name 3 erosional landforms
- cliffs/wave cut platforms:
- headlands and bays;
- cliff profile features: caves, arches, stacks:
name 6 depositional landforms
- beaches:
- spits:
- offshore bars/tombolo
- barrier islands
- sand dunes
- estuarine/mudflats/saltmarsh
-forms in sheltered environments( spits, bars, bays, coves)
what is eustatic sea level change
sea level change caused by a change in the volume of water or a change in the shape of the ocean basins with global causes
what causes eustatic sea level change
-climate change: increase in temperature causing melting of ice sheet which increases sea level
a decrease in temperature which causes more snow which increases the the water stored in glaciers which reduces the volume of the sea and decreases sea level
- tectonic movements: movements in the crust alter the shape of the earth basins
e. g. sea floor spreading increases the volume of the basin and so decreases sea level
what is isostatic sea level change
sea level change caused vertical movements of the land relative to the sea with local causes
what causes isostatic sea level change
- uplift: the melting of ice sheets causes land to slowly lift up over thousands years due to the removal of weight - -isostatic rebound:
- depression: the accumulation of ice sheets causes a depression due to the new weight
- subsidence: land sinks when ground water is absorbed
- tectonic: tectonic plates e.g. the subduction of one plate under another
5 points on sea level change in the past 10,000
- last glacial maximum sea level was 130m lower than it is presently
- the last time sea levels were this high was 4000 years ago
- sea level rising since 1930
- currently sea level rise per year =2mm
- predicted for sea levels to rise 8-26mm per year by 2100
5 impacts of sea level change in the future
- submergence of low lying islands e.g.0.5 increase in sea levels would completely submerge the Maldives
- changes to coastlines-0.3m sea level rise will result in the lost of 8000km squared of land in Bangladesh’s
- contamination of water sources and farmland
- cause mass migration - international/rural-urban
- displacement
- cultural loss
- soil problems - food security
- increase in the intensity and frequency of storms
3 landforms of emergence caused by sea level fall
- raised beaches: formed when sea level fall leave beaches above tide marks leaving a beach below. the raised beach will become vegetated overtime
- marine platforms: sea level fall exposes wave cut platforms leaving them raised above their former levels
- relict cliffs: cliffs above raised beaches which also become vegetated, erosional landforms are often still present.
- e.g. occur in North Scotland
3 landforms of submergence caused by sea level rise`
- rias: formed where river valleys are partially submerged. they are wide at mouths and become narrower as you go inland
e. g. Milford haven, south wales
-fjords: formed when rising sea levels flood deep glacial valleys to create natural inlets and
harbours. They are deeper in the middle than they are at the mouth , with the shallower section
showing where the glacier left the valley
-e.g. Milford Sound New Zealand
-Dalmatian coasts: formed by sea level rises in areas with with valleys that are parallel to the coast. the valleys are flooded leaving island parallels to coastline
how are cliffs and wave cut platforms formed
- Erosion is concentrated around the high-tide line creating a wave-cut notch
- As the notch becomes deeper the cliff face becomes unstable and collapses
- This leaves behind a platform of the unaffected cliff base
- Over time a wave-cut platform is formed
how are headlands and bays formed
- formed where bands of alternating hard and soft rock are at a right angle to the shore (discordant coastlines
- soft rock is eroded quickly creating bays’
- hard rock is more resistant and erodes less so it sticks out forming a headland
how are cliff profile features formed
- weak joints in cliffs are eroded to form caves
- caves on opposite sides may join or the cave is eroded through to create an arch
- when the arch collapses a stack is formed
- overtime erosion will turn a stack to a stump
how are beaches formed
-beaches are stores in the coastal system formed by the deposition of sediment on shore by constructive waves
features of a beach
- berms: ridges of sand and pebbles found at high tide marks
- runnels: grooves in sand running parallel to shore formed by backwash
- cusps: crescent shaped indentations
how are simple, recurved and compound spits formed
- spits form when the coast suddenly changes direction, e.g. river mouth
- simple: long shore drift continuous to deposit material across the river mouth leaving a bank of sand sticking out.
- recurved: a change in dominant wind direction will cause a spit to have a curved end
- compound: over time recurved ends will be abandoned and new ones created due to changes in wind direction
- the area behind a spit is sheltered from waves and so develops into a mudflats or saltmarshes
how are offshore bars and tombolos formed
- bars: formed when a spit joins two headlands together across a bay or river mouth. a lagoon will form behind the bar
- offshore bars form of the coast and can be partially or fully submerged by sea level rise
- tombolo: a bar that connects an island to shore
how are barrier islands formed
- A barrier beach is usually formed as an extension to a spit and joins two headlands together
- Colonization by vegetation can stabilize the barrier beach and trap further sediment keeping it above sea even at high tide
- when a barrier beach separates from the main land it becomes a barrier island
how are sand dunes formed
- sand deposited by longshore drift is moved up the beach by wind and trapped by driftwood and berms.
- the sand is then colonised by vegetation which stabilises it and encourages more sand to accumulate creating embryo dunes
- overtime dunes migrate inland allowing space for new embryo dunes
- oldest dunes/grey dunes can reach 10m
how are Estuarine mudflats and saltmarshes formed
- Sediment is transported from the river and sea with suspension as the tide goes in and out
- combination of fresh and saline water
- Deposition occurs as a result of flocculation , leading to mud above the high tide level.
- Pioneer plants (Barren sand, lyme grass, sea crouch grass) colonizes the transition zone, leading to more sediment becoming trapped.
- A meadow is formed as sections of the salt marsh rise above the high tide level.
- This leads to the climatic climax of the vegetation succession when trees begin to colonizes the area.
- e.g. Morecomb Bay is the biggest Mudflat in England
- e.g. Thames Estuary
past impacts of sea level change
-increase in severe coastal flooding e.g. kings point, New York: 1995-2004 flooded 80 times
2005-2014 flooded 160 times
- past millennia: sea level rise of 1-2mm per year
now: 4-5mm rise per year - Banda Aceh, 2004 Boxing Day tsunami
- earthquake caused the ocean floor to rise by as much as 40m
- killed 230, 000 in 14 countries
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the concept of a hazard in a geographical context12
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plate tectonics26
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volcanic hazards23
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seismic hazards24
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storm hazards31
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fires in nature17
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hazards case studies9
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coasts as natural systems8
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systems and processes21
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coastal landscape development21
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coastal management7
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coast case studies7
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water and carbon cycles as natural systems9
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the water cycle26
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the carbon cycle10
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water, carbon, climate and life on earth7
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water and carbon cycle case studies13
