Coastal Landforms


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Coastal Landforms

  1. 1. Coastal Landforms <ul><li>Learning Objectives </li></ul><ul><li>To understand the landforms created by coastal erosion and deposition </li></ul>
  2. 2. Match up the pictures around the edge with each of the landforms below. Headland Bay Crack Arch Cave Stump Stack Wave cut platform
  3. 3. Landforms of coastal erosion 1) Headlands and Bays 2) Cliffs and Wave Cut Platforms 3) Caves, Arches, Stacks and Stumps
  4. 4. Headlands & Bays Headlands & Bays are landforms of coastal erosion. They occur where there is a resistant and less resistant rock. The diagram on the next slide explains their formation
  5. 5. Headlands and bays
  6. 6. An example of headlands and bays on the Dorset coastline… chalk clay limestone Swanage Bay
  7. 7. <ul><li>The waves attack the base of the cliff through the processes of abrasion, corrosion, hydraulic action and attrition. </li></ul><ul><li>Over time the cliff will be undercut and a wave-cut notch is formed. </li></ul><ul><li>Eventually the cliff becomes unstable and collapses. Further cliff retreat will form a wave-cut platform . </li></ul>Wave-cut notches/platforms & cliffs Click on the link below to show how a wave cut platform is formed. http:// =geo0005
  8. 8. <ul><li>1. The waves erode FAULTS (cracks) in the headland. </li></ul><ul><li>2. The waves eventually erode through the headland to form an ARCH . </li></ul><ul><li>3. The arch becomes unsupported and collapses to form a STACK . </li></ul><ul><li>4. A STUMP is formed from the collapsed stack. </li></ul>Caves, arches, stacks and stumps
  9. 9. A crack in the cliff is eroded by erosion processes such as hydraulic action and solution Over time the erosion causes the cave to break through the headland creating an arch. Eventually the top of the arch will collapse due to gravity and a lack of support. This creates a stack. A stack becomes unstable as erosion continues at the base. It eventually collapses and creates a stump 1 2 3 4
  10. 10. Click on the web addresses below for different resources on coastal stacks. <ul><li> </li></ul><ul><li>http:// = YGNUrACPrmA </li></ul>
  11. 11. Landforms of coastal deposition <ul><li>Beaches </li></ul><ul><li>Spits </li></ul>
  12. 12. <ul><li>Beaches are the main feature of deposition found at the coast. </li></ul><ul><li>They consist of all the material (sand, shingle etc.) that has built up between the high and low tide mark. </li></ul><ul><li>They normally form in sheltered areas and bays. </li></ul><ul><li>There are number of different sources of beach material – </li></ul><ul><li>fine muds and gravels are deposited at the river mouth </li></ul><ul><li>material deposited by longshore drift </li></ul><ul><li>constructive waves (bringing material up the beach from the sea) </li></ul><ul><li>material slumped onto the beach from cliff ` erosion. </li></ul>BEACH FORMATION
  13. 13. <ul><li>Spits are long narrow ridges of sand and shingle which project from the coast into the sea. </li></ul><ul><li>the main source of material building up a spit is from longshore drift which brings material from further down the coast. </li></ul><ul><li>The formation of a spit begins due to a change in the direction of a coastline ( EG a river estuary). </li></ul><ul><li>This causes a slight drop in wave energy and longshore drift will deposit material at a faster rate than it can be removed </li></ul><ul><li>Gradually a ridge is built up, projecting outwards into the sea - this continues to grow by the process of longshore drift and the deposition of material. </li></ul><ul><li>This is a spit. </li></ul><ul><li>A change in prevailing wind direction often causes the end of spits to become hooked </li></ul><ul><li>On the spit itself, sand dunes often form and vegetation colonises </li></ul><ul><li>Water is trapped behind the spit, creating a low energy zone, as the water begins to stagnate, mud and marshland begins to develop behind the spit; </li></ul>SPIT FORMATION
  14. 14. Click on the links below for useful animations & resources on spit formation <ul><li> </li></ul>