coastal landscapes Flashcards
define the coast
the coast is a part of land most affected by its proximity to the sea and the part of the ocean most affected by its close proximity to land
what are the four zones the sea is subdivided into and give a brief explanation of what this is
offshore - beyond the influence of waves
nearshore - breaker zone
foreshore - intertidal zone ( waves mainly break here)
backshore - usually above the influence of waves
define a system
a set of interrelated inputs, processes, flows, stores and outputs that work together to maintain equilibrium
define an open system
a system that is influenced by external factors, energy and matter are input and output
define a closed system
energy can enter or leave but matter cannot
define equilibrium
the point where the system is balanced
define feedback
counteracting a change in the system, this can either be positive feedback or negative feedback
define threshold
the point where the equilibrium can no longer be returned, the tipping point
name at least four inputs to the coastal system
- fluvial, both water and sediment
- precipitation
- solar and kinetic energy
- mass movement from cliffs
- weathering inputs sediment
- sea level rising, ice melt and thermal expansion
what does fluvial mean
rivers
name at least four throughflows to the coastal system ( these involve stores and processes, split your answers into these two categories)
stores:
- beach
- cliffs ( stacks, stumps, arches)
- spits and tombolo
processes:
- transportation
- deposition
- erosion
- tides
name at least four outputs from the coastal system
- evaporation
- offshore transport
- sand mining
- sediment accumulating outside of tidal range
how is equilibrium established in the costal system, give an example
the interconnection and reliance of inputs, throughflows and outputs have on each other
- without erosion from cliffs, there would be no sediment input to the beach, without transportation of sediment, the rockfall wouldn’t make its way along the beech to be deposited
what are the five types of energy operating in the costal system
solar, kinetic, potential, gravitational, geothermal
how does solar energy and kinetic energy impact the costal system
solar - heat powers the water cycle, transferring water from the land to coastal zones and vice versa. also responsible for atmospheric process such as wind which generates waves and current
kinetic - seen in transportation processes
how does potential energy, gravitational energy and geothermal energy impact the coastal system
potential - a cliff may have seaward dip and once there is an interaction with another form of energy it may cause the slumping of the cliff
gravitational - pull of the moon and sun generates tide, can also pull rocks down cliffs
geothermal - responsible for tectonic activity, causing the uplift of seabed or submergence of the coast
how is the coast seen as an open system
there are various inputs from outside the coastal zone such as from river systems. sediment can be transferred as well as energy
how is the coast seen as a closed system
sediment cells are regarded as closed systems as sediment isn’t transferred between them
define a sediment cell
a stretch of coastline within which sediment movement is largely contained
what separates one sediment cell from the other
often coincides with substantial landforms such as rocky headlands.
how many major sediment cells are there in the UK
11
what is a sub cell
smaller scale sediment cells where sediment moves in and out of them freely
how is time significant to the concept of sediment cells
sediment supply and transport changes over a period of time
- rocky headlands are bypassed by sediment from one cell to another during storms
- material can be dragged offshore by wind and tide conditions
- locations that experience high seasonal variation in energy inputs (wind and waves) or sediment inputs
- some stores may relate to processes in geological past
what are sediment budgets used for
used to asses what is happening to sediments within a specified location as it is difficult to account for the various movement of materials within the coastal zone especially as human activity along the coast has grown
what are the natural and human inputs of the sediment budget
natural - rivers, rocks, cliffs, offshore, longshore drift, sand dunes
human - beach replenishment, sand dune and salt marsh reclamation
what are the natural and human outputs of the sediment budget
natural - offshore including deep water sediments, estuary - mudflats and marshes, sand dunes, longshore drift
human - extraction of sand and gravel, dredging, land reclamation
what is a sink
anything that absorbs more of a substance than it releases
what factors make a balanced sediment budget
volume of sediment = volume of sediment stored + volume of sediment out
what factors make an unbalanced sediment budget
volume of sediment in is less than the volume of sediment stored + volume of sediment out
what are the five physical factors effecting the coasts
geology, tides, ocean currents, wind, waves
what is another word for wind
aeolian
why is wind an important factor effecting coasts
the wind generates wave action which in turns causes erosion, transportation and depositional processes
what is the prevailing wind and what direction does this come from in the uk
the dominant direction the wind blows in
- for the UK this is south westerly
what is the fetch and how does this have an impact on waves
the distance of open water the wind travels over. if there is a long fetch, the wind will have more energy creating larger, more powerful waves
at what angle does wind have to travel in for longshore drift to occur
oblique
give three A02 points about how wind impacts the coast
- wind importance varies spatially, it is more influential in places with longer fetch and therefore waves have more power, causing more erosion
- wind varies seasonally, in winter, wind from the North Sea increases in strength
- the angle the wind blows at varies spatially and will determine transportation processes. oblique vs perpendicular
What is the crest, trough and wave height
the crest is the highest surface part of the wave
the trough is the lowest part of the wave
the wave height is the vertical distance between the two
what is the wavelength and wave period
the wavelength is the horizontal distance between two adjacent crests or troughs
the wave period is the duration between two wave crests
what are swell waves and give a few characteristics
waves that form in open ocean, travelling in huge distances from where they are generated from. usually have long wavelengths and a long wave period
what are storm waves and give a few characteristics
generated locally and have a shorter wavelength, greater height and a shorted wave period
what are the three types of breaking waves and give a brief explanation
spilling - steep waves breaking onto gently sloping beaches, water will spill gently forward as the wave breaks
plunging - moderately steep waves breaking onto steep beaches, water plunges vertically
surging - low angle waves breaking onto steep beaches, waves slide forward and may not actually break
what is swash and what is this driven by, what is backwash
water moving up a beach after a wave has broken driven by the transfer of energy. the speed will decrease the further it travels until there is no more energy. the water is then drawn back down the beach as backwash
what happens to waves in deep water and what are the characteristics of waves in deep water
energy from the wind creates friction with the water causing it to ripple in a circular orbit. the wave base doesn’t hit the sea floor as the energy from the wind dissipates before it can.
- waves have a larger wavelength and smaller height
what happens to waves in shallow water and what are the characteristics of waves in shallow water
the wave base starts meeting the seabed creating friction. this friction is strong and slows down the base of the wave, whilst the crest is still moving due to the wind. this decreases wave length whilst increasing height. the potential energy stored in the wave is activated when the depth of the wave is less than 1.3 x the height. the waves then crash due to gravity
- wave length is reduced and wave height increases
what are the two types of waves
constructive and destructive
what are the main characteristics of constructive waves that differentiate them from destructive waves
- lower in height
- have longer wavelength
- low frequency ( 6-8 per minute)
- they break by spilling forward
- strong swash travels up the beach due to long wavelength and backwash returns to the sea before the next wave breaks, the next swash movement is uninterrupted therefore retaining its energy
- SWASH ENERGY EXCEEDS BACKWASH
what are the main characteristics of destructive waves that differentiate them from constructive waves
- greater in height
- shorter wavelength
- higher frequency (12-14 per minute)
- break by plunging downwards so there is little transfer of energy to move water up the beech as swash. friction form the beech slows swash therefore it can’t travel far, returning as backwash, swash of next wave is often slowed by backwash of previous
- SWASH ENERGY IS LESS THAN BACKWASH
what causes tides, which is the most significant and why
the gravitational force of the sun and moon causing water to bulge
- the moon as it is closer
how many high and low tides are there in most places a day
2 low tide and 2 high tide a day
what are spring tides and how often do they occur
when the moon, sun and earth are all in a line and therefore the forces are working in alignment. this causes high tides to be higher and low tides to be lower
- twice a month
what are neap tides and how often to they occur
when the moon, sun and earth form a right angle and therefore gravitational forces are not acting together. this causes high tides to be lowest and low tides to be highest
define tidal range
the difference between high and low tide
how do tide vary spatially around the world
- most coastlines are semi diurnal having 2 high tides and 2 low tides a day, but Antarctica only has one of each a day
- different places around the world will have different tidal ranges such as in the UK we have macro tides and in the Mediterranean they have micro tides
- the greatest tidal range is the Bay of Fundy = 16m
what are macro and micro tidal ranges
macro = >4
micro = <2
define lithology and geological structure
- the physical and chemical compositions of the different rock types
- the arrangement of rock including features often caused by deformation
what are the three factors of lithology that effect the coast
rock type, permeability and strata
give an example of igneous rock and state the rate of erosion and why this is
- granite
- very slow erosion
- igneous rocks are crystalline, the interlocking crystals making strong hard erosion resistant rock
- it has few joints so there are limited weaknesses to exploit
give an example of metamorphic rock and state the rate of erosion and why this is
- marble
- slow erosion
- crystalline metamorphic rock are resistant to erosion
- some metamorphic rock have foliation where crystals are all orientated in one direction producing weaknesses
- they are often folded and heavily fractured which are weaknesses
give an example of sedimentary rock and state the rate of erosion and why this is
- chalk, limestone
- moderate / fast erosion
- most sedimentary rock is clastic and erodes faster
- the older the rock, the less likely it is to erode as younger rock is weaker
- rock with bedding planes and fractures are more likely to erode
give an example of unconsolidated material and state the rate of erosion and why this is
- boulder clay
- fast
- sediments are not cemented together so are easily eroded
define permeability, porosity and pervious
- the ability for material to hold water
- the total volume of pore space
- rocks having joints and bedding planes where water can flow
define strata and the most typical rock it can be found in
layer of rock that run parallel to each other and show differences in material deposited on the cliff, the lines of strata may vary in width
- mostly seen in sedimentary such as limestone or sandstone
give an A02 point about geological structure
they are localised and specific to a specific coastline
what are the six geological structures that influence the coast
dips, faults, joints, bedding planes, folds, planforms
what is a dip and what are the four types of dips that can occur
a tectonic feature that refers to the angle at which strata lies
may be horizontally, vertically, dipping toward the sea or dipping inland
how do dips influence the coastline and is this a large scale or small scale
horizontal dips - may be impacted as strata near the sea may be more exposed to wave erosion
seaward dips - prominent to rock falls and mass movement from top of cliffs
landward dips - wave action is more prominent if there is weak geology
- impacts on a micro localised scale
what are faults and how do faults influence the coastline, is this large scale or small scale?
- faults are fractures in the rock formed by tectonic processes
- either side of the fault line rocks are heavily fractured and broken leading them to be exploited by marine erosion processes
- small localised scale
what are joints and how do they influence the coastline, is this large scale or small scale
- they are vertical cracks in the rock and occur in most rock patterns, dividing the strata up with regular shapes
- they are caused by contraction of sediment or earth movement and uplift
- small localised scale
what are bedding planes and how do they influence the coastline, is this large scale or small scale
- horizontal cracks that are naturally broken and caused by gaps in time period of rock formation
- small localised scale
what are folds and how do they influence the coastlines, is this large or small scale
- occurs due to crustal compression and often creates joints. when horizontal strata is squeezed they can be folded into anticlines and synclines
what is the difference between an anticline and syncline
Anticline refers to structures that dip downwards from a median line, forming a hill, while syncline refers to structures that dip upwards from a median line, forming a valley
define planform and are planforms larger or smaller scale
how rocks are structured in relation to each other
large scale, regional or sediment cells
what is a concordant coastline and what do these create
occurs when the folding or arrangement of rock is parallel to the coastline - altering layers of resistant and less resistant rock creating cliffs
what is a discordant coastline and what do these create
occurs when the folding or arrangement of rock are alternating bands of more and less resistant rock creating headlands and bays
what are the three main sources of coastal sediment
terrestrial, offshore and human
what are the six terrestrial sources of coastal sediment
fluvial deposition
weathering
mass movement
marine erosion
aeolian deposition
longshore drift
what is fluvial deposition and weathering as a source of coastal sediment
fluvial deposition - river inputs of sediment, in some places 90% of sediment is inputted through rivers
weathering - this is the origin of sediment
what is mass movement and marine erosion as a source of coastal sediment
mass movement - cliff erosion can be increased by rising sea levels, causing undercut cliffs collapsing directing depositing sediment to sea
marine erosion - wave erosion on cliffs causing direct deposit of sediment
what is aeolian deposition and longshore drift as a source of coastal sediment
aeolian deposition - wind blows sediment from other locations such as sand dunes and other beaches depositing sediment
longshore drift - supply sediment from one coastal area by moving it along the coastline to another coastal area
what is the offshore source of coastal sediment and how it is a source
marine deposition
- constructive waves bring sediment to the shore and deposit it adding to the sediment budget
what are the five geomorphic processes affecting the coast
mass movement, weathering, fluvial processes, aeolian processes and wave processes
define geomorphic and define sub - aerial
geomorphic - processes affecting how landscapes are formed and shaped
sub-aerial - happening in the air and on the surface of earth, not underground
define mass movement
the downslope transport of material under gravity
why does mass movement occur
- the angle of the cliff
- rock type and structural properties
- vegetation cover
- permeability and water content
what are the three mass movement flows
soil creep, solifluctuation, earthflows/mudflows
briefly explain soil creeps
- the slowest form of mass movement
- is almost a continual process
- downhill movement of individual soil particles
- occurs more in temperate climates where there is higher soil moisture
briefly explain solifluction
-the movement averages between 5cm and 1m a year
- occurs mainly in tundra areas where the ground is frozen, the top layer of soil thaws in the summer but the layer below remains frozen. the surface layer becomes saturated and flows over subsoil and rock
briefly explain earthflows/mudflows and specify the difference between a slide and a flow
- occurs due to an increased amount of water which reduces friction causing earth and mud to flow over bed rock
- in a slide the material remains in tact moving in a mass
- in a flow the material becomes jumbled up
what are the three mass movement slides
rock falls, rock slides, slumping
briefly explain a rock fall and what is the difference between that and a block fall
- more likely to occur when strong, jointed, deep rock cliffs are exposed to mechanical weathering such as freeze thaw
- once material has broken away it either bounces or falls vertically to form scree at the foot
- a block fall is where a large block falls away from cliff
briefly explain a rock slide
- rocks that are jointed or have bedding planes that are parallel to slope are more susceptible to land slides
- increase amount of water causes friction causing sliding
- slabs of rock slide over underlying rock
briefly explain slumping and state the difference between slumping and sliding
- slumps occur in saturated conditions and on moderately steep slopes
- they are more common where soften material eg clay lay over more resistant or impermeable rock
- the difference between slumping and sliding is that in slumping there is rotational movement
define weathering
using energy to physically or chemically alter rock. it is the gradual breakdown or rock and is sub-aerial
define the three types of weathering
physical ( may be mechanical) - rock is broken down by force
chemical - rock is decayed through chemical reactions
biological - plants and animals influence the breakdown of rock
what are the three physical weathering processes
freeze thaw
salt crystallisation
wetting and drying
explain briefly each physical weathering process, ranking them from most important influence on coastal landscape to least
salt crystallisation - salt solution from sea seeps into porous rock, water evaporates and salt crystals remain and grow creating stress on rock causing it to disintegrate
freeze thaw - water enters cracks or joints in rock, water freezes and expands putting pressure on joints causing them to widen and break
wetting and drying - high tide soaks rock with sea water, rocks (specifically rich in clay) will expand when wet and contract when dry. this eventually causes rock to fragment and crumble.
how does the three physical weathering processes vary spatially
salt crystallisation - porous, sedimentary rock, greater in hot and humid climates where evaporation is promoted
freeze thaw - areas of higher precipitation and can cause further erosion as fragments of rock break into sea causing marine erosion
wetting and drying - areas of clay and macro tidal ranges
what are the five chemical weathering processes
carbonation, oxidation, solution, hydrolysis, hydration
explain briefly each chemical weathering process
carbonation - rainwater combines with carbon producing weak carbonic acid, it reacts with calcium carbonate which dissolves the rock in sea water
oxidation - the reaction of rock minerals (especially iron) with oxygen in air or water. when minerals oxidise they become less resistant to weathering
solution - when materials dissolve in water
hydrolysis - chemical reaction between rock and water
hydration - minerals in rock absorb water weakening their crystal structure, making rock expand
how does the five chemical weathering vary spatially
carbonation - certain geology such as chalk
oxidation - rock type dependent
solution - rock type dependent
hydrolysis - particularly effects the mineral feldspar in granite producing clay which is more susceptible for further erosion
hydration - need permeable rock
what are the three biological weathering processes
chelation, animals, plants
explain briefly each biological weathering process
chelation - organic acids produced by plant roots and decaying organisms bind to metal ions causing rock to decompose
animals - small animals secrete acids that create small, hollows in the rock, some can burrow into the rock and large land animals burrow into cliff face = exposing material making weathering easier
plants - plant and tree roots force way into joints, breaking rocks down
how do the three biological weathering processes vary temporally or A02 in general
chelation - areas of low temp decomposition is slow
animals - a slow, long term process
plants - some plants and shrubs bind soil on top of cliff helping security
how do waves cause costal erosion that inputs sediment into the coasts (what are the four types of wave erosion)
attrition - rock particles collide wearing coastal rock away
abrasion - rocks rub and hit against a cliff
hydraulic action - waves break against cliff, moisture is trapped in cliffs, wave recedes and pressure releases and water expands so cracks widen
solution - dissolving coastal rock
how do waves transport sediment (what are the five types of wave transportation)
solution - minerals are disolved
suspension - smaller sediments are transported and larger particles when increased velocity of water
saltation - irregular movement of larger particles
traction - larger rocks rolling along sea bed
longshore drift - waves approach coast at an angle due to prevailing wind, waves break and swash carries sediment across the beach under influence of gravity
why do waves deposit sediment and when does deposition occur
when the energy of the wave isn’t strong enough to carry the weight of the sediment
- when the rate of sediment accumulation exceeds rate of removal
- waves slow down after breaking
- at the top of swash, water stops moving for a moment
- during backwash water percolates down into beech matter
- in low energy environments such as estuaries
define settling velocity in relation to deposition
the velocity at which material is deposited at - larger and heavier particles require more energy to transport so as velocity decreases the largest particles are deposited first
define fluvial
relating to rivers
how does fluvial erosion input sediment into the coasts
- fluvial erosion in the upper catchment
- weathering and mass movement from upstream
- similar erosion processes to waves
how do fluvial processes transport sediment
solution - minerals are disolved
suspension - smaller sediments are transported and larger particles when increased velocity of water
saltation - irregular movement of larger particles
traction - larger rocks rolling along sea bed
how do fluvial processes deposit sediment
rivers enter mouth where there is a reduction in velocity due to flowing water entering static water
- largest sediments are deposited first and smaller sediment taken further out to sea
- tides and currents may resist forward flow
define flocculation and why this occurs in fluvial processes
when fine, light materials clump together due to the electrical charges of clay particles. this occurs in river estuaries due to the meeting of sea and fresh water. brackish water activates chemical charge causing clay particles to clump together and sink as they have a larger mass
how does aeolian erosion input sediment into the coasts
- deflation enables wind to pick up sand particles and move them
- at 40km/hour sand grains are moved by surface creep and saltation
- erosive force increases with wind velocity
- dry sand is easier to pick up than wet sand as moisture increases cohesion between particles
- attrition on land is effective as particles tend to be carried further on land
how does aeolian transport sediment in and around the coast
- exception of solution, moving air can transport material the same way as waves
- once particles are in the air they can be carried in velocities as low as 20km/hour
- larger sediment are too heavy to be saltated and move by surface creep
- only small sediment can be held by suspension
how does aeolian deposit sediment in and around the coast
- material carried by wind will be deposited when wind speed falls usually as a result of surface friction
- this occurs mostly inland in coastal areas where friction from vegetation and irregular surfaces is greater than out at sea
what are the three types of equilibrium
steady state, meta stable and dynamic equilibrium
define steady state equilibrium
when a system is essentially consistent in its relationship of inputs and outputs, there may be seasonal variation but on average it is stable
define meta stable equilibrium
where a system changes dramatically between one state and another, after the influence of a trigger and it then has to adjust to that new state
define dynamic equilibrium
involves change in a system but in a more gradual way than the meta stable change
give examples of erosional landforms that form due to flows of energy and material
- cliffs
- shore platforms
- headlands
- bays
- geos
- blowholes
- caves
-arches - stacks
- stumps
how can you describe what a cliff looks like
using a cliff profile
what is the main physical factors that affects a cliff profile - this is from KQ1
- geology - the main type
lithology - this is because it determines the speed of erosion of the strata
geological structure - joints, bedding planes, dips, faults, folds are more likely to speed up the process of erosion therefore exploiting land creating cliffs
what is the main geomorphic process that affects a cliff profile - this is KQ2
- mass movement and weathering
- wave processes cause erosion which is the most important
- aeolian processes
what are the main erosional features found in cliffs
- caves, wave cut notches, blow holes, geos, wave cut platforms
describe how a shore cut platform is formed
waves break against cliff = marine erosion = bottom of cliff receives more energy than strata = faster erosion = wave cut notch = advances deeper into cliff = strata becomes unstable = potential energy stored in cliff and gravity = rock falls = debris at bottom of cliff = slows erosional processes. process is repeated over time creating a platform, over time the platform will be so wide that even at high tide, waves will break before reaching cliff, limiting erosion and further retreat.
what are the most important factors influencing the formation of shore cut platforms
marine erosion at both low and high tide, weathering process that take place of platform: specifically solution, freeze thaw and salt crystallisation, biological weathering with algae
explain the formation of headlands and bays
- differential erosion (Erosion that occurs at irregular or varying rates) results in the formation of headlands and bays on discordant coastlines and bays or coves on concordant coastlines
- discordant coastlines the layers of rock run parallel to the coastline where bands of less resistant rock erodes faster and therefore leaving headlands that are more resistant sticking out more
- bays are curved shaped due to different erosion speeds
- coves are more sheltered and are protected by more resistant geology in front of them.
- wave refraction also plays an important role
define wave refraction
refers to the way a wave bends when the seafloor is uneven.
how does wave refraction play a role in the formation of headlands and bays
- important as it determines where wave energy is concentrated and therefore where erosion takes place
- on a coastline the seabed around the resistant headlands will be shallower
- the shallowness means the wave base meets the seafloor increasing wave frequency and wave height as the seabed increases friction
- the waves follow the shape of the seafloor and so refract around the headland where it is more shallow
- meaning that wave energy is more concentrated around the resistant headland and less near the bays, causing more deposition in the bays
what are geos and how are they formed
- A long, narrow, steep-sided slit formed by erosion in coastal cliffs
- A geo is formed by the action of waves eroding the lower portion of a cliff. A depression or sea cave may form. The cliff face above the cave can erode and collapse over a period of time, creating a geo.
what are blowholes and how are they formed
- A crack or fissure in coastal rock through which air and spray is expelled when waves break on the shore
- When part of the tunnel-like cave collapses along a master joint it may form a vertical shaft that reaches the cliff top, In storm conditions large waves may force spray out of the blowhole as plumes of white, aerated water.
explain the formation of caves, arches, stacks and stumps
- Caves occur when waves force their way into cracks in the cliff face. The water contains sand and other materials that grind away at the rock until the cracks become a cave. Hydraulic action is the predominant process
- If the cave is formed in a headland, it may eventually break through to the other side forming an arch
- The arch will gradually become bigger until it can no longer support the top of the arch. When the arch collapses, it leaves the headland on one side and a stack (a tall column of rock) on the other
–The stack will be attacked at the base in the same way that a wave-cut notch is formed. This weakens the structure and it will eventually collapse to form a stump.
name the six main depositional landforms
- spits
- tombolo’s
- salt marshes
- onshore sandbars
- offshore sandbars
- beaches
what are the main two categories of depositional landforms
swash aligned and drift aligned
what are swash aligned depositional landforms and give two examples
- formed when waves break parallel to the coast
- swash and backwash move material up and down the beach
- fairly closed sediment systems
- beaches and bars
what are drift aligned depositional landforms and give three examples
- formed when waves reach the coast at an angle but the backwash runs perpendicular to the beaches
- create longshore drift
- they are more open systems
- produces partially attached features
- spits, Tombolo and beaches with LSD
what are the two types of sediment on the beach
sand beaches and shingle beaches
what is the role sediment on sand beaches
- produces beaches with a gentle gradient (under5 degrees) due to small particle size which becomes compacted when wet allowing little percolation
- means less water drains through beach during swash causing more backwash = more energy to transport sediment in backwash = lower gradient
- development of micro features
what is the role of sediment on shingle beaches
- a mix of small to medium size cobbles and pebbles produce steeper beaches as swash is stronger than backwash
- there is a net movement of shingle onshore
- shingle may make up the upper part of beach where rapid percolation occurs due to larger spaces = little backwash so material is left at the top of the beach = steep profile
name a few micro features that can be found on the beach
- berms
- beach cusps
- ripples
- storm beach
what are beach cusps and how do they form
small semi circular depressions
- they are temporary features formed by a collection of waves reaching the same point and where the swash and backwash have similar strength
what are berms and how do they form
smaller ridges that develop at the position of the mean tidal high mark resulting from deposition at the top of swash
what are ripples and how do they form
may develop in the sand due to orbital movement of water in waves
what are storm beaches
where storm waves hurl pebbles and cobbles to the back of the beach forming a storm beach or ridge, this increases the gradient of the beach
what are spits
- drift aligned depositional landforms
- resemble a beach that is joined to the mainland at only one end
define the proximal end
the end of the spit that is attached to the mainland
define the distal end
the end of the spit that projects out to the coast
what are the four conditions needed for a spit to form
- a good supply of sediment
- longshore drift
- an abrupt change in the shape of the coastline such as an estuary or bay
- limited tidal range
explain the formation of spits
- when longshore drift occurs moving material to the end of the beach
- when there is an abrupt change in the shape of land, the longshore drift continues in its original direction rather than following shape of land, building beach into open water
- more sediment is deposited over time stabilising the spit
- when in deep water near distil end of spit, wave energy is dispersed through deeper water = reduce in transportation and deposition
- waves refract around the distilled end, taking sediment with them, can cause a recurved spit
- if spits are formed over estuary then river energy may limit spits growth
what are tombolos
a bar or spit connecting to an island
what is the first theory of how tomobolos are formed
- kinetic energy in waves creates conditions suitable for transportation and deposition of material through longshore drift.
- prevailing winds at an oblique angle means there is low energy to encourage deposition and therefore lots of sediment
- sediment is transported along the beach in the direction of prevailing wind and waves
- a spit starts to form growing seawards until they reach and adjoin an offshore island
- wave refraction around an off-shore island causing a wave energy shadow (where increased deposition occurs on the lee side of an island as it is sheltered from waves and wind, therefore less energy)
what is the other theory of how tombolos are formed - includes details of Chesil beach
- if longshore drift was responsible for the growth of Chesil beach, it would be expected that the sediment further east would be smaller
- it is more likely that onshore migration of shingle after the end of ice age originally produced uniform distribution of sediment.
what is an onshore bar and what other landforms do they create
can develop if a spit continues to grow across an indentation to the land and then re-joins on the other side.
- create lagoons or salt marshes on the sheltered side
what is a salt marsh
features of a low energy environment such as estuaries and on the landward side of a spit.
- they are vegetated areas of deposited silts and clays
where to salt marshes form on a coastal zone
the landward side of a spit
what conditions are needed for salt marshes to form
- low energy environment so deposition can occur
- tiny clay particles for flocculation
- greater density of vegetation cover helps trap and stabilise sediment
what are the plants called that can survive in salt marshes
Halophyte plants
