Coastal Environments- A-Level

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parts of a system
input, flow, store, output, feedback loop
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what type of system is the coast and why
open system because sediment can enter and leave it
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how many sediment cells in England/Wales and what type are they
11, self-contained/closed systems- due to topography of coastline, sub-sediment cell- open system
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3 longest cells
St Abb's Head to Flamborough Head, River Thames to Selsey Bill, Portland Bill to Lands End
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is a sediment cell a completely closed system
No- variations in wind direction and tidal currents
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name the physical factors that affect the coastline
wind, waves, tides, geology, currents
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what causes wind
difference in energy input from the sun at the poles compared to the equator, causes hot air to move from the equator to the poles and vice versa to balance temperature difference
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what causes wind waves
wind waves: wind speed is greater than the speed of a capillary wave (ripples on the surface)
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what causes storm waves
weather events
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what are swell waves
waves that have moved far from their origin
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what causes tides
gravitational forces from the moon and sun- a tide is where water is pulled towards them
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what causes high/low tide
high tide is when the moon pulls water towards it, mirror high tide on opposite side of the world. high tide moves around the world as the moon orbits, low tide in-between bulges
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what is a spring and neap tide
spring tide- when earth, moon and sun are lined up- highest tidal variation. Neap tide- when they are all at right angles, smallest tidal variation
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where is the smallest and largest tidal range
largest- 17m- Bay of Fundy, Eastern California. Smallest- less than 1m- Eastern Mediterranean
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how does tidal range affect erosion
small tidal range = concentrated erosion and vice versa
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what are the parts to geology of the coastline
rock jointing, bedding and faulting, permeability
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what are joints, bedding planes and faults
joints- cracks that run vertically. bedding planes- cracks that run horizontally. faults- cracks due to tectonic movement that shift big rock. all cracks speed up denudation
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what is primary and secondary permeability
primary permeability- small interconnected holes within called pores e.g. chalk. secondary permeability- natural joints and bedding planes that allow water in e.g. limestone.
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which erode faster
permeable- larger surface area
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what are strata
layers of rock that build up the crust of the earth. through tectonic movement, they can be thrust parallel to the coast- concordant, or adjacent to it- discordant
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characteristics of a discordant coastline
headlands and bays. resistant rock sticks out and weak get eroded
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characteristics of a concordant coastline
coves. breach at weakness in resistant rock allows sea to access weaker rock behind it
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what does dip refer to
angle of bedding planes relative to horizontal. if cliffs dip towards the sea they will be eroded faster than towards land
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what are currents
fast moving streams of water within seas and oceans. they can be local/nearshore e.g. rip currents or global.offshore e.g. global ocean conveyor system
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characteristics of rip currents
flow from the coast back out to sea, can be 2.5m/s, occur when a sand bar or reef lies off shore parallel to coast with a gap in it, returning water from swash will flow to gap causing a rip current
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what can rip currents cause
cusps- an arc pattern of sand, to form on a beach due to currents pulling sediment out to sea
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characteristics of global currents
caused by equator gaining more solar energy than the poles, temperature difference causes warm water to flow from the equator to the poles along the surface and vice versa
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example of a warm ocean current
Gulf Stream- from Caribbean Sea to Norwegian Sea. currents affects climate which affects denudation rates along coasts.
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currents link to weathering
warm currents speed weathering up and vice versa
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what are the five terrestrial sediment sources
fluvial deposition, cliff weathering and mass movement, marine erosion, longshore drift, aeolian deposition
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what is the marine sources of sediment
marine deposition
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what is the human source of sediment
beach nourishment
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what are the reasons for coastal landforms developing
geomorphic processes, fluvial processes, aeolian processes
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what are the geomorphic processes
weathering, mass movement, wave erosion, wave deposition, wave transportation
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what is weathering
break up of rocks into smaller fragments that remain in situ, and dissolved compounds by physical, chemical and biological processes
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what is physical weathering
freeze thaw, pressure release, thermal expansion, salt crystallisation- all occur most in areas with large diurnal temperature ranges, less likely to be coastal
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what is chemical weathering
oxidation, carbonation, solution, hydrolysis, hydration- the warmer it is, the faster chemical reactions so larger effectst
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what is biological weathering
tree roots and burrowing animals, organic acids e
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what is mass movement
after weathering, the particles only remain in situ if the friction is greater than gravity, if not then mass movement occurs. so if friction is reduced or effect of gravity is increased
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what are the types of mass movement
rock fall (rocks dropping when steep slope), flow (less steep & saturated, flow like liquid), slide (where defined bedding planes rock moves as a slide)
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what are the types of wave erosion
abrasion/corrasion, attrition, solution/corrosion, hydraulic action, pounding
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what is wave deposition
when kinetic energy falls, the sediment will be deposited, larger particles will be deposited first as the larger the mass, the more energy required to transport it
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what are the types of wave transportation
traction (large particles dragged along the bed), suspension (very small particles carried in water), solution (salts dissolved in sea water), saltation (small pebbles bounce along the base of the wave)o
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how does the river discharge affect the erosion rates
when the river discharge is high and the river is in flood, more materials is eroded and transported by the river to the coast, when it meets the sea the velocity is reduced causing deposition.
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what does fluvial deposition cause
mudflats, deltas and salt marshes
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what is aeolian deposition and what does it cause
deposition occurs when velocity falls due to increase in friction as it blows inland, this can cause sand dunes
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how is material moved by the wind
suspension (very fine material picked up and carried high into air by dust storms), Saltation (fine material is picked up and carried to a max height of 1m and bounced along ground), Surface creep (coarse materials is rolled along the ground surface)
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what are the erosional landforms
headlands and bays, cliffs and platforms, geos and blowholes, caves and arches and stacks and stumps
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what causes headlands and bays
where bands of more resistant and less resistant rock are found perpendicular to the coast- discordant coastline. e.g. Swanage. shallower water off headlands cause wave velocity to reduce as friction increases. not in bays so wave refraction occurs
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what is the wave attack zone
between the high and low water mark
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how is a geo formed
where there is a particularly weak joint in resistant rock, erosion will enlarge it. this first forms a cave perpendicular to the cliff which if it becomes large enough roof will collapse and leave an inlet called geo. common in Cornwall
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how is a blow hole formed
if the rock is particularly resistant then a cave won't form and erosion will continue along the joint and may cause passage to surface forming a blow hole
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what are examples of depositional landforms
beaches, spits & tombolos, onshore bars, salt marshes and deltas
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what are beaches made of
90% of the sediment on a beach comes from rivers, 5% from offshore sources and 5% from cliff retreat
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what are the parts of a beach
lower beach- made of finer sediment and maintained during day to day normal wave action. upper beach- made of coarser sediment and formed during infrequent storm events where waves have enough energy to move large particles up the beach- storm beach
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what are short term changes of a beach
cusps form when waves hit the beach at same point with equal swash and backwash energy. cuts a temporary shallow depression. depression is deepened by a stronger backwash that forms due to a process like a mini-rip current
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what are medium term changes of a beach
winter- storms more frequent so erosion of the lower beach occurs, removing berms and forming a near shore bar. summer- waves have less energy so less erosion occurs and the lower beach and berms rebuilds
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examples of spits, bars and tombolos
spits- Sandbanks, Bars- Slapton Ley, Tombolos- Chesil Beach
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what causes salt marshes and mudflats
where waves lose energy they deposit material, this occurs the landward side of spits and in the mouths of river estuaries. deposition occurs more rapidly in river estuaries as clay particles stick together through flocculation when water is brackish
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how is a delta formed
when a river reaches the sea its velocity and so energy level drops. the river therefore deposits material. when wave erosion is a smaller output than sediment input, sediment builds up formed a delta. the river channel splits formed distributaries
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what are the three types of delta
arcuate (fan shaped), bird's foot, cuspate (tooth shaped)
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what are the types of sea level fall
eustatic sea level change and isostatic sea level change
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what is eustatic sea level change
the sea level falls as there is less water in seas and oceans and more ice on land
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what is isostatic sea level change
the sea level falls as the land rises up, there is no change to the volume of water in seas. any sea level change is due to both factors as they occur at the same time just at different rates
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what cause sea level fall
climate change- caused by orbital eccentricity, axial tilt, equinox precession, solar cycle and a geological factor
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what is orbital eccentricity
earth changes orbit from circular to elliptical over 100,000 years. circular orbit means earth is closer to the sun so warmer. elliptical orbit means the earth is further away and cooler
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what is axial tilt
the earths axis changes by 2.4° every 41,000 years. when the tilt is at its maximum, earths summer is hotter and winter is colder
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what is equinox precession
the gravity of other bodies cause the earth's axial spin to wobble, making a circle over 22,000 years. when the northern hemisphere is pointing to the sun at perihelion the temperature range between summer and winter is greater
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what is a solar cycle
sun has a cycle of 11 years, over which the amount of radiation increases and then decreases. over a longer period, the cycle changes with minimum and maximum numbers of sun spots. impact is complex
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what is the geological factor
volcanic activity- short term- emit large amounts of ash which stay in stratosphere for months and reflect incoming solar radiation, causing cooling. also give off sulphur dioxide which reacts to form sulphuric acid which is also highly reflective
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example of volcanic eruption having an impact
Mount Pinatubo erupted in 1991, emitted so much sulphur dioxide that earth's climate cooled by 1.3°C from 1991-1994
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how does a cooling climate reduce sea level
by changing the balance of ice on land vs water in the seas and oceans. as temperature falls, more precipitation turns to snow and ice on the land and less melts, therefore glaciers and ice caps grow, oceans shrink in volume
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what landform does sea level fall produce
raised beaches- when sea level falls, it can leave several raised beaches above the current one. raised cliffs and raised wave cut platforms can also be found. e.g.- Langerstone Point, Devon
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what happens once an emergent coastal landform has been formed
it will start to be destroyed by denudation- biological weathering will increase, chemical weathering will increase, physical weathering will increase
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what causes sea level rise
temperature rises so less precipitation turns to snow and ice on the land and more ice melts, therefore glaciers and ice caps shrink in size, oceans and seas grow in volume
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what also causes sea level to rise
when temperatures are higher, thermal expansion of the seas and oceans occur. it is though that a 1°C rise in temperature would lead to a 2m rise in sea level
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how much did sea level rise in the Flandrian Transgression
the last glacial period is known as the Wurm glaciation, the warming that has occurred over the last 25,000 years caused a rise in sea level called the Flandrian Transgression, sea level was lower by about 120m
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what three features form due to sea level rise
rias, fjords and shingle beaches
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what is a ria and an example
river valleys that have been flooded by the rise in sea level. gentle sloping sides, irregular winding course. The Kingsbridge estuary, Devon. 4 miles long and 0.3 miles in width at widest point
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what is a fjord and an example
glacial U-shaped valley that has been flooded by sea level rise. deeper and narrower than rias and can extend hundred miles more inland. often shallow nearest the sea as glacial erosion was weakest here. Example is Milford Sound, New Zealand
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what effect is global warming having on fjords
increased global warming and further rise in sea level are likely to also increase the water depth in fjords and increase denudation to the valley sides
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what caused shingle beaches
during Warm Glacial period when sea level was lower, fluvial sediment built up in these paleo-coastal areas. joined by deposited glacial sediment as sea level rose from 25,000BP the sediment was pushed ashore
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what is an example of a shingle beach
chesil beach- during Flandrian Transgression in UK, large quantities of sediment were moved around 50km onshore by the rising sea level until sediment hit the land around Portland
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what effect is global warming having on shingle beaches
likely to be damaged by erosion due to increase in warming of climate. due to sea level rising further and there being an increase in stem frequency. both will increase the magnitude of marine erosion
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what are the four types of coastal management plans
hold the line (Mappleton on Holderness Coast), advance the line (NW Netherlands), retreat the line (Blackwater estuary, Essex), do nothing (St Aldheim's Head, Dorset)
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coastal management strategies
groynes, gabions, sea walls, revetments, beach nourishment, rock armour/riprap, breakwaters, managed retreat. see table in notes
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examples of economic development of coastal areas
coastal development: Australia, Brazil, UAE has seen extensive coastal development for mainly residential and tourist uses. Mineral resource exploitation: Netherlands, NZ have engaged in large scale offshore dredging for sand and gravel minerals
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Card 2

Front

what type of system is the coast and why

Back

open system because sediment can enter and leave it

Card 3

Front

how many sediment cells in England/Wales and what type are they

Back

Preview of the front of card 3

Card 4

Front

3 longest cells

Back

Preview of the front of card 4

Card 5

Front

is a sediment cell a completely closed system

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