- Created by: barry
- Created on: 29-05-18 17:08
Nature of hazards
Nature of Hazards
- Is the threat of substantial loss life, substantial impact upon life or damage to property that can be caused by an event.
- Difference between a disaster and a hazard is that a disaster occurs as a result of a hazard.
- Potential impacts of a hazard depend on the location of the hazard relative to areas of population, and the magnitude and extent of the hazard.
- Primary impact- have immediate effect on the affected area
- Secondary impact- happen after the disaster
- The economy of a area affects the severity of the hazard as in HICS there is enough wealth and potential for redevelopment to rebuild and support those directly affected. However, in LICS the economy is less wealthy.
- Geophysical-driven by the earths own internal energy sources eg, plate tectonics, volcanoes and seismic activity
- Atmospheric- driven by processes at work in the atmosphere eg, tropical storms and droughts
- Hydrological- driven by water bodies, mainly the oceans eg, floods, storms and tsunamis.
Nature of hazards 2
- Fatalism= is a human response to a hazard which involves doing nothing as if it was an acceptance that hazards are natural events and we don’t have control over.
- Adaptation = LEARNING TO LIVE WITH THE HAZARD
- Mitigation = REDUCING SEVERITY OF EVENT BY BEING READY, DIRECT INTERVENTION, SUPPORT AFTER
- Preparedness = MITIGATION STRATEGIES, but anything that prepares people for the hazard event
- Resilience = MITIGATION/ADAPTATION/PREPAREDNESS MANAGEMENT STRATEGIES RESULT IN RESILIENCE
The park model
Park Model of human responses to hazards
Disruption- is delaying on continuity and a hazard event causes disruption to everyday life. The steepness of the downwards curve during a disruption depends on the nature of the event (as a earthquake will have immediate effects and volcano will be over time ). The depth of the curve depends on the scale of the disaster and magnitude of the event.
Relief- is the immediate local and global response in the form of aid, expertise and search and rescue- hours short time period
Rehabilitation- is when infrastructure and services are restoring, possibly temporarily to allow the reconstruction phase to begin asap- weeks/months longer phase
Reconstruction- is restoring to the same or better quality of life before the event took place- months/years long time period. Reconstruction may result in improved QOF as this phase involves mitigating- as aid is received which can be used to build better.
The hazard management cycle
Hazard management cycle
- Preparedness= education and raising public awareness can reduce the scale of a hazard event. Knowing what to do can speed up the recovery process.
- Response= the speed of response will depend on the effectiveness of the emergency plan that is in place, an immediate response focuses on saving lives and co-ordinating medical assistance.
- Recovery= is the restoring the affected area to something approaching normality, short term will be restoring services so that further reconstruction can begin.
- Mitigation= is actions aimed at reducing the severity of an event and assessing its impacts. This can involve direct intervention, such as buildings that can withstand earthquakes or hurricanes.
Plate tectonics history
- Inner core- is a solid ball containing uranium making it radioactive- very hot.
- Outer core- is semi molten (liquid) and also containing lots of iron and nickel
- Mantle- mainly solid areas of molten, a lot of heat and pressure.
- Crust- the outer layer, solid area and very thin;
- Continental crust- is thicker 30-70km thick and is less dense. Lots of cracks and forms continental crust.
- Oceanic crust- is thinner 6-10km thick and denser. Found below oceans.
- Alfred Wegner suggested the continental drift theory in 1912 and that all the plates were joined together like a jigsaw- supercontinent called Pangea which drifted apart.
- Harry Hess studied the age of rocks on the floor of the Atlantic ocean and found that the youngest rocks were in the middle and the oldest near the USA with new rocks still being formed, this confirmed that the sea floor was spreading away from each other.
- Paleomagnetic is where the oceanic plates change polarities, shows millions of years ago that the ridge between plates were joined together and slowly moved away- this confirmed Hess ideas.
Plate tectonics movement
How crust moves
- Radioactive decay in core generates high temperatures
- These hot spots produce heat and melt the outer core and the lower mantle and create convection currents which rise towards the surface
- This molten magma rises to the surface and melts the oceanic crust. This heat causes the lithosphere to expand, rise and so forming the slope of the ridge
- This new rock cools, becomes denser and heavier and slides away from the ridge and encourages new magma to rise and repeat the process = ridge push/gravitational sliding
- This new rock is colder and heavier than the mantle, so it sinks pulling the rest of plate with it = slab pull.
- This plate is heavier/denser than the plate it meets, so it subducts below the lighter plate
Types of plate margins
Constructive continental vs continental
- Radioactive decay releases heat energy and generates convection currents, this rises and tries to melt the crust however it can’t because of its density and high thickness.
- The convection currents no where to go so it moves outwards and the pressure tension causes cracks to form. As a result, a block collapses forming a rift valley (6000km long) - the magma moves through weaker cracks and forms strata sticky volcanoes.
- Eg. Mid Atlantic ridge- African plate.
Constructive Oceanic vs Oceanic
- Radioactive decay in the core radiates heat energy and as a result this heats the mantle generating convection currents. - process known as sea floor spreading developed by Hess.
- As gravitational sliding occurs and as the plates move apart this leads to the formation of the rift valley- in the Mid Atlantic ridge. Earthquakes caused by the movement of magma through the crust.
- Eyjaffjallajokull is a fissure volcanoe found in Iceland.
Types of plate margins 2
Oceanic - Continental:
- The oceanic plate (Nazca) subducts because it is lighter and denser it subducts beneath the continental plate (South American). As the oceanic plate subducts a deep ocean trench is formed and as the oceanic plate is subducted friction causes earthquakes in the Benioff zone.
- As the oceanic plate is subducting the radioactive decay in the core causes convection currents to heat and then rise. The heat causes magma to rise and then it breaks through the continental crust and causes magma to be pushed up- ridge push. This magma cools and becomes more denser and heavier and gravataional slides away from the ridge.The crust is heavier do it pulls the crust downwards- slab pull.
- Magma plutons rise as they are less dense than the continental crust, they move through cracks. The magma plutons rise until it is joined in a magma reservoir, the magma eventually remerges to the surface and creates a volcanoes .
- Fold mountains- Andes
- Strato volcanoe- Galaeras
Types of plate margins 3
Continental vs Continental
- Continental plates are lower than the asthenosphere beneath them. Thus, subduction doesn’t occur- no volcanoes.
- Both plates and any sediments deposited between then become uplifted and buckle to for high fold mountains (Himalayas). Earthquakes occur
- EG. Indian Plate and Eurasian Plate
Oceanic vs Oceanic
- When two oceanic plates collide, one plate the denser or faster one subducts beneath the other. This leads to the formation of a deep oceanic trench (Mariana trench) and magma from the Benioff Zone forms crescents of submarine volcanoes along the plate margins causes volcanic eruptions which create Island arcs - cluster of islands that sit in a curved line. (Mariana Islands).
- EG. the pacific plate is subducted beneath the Philippine plate.
- Pinatubo volcanoe- strato volcanoe
Types of plate margins 4
Oceanic vs continental
- 2 plates either slide past each other in opposite directions, or 2 plates slide past each other at different speeds.
- As they move past each other friction builds as the plates snag and grind on one another, and parts of the fault line “LOCK”. When this stress energy is eventually released it sends shock waves (earthquakes) through the earth’s crust.
- NO melting of rock so no volcanoes.
- EG. Pacific plate moving faster than NA plate- San Areas fault line, California USA.
Volcanic hazards spatial distribution
- There is a high density of volcanoes around the “Pacific Ring Of Fire” stretching through Japan, New Zealand and the Philippines.
- Also, there are more commonly found at destructive margins and constructive margins.
- Also, some volcanoes are found in the centre of plates such as the Hawaii hot spot.
Volcanic hazards frequency/ regularity
- The frequency of volcanic eruptions is random. Volcanoes that are dormant rely on average cycles of activity can alert volcanagist which can lead to regional observations.
Volcanic hazards predictability
- The warning signs of an eruption is seismic activities such as rising groundwater temperature, small eruptions, emissions of gasses and landslides/rockfall.
- Volcanoes are monitored are using equipment like constant cameras, seismometer and tiltmeter- will all help to determine when a volcanic hazards Is going to occur.
Volcanic hazards 2
Volcanic hazards magnitude
- VEI = is the volcanic explosive index and is the measure of magnitude of an eruption and is measured by the amount of ejected material and height it relates in the atmosphere.
- High VEI does not mean high death as other factors are involved such as the location which will determine the level of technology which will result in a good warning system which will reduce the amount of deaths. Also, VEI8+ is not likely as they are very rare.
- Case study Nevado Ruiz volcano, Colombia 1985- Was only a VEI 3 and warnings were given (they were late and people had no idea what to do because there were no previous drills) but there were so many deaths because there was 50 m lahars.
Volcanic hazards risk management - Mt Etna
- To prevent the lava from reaching the town of zaffre they used concrete blocks to dam the lava flows.
- Mitigation- they got people out of the danger zone by using strategies like using risk maps and evacuation plans, alongside with practise drills so they were efficiently in getting people out.
Volcanic hazards 3
Pyroclastic flows- are avalanches containing hot volcanic gases, ash and volcanic bombs
Lahars- are volcanic mudflows created when water (from rain or melt water from glaciers) and ash mix. This deadly combination can have devastating results on the surrounding area.
There are 3 main types of lava:
- Basaltic: Made at CONSTRUCTIVE plate margins. They have low viscosity, low silica content but not violent.
- Andesitic: Made at DESTRUCTIVE plate margins. Has medium silica content, temperature and viscosity.
- Rhyolitic: Made at DESTRUCTIVE plate margins. Has high silica content and high viscosity, but low temperatures.
Volcanic hazards case study
Nyiragongo, Congo- constructive plate boundary
- 2002 17th January, African rift valley, Congo.
- African plate splitting in two (continental crust),
- Strato cone, nonviolent VEI 1
- Goma town destroyed (200.000+ homes)
- 147 dead
- Collapsing buildings
- 120,000 made homeless
- Contaminated water
- Many aftershocks 1 was a VEI 5
Volcanic hazards case study 2
Short term responses
- Poor infrastructure made helping/distributing aid very difficult
- Food aid given out freely by UNICEF (took 3 days due to distribute)
Long term responses
- Children and locals were educated on volcanic eruptions.
- UN later distributed supplies like beans, water and health care- costing $15 million
- UN set up camps housing as displaced people
- Adaptation- There is risk sharing between the communities as in helping each other out
- Mitigation- Evacuation was mostly successful. Future, authorities need stock up on recourses. More regular measurements taken by the Goma observatory. Risk map.
- Preparedness- Were not prepared as there were not much time and also perception of a serious hazard not occurring.
- Resilience- Were not resilient as they resulted in looting for survival
Earthquake spatial distribution
There are many seismic events around the edge of the pacific ocean because there is a lot friction along the ring of fire between oceanic and continental plate.
Earthquake frequency & regularity
Small earthquakes occur frequently 300 in a year. Trigger earthquakes are a result of large earthquake pushes a nearby already stressed fault over the point of rupture. An aftershock is a smaller earthquake following the main shock of a large earthquake and these are more predictable as they occur after the main one.
It is impossible to predict when a seismic disaster will occur or where it will occur. Warning signs of an earthquake is: Microquakes, Bulging of the ground and Rising groundwater levels. Also, Earthquakes are monitored by using a sisesomter on a seismograph.
Earthquake hazards 2
- The depth of the focus affects the magnitude of a earthquake- as the shaking becomes less surveer the further the depth of the focus. Also, the nature of bedrock affects the magnitude.
- The Richter scale measures the earthquakes magnitude by recording the distance moved by the vibrating pen on a seismograph. The Richter scale is from level 0 and each number is 10 times stronger than the one before.
- Modified Mercalli Intensity (MMI) scale which also measures the seismic activity, where intensity of the earthquake is measured by observing the ground of the actual impact of the earthquake.
- The epicentre is the point on the earth's surface where the earthquake is first felt (straight above the focus)
- P Waves (primary): travel through solids/liquids.They are the fastest type of seismic wave
- S Waves (secondary): travel through solids but not liquids. Waves move the earth 90 degrees to the direction of travel. Cause a lot of damage due to their shearing effect.
Earthquake/ Multi hazardous case study
Tohku, Japan 11th March 2011
- Destructive boundary. OC vs OC. N American vs Pacific (subducting).
- Caused a lot of friction thus a lot of tension was released.
- Sea floor was lifted by 10m which caused the great tsunami waves.
- Magnitude 9 on Richter scale
- It was not predictable, but it was a frequent hazard as 150 earthquakes happen a year.
- S- 15,000 people died
- S- 3,000 people missing
- EC, P- Oil refinery exploded caused tank to explode bad for the economy
- S, EC, Env- The tsunami flooded 500 miles square and destroyed all in path
Earthquake/ Multi hazardous case study 2
- S- 150,000 people lived in temporary shelter, lost all possessions.
- S- 1,000,000 homes left without water and 6,000,000 lost electricity
- P- Nuclear disaster panic caused panic in government and in the global stock markets
- EC, S- Shortage of food, water and petrol
- Risk from drowning in the tsunami
- Risk of loosing families, homes and livelihoods
- Government can not afford to protect against tsunami as it is very costly and complex.
- Nuclear disaster could cause problems in global stock markets
- Risk of radiation poisoning in the ecosystems and into food chains- potentialy be destroyed
Earthquake/ Multi hazardous case study 3
Risk management to reduce the impacts:
- Mitigation- buildings being Retro fitting and having aseismic designs government supports this financially, when existing structures can be strengthened and made earthquake proof this improves the populations resilience. EG the textile factory was retro fitted with carbon fibre rods 9mm wide run over the roof and allow buildings to move in earthquakes.
- Buildings can be cross braced to reinforce the existing structure. Old buildings to remain part of the character in the city but is expensive.
- Adaptation- people living with constant hazard the warning system (where buoys in the pacific ocean detect shockwaves and send signals via satellites to Japan- this alerts the population to prepare themselves, also phone messages are sent)
- Rail ways, industry and power stations shut down immediately after first shock.
Wildfire- is given the generic name used for an uncontrolled rural fire.
- Crown- spreads across the surface, canopies and affects the top of forested areas
- Surface- burns across surface vegetation
- Ground- burns beneath ground layers of dry soil organic peat
Causes of fire
- Human factors- fires can be started by humans by discarded cigarettes, poorly controlled camps/BBQ.
- Natural factors- are from lightning strikes which can cause a spark which can end up in resulting in a forest fire.
- Local eco systems affected habitats destroyed, animals killed.
- Toxic ash can wash into rivers, adversely affecting aquatic ecosystems.
- Burning will release carbon dioxide stored in plants, trees and peat, thus increase the amount of C02 in the atmosphere, enhancing the greenhouse effect
Fire hazards 2
Wildfire- conditions favouring
- A ready supply of fuel (form of dry vegetation, ignition sources and favourable climatic weather).
- The type and amount of fuel influences intensity and rate of spread of the fire.
- The climate also has a impact as dry hot conditions like heatwaves and droughts creates favourable conditions for wildfires. Also, wildfires occur during or after prolonged dry periods (as vegetation becomes dry).
Fire hazards case study
Fort McMurray wild fire, Alberta, Canada 2016
- Fire released tonnes of carbon dioxide released into the atmosphere- Environmental
- Ash washed into the water which causes water pollution and contamination- Environmental
- 90,000 forced to flee Fort Mc Murray- Social
- 2,400 buildings burnt down- Social
- Destruction of businesses- Economic
- The fire has fueld a political debate about possible impacts of climate change and increased vulnerability of the future- Political
- Climate change- carbon cycle more c02 in the atmosphere- Environmental
- People may have to abide by new rules on fire safety regulations- Social
- Cost of rebuilding will cost a large amount- Economic
- Cost of future preparedness and other strategies- Economic
- Review strategies on preparedness and mitigation- Political
Fire hazards case study 2
- Began 1st May 2016
- A lack of snowfall and with warmer than average temperatures dried out the ground
- Prior temperatures over 30°C and winds increased. This caused wider spread of the fires
Short term responses:
- A mass evacuation program was implemented and some 90,000 residents were escorted to safety. Lack of deaths show how good evacuation was
- The Alberta government declared a state of emergency and this triggered support from the Canadian armed forces.
- Offers of help were received from USA, Australia & Russia
Long term responses:
- At the end of June 2016 a benefit concert 'Fire Aid' took place in Edmoton
- The Canadian prime minister promised long term aid to help support the re-building
- Canadian Red Cross had received donations in excess $50 million
Magma plumes- oceanic & oceanic
- Radioative decay in the inner core creates strong convection currents and the magma partially melts the crust to form a magma plume
- The magma plume in the oceanic ccrust moves vertically upwards and surfaces, this forms shield volcanoes and islands
- Chain islands are formed where the crust moves but the plume is staionary creating a chain of islands.
- Hawaii island chain, Pacific Ocean- Pacific plate
Magma plumes- Continental & Continental
- Radioactive decay releases immense amount of heat as a result very strong convetion currents are formed in the mantle
- Strong convetion currents forms at hotspots and will melt the crust and form huge plumes in the construuctive plate
- These huge plumes will form supervolcanoes and will errupt and lead to a collapse of the land forming huge caldereas
- Yellowstone, National Park, USA- N A plate
Nature of tropical storms –
- A tropical storm is a storm with high winds
- Known as cyclone, hurricane and typhoon
- Average wind speeds are in excess of 75
- Torrential rain and thunderstorms common
- Categories of tropical storm are measured by the Saffir-Simpson scale (magnitude) in km/h. The scale is from category 1 to 5
- Criticism of scale; Doesn’t show impacts of storm or size and scale of the storm
Frequency and magnitude of tropical storms
- Warmer atmosphere does mean more evaporation, therefore more storms, but winds are also changing which prevent storm formation
- Magnitude of a storm is measured by the Saffir Simpson scale
- Spatial distribution- 5’north and south of equator
Tropical storms 2
Causes of tropical storms
- Formed in the tropics, then move north or south- this is Earth redistributing heat from tropics towards poles = global atmospheric system
- Ocean temperature of more than 26°C – found near equator
- Warm air rising from oceans at equator (Hadley cell) for clouds to form
- Uniform wind direction at all heights
- Prevailing wind direction to push storm across ocean
- Storms will peter out on reaching land as moisture supply is cut off
Tropical storm predictability
- Predictability – kind of! As storms mostly restricted to tropics
- Occur mostly from late summer into autumn, with a peak from August to October
- Impossible to predict exact scale/magnitude of hurricane or exact locations of storms.
- NOAA publishes each year a prediction of hurricane activity using sea surface temperatures, atmospheric conditions
- Normal year is 4-8 hurricanes
Tropical storms 3
Formation of tropical storm:
- Intense heat around equator = evaporation of warm moist air over oceans, air rises over oceans= as air rises it contains huge amounts of moisture
- Uniform wind direction is present
- Warmer air rising is replaced by air drawn at the surface of the sea
- More & more air drawn in & a central vortex is created as air rises and spins = eye wall
- As air rises = it cools and leads to condensation & forms towering cumulonimbus clouds
- Condensation occur= heat is released & powers storm
- Continues to grow- driven by prevailing wind across oceans
- It moves over land = supply of energy & moisture is cut ff and storm will decay.
- Strong winds- 75mph+. Tear off roofs, break windows, damage communication networks
- Storm surges- Surge of high water up to 3 m, sweeps inland flooding low lying areas
- Coastal and river flooding- Flash flooding, particularly at coastal urban areas
- Landslides- Heavy rainfall from storm, so water infiltrates all pore spaces in soil
- Thunderstorms- Lightning strikes can create fires, destroy homes
Tropical storms case study
Hurricane Sandy, 2012
- Originated in the Caribbean Sea on 22 October 2012.
- Made landfall in Jamaica 2 days later.
- Hit the eastern seaboard of the USA early hours of the 29th of October with winds of 185km/h.
- Cat 4 Saffir Simpson scale
- Storm surges - waves reached up to 20ft.
- 4 days of heavy rain causing flooding (triggered landslides).
- Strong winds - Wind speed 94mph hitting the US.
Tropical storms case study 2
- Economic- Damage to infrastructure cost the US financial state up to $30 billion.
- Social- 117 US deaths.
- Damaged 200,000 homes.
- Environmental- 378,000 gallons of diesel oil spilled in surrounding creeks.
- Political- Affected the election campaign as it hit a week before the presidential election
- Mitigation- closure of schools, reinforced building materials, closure of trams and trains
- Preparedness- Suggested plans to protect coastal areas from future flooding
- Short term- Several thousand people evacuated from Manhattan in 6 days.
- Red Cross deployed 4,000 disaster workers providing food, water.
- National guard and US air force were put on alert ready to assist when the storm arrived
- Long term- Congress passed a $50.5 billion bill for construction in order to rebuild along the coast.
- Concert raised $20 million
Tropical storms contrasting case study
Tropical storm case study – Cyclone Winston, Fiji, 2016
- Category 5 on Saffir Simpson scale
- Wind speeds sustained = over 145 mph
- High winds
- Storm surges – south Vanua Levu
- Unpredictability of track
Tropical storms contrasting case study 2
- 40% of population affected
- 44 deaths
- 40,000 houses damaged or flattened
- Goverment building and hospital damaged
- No water supply
- Communications between islands lost for several days
- Cost US$1.4 billion
- 80% of population lost power
- 131,000 people homeless
Tropical storms contrasting case study 3
Short term responses
- Fiji red cross – gave out water
- Armed forces set up base to help people
- People living in tents- tent hospitals
- Fiji gov declared state of emergency
Long term responses
- Australia (FRANZ agreement) – $50 million aid, military - clearing rubble, buildings
- Fiji gov gave to families US$9 million to help with reconstruction
- China, India, S Korea,, EU, UN sent aid
- NGOs raised money – Red Cross, Oxfam
- Adaptation- Risk sharing as small commutes helped each other out
- Adaptation- Cyclone shelters
- Mitigation- Monitoring stations and forecasting system in place
- Mitigation- 700 cyclone shelters
- Mitigation- Fiji military on alert to help
Tropical storms contrasting
Fiji- Cyclone Winston 2016
- Life expectancy- 70yr
- GDP- $8,620
- 47 killed
- Communication between islands were lost- prevented further aid
- $9million was given
- Immediate help from New Zealand and Australia- military, food water
Tropical storms contrasting
USA- Hurricane Sandy 2012
- Life expectancy- 79yr
- GDP- $52,449
- 160 killed- due to high population density
- City on halt- subway, train and roads blocked
- $5o billion- more developed higher GDP and is a global power
- Federal government immediately helped- petrol
- American red cross 4000 volunteers
Earthquake hazards case study
Haiti, Earthquake, January 2010
- January 12 2010
- 7 mangnitud en richtoer scale
- Epicentre above capital- port au prince
- Conservative plate boundary- Carribian and N American plate
- 200,000 people dead
- 300,000 injured due to collapsed buildings
- 1.5 million left homeless
- Many died after due to poor sanitation and medication
- Lack of local food, water
- Unemployment rate skyrocketed as buisnesses were unable to recover
Earthquake hazards case study 2
Short term responses
- Freinds and neighbours helped each other out- no emergancy services available
- Aid sent but piled up at the airport
- 16,000 UN troops restored law and order and UN provided basic food
Long term responses
- $11.5 billion aid
- Tent ities- many people still living in these temporal accomadation
- Children startvin and homless sold to traffickers
- Poorest country in the western hempisphere
- 54% live in poverty
- frequently hit by eartquake and hurricanes
- The political instability led to development of Hati to be slow= prone to hazards
Earthquake/ Multi hazardous case study 4
- Arrived October 2017
- Hit Honshu Island
- High winds, storm surges, torrential rainfall, high winds 170kmph
- Category 2-4 storm on saffir simpsons scale
- 200,000 evacuated, 17 died
- Roads were blocked by floodwater making response difficult
- Econamy on halt with flights canceled
- Low lying lands flooded with salt water impacted agriculture
- Encouraing new buildings to be made of wood, using braved wood structure- Adaptations
- Resdents advised to shut windows and bring plant plots inside- projectiles- Adaptations
- Flood prevention as they consructed storage tank, collects flood water- Mitigation
- 40,000 people trained in disaster recovery and prevention- Mitigation