Natural Hazards

• Hydrological events

  Events to do with rivers/ the earth's water cycle
• Climatological events


  Events that are to do with the earths climate (climate = long term )
• Meteorological events 


  These are to do withe the earth's weather (weather = short term)
• Geophysical events


  Events to do with the earth's structure and processes
• Natural Hazard

  A natural event that has a huge social impact
• Factors that influence the amount of damage or death that has occurred from a natural hazard

  • Wealth of a country (LIC/HIC)
  • Density of population
  • Magnitude of event (eg Richter Scale)
  • Quality of buildings
  • The three P's (Preparation, Planning, Prediction)
  • Secondary Hazards (eg disease, tsunami)
• Oceanic crust VS continental crust

  1. Continental crust is thicker (30 - 50km > 5 - 10km)
  2. Oceanic crust is more dense
  3. Continental crust is made of older rocks
• Layers of the Earth

  • Crust - Solid rock in pieces called tectonic plates
  • Mantle - made of semi molten rock called magma
  • Outer Core - made of liquid iron and nickel
  • Inner Core - made of solid iron and nickel. Temperatures up to 5500 degrees
• Why is the core so hot?

  Made from radioactive decay (Nuclear fusion)
• Convection currents

  1. Heated semi-molten rock in the mantle rises (less dense)
  2. The convection current reaches the crust and spreads out dragging the plate
  3. Magma cools down and sink (more dense) to be reheated
• Primary effects - occur immediately after event, and are directly caused by hazard event. eg lava flows

  Secondary effects - occur after time. considered knock on effects of the hazard event. eg disease, homelessness
• Constructive plate margins

  • Creates new rocks
  • Only creates volcanoes
  • eg Mid-Atlantic Ridge in Iceland
  • rising convection currents drive oceanic crust above. Magma from within the earth is pushed up to the Earth's surface where it cools and solidifies to form new plate material. New land is constructed
• Destructive Plate Margin

  • creates mountains
  • makes both volcanoes and earthquakes
  • Occur when crust is subducted. Convection currents come together causing the oceanic crust (denser, heavier) to be dragged under the continental crust (lighter). This process = subduction. As the plates move against each other, the pressure causes earthquakes to occur. The newly melted oceanic crust is lighter than the surroundings; therefore starts to rise and eat its way through the continental crust above, leading to volcanic activity
• Conservative margins

  • creates earthquakes
  • eg San Andreas Fault
  • The plates slide past each other at different speeds causing them to get stuck. Eventually, enough pressure build up to cause earthquakes
• Collision Margins

  • Creates earthquakes and mountains
  • process is called orogenesis
  • eg Himalayan mountains, the Alps
• Lava flows

  Don't cause death because they only flow at about 15kmph but can damage crops
• Pyroclastic flow are deadly clouds of ash and gas. They race down valleys at 200mph destroying everything in their path. It is a primary effect.
• Lahars

  Mudflows which can drown / suffocate people. (mixture of ash and rainfall/snow). It is a secondary effect
• Ash

  can kill crops, cause roofs to collapse, clog engines in cars and planes, and cause suffocation. It is a primary effect.
• Gases

  eg CO2 can suffocate and kill livestock and people. It is a primary effect.
• Diseases

  eg cholera and typhoid often spread due to lack of clean water particularly in LICs. It is a secondary effect
• Tephra/Pumice/Volcanic Bombs


  These are lumps of debris thrown out of a volcano. It is a primary effect.
• Nuees Ardentes

  Pyroclastic Flow
• Hazard Map


  a map where volcanologists can predict and plot where the hazards of a volcano will go

  However, volcanoes are unpredictable and hazards don't always move in the ways predicted
• Hazard maps. Advantages VS Disadvantages

  • Can help save lives because people will know which areas are at risk and in need of evacuation\
• Volcanic warning signs

  • Earth tremors
  • Start producing gases
  • Shape of ground starts changing
  • Volcano may swell\
• A permanent observatory


  A building close to a volcano where experts closely monitor the volcano
• Engineered responses to volcanoes

  • Damming the lava (boulders dropped from helicopters)
  • Build barrier walls prior eruption
  • Build channels to direct the lava away from towns/villages

  DISADVANTAGES

  • Very expensive
  • Don't always work
  • Only works for lavaflows. (Can't stop more threatening hazards eg pyroclastic flows)
• Planning for a volcano

  Educate locals. Make evacuation routes. Add warning sirens'
• Describing distribution

  T - trend

  E - example

  A - anomaly
• Earthquake- key terms

  
• The Richter Scale


  It is logarithmic ( each level is 10 times stronger than previous level )