Coastal Erosion Processes Flashcards
What is erosion
The wearing away and removal of the earths surface
Hydraulic action
The impact on the rocks or the sheer force of the water itself (with no debris). Heavy vibrations of cliff faces can occur as storm waves break against them. The resulting rock fracturing can produce quarrying at the base of cliffs leading to undercutting.
Wave quarrying
Breaking waves trap air as they hit the cliff face. Force of the water compresses into the air under any gap in the rock face which creates pressure in the joint or fissure. As water pulls back there is an explosive effect of the air under pressure being released
Attrition
Large angular fragments of rock produced by weathering and erosion are rounded, smoothed and reduced in size by wave friction against other fragments. The smaller pebbles are ammunition for abrasion ans may eventually from depositional material
Corrasion
Material transported by the waves is hurled at the cliff foot, chipping away at the rock
Abrasion
Material the sea has picked up also wears away the rock on the inter tidal platform. This acts like sandpaper and wears away the rock
Solution (corrosion)
Weak acids in sea water can dissolve alkaline rock (eg limestone and chalk)
Cavitation
Compression of air in sea facing joints as waves crash against cliffs can cause sea water to be severely compressed. As the wave recedes the pressure reduces and air comes out of solution in violent fizzing, enlarging fissures and joints
What is longshore drift / littoral drift
The movement of sediment along the coastline. Swash brings sediment up the beach whilst backwash brings it down and is always at right angles to the beach
How is material transported along the coast - TRACTION
Large boulders and pebbles are rolled along the sea bed
How is material transported along the coastline- SALTATION
Small stones, pebbles and silt bounce along the sea bed
How is material transported along the coast - SUSPENSION
Fine material such as clay and sediment is carried by the sea
How is material transported along the coastline- SOLUTION
Dissolved minerals are carried by the sea
Deposition
Deposition occurs when there is insufficient energy to move sediments further. In low energy environments, factors such as wave and wind direction, the supply and depth of sediment and water are often significant. Large depositional landforms are only found when the tidal range is less than 3m
