Paper 1 Coasts Flashcards
Why can coastal landscapes be viewed as systems?
Open systems - They have inputs, outputs and throughputs. They store and transfer energy and material.
What are the components of a coastal open system?
Inputs - kinetic energy from wind/waves, potential energy from deposition of material, thermal energy from the sun.
Throughputs - stores, longshore drift, nearshore sediment accumulations.
Outputs - wind erosion of beaches, marine erosion (hydraulic action) and evaporations.
What is dynamic equilibrium?
The system has a disturbance and then undergoes self-regulation to restore the original equilibrium.
Mudflats v salt marshes
Mudflats, usually found closer to the water, are prone to flooding from high tide so are harder to grow vegetation on. Salt marshes are further back and can grow more vegetation on.
What is a sediment cell?
A stretch of coastline in which sediment movement is largely self-contained. It is a closed system but impossible to be completely a closed system as fine sediment can still move through variations with tidal currents and wind direction changes, but it is largely closed because of large physical barriers like headlands. In the UK an example is Lands end.
What is weathering?
Breakdown or disintegration of rock in situ. It leads to the transfer of material. It is active at coasts where rock faces are exposed to elements and cliffs are kept fresh by regular removal of debris by the sea.
What is chemical weathering and what are the types?
Chemical weathering involves a chemical reaction where salts may be dissolved. Examples are carbonation, oxidation and solution.
What is carbonation in chemical weathering?
When rainwater absorbs carbon dioxide from the air, it forms a weak carbonic acid. When it hits rock, it reacts with calcium carbonate which is easily dissolved. It is more effective in winter as the cooler the rainwater, the more carbon dioxide is absorbed. This happens in limestone for example.
What is oxidation?
The reaction of rock minerals with oxygen to form rust leaving rocks more vulnerable to weathering.
What is freeze-thaw weathering and what is it an example of?
An example of mechanical weathering.
When water enters a crack in a rock, it freeze which expands the rock as the volume increases. This exerts pressure onto the rock and forces the crack to widen. Eventually fragments break away and collect at the base of a cliff for the sea to use in marine erosion.
What is salt crystallisation?
When salt water evaporates, it leaves salt crystals behind. These grow over time to exert pressure on the rock and can corrode rock.
What is biological weathering? Describe some examples of it.
Biological weathering is the breakdown of rocks by organic activity. E.g:
• plant roots growing into small cracks, widening the rock and breaking it up.
• birds digging burrows into cliffs.
• water running through decaying vegetation, making it become acidic and leading to chemical weathering
• marine organisms are capable of burrowing into rocks or secreting acids.
What is mass movement?
The downhill movement of material under gravity. It provides an input to sediment cells and provides rock to be eroded by the sea.
What is soil creep as mass movement?
Slow movement of individual soil particles downhill.
What is a mudflow?
Earth and mud flowing downhill over weak rock. Water pressure forces rock particles apart leading to slope failure. This is a form of energy within the slope system. They are often sudden and fast flowing.
Landslide meaning
Block of rock moving rapidly downhill along a surface. This block of material remains largely in tact. Triggered by land becoming lubricated, for example by earthquakes or heavy rainfall.
Rockfall explanation
Sudden collapse of individual rock fragments at a cliff face. Commonly associated with steep or vertical cliffs. Triggered by mechanical weathering. The scree that it forms at the base of a cliff is a temporary store within the coastal system.
Landslip
Slide surface is curved rather than flat. Commonly occurs in weak clays and sands. Sharp break up of slope to form a scar.
What are ocean currents?
Generated by the earths rotation, they act as a conveyor belt to transport cold and warm water across the globe. (Thermal energy) This helps to regulate global climate change as it counteracts the uneven distribution of solar radiation. They can modify local climate and influence weathering and other subaerial processes.
Describe warm and cold currents.
Warm - transfer heat from low latitudes to the poles. They have more energy.
Cold - move cold water from polar regions to the equator.
How can ocean currents affect coastal landscapes?
• Warmer currents have more energy so in some places can create more erosion and weathering.
•rising sea levels and changing climate patterns can accelerate coastal erosion and alter sediment budgets.
Describe the relationship between ocean currents and climate change.
•ocean currents regulate climate change by counteracting the uneven distribution of solar radiation on the surface.
•climate change can affect this, as waters warm up more there will be less of an even distribution and conveyor belts will not work.
What is a fetch?
The distance of open water which wind can blow over as it approaches a coastline.
Describe some terrestrial sources of sediment into the coastal system.
•Terrestrial and mass movement - from nearby cliff breaks or rock falls driven by gravity
•terrestrial and fluvial - rivers directly deposit sediment at the coasts.
•marine erosion - erosion of weak cliffs by high energy waves, can be amplified by storm surge events.
•longshore drift - supplying sediment from one coastal area to another.
•aeolian deposition - blowing fine sediment over locations.
Give an example of an offshore source of sediment.
Marine deposition - waves bringing sediment to shore from offshore locations.
What does beach nourishment do?
It is a human factor of sediment reaching the coastal system.
When a sediment budget is in deficit, it adds sand to the beach to maintain equilibrium to preserve the coastal environment.
How are tides formed?
The gravitational pull of the moon and sun.
What is a spring tide?
When the tidal range is high. The gravitational pull is at its strongest as the Earth , moon and sun are all aligned.
What is a tidal range?
The difference between high and low tide. A high tidal range would mean a large difference between the high water mark and low water mark, whereas low tidal range is the smallest difference between the water marks.
What is a neap tide?
The lowest range. The moon and sun are at right angles so the pull is weaker.
What is a sediment budget?
Added up inputs and outputs
What are waves?
The movement of water molecules in a circular motion carrying kinetic energy in motion and potential energy based on its height position.
Give 3 examples of an erosional landform
•headlands
•bays
•cliffs
•shore platforms
•geos
•blow holes
•caves
•arches
•stacks and stumps
Describe the process of abrasion
When waves armed with rock particles scour the land, rock rubbing against rock.
Describe the process of hydraulic action
When waves break against a cliff face and air and water gets trapped in cracks. As the wave recedes, the pressure is released and air and water suddenly expand and the crack widens.
Describe the process of attrition
Material gets swirled around by waves, breaking them down into smaller and more rounded rocks.
Describe the process of solution
Acidic water can dissolve rocks within
Describe a discordant coastline
The bands of rock are perpendicular to the coastline. Weaker rocks are eroded rapidly to form bays that are determined by the width of the bands of weaker rocks. The resistant rocks remain as headlands. The bays are larger on a discordant coastline.
Describe a concordant coastline.
Rocks lie parallel to the coastline. If the more resistant rock lies on the seaward side, it protects weaker rock behind from erosion. Small bays or caves are eroded at points of weakness in harder rocks. They don’t go very far back as they meet more resistant rocks.
Explain a horizontal bedded strata
The layers of rock lie on top of each other horizontally creating steep cliffs. Undercutting leads to rock fall and cliff retreat.
Explain a seaward dipping strata
The layers of rock lie at an angle, facing towards the coast. Undercutting removes the base support; rock layers loosened by weathering slide into the sea along the bedding planes.
What is lithology?
The physical and chemical composition of rock
Which rocks are more susceptible to chemical weathering through carbonation?
Chalk and limestone
What is the lithology of clay v basalt ?
Clay is weaker resistance of bonds so can be eroded more
Basalt has stronger resistance
How do you calculate the energy of a wave?
P = H squared T
What are spilling waves?
Gentle breaking and forward focus of energy with a strong swash
What are plunging waves?
Downward focus of energy with a strong backwash
What is percolation?
The movement of surface and soil water into underlying permeable rocks
What is the difference between porous and permeability?
Porous is gaps to store water for example air spaces in rocks
Permeable is water can flow through an access the spaces in the rocks.
Clay for example is porous but not permeable.
What is flocculation?
Saltwater causes clamping of clay particles transported by rivers which are heavier to transport
Why may deposition occur? Give three examples.
• sediment exceeding available energy for transportation
• percolation of water on a beach during backwash
• loss of energy due to shelter, e.g. estuary
• flocculation
• opposite directions of fluvial flow and wave action causes energy loss
• aeolian and deposition due to surface friction
What is a landward dipping strata?
Rocks, lay at an angle facing towards the land. Rocks loosened by weathering and wave action are difficult to dislodge. The slope profile is gradually lowered by weathering and mass movement.
How can algae influence biological weathering?
Marine organisms like Algae can accelerate weathering. Algae releases CO2 when photosynthesis is not taking place when this mixes with seawater it makes it more acidic results and high rates of chemical weathering.
Summarise the points in the formation of a shore platform
•sea creates a wave cut notch in the bottom of a cliff by hydraulic action and abrasion (describe those erosion processes)
•eventually the weight of the unsupported cliff collapses as a rockfall
•the platform left behind as cliffs retreat and the waves transport material from the base of a cliff is a shore platform - (usually 0-3 degrees, max width 500m)
•at low tide, physical and biological weathering occurs
• low tidal range - cliff at low water mark and ramp at high water mark as waves are concentrated in one place for longer
•high tidal range - smooth ramp as erosion is spread
Why is the maximum width of a shore platform 500m?
Friction between the waves and the platform cause the wave to break at the start of the platform rather than the base of the cliff so undercutting slows and stops. Research suggests that shore platforms have to reach 500 m before this happens.
What are geos and how are they formed?
Narrow steep sided inlets that occur at lines of weakness that are eroded more rapidly
May also be associated with the collapse of a cave roof
Caves, arches, stacks and stumps.
Often develop around a headland. Due to wave refraction, energy is concentrated on the side of the headlands. Any weaknesses are prone to erosion - forming a cave. If may enlarge to the other side or join another cave an arch is formed. Continued erosion and weathering weakens it support and it may collapse to form a stack. Further erosion of the stack may collapse or even more leaving a stump.
(Describe erosion, weathering and mass movement processes)
What are three main sources of beach material?
Cliff erosion (retreat from abrasion leading to rockfall)
Rivers (fluvial sediment)
Offshore
What are spits?
Long, narrow beaches of sand or shingle that are attached to land at one end and extend across a coastline.
What are the factors of a spit?
Wind direction, drift aligned for long shore drift
• low energy waves so deposition occurs
•sediment supply
• changing direction of a coastline
What is a salt marsh? Give some key points
Features of low energy environments (e.g behind a spit where it is sheltered)
Vegetated areas of deposited sand and silt which experience inundation daily
Salt tolerant plants grow helping to trap sediments
Fewer plant species can survive in saline conditions but further inland, conditions are not as saline so greater variety of species
Apart from long shore drift, how else may on shore bars be formed?
Sea level rise (onshore movement of sediment)
Why do sandy beaches have gentler gradients?
Less percolation than shingle beaches and a stronger backwash
Which types of waves create flatter beaches?
High energy waves as sediment is moved offshore
What is backwash?
The return of the wave back to sea due to gravity
What is the primary factor contributing to sea level rise?
Global warming, primarily due to melting ice caps and thermal expansion of seawater.
True or False: Sea level rise can lead to increased coastal erosion.
True
Fill in the blank: The process by which coastal areas become submerged due to rising sea levels is known as _______.
coastal inundation
What are two major impacts of rising sea levels on coastal landscapes?
Increased flooding and loss of habitat.
Which coastal feature is most vulnerable to sea level rise?
Estuaries
What is the term for the gradual sinking of land that can exacerbate the effects of sea level rise?
Land subsidence
True or False: All coastal areas will experience the same rate of sea level rise.
False
What is Eustatic sea level change?
A worldwide rise or fall in sea level
What is isostatic sea level change?
A relative rise or fall of land.
What is thermal expansion
The expansion of water molecules due to increased temperatures and therefore sea level rise.
What is a submergent landform? Give an example
Landforms from a relative rise in sea level. E.g fjords, rias, shingle beaches.
What is an emergent landform? Give an example
Landforms from falling sea level.
Raised beaches/marine terraces, abandoned cliffs.
Which process leads to the formation of submergent landforms?
Rising sea levels or land subsidence.
Multiple Choice: Which of the following is a characteristic of emergent landforms? A) They are underwater B) They are above sea level C) They are flat
B) They are above sea level.
True or False: Submergent landforms can include features like estuaries and fjords.
True.
Name one natural process that can lead to the submergence of landforms.
Rising sea levels due to climate change.
Fill in the blank: __________ is an example of a submergent landform created by glacial activity.
A fjord.
What is the difference between a sea level rise and land subsidence in terms of submergent landforms?
Sea level rise increases water depth over land, while land subsidence is the sinking of land itself.
Reasons for uneven sediment sizes on a beach
Mass movement, like rock fall where rocks of different sizes enter the coastline.
Different geology, harder or easier to erode so larger or smaller particles
High wave energy leads to more cliff erosion so more cliff collapse and uneven rock pieces.
Some sediment may have travelled further due to long shore drift and have been eroded more on the way due to attrition
How may tombolos be formed?
The swash of Longshore drift carrying sediment continuously even when a coastline ends until it reaches an island. Prevailing wind direction plays a large part
Why is sediment eventually deposited into a tombolo?
From a loss on energy, due to a river estuary or island providing shelter from wave action. Sediment may build up in this low energy area from deposition as it is deposited it becomes shallower and increases friction to further deposit sediment.
How can climate change influence raised beaches?
• during the interglacial periods, the raised beaches would have been a shore platform being eroded by abrasion at high tide at low tide, biological weathering occurs where organic acids from marine organisms erode the rock.
•may increase precipitation and when this water runs through vegetation on the rock, organic acids will enable weathering and lead to chemical weathering.
• hotter temperatures will also lead to salt crystallisation if the raised beaches is exposed where as salt water evaporates it leaves salt crystals behind which can grow over time and exert pressure on the rock, corroding it.
What are raised beaches?
Emergent landform formed by the fall of sea level. They are areas of former shore platforms left at higher level than present sea level.
