Coasts

Question 1

CASE STUDY: Studland management

Answer 1

Sand dune management: reinforced pathways with roped off dune areas- trampling causes loose sand which wind will blow away, stopping blowouts but was reducing biodiversity- sand lizards need compact soil to rest and lay eggs
Managed retreat: middle beach cafe and beach huts moved back, decided by national trust, direction of lsd means little sediment reaches this part of the beach, protection of this infrastructure as national trust did not want to rebuild hard defences as not sustainable but community did- social conflict, also feeds the spit which is important for poole harbour and hard management like groynes would stop this

Question 2

CASE STUDY: Barton on sea management

Answer 2

cliffs with sand on top and clay underneath so when wet landslides occur- rotational slumping, starved of sediment due to long groyne so beach cannot be built up leading to further erosion and cliff retreat, people also keep building on cliff making them weaker leading to more erosion, several chines also add water into the cliffs making them even weaker

Question 3

Open system

Answer 3

energy and matter can be transferred to neighbouring systems as an input and transferred out as an output
inputs- kinetic energy from wind and waves, potential from material from deposition, weathering and mass movement
outputs-marine and wind erosion and evaporation
processes- consist of stores like beach sediment accumulation and movement like lsd

Question 4

Feedback system

Answer 4

if inputs and outputs are equal then system will be in equilibrium- rate of sediment added same as rate of sediment being removed
when disturbed the system will self-regulate and changes form to restore it- dynamic equilibrium as own response being produced- negative feedback

Question 5

Sediment cell

Answer 5

stretch of coastline and nearshore area where movement of sediment is contained, primarily a closed system so no sediment is added or removed. The boundaries of a sediment cell is determined by the topography and shape of coastline- large physical features like Lands end are a natural barrier that prevent sediment transfer
can never be fully closed due to variation in wind direction, currents and natural events like storms

Question 6

Wind

Answer 6

frictional drag of winds moving across the ocean surface create wave energy which is a source of energy for erosion and transport. The higher the wind speed and longer the fetch, the larger the waves and more energy. Onshore winds are effective at driving waves towards coast, if winds blow at oblique angle so will waves and so lsd created
can carry out erosion, transportation and deposition so contribute to shape of land

Question 7

Waves

Answer 7

possess potential energy due to position above the wave trough and kinetic caused by motion of water within wave
Breaking waves- when waves go to shallow water they change and the deepest circling water molecule comes in contact with sea floor creating friction which greatly changes the speed, direction and shape of the waves- slow down as they drag on bottom, wavelength decreases and deepest part of wave slows down more than top of waves, wave steepens as crest goes ahead of base and then breaks against the shore, causing signif forward movement of water and energy
after breaking, water moves forward as swash, driven by transfer of energy occurring when wave breaks, speed of this will decrease due to friction and uphill slope, when has no more energy it will come back down as backwash and energy for this is due to gravity and always occurs perpendicular to coast down steepest slope angle

Question 8

Constructive and destructive waves

Answer 8

constructive- low height, long wavelength, low frequency, strong swash, due to long wavelength, backwash returns to sea before next wave breaks so next swash movement uninterrupted and retains its energy, swash energy exceeds backwash energy
destructive- high height, shorter wavelength, high frequency, break by plunging down so little forward transfer of energy to move water up beach, friction slows swash and doesnt travel far before moving back down, swash of next wave slowed by friction of meeting previous backwash
high energy waves often in winter months and remove material from top of a beach and transport it to offshore zone, reducing beach gradient. low energy waves in summer build up beach and steepen it

Question 9

Tides

Answer 9

moon pulls water towards it creating high tide and there is a compensatory bulge on opposite sides of the earth. at locations between two bulges there will be low tide, as moon orbits earth the high tides will follow it. highest tides when earth sun and moon are aligned and gravitational pull is at its strongest- happens twice each lunar month resulting in spring tides with high tidal range. twice a month moon and sun at right angles to each other and gp is weakest producing neap tides with a low range
signif in development of landscapes, in enclosed seas like the med the tidal ranges are low and so wave action is restricted to narrow area of land. influences where wave action occurs

Question 10

Lithology

Answer 10

physical and chemical composition of rocks, clay has weak lithology with little resistance to erosion bc the bonds between the particles that make up the rock are weak

Question 11

Structure of rocks

Answer 11

properties of individual rock types like jointing, bedding and faulting as well as its permeability, porous rocks like chalk can absorb and store water bc of tiny air spaces, carboniferous limestone also permeable but bc of its many joints
rocks that are parallel to coast are concordant, rocks at right angle to coast are discordant

Question 12

Currents

Answer 12

rip currents- caused by tidal motion or waves breaking at right angles to shore, cellular circulation generated by differing wave heights parallel to shore, water from top of breaking waves w large height travels further up the shore and returns through area where lower height waves broke, once formed they modify shore profile by creating cusps which help perpetuate the rip current, channelling flow through a narrow neck
ocean currents- large scale, generated by earths rotation and convection and set in motion by movements of wind across water surface. warm ocean currents transfer heat energy from low latitudes towards the poles and affect western-facing coastal areas where driven by onshore winds. cold ocean currents move cold water from polar regions towards equator and driven by offshore winds so less affect on coastal landscapes

Question 13

Source of sediment- Terrestrial

Answer 13

rivers major sediment input to sediment budget, esp for coasts w steep gradient where rivers directly deposit sediment to coast, can be intermittent mainly occurring during floods
origin of sediment is erosion of inland areas by water wind and ice and sub aerial processes of weathering and mass movement
wave erosion also major source, cliff erosion increased by rising sea levels and storm surge events
lsd supplies sediment by moving it along coast

Question 14

Source of sediment- Offshore

Answer 14

constructive waves bring sediment to shore from offshore locations and deposit it, tides and currents do same, wind blows sediment from sand bars, dunes and beaches elsewhere on the coast- fine sand as does not have energy to transport large particles

Question 15

Source of sediment- Human

Answer 15

when budget is in deficit, beach nourishment maintains equilibrium. sediment brought in and dumped then spread out, sand and water can also be pumped onshore by pipeline from offshore sources

Question 16

Physical weathering

Answer 16

freeze thaw- water enters joints and expands when frozen, exerts pressure on rocks and causes it to split
thermal expansion- rocks expand when heated and contact when cooled, if subject to frequent temp changes then outer layers crack and flake off
salt crystallisation- salt solutions seep into pores in porous rocks and the salts precipitate, form crystals which creates stress in the rocks causing it to disintergrate

Question 17

Chemical weathering

Answer 17

occurs better in tropical regions- vant hoffs law states that a 10 degrees increase in temp leads to a 2.5x increase in rate of chemical reaction
carbonation- rainwater combines w dissolved co2 from atmos to produce weak carbonic acid, reacts w calcium carbonate in rocks like limestone to produce calcium bicarbonate which is soluble
oxidation- minerals in rocks react w oxygen in air or water like iron, becomes soluble in acidic conditions and original structure destroyed

Question 18

Mass movement

Answer 18

forces acting on slope material exceed forces trying to keep material on slope
rock fall- on cliffs of 40 degrees or more, rocks may detach from slope through physical weathering and fall to foot of cliff bc of gravity
slides- can be linear w movement along a straight line slip plane like a fault between layers of rock or rotational w movement along a curved slip plane. rotational slides occur due to undercutting at base of cliff so no support for materials above, common in weak rocks like clay which are also heavier when wet

Question 19

Erosion

Answer 19

abrasion- waves w rocks against coast
attrition- rocks collide and become smoother and rounder
hydraulic action- waves break against cliff face and air and water trapped in cracks become compressed, wave recedes and pressure released and the air and water suddenly expand and crack is widened

Question 20

Transportation

Answer 20

solution- dissolved minerals in mass of moving water, invisible and will remain until water evaporates
suspension- small particles carried by currents
saltation- irregular movements of material too heavy to be suspended
traction- largest particles pushed along sea floor by force of the flow
lsd- waves approach at angle due to direction of dominant wind, when waves broken the swash carries particles diagonally up the beach, gravity and backwash pull them back down perpendicularly

Question 21

Deposition

Answer 21

material deposited due to loss of energy
large heavy material at back of beach due to strong swash but smaller at front due to weak backwash

Question 22

Fluvial processes

Answer 22

fluvial erosion in upper catchment is main source of rivers sediment load
deposition- as river enters sea there is high reduction in velocity as flowing water enters static sea water, energy reduced and so most of rivers sediment load is deposited, energy reduction progressive so deposition is sequential w large deposited first and finest going out to sea. meeting of fresh and salt water causes flocculation of clay particles which clump together bc of electrical charge and become heavier and sink to sea bedf

Question 23

Aeolian processes

Answer 23

erosion- wind picks up sand particles and moved them by deflation. dry sand easier to pick up as they are not stuck together, attrition effective in wind as can be carried a further distance and not protected by film of water, limited effect on cliffs as can only carry v light material
deposition- material deposited when wind speed falls due to surface friction

Question 24

Bays and headlands

Answer 24

form adjacent to each other due to bands of rock of differing resistance, if the rock outcrop lies perpendicular to coastline the weaker rocks are eroded more rapidly to form bays and the resistant rock stays between bays to form headlands. width of bays determined by width of the band of weaker rock
when waves approach an irregularly shaped coastline, wave refraction happens and they develop a configuration increasingly parallel to the coast . wave is slowed by friction in shallower water off the headland while the part of the wave crest in the deeper water approaching the bay moves faster so the wave bends around the headland, so wave energy and erosion is focused on the headland, in bays the energy is dissipated leading to deposition, as waves break onto side of headland at an angle there is longshore movement of eroded material into bays

Question 25

Geos and blowholes

Answer 25

geos- narrow steep-sided inlets, weak points on coastline eroded more rapidly by wave action, esp hydraulic action which weakens rock strata- huntsmans leap in pembrokeshire which is 35m deep along a large joint in carboniferous limestone. sometimes initially form as tunnel like caves at right angles to cliff line which may suffer roof collapse due to erosion. if part of the roof of a tunnel like cave collapses along master joint it may form vertical shaft that reaches the cliff top- blowhole. in storms large waves may force spray out of it

Question 26

Caves, arches, stacks and stumps

Answer 26

due to wave refraction, energy is concentrated on sides of headland, any joints or faults are exploited by erosion and small cave developed on one side or maybe both, wave attack is concentrated between high and low tide and it is here that caves form, if cave enlarges it may extend all the way through and form and arch, erosion widens arch and weakens support, aided by weathering processes the arch may collapse and leave a stack, erosion at base of stack may cause further collapse and leave a stump that may only be visible at low tide

Question 27

Beaches

Answer 27

material comes from cliff erosion, offshore and rivers sand makes beaches w gentle gradient, less than 5 degrees, bc the small particle size is compact when wet allowing little percolation during backwash, little energy lost to friction and little volume lost so material is carried back down beach rather than being left at top leading to gentler gradient and development of ridges. shingle makes steeper beach bc swash is stronger than backwash so net movement of shingle onshore, makes up upper part of beach due to high percolation so little backwash and more material at top of beach beaches respond to energy changes in wind and waves by developing an equilibrium profile with a balance between erosion and deposition. high energy destructive waves remove sediment offshore and create flatter beach profiles resulting in shallower water, more friction and less wave energy, low energy constructive waves transfer sediment creating steeper profiles resulting in deeper water, less friction and more wave energy

Question 28

Storm ridges and berms

Answer 28

ridge- storm waves hurl pebbles and cobbles to the back of the beach berms- smaller ridges that develop at the high tide mark due to deposition at the top of the swash

Question 29

Cusps

Answer 29

small semi-circular depressions, temporary feature formed by a collection of waves reaching the same point and when swash and backwash are of similar strength, sides of the cusp channel incoming swash to the centre of depression which produces strong backwash and drags material down the beach from the centre of cusp and enlarges the depression

Question 30

Spits

Answer 30

long narrow beaches that are attached to land at one end and extend across estuary or bay, generally formed by lsd occurring in one dominant direction, carrying beach material to end of beach and beyond into open water, storms build them up with larger material making them more substantial and permanent, end of spit often recurved due to wave refraction around the end of the spit and bc of secondary wave/wind direction, grow over time, if formed over estuary length may be limited due to river current in sheltered area behind spit deposition occurs as wave energy is reduced, silt and mud deposited build up and salt tolerant vegetation will colonise leading to a salt marsh studland

Question 31

Onshore bars

Answer 31

develop if a spit grows across bay and joins up with the land on the other side, forms a lagoon of brackish water Slapton sands- no dominant direction of lsd and no pattern of distribution of sediment sized, so formed by onshore movement of sediment during the post-glacial sea level rise

Question 32

Tombolos

Answer 32

beaches that connect the mainland to offshore island, formed from spits that grow seawards until they reach an island Chesil beach- 30km long, onshore movement of sediment is the cause and reached its present position 6000 yrs ago, at east end the ridge of shingle is 13m high and composed of flinty pebbles, at western end it is 7m high and composed of smaller shingle. if lsd was the cause then sediment should be smaller further east so more likely to be that the onshore migration of shingle originally produced a uniform distribution of sediment sizes, strong longshore currents from SW moved all sediment sizes while weaker currents from east only moved smaller particles to west

Question 33

Salt marshes

Answer 33

low energy features like estuaries, vegetated areas of deposited silts and clays, subject to inundation and exposure twice daily as tides rise and fall, salt tolerant plant species help trap sediment gradually increasing the height of the marsh, stems and leaves act as baffles and trap sediment while roots stabilise it high marsh- shorter period od daily submergence and less saline low marsh- seaward side, high salinity, turbid water and long periods of submergence poor species diversity as few plants can survive the conditions, greater variety inland as conditions not so harsh shallow gradient sloping seawards, higher parts inundated often but deposition still high as at high water mark low energy water can be present for 3 hours, small creeks drain the marsh at low tide and allows water to enter marsh as tide rises, shallow depressions often found between the creeks which trap water when tide falls and these areas of salt water called saltpans have no vegetation development depends on rate of accumulation of sediment, deposition of fine sediment occurs as river loses energy when they slow upon entering sea, flocculation also helps develop as as the clay particles are attracted to each other and are unable to be carried in river flow

Question 34

Deltas

Answer 34

large areas of sediment found at river mouths, deltaic sediments deposited by rivers and tidal currents anf form when rivers and tidal currents deposit sediment at a rate faster than waves and tides can remove it form where: rivers entering sea are carrying large sediment loads, broad continental shelf margin is at river mouth providing platform for accumulation, low energy environments exist in coastal area, tidal ranges are low structure: upper delta plain- furthest inland, beyond reach of tides and composed of river deposits, lower delta plain- intertidal zone, regularly submerged and composed of river and marine deposits, submerged delta plain- lies below mean low water mark and is composed of marine sediments criss-crossed by distributaries, overloaded with sediment so deposition in channel forms two bars causing channel to split in two, two channels w low energy levels so more deposition and more dividing, channels may be lined w levees on banks but in times of flood then they are breaches and depositions of lobes of sediment take place in low lying areas between levees called crevasse splays

Question 35

Types of delta

Answer 35

cuspate- pointed extension to coastline occurs when sediment accumulates and shaped by regular gentle currents from opposite directions arcuate- sufficient sediment for delta to grow seawards but wave action strong to smooth and trim leading edge birds foot- distributaries build out from coast in branching pattern, river supply exceeds rate of removal by waves and currents

Question 36

Eustatic changes

Answer 36

changes in the volume of water in the global ocean store, changes influenced by variations in mean global temperatures which affect the amount of water in the ocean store and its density

Question 37

Isostatic changes

Answer 37

changes in the land level, sea level change is relative

Question 38

What affects changes in global temp and volume of water in oceans

Answer 38

-variations in earths orbit around sun, every 400,000 yrs -variations in amount of energy produced by the sun with a solar maximum every eleven yrs or so -changes in composition of atmosphere due to major volcanic eruptions which reduce incident solar radiation -variations in tilt of earths axis, every 41,000 yrs

Question 39

Climate change and sea level fall

Answer 39

decrease in global temp leads to more precip as snow, turns into ice and so water stored on land in solid rather than ocean store as liquid, leads to reduction in volume of water in ocean store and worldwide fall in sea level temps fall and water molecules contract so more density and less volume- 1 degrees fall means 2m less sea level 130,000 yrs ago- global mean temps 3 degrees higher than now and sea level 20m higher, temps fell during Riss glacial period reaching 7 degrees lower than today and sea level dropped by over 100m

Question 40

Emergent landforms

Answer 40

landforms shaped by wave processes during times of high seas level are left exposed when sea level falls, may be found well inland

Question 41

Raised beaches, marine terraces and abandoned cliffs

Answer 41

raised beaches- areas of former shore platforms that are left at higher level than present sea level, found further inland abandoned cliffs- found behind the beach along emergent coastlines with wave cut notches, caves and arches and stacks marine terraces- larger scale landscape features, do not necessarily have cliffs above them but their formation is same as raised beaches- marine erosion during previous high sea level

Question 42

Isle of portland raised beach

Answer 42

15m above present sea level, formed 125,000 yrs ago during Tyrrhenian inter-glacial period when sea levels were much higher than todays. Portland limestone here eroded by hydraulic action, partly through exploitation of bedding plane weakness

Question 43

Modification of emergent landforms

Answer 43

no longer affected by wave processes but still by weathering and mm isle of portland- 1m layer of frost shattered limestone debris deposited when area had periglacial conditions in last glacial period, cliff itself also gradually degraded by frost weathering leading to rock fall from cliff face post glacial period- warmer and wetter conditions led to development of vegetation on many, further warming means continued degradation and chemical weathering being more influential esp w carbonation on limestone cliffs if temps increase then these landforms could end up at coastline

Question 44

Climate change and sea level rise

Answer 44

increase in global temp means more ice sheets and ice caps melting so more global volume of water and rise in sea level, as temps rise water molecules expand and leads to an increase in volume 25,000 yrs ago- temps 9 degrees lower and sea level 90m lower, since then temps and sea level has risen to current day- Flandrian Transgression, period of signif sea level rise

Question 45

Rias

Answer 45

submerged river valleys formed as sea level rises, lowest part of rivers course and floodplains alongside river may have completely drowned but higher land forming top of valley sides and middle and upper part of course remain exposed, in cross section has deep water in middle and shallow water at edges, exposed valley sides quite gently sloping, in long section they have a smooth profile and water of uniform depth , they reflect original route of river, most formed during Flandrian Transgression underlain by alluvial deposits in buried channels that were eroded by rivers that flowed down to the lower sea levels, during interglacial periods when sea levels rose further deposition occurred as rivers had less surplus energy for erosion, during FT there was infilling of these earlier channels

Question 46

Fjords

Answer 46

submerged glacial valleys, steep valley sides, water is uniformly deep often reaching over 1000m, due to depth of water that occupied fjords in FT marine erosion is high and sometimes they further deepened and sometimes there was infilling w sediments, has a glacial rock basin with a shallower section at end of known as the threshold, results from lower rates of erosion at the seaward end of the valley where the ice thinned in warmer conditions

Question 47

Shingle beaches

Answer 47

when sea level falls as the volume of land-based ice grows, large areas of new land emerge from the sea, sediment accumulates on this surface deposited by rivers and low energy waves, when sea levels rose waves pushed this sediment onshore, some beached at the base of former cliffs and some formed tombolos and bars

Question 48

Modification of submergent landforms

Answer 48

both rias and fjords modified by wave processes acting on their sides at present day sea level, valley sides may also be affected by operation of sub-aerial processes in todays climate which may lead to reduction in steepness of valley sides of fjords sea level predicted to keep increasing so debth will increase and marine erosion likely to increase due to stormier conditions and larger waves shingle beaches being made of unconsolidated material are highly vulnerabke to modification, shingle may be moved even further to northeast and tombolo breaches likely due to storms

Question 49

CASE STUDY: Chesil beach tombolo

Answer 49

30km long, onshore movement of sediment is the cause and reached its present position 6000 yrs ago, at east end the ridge of shingle is 13m high and composed of flinty pebbles, at western end it is 7m high and composed of smaller shingle. if lsd was the cause then sediment should be smaller further east Formation- during flandrian transgression, sediment carried into english channel by meltwater during wurm glacial period accumulated in locations like lyme bay, as sea levels rose this went NE bc of impact of southwesterly prevailing winds and the resultant waves, moved 50km until it attached to Isle of portland st one end and the mainland at the other

Question 50

CASE STUDY: Jurassic coast, concordant coastline

Answer 50

Durdle door- arch formed on a hard limestone headland, on a concordant coastline, erosion of Wealden beds and Greensand was quickly eroded either side of a more resistant rock, forming the headland of durdle door, erosion made crack then cave then arch, weathering and further erosion will eventually lead to its collapse Lulworth cove- portland limestone, hardest layer and acted as barrier to the area, began to erode away and softer rocks such as wealden clay and greensand was exposed, these were much easier to erode away and thus the cove began to form. alpine mountain event caused tectonic pressure which causes the rocks at lulworth to tilt north

Question 51

CASE STUDY: Jurassic coast, discordant coastline

Answer 51

Old harry- series of chalk stacks located on coast, created through thousands of years of erosion and were part of chalk ridge line that formed 65m yrs ago when area was under shallow sea, calcium deposits from sea creatures dying built up chalk and tectonics brought it above sea level before last ice age, started as headland with sea exploiting crack in chalk joints and created a cave which created arch which collapsed and formed the stack of old harry, old harrys wife collapsed and became a stump. due to horizontal strata the wave cut platforms still provide a footing for the stack and stump at low tide Swanage bay- made up of bands of hard and soft rocks, soft rock made of clay and sands and hard rocks of chalk and limestone, soft rock eroded quicker and left a headland of hard rock jutting out and swanage bay forming with deposition occurring there as energy is dissipated from wave refraction around the headland

Question 52

CASE STUDY: Mississippie delta

Answer 52

landforms: natural levees, wetlands, barrier islands (cat island and grand isle), spits, eyots, salt marshes, mudflats, birdfoot delta facts: 4700 sq miles, 3rd longest river system, passes through 31 states, made of clay silt and sand

Question 53

CASE STUDY: Mississippi delta, management

Answer 53

artificial barrier islands created as a natural buffer to erosional waves to prevent flooding following increase hurricanes and storm events floodgates put in marshland protection artificial levees and floodwalls to provide flood protection for communities on the tributaries constant dredging and maintaining of a continuous levee system on both sides of mississippi throughout its delta to preserve shipping channel and protect communities and infrastructure from flooding

Question 54

CASE STUDY: Mississippi delta, long term change

Answer 54

threat of submergence due to rising sea levels, threat to landforms and infrastructure natural course change of the river westwards towards the Atchafalaya river, changes the area in which sediment deposition and floculating occurs suffered large scale land loss during historic period because of disrupted sediment supply and accelerated global sea level rise- leveeing the river cut the tie between the sediment filled river and its delta stopping the cycle of new wetland growth so sediment is being completely wasted and the delta is deprived of sediment, sediment is also trapped behind dams upriver

Question 55

CASE STUDY: Mississippi delta, short term changes

Answer 55

natural disasters- hurricane katrina 2005 caused huge amounts of flooding and destruction of barrier islands, destroyed wetlands digging mangroves large scale in 1980s for aesthetics has made land more vulnerable to erosion, no roots stabilising the land, no trees to dissipate energy from waves urban development of new orleans adds pressure to land, sinking 5cm per year bp oil disaster- deepwater horizon oil rig explosion led to Macondo well spewing 206m gallons of oil into gulf damaging delicate shoreline and accelerating erosion, thousands of acres of coastal marsh were damaged and the communities, economy and wildlife of gulf coast were disrupted