3.2.3 Marine Processes Flashcards
Explain the process of hydraulic action
Hydraulic action is the name for a group of erosion processes that occur due to the power of the waves, with no involvement of rocks at all
Sea water forces air into cracks and joints in the rock
The pressure from the waves on this air causes the cracks and joints to expand
When larger, loose blocks of rocks are eroded in this way it is called wave quarrying
If the waves are very large cavitation will occur
High pressure air bubbles in the wave collapse on the rock, generating shock waves that erode the surface like a hammer
Explain the process of abrasion
Abrasion occurs when breaking waves that are carrying sediment scrape against the rock surface
This is also known as corrasion
It is dependent on how much sediment is available in a particular area of the coastal system
Outline four types of marine transportation
Traction involves the rolling of large and heavy rocks along the seabed.
Saltation involves smaller material being bounced along the seabed. The video below shows material being bounced along a beach by waves.
Suspension is when lighter sediment is suspended within the water. This often discolours the water close to the shore.
Solution: Sediment that has dissolved completely will be transported in solution.
Outline the process of long-shore drift
Longshore (littoral) drift is the main process of deposition and transportation along the coast
Influenced by the prevailing wind, waves approach the beach at an angle
As the waves break, the swash carries material up the beach at the same angle
As the swash dies away, the backwash carries the material down the beach at right angles (90°)
The process repeats, transporting material along the beach in a zig-zag movement
Offshore currents can contribute to the movement of sediment along or up the beach
When marine deposition occurs
Deposition occurs when waves lose energy
When do waves lose energy?
The wind slows or changes direction
The wave experiences friction, usually with the sea floor as the depth decreases
When the coastline changes direction such as at an estuary or headland
How marine deposits vary depending on the coastline?
High energy coastlines deposit large rocks and shingle but generally maintain enough energy to carry smaller sediment particles
This is why these types of coastlines tend to have rocky beaches, such as Brighton on the south coast
Low energy coastlines deposit smaller sediment due to low wave velocity, creating sandy beaches
