Coastal landscape devlopment

• landforms;

  inputs: geology and lithology of coast, nature of wave approaching coast, direction and strength of prevailing wind

  processes: differential rates of erosion, wave refraction, erosion of headland and deposition in the bay

  outputs: headland and bay, erosional features of the headland, depositional features in the bay
• geology - rock type
• lithology - way rocks are arranged
• coastal morphology - how rocks are shaped by processes
• strata - layers of rocks
• bedding planes - horizontal, natural breaks in the strata, caused by gaps in time during period of rock formation
• joints - vertical fractures caused by either contraction as sediments dry out or by earth movement during uplift
• folds - formed by pressure during tectonic activity, which makes rocks buckle or crumble
• faults - formed when stress or pressure to which a rock is subjected, exceeds its external strength
• dips - refers to the angle at which rock strata lie
• wave cut platforms

  • destructive wavesbreak at the base of the cliff and erosion occurs (hydraulic action and abrasion), which begins to undercut the cliff creating a wave-cut notch during high tide
  • as the wave-cut notch gets bigger the rock above collapses
  • erosional processes repeat and cliff retreats inland
  • wave breaks earlier and energy will be dissipated, this will reduce the rate of erosion
• the erosion of rocks tends to exploit lines of weaknesses - joints, faults and cracks

  when joints and cracks are eroded by hydraulic action and abrasion, this can form caves

  If two caves join up or a single cave is eroded through a headland and arch is formed

  eventually top of the arch collapses forming stack

  as it continues to be eroded, the stack collapses to leave a stump
• sandy beaches

  • produces beach with gentle gradient
  • small particle size allows wet sand to become compact and wet which restricts rate of percolation
  • most of the swash returns as backwash
  • creates ridges and runnels
• shingle beaches:

  • steeper beach profile
  • swash often percolates down through the shingle, leaving little backwash
  • strong swash may transport material up the beach to form a berm, above the berm there is usually large boulders
• beach features:

  storm beach - ridge composed of big boulders

  berms - deposition of material, constructive waves

  beach cusps - circular shaped depressions which form when waves break directly on to the beach

  ripples - orbital movement of water in waves
• types of beaches:

  swash aligned

  drift aligned
• swash aligned beaches:

  • minimal long shore drift
  • orientated parallel to incoming wave crests
• drift aligned beach:

  • orientated parallel to the direction of the long shore drift
  • considerable amounts of sediment transported
  • predominant wave angle is at an angle to the beach
• spit formation:

  longshore drift carriers sediment in dominant wind direction to the end of the beach and deposited in the open water

  storms build up larger material

  the end of the spit is often curved as a result of wave refraction
• Tombolo:

  • a spit joined to an island
• on shore bar - formed if a spit is developed across a a bay, it will link two headlands. A lagoon is formed behind the bar
• offshore bar/barrier island - elongated bank of deposited sand or shingle lying parallel to the coastline. due to waves losing energy and depositing sediment
• psamosseres - vegetation and succession of a sand dune
• inputs of sand dunes:

  • sand supply
  • strong onshore winds
  • large tidal range
  • obstacle to trap sand
  • vegetation growth to stabilise sand in mounds
• psammoseres:

  embryo dune - first dune to develop. colonisation of grasses. Marram grass, aids water retention

  fore/yellow dunes - beyond reach of all but highest storm tides, little organic matter

  grey dunes - organic layer develops as other types of vegetation colonise

  dune slacks - depressions within dunes where water table are on or near surface and conditions are damp
• mudflats - develop on sheltered shorelines not exposed to powerful waves

  • located in estuaries
  • composed of silt and clay
  • susceptible to change such as leave level changes, wave action and changes to tidal flows
• mudflats can develop into salt marshes which is an area of coastal grassland that is regularly flooded by sea water
• halosere - vegetation succession of mudflats and salt marshes
• haloseres:

  1. low lying vegetation e.g eelgrass, begins to grow on the mudflats
  2. pioneer plants begin to colonise the area known as halophytes (tolerate salt water)
  3. as mud level rises, complex creek systems develop that channel the tides
  4. as land rises above sea level, rushes and reeds become established eventually trees such as alder, ash and then oak grow
• eustatic change - global change in sea level resulting the actual fall or rise in the level of sea itself
• isostatic change - local changes in sea level resulting from the land rising or fallling relative to the sea
• fjord - former glacial valley drowned by rising sea levels
• ria - former river valley drowned by rising sea levels
• eustatic changes:

  • global scale
  • physical factors: global climate change and more/less snow being stored as snow on land
  • human factors: changes in greenhouse effect and burning fossil fuels
• changes in sea level

  • increase in volume of ocean
  • as earths climate increases ice caps melt increasing sea level
  • thermal expansion, water expands and takes up more space due to having more kinetic energy
• isostatic changes

  • local scale
  • physical factors: uplift due to continental plate collision
  • sinking/rising crust due to weight of ice sheets adding /removed during glacial period
• sea level change:

  glaciers grow and cause local isostatic changes causing sea level to rise - by land being pushed down under the weight of the ice

  ice sheets decline and isostatic uplift of land causes a relative drop in sea level
• Long term sea level change

  stage 1:

  • climate begins to cool
  • snow and ice acts as a store for water
  • eustatic fall in sea level
• Long term sea level change

  stage 2:

  • weight of ice causes land surface to sink
  • movement is said to be isostatic and it moderates sea level fall in some areas
• Long term sea level change

  stage 3:

  • climate begins to warm
  • ice masses on land melt
  • lowland areas flood to form submerged features such as fjords and rias
  • sea level rise (eustatic)