Tectonic Processes and Hazards Flashcards
What is a hazard?
A potential threat to human life and property
What can a natural hazard be?
Hydro-meteorological (caused by climatic processes)
Geophysical (caused by land processes)
Where do geophysical hazards occur?
Near plate boundaries
- These plates move at different speeds and directions which can cause collisions, earthquakes and volcanic activity
As well as plate boundaries, where else can earthquakes occur?
Near the middle of plates- called intraplate
What could be the reason for intraplate earthquakes?
- Some plates have pre-existing weaknesses which become reactivated, forming seismic waves
- An intraplate earthquake may occur, for example, if solid crust, which has weakened over time, cracks under pressure
Where are volcanic hotspots situated?
An area in the mantle where heat rises as a hot thermal plume- high heat and low pressure causes the lithosphere to melt
- It rises through the cracks to the surface and erupts to form an active volcano
Where do the most powerful earthquakes usually occur?
Convergent or conservative boundaries
What is the OFZ?
Oceanic Fracture Zone
- A belt of activity through the oceans and along the mid-ocean ridges through Africa, the Red Sea, the Dead Sea
What is the CFZ?
Continental Fracture Zone
- A belt of activity along the mountain ranges from Spain through the Alps to the Middle East and Himalayas
Tectonic trends since 1960:
- Total number of recorded hazards has increased
- The number of fatalities has decreased, but there are some spikes during megadisasters
- The economic cost associated with hazards has greatly increased
Why has the economic cost associated with hazards significantly increased since 1960?
- Increases in development as infrastructure in more developed countries is costlier to repair
- Increasing number of insurance policies, especially in developed countries also increases the cost
Why is reporting disaster impacts (i.e fatalities) so hard?
- Depends on whether you look at direct and/or indirect deaths + some impacts take time to be apparent
- The location is important as rural and isolated areas are hard to reach, so it may be difficult to collect data from them. Data also may be difficult to collect in areas with a high population density
- Different methods may be used by different organisations, so different sources might quote different stats
- The number of deaths quoted by the government can be subject to bias
What’s an example of a governments disaster fatality quote being subject to bias?
During the 2004 Indian Ocean Tsunami, the Myanmar Government declared there were no deaths in Myanmar.
- This may be to try and show the government was doing a good job in terms of aid and protection etc.
The earth consists of what four sections?
Crust
Mantle
Inner core
Outer core
What is the crust also know as?
The lithosphere
Describe the crust:
The uppermost layer of the Earth
Thinnest, least dense and lightest layer
Oceanic crust and continental crust
How thick can ocean crust be?
7km
How thick can continental crust be?
70km
What is the mantle also known as?
Asthenosphere
What is the mantle mostly composed of?
Silicate rocks, rich in iron and magnesium
Describe the mantle:
Semi-molten
A temperature gradient near the core generates convection currents
Because of convection currents, the mantle circulates and may contribute to the lithosphere’s plate tectonic movement
Describe the outer core:
Dense, semi-molten rocks containing iron and nickel alloys
Describe the inner core:
Similar composition to the outer core (dense, semi-molten rocks containing iron and nickel alloys)
Solid due to the extreme pressure it experiences
How far below the crust is the inner core?
Over 5150km
Why does the core have such a high temperature?
- Primordial heat left over from the Earth’s formation
- Radiogenic heat produced from radioactive decay
Describe the different plate boundaries:
Destructive plate
- Moving towards each other
Constructive plate
- Moving away from each other
Conservative plate
- Moving parallel to each other
What landforms are created at a constructive plate margin on continental / continental crust?
Rift valleys
Volcanos
Earthquakes
What landforms are created at a constructive plate margin on oceanic / oceanic crust?
Ocean ridges
Earthquakes
Volcanos
What are created at conservative plate margins?
Earthquakes
What landforms are created at a destructive plate margin on continental / continental crusts?
Fold mountains
Earthquakes
What landforms are created at a destructive plate margin on oceanic / oceanic crust?
Ocean trenches
Island arcs
Earthquakes
Volcanos
What landforms are created at a destructive plate margin on oceanic / continental crust?
Volcanos
Fold mountains
Earthquakes
Describe continental and oceanic destructive plate boundaries:
- Denser oceanic plate subducts below the continental
- The plate subducting leaves a deep oceanic trench
- The oceanic crust is melted as it subducts into the asphenosphere
- The extra magma created causes pressure to build up
- Pressurised magma forces through weak spots in the continental plate
- Explosive, high pressure volcanos erupt through the continental plate, known as composite volcanos
- Fold mountains occur when sediment is pushed upwards during subduction
Describe oceanic and oceanic destructive plate boundaries?
- Heavier plate subducts leaving an oceanic trench
- Built up pressure causes underwater volcanos bursting through oceanic plate
- Lava cools and creates new land called island arcs
Describe continental and continental destructive plate boundaries?
- Both plates are not as dense as oceanic, so lots of pressure builds
- Ancient oceanic crust is subducted slightly, but there is no subduction of continental crust
- Pile up of continental crust on top of the lithosphere due to pressure between plates
- Fold mountains formed from piles of continental crust
Describe oceanic and oceanic constructive plate boundaries:
- Magma rises in the gap left by the two plates separating, forming new land when it cools
- Less explosive underwater volcanos formed as magma rises
- New land forming on the ocean floor by lava filling the gaps is known as sea floor spreading
What is the evidence for plate movement and sea floor spreading?
Paleomagnetism
- The study of rocks that shows the magnetic fields of the Earth
Explain paleomagnetism:
- As new rock is formed and cools, the magnetic grains within the rocks align with the magnetic poles
- Our poles switch periodically
- Each time these switch, the new rock being formed at plate boundaries align in the opposite direction to the older rock
- On the ocean floor either side of conservative plate boundaries, there are symmetrical bands of rock with alternating bands of magnetic polarity, which is evidence of seafloor spreading
Who theorised the evidence for seafloor spreading and plate movement?
Harry Hess
Describe continental to continental constructive plate boundaries?
- Any land in the middle of the separation is forced apart, causing a rift valley
- Volcanos form where the magma rises
What are the forces that influence how convergent boundaries occur?
Ridge push
Slab pull
Describe ridge push:
One of the main driving forces of plate tectonics
- New ocean crust is formed at mid-ocean ridges and stands 2-3km above the ocean floor
- As the crust moves away from a mid-ocean ridge, it cools and becomes denser and thicker
- This causes the lithosphere to slope away from the ridge and gravity pulls the lithosphere down this slope, pushing it forwads
Describe slab pull:
When a plate subducts, the plate sinking into the mantle pulls the rest of the plate (slab) with it, causing further subduction
Describe conservative plate boundaries:
Between any crust, the plates move in different directions are at different speeds.
No plates are destroyed so no landforms are created
When these plates move, a lot of pressure is built up.
- On Oceanic crust, this movement can displace a lot of water.
- On continental crust, fault lines can occur where the ground is cracked by the movement
Describe oceanic crust:
Low density of rock
Mainly basalt
Thin
Newly created
Describe continental crust:
Less dense
Mainly granite
Thick
Old
What does the density of a plate determine?
Whether the plate subducts or is forced upwards.
This will determine the landscape and hazards the margin is vulnerable to.
What are the different mechanisms that can cause plate movement?
Mantle convection
Slab pull
Describe mantle convection:
Radioactive elements in the core of the earth decay which produces a lot of thermal energy
- This causes the lower mantle to heat up and rise, but as the magma rises it cools down and becomes more dense and begins to sink back down to the core
- These are convection currents, which push the plates
Who first theorised slab pull?
Dan McKenzie
What is thought to be the main cause of plate movement?
- It was initially thought to be convection currents, but now researchers believe its slab pull.
- Convection currents seem too weak to move massively dense plates
What happens when plates become stuck?
- Convection currents in the asthenosphere continue to push, which builds the pressure
- It builds so much that it cannot be sustained and the plates will give way.
- All of this pressure is released in a sudden movement, causing a jolting motion in the plates
- This jolt is responsible for seismic movement spreading throughout the ground in the form of seismic waves (or shock waves)
What is the focus?
- Also known as hypocentre
- The point underground where the earthquake originates from
What is the epicentre?
The area above ground that is directly above the focus
Describe primary waves:
Travels through solids
Compressional
Vibrates in the direction of travel
Travels fastest
Describe secondary waves:
Vibrate at right angles to direction of travel
Travels only though solid rocks
Half the speed of P waves
Most destructive because of large amplitude
Describe Love waves:
Near to ground surface- they do not travel through liquid
Rolling motion producing vertical ground movement
Travel the slowest
Most destructive because of large amplitude
Describe Rayleigh waves:
Vertical and horizontal displacement
Travels at 1-5 km/hr
Compressional
How does intensity of waves change from the epicentre?
Intensity of waves will decrease further from the epicentre, as waves lose energy as they travel
What factors affect a location’s vulnerability?
Geology
Geographical location (whether the earthquake occurs near the sea or intraplate)
Education of locals
Durability of buildings
Mitigation
What are the secondary hazards of earthquakes?
Landslides
Tsunamis
Soil liquefaction
Describe soil liquefaction:
- 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
Describe landslides:
- The shaking caused by the earthquake can weaken or damage cliff faces, hills and snow material
- Unconsolidated materials or loose rocks can collapse
- Landslides can travel several miles and accumulate material on the way
- Risk varies with topography, rainfall, soil and land use
Describe the formation of a tsunami:
- When Oceanic crust is jolted during an earthquake, all of the water above this plate is displaced, normally upwards
- The water is then pulled back down due to gravity. The energy is transferred into the water and travels through it like a wave
- The water travels fast but with a low amplitude (height)
- As it gets closer to the coast, the sea level decreases so there is friction between the sea bed and the waves
- This causes the waves to slow down and gain height, creating a wall of water that is on average 10 feet high, but can reach 100
Where do tsunamis normally form?
Generally in subduction zones at convergent plate margins
Most are found along the Pacific Ring of Fire
What does the impact of a tsunami depend on? (6)
Duration of the event
Wave amplitude, water column displacement and distance travelled
Physical geography of the coastline (depth and gradient)
Degree of coastal ecosystem buffer, e.g mangroves or coral reefs
Timing of the event- night or day- quality of early warning system
The degree of coastal development, and its proximity to the coast, especially tourist areas
What are a volcanos primary hazards, and what do they tend to have?
They have a fast speed of onset
- Lava flows
- Pyroclastic flows
- Tephra and ash flows
- Volcanic gases
Describe lava flows:
- Streams of lava that have erupted onto the Earth’s surface
- Fast flowing lava can be very dangerous- this depends on its viscosity (the explosivity and viscosity depends on its silicon dioxide content)
Describe pyroclastic flows:
- Mixture of hot dense rock, lava, ashes and gases which move very quickly along the surface of the Earth.
- Due to their high speeds, pyroclastic flows are very dangerous and can cause asphyxiation for anyone caught in them
Describe tephra and ash flows:
- When pieces of ash and volcanic rock are blasted into the air
- this can cause serious damage to buildings, which can collapse under the weight of ash or tephra
Describe volcanic gases:
- Gases like sulphur dioxide and carbon monoxide are released into the atmosphere
- Due to their potency, these gases can travel a long distance
What are the secondary volcanic hazards and why do they occur?
Occur as a result of the heat produced by the volcano
- Lahars
- Jokulhlaup
- Acid rain
What are lahars?
- Combination of rock, mud and water which travel quickly down the sides of volcanos
- These can occur when the heat of eruption causes snow and ice to melt, but also when an eruption coincides with heavy rainfall
What is a jokulhlaup?
- Snow and ice in glaciers melt after an eruption which causes sudden floods that are very dangerous
Describe acid rain:
- Caused when gases such as sulfur dioxide are released into the atmosphere
What is a disaster described as?
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
How can risk be calculated?
Risk = Hazard * Vulnerability / Capacity to cope
R= H*V/C
Why might a place be at high risk?
- Their capacity to cope is low
- They are quite vulnerable
- The hazard is large / high intensity
What concept does Degg’s model show?
- That hazards are not the same as natural disasters
- A disaster will only occur when a vulnerable population is exposed to a hazard
- If a population is not vulnerable, the hazard will not have a significant effect, thus the event will not be disastrous
What are some ways to classify a tectonic hazard?
The volume of people affected
Economic cost of the disaster
Comparison to previous events, prediction models or average statistics for that location
Describe classifying a hazard through looking at the volume affected:
- The International Disaster Database classifies a disaster as an event where more than 100 people are affected , or more than 10 people die
Describe classifying a hazard through looking at the economic cost:
- Jobs lost, cost of repairs needed, economic productivity lost
Describe classifying a hazard through comparing it to previous events and predictions:
- Some events may be more severe than the average tectonic hazard , due to a series of factors coinciding (e.g bad weather and recent deforestation will worsen the impacts of a tsunami)
What is the Park model?
- A graphical representation of human responses to hazards.
- The model shows the steps carried out in the recovery after a hazard, giving a rough indication of time frame.
Describe features of the curve in the Park model:
- The steepness shows how quickly an area deteriorates and then recovers
- The depth of the curve shows the scale of the disaster
What are the 3 stages in the Park model?
Stage 1- Relief
Stage 2- Rehabilitation
Stage 3- Reconstruction
Describe Stage 1 of the Park model:
- hours-days
- Immediate local response - medical aid, search and rescue
- Immediate appeal for foreign aid - the beginnings of global response
Describe Stage 2 of the Park model:
- days-weeks
- Services begin to be restored
- Temporary shelters and hospitals set up
- Food and water distributed
- Co-ordinated foreign aid (such as peacekeeping)
Describe Stage 3 of the Park model:
- 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 event
What is the Pressure and Release (PAR) model?
- Used to analyse factors which cause a population to be vulnerable to a hazard
- On one side of the model is the natural hazard itself, and on the other side, different factors and processes, which increase a populations vulnerability to the hazard
- This vulnerability is often rooted in social processes
Describe the social processes that vulnerability is rooted in?
- Dynamic and everchanging, and are often unrelated to the hazard itself (e.g poverty, poor governance)
Why is the PAR model complex?
- No two hazards are the same, and the factors leading to vulnerability are interconnected and hard to measure.
What three sections is the progression of vulnerability split into in the PAR model?
Root causes:
- often caused by economic, demographic and/or political processes , often affecting large populations or entire countries
Dynamic processes:
- local economic or political factors that can affect a community or an organisation
Unsafe conditions
- The physical conditions that affect an individual (unsafe building, low income, poor health etc.)
What are the different ways vulnerability can be defined?
Physical
Economic
Social
Knowledge
Environmental
Describe physical vulnerability:
Individuals live in a hazard-prone area, with little protection naturally or through mitigation
Describe economic vulnerability:
- People risk losing their employment, wealth or assets during a hazard.
- MEDCs tend to be more economically vulnerable than LEDCs
Describe social vulnerability:
Communities are unable to support their disadvantaged or most vulnerable, leaving them at risk to hazards.
Describe 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- e.g hazards are an act of God, so individuals don’t mitigate or evacuate (known as fatalist belief)
Describe environmental vulnerability:
A community’s risk to a hazard is increased due to high population density in the area
Give an example of factors in the PAR model leading to a populations vulnerability:
Unsafe living conditions:
- A lack of infrastructure can worsen the impacts of a hazard (such as poor sewage management)
Dynamic pressure:
- The lack of infrastructure may be due to rapid urbanisation, where little planning has been taken to safely construct infrastructure to cope with the rising population.
Root cause:
- Planning and controlling safe population is the government’s responsibility, so the root cause of this disaster may be weak governance.
What are common root causes in the PAR model:
- Weak governance
- Mismanagement by Industry, NGO’s or IGOs
- High reliance on products easily affected by hazards
What are common dynamic pressures in the PAR model?
- Lack of training / knowledge in locals
- Rapid urbanisation
- Poor communication between government and locals
- Natural environment degraded
- Lack of basic services
What are some common Unsafe Living Conditions in the PAR model?
- Lack of infrastructure
- Dangerous location of settlements
- No warning system for locals
- Disease and fire can easily spread between households
What do hazard profiles do and how are they helpful?
- Compare the physical characteristics which all hazards share
- Hazard profiles can help decision makers when deciding where to allocate the most human and financial resources
What do the characteristics of a hazard profile include?
Frequency
- how often it happens
Magnitude
- How extensive an area the event could affect
Duration
- How long the event lasts
Speed of onset
- How much warning time before event occurs
Fatalities
- Number of deaths caused
Economic loss
- Value of assets damaged, lack of industry or economic productivity, insurance policies
Spatial predictability
- The predictability of where would be affected
How can you evaluate the effectiveness of hazard models?
- Can they be applied to every hazard? Do some require a more complex model?
- Does the model take any aspects of hazards into account such as level of development?
- Is there any timeframe?
- Could the model be less vague / include more steps that can be applied to all hazards.
- Does the model present hazards currently? Are there any alterations that could be made to account for hazards affected by climate change?
How can you measure tectonic events?
Volcanic Explosivity Index (VEI)
The Modified Mercalli Scale
Moment Magnitude Scale
Richter scale
What is the VEI?
Volcanic Explosivity Index
A relative measure of the explosiveness of a volcanic eruption, which is calculated from the volume of products (ejecta), height of the eruption cloud and qualitative observations
Like the Richter scale, the VEI is logarithmic: an increase of one index indicates an eruption that is ten times as powerful
What is the Modified Mercalli Scale?
Measures the experienced impacts of an earthquake.
It is a relative scale, because people experience different amounts of shaking in different places.
It is based on a series of key responses, such as people awakening, the movement of furniture and damage to structures.
Doesn’t take into account economic or environmental factors
Scale of I-XII
What is the Moment Magnitude Scale?
A modern measure used by seismologists to describe earthquakes in terms of energy released. The magnitude is based on the ‘seismic moment’ of the earthquake which is calculated from:
- the amount of slip on the fault, the area affected, and an Earth-rigidity factor.
The USGS (United States Geological Survey) uses MMS to estimate magnitudes for all large earthquakes
- It’s a simple measure, so environmental or social impacts must be inferred
What is the Richter scale?
A measurement of the height (amplitude) of the waves produced by an earthquake.
The Richter scale is an absolute scale, wherever an earthquake is recorded, it will measure the same on the Richter scale.
Scale of 0-10
How can hazards be responded to?
Prevention
Preparedness
Mitigation
Adaptation
Describe prevention for a volcanic hazard:
- Volcanic eruptions can’t be prevented
- Only the risk to people can be prevented by not allowing people near volcanic hazards
Describe preparedness for 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
Describe mitigation for volcanic hazards:
- Direct intervention to the volcano, e.g concrete blocks to steer lava away from at risk areas
- Strengthening buildings that are at risk of mudlfows or ash pileup
- Evacuation and exclusion zones
- Mitigating effects on health by having emergency aid and rescue
Describe adaptation for volcanic hazards?
- Move away from area at risk
- Capitalise on opportunities, such as encouraging tourism
- Change profession so it is less likely to be affected by volcanic hazards.
What does the Hazard Management Cycle show?
- The stages of responding to events, showing how the same stages take place after every hazard
What stages take place in the Hazard Management Cycle?
Preparedness
- Being ready for an event to occur (public awareness, education, training)
Response
- Immediate action taken after event (evacuation, medical assistance, rescue)
Recovery
- Long-term responses (restoring services, reconstruction)
Mitigation
- Strategies to lessen effects of another hazard (barriers, warning signals developed, observatories)
How can scientists try and detect signs of an imminent eruption in a volcano?
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 when magma builds up
What are examples of short-term recovery?
- Providing aid, food, water, shelter
- Providing financial assistance so people can rebuild their livelihoods
What are examples of long-term recovery?
- Rebuilding homes
- Building and repairing infrastructure
- Reopening schools and businesses
What are the three different approaches to managing a tectonic hazard and reducing their impact?
Modify the Event
Modify the Vulnerability
Modify the Loss
How do you modify an event?
- You can’t control seismic activity, but you can control the design of buildings, which are said to be the biggest killer during a natural disaster.
- This is done through civil engineering using micro and macro methods
What are micro and macro methods in civil engineering?
Micro
- Strengthening individual buildings and structures
Macro
- Large scale support and protective measures designed to protect whole communities
How do you modify an earthquake?
- 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
How do you modify a tsunami?
- Tsunami walls which work for a given amplitude and threshold of wave
- Replanting coasts with mangroves and coastal forestry which dissipates energy from waves
How do you modify volcanoes?
- Diverting flows of lava
- Reinforce house roofs to withstand large deposits of ash
What are the types of modification that can be used against tectonic hazards?
Land use zoning
Resistant buildings
Aseismic buildings
Lava diversion
Tsunami defences
Describe land use zoning and its pros and cons:
- Preventing building on low lying areas and areas of high risk (close to volcanos or where liquefaction is likely)
PROS
- Low cost
- Reduces vulnerability
CONS
- Stops economic development on some high value land (coastal areas)
- Strict enforcement required
Describe resistant buildings and their pros and cons:
- Buildings with deep foundations, sloped roofs so that ash doesn’t build and create pressure
PROS
- Can help prevent collapsing
- Protects people and their property
CONS
- high cost for larger buildings
- low income families can’t afford this
Describe lava diversion and its pros and cons:
- Barriers and water cooling to divert and slow down lava flow
PROS
- Diverts lava away
- Low cost
CONS
- only works for basaltic lava, low VEI lava
- not feasible for majority of explosive volcanos
Describe tsunami defences and their pros and cons:
- Sea walls which stop waves travelling inland
PROS:
- Reduces damage
- Provides security
CONS
- Very high costs
- Doesn’t look nice
- Can be overtopped
What are types of modification used to modify the vulnerability of a tectonic event?
Hi Tech Scientific Monitoring
Community Preparedness and Education
Adaptation
Describe Hi Tech Scientific Monitoring and its pros and cons:
- Monitors volcano behaviour and predict eruptions
PROS
- Predicting eruption is possible in some cases
- Warning and evacuation can help save lives
CONS
- Costly, in LSCs, volcanoes aren’t usually monitored.
- Doesn’t prevent property damage
- possibility of cry wolf syndrome
Describe community preparedness and its pros and cons:
- involves earthquake kits, preparation days, risk education
PROS
- Low cost and often implemented by NGOs
- Can save lives through small actions
CONS
- Doesn’t prevent property damage
- Harder to implement in isolated rural areas
Describe adaptation and its pros and cons:
- Moving out of harm’s way and relocation
PROS
- Helps save lives and property
CONS
- High population densities prevent it
- Disrupts peoples traditional home and traditions
What modifications are used to modify the loss in a tectonic event?
Short term aid
Long term aid
Insurance
Describe short term aid and its pros and cons:
- Search and rescue and also food, water, aid and shelter
PROS
- Can help reduce death toll by saving lives and keeping people alive until long term aid is provided
CONS
- high costs and technical difficulties in isolated areas
- Emergency services are limited and are poorly equipped in LDC
Describe long term aid and its pros and cons:
- reconstructions planned to rebuild an area and improve resilience
PROS
- Reconstruction can help improve resilience through land use planning and better construction methods
CONS
- Very high costs
- needs are quickly forgotten by the media shortly after the disaster
Describe insurance and its pros and cons:
- Compensation to replace losses
PROS
- Allows people to recover economically by paying for reconstruction
CONS
- Doesn’t help save lives
- Not many people in LDCs have insurance
What is the role of communities in a tectonic disaster?
- In remote and isolated areas it might take a long time for aid to come
- People may begin local recovery operations
- Communities may clear debris from roads and set up temporary shelters
What is the role of NGOs and TNCs in a tectonic disaster?
- NGOs play a very important role from providing funds, coordinating rescue efforts and helping to develop reconstruction plans
- TNCs and NGOs may occasionally cooperate.
- Charity events may be organised by businesses to improve IGOs ability to help
What does the Risk Poverty Nexus state?
- Poverty is both a contributing factor and consequence of a natural hazard
- A positive feedback mechanism can cause further economic loss for already poor countries
What types of inequality are there?
Asset inequality
Political inequality
Social status inequality
Entitlement inequality
What is asset inequality?
Relates to housing and security of tenure, as well as agricultural productivity
What is political inequality?
Where certain groups of people, usually the wealthy and elite, hold quite a lot of power and political influence
What is social status inequality?
Unequal distribution of power, priviliges and resources amongst people in a society.
What is entitlement inequality?
Refers to unequal access to public services and welfare systems, as well a inequalities in the application of rule of law.
What factors can contribute to a population’s vulnerability?
Unstable political governance and/or corruption
Population density
Geographical isolation and accessibility
Level of urbanisation
What are the characteristics of a tectonic mega-disaster?
- Large scale disaster affecting a large spatial area, or large population
- They pose problems in effective management to minimise the impacts
- The scale of the impact may require international support and aid
- Mega-disasters are rare
What are some mega-disasters?
2011 Tohoku earthquake & tsuami
2011 Eyjafjallajokull eruption
What are the two classifications of tectonic hazards?
Seismic hazards
- Generated when rocks within 700km of the Earth’s surface come under such stress they break and become displaced
Volcanic hazard
- Associated with eruption events
Describe the global distribution of earthquakes:
- About 70% of all earthquakes are found in the ‘Ring of Fire’ in the Pacific Ocean
- The most powerful earthquakes are associated with convergent boundaries
What are the patterns of volcanic activity?
- Violence of a volcanic eruption is determined by the amount of dissolved gases in the magma and how easily the gases can escape
- There are about 500 active volcanoes in the world
- About 50 of them erupt each year
- Volcanic activity can also occur near the centre of some plates- hotspots
Who came up with the Continental Drift theory?
Alfred Wegener
How was continental drift discovered?
17th Century
- People realised South America and Africa looked like they should fit together
1912
- Alfred Wegener proposed the theory of continental drift, and the supercontinent, Pangea.
- He used fossil and geological evidence to suggest this but couldn’t back it up with the mechanism.
Describe the timeline of evidence supporting Plate Tectonics:
1915
- Wegener collects fossil, rock and mountain evidence
WW1
- Geologic features are found on the ocean floor
1919
- Its proposed that convection currents exist in the mantle after its discovered it can flow like a liquid
1946
- The ocean floor is mapped to reveal ridges, mountains, volcanoes and trenches
1954
- A worldmap of volcanic eruptios and earthquake epicenters reveals a world-wide pattern
1960
- Hess & Dietz develop the theory of sea floor spreading
1963
- Magnetic rock reveals a pattern of spreading away from the center, away from the Atalantic Ocean
1965
- Wilson proposes the idea that Earth’s crust is made of plates- giant chunks of rock.
1983
- The first GPS is available for public use.
Who was Arthur Holmes?
- 1890-1965
- He came up with the convection currents theory in 1919, which was about the time Wegener’s ideas began to be dismissed
Who was Harry Hess?
- Came up with the Sea floor spreading theory in 1962
Describe the process of sea floor spreading?
- Molten magma from beneath the earth’s crust could ooze up between the plates in the rift in the ocean floor
- As the hot magma cooled in the ocean water, it would expand and push the plates beside it
What does the theory of plate tectonics state?
All of Earth’s surface is made of tectonic plates that move, causing major geologic events along the boundaries between them
Why is the theory of plate tectonics such a significant idea?
Tied together the following concepts:
Continental drift
Seafloor spreading
Magnetic field reversals
Convection in the mantle
What do geologists use the theory of plate tectonics for?
- To show the relationship among geologic events
- Explain the occurrence of earthquakes and volcanic eruptions
- Explain the formation of mountain ranges and oceans
What is the Benioff zone?
This is the area where rock is subducted in the subduction zone that causes earthquakes to happen
Whats an important factor in determining an earthquake’s magnitude?
The position of the hypocentre
What is the hypocentre?
The focus point within the ground where the strain energy of the earthquake in the rock is first released.
The distance between this and the epicentre (on the surface) is caled the focal length
What focus do the most damaging earthquakes have?
A shallow focus of less than 40km
Explain how earthquakes happen:
- Movements are proceeded by a gradual build-up of tectonic strain (elastic energy stored in rocks)
- When the pressure exceeds the strength of the fault, the rock fractures
- This produces a sudden release of energy, creating seismic waves that radiate away from the point of fracture
- The brittle crust then rebounds either side of the fracture, which is the ground shaking
What are the strengths of the PAR model?
- It provides a broad view of vulnerability
- Gives weight to natural hazards
- Provides a framework for looking at livelihoods and vulnerability
What are the limitations of the PAR model?
- It is a tool for explaining vulnerability, not for measuring it
- The model cannot be applied operationally without a great deal of data collection and analysis
Do earthquakes or volcanos cause the greatest impacts?
Earthquakes
- They have a greater range (in terms of primary, secondary impacts & geographical range) than volcanic eruptions
Volcanos
- Relatively small in number and concentrated to particular belts around the world.
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Define governance:
The sum of man ways individuals and institutions, public and private, manage their common affairs.
It is a continuing process through which conflicting or diverse interests may be accommodated and co-operative actions may be taken.
What is economic governance?
Governance includes the decision making process about the economy and how it functions in the global economy
What is administrative governance?
This is the system of policy implementation and requires good governance at all levels- it requires the enforcement of building codes and risk mitigation strategies
What is political governance?
The process of decision making including national disaster reduction. This area brings together different stakeholders to determine the quality of the outcome
What can urban segregation generate?
New patterns of disaster risk
How can urban segregation generate new patterns of disaster risk?
Low-income households are often forced to occupy hazard-exposes areas where there are low land values.
Such places have poor infrastructure and social protection; they are also likely to have high levels of environmental degradation
How can hazard profiles be used?
Governments and other organisations use these to develop disaster plans.
What are the pros of using hazard profiles to compare natural disasters?
- Compare physical processes that all hazards share
- Help identify and rank hazards
- Allows for specific management to be considered
- Identifies hazards that require the most resources and attention
- Good for comparing similar events e.g Haiti Earthquake, Christchurch Earthquake
What are the limitations of using hazard profiles to compare natural disasters?
- Reliability when comparing different events is limited
- Difficulty comparing across hazards
- Perhaps for planning it is better to consider hazards as individual hazards.
What are the trends in tectonic hazards?
- Risks from them are increasing
- This is mostly due to human factors rather than physical factors
For what reasons should we question disaster statistics data?
Location
Political Influences
Why does location mean we should question disaster data?
- Events in remote locations are frequently under-recorded as they are not in the media spotlight, or data can be hard to collect there
Why do political influences mean we should question disaster data?
- Disaster deaths and casulties can be subjected to political influences
- After the 2004 tsunami the impact was ignored by the Myanmar government, but initially overstated and then played down by the Thai government to protect the tourist industry
What are the key characteristics of mega-disasters?
- Usually large-scale disasers on either an aerial/spatial scale or in terms of their economic and/or human impact
- Due to their scale they cause problems for effective management to minimise the impact of the disaster
- The scale of their impact may mean communities often need international support
- These disasters can affect more than one country directly or indirectly.
What are two mega-disasters??
Eyjafjallajokull 2010 Iceland eruption
2011 Japanese Tohoku tsunami
What are disaster hotspots?
- Disaster hotspots occur when two or more hazards occur in the same location
- In many cases, one hazard triggers of exacerbates another- for example, earthquakes trigger landslides
What is hazard management?
A process in which governments and other organisations work together to protect people from the natural hazards that threaten their communities.
The aim is to:
avoid or reduce loss of life and property
provide help to those affected
ensure a rapid and effective recovery
Describe mitigation in the hazard management cycle:
Identifying potential natural hazards and taking steps to reduce their impact.
The main aim is to reduce the loss of life and property
What actions could be taken in mitigation in the hazard management cycle?
Zoning and land-use planning
Developing and enforcing building codes
Building protective structures
Describe preparedness in the hazard management cycle:
- Minimising loss of life and property, and facilitating the response and recovery phases.
- Many activities are developed and implemented by emergency planners in both governments and aid organisations
What actions could be taken for preparedness in the hazard management cycle?
Developing preparedness plans
Developing early warning systems
Creating evacuation routes
Stockpiling aid equipment and supplies
Raising public awareness
Describe response in the hazard management cycle:
Coping with disaster. The main aims are to save lives, protect property, make the affected areas safe, and reduce economic losses.
What actions could be taken for response in the hazard management cycle?
Search and rescue efforts
Evacuating people where needed
Restoring critical infrastructure
Ensuring that critical services continue
Describe recovery in the hazard management cycle:
Short-term
- This focuses on people’s immediate needs, so it overlaps with the response phase. These activities may last for weeks.
Long-term
- This involves some of the same actions, but may continue for months or even years. It includes taking steps to reduce future vulnerability, which overlaps with the mitigation phase, and the cycle continues
What actions could be taken for short-term recovery in the hazard management cycle?
providing essential health and safety services
restoring permanent power and water supplies
re-establishing transportation routes
providing food and temporary shelter
organising financial assistance to help people rebuild their lives
what actions could be taken for long-term recovery in the hazard management cycle:
rebuilding homes and other structures
repairing and rebuilding infrastructure
re-opening businesses and schools
Describe aseismic buildings and their pros and cons:
- Involves cross-bracing, using counterweights, deep foundations
PROS
- protects people and property
- financially possible in the developed world
- basic design can be replicated in the developing world
CONS
- high costs for tall buildings
- older buildings and homes for people on low incomes are too difficult to protect
What is cry wolf syndrome?
- When predictions and evacuation prove to be wrong, so people are less likely to believe the next prediction and warning, and are therefore less likely to evacuate
Describe disaster aid:
- Aid flows to countries and victims via governments, NGOs and private donors.
- In the longer term, aid is used for relief, rehabilitation and reconstruction
- This type of aid is often appropriate to middle and lower income countries
Describe internal governmental aid:
- Typically used in emerging and developed countries where the disaster mitigation is achieved by spreading the financial load throughout the tax payers of the country
- This may include a national disaster fund and release of funds may require a political declaration.
What is the Sendai Framework?
It adovcates for:
The substantial redution of disaster risk and losses in lives, livelihoods and health and in the economic, physical, social, cultural and environmental assets of persons, businesses, communities and countries.
What does the Sendai framework recognise?
That the State has the primary role to reduce disaster risk, but that responsibility should be shared with other stakeholders including local government, the private sector and other stakeholders.
