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Sec3 Coast features
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Sec3 Coast features

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Sec3 Coast features Sec3 Coast features Presentation Transcript

  • Coastal Landforms Erosional Landforms Cliffs and Wave-cut platforms • A cliff is a steep rock face. Some tilt forward while others tilt backwards. • They are produced by waves undercutting a steep rocky coast.
  • Coastal Landforms Erosional Landforms Cliffs and Wave-cut platforms • Hydraulic action and abrasion erode cracks on a rock surface. • These cracks may enlarge to produce a notch, which may further deepen inwards to produce a cave.
  • Coastal Landforms Erosional Landforms Cliffs and Wave-cut platforms • Further undercutting by waves will cause the roof of the cave to collapse. • Undercutting by waves at the base forms an overhanging cliff.
  • Coastal Landforms Erosional Landforms Cliffs and Wave-cut platforms • This overhanging cliff will collapse and materials will be deposited at the foot of the cliff. • Some of these materials may be washed out into the sea and picked up by waves that throw them against the base of the cliff, causing further erosion.
  • Coastal Landforms Erosional Landforms Headlands and bays • Along coasts with alternate strips of resistant hard rocks and less resistant soft rocks arranged at right angles to the coast, the soft rocks are eroded faster than hard rocks. • This forms indented coasts with headlands and bays.
  • Coastal Landforms Erosional Landforms Headlands and bays • When softer rocks are eroded away, bays are formed. The remaining hard rocks are headlands. • Waves usually approach the shore at a right angle. • As they approach an indented shore, they refract. Consequently, they move parallel to the shore. • This is called wave refraction, caused by the uneven depth of the seafloor. • As they bend energy is unevenly distributed along the shoreline.
  • Coastal Landforms Erosional Landforms Headlands and bays • The part of the waves nearer to the shore touches the seafloor first. • It slows down due to friction with the seafloor while the rest of the waves move at full speed.
  • Coastal Landforms Erosional Landforms Headlands and bays • As a result of wave refraction, waves approach the shallow sea in front of the headland first before they reach the adjacent bays. • Wave energy strikes at the headland rather than the bay and erosion occurs. • Along the bays, waves are diverged and weak. • Deposition of sediments take place along the bays over time, forming a sandy beach.
  • Coastal Landforms Erosional Landforms Headlands and bays • Wave refraction determines when and where erosion, transportation and deposition takes place.
  • Coastal Landforms Depositional Landforms Beaches • It is a zone of deposition along the coast, usually consisting of sandy materials.
  • Coastal Landforms Depositional Landforms Beaches • It can also be formed from broken coral pieces, small stones called pebbles and blackish volcanic sand. • The size and composition of the materials vary greatly and change over time according to weather conditions, wind direction and ocean currents.
  • Coastal Landforms Depositional Landforms Beaches • Usually the waves and wind will sort out materials on the beach, usually with finer materials nearer the sea and coarser materials further inland.
  • Coastal Landforms Depositional Landforms Spits and Tombolos • Longshore drift transports materials along a coast. • If there is a certain change in the direction of the coast, the drift will continue to transport materials in the original direction into the sea. • When materials enter the sea, deposition occurs.
  • Coastal Landforms Depositional Landforms Spits and Tombolos • After some time, materials accumulate above water surface, forming a spit. • If there is an island near the mainland where the spit is formed, it may join the island to the mainland forming a tombolo.
  • Homework Using well-labelled diagrams, explain the formation of: a) a cliff b) a wave-cut platform c) headlands and bays d) a beach e) a spit and a tombolo