Tectonics Flashcards
(122 cards)
1
Q
A
2
Q
geophysical hazards
A
caused by land processes, near plate boundaries. these plates move at different speeds and directions which can cause colllisions, earthquakes and volcanic activity.
3
Q
intra plate earthquakes
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assumed that plates have pre existing weaknesses which become reactivated, forming seismic waves. for example, an intra plate earthquake may occur if solid crust, which has weakened over time, cracks under pressure
4
Q
volcanic hotpots
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localised area of the lithosphere which has an unusually high temperature due to upwelling of got molten material from the core (first theorised by tuzo wilson in 1963)
5
Q
where do the most powerful earthquakes occur at
A
convergent or conservative boundaries
6
Q
OFZ
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(ocean fracture zone) a belt of activity through the ocean and along the mid ocean ridges through africa, the red sea and the dead sea
7
Q
CFZ
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(continental fracture zone) a belt of activity along mountain ranges from spain through the alps to the middle east and to the himalayas
8
Q
tectonic trend since the 1960
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- total number of recored hazards increased
- number of fatalities decreased
- amount of people affected increased (population growth)
- economic costs has significantly increased (more developed infrastructure) increasing number of insurance policies (higher cost)
9
Q
why is reporting disaster impacts (e.g. fatalities) controversial
A
- direct deaths or indirect deaths as a cause (some take time to be apparent)
- hard to collect data from certain locations (rural/isolated or high population density)
- different methods produce different results
- bias from governments to show they are doing a good job (2004 indian ocean tsunami the burmese government claimed they had 0 deaths)
10
Q
hot and cold magma
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cooler magma is denser so sinks and hot magma is less dense so rises (particles spread out)
11
Q
why does the innder core experience high temperatures
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- primordial heat left over from earths formation
- radiogenic heat produced from radioactive decay
12
Q
landforms created from destructive plate margins
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(plates move towards each other)
continental/continental (earthquakes/fold mountaines)
oceanic/oceanic (ocean trench/island arc/earthquakes/volcanoes)
continental/oceanic (fold mountains/volcanoes/earthquakes
13
Q
landforms created from constructive plate margins
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(plates move away from each other)
continental/continental (rift valleys/earthquakes/volcanoes)
oceanic/oceanic (ocean ridge/earthquakes/volcanoes)
14
Q
landforms creates from conservative plate margins
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(plates move parallel to each other)
only create earthquakes
15
Q
continental to oceanic destructive plate boundaries
A
- denser oceanic plate subducts
- subduction creates deep ocean trench
- oceanic crust is melted as it is subducted into asthenosphere
- extra magma causes pressure to build
- pressurised magma forces through weak areas in continetal plate
- explosive high pressure volcanoes (composite voclanoes)
- fold mountains occur when sediment pushed up during subduction
16
Q
oceanic to oceanic destructive plate boundaries
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- heavier plate subducts (ocean trench and fold mountains occur)
- built up pressure causes underwater volcanoes
- lava cools and creates new land called island arcs
17
Q
continental to continental destructive plate boundaries
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- high pressure due to low density plates
- no subduction of continental crust
- pile up of continental crust ontop of lithosphere due to pressure between plates
fold mountains from piles of continental crust
18
Q
oceanic to oceanic constructive plate boundaries
A
- magma rises in between the gap left by two plates seperating forming new land once cooled
- less explosive underwater volcanoes formed as magma rises
- new land forming on ocean floor by lava filling gap is known as sea floor spreading
19
Q
evidence for seafloor spreading
A
theorised by Harry Hess in the 1940s
as a new rock forms and cools the magnetic grains within the rock align with the magnetic poles (the north and south poles switch periodically
there are symmetrical bands of rock with alternating banfs of magnetic polarity (evidence for seafloor spreading)
20
Q
continental to continental constructive plate boundaries
A
- any land in the middle of the seperation is forced apart causing a rift valley
- volcanoes form where magma rises
- eventually gap will fill with water and seperate completely from mainland
- lifted areas of rocks are known as horsts whereas the valley itself is known as a graben
21
Q
further forces influences how convergent boundaries occur
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ridge push - the slope created when plates moving apart has gravity acting upon it as it is at a high elevation. gravity pushes the plates further away, widening the gap (gravitational sliding)
slap pull - when a plate subducts, the plate sinking into the mantle pulls the rest of the plate with it, causing further subduction
22
Q
conservative plate boundary
A
between any crust, the parallel plates move in different directions or at different speeds. no plates are destroyed and so no landforms created. when plates move pressure builds up. on oceanic crust this movement can displace alot of water. on continental crust, fault lines can occur where the ground is cracked by the movement
23
Q
different mechanisms that cause plate movement
A
mantle convection - radioactive elements in the core of the earth decay which produce alot of thermal energy. this causes the lower mantle to heat up and rise, as the magma rises it cools down and becomes more dense and begins to sink back down to the core. these are convection current. these convection currents push the plates
slap pull - old oceanic crust will submerge into the mantle. pulling action drags the rest of the plate with it (first theorised by Dan McKenzie)
24
Q
why are tectonic movements not fully understood
A
previously convection current were thought to be the primary cause of plate movement. however it is now believed that slab bull is the primary mechanism for plate movement; convection currents seem too weak to move massively dense plates
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primary waves (p waves)
- travel through solids
- compressional
- vibrates in the direction of travel
- travels at 4-8km/s
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secondary waves (s waves)
- vibrate at right angles to direction of travel
- travels only through solid rocks
- travels at 2.5-4km/hr
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love waves
- near to ground surface
- rolling motion producing vertical ground movement
- travels at 2-6km/hr
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rayleigh waves
- vertical and horizontal displacement
- travels at 1-5km/hr
- compressional
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what type of waves are the most destructive and why
secondary and love waves are the most destructive as they have large amplitudes.
30
why are there aftershocks after an earthquake
due to their different speeds, different waves will hit a location at different times. the aftershock that survivors feel are these different types of waves arriving after each other
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does damage caused by an earthquake decrease with distance from the epicentre?
the intensity of waves decreases with distance as the waves lose energy as they travel. this does not mean that impacts felt or damages caused will always decrease, other factors can affect a locations vulnerability
32
what factors can affect a locations vulnerability from earthquakes
geology, geographical location (was the earthquake near the sea or intraplate), education of locals, durability of buildings, mitigation
33
how does soild liquefaction occur after an earthquake
- affects poorly compacted sand and silt
- water moisture within the soil separates from the soil particles and rises to the surface
- this can cause the soil to behave like a liquid, which can cause building subsidence or landslides
34
how do landslides occur after an earthquake
- the shaking caused by the earthquake can weaken or damage cliff faces, hills and snow material
- unconsolidated material or loose rock can collapse
- landslides can travel several miles and accumulate material on the way
- risk varies with topography of rainfall, soil and land use
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how do tsunamis form from earthquakes
- when oceanic crust is jolted during an earthquake, all the water above the plate is displaced, normally upwards
- the water is pulled back down due to gravity. energy is transferred into the water and travels through like a wave
- water travels fast but with a low amplitude
- as the sea level decreases towards the coast there is friction between the sea bed and the waves
- the waves slow down and gain height, creating a wall of water that is on average 10ft high but can reach 100ft
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where are most tsunamis formed
generally generated in subduction zones at convergent plate margins. most tsunamis are found along the pacific ring of fire, hence the most vulnerable countries are often located in Asia or oceania
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what factors affect the impact of a tsunamis
- population density
- coastal defences
- duration of event
- wave amplitude and distance traveled
- gradient of continental shelf
- the shape of the land - bays will funnel and concentrate tsunamis waves
- warning and evacuation systems
- level of economic and human development
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primary hazards from volcanoes
- lava flows
- pyroclastic flows
- tephra and ash flows
-volcanic gases
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what are lava flows
streams of lava that have erupted onto the earths surface. fast flowing lava that have erupted onto the earths surface. fats flowing lava can be very dangerous which depends on the lavas viscosity (depends on the silicon dioxide content)
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what are pyroclastic flows (nuée ardente)
a mixture of hot dense rock, lava, ash and gases which move very quickly along the surface of the earth. due to their high speeds, pyroclastic flows are extremely dangerous and can cause asphyxiation for anyone cause by the flow
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what are tephra and ash flows
when pieces of volcanic rock and ash are blasted into the air. this can cause serious damage to buildings, which can collapse under the weight of ash or tephra
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what are volcanic gases
gases like sulphur dioxide and carbon monoxide are released into the atmosphere. due to their potency, volcanic gases can travel long distances
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secondary hazards of volcanoes
lahars, jokolhulaup, acid rain
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what are lahars
combination of rock, mud and water which travel quickly down the sides of volcanoes. these can occur when the heat of the eruption causes snow and ice to melt or alternatively when an eruption coincides with heavy rainfall
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what are jokulhlaups
snow and ice in glaciers melt after an eruption which causes sudden flood that are very dangerous
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what is acid rain
caused when gases such as sulphur dioxide are released into the atmosphere
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disaster
a serious disruption of the functioning of a community or society involving human, material, economic and environmental losses which exceeds the ability of the affected community or society to cope using its own resources
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risk equation
risk = hazard x vulnerability / capacity to cope
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why may places be at high risk from a hazard
- there capacity to cope is low
- they are quite vulnerable
- the hazard is large/high intensity
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when does a natural disaster turn into a hazard
a disaster will only occur when a vulnerable population (one that will be significantly disrupted and damaged) is exposed to a hazard
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how does the united nations office for disaster risk reduction (UNISDR) define a disaster
"a serious disruption of the functioning of a community or society involving widespread losses and impacts, which exceeds the ability to the affected community or society to cope with using its own resources"
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how does the volume of people affected classify a tectonic hazard
the international disaster database classifies a disaster as an event where more than 100 people are affected or more than 10 people die
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how does the economic cost of the disaster classify a tectonic hazard
jobs lost, cost of repairs needed, economic productivity lost. the Un sendai framework is an initiative to reduce economic loss due to a disaster, after the huge economic losses during the 2011 tohoku earthquake and tsunami
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what does the park model show
the model shows the steps carried out in the recovery after a hazard, giving a rough indication of time frame
- steepness of curve shows how quickly an area deteriorates and recovers
- the depth of the curve shows the scale of the disaster
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stage one of the park model
relief (hours-days)
-immediate local response - medical aid, search and rescue
-immediate appeal for foreign aid - the beginnings of global response
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stage 2 of the park model
rehabilitation (days-weeks)
- services begin to be restored
- temporary shelters and hospitals set up
- food and water distributed
- coordinated foreign aid - peacekeeping forces etc.
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stage 3 of the park model
reconstruction (weeks-years)
-restoring the area to the same or better quality of life
- area back to normal - ecosystem restored, crops regrown
- infrastructure rebuilt
- mitigation efforts for future events
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what can the park model be used for
comparing hazards using multiple lines on the same graph to show differences in severity and response
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what is the pressure and release model
is used to analyse factors which cause a population to be vulnerable. one side of the model has the natural disaster and the other side has different factors and processes which increase a populations vulnerability to the hazard
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in the par model how is the progression of vulnerability split
split into 3 sections
-root cause
-dynamic pressures
- unsafe conditions
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what is the root cause of the par model
often caused by economic, demographic and or polition processes, often affecting large populations or entire countries
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what is the dynamic pressure section of the par model
local economic or political factors, that can affect a community or organisation
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what is the unsafe conditions section of the par model
the physical conditions that affect an individual (unsafe building, low income, poor health, etc)
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physical vulnerability
individuals live in a hazard prone area, with little protection naturally or through mitigation
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economic vulnerability
people risk losing their employment, wealth or assets during a hazard. MEDCs tend to be more economically vulnerable than LEDCs
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social vulnerability
communities are unable to support their disadvantaged or most vulnerable, leaving them at risk to hazards
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knowledge vulnerability
Individuals lack training or warning to know the risks of a hazard or how to safely evacuate. Alternatively, religion and beliefs may limit their understanding of hazards; hazards are an act of God, so individuals don't mitigate or evacuate (known as fatalist belief).
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environmental vulnerability
A community's risk to a hazard is increased due to high population density in the area.
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common root cause factors in the PAR model
-weak governance
-mismanagement by industry, NGOs or IGOs
- high reliance on products easily affected by hazards
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common dynamic pressures in the PAR model
- lack of knowledge/training
-rapid urbanisation
- poor communication between government and locals
- natural environment degraded
- lack of basic services
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common unsafe living conditions in the PAR model
-lack of infrastructure
- dangerous location of settlements
- no warning systems
- disease and fire spreads easily between households
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what are the characteristics of a hazard profile
frequency - how often in occurs
magnitude - how large an area affected
duration - how long event lasts
speed of onset - how much warning time before event
fatalities - number of deaths caused
economic loss - value of assets, insurance, industry
spatial predictability - predictability of effected area
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evaluating the effectiveness of hazard models
- can they be applied to every model?
- does the model take in all aspects of hazards into account
- is there a timeframe
- could the model be less vague
- does the model present hazards currently
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Volcanic Explosivity Index (VEI)
-measures relative explosiveness of a volcanic eruption
-based on the height of ejected material and duration of eruption
-scale from 0-8 and is logarithmic (increase of 1 is 10x more powerful)
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the modified mercalli scale
-measures the destructiveness of an earthquake
- is a relative scale as people feel different amount of shaking in different places
- subjective based on how mnay people wake up
- scale varies from I to XII
- doesnt consider economic, social, environmental impacts
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moment magnitude scale
- measures the amount of energy released in earthquake
- scale from 0-9
- its a simple measure, so environmental or social impacts must be inferred
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richter scale
- measures amplitude of waves during earthuquake
- most widely used scale
- must infer social or environmental impacts
- logarithmic
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prevention to volcanic hazards
volcanic eruptions cannot be prevented.
only the risk to people can be prevented by not allowing people near volcanic hazards (e.g. preventing building around volcanoes)
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preparedness to volcanic hazards
monitoring increases the notice of volcanic eruptions. meaning warnings can be given out.
education on volcanoes in areas of risk so people know what to do
evacuation procedures planned
training response teams
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mitigation to volcanic hazards
direct intervention to the volcano e.g. concrete blocks to steer lava away from places at risk
strengthening buildings that are at risk of mudflows or ash pileup
evacuation and exclusion zones
mitigating effects of health by having emergency aid and recue
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adaptation to volcanic hazards
move away from area at risk
capitalise on opportunities, such as encouraging tourism
changing profession so it is less likely to be affected by volcanic hazards
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what does the hazard management cycle show
outlines the stages or responding to events, showing how the same stages take place after every hazard
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preparedness
being ready for an event to occur (public awareness, education, training)
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response
immediate action taken after event (evacuation, medical assistance, rescue)
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recovery
long term responses (restoring services, reconstruction)
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mitigation
strategies to lessen effects of another hazard (barriers, warning signals developed, observatories)
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how can volcanic eruptions be predicted
- small earthquakes - called tremors
- changes to the top surface of the volcano as it swells when magma builds up
- changes to the tilt as the slope angle changes whens magma builds up
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short term recovery
providing aid, food water shelter
providing financial assistance so people can rebuild their livelihoods
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long term recovery
rebuilding homes
building and repairing infrastructure
reopening schools and businesses
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micro and macro methods to control designs of buildings
micro - strengthening individual buildings and structures
macro - large scale support and protective measures designed to protect whole communities
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modifying earthquake events
-mainly micro approach
- emphasis put into public buildings like hospitals, police stations and other vital infrastructure
- schools and factories strengthened to help shelter people
- some improvements to private houses
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modifying tsunami events
-tsunami walls which work for a given amplitude and threshold of wave
- replanting coasts with mangroves and coastal forestry which dissipates energy from waves
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modifying volcanic events
- diverting lava flows
- reinforce house roofs to withstand large deposits of ash
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land use zoning + -mitigation
preventing buildings on low lying areas and areas of high risk
+ low costs and reduces vulnerability
- stops economic development on some high value land, strict enforcement required
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resistant buildings + - mitigation
buildings with deep foundations, sloped roofs so that ash doesnt build and create pressure
+ can help prevent collapsing protects people and property
- high cost for larger buildings, low income families cannot afford this
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lava diversion + - mitigation
barriers and water cooling to divert and slow down lava flow
+ diverts lava away and low cost
- only works for low VEI lava
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tsunami defences + - mitigation
sea walls which stops waves traveling inwards
+ reduces damage and provides security
- very high cost, doesnt look nice, can be overtopped
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high tech scientific monitoring + - vulnerability
monitors volcano behaviour and predict eruptions
+ predicting eruptions is possible is some cases, warning anf evacuation can help save lives
- costly, in LDCs, volcanoes arent usually monitored, doesnt prevent property damage
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community preparedness and evacuation + - vulnerability
+ low cost and often implemented by NGOs, can save lives through small actions
- doesnt prevent property damage, harder to impliment in rural areas
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adaptation + - vulnerability
moving out of harms way and relocation
+ help save lives and property
- high population densities prevent it, disrupts peoples traditional home and traditions
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short term aid + -
search and rescue and also food, water, aid and shelter
+ can help reduce death toll by saving lived and keeping people alive until long term aid is provided
- high costs and technical difficulties in isolated areas, emergency services are limited and poorly equipped in LDC
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long term aid + -
reconstructions plant to rebuild an area and improve resilience
+ reconstruction can help improve resilience through land use planning and better construction methods
- very high costs, needs are quickly forgotten by the media shortly after the disaster
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insurance + -
compensation to replace losses
+ allows people to recover economically for paying reconstruction
- doesnt help save lives, not many in LDCs have insurance
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what is the roles of communities during tectonic disasters
in remote and isolated areas, it may take a long time for aid to come and people may begin local recovery operations, communities may clear debris from roads and set up temporary shelters
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what us the role of NGOs and TNCs during tectonic disasters
NGOs play a very important role from providing funds, coordination rescue efforts and helping to develop reconstruction plans. occasionally, TNCs and NGOs may cooperate; charity buckets or events may be organised by businesses to improve IGOs ability to help
106
why do less developed countries suffer more during tectonic hazards
governments in developing countries may not prioritise investing money in hazard mitigation as they tend to focus their resources on development and economic growth. this lack of investment in hazard management often means that less developed countries and their populations are more vulnerable to hazards
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what does the risk poverty nexus states
states that poverty is both a contributing factor and consequence of a natural hazard. it also suggests that a positive feedback mechanism can cause further economic loss for already poor countries
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assest inequality
relates to housing and security of tenure and also agricultural productivity
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political inequality
where certain groups of people, usually the wealthy and elite, hold quite a lot of power and political influence
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social status inequality
often directly linked to space and has a bearing on other dimensions of inequality, including the ability of individuals and groups to secure regular income and access services
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entitlement inequality
refers to unequal access to public services and welfare systems as well as inequalities in the application of the rule of law
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how can unstable political governance and/or corruption contribute to a populations vulnerability
a lack of political cohesion can impact on how prepared a country is for a hazard and can also negatively impact response and recovery efforts after the event
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how can population density contribute to a populations vulnerability
the higher the population density the more people affected by a hazard
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how can geography isolation and accessibility contribute to a populations vulnerability
remote, rural areas often have poor transport links which can negatively effect rescue efforts
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how can the level of urbanisation contribute to a populations vulnerability
urban areas tend to be worse affected by hazards due to two factors: urban areas are densely populated and also have larger amounts of infrastructure meaning there is more economic damage
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how can meeting basic needs affect a populations vulnerability
when food supply, water supply and health needs are met, the population is generally less vulnerable to secondary hazards such as diseases
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how can planning affect a populations vulnerability
land use planning can reduce risk by preventing people living in areas of high risk. secondary hazards may be made worse by deforestation
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how can preparedness affect a populations vulnerability
education and community preparation programmes raise awareness and teach people how to prepare, evacuate and act when disaster strikes
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how can corruption affect a populations vulnerability
if government politicians accept bribes and do unethical things, then vulnerability would increase as money would be invested in crucial areas like emergency services
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characteristics of tectonic mega disasters
- large scale disaster affecting large area/population
- pose problems in effective management to minimise impacts
- the scale of the impact may require international support and aid
- mega disasters are low probability
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how did the 2011 tohoku earthquake/tsunami disrupt business
there was a knock on effect for TNCs such as toyota and BMW which operate and source products from japan. this lost potential revenue for those TNCs and caused general economic uncertainty
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hoe did the 2011 iceland volcanic eruption disrupt business
the significant ash cloud closed european air space, which lead to the halt of goods and trade in the EU by air. this resulted in kenyan flowers couldnt be transported and wilted
