hazards Flashcards
define natural hazard
a perceived event that threatens people, the built environment and the natural environment. natural disaster only become hazards when a vulnerable population becomes exposed to it (deggs model)
how can you categorise hazards and examples
geophysical (land processes)- earthquakes, volcanic eruptions, landslides, tsunamis
atmospheric (climatic processes)- tropical storms, droughts extreme hot or cold weather, wildfires
hydrological (water processes)- floods, avalanches, storm surges
define disaster
hazardous event that caused unacceptably large numbers of fatalities and/or overwhelming property damage, UN defines as 10+ people being killed and 100+ people being affected
define risk
likelihood that humans will be affected by the hazard
define vulnerability
how susceptible a population is to the damage caused by a hazard
define hazard perception
how we view and process information about a hazard
factors affecting hazard perception
- wealth - richer people can have better provisions in place to not being badly affected
- religion- some people see hazards as being in God’s will
- education- more education means they have better understanding of the risks or hazards, and how to mitigate against
- past experience- people in hazard prone areas will know how to act
- personality- some fear hazards others may find them exciting and interesting
human responses to hazards
fatalism- view where people cannot influence the outcome and nothing can be done to mitigate against it
adaptation- attempts to live with the hazard and reduce their levels of vulnerability, like earthquake proof buildings
prediction- use last research to know the warnings of a hazard and help prevent major damage
prevention- ways of weakening the system as it approaches the land like seeding clouds
mitigation- strategies to lessen the severity of the hazard
risk sharing- pre arranged measured and public awareness to reduce the impacts on property and life, like through evacuation responses
what is parks model of human response to hazards and how can it vary
-describes a sequence of three phases following a hazard event
- model works as a control line and varying the steepness can show more catastrophic hazards with a slower response time
different stages of parks model
relief stage- immediate local response like food and medical services, immediate appeal for foreign aid
rehabilitation stage- services restore, temporary shelters food and water distributed
reconstruction stage- restore the area back to normal, rebuild new infrastructure
evaluation of parks model
+ useful to pinpoint the different kinds of response needed at different times
+ deepen understanding of responses
- does not take into account inequalities of development
- does not take into account varying capacity to response
- too general and not specific enough with the different magnitudes of hazards
- differences with climate change
stages of hazard management cycle
mitigation- minimise the impact of future disasters like building flood defences
preparedness- planning how to respond to a hazard like putting in warning systems
response- how people react when a disaster occurs like emergency services
recovery- getting the affected area back to normal
characterises of a hazard
- frequency- distribution of a hazard through time
- distribution- spatial coverage of a hazard
- magnitude- size of a hazard
- intensity- power of a hazard
features of inner core
- solid ball of iron and nickel
- very hot due to pressure and radioactive decay
- 6000C
features of outer core
- iron nickel
- less pressure so the metal can melt and it is semi molten
features of mantle
- thickest layer (2900 km)
- mainly solid rock
- very top layer is semi molten magma known as asthenosphere
- lithosphere is between mantle and crust and is where tectonic plates lie
features of continental crust
- 30-70km thick
- light so doesn’t sink
- known as SIAL due to larger amounts of silica and aluminium
- not created or destroyed
features of oceanic crust
- 5-10 km thick
- made of basalt
- constantly being destroyed and replaced
- heavy and dense so sinks below continental crust
- known as SIMA as it made of silica and magnesium
what did wegener suggest about how the continents once were
used to he one giant continent called pangea, which split into the continents we have today
geological evidence for plate tectonic theory
- continents vaguely fit together
- evidence of similar ancient glacial deposits in south america, antarctic and india
- similar rock type and structures along northern scotland and eastern canada
biological evidence for plate tectonic theory
- fossils found in india are comparable to those in australia
- fossil remains of mesosaurus found in southern africa and eastern south america
- identical plant fossils found in coal deposits in india and antarctica
what is palaeomagnetism
- discovery that earths polarity reverses on either side of the mid-atlantic ridge at regular intervals
- oceanic crust got older with distance from the middle of the ridge, and was mirrored on both sides
what is sea floor spreading and explain the process
- tectonic plates diverge and magma rises up to fill the gap, and cools to form new crust
- over time the new crust is dragged apart so more crust can form, as the sea floor gets wider
- however, crust is being destroyed elsewhere accommodate for new crust forming, and acts in a constant cycle
how can plates move
- convection currents
- ridge push or gravitational sliding
- slab pull
explain convection currents
- heat from earths inner and outer core heats the mantle, which rises upwards
- this cools and as it falls it drags the lithospheric plate with it
explain ridge push or gravitational sliding
- magma wells up and forms an ocean ridge above the ocean floor, which gets older and cools and condenses
- gravity pushes down the older lithosphere as new crust forms on top causing it to slide away from the ridge
explain slab pull
- older, colder plates sink at subduction zones and pulse the rest of the warmer plate along with it via gravity
- major driving force for most plate movement
how do constructive plate margins move apart
- pressure is released and causes the mantle to melt with produces magma
- when the pressure builds up too much, the plate cracks and makes a fault line
- transform faults are perpendicular to the ridge and divide the plate into sections to which they move
ocean ridge features
- in oceanic plates
- mid- atlantic ridge- where eurasian plate and north american plate are moving apart
- magma rises in between the gap left by plates separating and forms new land as it cools
- new land forming is also called sea floor spreading
rift valley features
- on continental plates
- plates diverge beneath land, where rising magma causes continental crust too bulge and dome
- as the plate is pulled apart, the crust between the faults sink
- east african rift valley
oceanic and continental plates destructive margin
- more dense oceanic crust is subducted under the continental crust, forming a sea trench
- fold mountains form when continental crust is deformed by folding and then forced upwards
- oceanic crust is heated and me,ted by friction into the subduction/ benioff zone
- magma can then be pushed up to create volcanoes
- as one plate moves, the friction causes pressure to build up and cause an earthquake
oceanic and oceanic plates destructive margin
- more dense oceanic crust subducts
- island arc (cluster of islands in a curved line) can appear when volcanic eruptions take place underwater, as the subducted plate melts and rises to the surface as magma
continental and continental plate destructive margin (collision boundary)
- neither is subducted so there aren’t any volcanoes but pressure can build for earthquakes
- fold mountains form like Himalayas
what are conservative plate margins
- parallel plates moving in different directions or at different speeds
- pressure can build up from the friction and cause earthquakes
what are magma plumes or hotspots
- hot magma plumes from the mantle rise and burn through weaker parts of the crust
- can create volcanoes and islands
- when plates move, it can take volcanoes with it and over millions of years a chain of islands can form
- oldest volcanoes move further away from hotspot
- hawaiian hot spot has been active for around 70 million years and created 6000 km chain of volcanic islands
features of volcanoes at constructive plate margins
- magma reaches surface quickly
- runny basaltic lava with low silica content
- can flow a long way before it hardens
- gentle sloping volcanoes- shield
- gentle but frequent eruptions
- low VEI
- icelandic/hawaiian eruptions
features of volcanoes at destructive plate margins
- rocky andesite lava with high silica content
- steep sided- stratovolcano or composite
- violent eruptions
- high VEI
- plinian/ pelean eruptions
features of volcanoes at hot spots
- low viscosity, basaltic lava
- low angled slopes
- lava flows great distance from volcanic vent
define active volcano
erupted in living memory
define dormant volcano
erupted within historic record
define extinct volcano
will not erupt again
features of fissure and shield volcanos
- low slopes and is associated with conservative plate margins with runny lava
- ash
- lava runs quickly downhill and over a large distance
- lava escaped through more than one vent
- gentle eruptions
features of ash cinder or composite volcano
- composed of tephra and happen at destructive plate margins with viscous lava
- pyroclastic flows, bombs
- violent eruptions
- narrow base due to slow moving lava
factors affecting the viscosity of lava
temperature- higher the temperature, runnier it is
silica content- higher silica content leads to thicker magma
volume of dissolved gases- higher the dissolved gases the more runny magma
primary volcanic hazards
tephra
pyroclastic flow/ nueés ardentes
volcanic gases
lava flow
ash
secondary volcanic hazards
lahars
flooding
volcanic landslides
tsunamis
acid rain
climate change
features of tephra
- solid material ejected from volcanoes
- endanger aviation and infrastructure
features of pyroclastic flow
- very hot mixture of gas and tephra moving at high speeds
- deadly
- destroys everything in its path
- can lead to secondary hazards like flooding and lahars
features of volcanic gases
- carbon dioxide, carbon monoxide, sulphur dioxide
- annually release 180-440 million tonnes of co2
features of lava flow
- flowing lava normally destroying crops
- speed and distance travelled depend on temperature and viscosity
features of ash
- fine material ejected from a volcano which can spread over large areas and smother crops
- can stay in atmosphere for a long time
- can affect health
- can cover vegetation, which stops photosynthesis
- alter composition of water systems and aquatic environments
features of lahars (mudflow)
- unconsolidated ash combined with water and swept down river valleys
- hot ash melts ice and it flows down valley
- can grow in size as it accumulated material
- speed can exceed 120 mph
- formed when long duration rainfall occurs during or after eruption
- steep slopes mean rainwater can move and erode faster
features of flooding
- eruptions can melt glaciers and ice caps
features of volcanic landslides
- large masses of wet or dry rock and soil
- common on volcanoes as they are steep and weak rocks
features of tsunamis
- waves generated by violent eruptions
features of acid rain
- sulphur mixed with atmospheric moisture
features of climate change (volcanic hazard)
- huge amounts of volcanic debris can reduce global temperatures
- sulphur dioxide leads to global cooling
Nevada del Ruiz volcanic eruption
- columbia 1985
- destructive plate margin
- lahars
- 22,000 dead
mount pinatubo volcanic eruption
- 1991 philippines
- destructive plate margin
- pyroclastic flows, ash, lahars
- 800 dead
- good management, people evacuated so were not as affected by pyroclastic flows
- typhoon yunga after was unpredictable and led to lahars
characteristics of volcanic hazards
- spatial distribution- constructive, destructive, plate margin
- magnitude- measures using volcanic explosively index (VEI) from 0-8
- frequency- active, dormant, extinct
- regularity- can be regular as eruptions on each boundary are similar
- predictability- regularity can help predict when they take place, as well as seismic activity gases releasing and elevation
main facts of eyjafjallajokull eruption
- VE4
- ash and jokulhlsup (glacier flood) were the main hazards
- constructive plate margin and hotspot
- hydro-meteorological events as well as jet streams meant areas of europe were covered in ash
positive impacts of eyja eruption
+ tourism benefit- end of march 10,000 visited eruption
+ trains like Eurostar benefit as no planes were flying
+ nutrition of ash allowed for some good harvest in parts of iceland
negative impacts of eyja eruption
- acidic tephra caused arable land to be infertile
- 25% increase in respiratory illness
- £2 billion cost to businesses
- medical operations cancelled like organ donors
- Kenya- flowers and vegetables were wasted which estimated to cost £2.4 million a year
- flooding- meltwater, 800 local people evacuated
- national debt and recession over next 3 years
management of eyja eruption
- no fly zone- 17,000 flights cancelled
- tourists stranded
- monitoring meant people could evacuate
- project FutureVolc- international project which aims to improve sensors and gas detection metres for future eruptions
social impacts of volcanic eruptions
- deaths
- buildings and infrastructure destroyed
- hazards can start fires
- mudflows and flooding
environmental impacts of volcanic eruptions
- ecosystems can be destroyed
- acid rain can ruin buildings
- volcanic gases contribute to global warming
economic impacts of volcanic eruptions
- disrupt businesses
- damaged buildings which are expensive to repair
- can also attract tourists
political impacts of volcanic eruptions
- food shortages
- government have to spend money on reparation
prevention of volcanic eruptions
not possible
preparedness of volcanic eruptions
- monitoring systems to predict when an eruption may occur- release of gases, bulging of land
- can stop people entering hazardous areas
- individuals can be prepared with kits
mitigation of volcanic hazards
- risk assessments
- can divert lava from the built environment
- evacuating people
adaptation of volcanic eruptions
- buildings can be strengthened to reduce chance of collapsing
- people can capitalise in opportunities around the volcano like farming or tourism
- move away from risk areas
what is the focus
where the earthquake originates from in the crust
define epicentre
the point on the surface above the focus
characteristics of seismic hazards
spatial distribution- all plate margins up the most powerful are at destructive margins, can also be when old faults are reactivated like dam or mining
magnitude- measured using logarithmic richter scale, moment magnitude scale is more accurate and identifies energy release, mercalli scale is subjective and qualitative
- frequency- occur every day but may not be strong enough to cause destruction
- random
- impossible to predict- can look at microquakes
features of earthquakes at constructive margins
- deep foci
- powerful earthquakes
- tsunamis
features of earthquakes at conservative margin
- shallow
- intense
- strike-slip fault- side to side movement
features of earthquakes at collision margins
- continental crust
- colliding plates can lead to friction when folding
- shallow
examples of primary seismic hazards
- ground shaking- plated jerk past each other and sends out shockwaves
- ground rupture- visible breaking and displacement of earths surface
examples of secondary seismic hazards
- soil liquefaction
- landslides/avalanches
- tsunamis
- fires
explain soil liquefaction
- soils violently shaken with high water content lose their mechanical strength and behave like a fluid
- importance of geology- most significant in sandy soils
- soft sediments means the particles, due to shaking, get forced upwards and acts as a liquid
explain landslides
- shaking can dislodge rock
- can also mean water infiltrated easier, and the weight triggers a landslide
explain tsunamis
- occurs in countries around pacific ring of fire
- large amount of water displaced leads to tsunamis- at destructive plate margins
- boxing day earthquake 2004, 300,000 died via the tsunami to neighbouring countries
- long wavelength in deep water but when bathymetry changes, amplitude increases and wavelength decreases
social impacts of seismic events
- buildings can collapse- killing and injuring people
- power lines can break
- lack of clean water
economic impacts of seismic events
- destroy businesses
- damage industry
environmental impacts of seismic events
- damage to industrial units can lead to leaks of chemicals or radioactive chemical
- fires can destroy ecosystems
- tsunamis can flood freshwater sources
political impacts of seismic events
- shortages of food and resources
- reliant on loans and aid to repair
prevention of seismic hazards
- it possible
- liquefaction can be prevented through soil stabilisation
prediction of seismic hazards
- very difficult
- can roughly know whereabouts and impacts
preparedness of seismic hazards
- education and evacuation routes
- emergency kits
- warning systems
- tsunami protection- seismographs can detect earthquakes and signal areas in pacific ocean
mitigation of seismic hazards
- moving away from risk areas
- earthquake prone buildings- shock absorbers, base isolation devices which detach building from the ground
background of haiti earthquake 2010
- richter 7
- strike slip fault- fault lines moves horizontally
- shallow rock- 13km down
- 33 aftershocks
- amplification- seismic waves pass through large sediment and intensify, city built on soft sedimentary rock
- 3/4 of Haitians live on less than $2 a day
impacts of haitian earthquake
- 220,000 dead
- 80% of port-au-prince was destroyed including the presidential prince
- 250,000 residential buildings destroyed
- lack of robust steel rods in houses so they collapsed
response to haiti earthquake
- international red cross says 3 million people affected
- britons donated £23 million
- dominican republic first to give aid- water, food
characteristics of storm hazards
- spatial distribution- between the tropics (USA, Mexico, south east africa, australia, india)
- magnitude- saffir simpson scale is used to measure storm magnitude, category 5 is the strongest
- frequency- very frequent but some never reach land so are not major hazard
- can be predicted using satellite imagery to formation of clouds and the tropical storm
- irregular
conditions for development of tropical storms
- sea temperatures over 27C
- ocean depth of at least 70m to provide latent heat
- location of at least 5 degrees north or south of the equator for coriolis effect
- low wind shear- winds moving in different directions
- disturbance near the sea surface
- convergence of air in the lower atmosphere as there is unstable air pressure
formation of tropical storms
- warm moist air rises leaving an area of low pressure below (warm air from surrounding areas of higher pressure move into this low pressure area)
- when warm air rises, it cools adiabatically and condenses into thunderstorm clouds
- whole systems spins due to coriolis effect
- constant additions of energy from the condensation of warm air causes the storm to spin faster
- an eye can develop which is an area of low pressure, calm conditions in the middle of the storm
- when it reaches land, it loses energy and collapses
what is the impact of climate change on tropical storms
- number of TS has decreased
- greater proportion of very strong TS due to increase in air temperature leading to enhanced uplift
- less difference in atmospheric pressure between poles and the tropics so speed of winds decrease which produces more rainfall
TS hazards
- winds that exceed 74mph, leading to structural damage
- heavy rainfall between 200-300mm
- storm surges
- high seas of up to 15m high
- tornadoes
- flooding
- landslides
social impacts of storm events
- people may drown or get injured by debris
- houses are destroyed
- lack of clean water and food supplies
political impacts of storm events
- political unrest
- expensive repair
economic impacts of storm events
- expensive to repair
- businesses are damaged
environmental impacts of storm events
- beaches are eroded and coastal habitats destroyed
- environments are polluted- water, oil and chemical spillages
prevention and prediction of storm events
- cannot be prevented
- national hurricane centre in florida can look at geostationary satellites
preparedness of storm events
- emergency kits
- evacuations routes
- educate people
adaptation of storm events
- reinforced concrete
- fixed roofs securely
- securing furniture
- buildings can be on stilts to withstand flooding
mitigation of storm events
- move away from high risk areas
impacts of hurricane katrina
- 1,800 people died
- $108 billion in damages
- 80% of New Orleans was flooded
- 25-35% of households had no access to a vehicle to escape
- mainly Black people marginalised
- 230,000 jobs lost from damaged businesses
- coastal habitats destroyed- sea turtle breeding beaches, breton national wildlife refuge in Louisiana
details of hurricane katrina
- 2005
- category 5
- USA, mainly New Orleans hit
short term responses of hurricane katrina
- mandatory evacuation- however 150,000bstayed
- superdome used as shelter with food and water
- 5,000 members of the national guard were mobilised to help
-$1.8 billion raised for the red cross - Fema “blue roof” scheme for 81,000 properties for temporary roofs
- US army removed 30 million cubic metres of rubble
long term responses for hurricane katrina
NOAA has 8 new buoys and improved satellite imagery
features of typhoon haiyan
- 2013
- category 5
- winds over 350km/hr
risk and vulnerability of typhoon haiyan
- tacloban lies in the centre of Philippines where tropical storms cross
- people move to Tacloban for employment opportunities- high population density
- poorly constructed houses
- $2,765 GDP
impacts of typhoon haiyan
- 300mm of rainfall
- storm surge of up to 6m
- 6,000 fatalities
- 90% of Tacloban was damaged
- 2 million people were homeless
- large areas cut off with communication
- Tacloban airport destroyed
- $2.9 billion in damages
short term responses of typhoon haiyan
- UK deployed 2 navy ships with 200,000 tonnes of aid
- indoor stadium used to house people
- WHO- tried to minimise risk of cholera and other diseases
- DEC announces international fundraising
- lots of looting and violence- hard for aid to reach places
long term responses of typhoon haiyan
- “build back better”- build stronger homes, local community gardens
- no build zone along Eastern Visayas zone
- new storm surge warning system
- mangrove plantations
features of mount mayon volcanic event
- 2018
- level 3 alert
- main hazard was ash
risk and vulnerability of mount mayon
- large ash emissions generally settle within a few km, and can affect nearby city of Legaspi
- ash emissions can settle in the gullies in the flanks of the volcano- high rainfall means there is high risk of lahars
- nuees ardennes are concentrated in the gullies
- lava flows can destroy local agriculture
impacts of mount mayon
- no deaths
- $3.4 million in damages to agriculture- rice and corn
responses to mount mayon
- 40,000 residents were evacuated from the 6km radius
- filipino government committed $1 million for a “cash for work” programme to provide 50,000 hygiene packages
- army was called to help
- USAID committed over $100,000
define wildfires
a large uncontrolled fire that spreads quickly between vegetation
spatial distribution of wildfires
- western US, australia, southern europe
- savanna or mediterranean climate
conditions favouring intense wildfires
- thick vegetation, like monocultures, that are densely together
- thick vegetation causes fire to burn longer and more intensely
- dry vegetation with little moisture
- enough rainfall for vegetation, but dry spells to dry out fuel
- windy areas also cause fires to spread quicker
- ignition needed
- gradient- slowly downhill or quickly uphill as hot air pre warms vegetation
natural causes of wildfires
- cycles of rainfall, dryness and lightning
- movement of ITCZ across Africa that bring wet season, otherwise dry season allows for fires
- el niño and la niña
- southern ocean dipole
- volcanic activity
human causes of wildfires
- slash and run
- fireworks
- cigarettes
- arson
types of fires
- ground fire- ground itself burns which is slow with no flame and little smoke
- surface fire- leaf litter and low lying vegetation burn
- crown fire- fire moves rapidly through the canopy and more likely to be intense and fast moving
effect of climate change on wildfires
increasing temperatures has increased number of wildfires and increased length of
socioeconomic impacts of wildfires
- deaths
- damage to buildings
- damage to crops and businesses
environmental impacts of wildfires
- loss of crops and wildlife
- damage to soil structure and nutrient content
- release of toxic gases and particulates
- water pollution
positive impacts of wildfires
- clear away dead underbrush
- fire returns nutrients into the ground
- rid areas of insects and parasites
- can stimulate secondary succession- plants grow quicker
preparedness of wildfires
- education- fire warning system, evacuation routes, emergency kit
- community action- identify vulnerable areas, help develop survival strategies
- computer modelling- predict fire behaviour
mitigation and adaptation of wildfires
- fire resistant landscaping
- home ignition zone
- landscape with pyrophytic plants
- fire breaks (gaps in trees) to reduce spread
- removing overhand and shrubs within close proximity of property
prevention of wildfires
- education
- managing vegetation
management of wildfires as it is happening
- retardants to slow pace of fire
- spraying with water and chemicals
factors that increase Japans vulnerablity
- on a destructive plate margin- high VEI, violent earthquakes
- near pacific ocean- strongest typhoons as it is biggest
- mountainous- leads to higher population density
- elderly population- unlikely to leave
- national pride- people are unlikely to leave or loot to live
- temperate climate and in the summer there are typhoons
factors that decrease japans vulnerability
- rich- an build earthquake prone buildings, efficient responses
- volcanoes are infrequent
- many earthquakes are offshore
- aid
- strict building code
- multi hazard warning system
- japans trench dissipate wave energy
what is the indian ocean dipole
- positive- temp in indian ocean is warmer and move West, leading to lower pressure in East Africa and droughts in Australia
- negative- westerly winds move East so lower prepare in Australia instead of
what is south annular mode
- westerly winds by the southern sub tropics
- movement N and S can affect weather patterns
- SAM can shift North- causing heavy rain in S Australia (negative SAM)
explain el niño and la niña
- normal conditions- trade winds blow towards the warm water in the west and keeps it warm by Australia, which leads to low air pressure as it rises
- el niño- winds weaken and mass of warm water migrates back to South America and Australia experience high air pressure
- la niña- conditions return back to normal but very extreme so there is extreme wet in the west and extreme dry in the east
cause of black summer
- exceptionally high level of dryness
- SAM fanned wildfire making firefighting difficult
- extreme positive IOD
- 91,000 lighting in strikes on christmas 2019 in Darwin
impacts of black summer
- more than 20% of forests burned
- 5,900 buildings destroyed
- 34 people killed
- 1 billion animals were killed
- $70 billion damages
- kangaroo island- 1/3 is protected by nature reserves but more than 1/2 was destroyed
responses to black summer
- australians defence force- air support and man power
- firefighters and equipment from canada, new zealand, US
- new homes built came with defendable space
typhoon hazards in japan
- typhoon season between july and october
- 25 typhoons in pacific ocean each year
features of 2011 tohoku earthquake
- richter 9
- mega thrust earthquake
- occurred in NE japan
- shaking extended to tokyo, which experienced richter 7 but all buildings stayed up and no deaths
- destruction came from tsunami
impacts of tohoku earthquake and tsunami
- fukushima nuclear disaster- equipment failures, explosions
- 20,000 deaths from tsunami
- waves up to 10m
-$100-235 billion in damages - 60+ years accounted for 65% of deaths
- 452,000 in evacuation facilities- huge numbers suffered hypothermia
- tsunami reached california, causing road and ferry closures in San Francisco
how prepared is japan for hazards
- warning system- gold standard
- detection buoys detected tsunami, but it was moving too fast
