landforms_from_deposition.jpg
Video showing all of the coastal landforms of deposition - http://www.bbc.co.uk/learningzone/clips/depositional-coastlines/4023.html
Beaches

  • They are usually found in sheltered bays between two headlands
  • The headlands protect the area from erosion
  • Low constructive waves deposit material on the shore
  • Gradually a beach is built up
  • Material on a beach is well sorted – the biggest pebbles are nearest the land with the smallest nearest the sea
  • The larger the material the steeper the beach – pebble is steeper than sand


Spits
http://www.geographyalltheway.com/ks3_geography/coasts/imagesetc/deposition.swf - an amazing animation which explains the formation of a spit!!
Video showing the formaiton of a spit - http://www.bbc.co.uk/learningzone/clips/the-formation-of-spits/3246.html

spit[1].jpg

A spit is an area of sand or shingle that has been transported by longshore drift and then deposited as the coastline has changed direction. It is attached to the land at one end. It is a depositional landformd. Hurst Castle Spit in Hampshire is a very famous example.

Where the coastline changes direction, sediment is deposited in the same direction as the original coastline (i.e. in line with the prevailing wind direction). Where there is a break in the coastline and a slight drop in energy, longshore drift will deposit material at a faster rate than it can be removed and gradually a ridge is built up. The material is deposited in the deeper water offshore until the ridge is built above the level of the sea. Drift continues along the seaward side of the spit extending it further down the coast while salt marsh develops in the slow-moving water on the landward side.

Spits can become a permanent feature. This happens when the prevailing wind picks up sand from the beach and blows it inland across the spit to form sand dunes. These dunes will then be colonised by vegetation, which stabilises them. It is common for a salt marsh to develop in the sheltered area of water behind the spit. Water is trapped behind the spit, creating a low energy zone. As the water begins to stagnate, mud and marsh begin to develop behind the spit.

A spit may grow out across a river estuary. Where the spit is crossing a river mouth, the river will be diverted so that it follows the coastline for some miles before reaching the sea.

Bars
Bar[1].jpg


A


Bars can form in several ways:
(a) a spit grows the whole way across a bay
(b) a sandbank devlops offshore, parallel to the shore, and is moved towards the coastline by the waves and wind until it joins the mainland


Slapton Sands is an example of a bar. The lagoon of water than has formed on the landward side of the bar is called Slapton Ley.


A tombolo is formed where a spit joins an island to the mainland. An example is the Isle of Portland which is joined to the mainland by a shingle ridge known as Chesil Beach.


Useful weblinks:


BBC Class Clips video - Blakeney Point
BBC Class Clips video - Kaitorete Spit, New Zealand
BBC Scotland video about spits, bars and tombolos
BBC Bitesize - Spits
BBC Bitesize - Tombolos