landfordms

• Coastline


  The land along the edge of a sea, ocean, or lake
• Types of coastlines


  • Erosional
  • Depositional
• Erosion


  The process by which the land is worn away by forces such as water (rivers, ocean waves or glacial ice) or wind
• Erosional coastal environment


  • Victoria's Great Ocean Road
• Deposition


  The process by which material is dropped in a new place having been eroded and then transported from somewhere else
• Depositional coastal environment


  • Lakes Entrance & the 90 mile beach in Victoria's East Gippsland
• Transportation


  The process by which eroded material such as sand is moved to a new place
• Longshore drift


  The natural process by which sand is transported along a shoreline in a particular direction
• When we modify the shoreline to suit our own purposes we sometimes disrupt the natural movement of sand along the coast producing unintended consequences
• Disruption of longshore drift

  • Build-up of sand in one place and disappearance of sand further up the coast
• The solution to disrupting longshore drift is to set up an expensive sand by-pass system
• Waves


  • They are generated by the wind
  • In windy, exposed areas waves have more energy and are more destructive (erosional waves)
  • In more protected areas with less wind, waves tend to have less energy and are constructive (depositional waves)
• Wave crest


  Top of the wave
• Wave trough


  Lowest point between two crests
• Wave height


  Height between the trough & the crest
• Wave length


  The distance between two crests
• Wave frequency


  The number of waves in any given time frame
• Breaker


  Where the top of the wave topples over or breaks
• As waves approach the shoreline they begin to drag on the shallower bottom which causes them to rise up. The wave height increases until they break and they also slow down reducing the wave length.
• Rocks are harder than water, yet water can wear away the hardest rocks along a shoreline over thousands of years
• Mechanical weathering


  As waves crash on the rocks of the shoreline water can be forced into small cracks and this compresses the air inside the cracks, which can eventually split the rocks
• Abrasion


  Waves pick up sand and small rocks and smash them against the rocks of the shoreline, greatly speeding erosion between high and low tide levels
• Wave refraction


  When waves move into shallow water as they approach the shore they begin to drag on the bottom, rise up, and slow down, causing the waves to bend and take on the approximate shape of the shoreline
• Wave diffraction


  When waves approach a headland they wrap around the headland which concentrates the wave energy onto the headland, while in between headlands in sandy bays the wave energy is spread out
• Erosional features tend to be formed on headlands, while deposition is far more likely to occur in sandy bays
• Cliff recession


  1. As waves crash on the shore, erosion occurs between the high and low tide marks and a notch develops

  2. As the notch cuts into the base of a cliff more and more over the years, a large overhang will develop

  3. Eventually, this will collapse, and a section of the cliff will collapse onto the shore platform below

  4. The cliff has retreated, or moved back

  5. This process will repeat itself over and over
• Stack


  A section of the cliff that resists erosion because it is made from harder rocks, and remains standing for many years as the rest of the cliff recedes
• Rock platform


  The areas of relatively smooth and flat rock at the base of a cliff, covered by water at high tide but exposed at low tide
• Rock pool


  Formed when large, hard boulders remaining on the rock platform are rocked around by wave action, drilling down into the softer platform and creating a pool
• Bay


  Sheltered, low energy zones that form in bands of softer shoreline where the cliff erodes at a faster rate
• Headland


  Exposed rocky outcrops made of harder rock, flanking bays
• Cave formation


  As waves crash on cliffs or wrap around headlands, erosion occurs between high and low tide marks, forming a notch which can develop into a cave if the overhang above does not collapse
• Arch formation


  As caves develop on opposite sides of a headland they can eventually meet up, having eroded right through, forming an arch
• Stack formation


  As erosion continues, all arches must eventually collapse, leaving the remaining rock outcrop isolated in the ocean as a stack
• In 1990, the famous double arch along Victoria's Great Ocean Road called London Bridge collapsed without warning, stranding several tourists
• Blowhole


  Where waves have eroded a narrow pipe, perhaps through the roof of a cave, and as waves crash into the entrance, water and compressed air can suddenly shoot out the other end causing a spectacular jet of water
• Inlet


  A long, narrow protruding bay that can form when the roof of a very long cave, which has eroded into the cliffs, collapses
• Stacks


  Rock outcrops isolated in the ocean that remain after arches collapse due to erosion
• All stacks will eventually erode away
• London Bridge double arch along Victoria's Great Ocean Road collapsed without warning, stranding tourists


  1990