Coastal Systems and Landscapes General AO1 - AQA Geography A-Level

Define an Open System

There are inputs and outputs of sediment through a system boundary

Define a Closed System

There are inputs and outputs of energy but not matter through a system boundary

Define an Isolated System

There are no inputs or outputs of energy or matter. No interaction with the system boundary.

At all spatial scales, the coastal system is a ___ system?

Open system (Energy and matter can enter and leave)

What are some of the key inputs in the coastal system?

Water, sediment, solar insulation

Where do the inputs of energy and matter in the coastal system originate from?

Rivers, Cliffs
Energy from wind, waves, tides and currents

What are the processes in the coastal system?

Longshore drift
Weathering
Erosion
Waves
Prevailing Wind
Deposition
Mass Movement

What are the key storages in the coastal system?

Beaches
Headlands
Bays
Spits
Tombolos
Bars
Salt Marshes

What are the key outputs from the coastal system?

Water, Sediment and Energy.

Define Positive Feedback Cycle

A set of processes that amplify an effect over time

Define Negative Feedback Cycle

A set of processes that nullify / cancel out an effect over time

Give an example of a negative feedback cycle in the coastal system

1) Sediment eroded from a beach
2) Sediment deposited forming an offshore bar
3) Waves forced to break earlier, dissipating their energy
4) After the storm, waves return offshore bar sediment back to the beach.

What is the difference between a landscape and a landform?

A landscape is the key physical features of an area. Whereas a landform is the shape and character of the land surface and the interaction of physical processes.

What is a small scale coastal system and what happens if inputs and outputs are different?

A small scale system is a beach

If the inputs are greater, the beach grows in height, width or length. If the outputs are greater, it will shrink.

Describe a large scale coastal system

A sediment (littoral) cell. Often bounded by headlands, sediment typically recycled in the cell but can be transferred between cells.

Give some examples of wave dominated landforms

Shore Platforms
Cliffs
Beaches
Spits
Tombolos

Give some examples of tide dominated landforms

Mudflats
Sandflats
Salt Marshes
Mangroves
Deltas

Give an example of a wind dominated landform

Sand Dunes

Where is solar insulation most concentrated?

The Equator

Which pressures does air move from (Hint: ___ to ___)

High to Low

What atmospheric condition operates in the UK (The Ferrel Cell)

The Jetstream

How are waves created?

Friction between wind and water transfers energy to the water.

What factors determine the amount of energy transferred to waves

Direction of Wind
Duration of Wind
Strength of Wind
Fetch

Define Fetch

The distance a wave travels interrupted by land masses.

Give some characteristics of waves

- Circular orbit
- Wave crest and trough
- Orbit becomes elliptical because of shore friction

What are the two different types of coastal waves (Not Physics!)

Constructive and Destructive

Give some properties of constructive waves

- Low height but long wavelength (100m)
- Low frequency, 6-8 a minute
- Wavefront steepens slowly, gentle breaking
- Weak backwash because of percolation of water

Give some properties of destructive waves.

- High wave height
- High frequency (10-14 a minute)
- Rapid steepen and plunge
- Powerful backwash, little forward movement which impedes the next swash.
- Often forms ridges nicknamed "Storm Beaches"

Why are beaches often subject to a cycle of constructive and destructive waves?

- Constructive waves steepen the profile and destructive ones break it down.
- Example of negative feedback
- Often breaks down due to other natural factors such as wind speed and direction.

Define Wave Refraction

Waves approach an irregular coastline, becoming more parallel to the coastline.

Where does wave refraction typically occur?

Headlands, the high energy is concentrated here. Low energy waves spread out across the bay.

Define currents

The permanent or seasonal movement of surface water in seas and oceans.

Give the names of three different currents.

- Longshore (Littoral) Currents
- Rip Currents
- Upwelling

How do longshore / littoral currents occur?

Waves approach the coastline at an angle, swash in the direction of the prevailing wind, backwash perpendicular to the beach, flow of water along the beach.

Define rip currents

Strong currents moving away from the shoreline - often occurs where seawater piles up. The current flows parallel to the coast before flowing out.

Give some properties of rip currents

- Occur in the surf zone (Where waves break)
- Not linear and travel in cycles
- Swell events influence the strength of one

Define Upwelling

Movement of cold water from deep oceans to the surface. The colder water is more nutrient rich and is responsible for global ocean currents.

Define Spring Tides

Occurs twice a month when the sun and moon are parallel to Earth. Causes the highest monthly tidal range.

Define Neap Tides

Occurs twice a month when the sun and moon are perpendicular to Earth. Causes the lowest monthly tidal ranges.

Define Sediment Cell

A stretch of coastline, usually bordered by two headlands, where the movement of sediment is more or less contained

What types of sediment can be found in a sediment cell?

- Clastic: From weathering
- Biogenic: Skeletons and Marine Organisms
- Non-Cohesive: Larger particles like sand moved grain by grain
- Cohesive: Small clay particle that bond together

Define the Coastal Sediment Budget

Measures the inputs and outputs of sediment in a cell and can be used to estimate the net movement of sediment each year.

Define Marine Processes

Removal of rock from processes within the water, such as hydraulic action (Or any other valid example)

Define Sub-Aerial / Aeolian Processes

Removal of rocks "IN-SITU" through either mechanical, biological or chemical means

Define Erosion

The wearing away / degradation and subsequent removal of material

Define Hydraulic Action

The processes by which air is forced into cracks in the rocks, mixture of acid and pressure erode the cliff.

Define Cavitation

Compression of air can cause sea water to be severely compressed. As the wave recedes, pressure reduces and the solution is released in violent fizzing.

Define Corrasion
How is this different to Abrasion?

Advancing waves picking up sediment and throwing it at the cliff face, transferring energy to the cliff

Abrasion is the sand paper effect as the sediment is dragged up and down.

Define solution / corrosion

Weak acids in sea water dissolve minerals such as calcium carbonate in the cliff. Can create cracks and encourage marine processes to erode further

Define Attrition

Where pieces of sediment hit against each other and become smaller, smoother and rounder over time.

Define Mechanical Weathering

Processes that physically damage the cliff itself. Such as Freeze-Thaw weathering. Water freezes in cracks and expands them, allowing more water to infiltrate.

Give three examples of Mechanical Weathering

Any three from
- Wetting and Drying
- Crystallisation
- Exfoliation
- Freeze-Thaw

Define Chemical Weathering

Breakdown of rocks by changing the chemical composition. Carboniferous limestone dissolved by weak carbonic acids.

Give two examples of chemical weathering

Carbonation
Oxidation

Define Biological Weathering

Breakdown of rocks from living organisms such as

- Plant Roots
- Birds
- Decaying material (Encourages chemical weathering)
- Marine Organisms

What is Mass Movement?

The sudden or gradual movement of sediment downslope due to the force of gravity

What is a rockfall?

The rapid free fall of rock from a steep, bare cliff face.

Give three key features that allow a mudflow to occur

Slopes of 10' or greater
A layer of topsoil that can be saturated
Impermeable rock below to allow the soil to slide as it gets heavier.

Give some key features that allow rotational slumping to occur

Permeable rock above impermeable rock
Step effect
Concave Bedding Plane
Undercutting

What is Soil Creep?

Soil expands at right angles and increases in size and weight. When it dries out, it contracts vertically and moves downslope. Very slow and occurs on gentle slopes

Give the four transportation processes

Traction
Saltation
Suspension
Solution

Define Traction

Boulders and other large material are dragged along the seabed

Define Saltation

Large pebbles and gravel "bounce" along the sea bed

Define Solution

Dissolved substances are carried in the water - dissolved limestone (example)

Define Suspension

Fine material such as silt and clay carried by the water - most eroded material transported this way

What factors influence coastal erosion?

Wave steepness
Fetch
Sea Depth
Coastal Configuration
Beach Prescence
Human Activity

What is a concordant coastline and what landform often occurs here? (Example?)

Where the rocks are organised in bands of harder and softer rocks parallel to the coastline. Coves (Such as Lulworth Cove) occur here.

What is a discordant coastline and what landform often occurs here (Example?)

Rocks are organised in bands of hard and soft rocks perpendicular to the coastline. Headlands and Bays (Such as the Isle of Purbeck) occur here.

Outline the formation of cliffs

- Erosional Landform
- Hydraulic Action (And corrosion) break down the cliff
- Dependant on fetch and strength of waves
- Cliffs are undercut and collapse
Example: Chalk Cliffs in Dover

Outline the formation of wave cut platforms

- Erosional Landform
- Abrasion key for the sand paper effect to drag material away
- Mass movement as the cliff retreats
- Example of negative feedback because waves can't break near the cliff anymore
Example: Kimmeridge Bay

Outline the formation of Caves

- Erosional Landform
- Hydraulic Action and Abrasion
- Wave energy concentrated on cracks that expand.
- May form an arch in the future.
Example: Old Harry Rocks (Isle of Purbeck)

Outline the formation of arches, stacks and stumps

- Erosional landform
- Sea caves become arches, collapse to stacks and then are eroded to collapse and become stumps.
- Marine and sub-aerial processes erode the bottom and top respectively
Example: Great Ocean Road (Australia)

Outline the formation of Headlands and Bays

- Erosional Landform
- Harder rocks are eroded more slowly, forming headlands
- Softer rocks eroded more quickly, forming bays and beaches
- Example: Isle of Purbeck (Dorset)

Outline the formation of Geos

- Erosional Landform
- Concentrated wave energy and weathering erodes a long vertical crack.
- Geo is widened by waves over time
Example: Shetland Isles (Scotland)

Outline the formation of beaches

- Depositional Landform
- Two types, constructive and destructive beaches, formed by named waves.
- Constructive beaches flatter and have lower wave energy than destructive
Destructive Example: Chesil Beach.

Outline the formation of spits

- Depositional Landform
- Caused by change in direction in coastline, prevailing blows sediment across a river or body of water.
- Decrease in wave energy behind spit, forming salt marshes.
Example: Hurst Castle Spit

Outline the formation of barrier beaches / bars

- Depositional Landform
- Occurs when a spit cuts off an entire body of water (Never occurs if there is an input such as a river)
- Bar may be infilled over time and start a new cycle of headlands and bays.

Outline the formation of a tombolo

- Depositional Landform
- Occurs when a spit connects an island to the mainland.
- May be eroded by marine processes or be tidal (Only appears at certain times)
Example: St Ninian and Shetland (Active relative to geological time)

Outline the formation of Sand Dunes

- Depositional Landform
- Very dynamic, lots of deposited sand needed to build one up.
- New dunes may form in front of older ones
Example: Studland Bay

What are the three different types of sea level rise?

Eustatic
Isostatic
Tectonic

How high has the sea level risen in the Holocene Period?

120m on average

What two terms define sea level rise?

Sea itself rising and falling
Land rising and falling relative to the sea

Are we currently in a glacial or interglacial period?

Interglacial

What is the name of the current period we're in (Geologically speaking)

Holocene Period (Started 10-12,000 years ago)

What occurs in an interglacial period?

- Higher sea levels (glacial retreat)
- Land rises relative to the sea where glaciers have melted.
- Bodies of land much less connected

What occurs in a glacial period

- "Snowball Earth"
- Typically lower sea levels
- Large glaciers extend from the polar regions (UK covered by one)

Define Eustatic Sea Level Change

- Sea level itself rising and falling
- GLOBAL changes
- Affected by human induced climate change (1-2m rise by 2100)

Define Isostatic Sea Level Change

- Land rising and falling relative to the sea.
- LOCAL changes
- Example: UK acts like a seesaw, glaciers melting caused land to rise in Scotland and sink in Southern England.

Define Tectonic Sea Level Change

- Tectonic Activity
- LOCAL changes
- Juan de Fuca plate causing tectonic uplift (1mm per year)
- Most changes reverted by large earthquake or volcanic eruption. Boxing Day tsunami caused a 0.1mm global rise in sea level.

Define Marine Regression

Where the sea level drops and produces emergent coasts

What are some examples of marine regression

- Eustatic fall in sea level
- Isostatic rebound of the Earth's crust.

Define Marine Transgression

Where the sea level rises and produces submergent coasts

What has led to consistent transgression in the Holocene Period?

Thermal Expansion and melting ice.

Why is Jakarta sinking?

Sudden growth in population. Over abstraction of water has led to 25cm of earth subsidence per year.

Define Emergent Coastlines and give an example

Results of local tectonic uplift or fall in sea level. Often leaves rocky coastlines.
Example: NW Scotland

Define Submergent Coastlines and give an example

Coastlines flooded due to relative sea level rise. Often river valleys flooded by ocean water.
Example: Norwegian Fjords.

What are raised beaches?

Key example of Isostatic rebound. Glacial ablation allows land to rise. You can also get raised beaches because of tectonic uplift - but this is restricted to areas of volcanic and earthquake activity.

Give an example of a raised beach / marine terrace.

Isle of Aaron / Isle of Skye - Northern Scotland - raised beaches 8, 15 and 30m above sea level

Seljalandsfoss - Iceland. Large waterfall 500m away from the coastline.

What is a Fjord?

Carved from mountainous glaciers, usually several km thick.
Abrasion of material dragged down the mountain. Deeper the further inland you go because sediment is deposited at the mouth of the valley.

What key characteristics does a fjord have?

It is longer than it is wide.
Mountains often range up to 1km above sea level around the fjord.