Coasts Flashcards
Describe the essential features of the backshore
- the part of the beach closest to the coastline
- dry under normal conditions
- berms (horizontal plateau formed from deposition) without vegetation
- only exposed to waves during storms
Describe the essential features of the nearshore
- where waves steepen and break and surge out to foreshore
- sediment is transported in this zone
Suggest three different criteria that might be use din classifying coasts
- geology
- sea level rise/fall
- deposition
What are subaerial processes
- land based processes which later the shape of the coastline
- weathering (e.g. Freeze thaw, chemical weathering)
- mass movement (e.g. Landslides, slumping)
Describe the essential features of the coastal plain
- flat low lying land adjacent to the sea
- cliff/wave cut notch
- gets flooded during storms
Contrast the profiles of 2 high relief cliffs - one whihc is being actively eroded and the other not
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What is the difference between a concordant coast and a discordant coast
- concordant when the arrangement of the rocks are parallel to the coastline
- discordant when arrangement is perpendicular to coastline
Name and example of a concordant and discordant coast
- concordant eastern coast of Adriatic Sea
- discordant south west Ireland
Explain what a haff coastline is
- a lowland coast where the long bars and lagoons are parallel to the shore
Headlands and bays are a feature of discordant coasts, explain why marine processes gradually smooth out such coasts
- resistant rocks form headlands meaning the shape of the coastline causes waves to refract as they approach headlands
- concentrates energy on headlands, increasing rate of erosion
- allowing coast to flatten out.
Examine the influence of dip on cliff profiles
- the dip of a rock layer is the angle of tilt from the horizontal.
- if a rock layer dips towards sea the blocks of rock may slide under the influence of gravity (mass movement)
- if the angle of the dip is landward, weathering and erosion may attack exposed bedding planes and joints, creating an irregular profile
What are the micro features of a cliff and how are they formed
- cliff profiles may include many protrusions and indentations due to erosion, as well as miro features such as caves, blowholes and geos
Characteristics of igneous rocks
- cooled magma (granite and basalt)
- more resistant to marine erosion and weathering than sedimentary rock.
Features of metamorphic rocks
- gneiss, marble
- formed from igneous and sedimentary rocks that were subjected to intense heat and pressure
- most resistant rock
Features of sedimentary rocks
- formed underneath oceans (limestone, sandstone)
- least resistant rocks
Describe how the differential erosion of alternating and contrasting rocks affects the coastline
- sedimentary rocks are permeable whereas metamorphic rocks are impermeable.
- the presence of water in these rocks can affect weathering and mass movement e.g. Slumping due to saturation
- some rocks such as limestone contain soluble minerals and so are vulnerable to chemical weathering such as carbonation (sea water absorbs co2 which splashes onto limestone and dissolves it)
Explain why vegetation is a a factor affecting coastal recession
- stabilises soft sediment low energy coastlines based on sand and mud.
- plant succession over time pioneer plants colonising bare areas as they change the conditions of soil by adding humus (decayed vegetation), retaining moisture and stabilising loose ground.
- sand dunes, where xerophyte plants such as marram grass grow, and salt marshes where halophyte plants such as glasswort grow provide buffer zones between and and sea. Sand dunes take the impact of storms and salt marshes absorb coastal flooding.
Explain why estuaries are ideal for the development of salt marshes
- estuaries are low energy environments where tidal conditions bring seawater and sediments in and out and rivers bring fine MUDs and silts and deposit them at the estuary
- the clay particles sick to one another (flocculation) and once deposited are colonised by algae.
- salt marshes can then be found at the edges of estuaries.
Explain the formation of embryo dunes
- sand dunes form where there is a plentiful supply of sand and a large area for it to dry out.
- onshore winds blow sand towards land and obstacles such as vegetation and shingle ridges which trap the sand
- embryo dunes are formed first.
Explain the formation of dune slacks
- at high tide or under storm conditions, seawater may reach the dips in the sand dunes, called dune slacks.
- this allows other plants such as march orchids to grow.
Apart form colour what distinguishes yellow dunes from grey dunes
- yellow dunes tend to be the highest, and may form a ridge near the dune front with marram grass.
- grey dunes are known as the mature dunes because their humus (decayed vegetation) content is greater. The clima vegetation is either pine forest (high acidity) or oak forest (slightly neutral).
Why is marram grass so important to the formation of sand dunes
- able to colonise the stable dunes and help hold the sand together and trap more sand.
What is the difference between tides and currents
- tides are driven by the gravitational force of the moon, water moving up and down the beach over a period of time
- current is the motion of the water, caused by density difference in water masses, cohesive streams that flow through the water
Describe what happens to waves when they reach shallow water
- forward movement starts to occur when the depth is less than the wavelength
- the base of the wave is slowed down by friction against the sea floor while the top of the wave rushes ahead
- the wave crest topples over and breaks onto the shore.
Distinguish between constructive waves and destructive waves
- constructive, larger swash than backwash, build up the beach
- destructive strong backwash weak swash, remove sediment
What is the difference between hydraulic action and corrosion
- hydraulic action is where a destructive wave breaks onto a cliff and the force of the water exerts pressure into cracks and joints which cause the rock to weaken
- corrosion is where seawater and salt spray react with rock minerals and actively dissolve them, rock minerals are then carried away in solution in sea water
Name two other marine erosion processes other than hydraulic action and corrosion
- abrasion, destructive waves pick up particles of sand and pebbles and scrape or throw them against a cliff as they break, this scratches the rock wearing it away, results in undercutting a cliff at high tide level.
- attrition occurs when boulders are continually moved around by waves especially in the breaker zone, as the sediment moves they collide with each other, rocks are broken down into smaller pieces.
Describe the suite of coastal landforms most commonly found in areas of sedimentary rock with defined bedding planes and joints.
- wave cut platform, where a cliff is eroded at its base, leaving the tour rock unsupported which eventually collapses, leading to coastal recession
- cliffs, vertical slopes caused by waves undercutting land at high tide or constantly if there is no beach, as the cliffs undercut gravity causes mass movement in the unsupported rocks.
- caves, arches, stacks and stumps
Headlands in the sea cause waves to be refracted and all wave energy to be focused on the sides of the headland, hydraulic action and abrasion will at first form caves which often meet from opposite sides to form a tunnel above which is a rock arch - eventually the top collapses leaving a pillar of rock called a stack, the stack continues to be eroded cutting notches all around leaving it unstable causing it to collapse leaving the base which is called a stump.
Name and describe the 4 sediment transportation processes
- suspension, small particles carried in the water e.g. Silts and clay, currents pick up large amounts during a storm.
- solution, minerals are dissolved in sea water and carried in solution, load comes from cliffs made form chalk/limestone.
- saltation, load is bounced along the sea bed e.g. Small pieces of shingle or large sand grains
- traction, pebbles and large sediment are rolled along the sea bed
What is longshore drift
- the movement of material along a coast by waves which approach at an angle to the shore but recede directly away from it.
Describe how a tombolo is formed
- tombolo is formed after longshore drift carries sediments cross a gap between the mainland and an island forming a narrow low ridge of sand and pebbles
- it may be a spit at first but when deposition links the island no mainland together it is a tombolo
- the isle of Portland in Dorset is joined to the mainland by a tombolo
Explain how a recurred spit is formed
- longshore drift moves sediment along the coast over a long period of time, when the sediments reach a gap in the coastline they are carried for a short while in the same direction until they are deposited on the seabed.
- over time this material is deposited causing it to real through the surface of the sea to form a narrow strip of land across the bay or estuary.
Describe how cuspate foreland is formed
- cuspate foreland is a low lying headland, formed when significant longshore drift is from opposite directions along the coast, sediment is deposited across a bay from both directions forming two spits
- the two spits converge and shelter the area behind in the bay, salt marshes form and enough deposition will form low lying land.
Examine the factors affecting the stability of depositional features
- geology
- type of waves (destructive/constructive)
- wave refraction
- protection against wave action
What are sediment or littoral cells
- a sediment cell is a closed system length of coastline
Describe the three types of weathering
- mechanical, physical factors e.g. Freeze thaw, salt crystallisation
- chemical, the erosion of rocks caused by chemical reactions, e.g. Oxidation
- biological, erosion of rocks by plants animals and microbes, e.g. Seaweed acids, boring molluscs
What is mass movement
- the movement downslope of rocks, sand, clay or soil caused by gravity once a slope has become unstable.
Describe three different types of mass movement
- landslides, movement of rock or debris down a slope
- rock falls, occur on steep slopes as a cliff face is weathered and rocks are loosened and the cliff is unsupported
- slumping, where unconsolidated sands and clays on a cliff remains intact as it moves down a cliff along a curved plane.
Describe the effects of mass movement on the coastal landscape
- lead to coastal recession
- change profile of cliff e.g. Slumping - curved talus slope
- slumping can create benches and terraces
- rock falls lead to debris gathered at bottom of cliff
What is the link between subaerial processes and rates of coastal recession
- increase in subaerial processes leads to increased rate of coastal recession
- rock falls - wave cut platform leads to unsupported rock whihc falls under gravity
Explain the increase in biological weathering
- recession into land leaves cliff more exposed to plants leading to more biological weathering.
What is the difference between isostatic change and ecstatic change
- eustatic change is change in sea level
- isostatic is change in land level
What could be the cause of an isostatic rise and fall in sea level
- during an ice age, ice on land is kilometres thick, meaning it is very heavy and bale to push land downwards
- because the upper mantle underneath the crust is a soft viscous fluid
- this means areas close to the ice where depressed whereas ares further away were tilted upwards. E.g. Scotland was pushed down but the weight of ice and southern england rose slightly
What type of coastline results from a sea level rise or isostatic sinking
- submergent coastlines
Eustatic rise since the end of the last ice age created drowned landforms called rias, fjords, and fjards - ria
Flooded river valley, during ice age some land areas not covered with ice but had frozen ground, so rivers carved valleys with steep sides, when ice melted sea levels rose and drowned the mouths of these valleys - fjord
Flooded glaciated valley, glaciers eroded u-shaped valleys down to the coast of the time and then after the ice melted, the sea level rose again and flooded into the valley creating a deep water inlet with steep sides. - fjard
Flooded inlet with low rocky banks on either side formed by post glacial drowning of glaciated lowland rocky terrain. - Dalmatian coasts
Feature several linked parallel flooded valleys as a result of submergence, when sea levels rose and flooded the valleys between mountain ridges parallel to the coast
What are the coastal features created by a isostatic rebound
- emergent coastlines
Raised beach, a former beach now above the tide line, features such as rounded pebbles and boulders.
Fossil cliff, near vertical slope initially formed by marine processes but now is inland, erosional landforms such as caves may still be visible.
Explain why it is difficult to predict future sea levels with any accuracy
- because there are many variables e.g. Climate change, temperature, thermal expansion, ice melt, ‘warming period’ earths natural climate cycle.
Describe how tectonic activity can affect sea level
- tectonic plates are constantly moving meaning th e volume of the ocean basins increase/decrease
- when subduction occurs a lot of water gets carried down into the mantle.
How is modern technology helping to measure coastal erosion
- LIDAR light detection and ranging, helps measure coastal erosion
- GPS
List four physical factors that encourage coastal recession
- geology
- marine processes
- subaerial processes
- climate
Explain why dredging can increase coastal erosion
- dredging removes sand and gravel for construction purposes, to deepen entrances to ports or supply sediment for beach nourishment
- deeper water caused by dredging may allow waves to maintain their circular motion and energy closer to the cliff, increasing erosion rates.
Give an example and an explanation of ‘dams that cause coastal erosion’
- dams trap sediment and prevent it reaching the beach leaving the coastline exposed and increasing recession and erosion rates.
Explain how weathering and mass movement contribute to coastal recession
- weathering weakens the rocks found at the coast and allows erosion rates to increase
- mass movement moves sediment to the base of coastal slopes, resulting in cliffs retreating further.
Why do rates of coastal recession vary over time
- wind direction, determines wave direction, dominant wind produces the largest waves which cause most erosion, fetch determines power.
- tides, at high tides waves are more likely to be able to reach the backshore and erode land faster
- weather systems
Seasonal weather, high pressure areas bring calmer conditions and smaller waves, low pressure events causes air to rise rapidly so there are strong waves.
Name two megadeltas which contain large populations
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What is storm surge
- a coastal flood of rising water caused by a low pressure weather system (depression)
Give an example of how coastal topography can contribute to the impact of storm surges
- if a coastline confines and funnels a storm surge into a an area of shallow offshore water, it can increase severity.
- examples are the southern part of the North Sea affecting countries such as the UK and the Netherlands.
Describe what is being done to a named island to reduce the risk of coastal flooding
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Explain why Bangladesh is at risk from sever flooding
- 25% of Bangladesh is less than 1m above sea level
- most of the land forms a delta form 3 main rivers which tend to burst their banks
- meltwater from Himalayas
Summarise four predictions made about the physical impacts of global warming
- rise in sea level due to meltwater and thermal expansion
- extinction of coral reef due to bleaching
- depressions and tropical cyclones will have more energy
- increased extreme sea-level events
Give examples of the economic and social losses resulting from coastal flooding
- economic, costs of repairs and rebuilding, loss of jobs and income, money needed in form of aid.
- social, having to relocate, loss of livelihood, losses of amenity areas
What are the main factors affecting the costs of coastal floods
- land use e.g. Industrial or agricultural
- preparation
- coastal defences
What sort of assessments would be made in an environmental impact assessment (EIA) of a proposed sea defence project
- aesthetics
- impact on habitats
Do you agree that the consequence of coastal flooding are greater in developing countries, explain why
- due to higher value of infrastructure
- more industrial therefore higher value land
- more residents leads to larger social impact
- can halt development and cause tnc’s to locate elsewhere.
Explain what is meant by environmental refugees
- people who have been forced to leave their home due to environmental disruption that affects their quality of life
Give reasons why the island of Tuvalu is likely to be one of the first sources of environmental refugees
- climate change causing rising sea levels will affect the island of Tuvalu
- due to the low lying rice farms which will be flooded preventing locals form making an income
- leading to more environmental refugees
What is involved in a hard engineering approach to coastal management
- sea walls, prevent high water levels moving inland
- rip rap, used as a breakwater
- offshore breakwaters (reefs), reduces wave energy
- gabions, absorb wave energy
Why might some stakeholders object to a hard engineering
- not aesthetically pleasing
- unsustainable, more expensive
Explain what is involved in a soft engineering approach to coastal management
- beach nourishment, builds up the beach using natural sediments
- cliff regrading, creates natural stable slope
- cliff drainage, reduces mass movement
- dune stabilisation, barrier to high sea levels
- managed retreat
Do you agree that a soft engineering approach to coastal management is better than a hard engineering approach? Explain why
- more sustainable
- flooding always going to occur and will get worse
- climate change will cause more severe flooding that hard engineering will not prevent
- reduces social and economic impacts
What is meant by the terms mitigation and adaptation
- mitigation, the action of reducing the severity of something
- adaptation, the process of changing to suit the circumstances
Explain why sustainable coastal management can often lead to local conflicts
- can lead to local people losing land, home, job and sense of community
Explain what is meant by integrated coastal zone management (ICZM)
- aims to bring together economic decision makers such as in tourism, fishing and ports, and different government levels.
- other aims include the conservation of ecosystems for future generations
Identify four different coastal management options
- hold the line
- advance the line
- managed retreat
- do nothing
Name the main factors that are likely to influence the choice of coastal management option
- stakeholders e.g. Local people
- sustainability
- SEE impacts
Illustrate the point that coastal management is most likely to involve decisions that will divide stakeholders into winners and losers
- conflicts will always occur if one groups is prioritised over another. E.g. Local residents and council
Is the need for coastal management any less in the developing world than the developed world
- no, development gap is getting smaller therefore developing countries need sustainable management strategies in order to prepare and prevent future threats when value fo land increases.
Describe the 3 features of a sediment cell
- sources, where sediment is eroded
- transfers, where sediment is transported
- sinks, where sediment is deposited
Examples of the 3 features of sediment cells
- source, erosion of cliffs, subaerial processes, land sediment eroded by rivers.
- transfers, LSD, tides, currents.
- sinks, backshore depositional landforms (sand dunes), foreshore landforms (beaches), offshore sediment (offshore bars)
Explain positive/negative feedback
- neg helps to maintain a balance within the system
- pos tends to change the balance until a new equilibrium is reached.
How are haff coastlines formed
- concordant coastlines
- form in low energy environments
- deposition by onshore winds and low energy waves
- south coast of the Baltic Sea
