Coastal Landscapes and Change - Coggle Diagram
Coastal Landscapes and Change
Features of Coastal Zones
The coastal zone in which sediments are moved around between the Beach and sea.
Consists of ?
Contains multiple sediments/Waves currents and tides as well. It is divided into backshore/foreshore/nearshore and offshore
-Area deeper water, beyond the point at which waves begin to break. Friction of waves and sea bed causes the shape to form.
-Shallow water beyond the low tide. Has two parts going towards the coastline, the breaker zone where waves break followed by the surfer zone where surfers ride waves hence the word "surf" in "surf zone".
-Area between high and low tide.
-Area above the high tide mark, affected by wave acction, only during a storm event.
Structure of Coastal Zones
(Cracks in the crust)
(Fractures dividing rocks)
(Earths crust creating overlapping ridges)
Types of Coastlines
-Bands of rock and layers run perpendicular to the coastline. Usually geology alternates between strata of hard and soft rock. headlands and bays occur at these coastlines as erosion resistance is different between rocks, so they wear at different rates.
-Where beds and layers of rock are folded into ridges that run parallel to the coast. Usually they have the same type of rock along their length. E.g. Dalmatian coastline(Croatia)
Coastal Recession and Stability
Types of Rock
-formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in either a planet's mantle or crust.
- arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock is subjected to temperatures greater than 150 to 200 °C and, often, elevated pressure of 100 megapascals
-accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place.
The harder the rock the more impermeable it is, lower the rate of erosion and coastal recession.
Erosion occurs at the foot of cliffs, creating notches. Material above the notch collapse and is washed away. Repeated collapsing causes cliffs to further retreat. Rates depend upon the strata of cliffs.
Vegetation stabilises sandy coastlines,provides habiutats and flood defences.
=A layer or a series of layers of rock in the ground.
Coastal System Landscapes and Processes
-Influence beach morphology and sediment profiles in the short and long term.
Created in storm conditions when wind is powerful and waves are high and dangerous.
Low wave energy
Erosion processes are influenced by five key identifiable factors
- Certain characteristics can make a coastline more erosional.
- larger the wave then typically the more erosion will occur and vice versa.
-Narrow beaches provide little protection. The waves break later so they're more powerful.
Depth of the Sea
-deeper it is then the less friction created towards the coastline, so it is less likely of large waves to build
Types of Erosion
- water dissolves minerals from the rock and wash it away.
-Eroded water particles scrape and rub against the rocks, removing small pieces.
-Waves crash into the rock compressing the air in the cracks and adding pressure. This repeated compression makes the rocks break away and shatter.
-Eroded particles in the water collide with each other and break into smaller fragments. This causes their edges to become rounded off as they rub together.
Wave cut Platforms
-Narrow base left behind as the cliff retreats.
-Through serious hydraulic action and abrasion, a coasts can form caves and eventually, through the continuous erosion of rock, the caves develop into arches which then develop even further till they cannot physically stand, so the roof of the arch gives in and leaves a stack(large and tall section of rock)behind. This is then further eroded, and eventually the stack will fall and a stump is al that remains.
Wave cut notches
-Erosion occurs at the bottom of the structure of a cliff and creates a gap within itself.
Types of Coastlines
-Sediment is transported along the coastline via processes such as longshore drift.
-Sediment moves along the coastline up and down the beach with little lateral movement.
Sediment Transport and deposition
the Coast is dependant on what ?
Bar/Barrier Beach Formation:
Ridge of material that is connected at both ends of the mainland. If longshore drift continues along the coastline then it will continue to form a bar.
Where two spits extend out in opposite directions, from both sides of an estuary towards the middle. Longshore drift in both directions. E.g. Bournemouth Estuary.
When the shape of the coastline changes substantially and longshore drift continues to move sediment in a zig zag pattern across the coast. This transports material out at sea. As the strength of the drift weakens away from the coastline so deposition occurs. Since the flow of the river at the estuary is stronger then sea then the spit usually stops before and estuary. Refraction around the spit curves in a hook so salt marshes develop behind it. Spits are eroded by the sea and wind.
Found on coasts between high water mark(highest point of the land which sea level can reach) and low water mark. They form due to constructive waves depositing sand and shingle.
Ridges of offshore sand, running parallel to the coast in an offshore zone. They form from eroded sediment by destructive waves carried seawards by the backwash. Sediment is offshore, where the orbit of water particles cease to reach the seabed, halting transport offshore.
Triangular shaped headlands. When longshore drift converges at the boundaries. Sediment is deposited out at sea by both currents creating a triangular shape area of deposited material. E.g. Dungeness, Kent
Ridge of material which extends for the mainland out to a island, this ridge is called a tombolo. E.g. Chesil Beach(South England).
Land based Processes which typically occur above the water level. They shape the land.
-Downward movement of material caused by gravity.
Rocks that re jointed or have bedding planes parallel to the slope are susceptible to landslides. Increase in water = reduction in the friction. Slabs of rock with the slide over the underlying rock, called a slip/plane.
Occurs when mechanical weathering, like freeze thaw, break large chunks off the cliff away. Cliff has to be at an angle of 40 degrees or more. Material hat breaks off is called scree and bounces down the cliff to the bottom.
Movement is around 1-5cm a year. Occurs in areas of permafrost. The top layer of soil thaws in warmer summer but layer below remains frozen(permafrost).The layer(surface0) becomes saturated as frost melts and flows over the sub soil and rock below.
Heavier rain causes reduction in friction and thus turns inti mud and flows slowly over the bedrock material will become al jumbled up and fall down the cliff.
-Slower form of mass movement, but it is almost continuous. Soil moves slowly down a hi due to gravity and added weight caused by water, creating ridges of soil(Terracettes, long low ridges that follow the contour of the slope).
Consists of saturated conditions/Forms of terraced cliffs/Causes rotational scars as of slumping/Moderate to steep slopes/Difference between slumping and sliding is that there is rotational movement in slumping.
-Decay and degradation of rock in situ.
- Materials such as limestone and chalk which are relatively weak rocks, can be exposed to water with a higher acidity or salt content and cause a chemical reaction which erodes the rock.
-The effect of biological life, e.g. tree roots/animal burrows and nests, can cause the land to erode faster as it weakens the soil of coastlines.
- Two types of hard weathering.
- Water seeps into the cracks and fractures the rock, water then freezes and it expands around 9%,which wedges the rock apart. This processes repeats and eventually weakens the rock to the pint of breaking.
- Salt crystals harden on certain rock types and this in tern widens joints in cliff.
What does Mass Movement cause ?
Talus Scree Slopes:
The loose debris accumulated at the foot f a cliff.
Terraced Cliff Profiles:
Eroded rocks create ridges within the cliff.
Material deposited from rotational slumping.
Sea level Change
Long term Sea level change can either be....
When ice melts and returns to the oceans, increasing the volume of water present in the sea. Usually this is accompanied by thermal changes which mainly melt ice. Estatic = fall in sea level and Eustatic = rise in sea level.
Involves the downward movement of land, causing localised sea level rise. Land can be stressed(compressed) downward from
(sinking of the land)and
(accumulation of layers pushing down on the earth
It has caused different types of coastlines
Other reasons for sea level Change
Anthropogenic factors such a s global warming
causing eustatic sea level change as ocean temperatures rise, particles expand, taking up more space in the ocean basin. So sea levels rise. Melting ice also adds to the amount of water in the sea. However NOTE ,like if you add a cube of ice to water, the melted ice will not rise the sea level as the volume of ice is replaced by the equivalent volume of meted water.
Sea floor Spreading:
Larger platforms for water to sit on, tectonic activity contributes to the ocean basin shape. If basins get smaller the volume of water decreases and sea level rises.
Isostatic (localised) sea level change can also be effected by
On pate boundaries, forcing the oceans to be at a higher platform than the and.
Caused by a mix of factors both human and Physical
Holderness retreats by 1.8m of and per year
as of easily erodible rock types and narrow beaches, alongside the building of coastal defences which makes narrower and more exposed beaches.
Rates of recession depend on:
Risk Of Coastal Flooding
Storm Surges, tropical cyclones, and depressions
can cause severe flooding. Leading to multiple Social, economic and environmental impacts.
Coastal Floods in the Maldives
causes loss of tourism ,beach's, soil and freshwater whilst disrupting the fishing industry and damaging homes.
is likely to increase the extreme weather. However it is the size and power of the weather that will worsen and increase not the frequency. However the future is clouded and may uncertainties remain .
Current Examples of Consequences of Coastal recession
-in 2007 made 9 million people homeless and 1000 people died from drowning an water born disease. It suffers worse from the occurrence of cyclones and monsoon rains. Its around 2 thirds less then 15meteres above sea level. So it is very low-lying and is very exposed to serious floods. It may one day become completely inundated(overwhelmed) by floods in the future yet little is known about this "future".
-In Feb. 2014 caused severe erosion, leaving Kimmeridge Clay bedrock exposed. The last time this happened was in 1989.The storm forced the. closure of main roads A354,impating business and local life.
We consistently keep seeing a
rise in environments refugees
from coastal areas, such as those living in Bangladesh and Tuvalu.
Management of Coastlines
Sand and shingle are added to a beach to make it wider, increasing the distance a wave travels before reaching the cliffs. So the waves have less general energy and erosive power.
Cliff Regrading and Drainage:
Inserting pips within a cliff to remove excess water. Cliff is still open to wave erosion but technique prevents mass movement and clay build-up.
Widen the beach/Dunes to dissipate wave energy.
Loose stone create a foundation for a breakwater. Reducing energy of the waves.
Concrete structures built along the base of cliff to absorb the impact and wave energy. Despite high set up costs, the concrete walls ned low maintenance.
Concrete walls that break incoming waves so they are less erosively powerful. During storms, these are easily destroyed and they are also visually pollutive.
Protect cliffs, land and buildings from erosion but are very expensive and waves can become more powerful and curved walls reflect the energy back into the sea. They can erode and need high maintenance.
Low wall/barrier that extends out into the sea to stop the movement of beach material along the coast, specifically stopping longshore drift. Yet its unattractive and costly.
meet the needs of today without comprising the needs of future generations.
Sustainable management is designed to cope with future threats but implementation can cause conflict.
Holistic Integrated Coastal Zone Management (ICZM)
Global strategies are being developed so they are sustainable and use ICZM techniques. It regards all aspects of the coastal zone in an attempt to achieve sustainability. This creates winners and losers as some ca achieve effective management and others cannot. Political judgements require cost benefit analysis and environmental impact assessment which an spark conflict as multiple procedures and players (homeowners, authorities etc.)are involved.