2.4B Erosion

• Hydraulic action:

  • where the force of the water itself breaks the rock
  • occur by the direct impact of the water itself or breaking waves compressing air into the cracks of rocks
• abrasion:

  • where a wave picks up sediment and throws these load items against a rock. The repeated impact chips away at the rock face until small fragments break away. 
• Corrosion:

  • where water in waves dissolves rock mineral
• attrition:

  • where material transported by a wave is eroded through collision with other load items. It breaks down sediment into smaller sized particles, and the repeated collision blunts any of the particles' sharp edges, making the sediment increasingly rounded. 
  • occurs in the foreshore and nearshore zones, where sediment is moved by swash and backwash. 
• how erosion influences wave type, size and lithology:

  • They are most effective during high energy storm events with large destructive waves. 
  • However, even coastlines composed of soft, unconsolidated sediment (e.g. boulder clay of Holderness Coast in Yorkshire), experience little erosion under normal conditions.
  • Most erosion (in the UK) occurs in the winter, in high energy storms. 
• effect of erosion:

  • The boulder clay of the Holderness coast has retreated by 120 m in the last 100 years. 
  • The granite of Land's End in Cornwall has retreated by only 10 cm in the last 100 years.