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A-Level地理-冰层运动Action of Ice

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Revision: Action of Ice

 

Definitions

  • Coast: The strip of land where it meets the sea
  • Coastline: The margin of land. The limit to which wave action takes place.
  • Shore: The strip of land lying between the high and low water levels.
  • Shoreline: The limit of the shore. The line where the shore and the water meet.
  • Beach: A shore covered by a deposit of sand and/or pebbles.

Factors Determining the Nature of Coasts

  • Wave action
  • Tidal currents
  • Nature of the rocks forming the coast
  • Height of the coast
  • Nature of the climate

Formation of Waves

  • Wind blows over the sea surface.
  • The surface of the sea exerts frictional drag on the lower layer of the wind.
  • The top layer (with the least drag) moves faster than the lower layer and hence tumbles over it.
  • This causes a circular motion of wind energy that acts on the sea to create waves.

Wave Erosion
Wave erosion like river erosion involves 4 processes:

  • Abrasion/Corrosion: The wearing away of the sides and the bed of a river by the impact of the load.
  • Hydraulic Action: Erosion by the force of moving water.
  • Attrition: The breaking down of the load by particles hitting against each other.
  • Solution/Corrosion: When minerals dissolve in water.

Features Produced by Wave Erosion

  • A notch is cut by waves at high tide level and developed further.
  • As this notch is developed, a cliff is formed.
  • The cliff steepens as weathering attacks the base further.
  • As the cliff retreats, the rock debris is swept by the backwash creating a wave-cut platform.
  • Some of the debris collects along the seaward edge of the wave-cut platform forming and off-shore terrace.

Caves, Geos, Arches and Stacks

  • Holes in the cliff face are enlarged by wave action
  • A tunnel like opening called a cave is formed.
  • The cave may develop further forming a long narrow inlet known as a geo.
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