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Flashcards

Coastal Environments - A level

Chris R Geography English 93 cards

Cards in this deck (93)

  1. 1Lithology (Rock Type)Hard rocks give rugged landscapes such as Giants Causeway in N. Ireland, whereas Soft Rocks give low flat landscapes like the Nile Delta.
  2. 2Geological StructureConcordant or accordant coastlines occur where the geological strata lie parallel to the coastline. Whereas, discordant coastlines occur where the geological state are at right angles to the shoreline.
  3. 3ProcessesErosional landscapes contain many rapidly retreating cliffs, whereas areas of rapid deposition contain many sand dunes and coastal flats.
  4. 4Sea level changesSea level changes interact with erosional and depositional processes to produce advancing coasts (grow due to deposition or fall in sea level) or a retreating coast (eroding or being drowned by a rise in sea level)
  5. 5Ecosystem typesMangroves, coral, sand dunes, salt marsh, and rocky shores add variety to coastlines.
  6. 6Coastal ZonesThe coastal zone includes all areas from the deep ocean to 60km inland. At the coast, there is the upper beach or backshore, the foreshore and the offshore area. The coastal zone is a dynamic area with inputs and processes from land, sea and atmosphere.
  7. 7Wave, marine and sub-aerial processes.Waves are a medium through which energy is transferred. They are created by the wind blowing across the surface of the sea. Frictional drag increases as the wind speed increases, making the wave bigger. Wave energy depends on the strength of the wind, the length of time the wind has blown and the fetch of the wind.
  8. 8The wave orbitThe wave orbit is the shape of the wave: varying between circular and elliptical. The orbit diameter decreases with depth to a depth roughly equal to wavelength, at which point there is no further movement related to wind energy - this point is called the wave base.
  9. 9Wave defintionsWave fetch: The distance of open water over which a wave has passed.
    Wave crest: Highest point of a wave
    Wave trough: Lowest point of a wave
    Wave height: Distance between trough and crest
  10. 10Wave definitionsWavelength: Distance between one crest/trough and the next
    Swash: Water movement up a beach
    Backwash: Water movement down a beach.
  11. 11Types of breakersSpilling breakers: Associated with gentle beach gradients and steep waves. Characterized by a gradual peaking of the wave until the crest becomes unstable.
  12. 12Types of breakersPlunging breakers: Occur on steeper beaches, with waves of intermediate steepness. Distinguished by the shore-ward face of the wave becoming vertical, curling over, and plunging forward and downward as an intact mass of water.
  13. 13Types of breakersSurging breakers: Found on steep beaches with low steepness waves. In surging breakers the front face and crest of the wave remain relatively smooth and the wave slides directly up the beach without breaking.
  14. 14Waves of translationConstructive waves: Short amplitude and a long wavelength. Low frequency of around 6-8 waves per minute, particularly when these waves advance over a gently shelving sea floor. These waves have been generated far offshore creating a spilling breaker. Produce a strong swash and weak bash meaning they supply new material to beach.
  15. 15Waves of translationDestructive waves: High amplitude and a short wavelength. High frequency of 10-14 waves per minute, resulting in a steeply shelving coastline, where rapid friction and steep circular plunging breakers are formed. Strong backwash and weak swash so they remove material from the beach.
  16. 16Tides and the tidal cycle.Tides are regular movements in the sea's surface caused by the gravitational pull of the moon and sun. When the earth, moon and sun are aligned the gravitation pull is at its greatest creating a Spring tide. Low spring tides occur just after a new moon whereas high spring tides occur after a full moon. When the sun and moon are at a right angle to the earth we experience Neap tides.
  17. 17What influences tides?Size and shape of ocean basins, characteristics of the shoreline, Coriolis forces and meteorological conditions.
  18. 18Tides and the tidal cycleThe difference between high and low tide is called the tidal range. The tidal range varies with distance from the amphidromic point. If the coast is funnelled, a tidal bore is created.
  19. 19Rip CurrentsStrong offshore flows, often occur when breaking waves push water back up the beach face. This piled-up water escapes back out to sea as water seeks its own level. The backwash is relatively uniform along ht beach however if the water can flow out more easily then a rip current can form. Rip currents modify the beach by creating cusps
  20. 20Types of erosionHydraulic action - This is the sheer power of the water as it smashes against the river banks. Air becomes trapped in the cracks of the river bank and bed, and causes the rock to break apart.
    Abrasion - When pebbles grind along the river bank and bed in a sand-papering effect.
    Attrition - When rocks that the river is carrying knock against each other. They break apart to become smaller and more rounded.
  21. 21Types of erosionCavitation: Compression of air in sea-facing joints as waves crash against cliffs can cause seawater to be severely compressed. As the wave recedes the pressure reduces and air comes out of the solution in violent 'fizzing', enlarging fissures within joints.
    Solution - When the water dissolves certain types of rocks, eg limestone.
  22. 22Discordant CoastsOn a discordant coastline, alternating layers of hard and soft rock are perpendicular to the coast. Because the soft rock is exposed, it is eroded faster than the hard rock. This differential erosion creates headlands and bays along discordant coastlines.
  23. 23Concordant CoastsConcordant coasts have alternating layers of hard and soft rock that run parallel to the cost. The hard rock acts as a protective barrier to the softer rock behind it preventing erosion. If the hard rock is breached though, the softer rock is exposed and a cove can form
  24. 24Storm surgesStorm surges are changes in the sea level, caused by intense low-pressure systems and high wind speeds. For every drop in pressure of 10mb, sea water is raised by 10cm. Therefore during tropical cyclones, pressure may drop by 100mb resulting in a sea level rise of 1m!
  25. 25Wave refractionThe depth of water around a coast varies due to a variety of coastal landforms. As a wave approaches the coast its progress is modified due to friction from the seabed, halting the motion of waves. Due to the uneven coastline, waves are refracted so that their energy is concentrated around headlands but reduced around bays. Due to the complexities of coastline shapes, refraction is not always fully achieved resulting in longshore drift.
  26. 26Sub-aerial processesSalt crystallization: Sodium and magnesium compounds expand in joints and cracks by 300% when temperatures fluctuate between 26-28 degrees weakening rock structures.
    Freeze-thaw: When water freezes while trapped in rocks it expands by 10% putting extra pressure on the rock. This cycle repeats until the rock fragments and weakens.
  27. 27Sub-aerial processesBiological weathering: Where living organisms such as molluscs or sea urchins on low-energy coasts physically break up structures.
    Solution weathering: The chemical weathering of calcium carbonate by acidic water, tends to occur in rock pools due to the presence of organisms secreting organic acids.
  28. 28Mass MovementRock falls: Cliff rocks break into smaller pieces and then freefall due to freeze-thaw.
    Soil Creep: Occurs on very gentle slopes due to damp soil moving downhill due to increased mass.
    Landslides: Cliffs made of soft rock will slip when soaked in water due to the rock being lubricated.
  29. 29Mass MovementSlumping: Heavy rainfall makes the rock heavier due to it absorbing the water. Happens on a concave surface.
    Mudflow: Occurs on steep slopes with saturated soil and little vegetation. Lack of vegetation means that there is nothing to bind the soil together, promoting mass wasting. Saturated soil becomes heavier leading to rapid movement of mud.
  30. 30Wave transporationTraction: Grains roll along the sea floor. Weaker currents can transport sands and stronger can transport pebbles and boulders.
    Saltation: Grains hop along the seabed in a skipping motion. Moderate currents transport sand and stronger transport pebbles and gravel.
  31. 31Wave transportationSuspension: Grains are carried by turbulent flow and held up in the water. Moderate currents transport silts and strong transport sands.
    Solution: Particles, invisible to the naked eye are carried in the water's current.
  32. 32Longshore driftThe process is responsible for moving significant amounts of sediment along the coast. Occurs in one direction as dictated by the prevailing wind. The swash moves beach material along the beach and the backwash, under gravity, pulls the material back down the beach at right angles to the coastline.
  33. 33Sediment cells'The coastal sediment system' or 'littoral cell system' is a simplified model that examines coastal processes and patterns ina given area. Each sediment cell is a self-contained cell in which inputs and outputs are balances. There are 11 such cells across the UK.
  34. 34Dynamic equilibriumImporant to littoral cells. The concept states any system is a result of inputs and processes operating within it. Changes to an input. Sediment increase, has a knock on effect on processes such as Longshore drift, and a resulting change in landforms will occur.
  35. 35Wave-cut platformThe base of a cliff is undercut by hydraulic action and abrasion forming a wave-cut notch. The rock face above begins to overhang. As waves attack the base of the cliff the size of the overhang increases until the weight of the rock above can no longer be supported and a section of the cliff collapses. Marine erosion begins again leading to further collapses and gradual retreat inland forming a wave-cut platform.
  36. 36Headlands and baysForm on discordant coastlines. where hard and soft rock run in layers at 90 degrees to the water. Alternating layers of hard and soft rock allow the sea to erode the soft rock faster, forming a bay but leaving hard rock sticking out, known as a headland. A bay begins to develop causing wave refraction around the headlands increasing erosion at the bay.
  37. 37CliffsA cliff is a vertical, near-vertical or sloping wall of rock or sediment that borders the sea. They generally differ in their angle of slope because of their rock structure and geology, but the processes involved in their formation are the same.
    Rocks form in layers of different rock types known as beds that are subject to tectonic forces that tilt and deform them. Angle the bed dips affects how they erode and the profile of the resulting cliff.
  38. 38CliffsMany cliffs are composed of more than one rock type - these are known as Composite Cliffs. The exact shape and form of the cliff will depend on such factors as the strength and structure of the rock, relative hardness and nature of the waves involved.
  39. 39BeachesThe term beach refers to the accumulation of material deposited between high and low tidal limits, which shelves downwards towards the sea. A beach has three zones; backshore, foreshore and offshore.
  40. 40BackshoreA cliff marked by a line of sand dunes. Above and at HWM there may be a shingle/storm ridge which is an area of coarse material pushed up the beach by spring tides. Often a series of smaller ridged formed beneath the storm ridge known as berms which are build-ups of finer material that mark the successive high tides. Edge of berm is often irregular due to creation of beach cusps which are semi-circular depressions.
  41. 41ForeshoreExposed at low tide. Ridges and runnels form parallel to the shore line in the foreshore zone. Ridges are areas of the foreshore that are raised above the adjacent shore which dips into a Runnel. Ridge and runnel systems are formed due to the interaction of tides, currents, sediments and the beach topography. They only form on beaches with a shallow gradient. They form as a simple drainage route for tides.
  42. 42OffshoreWhere the first material is deposited. In this zone, the waves touch the seabed and so the material is usually disturbed, sometimes being pushed up as offshore bars. when the offshore gradient is very shallow.
  43. 43Factors affecting beach formThe form is affected by the size, shape and composition of materials, the tidal range and wave characteristics. Storm waves are more frequent in winter and swell waves more in summer causing beaches to differ in winter and summer profiles. Wave steepness and beach angle. Sediment size affects beach profile through its percolation rate, shingle allow rapid infiltration.
  44. 44Swash aligned coastsProduces where the waves break in line (parallel) with the coast. Swash and backwash movements move material up and down the beach producing many coastal features. Swash-aligned beaches are smoothly curved, concave beaches.
  45. 45Drift aligned coastsProduced where waves break at an angle to the coast. The swash, therefore, occurs at an angle but the backwash runs perpendicular to the beach. As a result, the material is transported along the beach via longshore drift.
  46. 46Spit FormationA spit is a tretch of sand or shinge extending from the mainland out to sea. Develop due to a sudden change in the shape of the coastline such as at a headland due to longshore drift not following the coastline. Sediment is deposited out to sea as the strength of the drift weakens. Refraction around the end of a spit curves it into a hook forming a recurved spit.
  47. 47Bar formationA ridge of material is connected at both ends to the mainland. It is located above sea level. If a spit continues to grow lengthwise, it may ultimately link two headlands to form a bay bar. These are composed either of shingle, as in the case of the Low Bar in Cornwall, or of sand, such as the nebrung of the Baltic coast
  48. 48Barrier IslandsNatural sandy breakwaters form parallel to a flat coastline. By far the world's longest series is that of roughly 300 islands along the East and Southern coasts of the USA. Islands are generally 200-400m wide.
  49. 49TomboloIf a ridge of material links an island with the mainland. this ridge is called a tombolo. An example of this is Chesil Beach on the south coast of England
  50. 50Cuspate forelandsCuspate forelands consist of shingle ridges deposited in a triangular shape, and are the result of two separate spits joining, or the combined effects of two distinct sets of regular storm waves.
  51. 51Sand dunesSand dunes forms where there is a reliable supply of sand, strong onshore winds, a large tidal range and vegetation to trap the sand.
  52. 52Sand dunes - definitionsEmbryo dune = First part of the dune to develop. The stabilisation occurs via marram and Lyme grass which act as traps for sand.
    Yellow dune = Colour is due to lack of humus, but with distance inland, they become increasingly gey due to large amounts of humus
  53. 53Sand dunes - definitionsFixed grey dunes = Limited growth due to distance from the beach, Far more stable.
    Dune stacks = Depressions between dune ridges, which will be damp in summer and water-filled in winter.
    Blowouts = Often evidence of overuse by humans, Large 'holes' that appear in the dunes.
  54. 54Mudfalts and saltmarshesThe intertidal zone - the zone between high and low tide = experiences severe environmental changes in salinity, tidal inundation and sediment composition. Salt accumulated in these situations and on reaching sea level forms mud banks. The appearance of vegetation saltmarshes if formed.
  55. 55Coral reefsCalcium carbonate strucutres, made up of reef-building stone corals. Limited to the depth of light penetration. Occupy less than 0.25% of the marine environment, yet they shelter more than 25% of all known marine life.
  56. 56Development of coralBegin as polyps which attach themselves to a hard surface in shallow seas where there is sufficient light for growth. Exude calcium carbonation forming their skeleton. Polyps have small algae - zooxanthellae, growing inside them. Symbiotic relationship as they feed each other.
  57. 57Rate of growth of Coral reefsTropical reefs grow at rates ranging from less than 2.5cm - 60cm per year, forming huge structures over incredibly long periods of time. 2600km Great Barrier Reef was formed over 5 million years.
  58. 58Factors affecting distribution of coral reefs.Temperature - 23-25 degrees C
    Depth -Less than 25
    Light
    Salinity = 32 psu
    Sediment = No sediment
    Wave action = Strong wave action
    Exposure to air = Below low tide amrk
  59. 59Fringing reefFringe the coast of a landmass. Characterised by an outer reef edge capped by an algal ridge, a broad reef flat and a sand floored 'boat channel' close to the shore. Grow along shores that are protected by barrier reefs.
  60. 60Barrier reefsOccur at greater distances from the shore than fringing reefs and are separated from it by a wide and deep lagoon. Barrier reefs tend to be broader, older and more continuous than fringing reefs. Forms as the oceanic island begin to sink into Earth's crust due to the absence of volcanic island-building forces, added weight of coral and erosion at the surface.
  61. 61Atoll ReefsRise from submerged volcanic foundations and often support small islands of wave-borne detritus. Atoll reefs are essentially indistinguishable in form and species composition from barrier reefs except that they are confined to the flanks of submerged oceanic islands.
  62. 62Patch reefDescribes small circular or irregular reefs that rise from the sea floor or lagoons behind barrier reefs or within atolls.
  63. 63Uses of coral reefsSeafood in LEDCs, New medicines, jewellery, tourism, construction, aquariums, protecting the coast from storms.
  64. 64Human impact on coralOverfishing, destruction of the coastal habitat, and pollution from farms and households.
  65. 65Natural threats to coralDust storms from Sahara have introduced bacteria into Caribbean coral, and global warming causing coral bleaching, and natural disasters.
  66. 66Coral bleachingPollution, sedimentation, global climate change and other natural and anthropogenic pressures threaten the warm, clear water needed for corals causing zooxanthellae to not photosynthesis. When the zooxanthellae dies it causes the coral to lose its colour
  67. 67Climate change, coral and people500 million people depend on coral reefs for food, coastal protection, building materials and income from tourism. Climate change threatens these predominantly poor people, with many living in 80 small developing countries.
  68. 68Sustaining CoralReduction in emissions of greenhouse gases, limiting overfishing, sedimentation, and blasting coral, providing assistance in LEDCs, local coastal management.
  69. 69Sustainable management of coastsHuman pressures on coastal environments create the need for a variety of coastal management strategies. These may be long-term or short-term, sustainable or non-sustainable. Successful management strategies require detailed knowledge of coastal processes. Rising sea levels, more frequent storm activity and continuing coastal development are likely to increase need for coastal managemnet
  70. 70Shoreline management plans (SMPs)1. Do nothing
    2. Maintain existing levels of coastal defence
    3. Improve the coastal defence
    4. Allow retreat of the coast in selected areas.
  71. 71Hard engineering - Sea wallsGiant walls span entire coastlines and attempt to reduce erosion and prevent flooding in the process. Big, ugly and expensive requiring constant maintenance. Produce a strong backwash in waves undercutting the sea wall.
  72. 72Hard engineering - GroynesSoft hard engineering techniques. Low-lying wooden walls that extend out to sea. They capture sand that moves down the beach via longshore drift and help build up a large section of beach in front of an area that's experiencing coastal erosion. Remove lots of sand that are present down-drift of the beach.
  73. 73Hard engineering - GabionsBundles of rocks in a metal mesh. Places at the base of a cliff in an attempt to reduce the impact of waves on the cliff and prevent the cliff from being undercut. Not particularly effective and are unsightly but cheap.
  74. 74Hard engineering - RevetmentsConcrete or wooden slanted structures built along the base of a cliff. Act as a barrier against waves by absorbing the energy of the waves. Can have rippled surfaces to help dissipate the wave energy. Expensive to build but don't require as much maintenance as sea walls.
  75. 75Hard engineering - Riprap/Rock armourRocks and stones are put against the base of a cliff. Similar to gabions in their purpose but they aren't bound together in a mesh. Slightly more appealing as they blend into the environment better but the rocks can be moved by sea.
  76. 76BreakwatersOffshore concrete walls that break incoming waves out at sea so that their erosive power is reduce to next to none when they reach they coast. Effective but can be easily destroyed during a storm and they don't look nice.
  77. 77Soft engineering - Beach nourishmentSand and shingle are added to a beach in order to make it wider. Increasing the distance a wave has to travel to reach the cliffs.
  78. 78Soft engineering - Land managementSand dunes act as a good barrier against coastal flooding and erosion and they can be exploited as a natural defence. Dunes have to be left undisturbed so boardwalks are constructed and sections of sand dune systems are marked out as out of bounds.
  79. 79Soft engineering - Marshland creationUsed to break up waves and reduce their speed, reducing the wave's erosive power. Marshlands also limit the area which waves can reach preventing flooding. Marshlands can be created by encouraging the growth of marshland vegetation.
  80. 80Soft engineering - Beach stabilisationWiden the beach by planting dead trees in the sand to stabilise it and lower the profile of the beach.
  81. 81Isostatic changeIsostatic sea level change is the result of an increase or decrease in the height of the land. When the height of the land increases, the sea level falls and when the height of the land decreases the sea level rises. Isostatic change is a local sea level change whereas eustatic change is a global sea level change.
  82. 82Eustatic changeEustatic change is when the sea level changes due to an alteration in the volume of water in the oceans or, alternatively, a change in the shape of an ocean basin and hence a change in the amount of water the sea can hold. Eustatic change is always a global effect.
  83. 83Submergent landforms - RiaThis is a river valley that’s been flooded by the eustatic rise in sea level. They’re almost exactly like a typical river valley but they have even more water in them. The cross-section of a ria is really similar to the one you’d find for a river in the lower course. One thing to note, the floodplain of the river also gets flooded, altering the cross profile of a ria ever so slightly so that it includes the floodplain.
  84. 84Submergent landforms - FjordThese are steeper and deeper variants of riases that are relatively narrow for their size. They have a u-shaped cross profile and are often found in particularly icy sections of the world. Flooded glacial valleys. In general, fjords are really deep however they have a shallow mouth (known as a threshold) as this is where the glacier deposited its load. Fjords are pretty stunning pieces of scenery, an example of one is Sogne Fjord in Norway which is really big.
  85. 85Emergent coastlines - Raised beachesA raised beach is an emergent coastal landform. Raised beaches and marine terraces are beaches or wave-cut platforms raised above the shoreline by a relative fall in the sea level.
  86. 86Emergent coastlines - Relic cliffsAn old cliff displaying features such. as caves, arches and stacks. Revealed when the sea level lowers.
  87. 87Holderness coast case study.The Holderness Coast is one of Europe’s fastest eroding coastlines. The average annual rate of erosion is around 2 metres per year. The main reason for this is because the bedrock is made up of till (soft clay). This material was deposited by glaciers around 12,000 years ago.
    The coastline stretches along the coast of the East Riding of Yorkshire, known as Holderness, from Flamborough Head in the North, to Spurn Head in the south. Since Roman times, the Holderness Coast has retreated 4 km – at least 29 villages have been lost to the sea.
    The Holderness Coastline is made up of soft boulder clays (tills) left after the retreat of the Devensian ice sheets about 12 000 years ago.
    80000m2 of farmland is lost each year, this has a huge effect on farmers’ livelihoods.
    It’s predicted that 200 homes and several roads will fall into the sea by 2100
  88. 88Holderness coast case study - contAround 30 villages have been lost since Roman times, meaning homes and businesses have been lost.
    Wildlife behind Spurn Point is losing diversity as the environment cannot support many species due to the lack of sediment.
  89. 89Holderness coast case study - contSpurn Head is a spit and salt marsh at the southern tip of the coastline.
    Bridlington is protected by a 4.7 km long sea wall.
    Hornsea is protected by a sea wall, groynes and rock armour.
    Coastal management at Withernsea has tried to make the beach wider by using groynes and also uses a seawall to protect the coast. Mappleton is protected by rock groynes. Spurn Head is protected with groynes and rock armour.
  90. 90Great barrier reef case studyThe Great Barrier Reef is the longest coral reef system in the world and is made up of 2900 individual reefs and 900 islands. The Great Barrier Reef is the world’s largest living structure.
  91. 91Great barrier reef case study - ThreatsHuman Activity
    Shipping: huge numbers of tourist and commercial traffic which can leave foreign objects and ship wreck.
    Oil spills: Oil containers can scar reefs and oil spills can damage wild life on reefs.
    Overfishing: One of the problems with over-fishing is trawling.
    Trawling: Pulling huge numbers of fish from the sea floor using giant nets.
    2. Natural Threats
    Bleaching: Algae can’t survive in warmer waters – so is killed off and coral loses its coloration. Larger species lose primary food source and decline.
    Crown of Thorns: Feed off the coral reef – literally “sucking the life” out of the reef. Increases as algae increases due to agricultural runoff.
    El Nino and Climate Change: Every 7 years (increase in water temperatures) therefore more coral bleaching.
  92. 92MangrovesA mangrove is a shrub or small tree that grows in coastal saline or brackish water. The term is also used for tropical coastal vegetation consisting of such species. Mangroves occur worldwide in the tropics and subtropics, mainly between latitudes 25° N and 25° S.
  93. 93Mangroves - contMangroves are salt-tolerant trees, also called halophytes, and are adapted to live in harsh coastal conditions. They contain a complex salt filtration system and a complex root system to cope with salt water immersion and wave action. They are adapted to the low oxygen conditions of waterlogged mud.

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Geography Flashcards on Coastal Environments - A level, created by Chris R on 21/11/2022.
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