COASTS Flashcards
What is a model?
A way of understanding a complex world in simple form.
What are the four factors every model has.
1) Inputs
2) transfers
3) outputs
4) boundaries
What is the input?
Anything added to the model
What is the transfer?
Processes within a model
what is the outputs?
Anything leaving the model.
What are the boundaries?
The outer area of a model.
What is an open system?
Has inputs and outputs.
What is a closed system?
Doesn’t have inputs or outputs
What is energy in terms of natural systems?
Driving force/ power
What are stores and components in terms of natural systems?
The individual elements which make up a system.
What is positive feedback?
The flow/ transfer which results in increase/growth. creating change in balance of system = new equilibrium
What is negative feedback
Where flow/transfer result in decrease/ decline. to restore the balance of the system = dynamic equilibrium
Dynamic equilibrium
Represents the state of balance within a changing system.
how does wind travel?
diffuses from areas of high pressure to areas of low pressure
factors which increase wind strength
^duration, ^extent of pressure gradient, ^fetch
how are waves formed? (6 steps)
1) wind over water = frictional drag.
2) circular motion of water
3) shallower water = friction at sea floor
4 )elliptical movement
5) WL and velocity decrease and height increases
6) water backs up and rises to breaking point
formation C+D
near weather system = D
far weather system = C
wave form C+D
low surging wave, long wavelength C
short walelength, high plunging wave = D
beach profile C+D
steep, but flatten over time with erosion LOSS= D
gentle incline, but becomes steeper w deposition GAIN=C
neeptide
lowest tidal range
spring tide
highest tidal range
rip current
strong localised underwater current when plunging waves are met with breaking waves causing currents to form between.
tides
change in water level due to position of sun and moon.
wave refraction
energy concentrates around headlands and dissipates in bays - erosional and depositional land forms
sediment cells
stretch of coastline that is a relatively closed system usually bordered by 2 headlands. eg Christchurch bay
no. sediment cells in england and whales
11
sub cells
link marine processes
sediment budget
losses and gains of materials and energy
weathering
breaking down of rocks in situ, not due to sea, leads to transfers of materials
mechanical weathering (4)
exfoliation (temp) , freeze thaw, crystallisation (salt crystals), wetting & drying
coastal marine processes
erosion, deposition, transpotration
sub-areal proccesses
weathering, mass movement and run off
chemical weathering
carbonation (acid rain calcium carbonate to calcium bicarbonate )
oxidisation (rusting)
biological weathering
plants, animals
slumping
stages, rotational slip, saturation and undercutting
soil creep
gradual movement of individual particle, wet dry, g
rock fall
rapid free fall, steep slope , dry conditions, freeze thaw
landslides
sections of cliff detached, saturation
mud flow
steep slopes, saturated clay, little vegetation
run off
flow over impermeable surface, transports fine materials
factors influencing mass movement (3)
angle of slope, vegetation cover and rainfall
erosional
break down and transportation of materials, action by sea
erosional processes (5)
attrition (s,r,s), abrasion(cliff face) , corrosion ( chemical), hydraulic action, quarrying ( vibrations on cliff), cavitation (expanding air)
transportation
movement of materials from one part of shoreline to another
transportation processes (6)
longshore drift, offshore currents, suspension (small), traction (sea bed), solution (dissolved) , saltation (shingle bounce)
Deposition
materials build up when energy declines
causes of energy decline
1) alternating energy source (wind change)
2) stopping flows
3) increases friction
4) increased load - too big to move
discordant coastline
geology at 90* to the coastline with alternating soft and hard rock
concordant coastline
geology in parallel to the coastline, only hard rock.
featured of coastal erosion (8)
wave cut platform
bays, headlands
caves, blowholes, arcs, stacks and stumps
describe the process of wave cut platforms
waves erode cliff base = basal shelf.
its uncovered at low tide and covered at high tide
cliff retreat = wider wcp
eventually friction increases reducing erosional effect
= negative feedback loop
BUT change in imput (eg. sl rise) = process starts again
What is a blowhole?
when the joints in the cave roof give way to expose the cave roof.
Features of costal deposition (6)
beaches
spits, bars and tombolos
barrier island
sand dunes
berm
terraces = positional change of high tide
cusp
crescent shaped indentations that form in the junctions between sand and shingle on the beach
runnel
ridges of finer material parallel to the shore
Storm beack
top of beach, larger courser materials
spit
long narrow beach which extends into the sea from the shore.
causes a positive feedback loop
may curve due to change in prevailing wind direction
tombolo
spit that joins an offshore island
bar
spit which extends to the other side of a bay forming a lagoon.
barrier island
how are the formed?
series of depositional islands running parallel to the shore but unattached. can form offshore bars as they get longer.
deposits due to limited tidal range and increased friction.
possibly occurring after the ice age with rapid SL rise.
dune formation
embryo dunes, foredunes, fixed dunes form, dune slacks,
dune health.
cavitation
wave recedes, compressed air expands violently, exerting a force on the rocks and causing pieces to break off.
wave quarrying
the energy of the wave as it breaks against the cliff is enough to detach pieces of rock.
offshore bar
bars can form off the coasts as materials move inland. they may be partly submerged.
may be eroded to form smaller barrier islands.
sand dune
found immediately behind an active beach zone. Wind blown sand is fixed by vegetation.
sand dunes are most likely to develop in what conditions?
sandy beaches
large tidal zone - lots of exposed beach
shallow beach gradient - more exposed sand at low tide
persistent offshore wind and saltation
how are embryo dunes formed?
windspeed drops = sand deposited
yellow in colour
what are foredunes?
developing embryo = vegetation adds organic matter= more plants = root systems, flowering plants = reduced salt content = due become grey
what is a fixed dune form?
wind blows sand behind the foredunes while it is unstable
dune slacks
depressions between substantial dunes
high moisture content as they are closer to the water table
dune health
dunes develop more inland and drought tolerant plants grow beyond active sand accumulation.
there is better pH content, Hummus content and moisture retention.
salt marsh and estuarine deposit develop in:
- areas of sheltered water
- slow energy environment - no strong tides/currents
- where salt water meets freshwater
pioneer plants
early colonisers that can withstand harsh conditions
- dense stems and roots reduce tidal current and increase deposition
- plants die and decompose = high level of submergent shore.
mudflats to saltmarshes
- pioneer plants colonise
- plant roots with trap sediment building upwards to create a salt marsh.
- only covered at high tide = flowers develop.
rock hardness
some rocks are more resistant and erode differently
eg) granite erodes slowly and becomes angular
rock structure
joined and fractured rock vs solid blocks due to make up of tectonic movement
eg) limestone is jointed
structural alignment
angle of layers in relation to coastline - influencing rate of erosion and shape of cliff.
eustatic change
change in sea level relative to the land.
caused by a change in the volume of water in the sea or a change in the shape of the ocean basin.
has a GLOBAL effect
cause of eustatic change
climate change:
- increase temp = melting of ice sheets & thermal expansion
- decreased temp = more snow, increasing water stored in glaciers, decreasing sea level.
tectonic activity:
- increase/ decrease size of ocean basin
isostatic change
change in height of land relative to mean sea level. LOCAL scale.
downward movement = relative SL rise
uplift = SL falls (locally)
cause of isostatic change
1) isostatic recovery of land due to melting ice sheets
2) post glacial readjustment
3) subsidence due to shrinkage, eg) after abstraction of groundwater
4) tectonic processes
how have sea levels changed over the last 10,000 yrs
as temperature rose, ice sheets melted and sea level rose rapidly reaching its present level 4000 yrs ago
what causes sea level change on a daily basis?
tidal cycle
onshore wind
low atmospheric pressure systems
impacts of sea level rise on coastal areas?
- more frequent and severe flooding
- submergence of low lying islands (Maldives)
- changes in the coastline
- contaminated water sources and farmland
raised beaches
eustatic fall of sea level or isostatic recovery = beaches are left above the high tide mark so become colonised by vegetation and develop into soil.
relict cliffs
cliff lines which are much higher than current sea levels. Wave cut platforms, and headland features are left above than the high tide mark.
Rias
flooded river estuaries with valley sides emerging
the flood plains become submerged by SL rise.
deepest at the mouth, narrower and shallower inland.
Dalmatian coastline
sea level rise, filling hill valleys and dividing hills leaving islands parallel to the coastline.
fjords
glacial troughs (u shaped) that become flooded. leaving deep inlets with near vertical cliffs arising from either side.
changing landscapes: process sequence
development of a landform in multiple landform stages evident along the coastline.
changing landscapes: casual sequence
consequential change.
eg) chalk cliffs erode = pebble beaches
and sandstone = sandy beaches.
changing landscapes: spatial sequence
area zonation
erosion from one place results in deposition of another
changing landscapes: temporal sequence (time)
simultaneous and successive
simultaneous= rising sea level on a slowly emerging coastline (isostatic recovery) = maintenance of sea level
successive = erosional features developing into a cliff line of relic and raised beaches
by 2100 the IPCC predicted a sea level rise of ?
0.44 - 1m
since the last glacial period, how much has the sea level risen by?
125m
the las 3000 yrs have been stable until the 19th century where sea levels rose by?
6cm
how much did sea levels rise in the 20th century?
19cm
