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- 1Whats a coastal environment??The point at which the land meets the sea. This is a dynamic concept (i.e. not static) due to tides (2 per day)
- 2Define LWM and HWM?LWM- low water mark (usual low tide)
HWM- high water mark (usual high tide) - 3Draw a diagram of coastal environments?
- 4define backshore??is the area between the high water mark and the landward limit of marine activity. Changes normally take place here only during storm activity
- 5define foreshore?Foreshore is the area lying between the high water mark and the low water mark. It is the most important zone for marine processes in times that are not influenced by storm activity
- 6define inshore??Inshore is the area between the low water mark and the point where waves cease to have any influence on the land beneath them
- 7define offshore??Offshore is the area beyond the point where waves cease to impact upon the sea bed and in which activity is limited to deposition of sediments
- 8What are the factors that affect the coastline?? e.g. wave: size, frequency, type, energy produced and direction; local sea currents; longshore drift; tides; depth of water offshore; type + amounts of sediment offshore; rock type + structure; sub-aerial processes – runoff, weathering + mass movement; land-based agents of erosion – rivers and glaciers; climate+ weather;
- 9What factors affect coastal environment contd??fetch – distance over open sea that wind blows 2 generate waves; longer the fetch, greater potential 4 large waves; long-term sea level change – eustatic (sea level changes) + isostatic (land level changes); coastal ecosystems – sand dunes, salt marshes + mangroves; presence of coral; human activity
- 10Coastal system What is a coastline regarded as??A coastline is regarded as an open system because inputs are received and outputs are transferred, across the boundary of the system.
- 11Inputs consist of??Energy
sediment
changes in sea level
human activity - 12The input energy is used to drive the system what provides the energy??This is provided by waves, winds, tides and currents. The input is irregularly boosted by storm surges and tidal waves
- 13inputs : energy Spatial variations in energy result from variations in...........???strength of wind,
fetch and the number and intensity of the storm. Storms are most frequent in mid-latitudes where low pressure systems often dominate and in the tropics where low pressure systems (tropical storms/hurricanes) occur. - 14inputs : energy There are also temporal variations on a seasonal and even daily scale. give an example??For example in the mid latitudes depressions are more frequent in winter whereas in the part of the tropics that is in the northern hemisphere, the hurricane season is in late summer and autumn.
- 15Inputs: sediment how is sediment provided to the system??provided within system from erosion of coastlines by waves. but most sediment comes from outside the system. brought mainly by rivers that transport a whole range of different sediments from land to sea. Weathering + mass-wasting also contribute material from cliff faces
- 16Name the coastline processes?Coastline processes are mainly those associated with erosion, constructive wave’s action, longshore drift and the wind
- 17What does longshore drift do??Longshore drift is the main agent that relocates materials from coastlines dominated by erosion processes to areas where depositional landforms are constructed, such as beaches, spits and bars. Wind can also carry material in this case from the shoreline inland.
- 18what are the outputs of the coastal system??Coastal landforms, both erosive and depositional
accumulations of sediment above the tidal limit
loss of wave energy - 19how are waves created??Waves are created by a transfer of energy from the wind blowing over the sea surface. The energy acquired by waves depends on the strength of the wind, the length of time that it has been blowing and the distance over which it blows (fetch).
- 20What happens when waves approach shallower water??As waves approach shallower water, friction with the sea bed increases and the base of the wave begins to slow down. This has the effect of increasing the height and steepness of the wave until the upper part plunges forward and the waves 'break' onto the beach.
- 21what are the features of a wave??The rush of water up the beach is known as the swash and any water running back down the beach into the sea is known as backwash. Waves can be described as constructive or destructive.
- 22Draw and label a wave??
- 23Draw a labelled diagram of a wave approaching the coastline
- 24describe a constructive wave??Constructive waves tend to be low waves, but with a long wavelength, often up to 100m. They have a low frequency of around six to eight per minute
- 25What happens as the wave breaks?? in terms of wave profile, swash and backwash??As approach beach, wave front steepens only slowly giving a gentle spill onto beach surface. Swash rapidly loses volume + energy as water percolates through beach material. tends 2 give very weak backwash which has insufficient force 2 pull sediment off beach or 2 impede swash from next wave.
- 26What is a consequence of a constructive wave??As a consequence, material is slowly, but constantly moved up the beach, leading to the formation of ridges (berms)
- 27Describe a destructive wave??Destructive waves are high waves with a steep form and a high frequency
Destructive waves are commonly associated with steeper beach profiles. - 28What happens when the wave breaks??As they approach the beach they rapidly steepen and when breaking they plunge down. This creates a powerful backwash as there is little forward movement of water. It also inhibits the swash from the next wave
- 29Whats a consequence of destructive waves??Very little material is moved up the beach, leaving the backwash to pull material away. force of each wave may projects some shingle towards rear of beach where it forms large ridge known as a storm ridge
- 30Draw diagrams of constructive and destructive waves??
- 31Effects of waves: Most beaches are subjected to the alternating action of constructive and destructive waves how so??Constructive waves build up the beach + result in steeper beach profile. This encourages waves 2 become more destructive (destructive waves are associated with steeper profiles). With time, destructive waves move material back towards sea, reducing beach angle + encouraging more constructive waves.
- 32What sort of feedback is this??So, the pattern repeats itself.This type of negative feedback should encourage a state of equilibrium, but this is impossible due to other factors, such as wind strength and direction are not constant.
- 33What happens when waves approach an irregular coastlinesWhen waves approach a coastline that is not of a regular shape, they are refracted and becoming increasingly parallel to the coastline.
- 34Draw a labelled diagram of a refracted wave?? This diagram shows a headland separating two bays.
- 35Describe wave refraction??As each wave nears the coast, it tends to drag in the shallow water which meets the headland. This causes the wave to become higher and steeper with a shorter wavelength. The part of the wave in deeper water moves forward faster, causing the wave to bend.
- 36What is the overall affect of wave refraction??The overall effect is that wave energy becomes concentrated on the headland, causing greater erosion. The low energy waves spill into the bay, resulting in beach deposition.
- 37what happens at the headland due to wave refraction??As the waves pile against the headland, there might be a slight local rise in sea level that results in a longshore current from the headland, moving some of the eroded material toward the bays and contributing to the build-up of beaches.
- 38Erosional landform What are cliffs? E.g. White Cliffs of DoverCliffs are a common coastal landform and is simply rock exposure. Overtime cliffs retreat due to the action of waves and weathering.
E.g. White Cliffs of Dover
- 39Erosional landform Wave cut platformsWhen high + steep waves break at foot of cliff they concentrate their erosive capabilities into a small area of rock face only. usually between high tide + low tide water marks. This leads to the cliffs being undercut, forming a wave cut notch.
- 40what hapens due to continued erosion??Continued erosion at this point increases stress on cliff as it over hangs + in time weight of cliff cannot b supported. As rock above wave cut notch becomes unstable with nothing 2 support it, it collapses normally happens in storms as water acts as lubricant in cracks of rock.
- 41The cliff has therefore retreated, leaving at its base a gently sloping wave-cut platform. what happens to the platform over time??platform continues to grow as process is repeated +as it does waves break further out 2 sea + have 2 travel across a greater stretch of platform to reach cliff face. This leads to a great dissipation of wave energy, reducing rate of erosion on headland + slowing down growth rate of platform.
- 42whats the limit for a wave cut platform??There tends to therefore be a limit as to how large the feature can grow and it is thought that a platform over 500m is unusual.
- 43Draw a diagram detailing how a wave cut platform is formed??
- 44Headlands and bays form where there are alternating bands of resistant and less resistant rock. why is this??The less resistant rocks experience most erosion and develop into bays whereas the more resistant rocks become headlands as they are able to withstand the erosive power of the waves better than the less resistant rock.
- 45how does wave refraction play a part in this??Because of wave refraction, the headlands receive the highest energy waves and are more vulnerable to the forces of erosion than bays are. The bays experience low energy waves that allow sediment to accumulate and form beaches.
- 46Draw a diagram detailing the formation of headlands and bays??
- 47where do coves form?? how do coves begin to be formed??Coves form where rock run parallel with the coast. There is a band of resistant rock closest to the sea and a band of less resistant rock inland. The waves seek out faults in the hard rock and erode it and this continued erosion can break through the more resistant rock, exposing the weaker strata behind.
- 48How are coves formed??Wave processes erode the softer rock faster and this leaves a circular cove with a narrow entrance where the sea enters. The waves are also refracted within the cove, spreading out to erode in all directions. cove will be enlarged by erosion 2 form a bay. e.g. Lulworth cove, Dorset.
- 49Draw a diagram detailing erosional landforms formed on a headland??
- 50How is a blowhole formed??Weaknesses on the cliff such as cracks or joints are eroded firstly to form caves.
Occasionally the roof of a cave is weakened along a major joint normally by hydraulic pressure and the roof collapses and a blowhole is formed. - 51How is an arch formed?However what is much more likely is that erosion will continue backwards into the cave until it eventually meets another cave or the other end of the headland this creates a hole all the way through the headland known as an arch.
- 52How is a stack formed??As the Arch get bigger and bigger it will eventually collapse as the roof of the arch is too heavy to be supported, this leaves and isolated portion called a stack that is standing above the wave cut platform.
- 53How is a stump formed??In time the sea will exploit the wave cut notch at the base of the stack, leading eventually to the top of the stack to collapse and a small raised portion of the wave cut platform is left know as a stump. E.g. old harry rocks, Purbeck.
- 54what are beaches??Beaches represent the accumulation of material deposited between low spring tides and the highest points reached by storm waves.
- 55Beaches r mainly constructed from sand + shingle but these 2 materials create slightly different beaches. How is a sand beach formed??Sand produces beaches with a gentle gradient because the small particle size means the sand become compact when wet and allows very little percolation. Most of the swash therefore returns as backwash, little energy is lost to friction and material is carried down the beach.
- 56What forms on a sand beach??This leads to the development of ridges and runnels in the sand at the low water mark. These run parallel to the shoreline and are broken by channels that drain water off the beach.
- 57Beaches r mainly constructed from sand + shingle but these 2 materials create slightly different beaches. Describe a shingle beach??Shingle may b the whole or just upper parts of beach. larger the size of
material, generally steeper the gradient of the beach. cos water rapidly percolates through shingle, so backwash is somewhat limited. This together with the uneven surface, means that very little material is moved down the beach. - 58Describe the features of a beach??back of beach, strong swash at spring high tide level will create a storm beach – a ridge composed of the biggest boulders thrown by the largest waves.
- 59What is formed below the storm ridge??Below this there will be a series of ridges marking the successively lower high tide as the cycle goes from spring to neap, these ridges are known as berms and are built up by constructive waves.
- 60What are cusps?? They usually occur at the junction between shingle and sand beaches.Cusps r semi-circular shaped depressions which form when waves break directly onto beach + swash + backwash r strong. sides of the cups channel incoming swash into centre of embayment + this produces a stronger backwash in central area that drags material down beach deepening cusp.
- 61What develops below cusps??Below this ripples are developed on the sand by wave action or tidal currents
- 62Draw a detailed diagram of a beach??
- 63what is a spit??A spit is along narrow piece of land that has one end joined to the mainland and projects out into the sea or across an estuary. Like a beach + other depositional landforms its composed of sand +/or shingle + mixture very much depends upon the availability of material and the wave energy required to carry it.
- 64On the diagram above it shows the formation of a spit. On this diagram the prevailing wind and maximum fetch is from the southwest, so material will be carried from west to east along the coast by the process of longshore drift.
- 65How in the diagram has the spit been formed??Where the coastline changes to a more north-south orientation, theres a build-up of sand + shingle in more sheltered water in lee of headland. As this material begins to project eastwards, storms build up more material above high-water mark, giving a greater degree of permanence to feature. Finer material is then carried further eastward, extending the feature into the deeper water of the estuary.
- 66How is a curved end formed??end of the spit begins to curve round (recurrved end) as wave refraction carries material round into more sheltered water.second most dominant wind direction + fetch may contribute 2 this, pushing spit material back towards mainland. Several curved ends may develop during a period of weather until dominant south west weather reasserts itself.
- 67Why cant the spit in the diagram form a bar??The spit cannot grow all the way across the estuary to form a bar as the material is carried seaward by the river and the deeper water. E.g. Hurst castle spit
- 68How is a bar formed??A bar is formed when a spit joins 2 headlands together. This can occur across a bay or across a river bay (if the river isn't too strong). Some bars may simply be the result of the onshore migration of material from offshore as sea levels rose following the last ice age. Slapton ley, is believed to have been formed this way.
- 69Hows a tombolo formed??Tombolo – is a spit that joins an island to the mainland . The best example being Chesil Beach on the south coast of England. This links the Isle of Portland to the mainland and is about 30km long.
- 70what is the coastal system??The coastal system
The area of land affected by the sea and the area of sea directly affected by the land
Can be seen as a number of zones - 71what is backshore??Back shore is usually above the influence of waves but is covered in water during storms and spring tides, the high water mark is where backshore starts/ends
- 72what is foreshore??Foreshore is the inter-tidal or surf zone
- 73what is nearshore??Nearshore is the breaker zone and is always under water unless there is a neap tide
- 74what is offshore??Offshore is beyond the influence of the waves
- 75what are the inputs??energy in the form of:
Waves
Tides
Wind and
Currents
Another input is sediment as a result of the energy - 76outputs include???Outputs include:
Landforms (bit questionable)
Sediment
Energy - 77Inputs of coastal energy 1. Tides what are tides??The result of the gravitational pull of the moon on the oceans (+sun) 2 tides a day
Incoming tide – known as flood
Outgoing tide – known as EBB
Tidal currents are most powerful where there is a funnel shaped coastline e.g. a bay or estuary - 78whats a spring tide??Spring tides
Higher than usual high tide
Lower than usual low tide
Can cause floods
Why? When sun and moon pull in the same direction - 79whats a neap tide??Neap tide
Lower than usual high tide and higher than usual low tide - 80Draw diagrams of the position of the sun moon and earth for the different types of tides??
- 81how is wind an input of energy??Blow sediment from beach onto the back of the beach – creates sand dunes
Wind also creates waves - 82what are the two types of wave??Two types: forced waves and free waves
Free waves start in the middle of the ocean and then carry on moving due to momentum (known as swell)
Fetch – the distance that (free) waves travel over a stretch of ocean
In terms of the U.K - 83how far do winds travel in differnt directions in relation to the uk??South west winds travel 6400km
East winds travels 640km (distance of fetch)
South winds travel 64km
75% of the time we get south westerly winds so lots of rain - 84what are forced waves??Forced waves are waves that are only on the very surface of the ocean and created close to land by strong winds
- 85what are the types of waves and breaking waves??free – formed in the middle of the ocean and then move by wind as a result of momentum (SWELL)
forced – formed close to the coast as a result of storms
types of breaking waves:
1. destructive
2. constructive - 86whats lithology??lithology is the structure and layout of the rocks
- 87what are the two types of coastline??Concordant coastlines are those where rocks are laid out parallel to the coastline and are therefore straighter
Discordant coastlines are those where rocks are at angles to the coastline, therefore are more jagged in appearance due to differential erosion (erosion at different speeds) - 88whats rock dip??the way that rocks have been formed in vertical layers and how these layers currently sit in relation to the coastline
- 89whats a Littoral cells AKA sediment cells??sediment cells are areas of coast where sediment is cycled around via currents, longshore drift, wind and waves.
- 90whats special about littoral cells/sediment cells??Sediment within a cell will not leave to enter another cell
sediment in a cell comes from cliffs and erosion within the cell i.e. closed system
larger cells have sub-cells where the system is mostly closed, but some cell to cell movement occurs - 91what are sub aerial processes??Sub-aerial processes – processes which affect the cliffs/coast outside of the influence of the sea AKA weathering breakdown of rock (in situ)
- 92what are the different types of sub aerial processes??Mechanical: Freezethaw, Rainsplash
Biological: Roots of plants, Burrowing animals
Chemical: Dissolve (limestone), Lichens/mosses – excrete chemicals that breakdown rocks - 93define mass movement??Mass Movement – when weathered rock moves down towards the sea
- 94whats rockfall??Slumping - structural integrity of the cliff is affected usually by being saturated – the rock/cliff can no longer support its own weight and therefore slumps
Landslides / slips - rock rotates on a lubricated fault line and slides downwards - 95what are the different types of erosion??Hydraulic action
Abrasion
Attrition
Solution
Wave pounding / quarrying the energy of a wave when it hits a cliff/rock detaching pieces of weathered rock. - 96High energy and low energy coastlines what is a high energy coastline???High-energy coastlines are those in which wave power is strong for a greater part of the year, for example in the western coast of the British Isles. The prevailing and dominant wind direction on these coasts is westerly and they face the direction of the longest fetch.
- 97What does this high energy coastline mean in the U.K.The maximum recorded wave height on western coasts is therefore greater than on eastern coasts. For example, waves of up to 30m have been recorded on the west coast of Ireland.
- 98What is a low energy coastline and in what environments are these found??Many estuaries, inlets and sheltered bays are low-energy environments where wave heights are considerably lower. Here waves spread outwards and energy is dissipated, leading to the deposition of transported material. Enclosed seas also contain low energy environments.
- 99Give an example of a low energy coastline??The Baltic Sea, for example, contains some of the longest depositional landforms in the world mainly because of its sheltered waters and low tidal range.
- 100what are the features of a low energy coastline??stretches of the coastline where waves are not powerful
often the rate of deposition exceeds the rate of erosion
landforms include beaches and spits - 101what are the features of a high energy coastline??stretches of the coastline where waves are powerful for a significant part of the year
often the rate of erosion exceeds the rate of deposition
landforms include headlands, cliffs and wave-cut platforms - 102whats a storm surge??These are occasions when meteorological conditions giving rise to strong winds can produce much higher water levels than those at high tides.
High tides intensify the effect - 103One area affected by this phenomenon is the North Sea. Why is this??Depressions over North Sea produce low-pressure conditions have the effect of raising sea levels. Strong winds drive waves ahead of the storm + this also builds up water levels. The shape of the area means water is increasingly concentrated into space thats decreasing in size.
- 104whats a tide??Tides are the periodic rise and fall in the level of the sea.
- 105what are tides caused bycaused by the gravitational pull of sun + moon, although moon has the greatest influence because it’s nearer. The moon pulls water towards it, creating a high tide + there is a compensatory bulge on the opposite side of the earth in between these two bulges the tides is at its lowest.
- 106When is a spring and neap tide formed??When the moon, sun and Earth are in a straight line which happens once a month the highest tide is produced known as a spring tide. Twice a month the lowest tidal range occurs when the moon and sun are positioned at 90° to each other this is known as a neap tide.
- 107whats a landslide??Depends on rock dip
water gets into cracks and lubricates it
all rock slides off
rocks form at the bottom of cliff - 108whats sea level change??Sea level change: A change in sea level over time relative to the height of the land
4 types of sea level change - 109what are the short term sea level change??1. Tides – daily
2. Storm Surge – temporary rapid increase in sea level due to a combination of low pressure wind, high tides and often funnel shaped coastal areas - 110long term what eustatic sea level change??Eustatic: when the level of water changes
Today globally sea level is rising eustatically because glaciers melt + increase sea level. Sea levels r also rising eustatically due to thermal expansion, as water heats up it takes up more space - 111Long term whats isosatic sea level change??Isostatic: where the land goes up or down
How/why?
-Tectonic activity
-weight of ice
During global cool periods (ice ages) there is a lot of ice on land and causes the land to sink - 112what are submergent coastline landforms??- Submergent Coastline
submerged coasts – sea level has risen
Rias – flooded river V-shaped valley in valley
fjords – flooded U-shaped valley - 113what are emergent coastline landforms??-Emerent Coasts – sea level has fallen
Relict Cliffs
Raised beaches - 114what are coastal management stratagies??Techniques used by people to manage the coastline usually designed to do 2 things:
1. prevent/limit coastal erosion
2. prevent/reduce the impact of flooding - 115what types of coastal defence are there??Hard engineering
soft engineering
managed retreated - 116what are the 4 options for coastal management??hold the line – to maintain existing coastal defences; Advance the line – usually involves reclaiming land from sea; Do nothing – build no coastal defences + deal with issues when they happen; Retreat the line – move people away from coasts + allow existing defences 2 b destroyed.
- 117what is a coastline of submergence??form as a result of sea level rise. The current period of sea level rise, caused by melting ice sheets and thermal expansion of the ocean is called eustatic change. As a result of eustatic change, a number of coastal features develop, including the formation of fjords and rias
- 118What is a ria and how is it formed??form where river valleys are partially submerged. have a gentle long + cross profile. Theyre wide + deep at mouth, becoming shallower + narrower the further inland they reach. e.g. The Solva Pembrokshire
- 119what do many rias show??Many Rias show meandering as they navigate around interlocking spurs as the water reflects the valley that was previously shaped by river processes.
- 120What is a fjord and formed?? e.g. sognefjorden in Norway is over 1000m deep in some places.Fjords r drowned glacial valleys rather than drowned river valleys. They're relatively straight and narrow with steep sides, a shallow mouth caused by a raised bit of ground (called the threshhold) formed by deposition of material by the glacier.
- 121what can fjords become??They can become very deep inland Fjords have a U-shaped cross profile that was deepened by a glacier, during the last glacial period
- 122what is a dalmation coastline??In areas where valleys lie parallel to the coast, an increase in sea level can form Dalmation Coastline. Vallyes are flooded leaving islands parallel to the coastline. Its named after the Dalmation coast in Croatia
- 123coastlines of emergence??Emergent landforms begin to appear towards end of ice age + occur when isostatic rebound takes place faster than a eustatic rise in sea level. Emergent features r features of coastal erosion that appear to have developed well above the current sea level. Really, they developed when the sea was at that level + then the sea level changed during ice age + now they’re above sea level.
- 124what are raised beaches??these are formed when the fall in sea level exposes wave-cut platforms ad their beaches. Over time, beach sediment becomes vegetated and develops into soil.
- 125what are relict cliffs??cliffs above raised beaches r no longer eroded by the sea + slowly get covered in vegetation. Its not uncommon to see wave cut notches, caves, + arches within relict cliffs. These features r gradually weathered over time but at a much slower rate than when they were the coastline + eroded by the sea.
- 126—
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- AS - Level Geography Flashcards on Coasts notes, created by annabel.jennings on 08/04/2016.
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