Coastal Processes Flashcards
Define weathering
The breakdown of rocks in situ (weakens rocks and makes them easier to erode)
Define physical weathering
The breakdown of rocks in situ with no chemical change.
Define chemical change
The breakdown of rocks by a chemical change.
Define biological weathering
The breakdown of rocks by plants/animals
Define accretion
The build up/deposition of material
Name the 4 main processes of erosion
Hydraulic action
Abrasion/corrosion
Attrition
Solution/corrosion
How does hydraulic action work?
Hydraulic action occurs when the force of the waves compresses air pockets in coastal rocks and cliffs. The air expands explosively, breaking the rocks apart.
How does abrasion work?
Rocks and pebbles flung by waves against the cliff wear it away.
How does solution work?
Rocks dissolve in the water and are taken away
How does attrition work?
Eroded rock particles themselves are worn down, becoming smaller and more rounded.
What are the factors affecting rate of erosion on a coastline?
- Amount of marine energy (waves) - made worse on a spring ride - sea walls less effective and waves les affected by shore
- Geology of the area - structure and lithology
What is lithology?
Lithology refers to the physical properties of a rock such as its resistance to erosion.
The lithology of a coastline affects how quickly it’s eroded.
What are concordant coasts like?
Concordant coasts have alternating layers of hard and soft rock that run parallel to the coast. The hard rock acts as a protective barrier to the soft rock behind, preventing erosion.
If the hard rock is breached, the softer rock is eroded and a cove can form.
What is a discordant coast like?
Discordant coasts have layers of hard and soft rock running perpendicular to the coastline. At areas of soft rock, there is more erosion causing bays. At areas of hard rock, there is less erosion causing headlands which can then form caves, arches, stacks and stumps.
Freeze thaw
Physical
When water freezes within the rock, it attracts small particles of water, creating increasingly large ice crystals. It slowly widens the rock joints and causes rock to shatter from the main body.
Salt crystallisation
Physical
Slightly saline water enters pore spaces in rocks, evaporates and leaves salt crystals to form. The crystals become larger and exert stress on the rock, causing it to disintegrate
Water layer weathering
Physical
Water pushes rock layers apart
Exfoliation
Physical
Where cracks develop parallel to the surface. Sheeting cusses the outer layers of rock to peel away. Hot and cold wears the rock away.
Pressure release
Physical
Rocks developed under considerable pressure weaken when they are exposed to the atmosphere due to a release of pressure.
Oxidation
Chemical
When a substance reacts with oxygen. Rocks are weakened and crumble easily.
Reduction
Chemical
Removal of oxygen. Takes place in conditions of excess water.
Hydrolysis
Chemical
Chemical breakdown of a substance when combined with water.
Carbonation
Chemical
Water mixes with carbon dioxide to make carbonic acid. Carbonic acid reacts with minerals in rocks, and dissolves rock.
Hydration
Chemical
Water is taken into the rock and it swells
Biological
Biological
The roots grow along bedding planes/ extend into joints and widen them until the rock becomes detached. Burrowing animals may also do this.
Slides
Rapid movement of rock along bedding planes, which falls at the angle of dip.
Slumps
They take place across bedding planes. It’s rapid. It happens on unconsolidated geology, e.g. Clay
Rockfalls
When an overhang on a cliff breaks away and rocks fall down.
Mudflows
Debris which quickly flows down a hillside like a river. Not much water is needed.
Define mass movement
Can be a response to a trigger event.
The down hill movement of weathered material under the force or gravity. Friction is the opposing force which maintains the slope.
What are all the things that mass movement can be/do? 4 things
- works along weathering and erosion
- can be very fast or slow
- can be dry or wet
- can be a small amount of particles or huge volumes
