1
Q
Which of the spheres are most likely to interact with coasts
A
Hydrophere
Lithosphere
Biosphere
2
Q
What type of systems are coasts considered to be?
A
The coast can be considered as an open system as it receives inputs from outside the system an transfers outputs away from the coast and into other rock systems
3
Q
Whilst coasts are open systems, what should i be expected to consider them as?
A
Closed systems in some circumstances such as during scientific research and coastline management planning
4
Q
The coast is a __________ boundary area
A
The coast is a dynamic boundary area
5
Q
Inputs into coastal systems
A
Waves, Tides, Currents
Sun, Precipitation, Wind
Human:
Pollution, Settlement, management
6
Q
Processes in coastal systems
A
Erosion
Transportation
Deposition
7
Q
Outputs in coastal systems
A
Landforms
Loss of sediment taken out to sea (off-shore bars)
8
Q
Energy in coastal systems
A
Solar, Waves, Currents, Precipitation
9
Q
Stores/Components in Coastal Systems
A
Land forms
Oceans
Spheres
Off-shore bars
10
Q
Why are beaches in dynamic equilibrium
A
Beaches will increase in size however increase in output
-They don’t stay in equilibrium for very long naturally
11
Q
What is a system
A
A collection of interrelated parts that work together in an environment
12
Q
Give an example of a material input into a coastline system
A
Sediment carried into the coastal zone by rivers
13
Q
State one natural system which heavily influences coasts
A
The Ocean-eroded rock material transported offshore to the ocean, caused by tectonic systems
14
Q
How many sediment cells are there in England and Wales
A
There are eleven major sediment cells
15
Q
How have the glacial and interglacial periods of the quaternary period (last 2.6 million years) affected coasts
A
Sea levels rose and fell several times during glacial and interglacial periods. This has affected the precise location of coastal processes at the edges of land masses
16
Q
Processes affecting landforms
A
Wave Action
Erosion and Weathering
Sub-Aerial processes
Tides
Long-shore drift
Mass Movement
17
Q
Factors affecting Coastal landforms
A
Human activity
Geology
Lithology (Rock characteristics)
Vegetation
Sediment
Slope: Depth etc
Prevailing winds
Sea level change
18
Q
Different coastal landforms
A
Rocky Coasts:
Cliffs, caves, arches and stacks,
Slumps, slides, flows
Beach Coasts:
Swash-aligned and drift-aligned beaches
Spits, bars and tombolos
Sand dunes/ salt marshes
19
Q
wind as an energy source in coastal systems
A
Air moves from high to low pressure = wind
UK prevailing winds come from SW, huge fetch over the atlantic
Wind energy is determined by strength of wind, duration of wind blowing (fetch)
20
Q
tides as energy sources in coastal systems
A
-changes in the water level of the sea
-Caused by gravitational pull of the moon
-UK has two high and low tides a day
-Difference between high and low tide = tidal range
21
Q
what does a high tidal range mean
A
Powerful Tidal currents, which is a source of energy, often in estuaries
22
Q
Currents as energy sources in coastal systems
A
-Currents are driven by several factors, tides are one of these
-Tides involve water moving up and down; currents involve the movement of water back and forth
More factors influencing currents include: Wind, the shape of the land, and even water temperature
23
Q
Characteristics of high energy coastlines
A
-Rocky coasts
-Stretches of the Atlantic-facing coast, where the waves are powerful for much of the year e.g. Cornwall or Scotland
-Where the rates of erosion > Rate of Deposition
-Erosional landforms such as Headlands, cliffs, wave-cut platforms
24
Q
Characteristics of Low-energy coastlines
A
-Sandy and estuarine coasts
-Stretches of coast where the waves are less powerful
-Where the coast is sheltered from large waves
-Where rate of deposition > Rate of erosion
-Depositional landforms instead of erosional landforms
25
What is the main form of energy at coasts
Waves, although they can be generated by tectonic activity or underwater landslides creating a tsunami, they are mostly formed by wind.
26
Factors affecting wave energy
The strength of the wind - determined by the pressure gradient
The duration of the wind - the longer the wind blows, the more powerful waves become
The fetch - The distance of open water which the wind blows = the longer the fetch = the more powerful waves become
27
Formation of constructive waves
-Distance weather systems generate these waves in the open ocean
28
Formation of destructive waves
Local storms are responsible for these waves
29
Wave form of constructive waves
Low, Surging waves, with a long wavelength
30
Wave form of destructive waves
-High, plunging waves with a short wavelength
31
Do constructive waves cause beach gain or loss
Beach gain
32
Do destructive waves cause beach gain or loss
Beach loss
33
Beach profile associated with constructive waves
Usually associated with a gentle beach profile although, over time, they will build up the beach and make it steeper
34
Beach profile associated with Destructive waves
Usually associated with a steeper beach profile, over time they will flatten the beach
35
Negative feedback on a beach example in summer
Constructive wave = material moved up beach = steeper beach created = encourages destructive waves = gentle gradient as beach loss = Constructive wave and repeat
36
Negative feedback loop example coasts in winter
Winter Storms = Destructive Waves = Moves material down beach = Gentle Gradient = Encourages constructive waves = steeper beach gradient built
37
Positive feedback loop regarding coastal systems
People walking over sand dunes destroys vegetation growing there and causes erosion
As the roots from vegetation have been holding the sand dunes together, damaged vegetation makes sand dunes more vulnerable to erosion = increased erosion
Eventually sand dunes will be completely eroded leaving more of the beach open to erosion taking the beach further away from its original state.
38
Marine inputs at sediment cells
Waves, tides ,salt spray
39
Non marine inputs into sediment cells
-Sediment that has originated from rivers or eroded from cliffs
-Offshore sand banks
-human activity : Pollution, recreation, settlement, defences
40
Examples of stores at sediment cells
Rivers
Beaches
Sand Dunes
Spits
Bars and Tombolos
Headlands and bays
Cliffs
Wave cut platforms
Arch Cave stack Stump
Salt marshes
Offshore Bars
Nearshore sediment
41
Examples of different transfers at sediment cells
Wind-blown sand
Mass-movement processes
Longshore drift
Weathering
Erosion - Hydraulic Action, Corrosion, Attrition, Abrasion
Transportation - Suspension, Traction, Solution
Deposition - Gravity settling
42
Rivers acting as a source of sediment
Sediment that is transported in rivers often accounts for vast majority of coastal sediment, especially in high-rainfall environments
43
Cliff erosion as a source of sediment
Extremely important locally in areas of relatively soft or unconsolidated rocks
44
Longshore drift as a source of sediment
Sediment is transported from one stretch of coastline to another stretch of coastline
45
Wind as a source of sediment
In global or hot arid environments, wind-blown sand can be deposited in coastal regions
46
Glaciers as a source of sediment
areas of the world such as Alaska, Greenland and Antarctica, ice shelves calve into the sea, depositing sediment that was trapped within the ice
47
Offshore as a source of sediment
Sediment from offshore can be transferred into the coastal zone, by waves, tides and currents
48
What is a sediment budget
The different between gains and losses of sediment on a coastline
49
Primary energy source for sediment cells
The sun is the primary source of energy, converted into wave energy by the wind
50
Define tides and currents
Tides and currents are changes in the water level of seas and oceans caused by the gravitational pull of the moon
51
How many tides does the UK experience daily
Two high and two low tides
52
Define tidal range
Difference between high and low tides
53
What does a high tidal range mean
Creates relatively powerful tidal currents which are important sources of energy
54
What are Rip currents
Strong localised underwater currents that occur on some beaches, posing a considerable danger to swimmers and surfaces
55
How do rip currents normally form
When a series of plunging waves cause a temporary build up of water at the top of the beach
56
Where are rocky coasts normally found
In high-energy environments, because the rate of erosion exceeds the rate of deposition
57
Where are sandy and estuarine coastlines found
In generally low-energy environments, where waves are less powerful or where the coast is sheltered from large waves
Where the rate of deposition exceeds the rate of erosion.
58
Difference between marine processes and Sub-aerial processes
Marine processes operate upon a coastline and are connected with the sea, such as waves, tides and longshore drift
Sub-aerial processes operate on the land but affect the shape of the coastline e.g. such as weathering, mass movement and run off
59
Majority of wales coastlines are over ___ m high
30m
60
Which coastline in Britain has seen the greatest cliff recession
The holderness coastline
61
What factors may cause variation in cliff profiles
Rock type
high/low energy coastlines
Height of cliff
62
Different types of weathering
Chemical weathering
Biological weathering
Mechanical weathering
63
Types of mass movement
Mud flows
Rotational slumping
Rockfalls
Landslides
Soil Creep
64
What is Soil Creep?
The very slow and gradual downhill movement of soil and rock on a slump, usually driven by gravity that’s changes become visible over time
65
What is rotational slumping
Where a section of rock or soil moves downslope along a curved slip plane, causing it to rotate backwards, often forming a ‘scar’ on the cliff face
66
What is meant by coastal geomorphology
The study of coastal landforms and the processes which affect them
67
Coastal processes
Mass movement, erosion, weathering, transportation and deposition
68
How can biological weathering occur at a cliff edge
Roots from grass may dig into rock
69
What is hydraulic action
process occurs when waves crash against a cliff or rock surface, trapping air and water in cracks and crevices
The force of the water compresses the air, which creates pressure to break rocks apart
70
What is wave quarrying
Occurs when the sheer force of powerful waves breaks off chunks of rock from a cliff or shoreline
Impact of rocks exerts significant pressure, dislodges pieces of rock, contributing to coastal erosion
71
What is abrasion/corrasion
Happens when particles like sand, pebbles and other larger rock fragments carried by waves or wind are thrown against rock surfaces, causing them to collide
72
What is attrition
Involves the gradual breaking down of rock particles as they collide with each other in the water
These collisions round off the rock and reduce the size of them
73
What is solution/corrosion
This process involves the dissolution of soluble minerals in rock due to chemical reactions with water
e.g. Limestone and chalk are particularly susceptible to being dissolved by acidic water
74
What is the role of water depth in determining the impact of waves on cliffs
Important in influencing the amount of energy a wave will have, the deeper the water, a wave is more likely to have more energy for more erosion
Less cliff erosion will occur if the depth of water is greater than the depth of the incoming wave
If the water depth and breaking wave depth are equal than the wave energy is directed at the cliff foot and erosion occurs
75
How does Wave quarrying affect rate of coastal erosion
The impact on rocks of the sheet force of the water itself
This can exert enormous pressure upon a rock surface, thus weakening it
76
How can human activity affect the rate of coastal erosion
-People may remove protective materials from beaches which can lead to more erosion
-Humans can prevent the rate of coastal erosion using hard/soft engineering strategies to do so
77
How can hydraulic action affect the rate of coastal erosion
A Breaking wave traps air as it hits a cliff face
The force of water compresses this air into any gap in the rock face, creating enormous pressure
78
How can attrition impact the rate of coastal erosion
The rocks in the sea which carry out abrasion are slowly worn down into smaller and more rounded pieces.
79
How does abrasion affect the rate of coastal erosion
-Material the sea has picked up
-Sand, Shingle and boulders hurled against a cliff will do enormous damage
80
How does solution affect the rate of coastal erosion
A form of weathering not erosion, but contributes to coastal erosion
Process involves the dissolving of calcium based rocks e.g. Limestone
81
How does the fetch affect the rate of coastal erosion
How far the wave has travelled determines how much energy has been generated within it.
82
How does sea depth affect the rate of coastal erosion
A steeply-shelving seabed at the coast will create higher an steeper waves
83
How does the presence of a beach affect the rate of coastal erosion
-Beaches absorb wave energy and can therefore provide protection gains marine erosion
-Steep, narrow beaches easily dissipate the energy from flatter waves
-Flatter, wider beaches spread out the incoming wave energy and are best at dissipating high and rapid energy inputs
84
What does lithology mean
Refers to the characteristics of rocks such as resistance to erosion and permeability
85
What is differential erosion
The term used to refer to variations in the rates at which rocks wear away
86
Example of how does the structure of rock affect erosion
-bedding planes, joints
-When rocks lie parallel to the coast, they produce a very different type of coastline to when rocks lie perpendicular
87
What is a concordant coastline
A coastline that has the rocks running parallel to it
88
What is a discordant coastline
Rocks run at a right angle to the direction of the coast, allowing the sea to penetrate along the weaker clays to produce large bays
89
Rock dip as a factor of affecting erosion
The steepest cliffs tend to form in rocks that have horizontal strata or which dip gently inland
-Rocks that dip towards the coast tend to produce more gently sloping features
90
What is meant by rock dip?
The angle and direction that titled strata incline compared to the horizontal plane
91
What are six factors which make up a rock’s lithology
Strata
bedding planes
Joints
Folds
Dip
Faults
92
What is meant by strata
Layers of rock
93
What are bedding planes
Horizontal, natural breaks in the strata
94
What are joints
Vertical fractures caused by contractions as sediment dries out
95
What are folds
Formed by pressure during tectonic activity, which makes rock buckle and crumble
96
Transportation methods
Saltation
Traction
Suspension
Solution
Longshore drift
Surface Creep
97
What is saltation
Small stones bounce or leapfrog along the sea bed and beach.
This process is associated with relatively high energy conditions
98
What is traction
Large stones and boulders are rolled and slid along the sea bed and beach by moving seawater
99
What is suspension
Very small particles of sand and slit are carried along by the moving water
Such material is not only carried but picked up, mainly by turbulence that exists in the water
100
What is solution
Dissolved materials are transported within the mass of moving water
101
What is longshore drift
Longshore drift occurs when waves approach the shore at an angle and material is pushed up the beach by the slash in the same direction as the wave approach
102
Types of Deposition
Aeolian deposition
Marine Deposition
103
Marine deposition
Takes place where the waves are low energy or where rapid coastal erosion provides an abundant supply of material
A decrease in the velocity of water causes material to be deposited
104
Aeolian deposition
Refers to the transport and deposition of sediment by the wind
Wind plays an important role in shaping many coastlines and is an almost constant feature of most, due to prevailing winds
105
What are sub-aerial processes
Includes processes that slowly break down the coastline, weaken the underlying rocks and allow sudden movement or erosion to happen more easily, driven by atmospheric conditions rather than the sea
106
Main Sub-aerial processes
Weathering
Mass Movement
Run-off
107
Mechanical/Physical weathering
These processes occur at coasts depending on the nature of their climate
In places above and below freezing, freeze-thaw weathering occurs often
108
Biological Weathering
Includes processes that lead to the breakdown of rocks by the action of vegetation and coastal organisms
Quite an active process on coastlines
109
Chemical Weathering
Common on coasts as it occurs where rocks are exposed to air
Solution is the main chemical weathering process
Other processes include: Oxidation, hydration, carbonation
110
Freeze-thaw weathering
-Water enters the cracks in the rocks then freezes as temperatures remain below 0C
-As it freezes the water expands by almost 10%
The ice occupies more space and therefore exerts more pressure on the surrounding rock
eventually breaking the rock
111
Types of Mass Movement
-Rockfalls
-Toppling
-Wedge failure
-Mudslide
-Rotational slides
-Mudflow
112
What are rockfalls
the rapid, sudden movement of rock fragments falling vertically down a steep slope or cliff under the force of gravity
113
What is toppling
Topples occur on hard-rock cliffs with a joint structure producing columns in the rock
114
What is wedge failure
Hard-rock cliffs with a diagonal jointing pattern
115
What is landslide
Occurs on cliffs made from softer rocks or deposited material, which slip as a result of failure within it when lubricated
116
What is a mudslide
Involves earth and mud flowing downhill, usually over unconsolidated bedrock such as clay when large amounts of water saturates it, causing it to lose cohesion and flow downslope
117
What is slumping
A slump differs from a landslide in that its slide surface is curved rather than flat
Often occurs in weak and unconsolidated clays and sands, often when permeable rock overlies impermeable rock
118
What is soil creep
Soil creep is an extremely slow form of movement of individual soil particles downhill
119
Runoff as a form of mass movement
Good link between water cycle and coastal systems
When overland flow occurs down a slope or cliff face, small particles are moved downslope to enter the littoral zone, potentially forming an input into the sediment cell
120
Difference between aerial and sub-aerial processes
Aerial is processes driven just by wind
Sub-aerial processes are driven by atmospheric conditions above sea level, such as weathering
121
What cliff profile does sub-aerial processes create
A low-angled slope on the cliff
122
When marine processes are more effective than sub-aerial what cliff profile is created
The cliff edge will be much steeper with a wave-cut north on the cliff
123
What cliff profile is formed when subaerial processes and marine processes are in balance
Episodes of marine undercutting and cliff collapse alternative over time forming a beach
124
Examples of resistant rock
Granite, Basalt
125
Examples of less resistant rock
Clay, Shale, sandstone
126
Characteristics of discordant vs concordant coastlines
Discordant: Alternate bands of more and less resistant geology
Concordant: Geology runs parallel to the coastline
127
Landforms associated with Discordant vs Concordant coastlines
Discordant : Bays and Headlands, caves, arch, stack, stump beaches
128
Types of erosional Landforms
Headlands and bays
Caves,Arches,Stacks,Stumps sequence
Wave cut platforms
Blowholes
129
Formation of a crack
Develops along lines of weakness in a headland (Joints or faults)
Processes such as hydraulic action and abrasion occurring
Influencing factors are rock type, wave energy and geology
130
Formation of a Cave
Cracks widen into sea caves as erosion continues by erosional processes such as HA, abrasion
Influencing factors are Tidal Range, Wave refraction, Rock Strata
131
Formation of an Arch
If caves form on both sides of a headland and erode through an arch is created
132
Formation of a stack
The roof of the arch collapses forming an isolated column of rock
Erosional processes such as HA and abrasion attack the base of the new stack
Influencing factors:
Weathering - weakens the structure of arch
Wave direction and energy
133
Formation of a stump
-The stack collapses or is worn down into a low-lying stump
-Erosional processes occurring are abrasion and HA, especially at the base
134
Formation of a Wave-cut platform brief notes
Marine erosion attacks the base of cliff
Wave cut notch deepens and cliff collapses
Cliff retreat and platform exposure
Negative feedback loop eventually occurs
135
Step through marine erosion attack cliff forming wave-cut platform
Marine erosion attacks the base of the cliff
Waves focus erosion attack the high-tide line, forming a wave-cut notch
Processes such as HA, abrasion and solution occur eroding the cliff base
Influencing factors are destructive waves, rock type, and resistance and tidal range
136
Step through formation of wave-cut platform when wave-cut notch collapses and cliff collapses
-Continues erosion undercuts the cliff base, forming a notch
Overhanging rock becomes unstable and collapses due to gravity
Erosional processes that form notch are persistent e.g. HA and abrasion
Factors influencing cliff collapse : Weathering, heavy rainfall can add weight and lubricate bedding planes
137
Step through process of cliff retreat and platform exposure when a wave cut platform is being formed
-As collapse occurs, the cliff retreats inland, leaving behind a flat, rocky platform known as a wave-cut platform
-The platform is smooth by abrasion during high tides and storm events
-Negative feedback loop occurs
138
Negative feedback loop associated with wave-cut platform formation
As the platform widens = Wave energy is then dissipated before it reaches the cliff = reduces further erosion = nullifying the cliff retreat over time
139
Formation of blowholes
-A crack or sea cave is developed formed by erosion along a joint, fault or weakness in the cliff often at the base
-Vertical erosion occurs upwards, HA and abrasion enlarge the cave
-Vertical shaft may form upwards towards the top of the cliff
-When the shaft breaches the cliff top, a blowhole is created
140
Erosional processes that create blowholes
-Hydraulic action - air compressed in cave forces fractures
-Abrasion - Expands the cave and vertical shaft
-Solution - May assist in Limestone or Chalk cliffs
141
What occurs at a blowhole
During high tides or storms, pressurised water and air are forced out the top like a jet-like spray
142
Formation of headlands and bays
Alternating bands of hard and soft rock lie perpendicular to the coast (discordant coastline)
Differential erosion begins as soft rode erodes faster than hard rock
The soft rock retreats, forming a bay, forming low energy environments
Hard rock remains as prominent protrusions, exposed to more wave energy, become focal point for erosion
143
Processes that help form headlands and bays
-Hydraulic action and abrasion dominated on headlands
-Solution can affect limestone headlands
-Attrition breaks down sediment in bays
144
Feedback loops at headlands and bays
Positive feedback: Headlands erode faster due to concentrated energy = amplifies contrast between headlands and bays
Negative feedback: Bays accumulate sediment (beaches) which dissipates wave energy, slowing erosion down within the bay
145
Factors/Processes in development of landform
-Fetch
-Rock type
-Depth of water and wave depth
-Geology (softer or harder rock)
-Wave energy
-Wind speed
-Deposition
-Concordant/Discordant coastline
146
How may headlands and bays change temporally?
-Less biological weathering in the winter, however possible more severe rainfall and storms causing destructive waves
-Higher rates of erosion from May to October
147
How may caves,arches and stacks change temporally?
Winter: More intense storms and larger waves increase erosion rates speeding up the sequence
Summer: Calmer, Constructive waves may deposit sediment, slowing erosion.
More biological growth, can cause more biological weathering but also offer some protection to cave walls.
Long term: Cave can become arch, becomes stack which becomes stump etc
Climate change and sea level rise may submerge caves or increase erosion intensity
148
What is Wave Refraction?
The process by which waves turn and lose energy around a headland on uneven coastlines.
The wave energy is focused on the headlands, creating erosive features in these areas.
149
Where is Ballard Down?
South Coast of England in Dorset
150
Characteristics of ballard down
The headland faces different wave regimes on either side caused by tidal influence .
South-side wave more exposed to high erosion
151
Cliff Profiles of Ballard down
The northern and southern sides show different profiles due to structural orientation and wave exposure
Southern cliffs are more exposed and steeper, northern cliffs are more stable with less erosion due to gentler wave action
152
Coastal features of Ballard Down
At Handfast point, the chalk has been eroded to form a cave-arch-stack-stump sequence, including Old Harry Rocks
153
What influenced Old Harry Rocks to have its features
The presence of vertical joints and the strength of the chalk
154
Subaerial processes affecting ballard Down
Weathering, Particularly along joints and bedding planes
155
How does Ballard Down’s geographical structure affect it?
The chalk dips northward, with the presence of vertical joints that allow marine erosion to exploit weaknesses and form caves and arches
156
How does wave energy and direction affect Ballard Down
The variation in wave energy between the north and south sides plays a significant role in shaping the coastline
Sea level and storm events also influence erosion and deposition patterns
157
What is the spatial variation between Ballard Down and other nearby cliffs
-Ballard is made of chalk, more resistant to erosion
-Ballard down has prominent vertical cliffs and classic erosional features such as Old Harry Rocks, nearby cliffs (Swanage bay) are more gently sloped with less dramatic landforms
-Ballard Down is a protected national trust area so has less human activity affecting its landforms
158
Factors affecting type of transportation
Velocity and particle size (mass)
159
In low energy environments, what is likely to be transported
Only the finest particles (clays) will be transported
160
In high energy environments, what is more likely to be transported
Larger particles
161
Why is longshore drift important
It is responsible for moving vast amounts of sediment along the coastline and eventually out to sea
162
What can interrupt the process of longshore drift
Human management strategies
163
What can be impacts elsewhere if longshore drift is interrupted (spatial change)
Other natural patterns can be distorted, depriving other beaches of material
164
Deposition takes place when
The velocity of the water falls below a critical value for a particular size of particle and can no longer be transported
165
Examples of depositional landforms
Barrier beaches
Sand Dunes
Spits
Estuarine Mudflat
Offshore bars
Tombolos
166
When do beaches form
When constructive waves deposit sediment on the shore, they are a store in a coastal system
167
Characteristics of a shingle beach
Steep and narrow, because they are made up of larger particles and pile up at steeper angles
168
Characteristics of a sand beach
Wide and flat as they are made up of smaller particles
169
Beach definition
A depositional landform extending from approximately the highest high tide to the lowest low tide
170
What does accretion mean
The gradual build-up of land through the deposition of sediment over time
171
Swash-aligned vs Drift-aligned beaches
Swash aligned beaches will be less wide, as the sediment is only transferred up and down the beach
-Forms headlands and bays if discordant
Drift aligned beaches will have formed from sediment being transferred along the coastline by longshore drift
-Can form landforms such as spits
172
Are spits formed at swash or drift aligned beaches
Drift aligned beaches
173
Fetch and prevailing winds role in forming a spit
Prevailing winds causes waves to come at an angled approach, longshore drift occurs forming a drift aligned beach
Secondary winds can form a recurved spit
Fetch provides energy for longshore drift
174
Why can some spits be curved
Due to secondary winds coming in at a different angle to initial prevailing winds
175
Characteristics of a spit
-Made of sand, shingle or gravel
-Formed by deposition
Found in low energy environments
Often have salt marshes
One end is connected to land
176
Temporal change at a spit
-May change shape over time
-Can break off or shorten
-Can eventually develop into a salt marsh
177
What is a tombolo
A beach that has formed between a small island and the mainland, deposition occurs where waves lose their energy and the tombolo begins to build up
178
Processes creating a tombolo
Deposition and wave refraction as they bend around an offshore island
179
Characteristics of a tombolo
Composed of sand or shingle
-Formed in sheltered, low energy zones behind islands
-Connects land masses
180
Temporal change at a tombolo
-Can become wider or higher with continued deposition
-may become permanent if vegetation stabilises it
-May break apart if sediment supply is interrupted
181
What are offshore bars
They are submerged ridges of sand or sediment created by waves offshore from the coast
Parallel to the coastline.
182
How are offshore bars formed
Destructive waves erode sand rom the beach with their strong backwash and deposit it offshore
Offshore bars act as sediment sinks and as sediment input stores
They can also absorb wave energy reducing the impact of waves on the coastline
183
Difference betweeen bars and offshore bars
-Bars are created when longshore drift deposits sediment across a bay, whereas offshore bars are formed by wave action removing sediment from beaches and transported offshore
-Offshore bars are submerged ridges of sand, whereas a bar is a narrow strip of sand or shingle that joins two headlands together
184
Exposure of bars vs offshore bars
-Bars are usually above sea level and visible
Offshore bars are often submerged and only visible at low tide
185
Definition of sand dunes
Accumulations of sand shaped by the wind (aeolian processes), typically found at the back of beaches above the high tide line
They are a key depositional landform in the coastal system and an example of dynamic equilibrium
186
Conditions required for dune formation
Large supply of sand - typically from a wide beach exposed at low tide
Strong on-shore winds to move sand inland
An obstacle to trap moving sand
Dry sand so it can be transported by wind
A gentle beach gradient allowing sand to dry out
187
Formation process of sand dunes
-Sand is blown in land and trapped by an obstacle, forming embryo dunes
-Overtime, these grow and are colonised by pioneer species
-These plants help grow and stabilises the dune and add organic matter, allowing more species to grow
-This leads to a successional sequence known as a psammosere
188
Types of Dunes
Embryo dunes
Fore dunes
Grey dunes
Dune slacks
mature dunes
189
Embryo dunes
First to form in the sequence
Often no more than a metre high
Very alkaline due to shell fragments
Pioneer species
tolerates high salinity and lack of moisture
190
Fore Dunes
Form behind embryo dunes
Up to 5 m high
Appear as yellow due to limited organic material
Marram grass dominates
191
Grey Dunes
located behind yellow dunes
More stable, less mobile due to plant cover
Soil begins to form from decaying marram and other plants
192
Dune Slacks
Found in low areas between dune ridges
Water table is close to or at the surface creating damp conditions
Supports moisture reliant plants e.g. marsh orchids
High biodiversity and critical for certain species
193
Mature Dunes
Farthest inland
Fully developed soil profile, rich in humus and nutrients
supports climax community of plants
vegetation such as bramble and heathland
Final stage of psammosere succession
194
Short term imprortance of vegetation on dunes
Pioneer species will colonise embryo dunes e..g. marram grass, and will enable vegetation to grow and to stabilise the dune
Deep roots bind sand, reducing wind erosion allowing more sand to accumulate
195
Long term importance of vegetation on dunes
Soil fertility improves as move down the psammosere succession
more species are able to grow and develop
Dunes increase in height and stability over the years thanks to vegetation
196
Where are mudflats/ salt marshes found
Found in sheltered, low-energy estuarine environments behind spits or in river estuaries
197
Why are river estuaries important
Important sediment stores where huge quantities of river sediment is deposited in water sloe to the edges
198
How can mudflats form at river estuaries
Rising rides create a buffer to the river flow, slowing velocity and leading to considerable deposition
Most of the sediment that accumulates here is mud q
199
What is a salt marsh
Areas of flat, silty sediments that accumulate around estuaries or lagoons
Mudflats form, and over time they can develop into salt marshes
200
What environments do salt marshes form
In sheltered areas where deposition occurs
Where salt and freshwater meet
Where there are no strong tides or currents to prevent sediment deposition and accumulation
201
Process of mudflat becoming a salt marsh
As mudflats develop, salt -tolerant plants begin to colonise and stabilise them
Halophytes (salt-tolerant species) helps to slow tidal flow and trap more mud and slit
As sediment accumulates, the surface becomes drier and different plants begin to colonise
Creeks created by water flowing across the estuary at low tide divide up the salt marsh
202
What are the two main causes of sea level change
Eustatic change - when the sea level itself rises or falls
Isostatic change - when the land rises or falls, relative to the sea
203
Typical sequence of sea level rise to relflect retreat of ice examples
Eustatic Change
Eustatic change - Caused by change in the volume of water in the sea
Temperature rises, causing ice caps to melt increasing the volume of sea level
Temperature down = more precipitation as snow = volume of water stored in glaciers increases
Also, when temperatures rise, thermal expansion occurs causing water to expand and sea levels to rise
204
Sea level rise sequence and retreat of arctic ice for isostatic change
Glacial periods means that land is uplifted relative to the sea
Uplift or depression of the earth’s crust caused by ice sheets can change sea levels locally
Land shrinkage after abstraction of grand water can cause local sea levels to fall
205
What scales do Eustatic and Isostatic change occur
Eustatic = global scale
Isostatic = local scale
206
What occurs at the end of a glacial period regarding isostatic change
As the ice begins to melt at the end of a glacial period, isostatic change begins to occur
207
How has sea level changed in the last 100000 years
11-12k years ago water stored in ice sheets
Glacial period 20k years ago estimated to be 120-130m below current sea levels
208
Example of sea level change due to tectonic activity
2004 earthquake around 9 on RS caused a tsunami, raising of the seabed which increased sea level in Indian Ocean by 0.1mm
209
How can tectonic activity raise sea levels
Tectonic activity such as earthquakes can have knock on effects, causing a tsunami which can permanently raise the seabed and reduce the capacity of the sea.
210
Explain the features of global sea level changes
Features such as eustatic change alter sea levels
Typically occurs when temperatures rise causing ice caps to melt globally, decreasing cryospheric storage of water, increasing hydrosphere store (sea) causing the volume of water in oceans to increase.
Thermal expansion another feature as it is a result of global temperatures rising due to climate change
211
What are fjords
Flooded glacial valleys
These are usually quite deep and fill the previous u-shaped valley
212
What is a Rias
Flooded upland river valleys
Common features of the South West coast of the UK
213
What is a dalmatian coast
A submerged, concordant coastline formed when rising sea levels flood a folded landscape
This causes long,narrow islands to run parallel to the coast
214
How are submergent features created
-Rias created by rising sea levels
-The floodplain of a river will vanish beneath the rising waters
215
where are fjords often found
On the coasts of Norway, South Western New Zealand
216
Examples of submergent landforms
Rias - drowned river valleys
Dalmatian Coasts - long narrow islands parallel to the coast
Fjords - Drowned glacial troughs
-Estuaries - flooded river mouths
217
Examples of emergent landforms
-Raised beaches - present day high tide level reduces so beach raises relative to sea level
-Raised wave-cut platforms - present day high tide level no longer erodes the wave-cut notch
218
What is coastalisation
The process by which the coast is being developed and people are moving to the coast, increasing the number of people at risk from marine relative environmental activity
219
What is storm surge
A result of the low pressure created by large weather events such as tropical storms
Raises the sea level and therefore poses a significant flooding risk
220
How is risk of storm surge exacerbated on coastlines
Removing natural vegetation e.g. Removal of mangrove forests will reduce amount of trapped sediment, reducing accretion and less protection on communities from storm surge
Global warming, as surface of oceans get warmer, it is predicted that the frequency and intensity of storms will increase, so storm surge and flooding also expected to increase
221
How many people in the world live on the coast and are at risk of coastal flooding
More than 1 billion people
222
Evidence of contemporary sea level change
From late 19th century to the late 20th century sea levels globally rising by 1.7mm per year
223
What is contemporary sea level change
Refers to changes in global sea levels that are ongoing and have happened recently
224
Causes of contemporary sea level change
-Sea level rise is the result mainly of thermal expansion of water, melting of freshwater ice in Greenland and Antarctic ice sheets
225
Impacts of contemporary sea level change
-Significantly reduced house and land prices leading to economic loss for homeowners and local coastal economies
-Storm surges = removes natural vegetation and climate change exacerbates this
-Higher mean sea levels could have impact on underground water resources
226
How do impacts of contemporary sea level change vary
Exposure and geography of location being impacted
Protection of area
Population density
227
Impact of climate change in Kiribati
Sea level is rising by 4X the global average per year
Predicted that many of its islands could disappear under the sea in the next 50 years
228
What is next for Kiribati
President has purchased one of the islands of Fiji, so when the islands are submerged, Kiribati’s population will become environmental refugees and move there
229
Environmental impacts to Kiribati
ST: More frequent coastal flooding
Saltwater intrusion into freshwater
LT: Progressive shoreline retreat and permanent land submergence
Ecosystem degradation
230
How will sea level change influence groundwater sites in Kiribati
It was cause salinisation
231
Social Impacts of contemporary sea level change in Kiribati
ST: Water insecurity - more households reliant on imported/ bottled water
Public health risks
Damage to homes and schools close to the shore
LT: Loss of place and identity
-Inequality widens regionally and globally
232
Economic Impacts of contemporary sea level change in Kiribati
St: Rising adaptation and maintenance costs
Pressure on fishing and agriculture
LT: Loss of productive land and infrastructure corridors
A Level Geography
flashcards
Decks in class (27)
# Cards
-
Global Systems and Governance151
-
The water cycle90
-
River Exe Case Study River Catchment at a Local Scale18
-
The Carbon Cycle70
-
Case study of a tropical rainfroest - water and carbon cycle31
-
Local Place Study - Reigate25
-
Changing Places36
-
Local Place study - Reigate28
-
Distant Place Study - Dubai24
-
Coasts :/232
-
Contrasting coastline beyond the UK - The Sundarbans, Bangladesh10
-
Coastal Management and Local Place Study45
-
Population and the Environment - Booklet 1 Introduction51
-
Population and Environment - Booklet 2 Agriculture148
-
Population and Environment - Booklet 3 Environment, Health & Wellbeing74
-
Population and Environment - Booklet 5, China Case Study of Population Change38
-
Population and Environment Booklet 6 - Principles of Population Ecology41
-
Global Systems Booklet 5 - The ‘Global Commons’ and Antarctica as a global common96
-
Hazards Booklet 4a and 4b - Seismic Hazards and Christchurch18
-
Hazards Booklet 1 - The concept of hazard in a geographical context88
-
Population and Environmnet Booklet 3b : Local Case Study - Blackpool18
-
Hazards Booklet 2 - Plate Tectonics57
-
Hazards booklet 3 - Volcanic hazards37
-
Volcanic hazards Case Studies37
-
Population and the Environmnet Booklet 4a: Population Change43
-
Populatioon and the Environment Booklet 4b: International migration14
-
Population and the environment Booklet 7: Global population futures41
