Coasts - Content

• Outline the processes which lead to the development of barrier beaches.

  • A barrier beach is usually formed as an extension to a spit (1).
  • Longshore drift moves sediment along the coastline until there is a change in the coastline (1).
  • A spit develops, usually in a bay and once the spit develops across the whole bay, a barrier beach forms (1).
  • Barrier beaches are unlikely to form in estuaries as the outcoming force of freshwater will always keep part of the estuary clear (1).
• Explain the development of saltmarsh environments.

  • Salt marshes tend to develop in sheltered estuaries behind spits (1).
  • As the spit develops, the area behind it becomes sheltered (d).
  • Silt is deposited by the river which gradually builds up to form an inter-tidal mud flat (1).
  • The mud flat continues to build and rise above sea level with the addition of further silt (1).
• Outline the process of sub-aerial weathering in the development of coastal landscapes.

  • Sub-aerial weathering involves the action of rainwater and insolation upon landforms in the coastal landscape (1).
  • Here material is broken in situ, rocks are weakened and can contribute to sudden large-scale movements (1).
  • Chemical weathering occurs when weak carbonic acid in rainwater attacks limestone cliffs (1).
  • This leads to the formation of karst landscapes (d).
• Outline the role of waves in the transportation of sediments at the coast.

  • Constructive waves tend to bring sediments on to the beach (1).
  • This is due to the low energy nature of these wave (1) (d).
  • They tend to have low frequency, height and limited backwash (1) (d).
  • The swash is therefore a key factor in bringing sediments onshore (1) (d).
• Outline factors leading to the formation of fjords.

  • Fjords are an example of coastal landforms of submergence (1).
  • They are primarily a product of glacial erosion (1).
  • As glaciers advanced towards coastal locations in Norway for example, they carved out vast glacial troughs (1),
  • through processes such as abrasion and plucking (1)(d).
  • A combination of localised isostatic re-adjustment and global eustatic sea level change has led to the flooding of these valleys (1).
• Explain the concept of the sediment cell.

  • A sediment cell is a closed system usually bounded by headlands or a change in longshore drift (1).
  • Within a sediment cell, there is erosion, transport and deposition of sediment within a long term cycle (1).
  • The only inputs into the sediment come from erosion from the sea bed or land (1).
  • There is little or no movement of sediment between cells (1).
• Abrasion:

  • A form of erosion where loose material 'sandpapers' the walls and floors of the river, cliff or glacier
• Backshore:

  • The upper beach closest to the land, including any cliffs or sand dunes
• Beach Morphology:

  • The surface shape of the beach
• Coastal Recession:

  • The retreat of a coastline due to erosion, sea-level rise or submergence
• Concordant Coast:

  • A coastline where bands of alternate geology run parallel to the coast
• Dalmatian Coast:

  • A concordant coastline with several river valleys running perpendicular to the coast, producing parallel long islands and long inlets
• DEFRA's 1:1 Cost-Benefit Analysis:

  • The evaluation of a coastal town's economic value compared to the cost of the management required
• Discordant Coast:

  • A coastline where bands of alternate geology run perpendicular to the shore
• Dynamic Equilibrium:

  • Where a natural system tries to achieve a balance by making constant changes in response to a constantly changing system
• Emergent Coast:

  • A coastline that is advancing relative to the sea level at the time
• Eustatic:

  • Global changes to sea levels
• Foreshore:

  • The lower part of the beach covered twice a day at high tide, receiving the most regular wave action
• Freeze Thaw:

  • A form of physical sub-aerial weathering where water freezes in the cracks of a rock, expands, and weakens the rock
• Geology:

  • The structure and arrangement of a rock
• Glacial Erosion:

  • The removal of loose material by glacier ice, involving plucking, abrasion, crushing, and basal meltwater (necessary in the formation of Fjords)
• Grading:

  • The layering of sediments based on their size
• High-energy environment:

  • A coast where wave action is predominantly large destructive waves, causing much erosion
• Impermeable:

  • A rock that does not allow rainwater to pass through
• Isostatic:

  • A change in local coastline or land height relative to the sea level
• Littoral Cell:

  • A section of the coast involving significant sediment movement, not a closed system
• Permeable:

  • A rock that allows rainwater to pass through it
• Plant succession:

  • Change to a plant community due to growing conditions adapting (e.g., sand dunes and salt marshes)
• Subaerial Processes:

  • The combination of mass movement and weathering that affects the coastal land above sea level
• Submergent Coast:

  • A coast that is sinking relative to the sea level of the time
• Till:

  • Deposits of angular rock fragments in a finer medium
• Positive Feedback Loop: A feedback loop that amplifies a change in the system.
• Negative Feedback Loop: A feedback loop that reverses the change that caused it.
• Landscape: The physical features of a place, including the natural environment and the human-made features.
• Landform: A feature of the landscape that is formed by the action of natural processes.
• Hydraulic Action: The force of water pushing against the river banks and river bed
• Wave quarrying: when high energy, tall waves hit the cliff face they have the power to enlarge joints and remove large chunks of rock in one go through vibration. This occurs due to the intense force of these waves.
• Cavitation: Compression of air in sea-facing joints as waves crash against cliffs can cause sea water to be severely compressed. As the wave recedes the pressure reduces and air comes out of solution in violent 'fizzing', enlarging fissures within joints.
• Solution: This process of erosion occurs when weak carbonic acid in seawater dissolves rock at the coastline and breaks it down (particularly that containing calcium carbonate such as limestone)
• Attrition: the process of erosion caused by the grinding and wearing away of rock, sediment, or other materials by friction and collision.