Coastal Processes Flashcards
Define corrasion/ abrasion?
Bits of rock and sediment transported by the waves smash and grind against rocks and cliffs, breaking bits off and smoothing surfaces.
Define hydraulic action?
Air in cracks in cliffs is compressed when waves crash in. The pressure exerted by the compressed air breaks off rock pieces.
Define cavitation?
As waves recede, the compressed air expands violently, again exerting pressure on the rock and causing pieces to break off.
Define wave quarrying?
The energy of a wave as it breaks against a cliff is enough to detach bits of rock.
Define solution?
Soluble rocks get gradually dissolved by the seawater.
Define attrition?
Bits of rock in the water smash against each other and break into smaller bits.
What are the 4 main processes of transportation?
Solution, suspension, saltation and traction.
Define solution?
Substances that can dissolve are carried along in the water.
Define suspension?
Very fine material, such as silt and clay particles, is whipped up by the turbulence and carried along the water. Most eroded material is transported this way.
Define saltation?
Larger particles such as pebbles or gravel are too heavy to be carried in suspension. Instead, the force of the water causes them to bounce along the sea bed.
Define traction?
Very large particles are pushed along the sea bed by the force of the water.
Describe the process of longshore drift?
Swash carries sediment up the beach, parallel to the prevailing wind. Backwash carries sediment back down the beach, at right angles to the shoreline. When there’s an angle between the prevailing wind and the shoreline, a few rounds of swash and backwash move the sediment along the shoreline.
Define deposition?
When material being transported is dropped on the coast.
Define sub aerial weathering?
The gradual break down of rock by agents such as ice, salt, plant roots and acids.
Describe the process of salt weathering?
Salt weathering is caused by saline water. This saline water enters pores or cracks in rocks at high tide. As the tide goes out the rocks dry and the water evaporates, forming salt crystals. As the salt crystals form they expand, exerting pressure on the rock - this causes pieces to fall off.
Describe the process of freeze thaw weathering?
Freeze thaw weathering occurs in areas where temperatures fluctuate above and below freezing. Water enters the joints in the rock and if the temperature drops below freezing the water freezes and expands. Over time repeated freeze thaw action weakens the rocks and causes pieces to fall off.
Describe the process of chemical weathering?
Chemical weathering is the breakdown of rock by changing its chemical composition. For example, carbon dioxide in the atmosphere dissolves in rainwater forming a weak carbonic acid. This acid reacts with rock that contains calcium carbonate, so rocks are gradually dissolved.
Describe biological weathering?
Biological weathering is the growth of plant roots into cracks in the rocks and widening them which can cause the rocks to break down.
Describe the process of mass movement?
The shifting of material downhill due to gravity. In coastal areas, it is most likely to occur when cliffs are undercut by wave action- this causes an unsupported overhang, which is likely to collapse.
Name 4 types of mass movement?
Landslides, slumping, rockfalls and mudflows.
Why are unconsolidated rocks prone to collapse?
As there’s little friction between particles to hold them together.
Why can heavy rain increase the likelihood of a collapse?
It can saturate the unconsolidated rock further reducing its friction and making it more likely to collapse.
Describe the process of runoff?
The flow of water over land can erode fine particles and transport them downslope.
