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Hazards - Coggle Diagram
Hazards
Volcanic Hazards
Lava flows
lava can flow quickly or slowly depending on its viscosity. Silica makes lava viscous and slow, which is common in explosive eruptions.
Lahars (mudflats)
Caused by a number of reasons, usually by melting ice at high latitudesdangerous mudflows.
When water from rivers, snow-capped volcanoes or crater lakes mixes with rock fragments & volcanic ash, it combines to form fast-flowing mudflows or lahars that rush down the slopes of a volcano.
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Glacial floods
when temperatures are high from magma, glaciers or ice sheets at high temperatures quickly melt & a large amount of water is discharged
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Toxic gases
released during some eruptions, even CO₂ can be toxic as it can replace oxygen as it is heavier
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Nuées ardentes
Clouds of burning hot ash and gas that collapses down a volcano at high speeds. Average speeds of
around 60 mph but can reach 430 mph
Predictability
- Regularity of eruptions can help estimate when eruptions will take place
- Seismic activity, gases releasing, elevation etc. can all indicate an imminent eruption, but there is no definite predictions to a volcanic eruption.
Regularity
- Volcanic eruptions are regular in that the eruptions on each type of boundary are similar
Frequency
- Frequency of eruptions varies per volcano.
- Volcanoes are classed as either active, dormant or extinct.
- a higher frequency eruption means the eruptions are effusive whereas low frequency means the eruptions are explosive.
Magnitude
- Vulcanicity is measured using the Volcanic Explosivity Index(VEI).
- The more powerful, the more explosive
- The scale is logarithmic from VEI 2 and onwards.
- Multiple features are considered when calculating the VEI, including how much tephra is erupted, how long it lasts, how high the tephra is ejected etc.
- Intense high magnitude eruptions are explosive whereas calmer, lower magnitude eruptions are effusive.
Spatial Distribution
- Along constructive or destructive plate boundaries, or located in hotspots
- Ring of Fire = an area of high volcanic & earthquake activity located in then Pacific, and the majority of large volcanoes occur within this 25,000 mile belt.
Type of Volcanic Hazards
Primary
Economic
- Businesses & industries destroyed or disrupted
Social
- People killed
- homes destroyed
Environmental
- Ecosystems damaged through various volcanic hazards
- wildlife killed
Political
- Government buildings & other important areas destroyed or disrupted
- Tephra
- Pyroclastic flows
- Lava flows
- Volcanic gases
Secondary
Economic
- jobs lost
- profit from tourism industry
Social
- Fires can start which puts lives at risk
- mudflows or floods
- trauma
- homelessness
Environmental
- water acidified by acid rain
- volcanic gases contribute to greenhouse effect
Political
- Conflicts concerning government response, food shortages, insurance
- Lahars
- Flooding
- Volcanic landslides
- Tsunamis
- Acid rain
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Types of volcano:
- Fissure volcano - a fracture or crack in rock, often filled with mineral-bearing materials. Fracture or crack at the surface from which lava erupts.
- Shield volcano - Low with gently sloping sides & form from layers of lava. Eruptions are non-explosive. Produce fast flowing basic (fluid) lava that can flow for many miles. Eruptions tend to be frequent but relatively gentle.
- Dome volcano - A steep-sided mass of viscous & often blocky lava extruded from a vent; typically has a rounded top & covers a roughly circular area. Domes can generate deadly pyroclastic flows. The sides of a dome or an erupting lava flow on a dome can collapse down a steep slope to form a hot avalanche of hot lava fragments & gas (pyroclastic flow).
- Ash-cinder volcano - usually erupt lava flows, either through a breach on one side of the crater or from a vent located on a flank. Commonly found on the flanks of shield volcanoes, stratovolcanoes, and calderas.
- Composite volcano - steep, conical volcanoes built by the eruption of viscous lava flows, tephra, & pyroclastic flows. They are usually constructed over tens to hundreds of thousands of years & may erupt a variety of magma types.
- Caldera volcano - large basin-shaped volcanic depression with a diameter many times larger than included volcanic vents; may range from 2 to 50 km (1 to 30 mi) across. Commonly formed when magma is withdrawn or erupted from a shallow underground magma reservoir.
Types of lava:
- Basaltic lava has a low-silica content & is relatively fluid because of its low viscosity. Eruptions are non-explosive & regular.
- Andesitic lava has intermediate viscosity, with intermediate silica content. Eruptions can be very destructive, especially when the volcano has been dormant & hasn’t erupted recently.
- Rhyolitic lava is viscous. High viscosity is related to high silica content. Rhyolitic magma traps gas & coagulates up in the vent of the volcano. Pressure builds up over time until it is suddenly released in a catastrophic eruption. Large explosive eruptions can be highly dangerous
Types of eruption:
- Icelandic eruptions - basaltic lava flows gently from fissures
- Hawaiian eruptions - basaltic lava lows gently from a central vent
- Strombolian eruptions - (thicker) basaltic, frequent, explosive eruptions of tephra & steam. Occasional, short lava flows.
- Vulcanian eruptions - (thicker) basaltic andesitic & rhyolitic, less frequent but more violent eruptions of gases, ash & tephra
- Vesuvian eruptions - (thicker) basaltic, andesitic & rhyolitic, following long periods of inactivity, very violent gas explosions blast ash high into the sky
- Peléean eruptions - andesitic & rhyolitic, very violent eruptions of nées ardentes
- Plinian eruptions - rhyolitic, exceptionally violent eruptions of gases, ash & pumice. Torrential rainstorms cause devastating lahars
Ash cloud
ejected from the volcano & rise up & form an eruption column in the atmosphere. Can be transported on the wind over long distances. Will cover all surfaces > buildings, roads & farms over thousands of kilometres & cause major disruption to everyday life.
Pyroclastic Flows
If eruption column collapses a dangerous fluid-like pyroclastic flow composed of hot rocks, ash & volcanic gases can travel down the flanks of the volcano. The most destructive & deadly volcanic hazards.
Plate Tectonics
- Tectonic plates move due to the convection currents in the asthenosphere, which push & pull the plates in different directions
- Convection currents are caused when the less dense magma rises, cools, then sinks. The edges of where plates meet are called plate boundaries
Different Plate Boundaries
- At plate boundaries, different plates can either move towards each other (destructive plate margin), away from each other (constructive plate margin), or parallel to each other (conservative plate margin).
- Different landforms are created in these different
interactions
Structure on Earth
Inner core
- Solid ball of iron/nickel
- Very hot due to pressure & radioactive decay
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Mantle
- Mainly solid rock, & the rocks
are high in silicon.
- the very top layer of
the mantle is semi-molten
magma, which is known as the
asthenosphere. The
lithosphere rests on top.
Asthenosphere
- Semi-molten layer constantly
moves due to flows of heat
called convection currents
Lithosphere
- Broken up into plates
- Majority of the lithosphere is
within mantle
- The top of the lithosphere is
the crust
Crust
- The thin top of the lithosphere
- Oceanic crust is dense and is destroyed by plate movement, continental crust is less dense
and is not destroyed.
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Theories
Alfred Wegener - continental drift
- Gathered evidence to suggest that just one giant continent (Pangaea) existed about 300 million years ago & later split into 2 smaller continents - Laurasia & Gondwanaland
- Todays continents formed from further splitting of these 2 masses
Geological evidence
- the 'jigsaw fit' of South America & west Africa
- Similar ancient glacial deposits found in South America, Antarctica & India - formed together & moved
- Structural faults in rocks in Brazil & west Africa match when 2 are compared
- Similar rock sequences in norther Scotland & easter Canada, indicate that they were formed under the same conditions in 1 location
Biological evidence
- Fossils found in India are comparable with fossils in Australia
- Fossil remains of the reptile Mesosaurus are found in both South America & southern Africa indicating they were once joined together
- Identical plant fossils have been found in the coal deposits of both India & Antarctica
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Seismic Hazards
- The focus is the point underground where the earthquake originates from.
- The epicentre is the
area above ground that is directly above the focus.
- When the plates are stuck, the convection currents in the asthenosphere continue to push, which builds the pressure.
- It builds so much that it cannot be sustained & the plates eventually give way
- All of this pressure is released in a sudden movement, causing a jolting motion in the plates
- This jolt is responsible for seismic movement spreading throughout the ground in the form of seismic waves
- Plates don't directly fit in to each other, meaning they do not move in fluid motions
- At all boundaries plates can become stuck due to friction between plates
Spatial Distribution
- The Ring of Fire accounts for 90% of the world’s Earthquake
Magnitude
- Seismicity is measures using the logarithmic Richter Scale which is a measure of the strength of seismic waves.
- The magnitude of the earthquake is also dependent on the depth of focus.
- Conservative boundaries have the shallowest boundaries, meaning they are closer to the epicentre & the seismic waves are stronger.
- Destructive boundaries usually have deeper focuses, meaning the seismic waves are spread over a larger area before they reach the epicentre.
Frequency
- Earthquakes are frequent around the world and occur every day at boundaries.
- Hundreds of smaller magnitude earthquakes that cannot be felt by humans
- larger earthquakes are less frequent.
Regularity
- Earthquakes follow no pattern and are random so there is irregularity between events.
Predictability
- Earthquakes are almost impossible to predict
- Microquakes may give some indication but the magnitude cannot be predicted as how strong they are is random
Shockwaves
- When two plates move side by side, friction builds up & pressure increases; this pressure is stored as potential energy -> can't move so just builds up
- When pressure becomes too much the plates move
- transferred to kinetic energy -> released & vibrates through ground
- the further away from focus the weaker the shockwaves
Tsunamis
- when oceanic crust is jolted during an earthquake, all of the water above this plate is displaced.
- The water travels fast but with a low amplitude
- As it gets closer to the coast, the sea level decreases so there is friction between the sea bed & the waves.
- This causes the waves to slow down & gain height, creating a wall of water that is on average 10 feet high, but can reach 100 feet.
Liquefaction
- When soil is saturated, the vibrations of an earthquake cause it to act like a liquid
- Soil becomes weaker & more likely to subside when it has large weight on it.
Landslides & avalanches
- Movement in soil or snow will cause it to become unstable
Type of Seismic Hazard
Primary
Environmental
- Earthquake can cause fault lines which destroy the environment
- liquefaction
Social
- Buildings collapse, killing/injuring people & trapping them.
Political
- Government buildings destroyed
Secondary
Environmental
- Radioactive materials & other dangerous substances leaked from power plants
- Saltwater from tsunamis flood freshwater ecosystems
- Soil salinisation
Economic
- Economic decline as businesses are destroyed
- High cost of rebuilding & insurance payout
- Sources of income lost
Social
- Gas pipes rupture, starting fires which can kill
- Water supplies are contaminated as pipes burst, spreading disease & causing floods
- Tsunamis which lead to damaging flooding
Political
- Political unrest from food shortages or water shortages
- Borrowing money for international aid
- Can be initial chaos & ‘lawlessness’
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Storm Hazards
Tropical storm - low pressured, spinning storm with high winds & torrential rain
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Formation
- Warm, moist air rises, leaving area of low pressure below. Causes warm air from surrounding areas of higher pressure to move into this low pressure area & rise
- When warm air rises, cools, condensing into thunderstorm clouds
- Whole system spinning due to Coriolis effect. Southern hemisphere storms spin clockwise, Northern hemisphere, anticlockwise
- Constant additions of energy from warm air causes storm to spin faster & generate higher wind speeds. At 39mph = tropical storm
- Eye of storm = centre, 30 miles wide & extremely low pressure. Cool, dry air descends in eye, causing the weather to be relatively calm & cloud free. The more intense the storm the clearer the eye.
- Surrounding eye is eyewall, most intense & powerful area of storm. Warm, moist air rapidly rises here, with extremely high winds & torrential rain. Winds reach 74mph -> hurricane/cyclone/typhoon.
- When tropical storm reaches coast, low pressure & high winds cause a large amount of sea water to be taken into system & released as high wave -> storm surge
- Storm reaches land, no longer has supply of energy & eye collapses. Heavy rain persist for days.
Predictabilities
- Tropical storms form away from land meaning satellite tracking of cloud formations & movement can be tracked & general route can be predicted
- Closer hurricane gets the easier to predict based on pressure & intensity of storm
Regularity
- Tropical storms are irregular because although they occur in same areas, their path does not follow set route - the route taken is dependent on the storm & climatic conditions
Frequency
- Tropical storms form in Northern Hemisphere from June - November, Southern Hemisphere from November - April
- Majority of tropical storms don't develop into strong storms & don't reach land
- Tropical storms @ higher magnitude & reaching land thought to be increasing frequency
Magnitude
- Measured on the Saffir - Simpson Scale based on wind speed & power of storm
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Type of Storm Hazard
Primary
Environmental
- Beaches eroded
- Sand displaced
- Coastal habitats -> coral reefs are destroyed
Economic
- Businesses destroyed
- Agricultural land damaged
Social
- Drowning
- Debris carried by high winds can injure or kill
- Buildings destroyed
Political
- Government buildings destroyed
Secondary
Environmental
- River flooding/ salt water contamination
- Animals displaced from flooding
- Water sources changing course from blockages
Economic
- Rebuilding & insurance payout
- Sources of income lost
- Economic decline from sources of income destroyed
Social
- Homelessness
- polluted water supplies spread disease
- Food shortages from damaged land
Political
- Issues paying back international aid
- Pressure for government to do more about global warming
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Concept of Hazard
- Potential threat to human life & property caused by an event
- Event becomes a hazard when it is a threat to people
- Often result in disasters that cause some loss of life &/or damage to the built environment & create severe disruption to human activities
Atmospheric:
- Hazards caused by
atmospheric processes
& conditions created
because of these
Hydrological:
- hazards caused by water
bodies and movement
Geographical:
- hazards caused by land
processes, majorly
tectonic plates
Hazard Perception
- Different view points on the risk of hazards
- Can depend on economic & cultural lifestyles
Wealth
- wealthy may perceive hazards to be smaller -> less vulnerable
- or view as more at risk because of property damage & financial loss
- Can afford to protect themselves by building sea defences, constructing earthquake-resistant buildings, providing better emergency services
Experience
- someone with experience of hazards -> more understanding of full effects
Education
- more educated on hazards may understand the full effects
Religion & beliefs
- View hazards as put there by God & part of natural cycle of life
- Strongly in environmental conservation -> hazards a huge risk to natural hazard
Mobility
- Limited access to escape view hazards as greater threats than they are
- Those who can't leave quickly feel more at risk
Human responses
Fatalism
- viewpoint that hazards are uncontrollable natural events, & any losses
should be accepted as there is nothing that can be done to stop them
Prediction
- using scientific research & past events to know when a hazard will take place, warnings can be delivered & impacts of hazards reduced
Prevention
- Unrealistic although there have been ideas & schemes such as seeding clouds in potential tropical storms to cause more precipitation & weaken the system as it approaches land
Protection
- To protect people, their possessions & the environment from the impact of the event - modifications to built environment - improved sea walls, earthquake-proof buildings
- Governments & people can react to try & change attitudes & behaviour to natural hazards to reduce vulnerability - risk sharing #
Adaptation
- Attempting to live with hazards by adjusting lifestyle choices so that
vulnerability to the hazard is lessened
- People see that they can prepare for & therefore survive the events by prediction, prevention, and/or protection, depending upon the economic & technological circumstances of the area in question
Mitigation
- Strategies carried out to lessen the severity of a hazard
Management
- Coordinated strategies to reduce a hazard’s effects. This includes
prediction, adaptation, mitigation
- Integrated risk management > identification of hazard, analysis of risks, establishing priorities, treating risk & implementing risk reduction plan, developing public awareness & communication, monitoring & reviewing process
Risk sharing
- A form of community preparedness, whereby the community shares the
risk posed by a natural hazard & invests collectively to mitigate the impacts of future
hazards to reduce the loss of life & property damage
- Through education & awareness programmes, evacuation procedures & provision of emergency medical & food supplies & shelters
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Fear
- People feel so vulnerable to an event that they are no longer able to face living in the area & move away to regions perceived to be unaffected by the hazard
The Park Model
a graphical representation of human responses to hazards. The model shows
the steps carried out in the recovery after a hazard, giving a rough indication of time frame
- The steepness of the curve shows how quickly an area deteriorates and recovers.
- The depth of the curve shows the scale of the disaster
Stage 3
- Restoring the area to
the same or better
quality of life
- Area back to normal
- Infrastructure rebuilt
- Mitigation efforts for
future event
Stage 2
- Services begin to be
restored
- Temporary shelters
and hospitals set up
- Food and water
distributed
- Coordinated foreign
aid
Stage 1
- Immediate local
response - medical
aid, search and rescue
- Immediate appeal for
foreign aid - the
beginnings of global
response
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Hazard management cycle
outlines the stages of responding to events, showing how the same stages take place after every hazard.
Mitigation
- Strategies to lessen effects of another hazard
- barriers, warning
signals developed,
observatories
Recovery
- Long-term responses
- restoring services,
reconstruction
Response
- Immediate action taken after event
- evacuation, medical assistance, rescue
Preparedness
- Being ready for an event to occur
- public awareness, education, training
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Wildfire
A large, uncontrolled fire that quickly spreads through vegetation
Conditions -> intense
Vegetation type
- Thick, close together allows fires to spread quickly & easily.
- Trees & thick bushes lead to more intense wildfires; grasslands do not burn as intensely
- Vegetation with flammable oils - eucalyptus, causes more intense fires
Fuel Characteristics
- Vegetation should dry to allow it to catch
- Finer vegetation causes fires to spread quicker, but larger, thicker forms of vegetation burns for longer & more intensely
Climate & recent weather
- Wildfires can occur anywhere in world
- Occur in a climate that has enough rainfall to have sufficient plant growth, but considerable dry spells & droughts to dry out the fuel
- Areas with dry seasons -> California
- Wind causes fires to spread more
- Climatic events can make wildfires grow more intense & extend wildfire seasons
- The Santa Ana Winds & Diablo Winds in California cause more wildfire damage
- El Niño & La Niña are also climatic events that are thought to affect wildfire prevalence
- Effects of these phenomena cary throughout world, in California El Niño is thought to provide warmer, wetter seasons to grow vegetation & La Niña's dryer seasons create more wildfires
Causes of Wildfires
- naturally or by humans
- majority of wildfires caused by human activity
- Natural causes -> lightning, volcanoes
Human causes -> cigarettes, barbecues, agriculture, train lines
Type of wildfire hazard
Primary
Environmental
- Air pollution from ash
- water pollution
- habitats destroyed in fire
- toxic gases released in burning
Economic
- Business destroyed
- Agricultural land damaged
- Cost of fighting fires
Social
- People killed or injured in fires
- Homes destroyed
- People go missing during evacuations
Political
- Government buildings destroyed
Secondary
Environmental
- removing invasive species & stimulating seed germination
- Migration patterns of animals affected
- Increased CO2 from fires could heightened the greenhouse effect
Economic
- High cost of rebuilding & insurance payout
- Sources of income lost
- Discouraging visitors, losing tourism sector
- Planes cancelled
Social
- Homelessness
- Food shortages from destroyed agricultural land
- Health problems -> asthma from smoke inhalation
Political
- Borrowing money for international aid
- Pressure for government to do more about global warming due to increased frequency
Risk Management
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Mitigation
- Immediate response -> protecting those directly at risk extinguishing fire
- Search & rescue teams, immediate aid, evacuations
Immediately mitigate -> fire needs to be extinguished or diverted
- long term response -> controlled burnings, burnings created on purpose to remove flammable materials so less fuel available
- Those living near, ensure homes do not contribute to wildfire spread
Adaptation
- Adapt & live with consequences of fire
- Expenses of insurance & clean-up & well educated -> part of everyday life
- If temperatures continue to increase, it may lead to unprecedented changed in wildfire patterns -> avoidable with more eco-conscious decisions to reduce CO2 emissions
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