Chapter 5 - Hazards - Complete Flashcards
Define a hazard?
Something that’s a potential threat to human life or property
Define natural hazard?
A hazard caused by the earth and our atmosphere
Define geophysical hazard?
Caused by land processes
- Earthquakes
- Volcanic eruptions
- Landslides
- Tsunamis
Define atmospheric hazards?
Caused by climatic processes
- Tropical cyclones
- Storms
- Droughts
- Extreme hot/ cold weather
- Wildfires
Define hydrological hazards?
Caused by water movement
- Floods
- Avalanches
Define disaster?
When a hazard actually seriously affects humans.
What’s the difference between a natural hazard and a disaster?
A natural hazard is a volcano erupting in a deserted place but becomes a disaster when it affects people.
Define risk?
The likelihood that humans will be seriously affected by a hazard.
Define vulnerability?
How susceptible a population is to the damage caused by a hazard.
Define 5 factors that affect peoples perceptions of a hazard? W R E P E P
- Wealth = rich people afford to move house.
- Religion = view hazard as act of God.
- Education = More education better understanding of risks.
- Past experiences = People live in hazard-prone areas, adapt and know circumstances.
- Personality = People fear hazards/ others think they’re exciting.
Define 4 things governments try to do to reduce their vulnerability of a hazard? P P P F
- Preparation to reduce its magnitude. Building flood defences. Cost risk sharing.
- Prediction of hazard, when, where a hazard will occur.
- Protection of property.
- Fatalism - accept the hazard cannot be avoided.
Define the Park Model?
Shows the different phases of response to a hazard.
Define the 5 stages in the Park Model? P D D R R R
- Pre-Disaster
- Disruption
- Relief
- Rehabilitation
- Reconstruction
Define PRE-DISASTER in the Park Model?
Before the event, situation is normal.
Define DISRUPTION in the Park Model?
During & directly after the hazard occurred, destruction of property, loss of life.
Define RELIEF in the Park Model?
In the aftermath of event, rescue efforts focus on saving people & preventing further damage.
Define REHABILITATION in the Park Model?
Once the immediate impacts are under control, people start to resolve longer-term problems (shelter, aid).
Define RECONSTRUCTION in the Park Model?
Involves rebuilding permanent houses, infrastructure.
Define the 4 phases in the hazard Management Cycle? M P R R
- Mitigation = minimise impacts in future, build defences.
- Preparedness = Planning how to respond in future, warning systems.
- Response = How people react in disaster situation, emergency services rescue people.
- Recovery = Getting affected area back to normal, repairing rebuilding houses, restoring services.
Define the Earth’s core?
- Centre of earth
- Inner core = solid ball containing Iron & Nickel.
- Outer core = semi-molten containing Iron & Nickel.
- 6000oC hot
Define the Earth’s mantle?
- Around core is mantle (Silicate rock).
- Nearest to core/ quite rigid.
- Asthenosphere above mantle (semi-molten).
- 1000-3500oC hot.
Define the layers of the Earth?
- Inner core
- Outer core
- Mantle
- Asthenosphere
- Crust
Define 2 types of Crust?
- Continental = Is thicker (30-70km thick) less dense.
- Oceanic = Is thinner (6-10km thick) more dense.
Define tectonic plates?
- Lithosphere divided into many slabs, which move in relation to each other.
- Plates meet at plate boundaries/margins.
Define 3 theories why tectonic plates move?
- Convectional currents
- Slab pull
- Ridge push (Gravitational sliding)
Define CONVECTIONAL CURRENTS as a theory why tectonic plates move?
- Parts of asthenosphere heat up from core, less dense, slowly rise, then cool down and slowly sink.
- Circular movements of semi-molten rock called convection currents.
- Create drag on base of tectonic plate, making them move.
Define SLAB PULL as a theory why tectonic plates move?
- At destructive plate margins, denser crust is forced under less dense crust.
- Sinking plate edge pulls rest of plate towards boundary.
Define RIDGE PUSH as a theory why tectonic plates move?
- Constructive plate margin, magma rises to surface forms new crust.
- Surrounding rock heats, expands, rises above surface forming slope.
- New crust cools down, dense, gravity shifts denser rocks downslope, away from plate margin.
- Puts pressure on tectonic plate, causing then to move apart.
Define sea-floor spreading?
- As tectonic plates diverge, magma rises to fill gap.
- Sea bed gets wider as plates diverge, more magma fills gap.
- Creates mid-ocean ridges.
Define constructive margin?
Occurs where two plates move APART from eachother.
Define destructive margin?
Occurs where two plates are moving TOWARDS EACHOTHER (converging).
Define how a constructive plate margin causes volcanoes to erupt?
- Magma is less dense than the plate above, it rises and can erupt to form a volcano.
Define how a constructive plate margin causes earthquakes to happen?
- Plates don’t move apart in uniform.
- Causes pressure build-up, plates crack, making fault line causing earthquake.
Define 2 landforms created at a constructive margin?
- Ocean ridge
- Rift valley
Define OCEAN RIDGE as a constructive margin landform?
- Diverging plates underwater
- Underwater volcanoes erupt & build up above sea level.
- Mid-Atlantic Ridge (Eurasian & North American plate)
- Iceland built from underwater volcanoes build-up.
Define RIFT VALLEY as a constructive margin landform?
- Plates diverge beneath land, rising magma makes crust bulge & fracture, forming fault lines.
- Crusts between parallel fault lines drops down forming rift valley.
- East African Rift System (Mozambique –> Red Sea)
- Volcanoes found near rift valleys (Mount Kilimanjaro).
Define the landforms created at an OCEANIC-CONTINENTAL destructive margin? D F V E
- Deep-sea trench
- Fold mountains
- Volcanoes
- Earthquakes
Define how DEEP SEA TRENCH are formed at an OCEANIC-CONTINENTAL destructive margin?
- More dense oceanic crust is forced under less dense continental crust.
Define how FOLD MOUNTAINS are formed at an OCEANIC-CONTINENTAL destructive margin?
- Where plates meet.
- Made up of sediment that has accumulated on the continental crust, which are folded upwards along with the edge of the continental crust.
Define how VOLCANOES are formed at an OCEANIC-CONTINENTAL destructive margin?
- Magma less dense than continental crust and will rise back to surface forming a volcano.
Define how EARTHQUAKES are formed at an OCEANIC-CONTINENTAL destructive margin?
- One plate moves under other they get stuck.
- Causes pressure building up.
- Pressure breaks, plates jerk past each other, causing earthquake.
Define the landforms created at an OCEANIC-OCEANIC destructive margin?
- Denser plate submerged forming DEEP SEA TRENCH, triggering EARTHQUAKES & VOLCANIC ERUPTIONS.
- Volcanic eruptions that occur underwater form ISLAND ARCS.
Define the landforms created at a CONTINENTAL-CONTINENTAL destructive margin?
- Plates move towards eachother building pressure causing EARTHQUAKES.
- FOLD MOUNTAINS form when continental crusts converge.
Define conservative plate margins?
Occurs when two plates slide past eachother parallel.
Define EARTHQUAKES at conservative plate margins?
- Two plates get stuck alongside eachother, pressure builds, plates jerk forming fault lines causing an EARTHQUAKE.
- e.g. San Andreas Fault (California)
Define how magma plumes are formed at plate margins?
- Magma plume is a vertical column of extra-hot magma which rises up from mantle.
- Magma plume stationary over time, but crust moves above it.
- New volcanoes form above magma plume.
As crust moves, a row of volcanoes form on the land. - Hawaii is a magma plume.
Define where most volcanic eruptions take place?
Near constructive/destructive plate margins.
Define what the lava is like at a constructive plate margin?
- Basaltic lava formed here (very hot, low viscosity).
- Flows quickly
- Eruptions of basaltic lava are frequent, last long time.
- Not violent.
Define what the lava is like at a destructive plate margin?
- Andesitic & Rhyolitic lava formed here.
- Cooler, more viscous (Flows slower).
- Usually erupt intermittently, last short time.
- Subduction zones, melting plate forms magma, which rises to surface as volcano.
Define the 6 forms volcanic hazards can come in? P L V P M A
- Pyroclastic flows (nuée ardente)
- Lava flows
- Volcanic gases
- Pyroclastic & ash fallout
- Mudflows (Lahars)
- Acid rain
Define PYROCLASTIC FLOWS (nuée ardente) as a form of a volcanic hazard?
- Mixture of super-heated gas, ash & volcanic rock
- Flows downside of volcano, high speed, 80km/h for 10-15km long.
- As travel so fast little warning, cause death & destruction, burning.
Define LAVA FLOWS as a form of a volcanic hazard?
- Lava flows from volcanic vent in side of volcano.
- Speed, distance travelled depends on temperature & viscosity.
- Relatively slow, people can evacuate in time.
- Destroys anything in path, buildings & vegetation.
Define VOLCANIC GASES as a form of a volcanic hazard?
- Lava contains gases (carbon dioxide, sulfur dioxide).
- Released into atmosphere when erupted.
- Gases harmful to humans & animals if inhaled.
- Cause breathing difficulties.
Define PYROCLASTIC & ASH FALLOUT as a form of a volcanic hazard?
- Material being ejected from volcano falls to ground.
- Fallout ranges if sizes of sediment, ash, rock.
- Large pieces of falling tephra damages buildings, kill people.
- Ash cloud cover area, hard to see.
Define MUDFLOWS (Lahars) as a form of a volcanic hazard?
- Material mixes with large amounts of water, flows very quickly (80km/h) up to 10+km long.
- Can bury or destroy habitats, settlements, infrastructure.
Define ACID RAIN as a form of a volcanic hazard?
- Gases react with water vapour in atmosphere, then falls as acid rain.
- Damages ecosystem, cause stone/metal to erode/deteriorate.
Define magnitude in terms of volcanos?
- Volcanic Explosivity Index - grades volcanoes 0-8 amount & height of matieral ejected.
- Volcanic events range from small, slow lava flows to huge eruptions of lava, ash, gas.
Define frequency in terms of volcanoes?
- Volcanoes can erupt from every few months to once every 100,000 years.
- Less frequent eruptions are usually larger in magnitude.
Define randomness vs. regularity? in terms of volcanoes?
- Some volcanoes erupt at very regular intervals, others may be more random.
Define predictability in terms of volcanoes?
- The regularity of a volcano erupting helps scientists predict when it might erupt again.
- Also monitor tiny earthquakes & changes in shape of volcano, which suggests an eruption might happen.
Define primary impacts of volcanic eruptions?
- Are a direct result of the eruption
- e.g. people killed by falling tephra
Define secondary impacts of volcanic eruptions?
- Occur as a result of the primary impacts
- Pyroclastic flows (nuée ardente) melt glaciers causing flooding.
Define social impacts of volcanic eruption?
- People killed, buildings destroyed by pyroclastic flow.
- Pyroclastic flows (nuée ardente) & lava start fires, damage buildings.
- Mudflows (Lahars) & flooding cause damage.
Define environmental impacts of volcanic eruptions?
- Ecosystems damaged/destroyed.
- Acid rain cause acidification of aquatic ecosystems, killing plants & animals.
- Volcanic gases increase enhanced greenhouse effect.
- Ash clouds reduce sunlight reaching earth, decreasing temperatures.
Define economic impacts of volcanic eruptions?
- Destroy businesses, ash cloud prevent aircraft, damage crops.
- Damaged buildings expensive to repair.
- Location attracts tourists, boosting economy.
Define political impacts of volcanic eruptions?
- Damage agricultural land, food shortages, conflict caused.
- Governments spend money to repair damaged property.
Define hazard mitigation?
Anything done to reduce severity or impacts of a hazard.
Define short-term responses?
- Occur immediately before, during or after the hazard.
- e.g. evacuating people, providing food.
Define long-term responses?
- Designed to reduce impacts of future eruptions by managing the risks.
Define the 3 categories of long-term responses?
P
P
A
- Prevention
- Preparedness
- Adaptation
Define PREVENTION as a long-term response for volcanic eruptions?
- Not possible to prevent volcanic eruption.
- Possibly prevent eruption affecting people.
Define PREPAREDNESS as a long-term response for volcanic eruptions?
- Plans before eruption to minimise risk/vulnerability.
- Scientists install monitoring systems to predict eruption & plan for evacuation.
- Stop people entering area when eruption predicted to erupt.
- Individuals can find nearest emergency shelter.
- Communities set up search & rescue/ fire response teams.
Define ADAPTATION as a long-term response for volcanic eruptions?
- How people change behaviour to minimise risks.
- Buildings strengthened reducing collapsing.
- Capitalise opportunities of living near a volcano e.g. farming, tourism.
Define what causes an earthquake?
- Two plates jerk past eachother sending out shockwaves.
- Shockwaves spread out from the focus.
- Focus has strongest waves, cause more damage.
- Epicentre on surface shockwave felt first by people.
Define the 3 ways earthquakes can be measured?
- Richter scale = measures magnitude, logarithmic(0-9).
- Moment magnitude scale (MMS = total amount of energy released, logarithmic, more accurate than Richter scale.
- Mercalli scale, measures impact using observations of event (1-12).
Define the 3 hazards caused by an earthquake?
- Tsunamis
- Landslides & avalanches
- Soil Liquefaction
Define TSUNAMIS as a hazard caused by an earthquake?
- Large waves caused by the displacement of large volumes of water.
- Triggered by underwater earthquakes.
- Stronger if starts near coast.
- Waves travel very fast, high death toll, little warning.
Define LANDSLIDES & AVALANCHES as a hazard caused by an earthquake?
- Shaking of ground dislodges rocks, soil or snow causing landslides or avalanches downslope quickly.
- High speed movement, little warning.
Define SOIL LIQUEFACTION as a hazard caused by an earthquake?
- Soil is saturated with water, vibrations of earthquake cause to act like liquid.
- Makes soil weaker and subsides where heavy weight on top of it (buildings).
- Mass destruction.
Define the 3 factors which affect the magnitude and nature of an earthquake?
M
R
D
- Margin type
- Rate of movement
- Depth of focus
- Biggest earthquakes occur at ____________ margin.
- ___________ margin have lower magnitude earthquakes.
- Biggest earthquakes occur at destructive margin.
- Constructive margin have lower magnitude earthquakes.
Define RATE OF MOVEMENT which affects the magnitude and nature of an earthquake?
- Tectonic plates move in relation to each other at different rates (1-15cm per year).
- No clear relationship between rate of movement and earthquake magnitude.
Define DEPTH OF FOCUS which affects the magnitude and nature of an earthquake?
- Focus can be on surface or deep underground.
- Deep focus earthquakes have higher magnitude than shallow focus’s.
- Deep focus do less damage - shock waves generated further from surface, so reduced power.
Define aspects of low magnitude earthquakes?
- Hundreds of low mag earthquakes occur everyday.
- Occurrence very random.
- Scientists monitor tectonic movement to predict areas of risk.
Define primary impacts of seismic hazards?
Are direct result of the hazard, killed by tsunami, rupture of earth.
Define secondary impacts of seismic hazards?
Occur as a result of the primary impacts, earthquake break gas pipe, causing fires.
Define social impacts of seismic hazards?
- Cause buildings to collapse, killing people.
- Liquefaction cause gas pipes/power lines to break.
- Lack of clean water, cause diseases.
- Tsunamis flood areas, killing people.
Define environmental impacts of seismic hazards?
- Industrial buildings damaged, leaks toxic chemicals.
- Fires started by damaged gas & electricity lines.
- Tsunamis flood freshwater ecosystems.
- Kill plants & animals.
Define economic impacts of seismic hazards?
- Destroy business premises, ground shaking.
- Damages economy of region and country.
- Damage to industry & buildings, expensive repair.
Define political impacts of seismic hazards?
- Shortages of food, water, energy (cause conflict).
- Governments borrow money to repair damage, put country in debt.
Define PREVENTION as a long-term response for seismic hazards?
- Not possible to prevent seismic hazard.
- Authorities can prevent land prone to liquefaction to be evacuated, build sea walls for tsunami.
Define PREPAREDNESS as a long-term response for seismic hazards?
- Install earthquake warning systems.
- Individuals & businesses have plans how to respond during earthquake - find shelter.
- Communities set up search & rescue teams.
Define ADAPTATION as a long-term response for seismic hazards?
- Buildings designed to withstand earthquakes, using strong flexible materials, foundation absorb energy.
- Buildings designed to reduce vulnerability to tsunamis, tall strong buildings allow people to escape.
Define tropical storms?
- Huge spinning storms, strong winds, heavy rain.
- Develop over warm water.
- Air rises & condenses releases energy increases wind speed.
Define the 4 conditions needed to form a tropical storm?
- Disturbance near sea-surface triggering storm (low pressure).
- Sea water above 27oC at least 70m deep.
- Convergence of air in lower atmosphere, within ITCZ, forces warm air to rise.
- 5 degrees from equator.
Define what happens to the energy of a tropical storm when it goes over land?
- Loses its energy and dies down.
- Moist air is cut off.
Define which way tropical storms rotate in each hemisphere?
- Northern hemisphere = spin anticlockwise
- Southern hemisphere = spin clockwise
- Centre has low pressure.
- Rising air spiral around eye from Coriolis effect.
Define how a tropical storm is measured?
SSS
W
C
- Saffir-Simpson Scale.
- Based on wind speed (1-5).
- Cloud formations can predict tropical storm event.
Define the 5 forms storms can come as?
- High winds = 300km/h, destroy buildings.
- Storm surge = Large rise in sea level, high winds.
- Heavy rain = as moist air rises, torrential rain.
- Flooding = Heavy rain, high river discharge overflow.
- Landslides = Water infiltrate into soil, less stable ground.
Define social impacts of tropical storms?
- People drown, injured, killed.
- Houses destroyed (left homeless).
- Electricity/gas lines damaged.
- Flooding causes sewage overflow contamination water, lack of clean water, diseases.
- Damage to agricultural land.
Define political impacts of tropical storms?
- Conflict over food supplies.
- Expensive repairs to buildings, infrastructure.
Define economic impacts of tropical storms?
- Buildings & infrastructure expensive to rebuild.
- Businesses are damaged, can’t trade.
- Agricultural land damaged, affects trade.
Define environmental impacts of tropical storms?
- Beaches eroded, coastal habitats destroyed.
- Environments are polluted from toxic spills.
- Landslides block watercourses, change course.
Define wildfires?
- Uncontrolable fires that destroy forests, grassland.
- Occur in rural areas.
- If reach settlement will destroy buildings.
Define the 3 types of wildfires?
- Ground fire = ground itself burns.
- Surface fire = leaf litter, low-lying vegetation burns.
- Crown fire = fire moves through canopy of trees.
Define the 4 conditions needed for wildfires?
- Vegetation type
- Fuel characteristics
- Climate & recent weather
- Fire behaviour
Define VEGETATION TYPE as a condition of a wildfire?
- Thick undergrowth or closely spaced trees.
- Some trees contain oil, burn more easily.
- Eucalyptus trees shed bark helps spread fire.
Define FUEL CHARACTERISTICS as a condition of a wildfire?
- Fine, dry material catch fire more easily.
- Large amounts of fuel form continuous cover to burn.
Define CLIMATE & RECENT WEATHER as a condition of a wildfire?
- More rainfall, more vegetation, more fuel.
- A distinct dry season.
- Warm, dry weather causes water to evaporate.
- Strong winds blows more oxygen to fuel fire.
Define FIRE BEHAVIOUR as a condition of a wildfire?
- Creeping fire moves across ground surface slowly.
- Running fire spreads rapidly, more intense.
Define the natural causes of a wildfire?
- Lightning particularly likely to start fire.
- Volcanic eruptions can produce hot lava starting fires.
Define the human causes of wildfires?
- Can be accidental (dropping cigarettes, campfires, barbecues, fireworks.
- On purpose (arson) to burn forest.
Define social impacts of wildfires?
- People killed, injured.
- Homes destroyed, left homeless.
- Damage power lines, reservoirs.
- Cause health problems (Smoke)
Define political impacts of wildfires?
- Governments change forest management practices to reduce risk.
- Governments face criticism when wildfires have serve impacts.
Define economic impacts of wildfires?
- Destroy businesses, loss of jobs & income.
- Insurance premiums increase.
- Expensive fighting wildfires.
- Discourage tourists visiting area, reduce income.
Define environmental impacts of wildfires?
- Habitats destroyed, change ecosystem.
- Soils damaged, remove organic matter.
- Smoke caused air pollution, contaminates water.
Define the short-term responses to wildfires?
- Putting out fire, diverting it away from settlements.
- Evacuating people.
- Spraying water.
Define the long-term responses to wildfires?
- prevention
- preparedness
- adaptation
- Prevention = public education
- Preparedness = Emergency plan, supplies, food.
- Adaptation = Change way people live to cope with incident. Build houses out of non-flammable material.
Define the lava type of volcanoes at an ocean ridge?
Basaltic lava, low viscosity (very runny)
Define the lava type of volcanoes at subduction zones?
Andesitic lava, high viscosity (very sticky)
Define the volcano type at ocean ridges?
Gently sloped, small explosion, more running lava
Define the volcano type at a subduction zone?
Very steep, massive explosion, lots of pyroclastic flows (nuée ardente) and ash clouds.
Define the volcano type at rift valleys?
Very explosive and more effusive (spill out lava flows).
Define the volcano type at hot spots?
Shield curve (not steep)
Define the lava type of volcanoes at hot spots?
Very runny, low explosion
Define the ocean crust underneath the continental crust being melted?
Benioff zone
