- Created by: holly_u
- Created on: 21-03-18 15:00
Distribution of hazards
clusters along plate boundaries. 70% in 'Ring of Fire' in Pacific Ocean caused due to release of energy along a fault causing seismic waves.
Also along plate boundaries of the 500 around 50 erupt a year caused by magma rising between cracks in the crust.
Types of boundaries:
Constructive- plates move apart allowing magma to rise
Destructive- plates collide and more dense subducts beneath less dense
Conservative- plates slide past each other
Plate movement and volcanic/ earthquake activity:
- Constructive- spreading ridges in oceans create small earthquakes and low hazard as in sea. Volcanoes are less explosive especially under sea e.g Mid Atlantic Ridge. Basaltic magma.
- Destructive- strain built when one plate subducts beneath other, most damaging earthquakes and volcanoes. Also fold mountains.
- Conservative- strong earthquakes e.g San Andreas Fault in California.
Intra-plate activity and types of lava
previous weaknesses in rock due to continental drift being reactivated
Intra-plate volcanoes- Hotspots
Hot mantle from core of the earth rises and melts the rock and forms a volcano. Plates move over the stationary hotspot creating more volcanoes.
e.g chain of Hawaiin volcanoes in the Pacific
e.g Yellowstone National Park, US. Supervolcano. The emptying of the magma chamber beneath caused a Caldera to form due to it collapsing.
Types of lava:
- Basaltic=thin & runny. Very hot. Gentle erputions
- Ryholitic= slow & violent erpution. 800-1000 degrees celcius
- Andeistic= thick & stiff. Violent. 650-8000 degrees celcius (melting of lithosphere)
Theory of plate tectonics
1912- Wegener proposed continental drift but had no evidence
1918- WW1 sonar technology discovered sea floor not flat
1919- Arthur Holmes found convection currents
1946- solar technology found mountains and volcanoes
1963- plageomagnetism supporting sea floor spreading
1983- GPS allowed tracking of earths movement
Asthenosphere: Inner core (solid), outer core (liquid), mantle and crust.
Lithosphere: crust. thin oceanic and thick continental
Continental drift (1912): radioactive decay from earths core causes convection currents in mantle moving the crust floating on mantle.
Plageomanetism (1963): magma rises from crust and every 200,00 years the earths magnetic polarity changes causing bands of different magnetisms. Scientists use to age rock.
Theoretical frameworks continued
Seafloor spreading: constructive plates move apart allowing magma to rise. This builds up creating a ridge e.g Mid-Atlantic Ridge. MAGMA JUST FILLS GAP, not driving force of plates.
Subduction: at destructive plate margins when the dense oceanic plate subducts beneath the thick continental plate plates get stuck and pressure builds.
Slab pull: the pulling force of the dense plate at destructive margins forces the whole plate to sink down and melt into the mantle. GRAVITY.
Physical processes affecting volcano and earthquak
Earthquake magnitude and focal depth- THE BENIOFF ZONE
= an area of seismiscity relating to slab pull in the subduction zone. different speeds and movements of rock create quite deep earthquakes.
Earthquake waves and effects
Study of earthquake waves = seismology
Primary (P) Wave- fastest and travel through solid/ liquid/ gas. Compression and expansion in direction of travel
Secondary (S) Wave- slower and travels only through solids. Moves up and down at right-angles to direction of movement
Love (L) Wave- vibrate on surface of the earth on a horizontal plain so can damage infrastructure/ houses etc
Crustal fracturing- seperation in a geological formation due to extreme pressure
Ground shaking- the crust rebounds either side of the fracture causing the ground to shake
Liquefaction- water saturated material e.g soil loses strength and behaves like a liquid
Landslides- slopes weaken causing mass movement of material downwards
Effects of volcanoes and Tsunamis
Lava flows- non-esplosive lava flows outside of the volcano
Pyroclastic flows- fast moving currents of hot material (glass, rock) erupt outwards
Gas eruptions- gas trapped in rock dissolve in magma and are released through groundwater
Ash fall- ash (rock, glass, minerals) dissolve in magma and are propelled into atmosphere
Jokulhaup- sudden melting of glaciers causing flooding. Rapid
Lahars- hot/ cold flow of mud made of silt and sand caused by water
Caused by: undersea earthquakes and landslides at subduction zones. Sea bed displacement as the seismic waves cause it to move upwards, so causing water column displacement too. It creates a series of waves which are only hazardous when at a coastline as the grow in height as water becomes shallower.
Impact depends on: length of earthquake, distance travelled, amount of coastal buffers e.g mangrove forests and degree of coastal development
Natural hazards, disasters and reasons for
Natural hazard- a physical event which has the potential to threaten life and property
Disaster- a physical event which causes a significant impact on a vulnerable population
Community threshold for resilience- the capacity of a community can recover quickly
Things increasing resilience: optimism, wealth, pre-planning, good communications
Things decreasing resilience: lack of skills/ knowledge, environmental degradation, lack of doctors, unrealistic views of disaster
Hazard risk equation= frequency x level of vulnerability/ capacity that can cope
Reasons for exposure to hazards:
- 'Russian roulette' acceptance of the fact
- Unpredictability, unsure when hazards will occur
- Lack of alternatives, economic reasons or lack of skills
- Changing levels of risk, may increase/ decrease over time
Explanation for risk faced is combination between vulnerability and an actual hazard
ROOT CAUSES- limited access to power, structures, resources
DYNAMIC PRESSURES- lack of skills, ethical standards and rapid population growth, deforestation, debt repayment
UNSAFE CONDITIONS- fragile environment and society
Haiti, 2010 (LIC)
Root causes- corrupt government
Dynamic pressures- rapid population growth, deforestation, in debt to France, Germany abd US, lack of education
Unsafe conditions- 80% below poverty line, poor infrastructure, only 39% access safe water
Japan, 2011 (HIC)
Root causes- Fukushima power plant on coast, sea wall only 9m
Dynamic pressures- high population near coastline, lack of coastal buffers
Social and economic impacts of hazards
HIC- Tohoku, Japan, 2011. Social= 15,000 deaths, Economic= $300 billion damage Environmental= nuclear debris
LIC- Haiti, 2010. Social= 230,000 killed, water-borne illnesses. Economic= $7.8 billion damage Environmental= small landslides, risk of oil spillages
HIC- E15, Iceland, 2010. Social= 20 farms destroyed and evacuations. Economic= 100,000 air journeys disrupted costing $200 million per day. Environmental= volcanic ash fertilised land
LIC- Monsterrat, 1997. Social= 11,000 evacuated and homes destroyed, 19 killed. Economic= lahars destroyed roads and airport.
HIC- Tohoku, Japan, 2011. Social= 15,000 killed, water-borne diseases. Economic= $300 billion damage. Environmental= nuclear waste
LIC- Indian Ocean, 2004= Social= 250,000 killed, water-borne diseases. Economic= fishing & tourist industry destroyed. Environmental= turtles killed, coral ruined
Measuring Tectonic hazards
Richter Scale- 1-9. It measures height of waves . Each level is 10x stronger.
+ wherever the earthquake is it will measure the same on the scale
Mercalli Scale- 1-12. Measures physical impacts felt by humans. 12= total damage.
- relative, people experience different amounts of shaking. Subjective
Moment Magnitude Scale- 1-10. Measures in terms of energy released. Calculated by amount of slip, earth rigidity and area effected.
Volcanic Expolisivity Index- 0-8. Measures explosiveness through volume of product, height of eruption cloud and qualative observations. Each level is 10x stronger.
A hazard profile is a technique to compare physical characteristics of hazards.
+ They help decision makers to rank hazards and allocate resources and aid.
Magnitude is most useful to compare
- difficult to compare across hazards as they have different impacts on communities
Speed of onset least useful for comparing
Volcanic- Montserrat, 1997 vs E15, Iceland, 2010
Monsterrat= low magnitude, very long speed of onset, small areal extent (only on island),
E15= high magnitude (4 VEI), very large areal extent (100,00 flights cancelled), medium speed of onset (months), not frequent
Earthquake- Haiti, 2010 vs Tohoku Japan, 2011
Haiti= high magnitude (7), smaller areal extent (only Haiti), relatively frequent
Tohoku= very high magnitude (most powerful ever), very frequent, short duration (6 mins)
Tsunami- 2004 Indian Ocean vs Tohoku Japan, 2011
Indian Ocean= strong magnitude, rapid speed of onset, wide areal extent, short duration
Tohoku= high magnitude, shorted speed of onset (10 mins), short duration (4-5 mins)
Factors influencing vulnerability
Access to education= people are unaware of ways to protect themselves e.g planning ahead etc
Access to housing= low quality housing makes less resilient as their homes are not hazard proof so after a disaster they have no home
Acess to healthcare= people who are undernourished/ sick have weaker immune systems and are more likely to contract diseases after a hazard e.g cholera.
Population density= high is unstable environment because living close together so more death. Quick spread of disease etc.
Isolation= unable to recieve accessible help/ benefit from changes made to more urban areas e.g earthquake proofing buildings. Also lack of community so can't help
Factors Influencing Vulnerability- Governance
Governance: (the way people and insitutes run their public affairs)-
Weak political organisation and corruption leads to vulnerabiliy as resources won't be distributed equally and decisions won't benefit those who need it.
Political= creating policies e.g planning.
Economic= decision making on countrys economy.
Administrative= policy implementation. For disaster risk reduction it includes: landuse planning, safety standards...
good- Tohoku, Japan, 2011 (HIC)
Good building construction- strict regulations, Well prepared- emergency kits in offices, early warning system, evacuation shelters, education e.g emergency drills in schools, BUT failed to protect Fukishima power plant
bad- Port-au-Prince, Haiti, 2010 (LIC)
High level of corruption- poorly allocated resources, Lack of building regulations- poorly built slums affected by groundshaking, Lack of preperation- so when struck unprepared
bad- Sichuan, China, 2008 (Emerging)
Government ignored building regulations so schools etc built & accepted bribes from builders
Development and Disasters
Disasters limiting development- destruction of infrastructure and workers killed, made disabled and lack of (migration)
Disasters create development- favourable area for disaster-risk reduction measures, resources allocated there, reconctruction creates opportunities
Development causes disasters- unstainable development creates unsafe working conditions and creating inequality
Development reducing disasters- access to safe drinking water, food and shelter, technology can reduce poverty, builds communities and recognises excluded groups e.g ethnic minorities, women, provides jobs
Hazard events and context
Developed- TOHOKU, JAPAN, 2011
Physical factors and context: Two destructive plates slip 80m. Occured 20-30km below ground
Impacts: 15,000 killed, $300 billion damage, caused a tsunami
Emerging- BAM, IRAN, 2003
Physical factors and context: 6MMS. One plate subducted beneath other near Japan trench. Occured very early morning so people weren't prepared.
Impacts: 43,000 deaths, people traumatised, traditional mud-brick houses destroyed
Responses: 60 countries gave aid, 81 emergency teams
Developing- HAITI, 2010
Physical factors and context: 7MMS. Conservative plates slipped (North American and Carribean)
Impatcs: 230,000 killed, $7.8 billion damage, airport damaged
Tohoku had such extreme economic damage due to it being highly developed. Bam had so many deaths due to it occuring at night, whereas Haiti had so many due to high population density and lack of preparedness as LIC. However less economic damage as buildings etc not expensively built.
Swiss Cheese Model
Used in risk management. It explains how one hazard can cause many other events if holes 'align'
The layers of cheese represents safety systems, and the holes represent weaknesses in defence. e.g Japan's sea wall was only 9m high so couldn't protect against the tsunami
governance= the way people/ instutions run their public affairs can be administrative/ economic/ political governance.
inequality= an unfair situtaion/ distribution of resources
development=dthe process of social/ economic/ political change affecting peoples lives
Disaster trends and mega disasters
Since 1960- Total number has increased but number of deaths is lower recently due to improved technology, planning and quicker responses, number of people affected is increasing for meteoroligical (extreme weather - drought) and hydrological hazards (water events), economic costs drastically increased due to more investment in infrastructure etc..
Why this data is unreliable:
Disaster data is too hard/ big to collect
Some countries hide information relating to tourist deaths
There are primary and secondary deaths (disease)
Historical data is unrelaible
E15, Iceland, 2010
Regional= 20 farms destroyed, ash covering land
Global= 100,000 flights cancelled costing $200 million per day, countries e.g Africa couldn't import goods such as fruit and veg so they perished
Regional= health and safety issues, asthma, homes destroyed and covered in ash
Tohoku, Japan, 2011
Regional= paddy fields destroyed affecting incomes and fishing boats destroyed
Global= nuclear debris washing ashore 2 years after event in USA
Regional= 19,000 killed, people traumatised, water-borne diseases e.g cholera
PHILLIPINES- 7000 islands covered in rainforests
Volcanoes- VERY COMMON (Mount Mayon)
Earthquakes- sometimes (destructive boundary)
Cyclones- MOST COMMON
Drought- very rare but sometimes El Nino causes it
CALIFORNIA- highly populated urban area
Earthquakes- frequent (conservative boundary, San Andreas Fault)
Drought- VERY COMMON
Both have: volcanoes, earthquakes
Opposite: Cyclones (Phillipines) and Drought (California)
Hydrometeorological hazards (cyclones, storm surges etc) lead to tectonic disasters because often one will cause a domino effect. e.g cyclones can cause landslides which can lead to tsunamis (water column displacement)
Predicition & Hazard Management Cycle
Earthquakes can be forecasted because of statistical likelihood which helps govs enforce regulations and evacuations. BUT not accurate prediction so trying to improve by looking at movement of lava, animal behaviours.
Volcanoes can be predicted due to warning signs e.g gases released, magma.
Hazard Management cycle
Response- trying to save lives after an event e.g search and rescue
Recovery- helping peoples needs. Short term= shelter. Long term= re-building homes
Mitigation- reducing potential risks e.g re-enforcing buildings
Preparedness- trying to minimise loss e.g early warning systems
Stage 1- preparedness (modify cause& event)
Stage 2- Hazardous event e.g earthquake
Stage 3- Response e.g search and rescue
Stage 4- Recovery e.g building homes (modify the loss)
Stage 5- Mitigation e.g re-enforcing buildings
Modify the event (Mitigation and Preparedness)
Land-use zoning- building in safer areas (macro= large scale)
Hazard resistant design- strengthening buildings (micro= smaller scale)
Engineering defences- tsunami sea walls, replanting coasts (macro)
Diversion lava flows (macro)
Modify the vulnerability (Response)
High-tech monitoring- tsnunami warning systems (macro)
Prediction- e.g monitoring tech of volcanoes (macro)
Education- changing behaviours
Community preparedness- preparing e.g supplies
Adaption- changing to become more suited to the environment
Modify the loss (Recovery)
Emergency aid- short term= disaster aid. long term= relief rehabilitation and reconstruction
Internation Governmental aid= financial load spread through the economy
Insurance- cover for property and losses
Actions of communities- search and rescue etc..
aims to promote strategic approach to reducing vulnerability and risks. 4 priorities:
- understand disaster risk
- strengthen governance
- invest in disaster risk reduction for resilience
- 'Build back better'
Hazard Management Case Studies
Tohoku, Japan, 2011