Coasts 2

• Coast


  An open system that receives inputs from outside the system and transfers outputs away from the coast into other systems (terrestrial, atmospheric or oceanic) including rock, water and carbon cycles
• Sediment cell


  A section of the coast that is typically considered a closed system in terms of sediment
• Components of a sediment cell

  • Sources (where sediment originates)
  • Through flows (movement of sediment along the shore through longshore drift)
  • Sinks (locations where deposition of sediment dominates)
• Dynamic equilibrium


  A state where inputs and outputs of sediment are in a constant state of change but remain in balance
• Negative feedback loop


  A mechanism that lessens any amount of change that has occurred within a system, taking it back towards dynamic equilibrium
• Positive feedback


  A mechanism that exaggerates the change being made within the system, making the system more unstable and taking it away from dynamic equilibrium
• Littoral zone


  An area of the coast where land is subject to wave action, constantly changing due to short-term factors like tides and storm surges and long-term factors like changes in sea level and climate change
• Valentine's classification


  A classification system that describes the range of coastlines that can occur, including advancing and retreating coastlines
• Erosional processes


  • Corrosion
  • Abrasion
  • Attrition
  • Hydraulic action
  • Corrosion solution
  • Wave quarrying
• Vulnerability to erosion


  Influenced by factors such as whether rocks are clastic or crystalline, the amount of cracks/fractures/fissures, and the lithology of the rock
• Formation of coastal landforms

  1. Caves

  2. Arches

  3. Stacks

  4. Stumps

  5. Wave cut notch and platform

  6. Blowholes
• Longshore drift


  The process that transports sediment along the coast, driven by waves hitting the beach at an angle
• Processes of sediment transport

  • Traction
  • Saltation
  • Suspension
  • Solution
• Deposition


  Occurs when waves lose energy, causing sediment to become too heavy to carry
• Depositional landforms


  • Spits
  • Bars
  • Offshore bars
  • Sand dunes
• Stability of depositional landforms


  Dependent on a continuous supply of sediment to balance erosion, vulnerable to change during major storms
• Types of weathering


  • Freeze-thaw
  • Salt crystallisation
  • Wetting and drying
  • Carbonation
  • Acid rain
  • Oxidation
  • Solution
  • Biological
• Types of mass movement

  • Slides (rock falls, rock slides, slumps)
  • Flows (soil creep, solifluction, mudflows)
• Cliff profiles


  Influenced by the resistance of the rock to erosion and the dip in the rock strata
• The increase of the water content of soil can reduce friction leading to earth and mud to flow over the underlying bedrock
• Rock slides occur on sloped lifts over 40 degrees when exposed to mechanical weathering
• Water between joints and bedding planes which are parallel to the cliff face can reduce friction and lead to more sliding and slumps
• Slumps occur when the soil is saturated with water causing a rotational movement of soft materials such as clay and sand forming rotational scars and terrorist cliff profiles
• Vulnerability to sub-aerial processes

  • Temperature and climate can influence the prominent processes of weathering
  • In colder climates mechanical weathering is more common
  • In warmer climates chemical weathering is more common
• Cliff profiles


  Influenced by the resistance of the rock to erosion and the dip in the rock strata in relation to the sea
• Many cliff coastlines are composite, they have different rock layers which makes explaining cliff profiles very complex
• Concordant coastlines


  Where the rock strata are run parallel to the coast, the rock type varies between different concordant coasts and normally consists of bands of more resistant and less resistant rock
• Concordant coastlines can lead to the formation of dalmatian coastlines where a rise in sea levels led to the flooded widened valleys between tall headlands
• Discordant coastlines


  Where the rock strata run perpendicular to the sea which creates successions of headlands and bays
• Less resistant rocks are eroded faster than the more resistant rocks which lead to the formation of bays
• Wave refraction is the process by which waves in turn lose their energy around a headland or on uneven coastlines, the wave energy is focused on the headlines creating erosive features in these areas, the energy is dissipated in bays leading to the formation of features associated with lower energy environments such as beaches
• Coastal vegetation, rocks and sediment

  • Play a very important role in influencing the shape of a coastal landscape
  • Vegetation is essential in stabilizing a landform from further change
  • Roots of plants bind soil together which helps to reduce erosion
  • Submerged plants provide a protective layer for the ground and so the ground is less easily eroded
• Halophytes


  Plants that are tolerant to salty conditions
• Xerophytes


  Plants that are tolerant to dry conditions
• Plant succession


  1. Pioneer plants begin to grow in bare mud and sand due to the salty conditions

  2. As more deposition occurs the vegetation dies and release nutrients into the sand which reduces the saltiness of the soil allowing different plant species to start to grow

  3. These processes continue over time allowing new species of plants to colonize
• Marram grass


  • A very good example of a pioneer plant, it is tough and flexible and can cope with being blasted with sand, it has adapted to reduce water loss through transpiration and their roots grow up to three metres deep and can tolerate temperatures of up to 60 degrees centigrade
• Salt marsh succession


  1. Algal stage - gut weed and blue-green algae establish

  2. Pioneer stage - cord grass and glass water grow their roots begin to stabilize the muds

  3. Establishment stage - salt marsh grass and sea asters grow creating a carpet of vegetation

  4. Stabilization - sea thrift, scurvy grass and sea lavender grow and so rarely ever gets submerged beneath the marsh

  5. Climax vegetation - rush, sedge and red fescue grass grow
• High energy coastlines


  Associated with more powerful waves, typically have rocky headlands and landforms and fairly frequent destructive waves, often eroding as the rate of erosion exceeds the rate of deposition
• Low energy coastlines


  Have less powerful waves, occur in sheltered areas where constructive waves prevail, fairly sandy areas with landforms of deposition as the rates of deposition exceeds the rate of erosion
• Factors affecting wave size

  • Strength of the wind
  • How long the wind has been blowing for
  • Water depth
  • Distance of fetch