Tectonic Hazards

• Convection currents

  • Mantle is heated by the core. This causes the heated mantle to rise.
  • As this hot mantle reaches the solid crust, it cannot rise further and so it moves sideways. 
  • ​This causes the plate above it to also move.
  • When the mantle cools it will sink back down.
  • This movement is known as a convection current.
• Ridge Push

  • At constructive margins oceanic ridges form high above the ocean floor.
  • Beneath ocean ridges the mantle melts, the molten magma rises as the plates move apart and cools down to form new plate material. 
  • As the crust cools it becomes denser and starts to slide down, away from the ridge, which causes plates to move away from each other. This is called ridge push.
• Slab pull

  • At destructive margins, the denser plate sinks back into the mantle under the influence of gravity.
  • This pulls the rest of the plate behind it.
• 3 points on Distribution of earthquakes :

  1. Occur in linear clusters
  2. Many occur on or in close proximity to plate margins
  3. Clustering of earthquakes around the edge of the Pacific Ocean
• Distribution of earthquakes : Where are they most dominant?

  • Destructive plate boundary
  • Conservative plate boundary
• 3 points on Global distribution of Volcanoes

  1. Occur in linear clusters
  2. Mostly occur on plate margins at constructive and destructive plate boundaries.
  3. Clustering of volcanoes around the edge of the pacific ocean - Pacific Ring of Fire
• Hot spots

  • Some volcanoes occur here, away from plate boundaries
  • Hawaii
• Example of destructive plate margins

  • Nazca and South American plate
• Example of conservative plate boundaries

  • North American plate and Pacific plate
• Example of constructive plate boundary

  • Mid-Atlantic Ridge
• Case Study : Earthquake in LIC

  • Haiti
• Plate margins Haiti lies on :

  • A conservative plate margin
  • Caribbean Plate and North American Plate are sliding past each other
• Magnitude of Haiti Earthquake, 2010

  • 7
• Wealth of Haiti

  • poorest country in the Western Hemisphere
• Primary social effects of Haiti Earthquake, 2010

  1. 230,000 people killed
  2. 250,000 houses destroyed
  3. 50 health care facilities destroyed
• Secondary effects of Haiti Earthquake, 2010

  1. 1 million people homeless. Today, 60,000 people are still homeless - SOCIAL
  2. Contaminated water supplies led to outbreak of cholera, over 8,000 died - SOCIAL.
  3. The Haitian Economy is in ruins – 1 in 5 jobs lost - ECONOMIC
• Immediate responses to Haiti, Earthquake 2010

  • Temporary field hospitals were set up by organisations e.g The Red Cross.
  • Emergency rescue teams arrived from a number of countries, although due to loss of communication services, this was delayed
  • People resorted to looting and sporadic violence
• Secondary responses to Haiti Earthquake, 2010 


  • Schools are being rebuilt with long-lasting material
  • The EU gave €330 million euros to assist in rebuilding
  • Small farmers are being supported – so crops can be grown
  • Port being rebuilt
• Effectiveness of responses to Haiti Earthquake, 2010

  • Not completely effective as the nation is still recovering from the earthquake.
  • The country is still in economic disarray.
• Case Study of Earthquake in HIC

  • Christchurch, New Zealand
• Magnitude of Christchurch, New Zealand 2010

  • 7.4
• Wealth of New Zealand

  • One of the wealthiest countries in the Southern Hemisphere
• Primary Effects Christchurch, New Zealand Earthquake 2010 


  1. 0 people killed
  2. 2 people injured
  3. 100,000 homes damaged
• Secondary Effects of Christchurch, New Zealand Earthquake 2010 


  1. Schools were shut for 5 days so that safety checks could be carried out.
  2. Christchurch could no longer host Rugby World Cup matches so lost the benefits, e.g. tourism and income.
  3. Damage to buried pipes allowed sewage to contaminate the water supply and residents were warned to boil tap water before using it.
• Immediate response to Christchurch, New Zealand Earthquake

  • Chemical toilets were provided for 30,000 residents
  • Aid money poured in – Australia gave $5 million (Aus $) in aid.
  • Army troops were on standby to assist after the Earthquake - brought heavy machinery to clear rubble from rural areas
• Long-term responses of Christchurch, New Zealand Earthquake 2010

  • Homes are no longer allowed to be built in earthquake-prone zones.
  • There are now regular earthquake drills.
  • Buildings built before 2011 are being retrofitted with earthquake proof devices.
• Living with Hazards - Geothermal power

  • Heat generated by volcanoes is harnessed by countries e.g USA
  • In Iceland, the hot water from this source is used directly to heat buildings and greenhouses.
  • This makes the country self-sufficient in many foodstuffs.
  • 17% of Iceland's electricity is created by geothermal power..
• Living with Hazards - Fertile Volcanic Soils

  1. Volcanic soils are very fertile due to the weathering of volcanic products such as ash, lava and rock. This releases valuable nutrients and minerals, enriching the soil.
  2. In Italy, large numbers live on the slopes of Vesuvius and Etna due to the fertile soils, providing rich opportunities for growing products e.g olives and fruit.
• Living with Natural Hazards - TOURISM

  • Many tourists are drawn to volcanic areas due to their dramatic scenery and features such as hot springs.
  • Tourism attracts customs for businesses such as hotels + cafes, creating jobs and improving the local economy.
  • Mt Vesuvius has a large tourist’s car park just below the summit!
• Living with Natural Hazards - Minerals

  • Valuable minerals such as copper, gold, silver, and zinc are all associated with volcanic regions.
  • Volcanic areas are therefore excellent areas for mining. This creates job opportunities.
  • Copper is mined near volcanoes in Chile
• Brief description of earthquakes at destructive plate margins.

  • As two plates converge, pressure builds up
  • Large amount of energy released
  • The rocks eventually fracture causing an earthquake
  • Most happen at shallow depths where the plates collide
• How do volcanic eruptions occur at destructive plate boundaries?

  
  

  • Two plates converge
  • Denser (oceanic) plate subducts under continental plate
  • Melts in the subduction zone
  • Hot magma rises through overlying mantle + lithosphere
  • Eventually erupt causing volcano
  • Magma becomes more viscous as it rises to surface
  • Forms composite volcanoes, steep-sided + violent eruptions
• Conservative plate Margin


  Tectonic plate margin where two tectonic plates slide past each other (at different speeds)
• Constructive plate margin

  • Tectonic plate margin where rising magma adds new material to plates that are diverging or moving apart.
• Define a Natural Hazard

  • A natural event (e.g earthquake, volcanic eruption, tropical storm, flood)
  • Threatens people
  • Has the potential to cause damage, destruction and death.
• DESTRUCTIVE - How does seawater increase the intensity of an eruption?

  1. Adds steam
  2. Makes lava thicker and more explosive than a constructive margin
• What type of volcanoes are formed at constructive plate margins?

  1. Magma escapes easily
  2. Shield volcanoes
• 4 Ways of managing natural hazards

  1. Monitoring
  2. Prediction
  3. Planning
  4. Protection
• Definition : Monitoring

  How may this reduce the effect of a natural hazard?

  • Involves recording physical changes to help forecast when and where a natural hazard may strike.
• Examples of Monitoring of a Natural Hazard

  Scientists' use of seismometers:

  • detect tremors
  • looking for changes in water pressure
  • changes in ground deformation