natural hazards Flashcards
describe the oceanic crust
-basalt and gabbro
-6km thick
-thin
-dense
describe the continental crust
-granite
-35km thick
-thicker
-less dense
what is the slab pull movement of the crust
- occurs at destructive boundary
- dense oceanic plate subducted
- as the plate sinks into the mantle the rest of the plate follows
what is the convection currents movement of the crust
-hot magma rises and spreads out under the plates
-as it cools it becomes denser and sinks
what is the ridge push movement of the crust
-also known as gravitational sliding
-occurs at constructive plate boundaries
-magma rises up and solidifies, creating new plate and pushing old plate apart
what happens at a destructive plate boundary
1- two plates pushed together, heavier oceanic gets subducted beneath lighter continental
2- oceanic plate sticks and locks as it tries to slide under the continental
3- heat from friction and the mantle starts to melt the subducted plate
what happens at a constructive plate boundary
1- two plates move apart from eachother
2- a gap appears and molten magma rises to fill the gap
3- solidifies to create new rocks on the sea bed
4- over time layers of new rocks build up and break through the surface of the ocean
what happens at a conservative plate boundary
1- two plates slide in the same direction
2- pressure and mention builds up as the plates lock together
3- eventually the plates break causing a sudden surge forward - earthquake
what happens at a collision plate boundary
1- two continental plates crash into eachother
2- as they collide they trigger earthquakes
3- the rocks between the plates get pushed up and folded
formation of sea floor spreading at a constructive margin
- two plates move away from eachother
- molten magma rises creating new crust
-submarine volcanoes can form
formation of a rift valley at a constructive margin
- two players move away from each other
- molten magma rises creating new crust
formation of a deep sea trench at a destructive margin
- continental and oceanic plates meet
- oceanic plate is subdued underneath
formation of island arcs at destructive margins
-magma pushes up from the trenches creating a volcano
- the magma solidifies creating an island
formation of young gold mountains at collision margins
- continental plates meet
- both plates push upwards
formation of fault lines at conservative margins
- two plates move parallel to eachother
- crust is neither created nor destroyed
what are fissure eruptions at constructive margins
- occur when two plates move apart
- lava is ejected through fissures
- normally comprised of basalt
- the snow cooling of the lava produces columnar jointing
- lava fills of hollows rather than creating a dome shape
formation of shield volcanoes at constructive margins
- lava flows from a central vent
- lava spreads over a large area before solidifying
- results in a cone with long, gentle sides
- volcano is made up of many layers
formation of dome volcanoes at destructive margins
- lava flows from a central vent
- acid lava quickly solidifies
- steep sided convex cone
- volcano is made up of many layers
formation of ash and cinder cones at destructive margins
- fine ash and cinder is ejected from a central vent
- layers of ash and cinder build up
- shallow sided concave sides
- volcano is made up of many layers
formation of caldera volcanoes at destructive margins
- gas builds up in the magma chamber causing an explosion
- the sides of the crater subside
- craters can be flooded by the sea creating lagoons
formation of magma plumes
-radioactive decay in the earths core heats the mantle creating plumes of magma
- this causes the plates to move or create a hot spot volcano
- the hot spot stays fixed whilst the plate above moves, creating a chain of extinct volcanoes
- bends in the chain show plate movement
what is pyroclastic flow
- mix of hot rock lava ash and gases
- more common with andesitic lava
- often occur at subduction zones
- can travel large distances
- temp of 350c to 1000c
pyroclastic flow impacts
- destroys any object or structure in its path
- can cause fires
- ice and snow can melt due to high temps
- risk of serious burns
- can cause floods and lahars
what is nuce ardente
- means ‘glowing cloud’
- contain more dense material
- are normally only found 50km from source
what is tephra
- rock fragments ejected during an eruption
- large fragments land close to the source
- small fragments can travel great distances
nuce ardente and tephra impacts
- ash can cause breathing difficulties, block sunlight and alter temps
- endangers infrastructure
- damages crops
- can interrupt communication equipment
what are mudflows/ lahars
- ash and volcanic material mix with water
- commonly occurs in glaciated areas due to the rapid melting of ice
- speeds up to 60km/h
- can be highly erosive
- will engulf anything they pass over
mudflows/ lahars impacts
- crushes, abrades, buries or carries away anything in its path
- can melt snow and ice
- destroys bridges and roads
- can silt up river causing floods
- can trap people in hazardous areas
what are lava flows
- lava flows down the side of a volcano
- may cover hundreds of km
- slow flow rate allows for evacuation
- will destroy anything it passes over
lava flows impacts
- flows over, surrounds, buries or ignites anything in its path
- can trigger a lahar
- can cause water to evaporate immediately creating a molten shower
- can cause methane gas build creating explosions
what are gases and acid rain
-Co2 and So2 are released upon eruption
- can cause breathing difficulties and harm wildlife
- gases react with water vapour creating acid rain
- damages ecosystems and infrastructure
gases and acid rain impacts
- acid rain can poison water supplies
- gases can cause health difficulties
- gases can create unseen hazards
Nevada del Ruiz eruption and lahar, Columbia, 1980s
-25,000 dead
- $218 million in damage
Mt St Helens, Washington state, USA, 1980
- 57 dead
- pyroclastic flows and lahars
- destructive plate boundary
Mt Kilauea, Hawaii
- hot spot
- basaltic lava - low viscosity, frequent, predictable eruptions
environmental impacts of volcanic events
- polluted water
- change in weather
- habitats destroyed
- crop damage
social impacts of volcanic events
- people forced out their homes
- death
- injuries
- loss of jobs
economic impacts of volcanic events
- damage repair
- loss of jobs
- damage to crops and infrastructure
political impacts of volcanic events
- government may struggle to rebuild the area
- aid
- government strain
short term responses to volcanic events
- evacuation of people at risk
- deployment of emergency services
- international aid
- aid from eight in the country sent to the area
long term responses to volcanic events
- risk management
- creation of hazard maps to aid evacuations
- alert systems
- storage of emergency food water and aid supplies
monitoring gas emissions
- the main gas is sulphur dioxide
- an increase in gas quantity can signal the start of volcanic activity
- gas levels can drop rapidly in the few hours before an eruption
ground deformation
- magma moving in the lithosphere can deform the ground above
- volcanoes swell prior to an eruption due to a gathering of magma
thermal monitoring
- magma movement and changes in. gas release can alter temperatures
- magma heats up groundwater
satellite images and remote sensing
- monitors change in volcanoes from the surface
- images can be used to compare to previous times
mass movement and mass failures
- movement of land can happen before, during or after eruption
- can show evidence of past activity and suggest deformation is happening
what is basaltic lava
- hot, runny and low viscosity
- flows as rivers of molten rock as takes longer to cool
- gentle but frequent eruptions
- found at constructive plate margins
what is andesitic lava
- cooler, slower and viscous
- flows very short distances as soon cools down and solidifies
- less frequent eruptions but they are more violent due to gas build up
- found at destructive plate margins
Iceland volcano 2010 social impacts
- 700 people evacuated
- communication and travel infrastructure disrupted
- homes and farmland destroyed
- people were stranded around europe
Iceland volcano 2010 economic impacts
- tourism declined
- many industries were affected due to lack of imported parts and raw materials
- fresh produce couldn’t be imported
- total loss for airline companies was £1.1billion
Iceland volcano 2010 environmental impacts
- homes and farmland destroyed
- infrastructure damaged or destroyed
Iceland volcano 2010 responses
- government rebuilt roads and infrastructure in under 2 months
- environment has grown back more fertile than ever
- tourism industry has grown rapidly
Congo eruption 2002 social impacts
- 250 dead
- 350,000 people dependant on aid one month after disaster
- 5,000 buildings destroyed
Congo eruption 2002 economic impacts
- 15% of the town was destroyed
- many farmers lost income due to damage
Congo eruption 2002 environmental impacts
- poisonous gases caused acid rain
- carbon dioxide levels are still a serious issue
Congo eruption 2002 political impacts
- up to 400,000 people were forced to move across the border
Congo eruption 2002 responses
- managing the disaster was badly coordinated as is an LIC
- 10 aid agencies helped out
- US provided $7.5million in funding
- locals had to work themselves to support the reconstruction
what is an earthquake
- movement within the earths crust causes stress to build up
- when the stress exceeds the strength of the rock fractures
- the stored energy is released as an earthquake
- intense seismic waves spread out from the focus
- these waves are what causes the ground to shake
primary effects of an earthquake
- ground shaking
- ground rupture
secondary effects of an earthquake
- soil liquefaction
- tsunamis
- effects on people and built environment
- fires
- landslides and avalanches
environmental impacts of an earthquake
- tsunamis
- landslides/ avalanches
- disrupt migration patterns
- water pollution
- loss of habitats
social impacts of an earthquake
- deaths
- loss of jobs
- displaced from homes - homelessness
- spread of disease from polluted water
- property damage
economic impacts of an earthquake
- supply chains disrupted
- companies suffer
- damage to infrastructure and property
- loss of productivity
- negative impacts on tourism
political impacts of an earthquake
- media framing government responses
- relocation of people out the country
- aid from other countries causes dependence on them
- future planning to avoid impacts
how does preparedness reduce impacts of an earthquake
- alarms
- evacuation plans and drills
- food and water supply
- medical supplies
- warnings
- monitoring
how does mitigation reduce impacts of an earthquake
- rubber shock absorbers in the foundations absorb tremors
- buildings reinforced with steel
- open areas for evacuation
- lightweight roofs reduce injuries
how does prediction reduce impacts of an earthquake
- remote sensing of ground movement
- monitoring fault lines
- seismographs and seismometers can be used to measure plate activity
- animal activity
how does adaption reduce impacts of an earthquake
- evacuation routes and safe zones
- refil stocks of food and water
- buildings to be resistant to shakes
- educate people on plans and risks
Christchurch earthquake 2011 key stats
- 6.3 magnitude
- 4km depth
social impacts of christchurch earthquake 2011
- 185 dead
- disease spread from contamination
- schools closed for two weeks
- 1/5 of the population left the city
- homes destroyed
environmental impacts of christchurch earthquake 2011
- water quality declined
- river changes and landslides
- habitat loss
- increased the city’s flood risk
- liquefaction
- sewage discharge
economic impacts of christchurch earthquake 2011
- up to $30billion in damage
- high unemployment rates
- tourism decreases
- damage to infrastructure and property
political impacts of christchurch earthquake 2011
- 70% of responders disagreed with governments response
- residents felt left out of consultation
responses of christchurch earthquake 2011
- $6-7million in international aid
- pop up hospitals were set up
- city centre was redesigned to be more safe
- government offered grants and loans to help rebuild the cathedral
Türkiye-Syria earthquake 2023 key stats
- earthquake - 7.8 magnitude, 18km depth
- aftershock - 7.5 magnitude, 13km depth
social impacts of Türkiye-Syria earthquake 2023
- 55,000 deaths
- 130,000 injured
- millions of people displaced
- risk of contagious diseases from contaminated water
- 3 million displaced refugees
- 12 million people face food insecurity
environmental impacts of Türkiye-Syria earthquake 2023
- 300,000 buildings destroyed or unstable
- devastated agricultural livelihoods
- liquefaction
- ground failure
- flooding
economic impacts of Türkiye-Syria earthquake 2023
- house prices in turkey increased by up to 45%
- turkey damage cost - $103 billion
- direct damage cost - $34 billion
political impacts of Türkiye-Syria earthquake 2023
- syrian civil war since 2011 led to worse living conditions, 3 million internally displaced refugees and 90% of syrians living below poverty line
responses of Türkiye-Syria earthquake 2023
- 105 countries have support and aid
- shelter, food and medical aid supplied
