waves and coastlines

• features of high energy coasts:

  • destructive waves
  • long fetches
  • high rates of erosion
  • caves
  • arches
  • stacks, stumps , cliffs , wavecut-platform
• low energy coasts features:

  • constructive waves
  • shorter fetches
  • higher rates of deposition
  • spits , bars
  • beaches , sand dunes , salt marshes
• destructive wave features:

  • responsible for erosion
  • 10-15 waves per minute
  • steep and high , waves break at greater height due to circular motion
  • remove material from coasts , swash less powerful than backwash
• longshore currents happen when a flow if water runs parallel to the shoreline in areas where waves approach at an angle , moving both water and sediment along the shoreline
• rip currents are strong currents which flow away from the shoreline and can be dangerous for swimmers
• upwelling is movement of cold water from the deep ocean to the surface as part of the global ocean circulation currents
• spring tide - moon , sun and earth line up. High strong tide , happens twice a month
• neap tide - moon and sun align at right angles. happens twice month. strong tide.
• tides are influenced by:

  • shape of seabed
  • coriolis force
  • nearby landmasses
• tidal range is difference in height between high and low tides. varies over time due to differences in heights of tides. erosion and deposition occur in this zones
• tidal surges occur when storms bring much higher water levels than usual , often due to low-pressure conditions created by atmospheric depressions
• factors that affect wave energy :

  • fetch
  • strength of wind
  • duration of wind
• the further waves travel , the more powerful they are
• 3 types of currents:

  • longshore currents
  • upwelling
  • rip currents
• longshore currents approach the shore at an angle and transport sediment
• rip currents are strong currents moving away from shore , they develop when seawater is piled up along coastline by incoming waves
• upwelling is the movements of cold water up to the oceans surface. currents form part of the pattern of global circulation currents
• tidal range is difference in height between high and low tide . varies over time due to difference in heights of tides
• tidal surges occurs when storms bring much higher water levels than usual - often due to low-pressure conditions created by atmospheric depressions
• features of a high energy coastline:

  • wave energy is high
  • erosion happens faster than deposition of sediment
• typical landforms of a high energy coastline:

  • headlines
  • cliffs
  • wavecut platforms
• examples of a high energy coastline:

  • atlantic coasts of northern europe and cornish coast
• features of low energy coasts:

  • low wave energy
  • rates of deposition exceeds erosion of sediment
• landforms of a low energy coast:

  • beaches
  • spits
• examples of low energy coastline:

  • estuaries
  • sheltered bays e.g Baltic Sea
• concordant coastlines have alternating bands of hard and soft rock parallel to the coast (horizontal)
• discordant coastlines have alternating bands of soft and and rock at 90 degrees to the coast
• drift aligned beaches - waves come in diagonally to coast , transfer sediment