Rock broken down- mechanical and chemical weathering
Mechanical- eg freeze thaw. Water in cracks. Water freezes, expands- pressure on rock. Thaws, contracts- releases pressure. Repeated freeze/thaw widens cracks cause rock to break.
Chemical- changes chem composition eg acid rain. Dilute acid in rainwater reacts with rocks with CaCO3- dissolve them
Mass Movement- shifting of rock/loose material down a slope (eg cliff)- causes coasts to retreat rapidly. More likely to happen when material full of water- lubricant.
SLIDES- material shift in straight line
SLUMPS- material shifts with a rotation- (semicircle-ish)
Processes of Erosion and Waves
Hydraulic Power- waves crach, compress air into rock cracks-pressure. Repeated compression= bit of rock break off
Abrasion- eroded particles in water scrub/ rub rock in water removing small pieces
Attrition- eroded particles in water smash into each other- break off smaller fragments- smooth off.
Solution- weak carbonic acid in seawater dissolves rock eg chalk/limestone
Corrasion- rock fragments hurled at ciff by waves
formed by wind blowing over sea. Distance wind blows over called fetch. Bigger fetch= more powerful wave
Destuctive- Low swash, high backwash. Material removed from coast. High frequency. High and steep.
Constructive- High swash, low backwash. Deposits material on coast. Low frequency. Low and shallow.
Landforms caused by Erosion
Wave cut platform- erosion at foot of cliff forms wave cut notch. Unstable rock on top collapses. Repeat. Cliff retrats leaving wave cut platform
Headlands and Bays- alternating bands resistant/less reststant rock. Less resistant rock (clay) eroded quickly to forma bay- have a gentle slope, Resistant rock (chalk) eroded more slowly, left jutting out to form headland- steep sides.
Caves, Arches and Stacks- weakness like crack in headland, hydaulic power and abriasion in waves, repeated erosion enlarges cracks. eventually forms cave. Continued erosion deeps cave until breaks through whole headland to form arch. (ed Durdle Door in Dorset) Erosion wears out rock supporting arch until eventually collapses. This forms a stack- isolated and seperate from headland (eg Old Harry in Dorset). Continued erosion reduces its size until it is a stump.
Transportation- movement of material
Longshore Drift- Waves follow direction of prevailing (most common) wind. Hit coast at oblique angle (not right angle), Swash carried up bleach in same direction as waves. Backwash carries material down beach at right angles towards sea. Over time zig-zags along coast.
Four Processes of Transportation
Traction- large particles like boulders pushed along sea bed by force of water
Saltation- force of water bounces pebblie sized particles along sea bed
Suspension- small particles like silt and clay carries along in the water
Solution- soulable materials dissolve and are carries along
When material carried by sea is dropped on coast.
Coasts built up when deposition > erosion
Deposition increases- lots of erosion elsewhere on coast so material available/ lots of trasportaion of material into that area.
Low energy waves (slow) deposit- not strong enough to take back material it carried
long and low
materual deposited on coast
Coastal Landforms caused by Deposition
Beaches- found between highest and lowest water mark ( highest/ lowest place sea level reaches), formed by constructive waves depositing sand/ shing.
Sand beaches- flat, wide, particles small/ weak, means weak backswash can carry them down making long gentle slope.
Shingle beaches- steep, narrow, particles large, means weak backwash cant carry them down, particles build up, steep slope
Spits and Bars- formed by LSD- just beaches that stick out into sea (spit), join with other bit mainland (bar)
Spit- form at sharp bends in coastline eg river mouth, LDS transports sand/shingle past bend & deposits into sea. Strong winds can curve end (forming recurved end). Sheltered area protected from waves- material accumulates, means plants can grow. Over time can become mud flat o salt marsh. (eg Spurn Head in Yorkshire)
Bar- formed when spit joins 2 headlands together. Cuts off bay between headlands from sea. Lagoon can form behind bar. (eg Slapton in Devon)
Coastal Landforms on Maps
Landforms Caused by Erosion
Cant see arches/ caves because of rocks above them.
Stacks= little blobs in the sea
Cliffs= little black lines
Wave Cut Platforms- bumpy edges along coast
Landforms Caused by Deposition
Sand Beaches- pale yellow
Shingle Beaches- white or yellow with speckles
Rising Sea Level and Coastal Flooding
Sea level rising due to glabal warming- 2mm/year (20cm past century) Causes are:
Melting Ice Caps- water stored in land returns to oceans, Increases vol of water
Heating Oceans- Increase in global temp means oceans get warmer and expland.
This will increase Coastal Flooding- more often/ more damage in low lying places (eg Bangladesh/ Maldives)
Economic- loss of tourism (close attractions/ put people off), damage repair, loss of agricultural land- high salt content of sea water reducees soil fertility (crop production affetced for years)
Social- death, pollute drinking water supply, loss of housing (homeless people), loss of jobs (coastal industries shut down after damage)
Environmental- high salt content affect affect ecosystem (kill/ damage organisms), kill vegetation (uproot trees/plants, standing in flood water drowns plants), inreased erosion (large vol, fast, erode lots of material damaging environment)
Political- goverment make reduce flooding policies- eg building more/better defences, manage use of land that might be flooded (stopping people living there)
CASE STUDY- MALDIVES COASTAL FLOODING
Group of Islands in Indian Ocean. Population- 300,000. No of Islands- 1190, 119 inhabited. Av. island height- 1.5m above sea level. 80% land >1m. Scientists belive due to rising sea levels, submerged 50-100 years.
Economic- Loss of tourism (largest industry) airort damage= cut off international tourists // Disrupteed fishing industry (largest export) may damage fish processing plants reducing export & income.
Social- Destroy/ Damage Housing many left homless // Less freshwater available supplies on island already low. if salty seawater pollutes some islands have to rely on rainwater or build expensive desalination plants to meet water demands.
Environmental- Loss of beaches flooding wears away beaches at rapid rates- loss of habitats & exposes land behind to flooding // Loss of soil soil on islands mostly shallow (20cm deep or less)- wash away soil layer, most plants wont be able to grow.
Political- Maldivan gov.had to ask Japanese gov. for $60mil for 3m high seawall, protects Capital of Male // Change in ebvironmentla policies- Maldives pledge become Carbon neutral, wont contibute to global warming increasing flooding, encouraging other gov. do the same // Gov. thinkin buying land (in India, Australia etc) & moving Maldivans there before land is unihabitable.
CASE STUDY- HOLDERNESS EROSION
Coastline- 61km long from Flamborough Head (headland) to Spurn Head (spit) // average rate of erosion - 1.8m/year- some more eg Great Cowden over 10m/year recent // erosion cause cliffs to colapse, material washed away- coastline retreating.
Main reasons for Rapid erosion- Easily eroded rock type mostly made of clay, likely to slump when when causing collapse // Naturally narrow beaches- beaches should slow waves down reducing erosive power but narrow= less protection // Groynes at Mapleton- causing more erosion // Powerful Waves- faces prevailing wind direction, brings waves from NE (from arctic ocean) increase in power over long distances so coasts battered by highly erosive waves.
Impacts on people's lives- homes near cliff risk collapse (eg in Skipsea) // Property prices along coast fallen sharply, houses at risk of erosion // Accesability affetced- roads at clifftops at risk of collapse (eg Southfield Land betweer Skipsea and Ulrome) // Eastington gas terminal only 25m away from cliff edge- accounts for 25% Britain's gas supply // 80000m^2 farmland lost each yeat- huge effect on farmers livelihoods.
Environmental Impacts- Some SSI's are threatened- eg Langoons near Eastington part of an SSSI. Lagoons are seperated from sea by a bar. If eroded will connect lagoons to sea and they will be destroyed.
Coastal Management Strategies (Hard)
Hard- man made built to control sea flow and reduce flooding/ erosion
Soft- schemes set up using knowledge of sea and its processes to reduce flooding/ erosion
Sea Wall- (What) wall made of hard material (eg concrete) that refelcts waves back to sea. (Benefits) prevents coastal erosion, acts as barrier against flooding. (Disadvantages) creates strong backwash- erodes under wall, very expensive to build/ maintain.
Rock Armour- (What) boulders piled along coast. (Benefits) boulders absorb wave energy so reduce erosion/ flooding, fairly cheap. (Disadvantages) boulders can be moved by strong waves so need replacing.
Groynes- (What) wooden or stone fences built perpendicular to coast, trap material from LSD. (Benefits) create wider beaches which creates slow waves, greater protection from flooding/ erosion, fairly cheap. (Disadvantages) starve beaches further down coast making them narrower so less protection for coast leading to greater erosion and floods
Coastal Management Strategies (Soft)
Beach Nourishment- (What) Sand/ shingle from esewhere (eg offshore seabed) added to beaches. (Benefits) create wider beaches which creates slow waves, greater protection from flooding/ erosion. (Disadvantages) taking material from seabed can kill organisms like sponges and corals, v. expensive, has to be repeated.
Dune Regenertaion- (What) creating or restoring sand dunes either by nourishment or planting vegetation to stabilise sand. (Benefits) dunes provide barier between land and se, wave energy absorbed prevemts flooding/ erosion, stabilisation cheap. (Disadvantages) protection limited to small area, nourishment expensive.
Marsh Creation- (What) planting vegetation in mudflats along coast. (Benefits) vegetation stabilises mudflats, helps reduce wave speed, prevents flooding/ erosion, provides new habitats. (Disadvantages) Not sureful where high erosion rates- marsh cant establish itself, fairy expensive.
Managed Retreat- (What) removing existing defense allowing land behind it to flood. (Benefits) Over time land become Marshland, new habitats, flooding/ erosion reduced behind marshland, fairly cheap. (Disadvantages) people disagree over what land is allowed to flood eg flooding farmland affects livelihood of farmers.
CASE STUDY- HOLDERNESS COASTAL MANAGEMENT
11.4km protected by hard engineering
Bridlington- protected by 4.7km long sea wall & wooden groynes.
Horsea- sea wall, rock armour & wooden groynes, protect village from flooding
Withernsea- groynes, sea wall, rock armour infront of wall after damged in severe 1992 storm
Mappleton- two rock groynes, cost £2mil built to protect village/ road from erosion/ flooding
East side of Spurn Head- groynes & rock armour, also protects Humber estuary behing Sp. Hd.
Strategies successful locally but cause problems elsewhere- Groynes protect local areas but cause narrow beaches further down coast- increases erosion (eg Cowden Farm south of Mapleton at risk of collapse into sea) // Material produces from erosion at Holderness normally transported south into Humber Estuary & down Linconshire coast. Reduced material transport= increase of flooding in H.E. beacuse less material to slow floodwater down. // Rate of coastal retreat increase along Linconshire coast- less material added. / Sp. Hd. risk of eroded away- less material added. // Bays forming between protected areas- proteced areas becoming headlands- eroded more heavily. Maintaining defences = more expensive.
STUDLAND BAY CASE STUDY- COASTAL HABITAT 1
Dorset SW England. Southern end eroded (others sheltered from highly erosive waves). sandy beaches around bay with sand dunes and heathland behind them. Heathland is an SSSI and nature reserve. Studland bay= popular for tourists.
Provides Habitats for Large Variety of Wildlife, some specifically adapted for that type of environment.
Marram Grass- folded laves reduce water loss, found in sand dunes where windy/ dry- increases transpiration. long roots take in water/ stabilise itself in sand.
Lyme Grass- waxt leaves, reduce water loss by transpiration.
Grebes- birds dive underwater to find food, feet far back on bodies- makes streamlined
Snakes and Lizards- (eg adders, grass snakes, sand lizards, slow worms) thick, scaly skin reduce water loss, protects them from rough undergrowth of Heathland.
Rare animals live here- eg Dartford Warblers (rare bird in England)
STUDLAND BAY CASE STUDY- COASTAL HABITAT 2
Conflict- Land Use vs Conservation
Some human activities damage environment/ use recourses.
Walking over dunes causes erosion- National Trust Manages the Area
Boardwalks guide people over sand (protected). Some dunes fenced off and marram grass planted- gived dunes chance to recover and grass stabilises them. Information signs put up- let visitors know why sand dune habitat is important/ how to enjoy it without damage.
Boats in the bay- anchors destroy seagrass where seahorses live. Seahorses protected by law- boat owners told not to damage seagrass.
Cigarette fires damage heathland (2008- six acres destoryed) National Trust edicating visitors on dangers and provided fire beaters to extingiush fires.