EQ2 Flashcards
what does sediment move along in
sediment cells
how many major sediment cells are in england and wales
11
TRUE or FALSE can major sediment cells be divided further
TRUE
Each major cell can be divided into a number of sub cells
what are each sediment cell operating within
Each cell operates between physical barriers that prevent sediment from moving any further along the coast
what is interlinked within sub cells
erosional processes
transport processes
deposition
can some coastal features operate as sinks, source and transfer zones
NO
ONLY some coastal features operate as SINKS AND SOURCES
- depends on whether the dominant processes are erosion or deposition at a given time
what is a source
give examples
a place where sediment is generated
such as cliffs, sand dunes or offshore bars and even river systems
what is a transfer zone
places where sediment is moving along the shore
via longshore drift and offshore current
what is a sink
locations where the dominant process is deposition
-depositional landforms are created such as spits and offshore bars
define sediment budget
The amount of sediment available within a sediment cell
what state does a system act in under natural conditions
DYNAMIC EQUILIBRIUM
TRUE or FALSE can dynamic equilibrium be disrupted
TRUE
dynamic equilibrium can be disrupted by storms leading to increased erosion
what do negative feedback mechanisms do to the dynamic equilibrium
Negative feedback mechanisms help maintain the balance by pushing the system back towards equilibrium.
what do positive feedback mechanisms do to dynamic equilibrium
Positive feedback mechanism is where one change has led to another change which leads to disequilibrium in the coastal system.
does positive feedback lead to equilibrium or disequilibrium
DISEQUILIBRIUM
does negative feedback lead to equilibrium or disequilibrium
EQUILIBRIUM
what are 2 factors that impact the state of dynamic equilibrium
Coastal management
Global warming
how does coastal management impact the state of dynamic equilibrium
can decrease erosion leading to less sediment input
how does global warming impact the state of dynamic equilibrium
Increased storms due to global warming could lead to long term erosion of sand dunes with no chance to recover between storm events.
Rising sea level could increase erosion of spits and estuaries, removing sediment faster than it can be replaced.
what do waves directly influence which in return shapes the….?
erosion, transportation and deposition,
so they shape the coastline.
how are waves caused
by friction between wind and water
what is wave size dependant on
-The strength of the wind
-The duration the wind blows for
-Wave fetch - the uninterrupted distance across water over which the wind blows
-Water depth - see waves as they approach a shoreline
how are waves affected when approaching the shoreline
the water shallows and the shape of the waves changes significantly.
what happens when the internal orbital motion of water touches the sea bed
friction occurs and this slows down the wave
what happens to the wave length and wave height as it approaches the shore
wavelength = decreases
wave height = increases
makes waves look like they bunch together
why do waves break in shallow water
because the crest of the wave begins to move forward much faster than the wave trough due to friction with the sea bed.
what causes a wave to break
the wave crest outruns the trough and the wave topples forward = breaks.
two types of waves
constructive
destructive
what is the wave height, energy and frequency of CONSTRUCTIVE waves
LOW
LOW
LOW
what is the wave height, energy and frequency of DESTRUCTIVE waves
HIGH
HIGH
HIGH
do destructive waves have a greater swash or backwash
BACKWASH > swash
beach loss
do constructive waves have a greater swash or backwash
SWASH > backwash
beach gain
what is beach morphology
the shape of the beach, including its width and slope and features. It also includes the type of sediment found at different beaches location
what creates different beach profiles
the seasonal changes in wave type
what wave type create winter beach profiles
destructive waves – sediment dragged offshore
what wave type create summer beach profiles
constructive waves - sediment dragged onshore
what factors create winter beach profiles
-Berms are eroded by plunging waves
-Strong backwash transports sediment offshore(depositing is at offshore bars)
-Sometimes the backwash exerts a current known as a rip/undertow - dragging sediment back as the next wave arrives over the top
what factors create a summer beach profile
-Constructive waves are less frequent wave energy dissipates and deposits over a wide area (weakening backswash)
-The swash of constructive wave deposits larger material at the top of the beach creates a berm
-As a berm builds up the backswash becomes weaker. It only has enough energy to move smaller material so the beach materials are smaller the closer you are to the shoreline
what are examples of changes in beach profiles
-sediment supply is reduced from rivers due to dams
-coastal management has effect on processes further along the coast
-global warming makes the UK stormier on average, more destructive waves, making winter beach profiles more common
what are the 4 ways sediment is transported
solution
saltation
suspension
traction
what is longshore drift
the movement of materials along a coast by wave action which approach at an angle to the shore but recede directly away from it
what can affect longshore drift
tides and currents
what are tides
changes in the level of seas and oceans – caused by the gravitational pull of the moon
what is tidal range
The relative difference in height between the high and low tides
what does a high tidal range mean
powerful tidal currents, as tides rise and fall
what are examples of depositional landforms
Spits
Beaches
Offshore bars
Barrier beaches
Tombolos
Cuspate forelands
what is a spit
A spit is a long narrow feature, made of sand or shingle, which extends from the land into the sea
how does longshore drift influence the spits formation
Sand or shingle is moved along the coast by longshore drift, but if the coastline suddenly changes direction (e.g because of a river estuary) sediment will begin to build up across the estuary mouth and the spit will start to form
what causes a recurved spit
end of the spit will begin to curve round as wave refraction carries material round into the more sheltered water behind the spit
where are beaches commonly found
Beaches are commonly found in bays.
what sort of environment does wave refraction create in beaches
Wave refraction creates a low-energy environment, which then leads to deposition
what are the two different aligned beaches
drift aligned beach
swash-aligned beach
what are offshore bars
are submerged ridges of sand - created by waves offshore from the coast
how do destructive waves create offshore bars
Destructive waves erode sand from the beach with their strong backwash and deposit it offshore as bars
what is a barrier beach
Where a beach or spit extends across a bay to join two headlands, it forms a barrier beach
is it true barrier beaches can form lagoons?
YES
Barrier beaches and bars can also trap water behind them to form lagoons.
what is a separated barrier beach called
barrier island
what is a tombolo
a beach that has formed between a small island and the mainland
how does deposition occur to form the tombolo
Deposition occurs where waves lose their energy and the tombolo begins to build up
what is a cuspate foreland
triangular-shaped headland that extends out from the main coastline.
how does a cuspate foreland form
a coast is exposed to longshore drift from opposite directions. Sediment is deposited at the point where the two meet, which forms a natural triangular shape as it builds up.
how does a cuspate foreland stabilise itself
vegetation begins to grow on the deposited sediment, it helps to stabilise the landform and protect it from storms that could erode it.
how does vegetation stabilise depositional landscapes
Depositional landforms are made of unconsolidated sediment and so are vulnerable to change.
Plant succession – salt marshes and sand dunes – bind the loose sediment together and encourage further deposition of sediment.
how do depositional landforms become vunerable
Depositional landforms are vulnerable when their vegetation is damaged through overgrazing or trampling from tourism and leisure activities.
what are the 4 coastal erosional processes
hydraulic action
abrasion
attrition
solution
explain hydraulic actions process
air trapped in cracks and fissures is compressed by the waves force crashing against cliff
The pressure forces cracks open, then more air can then be trapped and greater force is experienced during compression cycles
This process dislodges rock on the cliff face
hydraulic actions influence on lithology
heavily jointed sedimentary rocks are vulnerable
hydraulic action on the cooling cracks of igneous rock may be the only working erosive process
explain abrasion as a process
sediment is picked up by waves and is thrown against a cliff
it acts as a chisel gradually wearing down the cliff face by removing small rock particles
abrasions influence on lithology
for abrasion to be effective loose sediment has to be available.
softer sedimentary rocks are more vulnerable than igneous rocks
explain attrition as a process
the process acts on already eroded sediment
as sediment is moved by waves collision occurs chipping away fragments of sediment
Overtime sediment becomes smaller and rounder
attritions influence on lithology
softer rocks are rapidly reduced in size by attrition
explain corrosion as a process
carbonate rocks are vulnerable to solution by rainwater, spray from seawater
corrosions influence of lithology
mainly affects limestone, which is vulnerable to solution by weak acids
what influences the rate and type of erosion
the size and type of waves that reach the coastline
when does most erosion occur
during winter storms
small scale lithology are eroded more..?.. which results in the formation of..?…
quickly
different landforms
when destructive waves are at their largest and most powerful what erosional processes are going to become more powerful
abrasion and hydraulic action
TRUE or FALSE bands of more resistant rock erode more quickly
FALSE
they erode slowly
what is differential erosion
the selective erosion of areas of weakness as opposed to more resistant areas
what does differential erosion give you
caves, arches, stacks and stumps
what do areas of resistant rock generally form and what do areas of weaker rock form
Resistant rock: headlands and cliffs
Weaker rock: Bays and inlets
how does rock type influence erosion
erosion is faster when the rocks on the coastline are weaker
what are the 9 landforms of coastal erosion
headlands
bays
wave cut platform
caves
arches
stack
stump
blowhole
cliffs
when waves approach a headland does the water depth increase or decrease
DECREASES
when waves approach a bay does the water depth increase or decrease
INCREASE
when waves approach a headland the waves get steeper and the velocity..?.. as they become closer together however the erosional power…?…
velocity REDUCES
erosional power INCREASES
when waves enter a bay they don’t …?… the velocity and the waves are low and less steep which allows …?… to take place
velocity isnt lost as rapidly
deposition rather than erosion takes place
how are wave cut notches formed
-waves break against the foot of the cliff
-erosion is concentrated close to the high tide line
-creating wave cut notch which begins to undercut the cliff
what occurs when the wave cut notch gets bigger
the rock above becomes unstable and eventually the upper part of the cliff collapses
what causes the wave cut notch to migrate inland
erosional processes repeating causing the cliff to retreat
what reduces the rate of erosion on the wave cut platform
the platforms have grown due to continuous erosion by their width means the wave breaks earlier and its energy is dissipated before it reaches the cliff
when joints and faults are eroded this can create
A. spit B. cave C. tombolo
B. CAVE
when caves are created the overlying rock may collapse forming a
BLOWHOLE
when caves erode through a headland what forms
ARCH
what causes the arch to enlarge
erosion and weathering
when the top of the arch becomes unstable what forms
A STACK
when a stack is eroded by the sea what does it collapse into
a STUMP
how do cliffs maintain their steep profile
constant wave action and erosion at the cliffs base ensure it remains steep as it retreats inland
what are sub aerial processes
Weathering
Mass movement
what are the 3 types of weathering
mechanical
biological
chemical
define weathering
is the gradual breakdown of rock, in situ (in position) at or close to the ground surface
define mass movement
is the movement of weathered material down slope, as a result of gravity
what 2 factors have influence over weathering experienced
precipitation
temperature
where does mechanical weathering dominate
cold climates
where does chemical weathering dominate
hot wet conditions
what also has major influence on the type of weathering that takes place
the lithology of coastal rocks
as some rocks are more prone to certain types of weathering than others
define mechanical weathering
breaks down rock due to the exertion of a physical force
what are the 3 mechanical weathering processes
freeze thaw
salt crystallisation
wetting and drying
explain freeze thaw as a process
water expands in volume when freezing, exerting a force within cracks and fissures, repeated cycles forces rocks to open and loosen rocks
what rocks are vulnerable to freeze thaw weathering
Any rocks with cracks or fissures, especially rocks away from salt spray, as salt spray reduces the effect of freeze thaw
explain salt crystallisation as a process
The growth of salt crystals in cracks and pore spaces, can exert a breaking force
what rocks are vulnerable to salt crystallisation
Porous, fractured rocks e.g sandstone
Its effect is greater in not dry climates where evaporation occurs
explain wetting and drying as a process
Frequent cycles of wetting and drying of coastal rocks
what rocks are vulnerable to wetting and drying
Rocks rich in clay (shale) expands when wet and contract as they dry
define biological weathering
often speeds up mechanical or chemical weathering through the action of plants, bacteria or animals
what are the 2 biological weathering processes
plant roots
rock boring
explain plant roots as a process
Thin plant roots grow in cracks in the cliff face, the cracks then widen as roots become thicker, which breaks up the rock
what rocks are vulnerable to rock boring
Sedimentary rocks especially carbonate rocks (limestone) located in intertidal zones
what rocks are vulnerable to plant roots
Vegetated cliff tops, contributing to rock fall
explain rock boring as a process
Many species of clams and molluscs bore into rock and may also secrete chemicals that dissolve rocks
define chemical weathering
involves a chemical reaction and the generation of new chemical compounds
what are the 3 chemical weathering processes
hydrolysis
oxidation
carbonation
explain carbonation as a chemical weathering process
Where slow dissolution of limestone due to rainfall (PH 5.6, weak carbonic acid) producing calcium bicarbonate in solution
examples of vulnerable rocks to carbonation
Limestone and other carbonate rocks
explain hydrolysis as a chemical weathering process
The breakdown of minerals to form new clay minerals due to the effect of water and dissolved CO2
examples of vulnerable rocks to hydrolysis
Igneous and metamorphic rocks containing silicate minerals
explain oxidation as a chemical weathering process
the addition of oxygen to minerals, especially iron compounds which produces iron oxides and increases volume contributing to mechanical breakdown
example of vulnerable rocks to oxidation
Sandstones, siltstones and shales often contain iron compounds that can be oxidised
how does weathering increase mass movement
Weathering weakens rock, making them more vulnerable to erosion or mass movement processes
what is the main sub aerial process that causes cliff collapse
On some coastlines the dominant cause of cliff collapse is mass movement
how can mass movement be classified
how rapid the movement is
The type of material
the resultant movement is dependant on these 4 factors
The angle of the slope/cliff
The rock type and its structure
The vegetation cover
How wet the ground is
TRUE OR FALSE soil creep is the fastest form of mass movement
FALSE
its the slowest
what are the 3 mass movement FLOWS
solifluction
soil creep
earth/mud flows
is soil creep a continuous process
almost continuous process
It’s a very slow downhill movement of individual soil particles
where does solifluction occur mainly
tundra areas where the ground is frozen
explain solifluction as a process
When the top layer of soil thaws for summer – but the layer below is frozen (permafrost) – the surface layer becomes saturated and flows over the frozen subsoil and rock
an increase in …?… reduces friction causing …?… to flow over underlying bedrock
the amount of water due to increased precipitation
earth and mud
what is the difference between a mass movement SLIDE and a mass movement FLOW
In a slide the material remains intact (it moves ‘en masse’).
In a flow the material becomes jumbled up.
what are the 3 mass movement SLIDES
rock fall
rock slides
slumping
when are rock falls most likely to occur
Rock falls are most likely to occur when strong, jointed and steep rock faces/cliffs are exposed to mechanical weathering
Rocks falls occur on slopes that are..
A. slopes that are10 degrees and below
B. slopes that are 20-30 degrees
C. slopes over 40 degrees
C. slopes over 40 degrees
what happens when the rock falls in the mass movement slide rock fall
falls vertically causing scree/talus, at the foot of the slope/cliff
what rocks are vulnerable to rock slides
Rocks that are jointed, or have bedding planes roughly parallel to the slope or cliff surface
an increased amount of ..?.. can reduce friction causing …?…
And increase in the amount of WATER can reduce friction - causing SLIDING
what conditions does slumping occur
SATURATED CONDITIONS
what type of slopes does slumping occur
Slumps occur on moderate to steep slopes
what type of material leads to slumping
Common where softer materials (clay or sands) overlie more – resistant or impermeable rock, such as limestone or granite
what does slumping lead to
Slumping causes rotational scars
Repeated slumping creates a terraced cliff profile
what are the 3 landforms created by mass movement
Rotational scars
talus/scree slope
Terraced cliff profile
