Coastal Systems And Landscapes Flashcards
Define system
A set of interrelated components working together towards some kind of process
Define closed system and give an example
Closed systems have transfers of energy both into and beyond the system boundary, but no transfer of matter
Eg carbon cycle
Define open system and give an example
Where matter and energy can be transferred from the system, across the boundary and into the surrounding environment
Eg hydrological cycle
Define isolated system
Isolated systems have no interaction with anything outside the system boundary.
No input / output of matter of energy
Define dynamic equilibrium
Where there is a balance between inputs and outputs of a system
Define positive feedback
Where the effects of an action are multiplied by the following knock on effects
Define negative feedback
Where the effects of an action are cancelled out by its following knock on effects
Define subsystems
The earth is divided into 5 subsections / spheres
Name the earths 5 subsystems
Atmosphere Lithosphere Biosphere Hydrosphere Cryosphere
Define cascading system
The earths subsystems interlink to form a cascading system
Define fetch
Distance travelled by waves
Define prevailing wind
Most frequent wind direction
Define wavelength
Distance from one wave crest to the next
Define wave height
Distance from wave crest to trough
Define swash
Wave travelling up the beach
Define backwash
Wave travelling from the beach back into the sea
Define constructive wave
Characteristics mean more sediment is brought onto the beach in the swash than is removed by the backwash
Define destructive wave
Characteristics mean more sediment is removed from the beach by backwash than is brought onto it
Give an example of positive feedback in a system
Global temp rises -> oceans warm up -> warm water unable to dissolve gas -> more CO2 released -> more CO2 in atmosphere -> greenhouse effect -> global temp rise
Give an example of negative feedback in a system
Increase use of fossil fuels -> more CO2 in atmosphere -> global temp increase -> more plants grow -> absorb CO2 -> reduce in CO2 in atmosphere -> less global warming
Facts about the atmosphere
• nitrogen (78%), oxygen (21%), other gases (1%)
• atmosphere becomes thinner the higher up it is until it reaches space
• divided into 5 layers:
- troposphere
- stratosphere
- mesosphere
- thermosphere
- exosphere
• purpose to filter and stop UV radiation entering the earth
Facts about the biosphere
• area on or near the earths surface where life is found
• subdivided into 3 sections:
- lithosphere (rocks)
- atmosphere (air)
- hydrosphere (water)
• stretches 10km above sea level and 8km deep
Facts about the lithosphere
- includes the upper mantle and crust
- ‘lithos’ is Greek for rock
- average 75km thick
- sits on top of asthenosphere
Facts about the hydrosphere
• includes all water on, above and below earth - lakes - sea - rivers - ice - clouds • water can be liquid, vapour or ice
Facts about the Cryosphere
• the frozen water part of the earths system
- snow
- freshwater ice
- sea ice
- glaciers
- permafrost
How might the Cryosphere interact with the lithosphere?
Permafrost
Freeze thaw
Glacial erosion
How can you link the hydrosphere to the lithosphere?
Coastal / river erosion -> sediment ->. Deposition
How can you link the lithosphere to the biosphere?
Rocks in the lithosphere break down to form soil
Volcanoes - lahar mud flows
Is the coast a closed or open system?
Open
How can the dynamic equilibrium of the coastal system be upset?
Eg increased deposition of sediment on the beach but no corresponding change in sediment being removed
Inputs of the coastal system
• energy from - waves - wind - tides - sea currents • sediment • geology of coastline • sea level change
Components in the coastal system…
- erosional landforms and landscapes (caused by erosional processes)
- depositional landforms and landscapes (caused by wind and water transport)
Outputs in the coastal system…
- dissipation of wave energy
- accumulation of sediment above the tidal limit
- sediment removed beyond local sediment cells
How might the lithosphere interact with the atmosphere?
Weathering of rocks (rain wind etc)
Volcano -> ash cloud
What are the ‘shore’ areas in a coastal transect?
Backshore
Foreshore.
Inshore
Offshore
Where is the backshore area found and when do things occur here?
Area between HWM and landward limit of marine activity
Changes normally occur here only during storm activity
Where is the foreshore area found and what occurs here?
Area between HWM and LWM
Most important zone for marine processes in times not effected by storm activity
Where is the inshore area found?
Area between LWM and point where waves have no influence on land beneath them
Where is the offshore mark found and what activity takes place here?
Area beyond the point where waves cease to impact upon seabed
Activity limited to deposition of sediment
Give an example of negative feedback at the coast
Beach in dynamic equilibrium -> sediment eroded from beach during a storm -> sediment deposited forming offshore bar -> waves now forced to break before reaching the beach, dissipating their energy + reducing erosion at beach -> when storm calms, normal wave conditions erode offshore bar -> beach in dynamic equilibrium
What are waves formed by?
Winds on the surface of the sea - can be both local and distant winds
What are the factors that affect the strength of waves?
Wind velocity
Wind duration
Fetch
Which winds that hit the UK are most prevailing?
Come from South West, Atlantic Ocean
Describe how waves are formed
Wind causes friction at surface of sea
Friction causes a swell (wave)
Energy from wind causes water to move forward in an elliptical motion (circular)
Give the wave energy equation
Energy =(prop) wavelength x wave height^2
Give the characteristics of a constructive wave
Sloping wave front Wide wavelength Strong swash Weak backwash Low frequency (6-8/min)
Give the beach characteristics created by constructive waves
Wide, gently sloping beach
Berms (ridges)
Give the characteristics of destructive waves
Steep wave front Short wavelength Weak swash Strong backwash High frequency (10-14/min)
Give the beach characteristics created by destructive waves
Narrow steep beach profile
Trough
When does wave refraction occur?
When waves are not a regular shape when they reach the shore
What changes in the waves as they reach the shore during refaction?
Wave depth increases
Wave velocity decreases
Waves are bent towards the shoreline that is slowest
Waves crash to mirror the seabed contour
Which type of waves converge during wave refraction and where do they converge to?
Destructive waves converge towards headlands, eroding it
Which type of wave diverge during wave refraction and where do they diverge to?
Constructive waves diverge towards bays, depositing sediment there
Define global ocean conveyorbelt
Constant moving system of deep ocean circulation driven by temperature and salinity
What is the global ocean conveyorbelt driven by?
Combination of thermohaline currents in the deep ocean and wind driven currents on the surface
How does the global ocean conveyorbelt link to the coast?
The temperature of the water changes when it enters areas closer to coastlines
Define upwelling
A process in which deep, cold water rises towards the surface
Describe how upwelling takes place
Winds blowing across the ocean surface push water away.
Water then rises up from beneath surface to replace the water.
Why do areas of upwelling often have high biological activity?
The water that rises to the surface is typically colder and is rich in nutrients, which fertilise the surface waters
What are ocean currents driven by?
Wind
Water density differences
Tides
Define ocean currents
The movement of a body of water from one location to another
Generally measured in m/s or in knots
What are currents driven by?
The rise and fall of tides
Wind
Thermohaline currents
How does the rise and fall of tides impact on currents?
Tides create a current in oceans which are strongest near the shore and in bays and estuaries along the coast = tidal currents.
Give some information about tidal currents
Change in a very regular pattern and can be predicted for future dates
Strong tidal currents may travel at speeds of 8 knots or more
How do winds impact on currents?
Winds drive currents that are on / near the ocean surface
In coastal areas they drive currents on a local scale -> upwelling
Global scale = winds drive currents that circulate ware for thousands of miles throughout ocean basins
How does thermohaline circulation impacts on currents?
Currents occur at both deep and shallow ocean levels and move much slower than tidal / surface currents
How do currents affect the earth’s climate?
By driving warm water from the equator and cold water from the poles around the earth
Define rip current
Powerful, narrow channels of fast moving water
Move at speeds of up to 8 feet/second
They flow away from the shoreline towards the sea
What is a longshore current?
When a wave reaches the coastline, it releases a short burst of energy that generates a current which runs parallel to the shoreline = longshore current
What are longshore currents affected by?
Velocity of the wave
Angle of the wave / beach
E.g. Longshore currents increase velocity when…. wave breaks at steeper angle / steeper beach slope / high wave
Define flood current
An incoming tidal flow
Define ebb current
An outgoing tidal flow
Define slack water / slack tide
The period between flood and ebb tides when there is little / no current
What are tides caused by?
The gravitational pull of the moon and the sun
What are tides?
Very long period waves that move through the oceans in response to the forces from the moon and sun.
Tides start off in the oceans and move toward the coastlines where they appear as the regular rise and fall of the sea surface
Define high tide and low tide
High tide - when the crest of the wave reaches the shore
Low tide - when the trough of the wave reaches the shore
Define tidal range
The difference between high and low tide
When do spring tides occur? Why?
During full moons / new moons
When the earth, sun and moon are in alignment
The gravitational pull of the sun is added to that of the moon, causing the oceans to bulge a bit more than usual
How do spring tides affect tides and how often do they occur?
Average tidal ranges are slightly larger
Happen twice each lunar month
When do neap tides occur? Why?
When the sun and moon are at right angles to each other
The solar tide partially cancels out the lunar tide and produces moderate tides
How do neap tides affect tides and how often do they occur?
Tidal range is smaller
Happens twice each lunar month
What is the difference between currents and tides?
Currents move left and right, tides move up and down
Currents occur due to tides, winds and thermohaline circulation, tides occur due to gravitational forces from the moon and sun
What are the characteristics of a low energy coast?
Low wave energy
Low rate of erosion (sometimes higher rate of deposition)
Landforms include beaches and spits
What are the characteristics of a high energy coast?
High wave energy
Fast rate of erosion
Landforms include headlands, cliffs, WCP
What factors influence the regular pattern of the tide?
Morphology of the seabed
Proximity to landmass
Coriolis force
What is tidal range significant for?
Shipping routes
Coastal erosion
Leisure reasons
When do tidal surges occur and what is their effect?
Occur at times of intense low pressure (a depression)
Produce very high sea levels and violent storms
Name the two types of geomorphological processes
Marine processes
Sub aerial processes
Define marine process
Coastal processes that link with the sea e.g. Waves, tides, LSD
Define subaerial process
Take place on land but determine the shape of the coastline e.g. Weathering, mass movement, run off
Name the types of marine processes
Hydraulic action Wave quarrying Abrasion Attrition Solution
Define hydraulic action
The weakening of rocks by the force and pressure caused by the water hitting them
Define wave quarrying
Waves compress air into fissures / joints in the cliff face
As the wave withdraws the air is quickly released like an explosion
This weakens / breaks off the rock
Define abrasion
The weakening of rocks by sediment in the sea being thrown against the cliffs / WCP
Define attrition
Material in the sea wear down each other as they collide in the water
Define solution
When acidic water dissolves calcium based rocks e.g. Limestone
Carbon based rocks at the coast can be eroded by rainwater flow from the land as the pH of this is slightly acidic
Salt from the sea water residue in the rocks evaporates, forming salt crystals which as it expands, weakens the rock
Name the factors that affect the rate of marine erosion
Wave steepness Breaking point Fetch Sea depth Coastal configuration Beach presence Human activity
How does wave steepness affect the rate of coastal erosion?
Steeper waves carry more energy -> more erosive
How does breaking point of waves affect the rate of coastal erosion?
Closer the waves break to the shore, The more they erode rocks
How does fetch affect the rate of coastal erosion?
Waves have more energy if they have travelled a longer distance before reaching the shore -> more erosive
How does sea depth affect the rate of coastal erosion?
A steeper-shelving sea bed by the shore -> higher and steeper waves
How does coastal configuration affect the rate of coastal erosion?
Headlands attract high energy, destructive waves through wave refraction
Concordant / discordant -> more / less resistant rocks exposed
How does beach presence affect the rate of coastal erosion?
Beaches dissipate wave energy -> lower rate of erosion
Steep narrow beaches -> dissipate flatter waves
Flat, wide beaches -> dissipate high/rapid energy outputs (spread over a large area)
Shingle beaches -> dissipate steep waves by friction/percolation
How does human activity affect the rate of coastal erosion?
Higher rate of erosion -> removing beach material
Lower rate of erosion -> sea defences (may increase erosion elsewhere)
Define lithology
Refers to the characteristics of the rock
Esp resistance to erosion and permeability
Define differential erosion
The variation in rates that different rock types erode
Define concordant coastline
Where rock types run parallel to the coastline
E.g. Lulworth Cove
Define discordant coastline
Where rock types run perpendicular to the shoreline
Et Swanage bay
Define the ‘dip’ of the rocks
The angle at which rock layers are aligned within the rock
What does the dip of the rock affect?
Affects the steepness of cliff
Steepest cliffs - where rock strata is horizontal / dipping inland
Sloping cliffs - where rock strata dips towards the sea
Name the types of marine transportation
Traction
Saltation
Suspension
Solution
Define traction
Large rocks / boulders slide along the seabed in high energy locations due to the movement of the water
Define saltation
Small stones bounce along the seabed / beach in high energy locations , dislodging other stones
Define suspension
Very small particles of sand and silt that are carried in/ picked up by the water, giving it a murky appearance
Define solution
Dissolved materials are transported within the mass of moving water
What is the official name for sand dunes?
Psammosere
What are sand dunes created by?
Aeolian transportation
Aeolian deposition
Name the types of aeolian transportation that causes sand dunes to form?
Surface creep
Saltation
Define fluid threshold velocity
Wind speed needed to entrain sand particles
So that sand dunes form
What are the conditions needed for sand dunes to form?
Lots of fine sediment - from rivers/seas
High wind energy - big fetch
Large tidal range
Large backshore area
Name the types of sand dunes
Embryo dune Fore dune Yellow dune Grey dune Dune slack Mature dune
How do sand dunes form?
Sand is deposited when an obstacle traps it e.g. Driftwood, a rock, a bush
As sediment accumulates the mound of sand becomes larger -> dune
Plant e.g. Marram grass, sea couch
The roots interlock with the sand, holding the dune together
