coastal landscapes

• what are the types of erosional landforms

  shore platforms

  bays and headlands

  geos and blowholes

  caves, arches, stacks and stumps
• outline development of geos/blowholes

  lines of weakness in rocks eroded quickly

  hydraulic action forces water into weaknesses = weakened rock strata

  tunnel like cave running at right angle to cliff line suffers roof collapse = geo

  part of roof of tunnel like cave collapses along master joint and may form vertical shaft reaching cliff top = blowhole
• modification/alternate theory of geos/blowholes

  might form from mining shafts experiencing roof collapse

  headland retreats = blowhole retreats to form geo
• example of geos/blowholes


  huntsmans head - geo
• outline energy flows in formation of geos/blowholes

  kinetic energy - waves, wind, storm conditions

  gravitational potential - roof collapse
• outline development of wave cut notches/platforms


  sea attacks cliff base in tidal range

  wave cut notch forms due to hydraulic action and abrasion

  notch deepens until overlying material collapses = cliff

  process repeats = cliff retreat

  rock just below tide level = always submerged so no wave action = flat surface

  after 500m waves will no longer reach cliffs due to friction
• outline weathering involved in formation of wave cut notches and platforms

  aoelian weathering

  chemical weathering accelerated by marine organisms - algae release CO2 making sea water more acidic = faster erosion rates
• modification of wave cut notches/platforms

  overtime platform will erode slowly = cliff erosion increases
• example of wave cut notch and platform

  selswicks bay - flamborough coastline
• outline energy flows involved in formation of wave cut notches and platforms

  kinetic energy - waves, transport of undercut material, abrasion

  potential energy - mass movement
• outline energy flows in formation of headlands and bays

  kinetic energy in waves - erosion at headlands, deposition at bays
• outline development of headlands and bays

  discordant coastline = differing rock structures = differing erosion rates

  weak lithology = easily exploited by waves = bays

  strong lithology = harder to exploit = headlands

  bays are the width of the rock band
• modification of headlands and bays overtime


  headlands often develop into stacks/stumps
• examples of headlands/bays


  flamborough head

  file bay
• outline energy flows in formation of caves, arches, stacks and stumps

  kinetic energy - waves and wind

  gravitation potential - rock collapse
• outline development of caves, arches, stacks, and stumps

  points of weakness in headland exploited via hydraulic action and freeze thaw

  small cave develops in tidal range

  cave further eroded through headland until forms arch

  continued erosion and biological weathering from above = arch roof collapse= stack

  erosion at base causes stack to collapse = stump
• outline modification of caves, arches, stacks, and stumps

  climate change = colder = increased freeze thaw = faster erosion

  climate change = warmer = faster biological weathering = faster erosion

  headland retreat over time

  stacks/stumps disappear over time
• example of caves, arches, stacks and stumps

  flamborough head stacks made of chalk (strong lithology)
• what are the depositional landforms

  beaches

  spits

  bars

  tombolos

  deltas

  salt marshes
• outline formation of beaches

  sediment comes from 3 main sources - cliff erosion, offshore, rivers

  sand, minerals and sediment worn down over time by erosion

  material transported and deposited by constructive waves

  often form in sheltered bays where waves have little energy
• equilibrium in beaches


  storm = increased erosion = formation of offshore bar = waves break earlier = lose energy = constructive waves = deposition
• modification of beaches


  higher in summer due to increase in constructive waves

  storm conditions hurl sediment to top of beach = formation of storm beach/storm ridge
• outline formation of spits

  formed by longshore drift

  prevailing wind pushes constructive waves up beach at an angle

  waves reach end of beach and deposit material

  material accumulates = spit
• modification of spits


  wave refraction around edge of spit = recurved spit

  formation of salt marsh behind it due to area being sheltered leading to deposition

  form onshore bar

  form tombolo
• example of spit


  Orford ness spit
• outline formation of onshore bar

  spit grows across an indentation until it joins the land on the other side

  occurs due to transport of sediment by longshore drift

  lagoon forms on the landward side
• outline formation of tombolos

  formed by spit continuing to grow seawards until joins island

  formed by longshore drift
• modification AND equilibrium of tombolos, spits and bars over time

  storm event = destructive waves = sediment lost = offshore bar forms = more deposition = rebuilds
• formation of salt marshes

  mud/silt deposited along sheltered part of coastline (rate of deposition > rate of transportation)

  flocculation = clay deposited

  accumulates = mud flats

  halophytes grow binding mud and sediment

  plants trap more sediment meaning mud flat is decreasingly covered by tide

  tide/rain leaches salt out making soil more fertile

  2nd generation plants grow

  vegetal succession occurs and marsh uplands form
• define flocculation


  electrical charges of clay mean they are attracted to each other and clump to form flocs, which are larger and heavier = deposition
• 3 areas of salt marsh morphology

  mudflats

  lower marsh

  upper marsh
• characteristics of mudflats of salt marshes

  too hostile for most plants

  lowest area
• characteristics of lower marsh

  salt-tolerant plants

  low altitude = flooded at high tide

  soil highly saline

  covered by salt pans - depression where salty water pools and evaporates
• characteristics of upper marsh

  highest area

  flooded only at highest tides

  rainwater flushes salt out

  colonised by less salt-tolerant species
• outline formation of deltas

  form where river meets sea at a low energy environment

  river material eroded, loses energy when meets sea = fluvial deposition

  encouraged by continental shelf margin providing platform for sediment accumulation

  low tidal range
• 3 distinctive components of deltas


  upper delta plain - furthest inland, beyond tidal reach, completely fluvial deposits

  lower delta plain - inter-tidal zone, regularly submerged, both fluvial and marine deposits

  submerged delta plain - lies below mean tidal mark, composed mainly of marine deposits
• 3 types of delta

  cuspate

  arcuate

  birds foot
• outline cuspate delta


  pointed extension to coastline

  shaped by regular, gentle currents from opposite direction
• outline arcuate delta


  sufficient sediment available for delta to grow seawards, strong wave action trims and smooths leading edge
• outline birds foot delta


  distributaries branch out in branching pattern, river sediment supply exceeding rates of erosion