Geography GCSE- The Challenge of Natural Hazards


Natural Hazards

Natural Hazard- a naturally occuring event that has a huge social impact 

  • atmospheric= wind/ drought/ hurricane/lightning
  • flooding= tsunami/flood/mudflow
  • geological=tsunami/avalanche/landslide/volcano/earthquake

Hazard Risk= the chance/ probability of being affected by a natural hazard

Factors Affecting Risk=

  • Urbanisation- hazards will have greater impact on densely populated/ developed areas
  • Climate Change- causes extreme events/ places wetter or drier= increased risk
  • Poverty- forcing people to live in risk areas/ lack of resources to prevent/ protect hazards
  • Farming- farmers live on floodplains as very fertile

Why live in areas at risk?

  • lack of knowledge/ living in povert so no choice/ no event before so aren't aware
  • events don't happen that often/ faming/ weigh up advantages
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Tectonic Hazards

Earth's Layers=

  • inner core, outer core, mantle- 2900km wide, semi solid with magma, convection currents
  • Crust- solid outer layer, 5-60km thick, broken into plates- oceanic and continental

Earthquake- a sudden and violent period of ground shaking

Volcano- an opening in Earth's crust from which lave, ash and gases erupt

Plate Margins=

  • Constructive- plates away from each other due to cc in mantle, magma rises= v, movement= e (Mid Atlantic Ridge)
  • Destructive- plates move towards each other and collide, denser oceanic subducted under continental, trench in subduction zone where oceanic sinks to form magma= rises into v, friction of subduction causes e, if both continental- fold up for fold mountains (Nazca under South American)
  • Conservative- plates move past each othera nd get stuck= friction and pressure= seismic waves relaesed= earthquake (San Andreas Fault)
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Earthquakes- Chile

Factors Increasing Effect-

  • Magnitude- higher= more damage, depth of focus- shallower= more destructive
  • Level of development- richer= better protection, time of day- night= people sleeping
  • Population density- higher= more casualties, distance from epicentre- more severe at centre

Chilian Earthquake 27th Feb 2010-

  • Magnitude= 8.8, destructive plate margin, pacific ocean, waves at 800km/h
  • Development= life expec 81, GNI 22,540, HDI rank= 41/187

Primary Effects (immediate)-

  • 500 killed, 12000 injured, cost $30bil, many lost water/ power, 220000 homes, 4500 schools destroyed

Secondary Efects (hours, days, years after)-

  • 1500km roads damaged, coastal towns devastated, fire at chem plant near Santiago
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Earthquakes- Chile and Nepal

Immediate Responses-

  • international help for field hospitals/ emergency services, temporary repairs to highway in 24hrs
  • power/water restored 90% homes in 10 days, national appeal $60 mil= 30k emergency shelters

Long Term Repsonses-

  • reconstruction plan help 200,000 households affected, strong economy easily rebuilt

Nepal Earthquake 25th April 2015-

  • Magnitude= 7.9, destructive, 15km below surface, epicentre 80km from capitol Kathmandu
  • Development= life expec 69, GNI= 2520, HDI rank= 145/187

Primary Effects-

  • 1/3 pop affected, 9000 died, 20,000 injyred, 3mil homeless, 1.4mil neede food/ water/ shelter, 7000 schools destroyed, $5bil damage
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Earthquakes- Nepal

Secondary Effects-

  • landslides/ avalanches blocked roads, Mt ev avalanche killed 19, av in langtang 250 missing

Immediate Repsonses-

  • helicopters resuced mountain people and devlievred aid to cut off towns, 1/2mil tents, field hospitals supporting overcriwded hospitals, 300,000 migrated from Kathmandu

Long Term Responses-

  • lakes emptied/ landslides cleared, 7000 schools rebuilt, Aug 2015 everest routes created= tourism

Living on an Active Plate Margin Advantages=

  • cheaper energy, heating for homes, water for energy
  • beautiful views, shelter from wind, photo opportunities
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Reducing Risk of Tectonic Hazards

Monitoring= using scientific equip to detect warning signs of events

  • remote sensing- detect heat and shape changes, seismicity- seismograph records earthquakes
  • geophysical measurements- changes in gravity, hydrology- gases dissolved in water

Prediction= historical ev/ monitoring= predictions of when and where event might happen

  • can predict volcanoes from scientific monitoring
  • can't predict earthquakes as lack of clear warning signs, but know areas at risk

Protection= designing hazards to withstand tectonic hazards

  • earth embankments/ explosives to divert volcano lava
  • tsunami walls near nuclear power stations/ coast
  • shock absorbers/ concrete columns, auto shutters for earthquake protection

Planning= identifyig and avoiding places most at risk

  • hazard maps for volcanoes, maps for earthquakes to protect high value land uses (hsopitals)
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Global Atmospheric Circulation

  • Coriolis Effect- winds distorted by earth's rotation
  • Greatest Insolation- (input of energy from sun)= equator
  • Pressure- around earth, move n and s during year (with the seasons)


  • At equator concentrated sun energy, warm air rises, low pressure belt= air rises and cools= clouds and high rainfall in equatorial regions.
  • Air separates and moves to higher latitudes, cool air sinks at hot deserts (30 N and S of equator)= high pressure belt= few clouds and little rainfall= hot/dry but cold at night
  • Cold polar air mixes with warmer air and rises= high pressure belt, unstable boundary between, rising air cools and condenses into clouds= rainfall (UK 55 N of equator)
  • Air cools and sinks= high pressure belt= cold dry climate
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Tropical Storms- Typhoon Haiyan

Tropical Storms- large areas of low pressure or extreme depressions

  • located 5-15 N and S of equator, between tropics
  • America= hurricanes, E Asia= typhoons, W Asia/ Africa= cyclones
  • need ocean 26.5 degrees and wind- climate change heats oceans= more storms
  • In eye= calm weather, in eye wall= stormy/ lightning/ rain/ wind

Typhoon Haiyan=

  • 3rd-11th Nov 2013, Philippines (S-E Asia), 170mph winds, 15m high waves
  • Caused by tropical moisture clouds in Pacific, category 5 super typhoon

Primary Effects=

  • 6300 drowned in storm surge, 600k displaced, 40k homes destroyed,
  • 30 k fishing boats destroyed, 400mm of rain= flooding
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Typhoon Haiyan

Secondary Effects-

  • 14mil affected, 6mil lost source of income, $4.5bil damage, landslides blocked roads
  • Power supplies cut off for a month, airlines disrupted= no interbational help
  • Looting/ violence in Tacloban, shortages of food/water= disease outbreak

Immediate Responses-

  • international aid= food/water/shelter, 1200 evacuation centres, 
  • Philippines Red Cross delivered food aid, US helicopters for search and resue

Secondary Responses-

  • homes built away from flood risk, more cyclone shelters, rebuilding
  • foreign docs (US, EU, Australia) supported new ops, rice farming/ fishig quickly reestlablished
  • Cash for work programmes, aid agencies replaced fishing boats
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Reducing Effects of Tropical Storms

Monitoring and Prediction-

  • early warnings, hurricane modelling, hurrucane track prediction- determine path/ power


  • houses on stilts= water run through, shutters for wind, bicycles to deliver warnings
  • channel below house, natural landscaping absorbs water


  • Government educate and warn public, weather reports, TV/ radio safety instructions
  • water proof bags, disaster kit, pets indoors, cars away from trees, unplug devices
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UK Weather Hazards

  • 2003 Heatwave- 38.5 d in Kent, 2000 died, roads melted, train tracks buckled
  • Dec 2010 Heavy Snow- N Ireland -18.7 d at Castlederg

Somerset Levels Floods 2014-

Causes- 31.4cm rain 24hrs, ground already saturated, steep slopes, confluence, swollen rivers


  • meadows/ farms underwater, can't drive, angry locals

Immediate responses- villagers travel by boat, local communities helped

Long Term Responses-

  • £20mil flood action plan, March 2014 8km Rivers Tone/ Parratt dredged, road levels raised
  • river banks strengthened, 2024 consideration  to Bridgewater tidal barrage
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Climate Change- Causes and Effects

Causes of Climate Change-

  • Orbital Changes- changes circular- ellpitical affecting distance from sun, circular= closer= more heat energy= increased temps, Axial tilt- tilt chages changing temps
  • Volcanic Activity- eruptions release SO2 and CO2= ghg that trap sun's radiation= increased temps, ash can block out sun= reduced temps
  • Solar Activity- sunspot activity max= sun gives off more heat, explosions on Earth= solar flares= increased temp
  • Burning Fossil Fuels- release CO2= ghg= traps sun's heat
  • Deforestation- trees absorb CO2 in photosynthesis= reduced absorbtion
  • Agriculture farming= methane produced in decomposition/ digestion= ghg


  • Glaciers and ice sheets melt= loss of polar habitats, species extinct as conditions change 
  • Hotter/ drier climate= drought, declining cro yields, desertification= food/ water shortages
  • Extreme weather events, change in rainfall, coastal areas flooded as sea levels rise
  • Heat related health problems, mass migration and overcrowding to areas away from risk, 
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Climate Change- Evidence and Management


  • Sediment Cores- remains of organisms analysed to identify envrionmental conditions/ temps from Quaternary period and compare
  • Analysis of Pollen- preserved in lake beds/ bogs and analysed to show plants that grew then compraed to now to show change in climate
  • Ice Cores- analyse gas levels in ice to show temp change across time
  • Temp Records- global temps with thermomtere since mid 19th century


  • Alternative energy production- using renewabke sources (solar, wind, biofuel)= no CO2 produced (EU target 20% renewable 2020)
  • International Agreements- agree to common policies- reduce climate change/ ghg emissions
  • Carbon capture- capture CO2 released in industry and storing underground
  • Reforestation- more CO2 removed from atmosphere, Conservation International- restore 73mil trees in Amazon by 2023
  • Adapting- sea walls for rising sea levels, modify crops (drought resistant), water eficient devices
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