Development of coastal landscapes

• Mechanical weathering


  Physical weathering, the breakup of rock without any chemical change taking place
• Mechanical weathering processes


  • Freeze thaw
  • Thermal expansion
  • Salt crystallisation
  • Pressure release
• Biological weathering


  Plants and animals wear rocks away, through physical means or chemical reaction
• Biological weathering processes


  • Flora and fauna
• Chemical weathering processes


  • Solution
  • Carbonation
  • Oxidation
  • Hydrolysis
  • Hydration
• Mass movement


  The movement of material downhill due to gravity, often as a result of sub-aerial weathering, weakening rocks or saturation by heavy rainfall
• Mass movement processes


  • Rock fall
  • Landslide
  • Slumping
• Fluvial processes


  Very similar to coastal processes, impact coastal landforms at estuaries/deltas at river mouths, create salt marshes
• Flocculation (fluvial)


  The process where small particles suspended in water lump and form larger aggregates or flocs when salt water meets fresh water
• Aeolian processes


  Processes driven by wind, including deflation, creep, saltation and suspension
• Coastal erosion processes


  • Abrasion
  • Attrition
  • Hydraulic action
  • Pounding
  • Solution
• Coastal transportation processes


  • Traction
  • Saltation
  • Suspension
  • Solution
• Wave refraction


  The reorientation of wave fronts as they enter shallow water so that they approach parallel to the shoreline. Deeper water allows steeper and greater velocities, shallower water causes low velocity and shorter wavelengths.
• Beach


  An accumulation of material deposited in a shallow, sheltered area
• Beach zones


  • Foreshore
  • Backshore
  • Offshore
  • Nearshore
• Sand beaches


  Will have a low gradient because it can be easily taken away
• Shingle beaches


  Will have a higher gradient because the material is larger and can build up higher
• Swash aligned sediment


  Moves up and down the beach with little lateral transfer
• Drift aligned sediment


  Transferred along the coast by longshore drift
• Berms and storm beaches


  Berms are raised ridges or plateaus marking the highest tidal point, made up of the largest and most coarse sediment. Storm beaches are created in rare storm conditions when large waves push sediment to the end of the beach in the backshore zone.
• Ridges and runnels


  Smallest scale depositional feature formed in the foreshore zone through interactions of tides, currents, sediments and beach topography
• Cusps


  Mini bays in the sand
• Summer beach


  Gentler summer waves deposit sand from offshore bars onto the beach, ultimately widening it and increasing its elevation
• Winter beach


  Winter waves with more energy pick up the sand particles that were deposited in the summer, and carry them back offshore in bars, thus narrowing the beach
• Decadal variation

  Climate change is expected to produce more extreme weather events in the UK, with winter profiles present for longer and more frequent and powerful destructive waves reducing beach size
• Dorset is on the south coast of England, stretching from Lyme Regis in the west to Bournemouth in the east, part of the Jurassic Coast which was declared a World Heritage Site in 2001
• Dorset has 95 miles of near continuous sequence of rock that yields supremely preserved fossils, with 6 million tourists and 37,000 jobs in tourism
• Swanage Bay


  Has a discordant coastline where weaker sands can retreat 1m+ a year
• Dorset geology


  • Resistant rocks - chalk and limestone
  • Weaker rocks - clay and shale
• The rocks in Dorset were folded during the Alpine orogeny 7-50 million years ago, producing coastal cliffs
• Dorset sediment budget


  Sediment moves from west to east, carried by high energy destructive waves powered by south westerly prevailing winds that have built up over the Atlantic. Offshore transport goes eastwards, with erosion adding to sediment supply. Littoral (longshore) currents bring sediment in both directions, mostly east.
• Formation of Chesil Beach


  The increase in pebble size from west to east is the result of longshore drift transporting pebbles from west to east, with the largest pebbles found to the east and the smaller ones to the west. The increase in height of the shingle bank to the west also reflects the dominant east to west movement of material. Chesil Beach is separated from the mainland by a lagoon of brackish water known as the Fleet.
• Chesil Beach is both an offshore bar and a tombolo
• Old Harry Rocks


  A chalk headland at the eastern end of the Jurassic Coast towards Studland Bay that has been dramatically eroded into a stack and a stump
• Lulworth Cove


  A cove formed after a gap was eroded in a band of limestone, with a band of softer clay behind the Portland Stone eroded away to form the cove
• Durdle Door


  A sea arch formed by erosion by waves opening up a crack in the outer wall of Portland Stone (limestone) headland, becoming a cave, and rapidly eroding the Purbeck Bed behind, developing into an arch
• Groynes


  Structures built at right angles to the coast to trap material being transported by longshore drift and create larger beaches which can absorb wave energy to reduce erosion rates
• Spits and onshore bars


  Landforms formed by longshore drift moving material along the beach, where the coastline changes direction the material is moved into open water and deposited, building up until it breaks the water's surface
• Offshore bars and tombolos


  Offshore bars form due to movement of sediment from the sea bed inland since the last ice age, while tombolos are a ridge of sand/shingle which joins the mainland to an offshore island
• The Nile Delta is located at the mouth of the River Nile in northern Egypt, north of Cairo