General Flashcards

• Coastal system


  An open system that receives inputs from outside and transfers outputs away
• Coasts are open systems, but can be considered closed systems for scientific research and coastline management planning
• The coastal system is impacted by and impacts processes in the five oceans and smaller seas
• Sediment cells


  Sections of coast often bordered by prominent headlands, where sediment movement is almost contained and in dynamic equilibrium
• Dynamic equilibrium


  The maintenance of a balance in a natural system, despite constant change, where inputs and outputs remain in balance
• Dynamic equilibrium may be upset by human interventions or natural variations in the short or long term
• Key features of the coastal system

  • Inputs
  • Outputs
  • Stores/Sinks
  • Transfers/Flows
  • Energy
  • Feedback Loops
• Inputs to the coastal system

  • Marine: Waves, Tides, Salt Spray
  • Atmosphere: Sun, Air Pressure, Wind Speed and Direction
  • Humans: Pollution, Recreation, Settlement, Defences
• Outputs from the coastal system

  • Ocean currents
  • Rip tides
  • Sediment transfer
  • Evaporation
• Stores/Sinks in the coastal system


  • Beaches
  • Sand Dunes
  • Spits
  • Bars and Tombolos
  • Headlands and Bays
  • Nearshore Sediment
  • Cliffs
  • Wave-cut Notches
  • Wave-cut Platforms
  • Caves
  • Arches
  • Stacks
  • Stumps
  • Salt Marshes
  • Tidal Flats
  • Offshore Bands and Bars
• Transfers/Flows in the coastal system

  • Wind-blown sand
  • Mass-movement processes
  • Longshore drift
  • Weathering
  • Erosion: Hydraulic Action, Corrosion, Attrition, Abrasion
  • Transportation: Bedload, In suspension, Traction, In solution
  • Deposition: Gravity Settling, Flocculation
• Energy sources in the coastal system

  • Wind
  • Gravitational
  • Flowing Water
• Negative feedback loop


  Mechanisms that balance changes, taking the system back towards equilibrium
• Positive feedback loop


  Mechanisms that exaggerate change, taking the system away from dynamic equilibrium
• Sediment sources for the coastal system

  • Rivers
  • Cliff erosion
  • Wind
  • Glaciers
  • Offshore sediment sinks
  • Longshore drift
• Sediment budgets


  Use data on inputs, outputs, stores and transfers to assess gains and losses of sediment within a sediment cell
• Littoral zone


  The area of land between the cliff/dunes and the offshore area beyond wave influence, constantly changing due to short and long-term factors
• Coastal terminology


  • Shore/Shoreline
  • Offshore
  • Onshore
• Wave formation


  Wind creates frictional drag on water surface, forming ripples and waves with circular orbital motion, which becomes more elliptical as waves approach the coast
• Factors affecting wave energy

  • Strength of the wind
  • Duration of the wind
  • Size of the fetch
• Wave types


  • Constructive: Formed by open ocean weather systems, long wavelength, low frequency, low waves that surge up the beach
  • Destructive: Localised storm events, short wavelength, high frequency, high waves that plunge onto the beach
• Presence of constructive waves


  Causes deposition, steepening beach profile, leading to more destructive waves, which erode beach, reducing profile and leading to more constructive waves
• Tides


  Caused by gravitational pull of sun and moon, highest high and lowest low tides occur during spring tides when sun and moon are aligned, lowest high and highest low tides occur during neap tides when sun and moon are perpendicular
• Rip currents


  Powerful underwater currents flowing away from the shore, caused by a buildup of water at the top of the beach and resistance from breaking waves
• Riptides


  Occur when the ocean tide pulls water through a small area such as a bay or lagoon
• Characteristics of high and low energy coastlines


  • High energy: Rocky headlands, frequent destructive waves, erosion exceeds deposition
  • Low energy: Sandy areas, constructive waves prevail, deposition exceeds erosion
• Wave refraction


  The process by which waves turn and lose energy around a headland, focusing energy on the headland and dissipating it in bays
• Wave refraction and erosion


  Erosion leads to formation of headlands and bays, which then increases erosion on headlands and reduces erosion in bays, leading to dynamic equilibrium
• Main processes of coastal erosion

  • Corrasion
  • Hydraulic action
  • Corrosion
  • Attrition
  • Abrasion
• Erosion


  • Collaborative process involving removal of sediment from a coastline by different types of erosion, not one type acting by itself
• Corrasion


  Sand and pebbles picked up by the sea from an offshore sediment sink or temporal store and hurled against the cliffs at high tide, causing the cliffs to be eroded
• Abrasion


  Sediment moved along the shoreline, causing it to be worn down over time
• Attrition


  Wave action causes rocks and pebbles to hit against each other, wearing each other down and becoming round and smaller
• Hydraulic Action


  As a wave crashes onto a rock or cliff face, air is forced into cracks, joints and faults within the rock. The high pressure causes the cracks to force apart and widen when the wave retreats and the air expands.
• Corrosion (Solution)


  Mildly acidic seawater can cause alkaline rock such as limestone to be eroded, similar to carbonation weathering
• Wave Quarrying


  Breaking waves that hit the cliff face exert a pressure up to 30 tonnes per m², directly pulling away rocks from a cliff face or removing smaller weathered fragments
• Factors affecting coastal erosion

  • Waves
  • Beaches
  • Subaerial processes
  • Rock type
  • Rock faults
  • Rock lithology
• Traction


  Large, heavy sediment rolls along the sea bed pushed by currents
• Saltation


  Smaller sediment bounces along the sea bed, being pushed by currents
• Suspension


  Small sediment is carried within the flow of the water