HKDSE Geography/M2b/Coastal Processes
Like fluvial processes, coastal processes including erosion, transportation and deposition.
There are likewise four types of coastal erosion:
- Hydraulic action, by which water erodes the coast materials.
- The pounding effect of waves erodes the coast.
- When water is forced into joints and cracks of rocks, air is compressed. When the water retreats, air expands again. Repeated expansion and compression causes stress in the joints, eroding the rock.
- Solution, by which soluble minerals like calcium carbonate are dissolved in seawater.
- Abrasion, in which load carried by the waves attacks the coast.
- Attrition, in which load collides with each other and reduce in size and angularity.
There are four processes involved in coastal transportation:
- Solution: Soluble loads are carried by waves after being dissolved in seawater.
- Suspension: Light loads are suspended inside the waves.
- Saltation: Heavier load bounces along with the waves.
- Traction: The heaviest loads roll on the seabed.
During swash, water rushes up the shore at an angle (depending on the direction of the prevailing wind). During backwash, water rushes down the shore perpendicularly because of gravity. Therefore, the sand gradually moves along the shore. This movement of sand and shingle along the shore is known as longshore drift.
Wave deposition occurs when swash is greater than backwash. The sediments remain on the beach and accumulate there.