Coastal processes
- Created by: rchapman99
- Created on: 12-11-17 00:21
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- There are 6 main ways waves erode he coastline
- Corrasion
- Bits of rock and sediment transported by the waves smash against rocks and cliffs, breaking bits off and smoothing surfaces.
- Hydraulic action
- Air in cracks in cliffs is compressed when waves crash in. The pressure exerted by the compressed air breaks off rock pieces.
- Cavitation
- As waves recede, the compressed air expands violently, again exerting pressure on the rock and causing pieces to break off.
- Wave quarrying
- The energy of a wave as it breaks against a cliff is enough to detach bits of rock.
- Solution
- Soluble rocks dissolved by the seawater.
- Attrition
- Bits of rock in the water smash against each other and break into smaller bits.
- Coastal processes
- Transportation is the process of eroded material being moved.
- Solution: substance that can dissolve are carried along in the water, e.g. limestone is dissolved into water that's slightly acidic.
- 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.
- Suspension: very fine material, such as silt and clay particles, is whipped by turbulence and carried along in the water; most eroded material is transported this way.
- Traction: very large particles, e.g. boulders, are pushed along the sea bed by the force of the water.
- 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.
- Sub-aerial weathering occurs along the coastline
- Sub-aerial weathering is the gradual break down of rock by agents such as ice, salt, plant roots and acids. Weathering weakens cliffs and makes them more vulnerable to erosion.
- Wetting and drying
- Some rocks contain clay; when clay gets wet, it expands and the pressure caused by this breaks fragments off the rock.
- Chemical weathering
- The breakdown of rock by changing its chemical composition.
- Freeze-thaw weathering
- Occurs in areas where temperatures fluctuate above and below freezing; water enters the joints and crevices in rocks; if the temperature drops below 0 degrees, the water in the cracks freezes and expands; over time, repeated freeze-thaw action weakens the rocks and causes pieces to fall off.
- Salt weathering
- Caused by 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 which causes pieces to fall off.
- Mass movement is when material moves down a slope
- Slides
- Material shifts in a straight line.
- Slumps
- Material shifts with a rotation.
- Rockfalls
- Material breaks up and falls.
- Mudflows
- Slides
- Transportation is the process of eroded material being moved.
- Corrasion
- Deposition is when material being transported is dropped on the coast.
- Marine deposition is when sediment carried by seawater is deposited.
- Aeolian deposition is when sediment carried by wind is deposited.
- Deposition is the process of dropping eroded material
- Coastal processes
- Transportation is the process of eroded material being moved.
- Solution: substance that can dissolve are carried along in the water, e.g. limestone is dissolved into water that's slightly acidic.
- 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.
- Suspension: very fine material, such as silt and clay particles, is whipped by turbulence and carried along in the water; most eroded material is transported this way.
- Traction: very large particles, e.g. boulders, are pushed along the sea bed by the force of the water.
- 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.
- Sub-aerial weathering occurs along the coastline
- Sub-aerial weathering is the gradual break down of rock by agents such as ice, salt, plant roots and acids. Weathering weakens cliffs and makes them more vulnerable to erosion.
- Wetting and drying
- Some rocks contain clay; when clay gets wet, it expands and the pressure caused by this breaks fragments off the rock.
- Chemical weathering
- The breakdown of rock by changing its chemical composition.
- Freeze-thaw weathering
- Occurs in areas where temperatures fluctuate above and below freezing; water enters the joints and crevices in rocks; if the temperature drops below 0 degrees, the water in the cracks freezes and expands; over time, repeated freeze-thaw action weakens the rocks and causes pieces to fall off.
- Salt weathering
- Caused by 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 which causes pieces to fall off.
- Mass movement is when material moves down a slope
- Slides
- Material shifts in a straight line.
- Slumps
- Material shifts with a rotation.
- Rockfalls
- Material breaks up and falls.
- Mudflows
- Slides
- Transportation is the process of eroded material being moved.
- Both types happen when the sediment load exceeds the ability of the water or wind to carry it. This can be because sediment load increases, or because wind or water flow slows down. Wind and water slow down for similar reasons:
- Flow becomes turbulent if water or wind encounters an obstacle, flow becomes rougher and overall speed decreases.
- Friction increases - if waves enter shallow water, or wind reaches land, friction between the water/wind and ground surface increases, which slows down the water/wind.
- If the wind drops, wave height, speed and energy will decrease as well.
- Coastal processes
- The shifting of material downhill due to gravity.
- Occur when cliffs are undercut by wave action which causes an unsupported overhang, which is likely to collapse.
- Unconsolidated rocks are prone to collapse as there's little friction between particles to hold them together.
- Heavy rain can saturate unconsolidated rock, further reducing friction and making it more likely to collapse.
- Runoff can erode fine particles and transport them downslope.
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