Coastal systems and landscapes Flashcards
(125 cards)
1
Q
what type of system are coasts ?
A
open systems as it can receive inputs and transfer outputs away
- these systems may be terrestrial , atmospheric or oceanic and include rock, water and carbon cycles
note ; you may need to think of coasts as closed systems at points eg. coastal management planning
2
Q
what is a sediment cell ?
A
coasts are split up into sections ( sediment cells ) which are boarded by prominent headlands
- within the cells the movement of sediment is contained and flows of sediment act in dynamic equilibrium
3
Q
what is dynamic equilibrium ?
A
the balance in a natural system even though there is constant change, the system counteracts any changes imposed on it
- can be affected in the long term by human interactions or in the short term by natural variations
4
Q
what are the key inputs in a coastal system ?
A
marine: waves, tides, salt spray
atmosphere: sun, air pressure, windspeed and direction
humans: pollution, recreation, settlement, defences
5
Q
what are the key ouputs in a coastal system ?
A
ocean currents
riptides
sediment transfer
evaporation
6
Q
what are the stores and sinks in coastal system ?
A
beaches, sand dunes, spits, bars, tombolo, headlands, bays, nearshore sediment, cliffs, wave cut notches, wave cut platforms, caves, arches, stacks , stumps, slat marshes, tidal flats , offshore bands and bars
7
Q
what are the transfers and flows in a coastal system ?
A
windblown sand
mass movement processes
longshore drift
weathering
Erosion: hydrolytic action, corrosion, attrition, abrasion
Transportation: bedload, suspension, solution, traction
Deposition: gravity settling, flocculation
8
Q
what is the energy in a coastal system ?
A
wind
gravitational
flowing water
9
Q
what is a negative feedback loop ?
A
a mechanism that balances changes by lessening it in order to bring back equilibrium
10
Q
what is an example of a negative feedback loop ?
A
- destructive waves loos energy and deposit sediment as an offshore bar
- the bar dissapates wave energy protecting the beach behind it
- overtime the bar is eroded not the beach
- once the bar has gone normal conditions follow and dynamic equilibrium returns
11
Q
what is a positive feedback loop ?
A
a mechanism that enhances a change making the system more unstable and taking it away from dynamic equalibruim
12
Q
what is an example of a positive feedback loop ?
A
- people walking over sand dune destroys the vegetation and causes erosion
- without the roots from the vegetation the rate of erosion increases
- eventually the sand dunes will be completely eroded and leaves the beach open to erosion taking it away from its original state
13
Q
describe rivers as a sediment source
A
most of the sediment in the coastal zone is a result of input from rivers, especially after rainfall (more erosion of the bed)
- sediment may be deposited in estuaries which are salts areas where the river meets the sea
14
Q
describe cliff erosion as a sediment source
A
areas with unconsolidated cliffs are eroded easily, as coastlines retreat sediment is inputted into the sea
the most amount of erosion occurs in winter months due to storms
15
Q
describe the wind as a sediment source
A
the wind is a coastal energy source and can cause sand to be blown up or along a beach
sediment transport by winds may occur where there are sand dunes or desert environments
16
Q
describe glaciers as a sediment source
A
in some coastal systems such as Antarctica or Greenland, glaciers flow directly into the ocean depositing sediment that was stored in the ice
- this occurs when glaciers calve (ice breaks off)
17
Q
describe offshore stores as a sediment source
A
when waves and tides erode offshore sediment stores like offshore bars, sediment is transported onto the beach
sediment is also transferred from storm surges or tsunamis
18
Q
describe longshore drift as a sediment source
A
sediment is moved along the beach due to prevailing winds which change the direction of the waves, the swash approaches the beach at an angle due to the winds transferring sediment along the beach and then the backwash pulls sediment directly backdown the beach in a zig zag. this moves sediment from one side of the beach to another
19
Q
what are sediment budgets ?
A
similar to a carbon budget it measures the gains and losses of sediment within a sediment cell. in theory it will be in a dynamic equilibrium so inputs and outputs would be equal but due to human actions and natural variation this can shift
20
Q
what is the littoral zone ?
A
the area of land between the cliffs or dunes on the coast and the offshore area that is beyond the influence of the waves
21
Q
what can affect the littoral zone ?
A
short term factors - tides and storm surges
long term factors - changes in sea level and human intervention
22
Q
what is the main source of energy for coasts ?
A
waves which are formed offshore, commonly generated by wind but can be made by tectonic activity or underwater landslides ( tsunami waves )
23
Q
how are waves formed ?
A
- winds move across the surface of the water creating a frictional drag, which creates small ripples or waves
- this leads to a circular orbital motion of water particles
- as it gets shallower the orbit of partials gets more elliptical
- wave height increases and the water from the back surges forward and collapses
24
Q
what factors effect wave energy ?
A
strength of the wind : wind is are that moves from an area of high pressure to low pressure , the greater the pressure difference ( caused by the suns heating ) the stronger winds the stronger waves
duration of the wind : if the wind is active for longer periods of time then the energy of the waves will build up and increase
size of the fetch : the fetch is the distance over which the wind blows, the larger it is the more powerful the wave
25
what are constructive waves ?
deposit material to create depositional landforms and steeper beaches
26
what are destructive waves ?
remove depositional landforms through erosion and decrease the size of the beach and make them more sloped
27
how are constructive waves formed ?
formed by weather systems that operate in the open ocean , the swash is stronger than the backwash and they form the beach
28
how are destructive waves formed ?
localised storm events with stronger winds operating closer to the coast
the swash is weaker than the backwash and material is eroded
29
compare the wavelength and frequency of constructive and destructive waves ?
constructive waves have a long wavelength and a smaller frequency ( 6-9 per min )
destructive waves have a short wavelength and a higher frequency ( 11-16 per min )
30
what are the characteristics of both types of wave ?
constructive waves are low and surge up the beach
destructive waves are high and plunge onto the beach
31
how might the types of waves vary ?
- in summer constructive waves are more common but in winter destructive waves are
- constructive waves may become destructive if there is a storm
- climate change may increase the storm frequency within the uk
- coastal management may affect the types of waves
32
how is there negative feedback with beaches and waves ?
1. the presence of constructive waves causes deposition which creates a gently steeper beach
2. steeper beaches mean that there will be more destructive waves
3. destructive waves erode the beach reducing the profile (sloped)
4. leading to more constructive waves again
33
which beaches do the different wave types occur ?
constructive waves occur on a gently sloped beaches
destructive waves occur on steeply sloped beaches
34
what are tides ?
caused by the gravitational pull of the sun or moon which changes the water levels of the seas or oceans. the difference in height between the tides is know as tidal range and tends to be largest in channels like estuaries
35
what are spring tides ?
when the highest high tide and the lowest low tide occur due to the sun and the moon are aligned so both there gravitational forces combine, this creates the largest possible tidal range
36
what are neap tides ?
the lowest high tide and highest low tide occur when the sun and the moon are perpendicular to each other, so the gravitational forces act against each other. this creates the smallest possible tidal range
37
what are rip currents ?
powerful underwater currents occurring in areas close to the shoreline on some beaches when plunging waves cause a build-up of water at the top of the beach, the backwash is pushed under the breaking waves and flows away from the beach
- are an energy source and lead to outputs of sediment
38
what are riptides ?
occur when the ocean tide pulls water through a small area such as a bay or lagoon
39
what are high energy coastlines ?
- more powerful waves due to a large fetch
- rocky headlands and landforms
- destructive waves
- rate of erosion exceeds rate of deposition
40
what are low energy coastlines ?
- less powerful waves occur in sheltered areas
- constructive waves
- rates of deposition exceed rate of erosion = deposition landforms
41
what is wave refraction ?
the process by which waves turn and lose energy around a headland on uneven coastlines
- wave energy is focused on headlands and dissipates in the bays creating low energy features eg. beaches
42
how is there a negative feedback loop associated with wave refraction ?
1. a headland forms as waves don't erode the stronger rock
2. the headland then faces more erosion and the bays more deposition
3. the headland eventually wares away which once again increases erosion in the bays
43
what is erosion ?
removal of sediment from a coastline by different types of erosion
44
what is corrasion ?
sand and pebbles are picked up by the sea and hurled against cliffs at high tide causing the cliffs to be eroded, the size weight and quantity of the rocks picked up effects the power of erosion
45
what is abrasion ?
sediment is moved along the shoreline causing it to be worn down ( sandpaper effect )
46
what is attrition ?
rocks and pebbles hit against each other wearing each other down so they become smaller ( doesn't have a big effect on the coastline )
47
what is hydraulic action ?
as waves crash into a cliff face air is forced into cracks in the rock, the high pressure caused the cracks to force apart and widen when the wave retreats the air expands
48
what is cavitation ?
when bubbles in the water implode under high pressure creating tiny jets that erode the rock
49
what is corrosion ?
mildly acidic seawater can cause alkaline rock to be eroded, similar to carbonation weathering
50
what is wave quarrying ?
the breaking waves can exert a pressure on the cliff face, similar to hydraulic action
51
what factors effect erosion ?
waves
beaches - can absorb wave energy and reduce the effects of erosion on a cliff
subaerial processes - weathering and mass movement processes weaken cliffs, rock fragments as a result of this cause increases abrasion
rock type - sedimentary is mor vulnerable as partials can break off compared to igneous and metamorphic which are made of interlocking crystals
rock faults and characteristics
52
how are the different types of rocks effected by erosion ?
igneous - very slowly eroded , interlocking crystals are resistant eg, granite
metamorphic - less slowly, crystal all orientated in the same direction to resist erosion eg, slate
sedimentary - very fast eroded, lots of faults making them weak and vulnerable to erosion eg, limestone
53
what is traction ?
large heavy sediment rolls along the sea bed pushed by currents
54
what is saltation ?
smaller sediment bounced along the sea bed, pushed by currents
55
what is suspension ?
small sediment is carried with the flow of water
56
what is solution ?
dissolved material is carried within the water, potentially in chemical form
57
explain longshore drift ?
1. waves hit the beach at an angle determined by the prevailing wind
2. waves push sediment in this direction up the beach in the swash
3. due to gravity the wave carries sediment back down the beach in the backwash
4. this moves sediment along the beach over time
58
what is deposition ?
occurs when sediment becomes too heavy for the water to carry or if the wave loses energy
59
what are the two types of deposition ?
gravity settling - water velocity decreases so sediment begins to be deposited
flocculation - clay particles clump together due to chemical attraction and then sink due to density (process in salt and tidal marshes )
60
how does deposition differ in high energy coastlines and low energy coastlines ?
high energy coastlines - continue to carry the smaller sediment so larger rocks and shingle are deposited
low energy coastlines - have smaller sediment which is deposited where there is lower water velocity
61
what is weathering ?
the breakdown of rocks over time ( mechanical, biological, chemical ) , leading to the transfer of material into the littoral zone where is becomes an input to sediment cells
62
what is a positive feedback loop in weathering ?
1. if the rate of removal of weathers rock form the base of the cliff is higher than the rate of weathering
2. promotes further weathering as area of exposed rock is increases
3. more erosion
4. more rocks in water = more erosion processes like abrasion
63
what is a negative feedback loop in weathering ?
1. if the removal of rock from the base of the cliff is slower than the rate of weathering
2. build up of debris at the base of the cliff reducing the exposed area
3. reduced erosion
64
what is mechanical weathering ?
the breakdown of rocks due to exertion of physical forces without any chemical changes taking place eg. freeze thaw, salt crystallisation, wetting and drying
65
what is freeze thraw weathering ?
water enters rocks in cracks and freezes, it expands in volume and this puts pressure on the rock and cracks grow
66
what is salt crystallisation weathering ?
as seawater evaporates salt is left behind, this puts pressure on the rock causing cracks , can also corrode some rocks
67
what is wetting and drying weathering ?
rocks like clay expand when they get wet and then contract when they are dry this causes cracks and frequent cycles of this cause the rocks to break
68
what is chemical weathering ?
the breakdown of rocks through chemical reactions
eg. solution - when rock minerals such as rock salt are dissolved
69
what is carbonation ?
rainwater absorbs CO2 from the air to create a weak carbonic acid with reacts with rocks and they dissolve
acid rain reacts with limestone also dissolving rocks
70
what is oxidation ?
when minerals become exposed to the air through cracks and fissures, the minerals become oxidised which causes them to expand and crack
71
what is biological weathering ?
the breakdown of rocks by organic activity
eg. plant roots growing into cracks and exerting pressure, birds burrowing into cliff cracks, seaweed acids
72
what is mass movement ?
the movement of material down a slope under the influence of gravity
creeps, flows, slides and falls
dependent on: cliff slope, rock type and structure, vegetation, saturation of ground, weathering
73
what is soil creep ?
the movement of particles downhill due to the natural rise and fall or particles due to wetting and drying
leads to formation of shallow terracettes
very slow
74
what is solifluction ?
the top layers of land thaw and the bottom layers stat frozen due to permafrost , the top layers flow over and form solifluction lobes
75
what are mudflows ?
increase in the water content of soil can reduce friction leading to earth and mud to flow over underlying bedrock
76
what are rockfalls ?
occurs on sloped cliffs when exposed to mechanical weathering
it leads to scree ( rock fragments building up at the base of the slope )
77
what are landslides ?
heavy rainfall lead to water between joints and bedding plans in cliffs which can reduce friction and lead to a landslide , it occurs when a block of intact rock moves down the cliff face very quickly along a flat slope
78
what is slumping ?
movement of sediment along a curved slop creating a terraced appearance, the build up in PWP causes land to collapse under its own weight
79
what is pore water pressure?
When water gets trapped in the slope and forces rock particles apart, weekening the slope
80
what is runoff ?
overland flows of water may erode the clifface or pick up sediment, when it enters the littoral zone it can increase pollution as it can carry chemicals picked up
81
What is the sequence that causes the formation Of caves, arches, stacks and stumps ?
1. the faults in headland are evaded by hydraulic action and abrasion to create small caves
2.a blowhole may form at this point if the overlying rock in the cave collapses
3. more erosion widens the cave
4. erosion and sub-aerial processes can erode through to the side of the cliff creating an arch
5. the arch continues to widen and will fall under its own weight through mass movement, leaving a Stack
6. the stack is eroded into a stump
7. a wave cut platform can be left afterwards
82
What are steep cliffs ?
1. steep cliffs - most common, rock is fairly resistant to erosion , sedimentary rocks that have a vertical strata and the absence of a beach, long fetch and high energy waves promote steep cliff development
83
what are gentle cliffs?
found in areas with weaker rocks which are less resistant to evasion , prone to slumping. low energy waves and a short fetch lead to the Formation of scree overall reducing the cliff angle
84
What is the rate of retreat ?
how much the cliff retreats dependent on marine factors (fetch, beach, wave energy) and terrestrial factors (sub-arial processes, geology, rock strength )
85
What is an example negative feedback mechanisms in a coastal system ?
during a storm part of a cliff may collapse so the material produced will protect the base of the cliff reducing further cliff erosion and recession
86
how is a wave cut notch and platform formed ?
1. when waves erode a cliff , the erosion is mostly concentrate around the high tide line, hydraulic action and corrasion create a wave cut notch
2. as the notch gets deeper the top of the cliff weakens and becomes unstable and collapses under its weight
3. this leaves a platform behind of the unaffected cliff base beneath the wave cut notch
4. this continues over time till a wave cut platform is formed
87
what is a beach ? ( and how it is created )
a depositional landform that stretches form the low tide to the high tide line
is created when sediment is deposited near the coastline when waves lose their energy, this depends on the angle of the prevailing winds in relation to the land
88
what is beach accretion ?
when the beach is being built up by constructive waves usually during the summer months
89
what is beach excavation ?
occurs in winter when destructive waves remove sediment from the beach
90
what is a swash aligned beach ?
wave crests approach perpendicular to the coast so there is limited longshore drift, the sediment does not travel far
wave refraction may reduce the speed of the high energy waves leading to the formation of a shingle beach
91
what is a drift aligned beach ?
waves approach at a significant angle so LSD is increased , formation of a spit at the end of the beach
the start of the beach may have more larger sediment and further down the sediment is more weathered into smaller pieces
92
what are berms ?
ridges which mark where the high tide line is at different time of the year, there may be several berms on a beach characterized by small ridges or a change in the sediment type
93
what are cusps ?
small curved dips in the beach where the swash comes in and are slightly lower than the rest of the beach, creating undulations in the beaches profile
94
what are runnels ?
small ridges that are often found in smooth wet sand further towards the sea
95
how does the size of the beach sediment change along the profile?
the beach profile and sediment type are very dependent on the distance from the shoreline
larger sediment is found towards the top of the beach where its left from winter storms and when the backwash is less powerful than the swash larger sediment is deposited. scree is also found here as a result of mass movement.
the smaller sediment is moved further down
96
what is a spit ?
a long narrow strip of land is formed when LSD causes the beach to extend out to sea usually due to a change in the direction of the coastline. the length of the spit depends on the changing currents and rivers which will effect the rate of deposition
97
how is a salt marsh formed ?
a spit projection this can create a salt marsh due to the sheltered saline environment where water flow speed is slower allowing more deposition
98
what is a recurved spit ?
when the wind direction or wave direction can cause the end of the spit to be curved, this can happen multiple times overtime leading to a compound spit
99
what is a barrier beach/bar ?
when a beach or spit extends across a bay to join two headlands, this traps water behind it leading to the formation of a brackish lagoon which is separated from the sea
some have also formed from sea level rise
100
what is a tombolo ?
a bar or beach that connects the mainland to an offshore island and is formed due to wave refraction off the coastal island reducing wave velocity, leading to the deposition of sediments
101
what are offshore bars ?
offshore region where sand is deposited as the waves don't have enough energy to carry the sediment to shore
the can be formed when the wave breaks early and deposit sediment
or as a result of backwash from destructive waves
they may absorb wave energy, reducing erosion in some areas
102
what is vegetation succession ?
is a plant community that changes over time
on coasts where there is a supply of sediment and deposition occurs , pioneer plants begin to grow
103
what is sand dune succession ?
embryo dunes form around pioneer plants, which die and release nutrients into the sand increasing the amount of vegetation able to grow within the dune
these dunes alter environmental conditions from harsh and salty to a survivable environment
104
whats an example of a pioneer plant ?
marram grass
- tough and flexible
- adapted to reduce water loss through transpiration
- their roots grow up to 3 meters deep and tolerate hot temperatures
105
what is the stages of making a salt marsh ?
1. agal stage- algae (blue green )grows in bare mud and roots bind together
2. pioneer stage- types of grass (marrow )grow and their roots establish allowing the estuary to grow
3. establishment stage- salt marsh grass grows creating a carpet of vegetation and the height increases
4. stabilisation- sea thrift and sea lavender grow so salt rarely gets submerged beneath the marsh
5. climax vegetation- rush and red fescue grass grow since the salt marsh is only submerged once or twice a year
106
why is vegetation important at coasts ?
- roots of plants bind soil together which helps to reduce erosion
- when completely submerged they provide a protective layer for the ground so its less easily eroded
- plants reduce the wind speed at the surface and so less wind erosion occurs
107
what are the different types of dunes in order of smallest to largest ?
1. embryo dunes
2. yellow dunes - tallest dune
3. grey dunes - most varied plant growth
4. dune slack - as the wate table rises water is trapped between hollows between dunes
5. heath and woodland
108
how do estuarine mudflats and saltmarshes form ?
deposition occurs in river estuaries because the flow meets incoming tides and stops, this can also happen in sheltered areas like behind a spit
sediment deposited leads to a build up of mud and flocculation occurs
pioneer plants colonise the area
a meadow is formed as sections of the salt marsh rise above sea level leading to the climatic climax of the vegetation succession
109
how stable are depositional landforms ?
not stable as they consist of unconsolidated sediment
during storms large amount of sediment can be eroded or transported
they rely on a continuous supply of sediment to balance the erosion which may see some landforms changes as their dynamic equilibrium shifts
110
what causes sea level change in the short term ?
high and low tide
wind strength
changes in wind direction
changes in atmospheric pressure
111
what is isostatic change?
occurs when the land rises or falls relative to the sea and is a localised change
can happen as a result of isostatic subsidence ( when glaciers weigh down the land beneath) and once the glacier melts the land rebounds and rises again
112
what is eustatic change ?
affects the sea level across the whole planet
Eustatic for Everywhere
can be due to thermal expansion/contraction or changes in glaciers
113
what is thermal expansion ?
the process of water expanding when it gets warmer
this cause the volume to increase leading to rising sea levels
114
how much lower was the sea level in the ice age than now ?
100 m lower
115
what has the IPCC predicted for sea level change by 2100 ?
increase for 0.3 - 1.0 m
116
what are emergent coastal landforms ?
when the land has been raised in relation to the coastline eg. arches, stacks and stumps, raised beaches and wave cut notches
117
what are submergent coastal landforms ?
occur when the sea level rises or the coastline sinks in relation to the sea
eg. rias, fjords and dalmatian coasts
118
what is a ria ?
formed when sea level rises and floods narrow winding inlets and river valleys
they are deeper at the mouth of the inlet
119
what are fjords ?
formed when rising sea levels flood deep glacial valleys to create natural harbours
deeper in the middle section
120
what are dalmatian coasts ?
occurs when valleys running parallel to the coast become flooded as a result of sea level rise
this leaves a series of narrow, long and rugged islands eg. in croatia
121
what are the risks that occur from sea level rise ?
-cause aquifers to be polluted in low lying islands
- flood coastal cities
- increase risk of tropical storms and tsunamis
122
what is coastalisation ?
the process by which the coast is being developed and people are moving to the coast, this can be a result of urbanisation as lots of large cities are coastal
123
what is a storm surge?
a result of the low pressure created by a large weather event
it raises the sea level and causes flooding and can overwhelm ( inundate ) flood defences
124
what can cause more intense storm surges ?
- removing natural vegetation: such as mangroves which provide protection against extreme weather, they absorb wave energy and trap sediment leading to accretion on the coast
- global warming: leads to more frequent and severe storms
125
