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

There are inputs and outputs of sediment through a system boundary

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

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

Open system (Energy and matter can enter and leave)

Water, sediment, solar insulation

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

Longshore drift
Weathering
Erosion
Waves
Prevailing Wind
Deposition
Mass Movement

Beaches
Headlands
Bays
Spits
Tombolos
Bars
Salt Marshes

Water, Sediment and Energy.

A set of processes that amplify an effect over time

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

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.

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.

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.

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

Shore Platforms
Cliffs
Beaches
Spits
Tombolos

Mudflats
Sandflats
Salt Marshes
Mangroves
Deltas

Sand Dunes

The Equator

High to Low

The Jetstream

Friction between wind and water transfers energy to the water.

Direction of Wind
Duration of Wind
Strength of Wind
Fetch

The distance a wave travels interrupted by land masses.

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

Constructive and Destructive

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

- 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"

- 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.

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

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

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

- Longshore (Littoral) Currents
- Rip Currents
- Upwelling

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.

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

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

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

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

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

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

- 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

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

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

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

The wearing away / degradation and subsequent removal of material

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

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.

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.

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

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

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

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

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

Carbonation
Oxidation

Breakdown of rocks from living organisms such as

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

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

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

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.

Permeable rock above impermeable rock
Step effect
Concave Bedding Plane
Undercutting

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

Traction
Saltation
Suspension
Solution

Boulders and other large material are dragged along the seabed

Large pebbles and gravel "bounce" along the sea bed

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

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

Wave steepness
Fetch
Sea Depth
Coastal Configuration
Beach Prescence
Human Activity

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

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.

- 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

- 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

- 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)

- 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)

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

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

- 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.

- 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

- 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.

- 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)

- 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

Eustatic
Isostatic
Tectonic

120m on average

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

Interglacial

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

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

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

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

- 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.

- 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.

Where the sea level drops and produces emergent coasts

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

Where the sea level rises and produces submergent coasts

Thermal Expansion and melting ice.

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

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

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

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.

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.

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.

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