Coastal systems and landscapes Flashcards
what is an open system?
a system which both mass and energy are allowed to transfer across system boundary.
there may be flow of matter as well
what are some examples of a open system?
- the sun
- the coast
what is a closed system?
a system where there may be a flow of energy into or out of the system but no matter flow takes place across the system boundary.
what are some examples of a closed system?
- the earth
- tiny asteroid strikes
what is a subsystem?
a set of elements that is part of a larger system
what is an isolated system?
when there is no interaction between the system and its surroundings.
these types of systems are only theoretical
what are some examples of energy inputs?
- wind
- waves
- tides
what are some examples of stores and processes?
- beaches
- dunes
- salt marshes
- wave cut platforms
what are some examples of material inputs?
- marine e.g products of cliff erosion, sub aerial erosion, fluvial and glacial processes
- rivers
- freeze thaw weathering
what are outputs?
energy and material- some retained within the coastal system
what are inputs?
material or energy moving into the system from outside
what is energy?
power or driving force
what are flows/transfers?
the links or relationships between the components
what is negative feedback?
where a flow/ transfer leads to decline which lessens the effect of the original change
what is positive feedback?
where a flow/ transfer leads to increase or growth
what is dynamic equillibrium?
a state of balance within a constantly changing system
All beaches exist in dynamic equilibrium involving four factors:
1) the supply of sand
2) the energy of waves
3) changes in sea level
4) the location of the shoreline
what is a sediment sink?
when sediment is permanently lost due to lack of energy
what does a feedback loop require?
a shock to the system
does a positive feedback loop make the loop bigger or smaller?
bigger
how is no vegetation on a cliff an example of a positive feedback loop?
no vegetation means erosion occurs quicker due to no support from the roots and so erodes more and more vegetation
what is a sediment budget?
the net sum value between quantities of input and output of sediment in a system
what is a sediment (littoral) cell?
a section of the coastline in which sediment is recycled but not added to or lost
what is a pressure gradient?
how fast the pressure changes between two places
what is pressure measured in?
bars/millibars
what is the global air pressure?
1bar/ 1000 millibars
which way in a pressure gradient does wind blow?
high pressure to low pressure
what are tsunamis caused by?
seabed movement due to seismic shift
what causes changes in pressure?
change in temperature
what type of pressure does riding temperature cause?
low pressure
what is atmospheric pressure?
measure of the weight of the atmosphere on the ground
why cant gas hold large pressure changes?
it doesn’t have the structural integrity
what is an oscillatory wave?
a wave in open ocean with full circular motion particles
what is a translatory wave?
a breaking wave in which circular motion is broken by basal friction
what is fetch?
the length of ocean over which winds blow from a constant direction
waves with no ________ cant erode?
energy
how are big waves formed (like in Hawaii)?
- geology
- long fetch
- consistent wind
what are prevailing winds?
wind that consistently blow from the same direction
what are storm surges?
if an intense area of low pressure resides over the ocean, the reduced aur pressure allows the sea surface to rise higher than in surrounding areas of higher pressure. this creates a pressure wave that may encounter the coast as a storm surge of higher water
what do constructive waves do to beaches?
builds them up
what are some characteristics of constructive waves?
- small in height
- low energy
- strong swash
- weak backwash
- little erosion
what are some characteristics of destructive waves?
- tall in height
- high in energy
- weak swash
- strong backwash
- scours the beach
what do destructive waves do to beaches?
destroys them
what is a headland?
a coastal landform which is a point of land usually high and often with a steep drop that extends out into a body of water
what is a cape?
a headland of considerable size
what happens to waves at headlands?
they bend round the headland and have a higher frequency on the promontory (convergent waves)
what happens to waves in bays?
waves splay out (divergent waves) and are less frequent, having less energy and producing a more constructive impact
what are swash aligned beaches?
when the wave hits the beach at 90 degrees
what are drift aligned beaches?
when the wave hits the beach at a random angle other than 90 degrees
where are the waves convergent?
on a headlands
where are the waves divergent?
bays
where is backshore?
the area between the high water mark and the landward limit of marine activity. changes normally take place here only during storm activity
where is foreshore?
the area lying between the high water and the low water mark. the most important zone for marine processes
where is inshore?
the area between the low water mark and the point where waves cease to have any influence on the land beneath them
where is offshore?
the area beyond the point where waves cease to have an impact upon the seabed and in which activity is limited to deposition of sediments
where is nearshore
- the area extending seaward from the high water mark to the area where waves begin to break
- foreshore + inshore
where is the swash zone?
the area where a turbulent layer of water washes up the beach following the breaking of a wave
where is the breaker zone?
the area where waves approaching the coastline begin to break, usually where the water depth is 5-10m
where is the surf zone?
the area between the point where waves break and where the waves then move up the beach as swash in the swash zone
what controls the tides?
the sun and moon
does the sun or moon have a bigger gravitational pull?
sun
the sun and moon have the ________ pull on earth because _____________________?
- same
- the sun is further away than the moon
why is there hardly any tidal range in the Mediterranean?
there is only a very small opening that connects the med to the other seas, when the tide comes in and out, the water cant travel through the gap fast enough to cause large tide changes like the rest of the word
what is the Severn bore?
a large surge wave that can be seen in the estuary of the river Severn
what causes the sea to change density?
- saltiness
- temperature
what is a current?
a permanent or seasonal movement of surface water in the seas and oceans
what is upwelling?
water coming up to the surface
what are rip currents?
strong localised underwater currents that occur on some beaches, posing a significant danger to swimmers and surfers
how do storm surges occur?
when meteorological conditions giving rise to strong winds can produce much higher water levels than those at high tide
what are some factors that contribute to storm surges?
- low pressure systems/depressions (main factor)
- strong winds ahead of storm
- shape of the area e.g funnel shaped bays
- length of fetch
- high tides
- high river discharge
what was the height of the storm surge in hurricane Katrina?
over 10 metres
why does low pressure cause storm surges?
because it takes the weight of the atmosphere off of the ocean, giving the water particles more room to spread out
what are currents driven by?
- wind
- tide
- heat/ salinity
- thermohaline circulation
what is an example of currents being driven by wind
the north Atlantic drift is a current that is pushed by the gulf stream, which is a wind current and an ocean current
what is the worlds largest current?
- the kuroshio current
- water travels 25-75 miles a day, which is equal to the amount of water of 6000 large rivers
how does the UK stay warm?
the gulf stream comes up from the Caribbean
which ocean is the only ocean to go all the way round the world?
the southern ocean
what is the NOAA?
National Oceanic and Atmospheric Administration
how far down does wind go in the sea and what does it cause?
- 5-10m
- creates waves
what is a flood current?
when the tide goes up and the water moves inland
what is an ebb current?
when the tide goes down and the water moves out to sea
how does temperature affect density of oceans?
cold water is more dense than hot water
how does salinity affect density of oceans?
the saltier the water, the more dense it is
what is the great ocean conveyerbelt?
the sinking and rising of ocean currents all over the world that are connected
how long does it take water to travel round the great ocean conveyerbelt?
1000 years
why do oceans need a lot of energy to change temperature?
because the have a high specific heat capacity
what are tide patterns influenced by?
- ocean bed
- weather conditions
- rivers
- shape of coastline
what is a tidal range?
the difference between high and low tide
where are tidal ranges high?
in very narrow necks of water, like the English channel
tidal ranges will determine the rate of ________?
erosion
what are tides?
the periodic rise and fall of the sea surface
how are high tides formed?
when the moon pulls water towards it, there is a compensatory bulge on the other side of the world, and everything in these two locations is t high tide.
when do the highest tides occur?
when the moon, sun and earth are all aligned and so the gravitational pull is at its strongest
what are spring tides?
the highest of highest and lowest of lowest tides where earth is between the moon and sun
how often do spring tides occur?
twice a lunar month
what are neap tide?
the lowest of highest and highest of lowest tides where the moon and sun are at right angles to each other, and so the gravitational pull is at its lowest
macrotidal definition
areas with a tidal range in excess of 4m
microtidal definition
area with tidal range of less than 1.8m
mesotidal definition
between 1.8m and 4m
what are estuaries?
when the river becomes salty
what is a coastal sediment budget?
the balance between sediment being added to and removed from the coastal system
what are some human things that disrupt the dynamic equilibrium?
- sea wall
- offset groynes
- gabions
what are some physical things that disrupt the dynamic equilibrium?
- sand dunes
- sediment sinks
- transport corridors
what is erosion caused by?
tides, currents or waves
how long has erosion been going on since?
since oceans developed
what is the difference between erosion and weathering?
in weathering the sediment stays in situ
how do sea levels rise?
- ice melting
- thermal expansion
what are the different types of erosion?
- hydraulic action
- attrition
- solution (corrasion)
- abrasion
what two types of processes erode the coast?
- marine processes
- sub-aerial processes
what are the different types of coastal processes?
- weathering
- deposition
- transport
- erosion
- mass movement
what is strata?
the structure of rock
what are some factors that effect coastal erosion?
- waves
- rock type
- geological structure
- coastal management
- hydraulic action
- wave steepness
- wave quarrying
what is the hardest rock?
granite
what is aeolian deposition?
the deposition of sediment by wind
what are some ways sand can travel through wind?
- surface creep
- saltation
what are the four types of transportation?
suspension, solution, saltation and traction
what is suspension?
when fine material such as clay and sediment is carried by the sea
what is solution?
dissolved minerals that are carried by the sea
what is traction?
large boulders and pebbles are rolled along the sea bed
what is saltation?
small stone, pebble and silt bounce along the sea bed
what are the types of mass movement?
- soil creep
- landslides- rockfalls
- rotational slumping
- mudflows
what are subaerial processes?
processes which weaken the rocks and allow erosion and mass movement to occur more easily
where do subaerial processes operate?
on the land
what is weathering?
the break down of rocks or minerals, but they stay in situ
by how much does water expand when it turns to ice?
10%
what is scree/ talus?
piles of stones at the bottom of cliffs, which creates beaches
what must a rock be for wetting and drying to affect it?
porous
how does wetting and drying break down rock?
it weakens the rocks over time as their molecules keep expanding and shrinking, damaging the integrity of the rock each time
where does chemical weathering occur?
on coasts where rocks are exposed to air and moisture
what are the types of weathering?
- chemical
- mechanical
- biological
what type of weathering has the biggest impact on the coast?
mechanical
where does mechanical weathering occur?
on coasts that depends on the nature of the climate
what is an example of mechanical weathering?
- freeze thaw
- salt crystallisation
- wetting and drying
what is an example of chemical weathering?
chemical reactions
what does biological weathering include?
processes that lead to the breakdown of rocks by the action of vegetation and coastal organisms
what factors effect the rate of weathering?
- precipitation
- temperature
- strata of rock
- wind
- climate
- saltiness of water
what is mass movement?
the downhill movement of material under the influence of gravity
what are some natural factors that can cause landslips?
- rock type
- slope angle
- water
- human contributions
what type of rock is unstable at angles bigger than 10 degrees?
clays
the steeper the gradient of the slope, the _______ likely it is to fail?
more
why does water increase likelihood of a landslip?
it adds weight and acts as a lubricant
what are some human contributions that increase the chances of a landslip?
- building at top of slope
- poor drainage
- removal of veg
- creation of impermeable surfaces
- excavation
what happened in the Holbeck landslide in 1993?
a rotational landslide involving 1 million tonnes of glacial till cut back the 60m high cliff by 70m
what was the likely cause of the Holbeck landslide?
a combination of high rainfall (140mm in 2 months) and issues relayed to slope drainage
when can slumps occur?
after heavy rainfall or an earthquake
what degrees of slope to creeps usually occur on?
about 5 degrees
what do soil creeps produce?
terracettes
how do sides of headlands get eroded?
wave refraction
what is the sequence of events in the formation of a wave-cut platform?
1) the sea attacks a weakness in the base of the cliff
2) a wave-cut notch is created by erosional processes
3) as the notch becomes larger the cliff becomes unstable and collapses as the result of gravity
4) the cliff retreats inland
5) the material from the collapsed cliff face is eroded and transported away. this leaves a wave-cut platform
6) the process is repeated overtime
what is an offshore bar?
submerged ridges of sand deposited off the coast (only seen at high tide)
what is a barrier beach?
- sometimes considered the same as a bar
- a sand ridge that rises slightly above the surface of the sea and runs parallel to the shore, which is separated by a lagoon
what is a barrier island?
when a barrier beach is completely separated from the mainland (much further away from the coastline)
why is backwash weaker on shingle beaches?
the water goes through the stones instead of running over the top
what is a storm beach?
the back of the beach, which is composed of big boulders and has a strong swash at spring high tide, which creates it
what is a berm?
below the storm beach there is a series of ridges marking the successively lower high tides as the cycle goes from spring to neap
why does sand beaches have a gentler gradient?
- water can’t percolate sand as easily so doesn’t drag back as much sediment
- larger sediment can stack easier
what does leeward mean?
the sheltered side
what does windward side mean?
non-sheltered side
what are some uses of an estuary?
- carbon sink
- farming (livestock)
- natural coastal defences
- purifies water
- bird spotting
what is the formation of a salt marsh?
- first mudflats are created on sheltered shorelines that are not exposed to powerful waves (low energy environment so sediment is dropped)
- low lying veg (eelgrass) may begin to grow
- more plants grow which traps more mud
- land rises above sea level and eventually leads to tree growth
what is an example of a mudflat?
Keer estuary at Morecambe bay
what is needed for the formation of mudflats?
- sheltered coastline
- low lying
- submerged at high tide
- at an estuary
what are some characteristics of salt marshes?
- high oxygen content
- high nutrient availability
- light availability
- productive and fertile
- has salt loving plants (halophytic)
- an important store of sediment
what is needed for the formation of salt marshes?
- mud and fine sediment
- sheltered area e.g behind a spit
- colonization by halophytic (salt loving) plants
what is bioconstruction?
deposition as water slows down over vegitation
what is flocculation?
when clay particles stick together and are deposited
where is the sward zone in a salt marsh?
flat area covered by the sea for less than one hour every tidal cycle (top of salt marsh)
where is the pioneer zone in a salt marsh?
the area below the sward zone (middle zone of the salt marsh)
where is the salt pans in a salt marsh?
hollows devoid of most vegetation (bottom zone of salt marsh)
what is eustatic change?
world wide changes in sea level caused by glacial and interglacial periods
what is isostatic change?
localised and relative change in sea level caused by the crusts response to loading and unloading of ice
when does eustatic sea level change occur?
when there is a global change in the amount of water stored in the oceans, or a change in the geometry of the ocean basins which alters the volume of water they can hold
what is a ria?
a steep sided, v-shaped, valley formed by glacial rise in sea levels
what is a fjord?
a glacial trough that has been flooded by rising sea levels
how to Dalmatian coasts form?
- rivers flow parallel to the coastline which creates valleys
- when sea levels rise they flood creating ridges of land
what are emergent landforms caused by?
drop in sea level or land raised
what are submergent landforms caused by?
subsidence of land or by rise in sea level
what are some examples of soft engineering?
- beach nourishment
- cliff regrading and drainage
- dune stabilisation
- marsh creation
what are some advantages of beach nourishment?
- relatively cheap and easy to maintain
- it looks natural and blends in with existing beaches
-increases tourist potential by creating a bigger beach
