Coastal Systems and Landscapes from notes Flashcards
What type of system is the coast?
An open system
What are the inputs into the coast?
Wind Waves Sediment Sea levels tide currents
What are the outputs of the coast?
Energy
Taking away of sediment
What are the stores of a coast?
Beach rocks stumps stakes bay coves spits, bars features of erosion features of deposition
The dynamic Equilibrium in coastal systems is affected by?
- The supply of sand
- The energy of the waves
- Changes in sea level
- Location of the shoreline
What are the 4 parts of a beach?
Offshore
Nearshore
Foreshore
Backshore
Label a wave
crest
trough
wavelength
wave height
What are the 4 sources of energy?
Waves
winds
Tides
sea currents
Why does a wave break?
As waves a[[roach shallow water, friction with the seabed increases and the base of the wave begins to slow down. This has the effect of increasing the height and steepness of the wave until the upper port plunges forward and the wave breaks.
What ratio does a wave need to break?
(1:7)
What affects the amount of energy a wave has?
Fetch
duration of wind
direction of wind
What are the 2 types of wave?
Constructive
Destructive
What characteristics do destructive waves have?
Stronger backwash weaker swash higher wave height higher frequency shorter wavelength 14/min high energy steeper beaches plunging
What characteristics do constructive waves have?
Weaker backwash weaker swash smaller wave height lower frequency 6-8/min long wavelength low energy spilling gentle beaches
What is a spring tides?
Takes place when the earth sun and moon are inline
happens on day 14 and 28
What is a neap tide?
Happens on day 7 and 21
a lower tide when the moon is at a 90 decree angle to the sun.
Tides vary due to:
The morphology of the sea bed- affects the speed of travel
proximity of land masses- shore, headlands ect.
coriolis force
What are the stages of wave refraction?
When waves approach the coastline they begin to refract
waves in shallow water slow down due to friction with
the sea bed
Waves become parallel to coastline
The part of the wave in deeper water moves forward faster causing the waves to bend.
Therefore energy is on the headland causing eurotion. the rest of the wave has less energy therefore de[ostion takes place
What are the different ocean currents?
- Longshore currents
- Rip currents
- Upwelling
Longshore currents-
Longshore drift, causing a flow of water parallel to the coast
Rip currents-
Move away from the coastline, may start parallel and then where there is a headland head out to sea.
Fastest 8ft/second
Upwelling
wind blow away surface (warming) water allowing cold water, which full of nutrients, makes its way up to the surface.
What are the processes of erosion?
Attrition solution Abrasion Hydraulic action Quarrying
Attrition-
Material being carried by the sea hit against each other becoming smaller, rounder and smoother
Solution-
Rocks, normally limestone or other rocks containing carbon, are dissolved through rainfall
Abrasion
Material is used by the waves eg. shingles which is thrown at the cliff.
Hydraulic action
Sheer force of the water puts pressure on the rocsks and forced them apart
Quarrying-
Cavitation which traps air causing huge pressure, which is released when wave withdraws.
What are the processes of transportation?
Solution
suspension
saltation
traction
solution-
minerals are dissolved and are carried in the water
suspension-
particles are carried along in the water
saltation-
the sediment bonces along the bed of the river and dislodge other particles.
traction-
the bedload rolls along the sea bed.
When does Deposition occur?
Where the water loses energy.
Give 4 examples of how a wave loses energy leading to deposition.
- The wave slows down after breaking
- where accumulated;ation is quicker than removal
- where the coastline changes direction
- Just before backwash
Aeoil-
carried/deposited by the wind
How is the wind different at the coastline from day to night?
Day- Warm air rises from the land
Wind from shore
sinks over the colder sea
Cooler wind blown back to land across the sea
Night- warm air rises from the sea
Wind to shore
sinks over the cooler land
cooler wind blown back to sea
how does sand move?
surface creep- rolls
Saltation- bounces
Sub-aerial :
under the air
What are the 3 types of Weathering?
Mechanical (physical) weathering
Chemical weathering
Biological weathering
What are the 4 types of Mechanical (physical) weathering?
Freeze-thaw
Salt crystallisation
Wetting and Drying
Exfoliation
Freeze-thaw
Water enters cracks, expands 10%, puts pressure on rocks until they crack and break. They shattered, angular fragments are found at the back as scree (talus)
Salt crystallisation
Similar to freeze-thaw, salt crystals are deposited in cracks and accumlate
Wetting and Drying
Common on the coastline, in the inter-tidal zone, with clay and shale which expands when wet and contracts when dry. This produces cracks which are vulnerable.
Exfoliation
Rocks under considerable heat will expand and then cooled by the sea causes rapid contraction. This is repeated process causes the outer layer to crack and peel off.
What are the 2 types of Chemical weathering?
Carbonation
Oxidation
Carbonation-
Sea and rain absorb carbon dioxide forming carbonic acid which then dissolves the calcium carbonate in rock such as limestone or chalk into calcium bicarbonate, especially in crakes and joints
Oxidation-
Rocks containing iron (ferrous) compounds experience this earn turned into a ferric state (rusting) when oxygen and water are available leading to disintegration.
Biological weathering-
Growing plant roots widen cracks in the windy conditions theses can widen. On the coastline the piddock frills holes in the rock, puffins excavate nets and seaweed can move in storm conditions leaking rocks
What is mass movement?
Involving the downhill movement of material under the influence of gravity.
What is the range of movement in mass movement?
1cm per year to incredibly fast
Why is mass movement important?
It forms an import group of processes and flows within the coastal systems, transferring both energy and mass
What are the different types of mass movement?
Soil creep rotational slumping Landslide Mudslide Runoff
What is soil creep?
How fast does it happen?
Why does it take place?
What is it caused by?
- Very slow movement downhill (1cm/yr) or individual soil particles
- Particles dislodged bay raindrops or wave splash and typically freeze-thaw or wetting and drying
- caused by gravity (more than 5 degree angle needed)
What is rotational slumping?
- Heavy rain infiltrates unconsolidated soil Eg. Gacial till (east coast)
- Imperab;e soil traps water adding weight
- undercutting causes collapse on slip plane
Rock falls:
Due to physician weathering
Weaknesses exposed and can no longer support itself
Landslides:
Significant section
Unconsolidated, shales and sandstone
Sudden
Usually been lubricated- rain ect
Mud slides:
Excessive amounts of rainfall
Infiltration can’t take place as soil is saturated
Fine particles of mud
Run-off:
Intense rainfall
Impermeable surface
Transports fine material
Might also be transported by a river
Talus/scree:
The material left at the bottom of a slope
Landscape:
are the bigger- the entirety of the sea, coast and the rolling countryside
Landforms
are individual components of the landscape- cliffs, beach and the emerging wave-cut platform
Wave-cut Platforms:
When waves break against the foot of a cliff, erosion tends to be concentrated close to the high-tide line. This created a wave cut notch.
As the erosional processes are repeated (hydraulic action, abrasion), the notch migrates inland and the cliff retreated leaving behind a gently sloping wave-cut platform, which is usually only completely exposed at low tide.
What slope does a wave-cut platform normally have?
Less than 4 degrees
What angle is a discordant coast line on?
What land forms can be found?
Discordant is at 90 degree angle
Bays, headlands
Stumps, stacks, arches, caves
What angle is a concordant coast line on?
What land forms can be found?
Concordant- parallel
Coves
What type of rock are bays formed on?
Weak
What type of rock are headlands formed on?
Resistant
What is a Discordant coast line?
Give an example?
is where the bands of different rock run at right angles to the coast. Headlands and bays usually form if the resistance of rock type is varied.
An example of a discordant coast is the isle of Purbeck, Dorset, UK
What is a concordant coast line?
Give an example?
is where the bands of different rock run parallel to the coast. It results in some distinctive landforms.
Examples of concordant coasts include South Dorset coast line and Dalmatian coast Croatia
Geomorphology-
the shape of the coastline eg. refraction
Lithology-
The physical properties of a rock such as its resistance to erosion- the rock type
Structure-
Whether the rocks run parallel or perpendicular, joints and bedding planes
What is a beach?
A depositional landform, extending from highest to the lowest tide. It is a store which is constantly changing according to the type of waves.
What does the large material on single beaches result in?
Large material results in gaps between the particles. This allows water to percolate through it resulting in less water returning to the sea. This means the backwash is weak and has little energy to move material back down the beach. High friction levels add to this and so material is deposited up the beach resulting in a steeper beach profile.
On a single beach what is the distortion of material like?
Why?
By the cliff material larger and more angaila
Attrition
Cliff fall
Storm waves
Weak backwash
Sand beaches:
Sand beaches
Small particles eg. sand packs tightly together leaving few gaps for water to percolate between the particles.
What are the characteristics of Swash-aligned beaches?
Low energy Longshore drift Headlands and bays Waves parallel Bay
What are the characteristics of drift-aligned beaches
High energy No drift regular Waves oblique splits
Berms
Series of long ridges running parallel to the sea, marking various tide marks
Storm Berms
The height point the waved despite material
Cusp
An embayment with horns
Ridges and Runnels
The spreading out of the waves energy/work across a wide area of beach tends to produce ridges and intervening depressions called runnels.
The are particularly common on shallow, sandy beaches
Bars-
Destructive waves erode the sand, due to string backwash, deposit it offshore
Off shore bar
Source and a sink
Barrier islands-
Similar to offshore bears but they are always exposed, thought to have been created after the last ice age as material was left behind.
What conditions to sand dunes did to withstand?
Hostile environment Windy Salty Dry Lack of nutrients Poor soil
Plant succession-
Where plants gradually make an area more hospitable for other plants which then take over
What do Sand dunes need to form?
Large supply of sand
Large tidal range
Exposed to the wind
to dry sand and blow inland
What order do the sands dunes go in?
Embryo dune foredune Yellow dune grey dune mature dune
What do Embryo/fore dunes
Have to cope with?
Covered in salt water
Dry conditions
Lack of nutrients
No protection from wind
Pioneer species:
the first colonizing plants that can survive in hostile conditions eg. sea rocket
Pioneer species make dunes less hostile by:
Adding organic matter
Provide protection to plants behind
Help to bind sand together
What grows on yellow dunes and what does it do/have?
Marram grass
Long tap roots
Growth stimulated by burial
Add more nutrients
What do Grey/Muture do/have?
More favourable conditions allow other plants to grow
Finally allowing for climax community eg. Oak trees
Where do salt marshes form?
Estuaries Low wave energy Low river energy Sheltered area low lying and flat Behind spit
How are Mudflats created?
Mudflats are created by the deposition of fine silts and clays in sheltered low energy coastal environments such as estuaries.
What is a saltmarsh?
A saltmarsh is an area of coastal grassland that is regularly flooded by seawater.
Can a Mudflat become a Saltmarsh?
One can become the other though plant succession
What conditions to salt marshes have to cope with?
Inundation by salt water, maybe for 12 hours of the day
Open to the elements
What is the 1st stage of the creation of a saltmarsh?
The growth of Eelgrass. This is a pioneer species
What is the 2nd stage of the creation of a saltmarsh?
Spartina
Two root systems to trap the mud
Fine mat of surface roots
Long thick deep that can secure up to 2 meters of deposited material
What is the 3rd/4th stage of the creation of a saltmarsh?
Pioneers develop vegetation over the mud
Colonisation by the other plants such as sea aster, marsh grass and sea lavender
Growth of dense mat up to 15cm High
Leads to tidal currents slowing and more sediment being trapped, covered only at high tide
Grows by 1-5mm in height/yr
What is the 5th stage of the creation of a saltmarsh?
Greater height
Nearly all ground covered
Only highest tides cover the marsh
Eventually leading to growth of alder, ash then oak( climax community)
Flocculation:
the clay particles coming and sinking to the bottom
How has sea level changed over time?
The sea level rose in stepp upward trend from 22 thousand years ago to 8 thousand years ago and have leveled off since then.
The levels have leveled off when the sunda/viethan shelf and Barbados
Sea levels have risen 120 meters in 22 thousand years
When did the last ice age end?
10,000 years ago
When was the last ice age at its maximum?
20,000 years ago
Eustatic change-
….
What happened to sea levels during and after the ice age?
When the ice age began the sea levels fell as the water rose.
When the ice age ended the water level rose as the ice melted.
The inputs into rising sea sea levels would have been frozen lakes, rivers, glaciers
whats happens during glacial periods?
In glacial periods, the input of precipitation is snow and is stored in ice sheets rather than the oceans which decrease in size resulting in a fall in sea level. At the end of the glacial period as temperatures rise
How much is scotland rising each year?
1.0mm
How much is the east of London sinking each year?
-1.5mm
How much is the midlands sinking per year?
-0.5mm
What is Isostatic change?
The weight of the ice acted like a sea-sae and pushed down Scotland (isostatic subsidence) and raised the south East. Now that the weight of the ice has gone Scotland is rebounding and the South East sinking back down (isostatic recovery).
What is the difference between Eustatic and Isostatic?
Eustatic
- change in sea level
- Global
Isostatic
- change in land height
local
- Happens over a longer period of time
What can change the height if sea level?
Tsunami
Earthquakes
Thermal expansion
What are the figures for the 2004 boxing day tsunami?
- Richer scale
- Location
- Wave height
- Death toll
- How much did the fault line slipp by
- Sea level change
- Land subsidence
9.0 richter scale
Indonesian island of Sumatra worst affected
Banda Aceh - 15m high wave
300,000 died
1600km of the fault line slipped about 15m
Raising of sea bed led to 0.01mm rise in sea level
Land subsided by 1-2 meters
What are the figures for the New Zealnd 2019 Earthquake?
- Magnitude
- What happened to the land
- Sea bed rise
- What happen on the Bay of plenty
- 8 magnitude
- Some areas land subsided and some areas there was uplift
- Along the 10km stretch of the south island
- Seabed risen by 0.5-2m
New Zealand’s most noticeable uplift is on the Bay of Plenty coast near Matata where, at one point, the land was rising by up to 10mm a year, says Hamling. The rate has since dropped to about 3-4mm – still as fast as recent sea level rise.
