Geography - Dynamic Landscapes Flashcards
what is sea floor spreading and paleomagnetism?
this happens along divergent plate boundaries, plates move apart so magma rises to the surface and cools. this forms ridges in the sea floor
plaeomagnetism is when the earth’s magnetic field changes direction every 400,000 years. this can be seen as minerals in rocks change direction.
what are the characteristics of p-waves.
- they compress and expand as they move through the crust.
- faster than s-waves
what are the characteristics of s-waves.
move up and down as they move through the crust.
what are the characteristics of:
- love waves
- rayleigh waves
LOVE WAVES
-move from side to side
RAYLEIGH WAVES
- ‘roll’ through the ground.
- causes the ground to move up and down, causing lots of damage.
how do tsunamis form?
- displacement of a large column of water, usually caused by a fault block rising.
- water radiates from all directions.
- wave energy is crowded into a smaller volume of water as it approaches land, this causes the wave to increase in height as it slows down.
- waves can reach up to 20m, around 40% of the energy is deflected back into the sea.
what are the features of the following boundaries: -conservative -divergent -convergent (oceanic-oceanic) -convergent (continental-continental) convergent (continental-oceanic)
CONSERVATIVE
-strike-slip faults cause powerful earthquakes.
DIVERGENT
-small, not very explosive earthquakes.
CONVERGENT (CONTINENTAL-OCEANIC)
- explosive and destructive composite volcanoes.
- tsunamis can also form here due to destructive earthquakes.
CONVERGENT (CONTINENTAL-CONTINENTAL)
- fold mountains
- volcanoes are very rare.
- destructive earthquakes, up to magnitude 9.
CONVERGENT (OCEANIC-OCEANIC)
- forms ocean trenches.
- the more dense plate subducts underneath the less dense plate.
what does the VEI scale measure?
-shows the explosivity of volcanoes.
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how do hot spot volcanoes form?
- radioactive decay sends an abnormally hot mantle plume through the mantle.
- this is hot enough to burn through the crust.
- the crust continues to move but the hot spot stays stationary.
what is the definition of disaster?
an event where a place cannot adjust and there’s significant deaths or economic losses. the UN says that it’s a disaster when there are 500 deaths or more.
what is the definition of hazard?
a physical event which has a negative impact on people causing death, injury etc.
what’s the hazard risk equation?
(hazard x vulnerability) / capacity to cope.
what are root causes in the PAR model?
- political/economic systems etc.
- government corruption, for example.
what are dynamic pressures in the PAR model?
the effects the root causes might have.
what are unsafe living conditions in the PAR model?
the conditions the dynamic pressures will lead to.
what is magnitude?
the size of a tectonic hazard
what is speed of onset?
how slowly or rapidly the tectonic hazard develops
what is duration?
the amount of time a tectonic hazard lasts.
what is areal extent?
how widespread the tectonic hazard is
what is spatial predictability?
the likelihood of a hazard happening in a particular area.
what is frequency?
the number of times the hazard is likely to occur.
how have tectonic disaster trends changed over time?
recently, the recorded number of tectonic disasters has increased.
why have the numbers of tectonic disasters increased?
- equipment is more sensitive.
- we have more communication technology.
- increasing global population.
- urbanisation.
what can effect the accuracy and reliability of data in tectonic hazards?
- many improvements in monitoring.
- disasters aren’t recorded in some areas.
- a disaster might happen in a remote area.
- effort is more towards saving people than collecting data.
what are the criteria for a disaster to be considered a mega disaster?
- 2000 deaths or more
- over 200,000 homeless.
- dependence on aid for over a year.
what are the 3 stages of the hazard management cycle?
- pre-disaster
- response
- post-disaster.
what does the pre-disaster stage of the hazard management cycle involve?
- risk assessment
- mitigation
- preparedness (raising public awareness)
what does the response stage of the hazard management response involve?
- evacuation
- saving people.
- assessing damage.
what does the post-disaster stage of the hazard management cycle involve?
- reconstruction
- economic recovery
- risk assessment.
what does park’s response model show?
- sequence of 3 phases after a hazard event.
- it relates to the socio-economic status of the country affected.
what are the strengths of park’s response curve?
it shows what happens before the disaster and considers all levels of response.
what are the 3 ways of managing hazards?
- modify the event: (change the tectonic hazard)
- modify the vulnerability: (make the population more resilient)
- modify the loss: (accept or share losses from the hazard)
compare the characteristics of shield and stratovolcanoes.
- shield volcanoes are shorter
- shield volcanoes emit runny lava, stratovolcanoes emit viscous lava
- stratovolcanoes have very steep sides.
- stratovolcanoes are very explosive, shield volcanoes aren’t.
- shield volcanoes are formed along divergent boundaries.
why are stratovolcanoes more dangerous than shield volcanoes?
- lava is viscous so it traps gases, it makes it more explosive.
- viscosity also means that there’s pyroclastic flow due to tephra.
- large areal extent
- shield volcanoes aren’t very explosive
what is the littoral zone?
it’s the boundary between land and sea.
how can coasts be classified?
- geology
- energy
- balance (retreating/advancing)
- sea level
what are bedding planes?
horizontal breaks in the strata
what are dips in strata?
the angle at which the rock strata live.
what are faults in rocks?
internal fractures caused by pressure on the rock.
what would a cliff with a horizontal dip look like?
indentations form due to exploitation of bedding planes.
what would a cliff with a seaward dip look like?
it creates unstable cliffs, gravity causes mass movement.
what would a cliff with an inland dip look like?
the cliff is steep and stable.
explain igneous rock in terms of porosity, permeability and resistance.
POROSITY:
no space between rock crystals so it’s non porous so water can’t be absorbed.
PERMEABILITY:
there are no joints or bedding planes so it’s impermeable and nothing can pass through
RESISTANCE:
interlocking crystals make it resistant to marine erosion etc.
explain sedimentary rock in terms of porosity, permeability and resistance.
POROSITY:
grains of sediment aren’t fit close together so it’s porous
PERMEABILITY:
interruptions in sedimentation result in bedding planes, which makes it permeable.
RESISTANCE:
they contain soluble minerals so it’s not resistant to marine erosion.
explain metamorphic rock in terms of porosity, permeability and resistance.
POROSITY:
interlocking crystals don’t let water in
PERMEABILITY:
tightly packed crystals mean it’s impermeable
RESISTANCE:
layers can slide over each other easily but it’s usually quite resistant.
explain the formation of salt marshes.
1) tidal conditions deposit sediment and rivers bring mud and silt to the sides of the eustary.
2) tiny clay particles stick together. once deposited they’re colonised by algae.
3) pioneer plans colonise the salt marsh, they’re xerophytic so they can survive being covered with salty water.
4) over time, the plants trap sediment, which builds up the sand dune to a higher level.
5) the upper part of the marsh is slightly above high tide line. the area is criss-crossed by channels and creeks.
what is a berm?
a build up of material at the end of the beach, formed by constructive waves.
name some sources of coastal sediment.
- cliffs
- eroded rocks
- shells
- weathering and mass movement
how can depositional landforms be stabilised?
- sandy beaches may be backed by sand dunes.
- vegetation stabilises sand dunes due to plant succession.
what is the difference between swash-aligned and drift-aligned beaches?
- swash aligned beach is where the swash is at 90 degrees from the coast.
- drift aligned beaches is where the swash hits the beach at an angle, longshore drift.
what are the types of mechanical weathering
- frost shattering
- salt crystallisation
what are the types of chemical weathering
- oxidation
- carbonation (calcium carbonate reacts with acid rain)
what are the types of biological weathering?
- seaweed acids
- boring molluscs
how are rock falls and block falls formed?
- the cliff face is weathered, and blocks are loosened.
- waves erode a wave cut notch so the rock on the cliff face is unsupported.
- rocks fall to the bottom of the cliff and form talus (scree) slopes.
how does rotational slumping happen?
- a section of a cliff remains intact as it moves down the cliff along a curved slip plane.
- this leaves a crescent shaped rotational scar along the cliff
how do mudflows happen?
in areas with higher clay content, mudflows happen, which spill out over the foreshore as a love
how can eustatic change happen?
-THERMAL EXPANSION:
more heat energy results in kinetic energy in the water molecules. this means that they’re spaced apart more. this means that the same volume of water takes up more space.
-ICE CAPS MELTING
ice caps melt, adding more water to the sea and causing sea levels to rise
how has dam construction in the nile delta caused coastal erosion?
- it stops sediment from moving towards the coast.
- as sea levels rise and offshore bars are eroded, 33% of the delta land will be lost.
- building of the aswan dam in 1964 reduced terrestrial sediment supplies. this leaves coasts vulnerable.
what are the key players on the holderness coast and what are their opinions?
-central government agencies:
responsible for coastal management but have had their budget cut in 2010
-local government:
funding cut by central government in 2010
-stakeholders in the local economy:
tourist industry wants greater spending on coastal protection
farmers want money to be spent on protecting their land
residents want protection for their homes
insurance companies are reluctant to ensure valuable properties.
how is Bangladesh vulnerable to coastal flooding?
SUBSIDENCE:
some of the islands there have sunk by 1.5 metres. this is due to isostatic change and also the clearance and drainage of 50 islands there so that rice can be grown there.
REMOVING VEGETATION:
deforestation of the mangroves for shrimp farming results in more coastal erosion and waves travelling further inland.
what are the advantages and disadvantages of cliff draining?
ADVANTAGES
- looks natural once completed
- reduces mass movement
DISADVANTAGES
- difficult to implement along the whole cliff without disturbing the cohesion of the rock layers
- doesn’t completely prevent mass movement, only reduces it to an extent.
how is hard engineering used along the Holderness coast?
- 9.2km of the coastline protected by hard engineering structures.
- sea walls along hornsea deflect wave energy.
- groynes at hornsea trap sediment and maintain the beach, but the beach at mappleton is suffering from sediment starvation as a result.
what is holistic management?
managing the entire coastline, taking economic stakeholders into consideration and caring for the environment.
what are the 4 options for shoreline management plans?
hold the line: maintain/upgrade existing defences
advance the line: build defences seaward
managed retreat: allow the retreat of the coastline but manage the rate of recession
no active intervention: do nothing
what factors would decision makers consider when choosing a management option?
- economic value of the coast
- technical feasibility: is it possible to build defences?
- cultural and ecological value of the land
- pressure from communities.
how was the eyjafjallajokull eruption globally significant?
- airlines lost £130m a day collectively
- the owner of first choice lost between £5-6m a day
- the Kenyan economy lost $3.8m a day because they couldn’t export goods.
- large areal extent.
how was the indian ocean tsunami globally significant?
- 290,000 died
- 14 countries affected by the wave.
- decline in the tourist industry
how was the Japanese 2011 tsunami globally significant?
- affected nuclear policies in the UK and Germany stopped using nuclear power completely as a result.
- shifted the earth’s axis by 4 inches.
how is the coastline at pevensey bay managed?
- hold the line at lyme regis to reduce the threat of landslides. land has been stabilised and a sea wall was built.
- pevensey bay has high amenity value. there was a shingle beach there and groynes protected the beach in 2000, although they’re coming to the end of their lifetime.
- Beach replenishment is conducted each winter to build up an 8km shingle ridge and replace material scoured by destructive waves.
- Shingle is taken from areas of accretion in the bay and redistributed to areas of erosion. Some shingle is dredged from offshore.
- This is done at a cost of £1 million annually.
how can soft engineering be seen as better than hard engineering?
- more sustainable
- more cost effective
- lower environmental impact.
what is plant succession?
when plants decompose to form mud and increase the homous content, making it more fertile. vegetation then colonises the area.
how do sand dunes form?
- sand gathers in rocks or drift wood, forming embryo dunes
- more sand gathers on the embryo dunes. pioneer plants colonise the embryo dune
- pioneer plants alter the pH and humus content of the soil, allowing plants such as marram grass to populate the dunes. this forms yellow dunes.
- yellow dunes mature into grey dunes as the humus content increases.
- pine or oak forests colonise older dunes, this is knows as the climactic community.
how can the loss of a tectonic disaster be modified?
- aid: countries and NGOs send aid to areas affected by disasters. many NGOs start appeals after a disaster has happened.
- insurance: hazard insurance can be offered to homeowners in disaster-prone areas. it protects them against damage dealt to their property by a hazard, but it changes from place to place. in California, many people have disaster insurance as they can afford it, people can’t afford it in Bangladesh so less people have insurance.
how can the vulnerability of a tectonic disaster be modified?
- prediction/forecasting: in places such as Montserrat, technology such as gps and seismographs are being used to monitor the volcano and predict an eruption should it happen.
- land use zoning/building design: buildings in places such as silicone valley have been aseismically designed to withstand the shaking, reducing the vulnerability. land use zoning modifies the vulnerability as people cannot live in dangerous areas where they’re at risk from the hazard. such as in Montserrat, where they have red, amber and green zones.
- community preparedness: where the local population are more resilient to disasters. 1st September, national disaster day in japan where they practice evacuation drills etc.
how can a tectonic event be modified?
- lava diversion/draining: explosives can be detonated on volcanoes to create channels for lava, it can divert it away from communities, such as mt. etna.
- coastal environment strategies: in japan, they have 10m high tsunami walls to defend them against coastal flooding.
what is a multiple hazard zone?
an area which is at risk from 2 or more hazards.
how is the Philippines at risk from geophysical hazards.
22 active volcanoes, such as mt. pinatubo
how is the Philippines at risk from hydro-metreological hazards?
it lies on the pacific typhoon belt
how are there unsafe living conditions in the Philippines?
10% live in self-built housing
what is a hazard event profile?
a diagram which can be used to show the main characteristics of a hazard.
