Landforms of Coastal Deposition

HideShow resource information
  • Created by: holly
  • Created on: 28-04-13 18:21

BEACHES

  • commonly found in bays, 
  • represent accumulation of material deposited between lowest spring tides and highest point reached by storm waves
  • mainly constructed from sand and shingle
  • water rapidly percolates through shingle so the backwash is limited (shingle beaches)
  • together with uneven surface this means little material is moved down beach (shingle beaches)
1 of 7

BEACHES: storm beach, berms

  • strong swash at spring high tide leavel creates storm beach
  • storm beach is a ridge of largest boulders thrown by biggest waves
  • below storm beach is series of ridges marking high tide 
  • known as berms
  • built up by constructive waves 
  • indicate top of swash where deposition occurs
2 of 7

BEACHES: cusps , ridges and runnels

  • cusps are semi-circular shaped depressions
  • formed when waves break directly onto beach
  • when swash and backwash are strong
  • usually occur between sand and shingle on a beach
  • below cusps at the low water mark ridges and runnels are formed
  • developed on the sand by wave action
  • or tidal currents representing spreading of  the waves energy
3 of 7

SPITS

Spit: a beach of sand or shingle linked at one end to land (eg Spurn Head, Yorkshire)

  • where prevailing winds hit the coast at right angles LSD causes sediment to move along coastline towards headland to beach
  • Litoral drift continues past headland
  • after reaching other side of headland, where the coastline changes direction abruptly there is a change in the direction of prevailing wind
  • this causes refraction of the waves which pushes sediment closer to the original coastline
  • this all causes the ridge of deposited sand to form a recurved end
  • as the spit extends further towards the river estuary, the highest velocity flow from the river forces the sediment to be carried away so it cannot be deposited across the front of the river's channel.
4 of 7

SALT MARSHES

can form behind a spit due to drop in velocity causing deposition.

  • exposed at each low tide, thin layers of mud containing only algae at first.
  • as the mud deepens pioneer plants establish, trapping more sediment. Channels are cut by receeding water at low tide. (plants: Glasswort, Spartina)
  • more plants higher up the marsh trap more sediment, causes marsh surface to rise and channel to deepen. (plants:marramgrass, sea pursfare)
  • as the mud deepens further, marsh grows slowly with more plants colonising higher zones until largely covered with vegetation. Only highest tides cover marsh and erosion along channels cause bank collapse and salt pans to form. (plants: red fescue, sea rush)
  • Channels deepen further due to runoff, marsh only covered at high tide (plants: sea thrift, sea lavender)
5 of 7

SAND DUNES

  • dunes can form behind a spit inland due to sand being blown onto the original coastline by the dominant wind
  • the sand becomes trapped in obsticles like seaweed, rocks or driftwood near the back of the beach
  • the sand becomes attached to pioneer plants forming embryo dunes (little mixed salt and fresh water - lyme grass)
  • these grasses are xerophytic and have special adaptations to reduce water loss
  • inital plant growth adds organic matter (aids water retention)
  • upward growth of embyro dunes creates foredunes
  • inland these are fixed and organic layers develop (can be 20m high)
  • the supply of beach sand gradually decreases and stops
  • forms blow outs and dune slacks
  • dune slacks are always damp (high water table) enables woodland and rushes to develop

at the end of all these stages the formation is called a psammosere.

6 of 7

BARS AND TOMBOLOS

Bar: a spit joining one part of mainland to another (eg across a bay) can form a lagoon behind

Tombolo: a spit joining one part of the mainland to an island

7 of 7

Comments

No comments have yet been made

Similar Geography resources:

See all Geography resources »See all Coastal environments resources »