Hazards Flashcards
What is a natural hazard?
Extreme event which happens because of nature + may cause harm to humans
Element of human involvement -> X humans = X hazard
What is a natural disaster?
A hazardous event that causes large number of fatalities/property damage
What are the 3 types of hazards?
Geophysical = earths internal/external processes e.g. earthquakes
Atmospheric = processes in atmosphere e.g. droughts
Hydrological = water bodies + its processes
What is vulnerability?
High risk + an inability of individuals + communities to cope, making them more likely to be harmed/effected
What are the 6 responses to a hazard?
- Fatalism = choose to do little, belief in ‘God’s will’, > in developing countries
- Prediction = predicting to prepare for impact, not all can be, > in developed countries
- Adaptation = places experiencing regular hazards, adapt to cope better, cost-effective, > in developed countries
- Mitigation = reduce long-term risk to life/property- preparation to limit impact
- Management = identifying possible risks + allocating resources
- Risk sharing = UNs International Strategy for Disaster Reduction (ISDR) - national + international responsibilities in disaster preparation
What are primary impacts?
Have immediate effect on area experiencing disaster e.g. deaths, destruction of infrastructure
What are secondary impacts?
Occur after the disaster has occurred e.g. disease from contaminated water
4 stages of the Hazard Management Cycle
Preparedness - (Event) - Response - Recovery - Mitigation
Stages of the Park Model
Normal life, disaster, relief, rehabilitation, reconstruction
Process of convection currents
-Mantle hottest closest to core
-Lower part of asthenosphere heats up
-Becomes < dense + rises
-Cools down, becomes > dense + sinks
-Circular movements = convection currents
Evidence for continental drift
-Apparent fit of the continents
-Fossil correlation- Mesosaurus along East coast of S.America and West coast of Africa
-Geology- rock + mountain correlation- same age + type of either side of continents
-Past climate data e.g. glacial evidence has been found in warm regions
What are the 3 sections of the earth and the temperature of the furthest in section?
Crust, mantle, core
The temperature of the core is 5500 degrees celsius
What is slab pull?
Destructive plate margins
Denser crust forced under less dense
Sinking of plate edge pulls rest of plate towards the boundary
What is ridge push?
Constructive plate margins
Magma rises to surface + forms new crust
Magma heats surrounding rocks which expand + rise above surface of surrounding crust, forming a slope
New crust cools + becomes denser
By gravity it moves downslope away from plate margins (gravitational sliding)
Puts pressure on tectonic plates, causing them to move apart
What is paleo magnetism?
When new rock is formed at constructive boundaries it aligns to magnetic north creating magnetic stripes that increase in age from the boundary to the edge of the plate
Oceanic-oceanic destructive margins
Denser plate subducted- moving towards each other
Hazards found = violent earthquakes (from pressure release), volcanoes- above less dense crust, subducted plate melts, bursts through less dense crust
Landforms created = ocean trenches (subduction -> gap created when land drops down), island arcs (descending plate melts, rises as magma, volcanoes, eruptions at sea lead to island arcs- volcanoes line up next to boundary)
Example = Pacific Plate + Philippine Sea Plate- location of Mariana Trench
Continental-continental destructive margins
-Both plates < dense than asthenosphere- no subduction
-Hazards = shallow focus earthquakes, no volcanic activity
-Landforms = no subduction -> colliding plates become uplifted + buckle to form fold mountains
-Example = Indian plate + Eurasian plate -> Himalayas
Oceanic-Continental destructive margins
-Plates moving towards
-Hazards = volcanoes above continental (oceanic melts, bursts through crust -> violent volcanoes), violent earthquakes
-Landforms = fold mountains (continental crust gets bunched up, mountains become twisted), ocean trenches (oceanic subducted + pulled downwards, gap where land sharply drops)
-Example = Nazca Plate + South American Plate- Andes
Oceanic-Oceanic constructive margins
-Plates moving away
-Hazards = volcanoes (mantle melts, magma, rises + erupts), earthquakes (some parts move faster than others, pressure builds up, plate cracks -> earthquakes)
-Landforms = mid-ocean ridges (magma rises, calmer volcanoes, submarine mountain ranges), ocean ridges (space between plates fill with lava, forms ridges, can be volcanoes here)
-Example = Mid Atlantic Ridge
Continental-Continental constructive margins
-Plates moving away
-Gap > over time, bigger + deeper, land between forms small, narrow sea e.g. Red Sea
-Hazards = can be volcanoes along rift valleys (not destructive)
-Landforms = rift valleys (plates apart, crust fractures + sections drop to form the valley)
-Example = East African Rift Valley
Conservative plate margins
-Plates moving past each other
-Can be opposite directions or same direction at different speeds
-Hazards = earthquakes (violent release of pressure), no volcanoes/new land as no subduction/magma rising
-Example = San Andreas Fault, California
What is a magma plume and how do they form island chains?
Magma plume = vertical column of extra-hot magma that rises up from the mantle
Remains stationary within mantle, crust moves -> volcano loses its source
New volcano created over hotspot
Process continues -> volcanic island chain
What is the volcanic explosivity index (VEI)?
-relative
-measures amount ejected -> uses qualitative observations to determine explosivity value
-scale doesn’t have an end but anything above 6 = extremely destructive/dangerous
What is viscosity?
How thick/resistant a liquid is
How does silica content affect the lava?
> amount of silica, more sticky + explosive it will be
What is an extinct volcano?
Not erupted for 10,000 years and is not expected to again
What is an active volcano?
Volcano which has had an eruption in the past 10,000 years + is expected to again
What is a dormant volcano?
Not currently active but is expected to erupt again
Location of Montserrat
British Overseas Territory
In Caribbean
Surrounded by Caribbean sea
Why is Montserrat at high risk from tectonic activity?
Part of island arc
Formed from subduction of the South American plate under the Caribbean plate
Therefore = volcanic island formed from multiple eruptions
Key facts about the Montserrat eruption
Pyroclastic flows reached 600 degrees celsius + 120km/h
Violent eruptions- rhyolitic lava + pyroclastic flows
Main explosion was 2 years after the 1st eruption
Impacts of the Montserrat eruption
-Islands airport was destroyed by being in the path of the pyroclastic flow
-2/3 of all houses were buried by ash/flattened by rocks
-South of the island was covered by pyroclastic flows, including ash, lahars + rocks- ended up being an exclusion zone
-People had to abandon homes + businesses
-19 killed
-100s left homeless
-Pyroclastic flows caused associated fires + also caused burns + inhalation injuries
-Many chose to evacuate- became ghost island
Responses to the Montserrat eruption
-Setting up Montserrat volcano observatory in 1995- predicted the 1997 eruption
-NGOs provided aid
-Rebuilt the tourism industry- used volcano as an attraction
-People on Montserrat granted full residency rights in the UK- could choose to migrate
-Making the south, including the former capital Plymouth, an exclusion zone
How do earthquakes happen?
-Plates can’t move past each other easily
-Two plates become locked -> friction -> pressure builds up
-Pressure released -> seismic waves
What is the epicentre of an earthquake?
Point directly above the focus on the Earths surface
What is the focus of an earthquake?
Point at which rock moves- seismic waves start here
Deep focus = greater magnitude- but do less damage because energy is further dissipated
What are the 4 types of seismic waves?
Body waves:
-Primary waves = move backwards + forwards
-Secondary waves = move vertically/horizontally
Surface waves:
-Love waves
-Rayleigh waves
Earthquakes at constructive boundaries
Shallower + less powerful
Occur on mid-ocean ridges - away from land
Earthquakes at conservative plate boundaries
Shallow focus
Compressional forces high- continental plates drag past each other
Very powerful- severe damage in dense populated areas
Earthquakes at destructive plate boundaries
-tend to be at depth
-compressional forces at greater- subduction one crust in narrow area
-very powerful
-can take place under sea- tsunami threat
Richter scale
Logarithmic
1-10
Each increase, 30x more energy
Accuracy decreases for larger earthquakes
Moment magnitude scale
Total distance fault has moved + force needed to generate it
Now used worldwide
Mercalli scale
12 point scale
Effect on people + infrastructure
Severity on humans rather than objective measurement
Qualitative
How can human activity lead to earthquakes?
-Mining = highest number of human-induced earthquakes worldwide - removal of material -> instability -> collapse
-Dam building
-Fracking. - disposing of wastewater used in the process -> high pressure -> cracks rocks
Human + physical factors which increase the impact of earthquakes
Human:
-population density
-level of development
-prediction
-earthquake proofing
-education + politics
-wealth
Physical:
-location of epicentre
-time of day
-geology
-depth of focus
-plate boundary
What are the 3 secondary seismic hazards?
- Soil liquefaction
- Tsunamis
- Landslides + avalanches
Japan earthquake 2011 causes + key facts
-Japan located at junction between 4 major plates
-Magnitude of 9 = biggest ever recorded
-Depth of 30km
-Preceded by large foreshocks over previous 2 days
-shaking lasted over 3 minutes
Primary + secondary impacts of 2011 Tohoku earthquake
Primary:
-16000 killed, 6000 injured
-shifted Earth on axis by 10cm
-limited damage in Sendai + Tokyo- earthquake proofing
-127000 buildings destroyed + 1 million damaged in northeast Japan
-4.4 million households left without electricity + 1.5 million without water
-only 4 trains derailed
Secondary:
-1800 houses destroyed when Fujinuma dam failed
-tsunami waves after 20 minutes - travelled 10km inland in Sendai
-nuclear meltdown in 3 reactors
-ice calved from Sulzberger ice shelf
-cost > $300 billion - most expensive natural disaster in history
Responses of 2011 Tohoku earthquake
-116 countries + 28 international organisations
-military had to bury in mass graves
-declared state of emergency
-55 nuclear reactors taken offline -> rolling power blackouts common for weeks
-food exports restricted (radiation fears)
What is a tropical storm?
Huge low pressure storm which develops within the tropics
Powerful
Cause devastation to small islands + coastal regions
Components for a tropical storm to form
-ocean temp > 27 degrees (therefore mostly occur in summer/autumn)
-ocean depths > 70m
-high heat -> violent updrafts of air
-high levels of humidity
-trade winds (major winds all blowing in same direction)
-between 5-15 degrees N+S of Equator- needs spin from Coriolis effect
Saffir-Simpson Scale
-Measures tropical storm
-Wind speed + give estimate on how much damage a storm will cause
-Category 5 = strongest, catastrophic damage
-Category 1 = weakest, limited magnitude of damage
What are the 3 hazards in tropical storms?
-Heavy rainfall
-High winds
-Storm surges
Physical + human causes of Hurriance Katrina
Physical
-low lying land = 51% New Orleans at/below sea level
-storm surges = warm waters nearby intensify
Human
-high population density - 485k in New Orleans
-failure of levees
-loss of wetlands- used to provide natural barrier
-delayed implementation of rescue plans
Consequences of 2005 Hurricane Katrina
-1800 died
-value of property damage = $161 billion
-4 years later - 1000s displaced residents still living in trailers
-Head of FEMA resigned
-led to looting in New Orleans
-2015 = population of Lower Ninth Ward <40% pre-storm level
-residents in Lower Ninth Ward = held pessimistic views about recovery of the community
Cyclone Nargis key facts
-May 2008
-in monsoon region of Asia
-next to Bay of Bengal - warm and moist air
-had limited mitigation + organisation after the event -> more deaths
-nearly 2 million people along coastline living on land < 5m above sea level
What is a wildfire?
Distinguished from other forms of fire event by being beyond control for an initial period of time in a natural environment.
Known as ‘quasi-natural’ wildfires = created by human + natural factors
the fire triangle- 3 conditions that need to be present for a wildfire
- fuel
- oxygen
- a heat source
-all 3 must be present for fire to continue
Distribution of wildfires
-Large forested areas
-warm climates e.g. California
-rural hazard
-can occur in most environments
-areas with distinct dry seasons e.g. Mediterranean
3 types of wildfires
Ground fires = burns beneath ground in layers of dry organic peat, 540 degrees, smoulder, burn for longer periods
Surface fires = across surface vegetation, dry conditions, 900 degrees, easiest to control
Crown fires = spreads across tree canopies + forested areas, 1100 degrees, quick + intense, little control, worse on steep slopes
What are spot fires?
Winds blow ‘fire brands’ away from crown fires onto new areas, like fireballs- fly from burning treetops to other new places -> spreads new fires
What are conflagarations?
Large, destructive fires
Distribution of wildfires
Occur in large forested areas, mostly in warm climates such as California
Can occur in most environments
Expansion of towns/cities mean they’re now closer to human occupation
Dry vegetation is most susceptible to natural wildfires from lightning strikes
Distinct dry seasons, such as in Mediterranean makes them high risk
How does humidity and temperature affect the risk and severity of wildfires?
Humidity = > 15%- wildfire risk = low, < 7% risk is much >
Temperature = higher temps mean absorb moisture from fuels -> can catch fire as more dry
How can wind and topography affect wildfires?
Wind = change direction of fire, provide fresh supply of oxygen
Topography = fires move faster uphill, steeper slope = faster burning (as more fuels in close proximity)
How do times and seasons affect wildfires?
USA = summer has > fires, heat makes fuels drier + provides richer oxygen
West Africa = Harmattan Winds (Nov - March), blow from Sahara desert + make fires burn more
What happened in the California wildfires?
> 9,000 wildfires in last months of 2017 -> 1.2 million acres of land, killed 46, destroying around 11,000 structures
2 major outbreaks -> October event know as Northern California firestorm where 21 of these fires became major fires
How were the California wildfires caused?
at least 12 of Northern fires caused by electric power + distribution lines
Exacerbated by strong Santa Ana winds
Factors which increased risk in California wildfires
-Little precipitation from May 2017 onward- autumn precipitation was substantially delayed- Sep-Dec precipitation = exceptionally low
-Population growth placed more people in the way of fires (building on the wildland-urban interface- 3.6 million properties situated here)
-2017 = longest duration of Santa Ana winds for > 70 years- brings warm + dry air (low humidity)
-Policy = fewer control burns as policy is to just suppress all fires -> poses > risk when fires occur (constrained in ability to prevent fires)
-Winds drove fires west + south across slopes- made it more destructive
Impacts of the 2017 California wildfires
Social = shutdown of US 101 (traffic disruptions), school closures, > 230,000 forced to evacuate
Economic = wine industry experienced damage ($58bn to state in 2016), damage estimated to be $180bn
Environmental = burned over 307,900 acres, floods + mud/debris slides (damage to topsoil)
Political = fires had a larger impact as funding goes into suppression + not prevention
Immediate responses to California wildfires
-Satellite imagery
-Air quality updates
-Social media to send messages
-“Major disaster declaration” approved by Trump
-deployment of California’s National Guard
-FEMA sent aid (40,000 meals, 40,000 blankets)
-$18.9 million spent on emergency relief
Long-term responses of California wildfires
-Legislators = increase fuel treatments by timber thinning + prescribed burns
-Gov. Brown = issued to establish training + certification programs for prescribed burns -> doubled number of actively managed acres
Why is Haiti classified as a multi hazardous environment + what hazards are they vulnerable to?
-Located on a plate boundary
-Located in Gulf of Mexico- prone to tropical storms
-Earthquakes, tropical storms, flooding, mudslides
Impacts of the 2010 Haiti earthquake
-Social = 800,000 had to live in 450 camps (only 3 had potable water), collapsed buildings caused most deaths, 4,758 schools damaged/destroyed
-Economic = capital city destroyed, capital’s main port was destroyed
-Environmental = cholera from infected UN troops (10,000 deaths), bodies buried in mass graves
-Political = gov + parliament buildings destroyed, political unrest + gang violence, US felt responsibility to help, injured survivors went to hospital in Dominican Republic + overwhelmed them
Physical + human factors which affected the severity + impact of the 2010 Haiti earthquake
-Physical = Enriquillo fault line runs through Haiti, shallow earthquake + epicentre 25km away from capital
-Human = living in flimsy huts, buildings made with weak cement without steel rods, poverty (poorest country in Western hemisphere), low level of resilience
What were the immediate responses to the Haiti earthquake?
Aid workers used GPS to show current coordinates of camps + potential dangers- allowed to keep track of logistics of delivering aid
People hand-moved rubble
First 2 weeks- tents could only be provided for 25% homeless
What were the long term responses of the Haiti earthquake?
40% rubble removed after 2 years by UN partners + locals
Little available space to move people out of emergency tents due to lack of rubble clearance
2 years later- $5.5bn pledged by countries + agencies but only 53% released to projects
