Hazards Flashcards
What is a hazard?
Potential threat to life and property caused by an event.
They can be natural or caused by humans.
What are natural disasters?
Disasters occur when a vunerable population is exposed to a hazard.
Dregs model is a good representation of this concept.
What are the 3 main types of hazard?
Geophysical - tectonics, volcanoes
Atmospheric - weather systems, wildfires
Hydrological - bodies of water, floods
Can be a mixture of the 3
What is hazard perception
Viewpoints on how dangerous / how much of a threat a hazard poses to a group of people.
What lifestyle factors affect perception of hazard?
Wealth - may percieve hazard to be smaller as they are less vunerable. Equally, may view it as higher as cost of property damage and financial loss.
Experience - people who have experienced more hazards ar emore likely to understand the extent. Some may be more optimistic and unrealistic on the outlook. ‘Lightning never strikes twice’
Education - more educated will understand the effects - more likely to evacuate
Religion and beliefs - everything happens for a reason, don’t view hazard as negative. Strong environmental conservation belief may vire hazards as huge risk.
Mobility - limited access to evacuation - hazards greater threats in secluded locations. Impared with disabilities or illness
What is fatalism
Response to hazard that nothing can be done, hazards are uncontollable and should be accepted.
What are some active responses to hazards?
- prediction
- adaptation
- mitigation
- management coordinated strategies - prediction, adaptation, mitigation.
- risk sharing - community preparedness - community shares risk and invests collectively to mitigate future hazards.
Name an example of risk sharing that worked
New Zealand - multi-hazard environment under threat from earthquakes, tsunamis, volcanoes and atmospheric related hazards.
Canterbury EQ (2010) cost 20% gdp.
Name the aspects of hazards
Incidence - how often it occurs. Generally low incidence have higher magnitude. Harder to predict and more catastrophic.
Distribution - where they occur geographically. Areas of high hazard activity have management strategies. Pacific ring of fire - EQ and Volcanoes.
Intensity - power of hazard and how damaging the effects
Magnitude - size of hazard, usually how intensity is measured.
Level of developent- affects how well a place can respond to hazard. Ifentical hazards affect places different based on economical development. Multihazard environments struggle as resources spread thinly.
What is the difference between magnitude and intensity of a hazard?
Magnitude - definable by a number scale that doesn’t change.
Intensity - affect on person and can change depending on distance from hazard and management strategies in place.
Evaluate the effectiveness of hazard models.
Can they be applied to every hazard?
Does it take aspects of hazards into account?
Is there a timeframe?
Is the model too vague?
Doesit include hazards surrounding climate change?
Describe the structure of the earth.
Crust - top layer of lithosphere, oceanic crust is dense and continential is thicker but less dense. Oceanic crust is destroyed.
Lithosphere - majority within mantle.
Asthenosphere - semi-nolten layer moves due to concection currents - powered by heat from core.
Mantle - mainly solid rock high in silicon. Top layer semi-molten.
Outer core - semi-molton, mainly iron and nickel.
Inner core - solid ball of iron and nickel. Hot and extreme pressure - radioactive decay provides extreme heat.
What is the plate tectonic theory?
The lithosphere is broken into plates which move through convection currents in the asthenosphere.
State what happens at a destructive boundary for all 3 plate margins.
Oceanic-continental - dense oceanic plate subducts below continental. Ocean trench, fold mountains, explosive composite volvanoes form.
Oceanic-oceanic - heavier plate subducts. Island arcs formed by volcanoes, and trenches form here.
Continential-continential - neither subducts. Forms fold mountains.
State what happens at a constructive plate boundary. Include both types of plate margin.
Oceanic - oceanic - plates pull apart forming ocean ridge. Magma rises in gap forming new land. New land pushes slabs of magma away from ridge - ridge push.
Continental- continental- land pulls apart forming rift valley. Volcanoes form as magma rises through gap. Usually fills up with water forming separate island. Lifted areas called horsts, valley is called a graben.
Explain what ridge push and slab pull are.
Ridge push - slope created when plate smove apart causes plate to push further away through gravity. AKA gravitational sliding.
Slab pull - when plate subducts pulling rest of plate with it.
Name some primary effects of volcanic hazards
Injury / death by:
- tephra
- lava flows - silica lava slow and viscous.
- pyroclastic flow
- increased CO2 levels
Name some secondary effects of volcanic hazards:
Lahars - volcanic material mixed with rainfall / snowmelt.
Acid Rain
Explain the spatial distribution of volcanoes
Pacific ring of fire - 25,000 mile belt. Occur along plate boundaries generally, some located oustide in hotspots.
How is the magnitude of a volcano measured?
Volcanic Explosivity Index - VEI
More powerful - more explosive.
Logorithmic scale from VEI2 - onwards based mainly off tephra ejected.
Describe the frequency of volcanic eruptions.
Estimated 50 - 60 per month. Higher frequency erruptions are effusive while lower frequency are explosive.
Describe the responses to volcanic hazards.
MAPP
Mitigation - intevention to hazard - building walls to direct lavaflows. Strengthen buildings. Establish evac and esclusion zones. Having emergency aid and rescue ready.
Adaptation - move away from hazard area. Capitalise on tourism and agriculture - ash makes fertile soil.
Prevention - hazard cannot be prevented, risk to prople can be prevented - prevent building around volcano
Preparedness - monitoring increases notice of eruptions. - give out warnings. Education in high risk areas. Evacuation proceduces and emergency staff training
What are seismic hazards?
Frition from plates moving through convection currents in asthenosphere causes ground to shake (earthquakes).
Describe the spatial distribution of earthquakes.
Pacific ring of fire (circum-pacific belt) - 90% EQ’s
Alpine-himilayan belt 5 - 6% earthquakes.
How is the magnitude of EQ’s measured?
Logorithmic Richter Scale - 0 - 10.
Modified Mercalli Intensity Scale - rate of destruction caused. Definite end at XII (12). Its subjective - sometimes disputed as dependant on human development.
Magnitude affected by depth of focus
How frequent are earthquakes?
Occur every day in small scales, larger magnitude much less frequent
Is there any way to predict earthquakes?
Some small tremors can give indication, but no there isn’t any way to predict them.
What is liquefaction?
Saturated soil acts as liquid through vibrations from earthquakes. Soil becomes weaker and more likely to subside with weight placed on it.
Describe the responses to seismic hazards.
MAPP
Mitigation - SAR, demolish unsafe buildings, tsunami wave breaks and sea walls.
Adaptation - move away from risk, capitalise on tourism, insurance in place, changing lifestyle, building EQ proof buildings
Prevention - cannot be prevented, and liquefaction can be prevented through soil stabilisation. Avalanches can be prevented through controlled explosions.
Preparedness - earthquake prone areas have intensive awaredness strategies and education.
Earthquake warning systems and evac training.
What conditions need to be met for tropical storms?
Ocean temperature between 26 - 28°c and at least 50 meters deep - provides energy for storm.
Area of unstable air pressure - convergence of high and low pressure.
Present wind shear to form rotation, not too strong that it breaks storm apart.
Rotation of earth - min 5° N+S of equator - no coriolis effect at equator.
Trigger event such as previous thunderstorm, hot spot of sea temperature, area of low air pressure. Trigger and other conditions needed for storm to form
Describe the formation of a tropical storm.
- Warm, moist air rises leaving area of low pressure below - sucks in warm moist air from outside.
- Rising air condenses forming clouds, then forms thunderstorms.
- System begins spinning - coriolis and wind shear.
- Constant addition of energy builds storm, makes it spin faster. Wind speads of 39mph classifies it as a tropical storm.
- Eye forms in centre where cool air descends. Stronger the storm, clearer the eye
- Eye wall surrounding eye - most intense area of storm. When speeds reach 74mph - classifies as hurricane/typhoon/cyclone
- surge released at coast.
- Upon reaching coast - friction of land slows storm down, energy source removed and collapses.
Describe the spatial distribution of tropical storms. Give the names of the types of tropical storm in the different regions they form.
Typhoons - northern hemisphere around India and Asia.
Cyclones - southern hemisphere around Australia and Madigascar
Hurricanes - norther hemisphere around America, some make their way to Europe.
How is the magnitude of tropical storms measured?
Saffir-simpson scale. (1-5) based on windspead and power of storm.
Cat1 - 74-95 mph
Cat2 - 96-110 mph
Cat3 - 111-129 mph
Cat4 - 130-156 mph
Cat5 - 157+ mph
How frequent are tropical storms?
What time of year do the storms form in the Northern and southern hemisphere?
Northern hemisphere storms form June - November.
Southern hemisphere storms form November - April. Many do not develop into strong storms reaching land.
Higher magnitude storms are becoming more frequent.
How predictable are tropical storms?
Very predictable, early warning systems can be sent out. Wearher monitoring whee they form is common and meteorologist know if the conditions are there.
Storms are trackable from satelite and their path (track) can be estimated. The accuracy of the track is higher in the day / hours before approaching. Less acurate a few days away.
What hazards are caused by tropical storms?
Wind speads - excess of 300km/h - can blow buildings down, launch debris at high speeds.
Flooding - high rainfall, storm surges.
Landslides - saturated soil through heavy rainfall
Storm surges - rise in sea level caused by low pressure and high wind speeds.
Describe the responses to storm hazards
Prevention - cannot be avoided, strategies to mitigate exist
Preparedness - awareness through education. Evac plans and training. Satelite tracking and advanced warning systems
Mitigation - SAR and emergency aid, strengthening home - barricades and roof strenghtening. Clearing loose debris
Adaptation - move away from risk area. Design resistant buildings, flood defenses and houses on stilts.
What conditions are required for a wildfire to start.
Thick, dense and flammable vegetation - dry, sappy (eucalyptus). Finer vegetation allows quick spreading.
Enough rainfall for sufficient growth, considerable dry spells - dry out plants. Wind helps spread quicker
How is climate change affecting wildfires?
Increased dry spells with higher temperatures - drying out vegetation. Canada 2023 worst fires recorded. US has seen incline in wildfires and their intensity - six times strength.
Explain the behavior of fire.
Spread quickly on hills. Fires can ‘junp’ across barriers - lit debris.
- Crown fires - entire tree burnt top to bottom. Most destructive fire.
