and waves come from the south west

• swash comes up the beach from a angle

• then backwash comes straight back down due to gravity

• this repeats leading to longshore transport of sediment in that direction

what is marine deposition

• when the carrying capacity of water decreases below a critical value

• water drops the finest particles first so there can be sorting

• this deposition forms landforms (sediment sinks) like beaches, spits etc

what are the three landforms of coastal erosion

• cliffs and wave cut platforms

• headlands and bays

• arches and stacks

explain how cliffs and wave cut platforms are formed

• water erodes (hydraulic action and corrosion) the cliff at a high water mark creating a wave cut notch

• as the notch gets bigger, the cliff is undercut and rock above it becomes unstable, collapsing

• these erosional processes repeat, causing the notch and cliff to retreat inland leaving behind a wave cut platform

how are headlands and bays formed

• occurs when the sea erodes a discordant coastline

• less resistant rock is eroded more easily, creating bays ( eg swanage bay)

• more resistant rock is eroded at a slower rate, creating headlands ( eg durlston head)

explain how caves arches and stacks are formed

• firstly the sea attacks the cliff and erodes the areas of weakness causing cracks

• these cracks get larger as more sub-aerial processes occur and develops into a small cave

• the cave is widened and deepened until it cuts through the headland to form an arch

• further erosion causes the arch to collapse leaving part of the cliff detached as a stack

• the stack may also collapse and form a stump

what are the 6 landforms of deposition

• beaches

• simple and compound spits

• tombolos

• offshore bars

• barrier beaches

• sand dunes

how are beaches formed

• beaches build up due to constructive waves

• they can be drift-aligned or swash-aligned 

  • drift-aligned beaches form where longshore drift moves the sediment along the beach as waves approach at an angle often resulting in a spit

  • swash-aligned beaches form where the energy is low and when the waves are more parallel to the shore, there is less lateral movement of sediment

• characteristics of a beach include berms (ridges) and cusps

how are simple and compound spits formed

• prevailing winds from the SW cause longshore drift that transports material along the coastline

• when the coastline changes, it reaches shallower water (or rivers and eustaries)

• the material being transported is deposited along the direction of the original coastline

• it accumulates over the years, creating a spit

what is an example of a simple or compound spit

Hurst Castle spit

how are tombolos formed

• prevailing winds result in a drift aligned beach and longshore drift

• sediment is carried by longshore drift until their is a change in the coastline or where waves lose energy and a spit is formed

• the spit builds up from the mainland and then joins to another island forming a tombolo

what is an example of a tombolo

Bruny Island tombolo, Japan

how are offshore bars formed and what can they do

• destructive waves erode sand from the beach with a strong backwash and deposit it offshore

• offshore bars are the submerged or partly exposed ridges of sand or coarse sediment that has been deposited

• acts as a sediment sink by absorbing wave energy

how are barrier beaches formed and give an example

• when one spit joins one part of the mainland from another across a bay (forming a lagoon)

  eg Looe bar, Cornwall

what 3 conditions are needed for a sand dune to form

• lots of sand (from longshore drift)

• wind blowing in the correct direction (bringing sand up the beach onshore)

• a flat dry area

how and where does wind transport sand for sandunes

• saltation moves sand up the beach in a bouncing action where it collects in the lee of a berm

how are sandunes formed and what role does vegetation play

• embryo dunes form from the placement of sand

• sea couch grass has spreading roots that binds the sand together

• once the dune is about 1m high, marram grass forms and replaces the sea couch grass with its long roots

• this continues to grow till about 10-20 metres which is now a yellow dune

• the marram grass dies and decays adding humus to the sand

• the humus forms a soil with the sand which allows plants to grow (eg dandelions), now called a semi-fixed or grey dune

• as soil depth increases and becomes damper more plants grow over (eg lichen, moss etc), now a fixed dune

• dune systems get bigger so water can collect in dune slacks allowing climax vegetation to happen

what is a salt marsh

a damp area with vegetation associated with shallow, saline waters near the coast

occurs on muddy shores between approximately mean high water neap tides and extreme high water spring tides

what are the conditions necessary for a salt marsh to form

• a sea shore with very little waves action so fine particles can fall out of suspension

• saline conditions for fluctuation to occur (neutralisation of clay particles so they cling together and are deposited)

• shelter from exposure eg a river or estuary behind a spit

• a source of mud

describe the stages of formation of a saltmarsh

1. the development of a landform of deposition such as a spit produces extremely sheltered conditions in the lee of a landform

2. allows clay particles to flocculate and settle and deposit in the sheltered area (this is added to microscopic algal growth which adds to the mud creating more sediment)

3. mudflats develop which are exposed at low tides

4. mudflats are colonised by pioneer species such as cord grass, spartina and eel grass

5. over time the salt tolerant plants trap more mud and these spend a longer period of time exposed. in addition, dying plants and humus add nutrients to the soil making conditions less hostile

6. competition between pioneer species which grow quickly and die young competing with those that may take longer to grow but and stronger and will eventually dominate

7. number of species increases as abiotic factors become more favourable

8. as mud levels rise, complex creek systems that channel the flowing tides develop

9. eventually the land rises above sea level and new species such as reeds and rushes become established

10. finally the climax stage of here trees can develop

define isostatic change and give an example

the result of an increase or decrease in land levels

eg landsend in cornwall is decreasing by 1.1mm each year

what causes isostatic change

post glacial adjustment heavy ice sheets weigh land down, when it ends and ice melts, land rebounds to higher levels

accretion net disposition causing land to build up

subsidence increased deposition weighing down sediment

tectonics folding of sedimentary rock eg lava and ash from volcanoes increases height of land relative to sea level

define eustatic change

result of an increase or decrease in volume of water in oceans

what causes eustatic change

changing amounts of ice at the end of the ice age 10 000 years ago sea levels rose rapidly due to melting ice, can also decrease as water is locked in ice sheets and glaciers

thermal expansion as water warms, warmer fluids expand taking up a greater volume

tectonics magma rises to the surface, lifts crusts, reduces capacity of oceans, increasing sea levels

what is the general pattern of sea and land level changes in the past 10 000 years

the formation of glaciers and ice sheets decreases sea and land levels and water is locked in ice sheets and forces pressure down on land

as the climate has got warmer, ice sheets have melted increasing sea levels and causing land to rebound back

what are rias and are they submergent or emergent

• have a V-shaped cross-section caused by flooding of valleys

• an estuarine coastline

• most common coastal landform

• submergent

what are dalmatian coasts and are they submergent or emergent

• when a landscape of valleys and ridges are parallel to the coastline the low parts of the valleys will be flooded when sea level rises 

• exposed tops of the ridges become small offshore islands parallel to the coast 

• eg the dalmatian coast in croatia that the landform is named after 

• submergent

what are fjords and are they submergent or emergent

• U-shaped valley carved out by a powerful glacier

• relatively straight profile, steep sided

• maybe deeper than the adjacent sea

• submergent

what are raised beaches/marine platforms and are they submergent or emergent

• beaches which are above high tide level

• flat and covered by sand/pebbles

• experience succession 

• eg Scottish islands of Islay, Jura, Colonsay and Mull

what are the predictions for future climate change

IPCC predicts that sea levels by 2100 will be between 0.3 - 1.0m higher than they are now 

• could inundate many coastal cities and settlements (75% of world cities are coastal)

• could also salinise aquifers in low lying regions eg tuvalu, bangladesh, kiribati and increase coastal erosion (more than 1 billion people live on high risk coasts)

what is hard engineering

man made coastal management technique used to protect coasts

absorb energy of waves, prevent erosion and flooding

however are ugly, expensive and can have detrimental effects further down the coast

what are groynes

wood or boulder fences that trap sediment as it is transported by longshore drift

beach builds up which absorbs wave energy 

what are the pros and cons of groynes

pros

• builds up the beach

• provides calm water

• encourages tourism

cons

• need maintenance

• doesn’t prevent strong waves

• sediment starvation further down the coast

what are sea walls

walls with a curved or stepped surface that absorb and reflect wave energy

what are the pros and cons of sea walls

pros

• effective

• lasts a long time

• promotes tourism as forms pathways

cons

• expensive

• ugly and intrusive

what is riprip/rock armour

granite boulders which have spaces in between causing waves to bounce between many surfaces, reducing the energy of the wave