booklet 1- coasts as natural systems Flashcards
(36 cards)
1
Q
what is a coast
A
a dynamic boundary where the land meets the sea
complex system with different outputs , stores, inputs , processes
dominated by interrelationship of spheres
a continuum of relevant processes and landforms
2
Q
dynamic equilibrium and is a coast an open or closed system
A
- wide range of inputs, outputs etc = systems is rarely static BUT different components and factors within systems changed to maintain this balance
- coast can be seen as an open and closed system
—> open because it receives inputs from different spheres
—> closed because sediment cell (stretch of coastline bordered by 2 headlands where movement of sediment is contained)
3
Q
inputs in a coast
A
- sediment carried by waves/rivers
- waves, tides, currents
- precipitation
- weathering rock
- humans (pollution, settlement, management )
- wind
4
Q
processes (transfers/flows) in coast
A
- erosion
- transportation
- deposition
- mass movement
- longshore drift
5
Q
outputs in coast
A
- eroded material taken out to sea
- evaporation
- ocean currents
- rip tides
6
Q
stores in coast
A
- beaches, sand dune, marsh environments , cliffs, bar , spit etc
7
Q
what is the energy (power/driving force) in coats
A
- sun, wind energy, wave energy , effects of gravity on cliffs
8
Q
positive feedback at coasts
A
- waves erode cliffs = material released = this abrades cliff= more cliff erosion
- groynes = trap sediment = deprives areas elsewhere down drift = excaberate erosion
- sea walls= transfer high energy waves elsewhere
9
Q
negative feedback at coasts
A
- when rate of weather and mass movement exceeds rate of cliffs erosion= slope formed —> material builds up cliff face protecting it from sub aerial processes = less mass movement etc
10
Q
dynamic equilibrium between type of wage and angle of beach
A
- constructive waves build up beach = steeped and encourages destructive waves that plunge rather than surge = redistribution of sediment offshore by destructive waves reduces beach gradient = encourages more constructive waves
11
Q
links to other natural systems (human and physical)
A
- quaternary glacial and interglacial periods = sea levels (eustatic and isostatic) rise and fall several times in response to global water cycle —> this impacted location of coastal processes etc
- changes in global carbon cycle = global warming = impacting sea levels and ecosystems = flooding and more storm surges etc
- many landforms at coast created by wind , rivers etc
- Dyroholaey, Iceland= shows link with coastal processes and other physical systems —> it is made up of vast , exploded coastal plants caused by volcanic basalt transported by rivers, glaciers and wind/sea level change
12
Q
what do processes + factors create
A
processes + factors = landforms
13
Q
what are some processes ?
A
wave action
erosion
weathering
sub aerial
tides
longshore drift
mass movement
14
Q
what are some factors?
A
human activity
geology
lithokogy
vegetation
sediment
slope
prevailing wind
sea level change
sediment supply
15
Q
what are some landforms
A
rocky coasts:
- cliffs, caves, arch, stack, stump, shore platforms , slumps, slides, flows
beach coasts:
- swash and drift aligned beaches
spits, bars, tombolos, sand dunes , salt marshes
16
Q
what are the energy sources in coastal systems?
A
wind
tides and currents
rip currents
17
Q
explain the energy source wind
A
wind = movement of air from high to low pressure
- waves= can be generated from tectonics
- normally generated by friction from wind
- air moves from high to low pressure = wind
- UK prevailing winds come from SW , huge fetch over the Atlantic
18
Q
wind- what is wave energy determined by?
A
- strength of wind (pressure gradient)
- duration of wind blowing
- fetch (distance the wind blows over open water)
19
Q
explain the energy tides and currents-
A
- changes in water level of sea caused by gravitational pull of moon (and sun)
- UK experiences 2 high and 2 low tides a day
- different between high and low tides= tidal range
- tidal range impacted by sun and moon position e.g. highest during spring tide
- high tidal range creates powerful tide currents as tides fall and rise (often is estuaries)
- current= movement of water back and forth (rather than up and down) —> key for transporting sediment
- currents driven by factors including tides, wind , shape of land, water temp etc
20
Q
what are rip currents
A
- strong localised underwater currents on some beaches = big danger to swimmers etc
- caused by series of plunging waves that cause temporary build up of water on top of beach met with resistance from breaking waves
backwash= forced below surface of troughs and small undulations in beach profile = can pull ppl etc under
21
Q
how are waves formed?
A
- wind moving over water= direction between water and moving air moves up water into ridges that become waves
- circular orbit in open water as little friction with water and base
- shape of wave and its energy transferred horizontally , waves become more elliptical due to friction slowing velocity of base of wave
- top of wave moves faster , higher and steeper and begins to breaks
- horizontal movement of the water only happens at coast, in open sea the orbits circular
22
Q
what are the types of waves ?
A
constructive and destructive
23
Q
features of a constructive wave
A
- caused by distant (calmed weather (summer etc)) weather systems in open ocean
- low surging waves with long wavelength
- strong swash, weak backwash
- beach gain (builds up material on beach= increased gradient )—> STEEP profile created
- less frequent
- have limited energy
24
Q
features of a destructive wave
A
- cause by local storms
- high waves with short wavelength
- weak swash, strong backwash
- more energy
- creates a FLAT profile
- greater erosion (beach loss)
- more frequent
25
construction and destructive waves key points
- constructive waves often associated with gentle beach profiles = enables waves to surge up beach BUT this steepens beach = encourages destructive waves (plunging rather than surging) removing material form beach and deporting it offshore = less steep profile and encourages constructive waves —> results in dynamic equilibrium caused by negative feedback
26
high energy coastlines
- rocky coasts
- in UK: stretches of Atlantic facing coasts where waves = more powerful for much of the year e.g. Cornwall
- rate of erosion > rate of deposition
- erosional landforms e.g. headlands, cliffs, wave cut platforms etc
27
low energy coastlines
- sandy and estuarine coats
- stretches of coasts where waves are less powerful or where coast is sheltered from large waves e.g. estuaries bay of Lincolnshire
- rate of deposition> rate of erosion
- depositional landforms (bars, beaches, spits, tombolos etc)
28
what is wave refraction?
A distortion of wage fronts as they approach an indented shoreline
- caused energy to be concentrated on headlands and dissipated in bays
- can see negative feedback here as variation in rock strength = formation of headlands and bays = wave refraction causes erosion of headlands and deposition in bays= working against original erosion of softer rock that formed original bay
29
what are sediment cells ?
- closed systems - largely self contained stretch of coastline —> often separated from other areas by headlands/ stretches of deep ocean = movement of sediment is pretty contained
30
sediment cells inputs, transfers, stores and sources of sediment
inputs= river , coastal erosion, offshore sources etc
transfers= longshore drift, rip currents etc
stores= beach, sand dunes, offshore deposits etc
31
how many sediment cells are in England /wales
11 which are divided into many smaller sub cells e.g. Christchurch Bay Dorset
32
sediment budgets
- sediment cells have losses (deposition etc) and gains (erosion etc)
—> overall it tries to achieve dynamic equilibrium (erosion=deposition) —> balance can be upset by events e.g. surge in river discharge following floods, severe storms (erodes beach etc)= transfers sediment outside system , human actions = also impact this
33
sediment cells- the South Carolina, USA (north coast)
- research been conducted , improved coastal protection , increased erosion due to climate change. —> coastal protection impacted and disrupted operation of sediment cells and budget
34
beach profile key words
* see diagram on mindmap
- backshore, foreshore, inshore, offshore, nearshore (swash zone, surf zone, breaker zone, littoral zone)
35
beach profile what is the backshore, foreshore, inshore, offshore
backshore- area between high watermark and land limit of marine activity
foreshore- area between high and low watermark. key zone for marine processes
inshore- area between low water mark and point where waves cease to have any influence on land beneath them
offshore- area beyond point waves crease join sea bed. Activity= deposition of sediments
36
beach profile what is near shore (swash zone, surf zone, breaker zone, littoral zone)
near shore- area extending seaward from high watermark area to where waves begin to break includes:
swash zone - area where water washes up beach
surf zone- area between points where waves break= forms bubbly surface and where waves then move up beach as swash in swash zone
breaker zone- area where waves approaching behind to break
littoral zone- area of land between cliffs/dunes on coast and the offshore area beyond the influence of waves —> constantly changing due to tides, storms , sea level changes and human intervention
