Coasts Flashcards

Question

How does geology influence coastal landscapes?

Answer 1

Lithology - The physical & chemical composition of rocks. Clays = weak lithology, bonds between particles are weak. - Basalt = made of dense interlocking crystals = highly resistant - Chalk & carboniferous limestone (predominantly composed of calcium carbonate) = soluble in weak acids & vulnerable to chemical weathering (carbonation) Structure - Properties of individual rock types such as jointing, bedding & faulting - Permeability of rocks - Porous rocks (chalk) = tiny air spaces (pores) separate the mineral particles = absorb & store water = primary permeability - Carboniferous limestone (permeable) = water seeps into limestone due to many joints = secondary permeability. (the joints are easily enlarged by solution!)

Answer 2

Concordant platform - bands of different rock type run parallel to the shore. These rock types are usually of alternating resistance, so the coastline forms distinctive landforms, such as coves. Discordant platform - bands of different rock type run perpendicular to the shore. These have distinctive landforms because rocks are eroded by ocean waves. The less resistant rock erodes faster, creating bays; the more resistant rocks erode more slowly, remaining as headlands.

Answer 3

Rip currents Nearshore & offshore currents have an influence on coastal landscape systems. Rip currents = transport coastal sediment. Caused by tidal motion OR waves breaking at right angles to the shore. Differing wave heights = cellular circulation. Water from the top of breaking waves (with large height) travels further upshore = returns through adjacent area where the lower height waves have broken. = Rip currents = modify shore profile = creating cusps = helps perpetuate the rip current, channelling flow through a narrow neck

Answer 4

Ocean currents = Larger scale phenomena = generated by Earth’s rotation & convection. Set in motion by winds across water surfaces. Warm ocean currents transfer heat energy from low latitudes towards the poles. Affect Western-facing coastal areas where they are driven by onshore winds. Cold ocean currents do the opposite = moving cold water from polar regions towards the equator (usually driven by offshore winds = less effect on coastal landscapes) The transfer of heat energy can be significant on the coastal landscape = air temperature = Subaerial processes.

Answer 5

Sediment budget refers to the balance between sediment added (Input = Sources) to and removed (Output = Sinks) from the coastal system; in this respect the coastal sediment budget is like a bank account. When more material is added than is removed, there is a surplus of sediment and the shore builds seaward Rivers are major sources of sediment input - steep gradient River directly deposit their sediment at the mouth (eg in some locations, as much aas 80% of coastal sediment comes from rivers!) Can be flood induced Fluvial & coastal erosion, subaerial processes, mass movement & transportation = contribution to sediment budget

Answer 6

Buildings, roads, tourism

Answer 7

The movement of seawater in a pattern of flow dependent on variations in temperature, which give rise to changes in salt content and hence in density. Atmospheric winds can also create currents in the water Equator is 0 degrees Latitude and longitude

Answer 8

On or relating to the earth.

Answer 9

Affects ocean currents and direction, Prevailing winds are winds that blow predominantly from a single general direction over a particular point on the Earth's surface. The dominant winds are the trends in direction of wind with the highest speed over a particular point on the Earth's surface.

Answer 10

Aeolian processes, involving erosion, transportation, and deposition of sediment by the wind, occur in a variety of environments, including the coastal zone, cold and hot deserts, and agricultural fields.

Answer 11

EROSION IS THE WEARING DOWN OF ROCK BY MOVING FORCES. This usually occurs at the base of our cliffs and by waves. WEATHERING IS THE WEARING DOWN OF ROCK ‘IN SITU’ BY ITS ENVIRONMENT. Sub aerial forces (like rain, air and temperature) act on the cliffs to break them down. MASS MOVEMENT IS THE MOVEMENT OF ROCK DOWNHILL UNDER GRAVITY. Weathering and mass movement work together. The cliffs are weakened by weathering, pieces of rock are loosened and then they fall away from the cliff (this final stage is mass movement).

Answer 12

Bits of rock and sand in waves grind down cliff surfaces like sandpaper. Attrition. Waves smash rocks and pebbles on the shore into each other, and they break and become smoother.

Answer 13

The particles are knocked about as they are transported, and they gradually become more rounded and reduced in size.

Answer 14

Erosion that occurs when the motion of water against a rock surface produces mechanical weathering. Most generally, it is the ability of moving water (flowing or waves) to dislodge and transport rock particles.

Answer 15

Water dissolves minerals from the rocks and washes them away.

Answer 16

Wave pounding is the 'sledgehammer' effect of tonnes of water crashing against cliffs.

Answer 17

Chemical: The decay of rock due to chemical reactions between moisture & some minerals within the rock May reduce the rock to its chemical constituents or alter its chemical & mineral composition Most chemical reactions increase with temperature. Van’t-Hoff’s aw states that a 10⁰C increase = 2.5 increase in the rate of chemical reaction (up to 600⁰C). But carbonation can be more effective in cold, dry locations as C0₂ is more soluble in cold water than warm. Biological: Growth of plant roots, borrowing or chemical processes such as chelation by organic acids. Physical/mechanical weathering: Increases the exposed surface area of the rock, allows further weathering.

Answer 18

Water molecules added to rock mineral create new minerals of a larger volume. This happened when anhydrite takes up water to form gypsum. Hydration causes surface flaking in many rocks, partly because some minerals also expand about 0.5% during the chemical change because they absorb water.

Answer 19

Rainwater combines with dissolved C0₂ from the atmosphere to produce a weak carbonic acid. This reacts with calcium carbonate in rocks such as limestone to produce calcium bicarbonate, which is soluble. This process is reversible & precipitation of calcite happens during evaporation of calcium rich water in caves to form stalactites & stalagmites.

Answer 20

Some salts are soluble in water. Other minerals, such as iron, are only soluble in very acidic water, with a pH of about 3. Any processes by which a mineral dissolves in water is known as solution, although mineral specific processes such as carbonation, can be identified.

Answer 21

Some minerals in rocks react with oxygen, either in the air or in water. Iron is especially susceptible to this process. It becomes soluble under extremely acidic conditions and the original structure is destroyed. It often attacks the iron-rich cements that bind sand grain together in sandstone.

Answer 22

This is a chemical reaction between rock mineral & water. Silicates combine with water, producing secondary minerals such as clays. Feldspar in granite reacts with hydrogen in water to produce kaolin (china clay).

Answer 23

Grow into cracks or joints in rocks & exert outward pressure. This operates in a similar way & with similar effects to freeze-thaw. When trees topple, their roots can also exert leverage on rock & soil, bringing them to the surface & exposing them to further weathering. Burrowing animals may have a similar effect. This may be particularly significant on cliff tops & cliff faces.

Answer 24

Produced during decomposition of plant & animal litter cause soil water to become more acidic and react with some minerals in a process called chelation. Blue-green algae can have a weathering effect, producing a shiny film of iron & manganese oxides on rocks. On shore platforms, molluscs may secrete acids which produce small surface hollows in the rock.

Answer 25

Water enters cracks/joints & expands by nearly 10% when it freezes. In confined spaces this exerts pressure on the rock causing it to split or pieces to break off, even in very resistant rocks.

Answer 26

Water overlying rocks are removed by weathering & erosion, the underlying rock expands & fractures parallel to the surface. This is significant in the exposure of sub-surface rocks such as granite & is also known as dilatation. The parallel fractures are sometimes called pseudo-bedding planes.

Answer 27

Rocks expand when heated & contract when cooled. If they are subjected to frequent cycles of temperature change then the outer layers may crack & flake off. This is also known as insolation weathering, although experiments have cast doubts on its effectiveness unless water is present.

Answer 28

Solutions of salt can seep into the pore spaces in porous rocks. Here the salts precipitate, forming crystals. The growth of these crystals creates stress in the rock causing it to disintegrate. Sodium sulphate & sodium carbonate are particularly effective, expanding by about 300% in areas of temperatures fluctuating around 26-28⁰C.

Answer 29

def - The slow downward progression of rock and soil down a low grade slope; it can also refer to slow deformation of such materials as a result of prolonged pressure and stress. most prone geology types - Rocks and soil areas psd - Carribean nation of Trinidad; in 2012 expensive road repair plans (61 million dollars) were announced. The area surrounding the road which needed repairs suffered from soil creep. The movement of the soil caused instability and truggered more mass waste such as debris flows. Soil creep usually hinders us financially.

Answer 30

def - the gradual movement of wet soil or other material down a slope, especially where frozen subsoil acts as a barrier to the percolation of water. Most prone geology types - hillsides that have lobe-shaped slumps in them psd - Gros Morne, Newfoundland

Answer 31

def - a fluid or hardened stream or avalanche of mud. Most prone geology types - Mudflows occur on steep slopes where vegetation is not sufficient to prevent rapid erosion but can occur on gentle slopes if other conditions are met. psd - On June 15, 1991, Mount Pinatubo in the Philippines exploded in the second largest volcanic eruption on Earth this century. Within hours, heavy rains began to wash this material down into the surrounding lowlands in giant, fast-moving mudflows called lahars.

Answer 32

def - A slump is a type of mass wasting that results in the sliding of coherent rock material along a curved surface. A slump is sometimes referred to as a rotational slide because a portion or block of the slope 'slides' down as it 'rotates' around an axis parallel to the slope. Most prone geology types - Coastal cliffs are subject to slumping when wave action undercuts lower layers. psd - The slump that destroyed Thistle, Utah, by creating an earthen dam that flooded the area. By the 16th of April the tracks were buried and the town was ordered evacuated. The ground continued to move and the 17th they tried to keep the river from being blocked, and failed. This rail route is one of the busiest in the nation, and the rail was rerouted through Wyoming.

Answer 33

def - an avalanche of loose rocks. Most prone geology types - cliff faces psd - Yoseite rockfall (national park california) On July 5, two rock climbers found a new expanse of blank rock. Sometime in the previous days, a rock slab totaling some 1,800 cubic meters (about 5,200 tons) parted from the cliff in a classic case of exfoliation.

Answer 34

def - he draining away of water (or substances carried in it) from the surface of an area of land, a building or structure, etc. Most prone geology types - valleys

Answer 35

Solution - minerals are dissolved in the water and carried along in solution. Suspension - fine light material is carried along in the water. Saltation - small pebbles and stones are bounced along the river bed. Traction - large boulders and rocks are rolled along the river bed. Longshore drift - occurs when waves approach the coast at and angle due to the direction of the prevailing wind. Then swash carries particles diagonally up the beach. Backwash then moves sediment perpendicularly back down the beach. This can increase rates of attrition

Answer 36

- this is the dumping of sediment by the sea. - It occurs when the waves lose energy,a decrease in velocity &/or volume of water - often when they enter a sheltered part of the coastline like a bay, estuary etc, away from winds & waves - The rate of sediment accumulation exceeds the rate of removal - When waves slow immediately after breaking - Top of swash, where water is no longer moving - Backwash, when water percolates into the beach material

Answer 37

Erosion - wind is able to pick up sand particles & move them be deflation. at speeds of 40km/hour, sand grains are moved by surface rolling(surface creep) & saltation. Erosive force increases exponentially with increases in wind velocity. Eg, velocity increase from 2 to 4 m per second causes an 8fold increase in erosive capacity! Dry sand is much easier for wind to pick up than wet, moisture increase cohesion in particules. Transportation - Moving air is able to transport material using the same mechanisms as water. Once particles have been entrained, they can be carried at velocities as low as 20km/hour. Saltating grains = 0.15-0.25mm in diameter, while those 0.26-2mm which are to heavy = surface creep. 0.05-0.14mm can be carried in suspension. Deposition - When when speed falls, usually as a result of surface friction. Occurs inland, where friction from vegetation & surface irregularities is much greater than on the open sea.

Answer 38

``` Flows of energy Flows of material Weathering Mass Movement Wave action Fluvial & aeolian erosion Transportation Deposition ```

Answer 39

Destructive waves break repeatedly Relatively steep sloping coastlines Undercutting can occur between HTWM & LTWM Wave cut notch Weakens strata above Pulls down & collapses Leaving a steep profile & cliff Constant removal of sediment at the base Wave action ensures that the cliff profile remains relatively steep. Cliff retreats inland parallel to the coast Geology, Lithology & Structure: Horizontally bedded & landward dipping strata = supports cliffs with steep, near vertical profile. Strata inclining seawards = follows the same angle of the dipping strata.

Answer 40

As the sequence of undercutting, collapse & retreat continues the cliff becomes higher. At its base a gently sloping shore platform is cut into the solid rock: Abrasion = rock debris Wave action Accumulation of large boulders Platform will eventually be so wide = shallow water & small waves even at HT Friction slows waves = breaks waves away from cliff = undercutting reduced (max W = 500m) Solution, freeze-thaw, Salt crystallisation Algae accelerates weathering Slope seawards (0°-3°) Sometimes ramp at HT & small cliff at LT (tidal range less than 4m)

Answer 41

Algae, lichens, bacteria and mosses often grow on rock surfaces, especially in humid regions. They produce weak acids, which convert some of the minerals to clay. Algae growth can weaken many rock types and make it more open to weathering.

Answer 42

If rock outcrops lie perpendicular to the coastlines = weaker rock = bays BUT More resistant rock = headlands = discordant. Width of bays determined by width of bands or rock Differential rates of erosion Rocks lying parallel to the coastlines = concordant. More resistant rock lies seaward side = protects weaker rocks inland = straight & even coastlines BUT small bays & coves can still be created at points of weakness (fault lines)

Answer 43

An example of refraction is when waves approach a straight shoreline at an angle. The part of the wave crest closer to shore is in shallower water and moving slower than the part away from the shore in deeper water. The wave crest in deeper water catches up so that the wave crest tends to become parallel to the shore.

Answer 44

At right angles. Orthogonals plotted through the crests of waves in plan illustrate the process of *wave refraction.

Answer 45

Geos are narrow, steep-sided inlets. Even on coastlines with resistant geology, there may be lines of weakness such as joints& faults = eroded more rapidly = Hydraulic Action weakening rock strata. Eg, Huntsman’s leap in Pembrokeshire 35m deep & eroded along a large joint in the carboniferous limestone. Initially forms as tunnel-like caves running right-angles to the cliff line = may result in roof collapse creating a GEO.

Answer 46

If part of the roof of a tunnel-like cave collapses along a master joint it may form a vertical shaft that reaches the cliff top. This is a blowhole Storm conditions & large waves may force spray out of the blowhole Plumes of white aerated water Eg, Trevone, Cornwall, where they are known as zawns 25m deep blowhole! They may also be associated with old tin mining shafts!

Answer 47

Wave refraction Energy if concentrated on the sides of headlands Points of weakness are exploited by erosional processes Small cave may develop between HTWM & LTWM Cave enlarges to extend through to the other side of the headland. An arch is formed Aided by weathering the arch collapses Isolated stack from gravitational pull

Answer 48

Most common landform! Accumulation of material deposited between LT and H storm tides. Sand produces beaches with a gentle gradient (usually less than 5°). Its small particle size becomes compact when wet, allowing little percolation during backwash. As little energy is lost to friction, & little volume is lost to percolation, material is carried back down the beach rather than being left at the top! Shingle produces steeper beaches. Swash is stronger = net movement of shingle onshore. Shingle may make up the upper part of the beach where rapid percolation due to lrager air spaces = little backwash.

Answer 49

Storm waves hurl pebbles & cobbles to the back of the beach = storm beach or storm ridge. Berms = smaller ridges = mean high tide mark = deposition at the top of the swash. Dynamic & profiles change over times (wind strength & wave energy) Respond by creating equilibrium profiles, balance between E&D Cusps = small, semi-circular depressions temporary features formed by collection of waves reaching the same point & when swash & backwash have similar strength the sides of the cusp channel incoming swash into the centre of the depression = strong backwash drags material down the beach from the centre of the cusp = enlarging the depression. Further down the beach ripples may develop in the sand due to the orbital movement of water in waves

Answer 50

High energy = destructive waves = removal of sediment offshore = flatter beach profile = shallower water = more friction = reduction in wave energy. Low energy = constructive waves = transfer sediment in the opposite direction = stepper profiles = deeper water = less friction = increase wave energy.

Answer 51

Attached to the land at one end & extend across a bay, estuary or indentation in a coastline. Formed by L.S.D in one dominant direction Storms build up material & larger material = substantial & permanent. End may become recurved as a result of wave refraction around the end of the spit & possibly the presence of a secondary wind/wave direction. Over time spits continue to grow = number of recurves or hooks ends my develop. Spits across estuaries lengths may be limited by the river's current Sheltered area = behind spits = wave energy reduced = deposition = silt & mud build up = salt-tolerant vegetation colonise = salt marsh

Answer 52

When spits grow across a cove/bay until it joins onto land at the other side. Forms a lagoon of brackish water on the landward side

Answer 53

Are beaches that connect the mainland to an offshore island Often formed from spits that have continued to grow seawards until they reach & join an island Chesil Beach, Weymouth, Dorset: 30km shingle beach However the onshore movement of sediments is now thought to be the more likely cause, with it reaching its present position some 6,000 years ago. At its eastern end at Portland , the ridge of shingle = 13m high & composed of flinty pebbles At the western end, near Burton Bradstock, the ridge is only 7m high & composed of smaller pea-sized shingle If LSD responsable = it would be expected that the sediment further east = smaller! Onshore migration of shingle originally produced a uniform distribution of sediment sizes. subsequently , strong longshore currents from the southwest have moved sediment s of all sizes eastwards while weaker longshore currents from the east have only been able to return the smaller particles westwards.

Answer 54

Low marsh , on seawards side = high salinity, turbid water & long periods of submergence. Few plants can survive the conditions = specie diversity is poor. Low-energy environments such as estuaries & on landward side of spits. The Uk = 45,500ha of salt marsh! (mainly on eastern & northwest England) Vegetated areas of deposited silts & clays Twice daily inundation & exposure as tides rise & fall. Salt tolerant plants like cordgrass then colonise (move into) the area. Cordgrass is called a pioneer species. Others include eelgrass & spartina. Traps sediments, helping to increase the height of the marsh. Over time more species move into the area, building up the vegetation. This is called succession. Roots stabilise sediment. The higher the marsh the shorter the inundation = less saline conditions. Further inland = less harsh, less salinity, turbidity & submergence periods are lower. = variety of species can survive, eg, sea aster, reeds & rushes. Shallow gradient which slopes seawards A low cliff sometimes separates the salt marsh from the unvegetated mudflats on the seaward side. Deposition rates are quite high as at HTWM = low energy = slack water 2-3hrs. Extensive networks of small, steep-sided channels, or creeks drain the marsh at LT & provides routes for water to enter the marsh as the tide rises.

Answer 55

Are large areas of sediment found at the mouths of many rivers. Deltaic sediments are deposited by rivers & tidal currents. When rivers & tidal currents deposit faster than waves & tides can remove it! Most common creations: Large river load Broad continental shelf margin at the river's mouth = platform for sediment accumulation Low-energy environments exist Tidal ranges are low Three distinctive structural components: Upper delta plain - furthest inland, beyond the reach of tides, composed entirely by river load. Lower delta plain - inter-tidal range, regularly submerged & both river & marine sediment. Submerged delta plain - lies below mean LTWM = marine sediments mainly & seaward growth of the delta Criss-crossed branching networks of distributaries = Overloaded with sediment, deposition in the channel forms bars = channel splits into 2 = reduced energy = more deposition & divides further = levѐes on banks = when breached = lobes of deposition called crevasse splays are left.

Answer 56

There are many different types of delta but three of the most common types are: Cuspate: A pointed extension to the coastline occurs when sediment accumulates but this is shaped by regular, gentle currents from opposite directions. Arcuate: Sufficient sediment supply is available for the delta to grow seawards but wave action s strong enough to smooth & trim its leading edge. Bird’s Foot: Distributaries build out from the coast in a branching pattern, with river sediment supply exceeding the rates of removal by waves & currents.

Answer 57

About 130,000 years ago, during the Tyrrhenian inter-glacial period, global mean annual temperatures were almost 3°C higher than today & sea level was about 20m above today's position! Temperatures fell during the onset of the Riss glacial period, reaching a minimum about 7°C lower than today about 108,000 years ago. This led to temperature decrease, less water was returned to the ocean store & sea levels dropped by over 100m, making them about 83m lower than the present day.

Answer 58

Changes in the volume of water in the global ocean store are known as EUSTATIC changes. These changes are influenced by variations in mean global temperatures, affecting both the amount of water in the ocean store & its density However, it should be appreciated that sea level change is relative as it is also affected by changes in land level. These changes are known as ISOSTATIC. There are a number of physical factors that can affect changes in global temperature & volume of water in the oceans: Variations in the earth's orbit around the sun, typically every 400,000 years Variations in the amount of energy produced by the sun, with a solar maximum every 11yrs or so Changes in the composition of the atmosphere due to major volcanic eruptions which reduce incident solar radiation Variations in the tilt of the earth's axis, occurring every 41,000yrs. A decrease in global temperature leads to more precipitation being in the form of snow. Eventually snow turns to ice & so water is stored on the land in SOLID form rather than being returned to the ocean store as LIQUID. The result is the reductio in the volume of water in the ocean store & a worldwide fall in sea level As temperatures fall = water molecules contract, leading to an increased density & a reduced volume. It is estimated that a 1°C fall in the mean global temperature = sea levels to fall approximately 2m.

Answer 59

Are areas of former shore platforms that are left at a higher level than the present SL. Found a distance inland from the present coastline Behind the beach along emergent coastlines it is not uncommon to find abandoned cliffs with wave-cut notches, caves & even arches & stacks! On the southern tip of the Isle of Portland near Weymouth in Dorset = distinct raised beach at a height of about 15m above the present day SL. Around 125,000 years ago during the Tyrrhenian inter-glacial period when SL were much higher than today’s. The Portland Limestone = eroded by hydraulic wave action & exploitation through the bedding plane weaknesses. Erosion rates at that time are estimated to have been as much as 1m/yr.Other raised beaches at Portland are thought to date to about 210,000years ago! After their emergence, these landforms were no longer affected by wave processes. Continue to be affected by weathering & mass movement Isle of Portland = 1-1.5m layer of frost-shattered limestone debris deposited when the are experienced periglacial conditions during the last glacial period The cliff face itself was gradually degraded by frost weathering processes = rock fall Evidence of other periglacial processes = cryoturbation = contortions in fragmented limestone = freezing/thawing of the permafrost in the subsoil during the late pleistocene period ( the final glacial phase) In post-glacial period = warmer & wetter conditions = development of vegetation cover on many exposures,, often making them more difficult to recognise. Further warming = continued degradation = chemical weathering? Carbonation of limestone cliffs & platforms. Biological on raised beaches = colonisation from marine organisms such as limpets & whelks. Temp increase rapidly = the associated sea level rise could lead to these emergent landforms again being found much closer to, or even at, the coastline They would be subject to wave processes once more. Temp rise = water molecules expand = increase volume. A 1°C rise in mean global temp = sea level rise of approx 2m! About 25,000 years ago at the end of the Wurm glacial period = temp were about 9°C lower than today & sea level was about 90m lower than the present. Since then significant rise = FLANDRIAN TRANSGRESSION

Answer 60

SL can fall in a series of stages = Marine erosion = marine terraces. Appears as steps in the landscape - each one represents a period of stable temperatures & SL during wave action. Wave action needs sufficient time to create a flat, eroded step/terrace. Although associated with a decrease in SL due to cooling climate = can be related to rising land levels (Isostatic Change).

Answer 61

Submerged river valleys formed as sea level rises. The lowest part of the river course & the floodplains alongside the river may be completely drowned. BUT the higher land forming the tops of the valley sides & the middle & upper part of the river’s course remains exposed. In cross section rias = relatively shallow water becoming increasingly deep towards the centre. Exposed valley sides = gentle sloping Long section = smooth profile & water of uniform depth. Plan view = winding, reflecting the original route of the river & its valley formed by fluvial erosion within the channel & sub-aerial processes. Can be found on south coasts of Devon & Cornwall - Salcombe, Kingsbridge & Fowey Formed during post-glacial sea level rise of the Flandrian Transgression. Alluvial deposits in buried channels - eroded by rivers that flowed down the lower SLs of Pleistocene glacial periods. During interglacial periods = sea level rose = further deposition = less surplus energy for erosion.= significant infilling of these earlier

Answer 62

Are submerged glacial valleys = steep (almost cliff-like) valley sides & water is uniformly deep - often reaching 1000m! Sogne Fjord in Norway = 200km long Although those in Scotland are less well developed as the ice was not as thick during the glacial period. U-Shaped cross section reflects the original shape of the glacial valley itself - they consist of a glacial rock basin with a shallower section a the end known as the threshold This results from lower rates of erosion at the seaward end of the valley where the ice thinned in warmer conditions. (eg, Milford Sound, New Zealand) They also tend to have much straighter planforms than rias as the glacier would have truncated any interlocking spurs present. Due to the depth of water that occupied fjords during the Flandrian Transgression, marine erosion rates remained high and in some cases the fjords were further deepened. In others, such as those on the west coast of South Island, New Zealand, there has been some infilling with sediments. Deposited by meltwater from the glaciers of the Southern Alps, the volume of sediment has increased significantly in recent decades as glaciers have receded.

Answer 63

def - When SL falls as the new volume of land-based ice grows, large areas of ‘new’ land emerge from the sea. Sediment accumulates on this surface,deposited by rivers, meltwater streams & low-energy waves. As sea levels rose at the end of the last glacial period, wave action pushed these sediments onshore = beached at the base of former cliff lines; elsewhere they may form tombolas & bars. Flandrian Transgression = Chesil Beach. Sediment carried into the English Channel by meltwater during the Wurm glacial accumulated in locations such as Lyme Bay. SL rose = sediment carried NE by southwesterly prevailing winds & the resultant waves. Moved a total of about 50km until it became attached to the Isle of Portland at one endand & the mainland near Abbotsbury at the other. Beach contains as estimated 100million tonnes of shingle, varying in size from 1-2cm pea-sized material to 5-7cm pebbles. It was previously thought this tombola was formed by the extension of a spit towards the Isle but the lack of recurves & the complex grading of pebbles suggest that it was not formed by LSD alone.

Answer 64

Both rias & fjords may be modified by wave processes acting on their sides at the present-day sea level. Valley sides by sub-aerial weathering in today's climatic conditions or in any different climatic conditions of the future = reduction in steepness of valley sides of fjords SL predictions of 0.6m in the next 100yrs, water depth in rias & fjords will increase = marine erosion increases due to stormier conditions & larger waves Shingle beaches = composed of unconsolidated material = vulnerable to modification. The tombolo at Chesil Beach has been affected by present-day LSD SL irse = shingle may well be moved even further to the NE (currently at a rate of 17cm/yr) & a breach of the tombolo is highly likely in future storm events. Recent storms = waves over-topping the beach = 2009a 1m=sized particle of shelly clay were eroded from in front of the beach & washed up onto it at West Bexington in a winter storm.

Answer 65

The Holderness Coast in North Yorkshire is the fastest eroding coastline in Europe. The current rate of erosion along the coast is 2 metres a year.

Answer 66

The average annual rate of erosion is around 2 metres per year. 4km strip of land lost since Roman times – along with its settlements

Answer 67

The Holderness Coastline is made up of soft boulder clays (or till) left after the retreat of the Devensian ice sheets about 12 000 years ago. To look at the cliffs are a mass of brown clay containing pieces of rock (erratics) brought here by the glaciers. These soft, recent deposits sit on a platform of chalk which slopes away gently to the east.

Answer 68

Attack from above: The soft Boulder Clay cliffs become saturated with rain water. Chemical weathering in the summer and freeze thaw in the winter weaken the cliffs. The cliffs fail and mass movement occurs either as a landslide or as a mudflow Attack from below: Large destructive waves from the North East erode the base of the cliffs Hydraulic action and abrasion create wave cut notches that undercut the cliffs. The cliffs retreat and sediment is removed by longshore drift to the south

Answer 69

1. Hard Engineering - Wooden Groynes Coastal Resorts need to protect the beach! Used to trap sediment carried by longshore drift. 2. Soft Engineering – Beach Nourishment Added sediment to the beach by dredging or pumping from offshore straight onto beach. Mappleton: Hard Engineering - Rock Groynes In place to reduce the 4m of cliff erosion per year! Also cliff face was re-graded to make it more stable. Hornsea Groynes = Starved Mappleton = Cliff Erosion = Longshore Drift

Answer 70

The village of Mappleton, perched on the cliff top, has approximately 50 properties. As the cliff is eroded away, the village is under threat. Protecting Mappleton: This is Mapleton's shoreline management plan or SMP. It was very controversial. In 1991 a shoreline management plan (SMP) costing £2 million was introduced. This involved two types of hard engineering: placing rock armour along the base of the cliff and building two rock groynes

Answer 71

In 1991 two rock groynes and a rock revetment made from huge blocks of Scandinavian rock were built. As a result a substantial beach accumulated updrift of the groynes stopping erosion (picture 1 below). However, further south the rate of erosion has increased significantly (picture 2 below). This is because material which is being carried south is not being replaced (terminal groyne syndrome). Therefore there is no beach to protect the cliffs. Waves are able to break directly onto the soft boulder clay cliffs. Hydraulic action and abrasion leads to rapid cliff retreat.

Answer 72

Mappleton’s groyne has cut off sand to Aldbrough – a small hamlet 1km south of Mappleton. The Mars family live here. They are set to lose everything. Watch the clip and fill in the following table.

Answer 73

Hard Engineering – Sea Walls Tourist resort needed protecting. Holding the line strategy to save employment and property price. Two types of sea wall Straight Wall Recurved wall 2. Hard Engineering – Rock Armour/rip-rap Placed at base of wall. Boulders designed to dissipate wave energy, preventing scouring. Sea Wall & Rock Armour = Very Expensive = Dissipates wave energy = reducing erosion

Answer 74

Hard Engineering – Revetments Rock revetment has been built to protect gas terminal Placed like wall to absorb wave energy Expensive but long lasting.

Answer 75

Agriculture is the traditional employment of the area and there is a substantial area of horticultural development on the flat fertile land in the south-west. Animal husbandry, particularly pig rearing, is a major part of the agricultural scene. In 2001 agriculture employed 4.5% of the working population. Industrial activity ranges from small workshop units in Hornsea and Withernsea to the Easington and Dimlington gas terminals on the east coast. These terminals process gas from the North Sea gas fields. The British Petroleum chemical works at Saltend uses condensates from the gas refining process and is a major employer in the area. Tourism makes a significant contribution to the economy of Hornsea and Withernsea with Hornsea Pottery and Freeport attracting around a million visitors each year

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