coastal landscapes
- Created by: Devika_C
- Created on: 05-01-20 15:53
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- coastal landscapes
- waves
- waves FORM when wind is blown over the sea : the friction causes ripples which turn into waves
- WHEN THE WAVE REACHES THE COAST : the water is in a circular orbit which is broken down due to the friction with the seabed.
- crest of wave moves faster and water becomes shallower and the wave moves forward
- the wave breaks and collapses on the beach
- water which rushes UP the beach : SWASH
- water which returns: BACKWASH
- the wave breaks and collapses on the beach
- crest of wave moves faster and water becomes shallower and the wave moves forward
- two types
- constructive
- FORMED : by storms far away COMMON : in the summer
- waves are far apart
- low waves + gently sloping wave front
- strong swash + weak backwash
- low waves + gently sloping wave front
- waves are far apart
- FORMED : by storms far away COMMON : in the summer
- destructive
- FORMED : by local storms close to the coast COMMON : in the winter
- waves are close together
- high waves + steep wave front
- weak swash + strong backwash
- high waves + steep wave front
- waves are close together
- FORMED : by local storms close to the coast COMMON : in the winter
- constructive
- FETCH : the distance the wave-generating winds blow across the water
- the longer the fetch the bigger the wave
- weathering
- Weathering: the weakening or decay of rock due to the weather
- three types
- mechanical
- freeze-thaw : water collects in cracks - water freezes and expands = larger cracks - temp rises = ice thaws and water seeps deeper - repeated process = fragments break off
- chemical
- carbonation : rainwater absorbs CO2 and becomes slightly acidic - contact with alkaline rocks = dissolves due to a chemical reaction
- biological
- plant roots grow in cracks in rocks and animals burrow into weaker rocks
- mechanical
- mass movement
- the downward movement of weathered material
- 4 examples
- ROCKFALL : rock breaks away due to freeze-thaw
- LANDSLIDE : blocks of rock slide downhill
- MUDFLOW : saturated soil and weak rock flows downhill
- ROTATIONAL SLIP : slump of saturated soil and weak rock along a curved surface
- erosion processes
- SOLUTION : dissolving of soluble chemicals in rock
- CORASSION: rock pieces are picked up by the sea and thrown at the cliff where it scrapes away rock
- ABRASION : sandpaper effect - making a rocky platform smooth
- ATTRITION: rock fragments knock into each other in the sea making them smaller
- HYDRAULIC POWER : power of waves onto a cliff moves trapped air into cracks which causes the rock to break
- coastal transport
- SOLUTION: dissolved chemicals
- SUSPENSION : particles carried within the water
- TRACTION: large pebbles rolled along the seabed
- SALTATION: bouncing motion of particles too heavy to be suspended
- LONGSHORE DRIFT: moves sediment along the beach in a zig-zag pattern
- landforms
- deposition landforms
- BEACHES: are deposits of sand and shingle
- SAND DUNES: at the back of the beach, sand blown inland can build up to form dunes
- SPITS & BARS: - spit = long finger of sand jutting out into sea - bars = form when long-shore drift causes spits to grow across a bay
- barrier beaches = when offshore bars have been driven on shore by rising sea levels [ eg: Chesil Beach in Dorset]
- erosion landforms
- - influenced by rock type and geological structure - different rocks erode at different rates
- HEADLANDS & BAYS : more resistant rock is eroded slowly to form headlands + weaker rock erodes easily to form bays
- CAVES, ARCHES & STACKS: - crack - abrasion and hydraulic action = cave - erosion = arch - roof collapses = stack - more erosion = stump
- CLIFFS & WAVE CUT PLATFORMS: erosion against the cliff will eventually form a wave-cut notch - this repeats until the overlaying cliff collapses - this happens again and again, leaving a wave-cut platform
- SWANAGE, DORSET [south coast of england]
- important factors of the formation = rock types and geological structure
- discordant coastline = alternating bands of harder and softer rock = headlands and bays
- (concordant coastline = one band of rock which is parallel to the coast) { not swanage }
- examples
- HEADLANDS: The Foreland, Ballard Point, Peveril Point & Durlston Head
- BAYS: Studland Bay, Swanage Bay & Durlston Bay
- BEACHES: in Studland Bay & Swanage Bay
- STACK: Old Harry
- deposition landforms
- management
- HARD engineering
- SEA WALL - concrete or rock barrier at the top of beaches to reflect waves out to sea
- [+] -effective -creates a walkway
- [-] - looks unnatural - very expensive + high maintenance costs
- GROYNES - rock structures built at right angles to the beach which traps sediment from moving from longshore drift
- [+] - creates a wider beach which is good for tourism - not expensive
- [-] - unnatural and unattractive - erosion elsewhere
- GABIONS - rock-filled cages that support a cliff and provide a buffer against the sea
- [+] - cheap - improve cliff drainage
- [-] - unattractive - cages rust
- ROCK ARMOUR - piles of large boulders at foot of cliff (rocks absorb wave energy)
- [+] - cheap -adds interest - easy to maintain
- [-] - expensive to transport rock - obtrusive - not local geology
- SEA WALL - concrete or rock barrier at the top of beaches to reflect waves out to sea
- SOFT engineering
- BEACH NOURISHMENT - sand or shingle is dredged offshore and transported to the coast by barge
- [+] - cheap - blends in with landscape - bigger beach means more tourism
- [-] - needs constant maintenance
- DUNE REGENERATION - grass is planted to stabilise dunes and help them develop
- [+] - natural environment which is good for wildlife - cheap
- [-] - time-consuming - can be damaged by storms
- DUNE FENCING - fences are used to encourage new dune formation and keeps people off newly planted areas
- [+] - using this method helps other ecosystems - little impacts on natural systems
- [-] - unsightly -regular maintenance
- BEACH NOURISHMENT - sand or shingle is dredged offshore and transported to the coast by barge
- managed retreat
- allows the sea to flood or erode an area of relatively low-value
- people living in these areas must adapt by moving further inland & scientists monitor thee stretches of coast
- MEDMERRY MANAGED RETREAT
- flat low-lying land in southern England
- land is low value so the sea wall was allowed to breach in 2013
- costs : £28 million to - create a large natural saltmarsh - help to protect surrounding lands - wildlife habitats and encourages visitors to the area
- embankments have been built inland to protect farmland, roads and settlements
- LYME REGIS : small coastal town in Dorset on England's south coast
- issues: unstable cliffs + powerful waves cause rapid erosion + sea walls breached many times
- the lyme regis environmental improvement scheme was set up in the early 1900s to provide long-term coastal protection and reduce the threat of landslips. completed in 2015
- features of the scheme: - new sea walls -cliff stabilised - extension of rock armour -creation of beaches COSTS: £43 million
- [+} - new beaches = increased visitors - defences withstood winters - harbour is better protected
- [-] - more visitors = conflict due to traffic congestion and litter - defences spoil the landscape - sea wall interferes with natural processes
- HARD engineering
- waves
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