Coastal Systems and Landscapes Flashcards
Talk about Coasts as a System
Coasts are considered an open system, however, can be seen as a closed system due to the different conditions and habitats in different areas which effect the coastal environment.
As an open system, the coast has important liks with other natural systems like the atmosphere, tectonics, ecosystems.
Inputs- Precipitation, wind, energy from waves, sediment, sea level changes.
Outputs- Ocean currents, rip tides, sediment transfer, evaporation.
Energy- Flowing water, effects of gravity on cliffs, moving air.
Stores- Beach, landforms etc.
Flows- Aeolian processes, erosion, wind, longshore drift, transportation
What are some examples of feedback loops within coastal systems?
Positive- Coastal managements increases erosion in other areas. Groynes trap sediment which deprives other areas increasing erosion. People walking over sand dunes destroys vegetation growing which causes erosion, roots can no longer hold the sand dunes making it more easy to erode
Negative- Strong storm waves erode sediment and form a bar further out to sea, waves are forced to break earlier so the waves loose energy and deposit the sand back up the beach and it turns back to equilibrium.
What are the sources of Energy to a coastline?
Wind, Waves, Currents, Tides
Talk about Wind as a coastal process?
Wind is the primary source of energy as it creates waves.
It is the movement of air from one place to another from an area of high to low preassure.
The difference in preassure is known as the preassure gradient and defies the strength of the wind. The greater the difference, the steeper the gradient, the stronger the wind, the stronger the waves.
Talk about waves as a coastal process?
Waves are primarily formed by wind however, they can also be formed by tectonic activity.
Wind blows over the surface of the sea, generating frictional drag which forms ripples. In the open sea, there is little horizontal movement of water, instead there is an orbital motion of the water particles. Closer to the coast, horizontal movement of water does occur as waves break onto the beach.
What are the factors effecting wave energy?
- Strength of wind
- Duration of wind
- The fetch
Talk about Constructive Waves?
- Frequency- 6-8 minuites
- Created by distant weather systems which generate these waves in the open ocean.
- Large Amplitude, Low wave height
- gentle waves and beach profile
- large swash, weak backwash,
Talk about Destructive waves.
- # 10-14
- Caused by local storms
- short amplitude, tall wave height
- big, plunging waves
- small swash, large backwash
Discribe the process of wave rarefraction?
- occurs when the coastline is not uniform (ie. headlines and bays)
- Waves travel faster in deeper water (no friction), so waves arrive at the headland first causing waves to rarefract which means the waves are distorted.
- This concentrates the waves energy on the headland resulting in greater erosion.
- Low energy waves are rarefracted toward a bay causing deposition
- This is an example of negative feedback.
- longshore currents can occur here.
- Discordant coastline
Talk about tides.
- Caused by the sun and moons gravitational pull
- The moon has the greatest influence, dispite the suns gravitational pull being a lot stronger
- Two high tides and two low tides a day
- it takes 28 days for the moon to orbit the earth
- every 14 days, the moon and sun align creating the strongest pull- Spring Tide
- every other 14 days, the moon is perpendicular to the sun, creating the weakest pull- Neap Tide
What are factors that affect the patterns of tides?
- morphology of the sea bed
- closeness of land mass
- The coreolis effect
Talk about tidal range.
The difference between the high and low tides.
The tidal range determine the development of the coastline through range of erosion and deposition
A lower tidal range means waves will break on a more concentrated part of the coastline and vice versa.
Types of tidal range:
- macrotidal (4m+)
- mesotidal (2-4m)
- microtidal (>2m)
What are currents and what are the three types?
A current is the movement of water at the surface which can be powerful for transporting energy and matter.
There are three types: longshore currents, Rip Currents and Upwelling
what are longshore currents?
occur as most waves do not hit the coastline head on, but approach at an angle. This makes a current parallel to the coastline, zigzagging in the same direction as longshore drift
What are rip currents?
Strong currents moving away from the shoreline, they develop when seawater is piled up along the coastline by incoming waves, due to sand bars. This ends up perpendicular to the coast. Bars of sediment funnels out backwash underneath the sea surface creating a current up to 5mph.
What is Upwelling?
movement of cold water from deep in the ocean toward the surface. The more dense, cold water, replaces the warmer surface water and creates nutrient rico ocean currents. This forms part of global pattern of circulation.
What are Storm Surges?
A storm surge is the abnormal rise in seawater lebel during a storm due to the strong winds blowing the water up. It is also due to low pressure allowing higher tides.
What is the difference between high energy and low energy coastlines?
High Energy- More powerful waves, areas where there is a large fetch, erosion exceeds deposition, erosional landforms ie Cornwall.
Low Energy- Less powerful waves, or coast is sheltered, rate of deposition exceeds the rate of erosion, depositional landscapes, ie Lincolnshire esturaies and bays
What are the sources of Sediment?
Rivers- sediment that is transported by the rivers accounts for a vast majority of the sediment in a coast, especially in high rainfall environment.
Cliff Erosion- important in local areas with soft and unconsolidated rocks ie Holderness coasts where erosion can be 10m per year.
Longshore Drift- Sediment is transported from one streach of coastline to another.
Wind- Wind blowing can move sand can be deposited that helps contribute to dune growth and formation.
Glaciers- Ice sheets and glaciers can melt jnto the sea depositing sediment
Offshore- Sediment from offshore caan be transfered into the coastal zone by waves, tides and currents.
What is a sediment cell?
Sediment cells are a streach of coastline, usually bordered by two headlands where the movement of sediment is more or less contained and the flows of sediment act in dynamic equilibrium.
Talk about Sediment cells (UK)
There are 11 littoral cells on the English and Welsh coastline which can be split into sub-cells.
The processes of Erosion, Transportation and Deposition within a coastal landscape is largely contained in a cell, so they are considered closed systems.
However sediment can jump from cell to cell, so it could be seems as an open system
INPUTS- rivers, coastal erosion, sand bars/banks, currents, aeolian and sub aeolian.
TRANSFERS- Longshore drift, rides, waves, currents, aeolian
OUTPUTS- beach, sand dunes and bars and banks
Talk about sediment budgets.
All of the sediment in a cell can be considered part of a budget
Positive = surplus, more material, builds toward the sea
Negative = deficit, retreats landward, material removed
However the cell always want to be at dynamic equilibrium
Events that can effect Sediment Budget:
- storms, remove sediment by erosion
- rising sea levels,
- flooding
- human activity
These increase erosion as dump more sediment in estuary and can be transported offshore.
What is weathering?
Weathering is the breakdown or disintegration of rock in its original place. Energy flows can be clearly demonstrated as most processes involve energy. Weathering leads to the transfer of material
What is Mechanical Weathering and examples.
Breakup of rocks without chemical changes taking place
Freeze Thaw action- when water enters a crack and freezes, expanding in volume which forces the cracks to widen
Salt Crystallization- When salt evaporates, leaving salt crystals behind which grow overtime exerting stress on the rock causing it to break down.
Wetting and Drying- Frequent wetting and drying cycles expand and contract in a rich clay cliff causing them to break and crack.
What is biological weathering and examples?
The gradual destruction of rocks caused by living organisms.
Vegetation Root- Roots grow into small cracks which widen as the roots grow which breaks up the rock
Birds and animals dig burrows- in cliff breaking it up
Water running through decaying vegetation- become acidic which increases chemical weathering.
What is Chemical Weathering and examples?
The breakdown of rocks using chemical reactions.
Carbonation- rain water absorbs CO2 from the air to form a weak carbonic acid which reacts with calcium carbonate in rocks which is easily dissolved, cooler the rainwater, more carbon dioxide absorbed
Oxidation- The reaction of rock minerals with oxygen ie. iron, forms a crusty red powder which makes rocks more venerable to weathering
Solution- dissolving of rock materials
What is mass movement?
Mass movement is the movement of material downhill under the influence of gravity. It can be assisted by rainfall. It can be sudden and occur over a long period of time. More common on steep surfaces.
What are the factors affecting mass movement?
- level of cohesion
- height of slope
- Grain size within sediment
- temperature, freeze thaw action
- level of saturation
- Temperature and Climate
Describe soil creep?
- The slowest form of mass movement
- Particles rise and fall due to wetting and freezing and then returning vertically to the syrface in response to gravity as the soil dries out
- Zig-zag like motion
- Leads to the formation of terracettes
Describe Mudflows?
- Saturated soil reduces friction leading to mud flowing over week bedrock.
- Water gets trapped in the pores of rock weakening the slope by pushing the pores apart
- Happens after rainfall
- happens quickly
What is rockfall?
- sudden collapse of individual rock fragments
- often triggered by mechanical weathering
- leads to scree due to rocks bouncing down the slope
- associated with steep cliffs
What is a landslide?
- Block of rock rapidly moving downhill along a planar surface
- can also be caused by an earthquake
- rainfall leads to water between joints which reduces friction
- very rapid and appose a threat
What is a landslip?
- Different to landslide as the surface is curved
- Weak clays and sands are underlined by impermeable rock causing a build up of pore water preassure.
- The weak clays and sands collapse under own weight
What is runofff?
When sediment flows over the ground downhill moving small particles causing them to enter the littoral zone.
How can temperature and climate influence weathering?
In Warmer climates, Chemical weathering is more prominent whereas in colder climates, mechanical weathering is more common.
What is Hydraulic Action
As a wave crashes onto a rock or cliff face, air is forced into the cracks within the rock. The high preassure causes the cracks to force apart and break off rock.
