Geography Coastlines topic, AQA A LEVEL PART 1

Topics 1-4 including case studies

Coastal environments definition

Coats are dynamic environments, shaped by the interaction of marine, sub-aerial, and aeolian processes, within a closed system.

Why are Coastal environments significant?

As 50% of the world’s population lives within 150km of the coast, and the ten most populous cities reside next to the coast.

Isolated system definition

No inputs/outputs and largely theoretical

Closed system definition

Inputs and outputs confined within a sediment cell, with limited exchange

Open system definition

Exchanges both energy and matter with the surroundings.

Sediment Cells definition

Selection of a coastline in which characterises a closed distinct system

How many sediment cells are there?

There are 11 sediment cells in England and Wales

What is a feedback loop?

An accruing change in a system that triggers further changes

Positive Feedback loop

When one action increases the original action, that creates a feedback loop

Negative feedback loop

When one action decreases the original action, creating a feedback loop

When is dynamic equilibrium achieved?

When an environment is eventually maintained within a ecosystem if negative or positive feedback loops aren’t greater than the equilibrium

What is wind as a source of energy along a coastline?

its a primary source of energy formed by the contrasting air pressures offshore the coast, that transports sediment and deposits, along with eroding a coastline overtime.

How are waves caused?

By prevailing/offshore winds over a large fetch distance towards a coastline

What is a destructive wave?

When a wave erodes at a greater rate than depositing material along the beach, as it generates more backwash than swash

What is a constructive wave?

When a wave deposits at a greater rate than eroding material along the beach, as it generates more swash than backwash

What is a current?

Permamenmt or seasonal movement of water, that transports and redistributes energy along a coastline that is formed by tides, winds and thermohaline circulation

What are the types of currents?

Longshore currents, are formed by the movement of water and sediment parallel to the coast, Rip currents carry water away from the shore, Upwelling currents move cold water to the surface

What are the Tides?

They are the periodic rise and fall of sea levels caused by gravity of the moon and the sun

When do high tides occur?

when eustatic levels reach the local max

When do low tides occur?

when eustatic levels reach the local minimum

What are the significance of tides?

They impact how far waves reach up a beach and what parts of a cliff are exposed to hydraulic action

What are spring tides?

Occurs near new and full moons when they create larger tidal ranges

What are neap tides?

Occurs near one quater and third quarter moons when they create smaller tidal ranges

What is wave refraction?

the bending and distortion of wave fronts when waves approach an uneven coastline

How does wave refraction occur?

When waves approach a coastline contain headlands and bays and the shallowe waters slow the waves speeds due to friction. As a result waves travel faster ind deeper water cause the wave in the front to bend. Due to this, waves become more concentrated around headlands and more dispersed around bays. Which orthogonal lines represent this direction of wave energy.

What are the characteristics of high energy coastlines?

High wave frequencies, height and prevalent destructive waves, often correlated with strong prevailing winds and a long fetch.

Consequences of high energy coastlines

Lower sediment stores and deposition, higher erosional processes, and more frequent storm patterns

What are the characteristics of low energy coastlines?

low wave frequencies, height and prevalent constructive waves, often correlated with little wind and a short fetch, where there are less frequent storms.

What are the sources of sediment along a coastline?

coastal erosion of landforms, rivers, streams, estuaries and offhshore and biogenic sediment sources

What is a coastal cell budget?

Its the balance between inputs and outputs of sediment

What is a positive cell budget?

Inputs of sediment exceeds outputs, where stores increase and depositional landforms develop

What is a negative cell budget?

outputs of sediment exceeds inputs, where stores decrease and erosion becomes more frequent

What is a balanced cell budget?

Where processes are at a dynamic equilibrium and limited changes occur

What are differences between marine and sub-oriel processes

Marine processes operate along a coastline and are connected to the sea, that is infeuceced by waves currents and tides, sub-aerial processes operate along a exposed are of land that results in weathering, massmovemnt and run off

What is marine erosion?

Its the wearing away of rocks and sediment by waves

What is hydraulic action?

HA forces water and compressed air into cracks within rocks that exert repeated pressure that widens cracks over time and eventually destroying it.

What is wave quarrying?

WQ is large scale more powerful HA that exploits lines of weakness to detach and remove rock

what is abrasion

AB is when rocks and sediment transports and is carried by waves and collide against each over, corrosion is the process where rocks are colliding along a cliff

What is attrition?

When sediment/rocks collide with one another becoming more rounded over time

What is Solution

when soluble rocks and minerals dissolve within seawater gradually chemically eroding the rock over time

What factors effect marine erosion?

Fetch, sea depth

Why does sea depth effect marine erosion?

because it influences ave refraction which leads to steeper or shallower waves that effects the energy of waves due to friction.

Why does fetch effect marine erosion?

As it allows a longer distance for the waves to accumulate energy due to the more time provided.

What is lithology?

refers to the characteristics, composition, strength, resistance and permeability of rock that responds differently to types of erosion, that results in differing impacts and differential erosion the may occur due to variations in the resistance of rock

What is marine transportation?

The movement of sediment by waves.currents and transferring stores of sediment there are 4main types traction, saltation, suspension, solution

what is transportation by traction?

Large heavy rocks that roll along a seabed or are dragged

what is transportation by saltation?

smaller sediment rocks that bounce or hop along the seabed

what is transportation by suspension?

when fine particles or silt are carried within the water

what is transportation by solution?

when minerals and chemicals are dissolved within the water

What is longshore drift?

littoral drift occurs when sediment is travelled along a beach at a zig zag direction often at an angle, when prevailing winds approach a drift aligned beach; gradually transporting sediment.

What is mass movement (sub-ariel processes)

the downhill movement of weathered rock, soil, or material under the influence of gravity, that transfers the material from the top of the cliff to the base

what are the four types of movement?

Creep, flow, slide and fall

What is soil creep

the very slow downhill movement of soil downhill due to the repeated wetting and drying or repeated cooling and heating

What is Soliflucation?

The slow movement of waterlogged soil over an impermeable frozen layer of soil

What is mudflow?

the rapid movement of waterlogged sediment down a slope

what is a landslide?

when massmovment of rock and soil travels downhill very rapidly, often triggered by heavy rainfall, and erosion due to the changes in stability.

What is rockfall?

When pieces of rock detach and fall under gravity

What is rotational slump?

Occurs when material moves downhill along a curved slip surface that rotates backwards as it travels.

Landslides

are also the general term for material moving down a slope

What is weathering?

the breakdown or decay of rock in situ that weakens rocks promoting erosion

What are the three types of weathering?

Mechanical, Biological, Chemical, weathering

What is mechanical weathering?

The break down of rocks into smaller pieces without changing chemical composition

What is freeze thaw weathering?

When water from rain enters cracks within rocks, and as the temperature decreases, it freezes and expands when it thaws exerting pressure on the surrounding rocks, widening the cracks around the rock

What is salt crystalization weathering?

When salt water enters rocks cracks and evaporates leaving salt behind the rock, as the crystals accumulates it exerts pressure

What is Wetting and Drying weathering?

when some rocks absorb water and expand, they tryout and shrink, repeatedly expanding it weakens material over time due to the decaying of rock

What is Biological weathering?

when living organisms contribute to the breakdown of rock

What is plant weathering ?

When roots grow into rocks and as a result absorbs the materials widening the rocks

What is Chemical weathering?

when the change of a rock chemical status as the result of chemical reactions weathers the rocks

What is carbonisation weathering?

when carbon dioxide dissolves into rainwater to form weak carbonic acid that especially reacts with calcium carbonate in limestone dissolving the rock

What is oxidisation weathering?

when oxygen reacts with iron minerals and oxides form chaining the chemical composition within the rock

What is runoff?

the flow and movement of water created over land towards the coastline due to the influence of gravity

TOPIC TWO- As coastlines develop

What is a landscape?

the overall appearance and chracter of an area

what is a landform

the specific physical feature created by coastal processes

what are the types of coastal erosion processes?

Hydraulic action, wave quarrying, corrosion, abrasion and solution/corrosion

How do headlands and Bays form?

Alongside disconcordant coastlines, where coastal erosion processes erode soft rock at a faster pace than hard rock, which bays form at the soft rock and headland form at the sides of a bay. Wave refraction emphasises this

When do disconcordant coastlines occur

when bands of soft and hard rock run at an angle to the coast, differential erosion form headlands and bays due to alternating geology.

When do concordant coastlines occur

when bands of soft and hard run at parallel to the coast, as a result forming fewer headlands and bays

What are wave cut platforms?

erosional landforms that develop when waves attack the base of the coast

What is the process that produces a wave cut platform

When hydraulic action erodes the base of a cliff, most at high tide, this then undercuts the rocks surface forming a wave cut notch, concentrated erosion then deepens and enlarges the notch, further undercutting. Overtie, prolonged erosion creates cliff retreat as material is washed away, leaving a wave-cut platform, usually not smooth.

How does cliff retreat occur?

when preloved erosion and weathering weakens the cliff as a result the edge moves inland repeatedly

What is the shape of a cliff shaped by?

Geology, rock hardness and the arrangement of strata

How do steep cliffs develop?

When rocks are relatively resistant to erosion, or in high energy environments

What is rock strata?

the hardness within the composition of rock

What is Scree?

the collection of loose fragments. of rocks and the accumulation at the base of a cliff or steep slope, that form when weathering and gravity causes pieces of rock to break away, where it is left at the foot of a cliff

What are Geos?

Narrow steep sided inlets inside a cliff, that from when waves exploit a weak joint or crak along a wall of rock, which is expanded when erosion continues

what are blowholes?

when erosion continues upwards through a cave or geo until it reaches the land above, forming through hydraulic action

what are arches?

A headland which has been eroded over time, where a cave has expanded below, which opposite sides meet

what is a stack?

when an arch collapses leaving a column of hard rock isolated from the shore

what is a stump?

when the low remmant of rock is left after a sea stack has eroded further and parts collapsed

What order does the formation of Geos/caves, Arch, stacks and stumps look like?

Geos/caves, Arch, stacks and stumps

What is an example of a headland landform?

Durdle door, Dorset England

What is coastal morphology?

the shape and physical form of the coasts, including slopes headlands and bays

what is deposition?

the process which sediment is dropped as the energy decreases to the point it cannot longer be transported

what is a beach?

a depositional landform that is made from accumulated sediment which is dynamic via the environment

what is beach accretion

the enlargement of a beach as sediment is deposited

what is beach excavation?

the removal of beach sediment and material

What are swash and drift aligned beaches?

the process that classifies beaches according to how waves approach the coast

what is a swash aligned beach?

when waves approach parallel beach, which influences and aids wave refraction, as shallower waters help concentrate parallel waves, Longshore drift then occurs according to wave direction

what is a drift aligned beach?

when waves approach at an angle, and sediment, up a beach from longshore drift