Coastal Landscapes content Flashcards
1
Q
Is the coast an open or closed system?
A
the coast is an open system as it receives inputs and outputs outside the system.
2
Q
what are sediment cells?
A
sections of the coast
closed systems (not fully closed)
11 sediment cells in the UK
operate in a state of equilibrium
3
Q
What is negative feedback?
A
lessens any change that has occurred in the systems taking it back to dynamic equilibrium
Example= storms erodes beach more taking it away from dynamic equilibrium but as the waves lose their energy offshore bar is created which then dissipates wave energy preventing erosion of the beach, this offshore bar is eroded and once its gone normal conditions are restored
4
Q
What is positive feedback?
A
exaggerates the change making the system more unstable and moving further away from dynamic equilibrium
Example= people trampling on sand dunes, now they are more susceptible to erosion, once they’ve eroded beach is more at risk from erosion so taking beach further away from equilibrium.
5
Q
What is the littoral zone? Name the subzones
A
Littoral zone is the area of coast subject to wave action
Backshore= area above high tide only influenced by exceptionally large waves (storm surges)
Foreshore=area between high tide and low tide mark (inter tidal zone)
Nearshore= breaker zone
Offshore= beyond the influence of the waves
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6
Q
Valentines classification
A
advancing coastline= emerging or deposition are prominent
retreating coastline= submerging or erosion are prominent
7
Q
Why may some coasts be difficult to classify?
A
-energy can change throughout the year (low energy env can become high energy when storms arrive)
-local geology can produce rocky areas within coastal plain landscapes
-sheltered bays can encourage deposition in areas with long fetches and destructive waves
8
Q
What is morphology?
A
the shape of the coast
largely determined by geological structure and lithology
9
Q
What is geological structure?
A
refers to the arrangement of rocks…
in layers or folds and the joints and bedding planes within them
10
Q
What are bedding planes?
A
horizontal breaks in the strata
caused by gaps in time during periods of rock formation
11
Q
What are dips?
A
angle at which rock strata lie
can be horizontal/vertical and seawards/landwards
12
Q
What are faults?
A
formed when pressure to which rock is subjected to exceeds its internal strength- causing it to fracture
13
Q
What are folds?
A
formed by pressure during tectonic activity which makes rock buckle and crumble
14
Q
What are joints?
A
vertical cracks
caused by:
-contraction (shrinking) as sediments dry out
-by earthquakes during tectonic uplift
15
Q
What are strata?
A
layers of rock
16
Q
What impact does dip have on cliff profiles?
A
horizontal strata= steep cliff profile- indentations form in the cliff face due to exploitation of bedding planes.
strata dips seaward= creates unstable cliff= gravity causes mass movement e.g. rock fall
landward strata dip= steep stable cliff (exploitation of exposed bedding planes can create an irregular profile)
17
Q
What is lithology?
A
rock types
-bedrock lithology (igenous,metamorphic or sedimenhtary)
-surface deposits
18
Q
What is igneous rock?
A
e.g basalt and granite
-non porous
-tightly packed
-crystalline= interlocking crystals
-impermeable= no bedding planes or joints
-very hard
-very slow recession rates
19
Q
What is metamorphic rock?
A
e.g, slate, marble
-non porous
-crystalline= heat and pressure flattens rounded crystals in sedimentary rock
-hard but some rocks are prone to mass movement
-impermeable= no bedding planes or joints
20
Q
What is sedimentary rock?
A
e.g. chalk, sandstone
-clastic
-porous due to rounded crystals
-permeable due to presence of bedding planes and joints
-soft
-faster recession
-vulnerable to chemical weathering
21
Q
What are surface deposits?
A
-unconsolidated rock found on top of bedrock left behind by rivers, glaciers or winds
-e.g. glacial till= mixture of sand, clay and stones left behind by glaciers after the last ice age= very soft can recede by 1m py= found in much of Eastern England
22
Q
what happens in corrasion?
A
sand and pebbles hurled against the cliffs at high tide
23
Q
what happens in attrition?
A
rocks and pebbles hit against each other wearing each other down
becoming round and smaller
24
Q
what happens in corrosion?
A
mildly acidic seawater causes alkaline rock i.e limestone to be eroded
25
what happens in hydraulic action?
as a wave crashes onto cliff face
air is forced into joints and faults within the rock
the high pressure causing causing cracks to widen
26
what happens in abrasion?
sediment is moved along the shoreline (rubbing) so is worn down over time
27
what happens in wave quarrying?
similar to hydraulic action
hut directly pulls away rocks from the cliff face as the force of the breaking wave hammers the rock surface
28
how does the cave-arch-stack-stump sequence occur?
occurs on pinnacle headlands
hydraulic action and abrasion widens faults in base of headland- over time creates a cave
continued erosion erodes this cave to the other side of headland- forming an arch
arch continues to widen until it is unable to support itself falling under mass movement- leaving a stack
base is attacked until it collapses into a stump
29
how does a wave-cut notch and platform form?
marine erosion attacks base of cliff between high tide and low tide mark creating a notch
notch deepens until cliff face becomes unstable and falls under its own weight-mass movement
leaves behind a platform of the unaffected cliff base below low tide mark
(retreating cliffs occur through this process)
30
how do blowholes form?
combination of a pot hole on top of a cliff created by chemical weathering and a cabe formed by marine erosion
as cave erodes deeper into cliff face and pothole deepens
they meet so a channel is created
this means incoming waves can travel into and up cliff face
31
What are geos?
narrow inlets created by the erosion of joints in resistant rock coastlines
32
What is long shore drift?
main marine transport process= transports sediment along the beach and between sediment cells
1. waves hit the beach at angle of the prevailing wind
2. waves push sediment in this direction (swash)
3. wave then carries sediment back down the beach at an angle perpendicular to the beach (90 degrees)
4. this moves sediment along the beach over time
(strongest when waves approach at 30 degrees)
33
What is traction?
large heavy sediment rolls along the seabed
34
What is saltation?
smaller sediment bounces along the sea bed
35
What is suspension?
small sediment carried in water column
36
What is solution?
dissolved material is carried within the water
37
What is the difference between swash-aligned and drift-aligned
Swash aligned:
- wave crests approach parallel to coast
-limited LSD
Drift-aligned:
-waves approach at a significant angle
-LSD causes sediment to travel far up beach
38
What are the two types of deposition?
Gravity settling:
- waves energy becomes very low
heavy rocks and boulders deposited followed by next heaviest
Flocculation:
- clay particles clump together due to chemical attraction
-sink to high density
39
What are spits?
long narrow strip of land formed due to deposition
long shore drift occurs along the coast but as they lose energy (go behind a headland) they deposit sediment
over time creates a spit
as prevailing wind changes direction a hook may form
the sheltered area behind can turn into a salt marsh
40
What are bars?
Spit which overtime crosses a bay (because of LSD) joining two headlands
body of water behind bar=lagoon
41
What are cuspate forelands?
occurs with triangular shaped headlands.
LSD occurs along each side of the headland=create beaches
when both beaches meet= cuspate foreland.
42
What is a tombolo?
bar/beach that connects mainland to an offshore island
formed due to wave refraction of the coastal island reducing wave velocity leading to deposition
43
What are offshore bars?
region offshore where sand is deposited
wave don't have enough energy to carry sediment to shore
can be formed if waves break early
44
What is succession?
a long-term change in a plant community in an area.
on coasts pioneer plants begin to grow in bare mud and sand.
Due to the salty soil conditions only certain plants can grow there.
As more deposition occurs and
the vegetation dies and releases nutrients into the sand this reduces the saltiness of the soil which means different plants can start growing there.
this continues over time allowing plants to colonise.
45
What are the stages of sand dune succession?
Sand dunes (psammosere) occur when prevailing winds blow sediment to the back of the beach
1. Embryo dunes = Upper beach area where sand starts to accumulate around a small obstacle (e.g driftwood)
2.Dunes= As more sand accumulates and the dune grows taller, pioneer plants such as sea rocket may colonise, which stabilises the dune.
2. Yellow dunes= The tallest of the dune succession. Pioneer plants alter the pH and humus content of the dunes as they die and decay allowing other plants such as marram grass to grow trapping more sand
3. Grey dunes = humus content increases so more plants such as shrubs can grow as more nutrients
4. Dune slack=The water table rises closer to the surface, allowing the development of moisture-loving plants (e.g. willow grass)
5. Heath and woodland= Soils develop as there is a greater nutrients content, allowing for less brackish plants to thrive. Trees will also grow (willow, birch, oak trees) with the coastal woodland becoming a natural windbreak to the mainland behind.
46
What factors are required for sand dune succession?
-large quantities of sediment
--large tidal range=allows and to dry so can be picked up
- frequent and strong onshore winds= that can carry sediment to back of beach
47
What are the stages of salt marsh (halosere) succession?
Firstly rivers bring mud and clays deposit them in sheltered areas along estuary sides through flocculation
1.Algal Stage - Gut weed & Blue green algae colonise as they can grow on bare mud, which their roots help to bind together.
2.Pioneer Stage - Cord grass & Glasswort grow, which can survive being flooded 2 a day their roots begin to stabilise the mud allowing the estuarine to grow.
3.Establishment Stage - Salt marsh grass & Sea asters grow on drier areas so vegetation builds up and the height of the salt marsh increases.
4. Stabilisation - Sea thrift, Scurvy grass & Sea lavender grow, and so salt rarely ever gets submerged beneath the marsh.
5.Climax vegetation - Rush, Sedge & Red fescue grass grow since the salt marsh is only submerged one or twice a year as above high tide line
48
What are xerophytes and halophytes/brackish?
Xerophytes= plants that are tolerant to dry conditions (sand dune succession)
Halophytes= plants that are tolerant to salty conditions (salt marsh sucession)
49
How is marram grass adapted as a pioneer plant?
-tough and flexible=can cope with being blasted with sand
-adapted to reduce water loss through transpiration
-roots grow up to 3m deep
-can tolerate temp of up to 60 degrees
50
What is the importance of vegetation/plant succession in coasts?
-Roots of plants bind soil together, stabilising it, which helps to reduce erosion allowing coasts to advance
-When completely submerged, plants provide a protective layer for the ground and so the ground is less easily eroded.
-Plants reduce the wind speed at the surface and so less wind erosion occurs.
-provides a buffer between the land and the sea acing as a long term flood and storm defence
51
What is weathering? Name the 3 types
Weathering is the breakdown of material in situ
-mechanical=breakdown of rocks due to exertion of physical forces
-chemical= breakdown of rocks through chemical reactions
-biological= breakdown of rocks due to actions of plants, bacteria and animals
52
What are examples of mechanical weathering?
-Freeze thaw weathering= water enters cracks then freezes over night, expanding in volume by around 10% putting pressure on rocks so they crack.
-Salt Crystallisation= seawater evaporates so salt s left behind, they will grow in size exerting pressure and forcing cracks to widen
-Wetting and drying= rocks (e.g clay) expand when wet then contract when drying, this constant cycle will cause rocks to break up.
53
What are examples of chemical weathering?
-Carbonation=rainwater absorbs CO2 which then reacts with limestone to form calcium bicarbonate which is then easily eroded.
-Oxidation= minerals are oxidised when exposed to air through cracks which increases its volume causing rock to crumble e.g. iron ions becoming iron oxide
-Solution= rock minerals such as salt are dissolved
54
What are examples of biological weathering?
Plant roots= grow into cracks of rocks exert pressure splitting rocks
Birds= e.g. puffins dig burrows into cliffs creating weaknesses
Rock Boring= e.g clams secrete chemicals that dissolve rock + may burrow into rock surface
Seaweed acids= some contain pockets of sulfuric acid- dissolve some of rocks minerals
Decaying vegetation= water that flows over decaying vegetation turns acidic then flows over coasts dissolving rock
55
What is mass movement?
two categories:
-slide= sediment keeps its place within the whole material but moves downhill
-flow= all the material flows down and mixes
56
What are the types of flows?
-Soil creep= movement of soil particles downhill (slowest)
-Soilifluction= occurs as the top layers of land thaws during summer (but the lower layers still stay frozen due to permafrost) and surface layers flows over the frozen layers (mainly in tundra areas)
-Mudflows= increase in water content of soil reduces friction so mud flows over underlying bedrock
57
What are the types of slides?
-Rock falls= occurs on sloped cliff (<40degrees) when exposed to chemical weathering
-Rock slides= water between joints and bedding planes reduces friction and leads to more sliding
-Slumps= when soil is saturated with water causing a rotation of materials forming rotational scars and terraced cliff profiles
58
What factors affect the type of mass movement that occurs?
-angle of slope/cliff
-lithology and geology
-vegetation cover on cliff face
-saturation of ground/previous weather patterns
59
What is the difference between a concordant and discordant coastline?
Concordant:
-rock strata run parallel to coast
-Dalmatian coasts
-haff coasts
-coves
Discordant:
-rock strata run perpendicular to the sea
-headlands and bays
60
How do coves form?
Form on concordant coasts
1. initially erosion occurs at same speed along whole coastline
2. over time waves start to exploit weaknesses such as faults and large joints
61
How do headlands and bays form?
form on discordant coasts
waves erode softer rocks faster than harder rock
hard rock forms rugged, rocky headlands that stick out into the sea
indented shape of coastline causes waves to refract as they approach the headlands so concentrates wave energy on them (increasing rate of erosion= cave-arch-stack-stump)
waves slow down in bays and lose energy (depositing bay-head beaches)
62
What are the factors affecting wave size/energy?
-strength + duration of wind
-water depth
-fetch distance
63
What are the differences between constructive and destructive waves?
Constructive:
-strong swash, weak backwash
-low wave height (>1)
-long wavelength
-low frequency
-deposition>erosion
-dominate in summer
Destructive:
-weak swash, strong backwash
-high wave height (<1)
-short wavelength
-high frequency
erosion>deposition
-dominate in winter (+storms)
64
What are swell waves?
-waves generated from storms in middle of ocean that maintain their energy for thousands of miles
-distance over which they travel=fetch
-lager the fetch=more destructive
65
What are beach profiles?
-Steep, convex profile= swash pushes material up the beach in a spilling breaker (typical of beaches in calm, summer conditions
-Steep, concave profile= berns eroded by plunging breakers (typical of beaches in stormy, winter conditions)
66
What are the characteristics of a high energy coastline?
-large fetch
-destructive waves
-rocky cliffed coastline
-high steep relief
-erosional landforms
-erosion>deposition
67
What are the characteristics of a low energy coastline?
-shorter fetch
-constructive waves
-sandy beaches
-low relief
-depositional landforms
-deposition>erosion
68
What are the causes of short term sea level change?
-high tide and low tide: due to gravitational pull of the moon (daily)
-wind strength and duration: can change causing a change in sea level
-atmospheric pressure: lower the pressure=higher the sea levels
69
What are the types of long term sea level change?
Sea levels have risen by 120m since the last ice age 18,000 years ago
Isostatic- localised sea level change= when land rises or fall in relations to the sea
Eustatic- global sea level change= when sea level rises or falls
70
How does isostatic sea level change occur?
71
How does eustatic sea level change occur?
72
What are example of emergent landforms?
-Fossil cliffs
-Raised beach
73
What are examples of submergent landforms?
-rias
-fjords
-Dalmatian coasts
74
What is coastalisation?
movement of people towards the coast
75
What are storm surges?
occurs when there is a short term change in sea level which may be due to low pressure during a depression or tropical cyclone.
76
How are storm surges formed?
1. a low pressure system such as a depression or tropical cyclone develops offshore
2. rising air within the low pressure system draws the sea upwards into a dome
3. onshore winds drive the dome of seawater towards the coastline
4. the increased height in sea level allowing the water to surge inland
77
What factors exacerbate or minimise storm surges?
-subsidence of land (tectonic activity/post glacial adjustment)
-compaction of deltas= allow storm surge to travel further inland
-deforestation= mangrove forests provide provide protection against extreme weather events so removal of them allows storm surges to travel further in land
-global warming= frequency and intensity of storms will increase due to increased evaporation so severity of storm surges and flooding will rise. Furthermore sea level rise allows storm surges to travel further inland affecting a greater area=more people
-population density= in coastal zones population density is increasing= increasing number of people, property and infrastructure at risk
-flood defences= prevent storm surges inundating land
-forecasting and warning systems= reduce vulnerability/allow for evacuation
78
What are the general consequences of storm surges?
-reduced house and land prices=economic loss for homeowners and companies
-insurers often don't provide home insurance for people living along coastlines at extreme risk of erosion from storm surges
-can damage plant succession and coastal landform
-people may lose their homes so forced to migrate= environmental refugees
79
What are the four main approaches to coastal management?
1. Hold the line= defences built in an attempt to keep the shore at its current position
2. Managed realignment= some defences built so coastline moves inland naturally but still managed.
3. Advance the line= defences built in an attempt to move the shore seawards
4. No active intervention= no defences are put in place- coast allowed to erode
80
What are the factors influencing chosen approach?
-Economic value= e.g. gas terminal at Easington was protected yet somewhere of low business and tourism value would likely not be
-Ecological and cultural value= e.g historical sites or politically important sites like London and the houses of parliament.
-Social pressure= pressure from locals in Mappleton resulted in groynes being built
81
What are EIAs?
Environmental Impact Assessment
They are carried out to find out what effect coastal management might have on:
-water movement and sediment flow
-water quality
-marine ecosystems
-air quality
82
What is cost benefit analysis?
analysis that is carried out to see whtether the expected effects outweigh the costs
If they don't then management will likely not be put in place
83
What is ICZM?
Stands for integrated coastal zone management
a sediment cell is manged as a whole
in UK different councils work together to manage coasts together
recognises the importance of peoples livelihoods
recognises that managemet must be sustainake where economic devlopment is importnat but should not come at a costs for environment
84
What are SMPs?
Shoreline Management Plans
identifies all of the activities both natural and human which occur in a sediment cell
85
What is hard engineering/ Examples?
man made structures that aim to prevent erosion
Examples:
-offshore breakwater= Rock barrier which forces waves to break before reaching the shore
-groynes=Timber or rock protrusions that trap sediment from LSD
-sea wall= Concrete structures that absorb and reflect wave energy, with curved surface
-revetments=Wooden or concrete ramps that help absorb wave energy
-riprap/rock armour= Large rocks that reduce wave
energy, but allow water to flow through
86
What are the advantages and disadvantages of offshore breakwater?
+Effective at reducing waves’ energy
-Visually unappealling
-Navigation hazard for boats
-Can interfere with LSD
87
What are the advantages and disadvantages of groynes?
+Builds up beach, protecting cliff and
increasing tourist potential
+Cost effective (compared to sea wall e.t.c)
- Visually unappealing
- Deprives areas downdrift of sediment
increasing erosion elsewhere
88
What are the advantages and disadvantages of sea walls?
+Effective erosion prevention
+Promenade has tourism benefits
-Visually unappealling
-Expensive to construct and maintain
-Wave energy reflected elsewhere, with impacts on erosion rates
89
What are the advantages and disadvantages of revetments?
Cost effective
-Visually unappealing
-Can need constant maintenance with added costs
90
What are the advantages and disadvantages of riprap?
+Cost effective
-Rocks are sourced from elsewhere,
so do not fit with local geology
-Pose a hazard if climbed upon
91
What is soft engineering? Examples?
aims to work with and complement the existing environment
Examples:
-beach nourishment= sediment is taken from offshore sources to build up the existing beach
-cliff regrading and drainage= Reduces the angle of the cliff to help stabilise it.
-dune stabilisation= Marram grass planted. The roots
help bind the dunes, protecting land behind
-marsh creation= Type of managed retreat
allowing low-lying areas to flood
92
What are the advantages and disadvantages of beach nourishment?
+builds up beach= protecting cliff and increasing tourism potential
+cost effective
+looks natural
- dredging may have consequences on local coastal habitats
93
What are the advantages and disadvantages of cliff regrading and drainage?
+cost effective
-may look unnatural
-cliff may collapse suddenly as it is drier (rock falls)
94
What are the advantages and disadvantages of dune stabilisation?
+cost effective
-time consuming
95
What are the advantages and disadvantages of marsh creation?
+creates an important wildlife habitat
-farmers lose land so may need to be compensated
