Restless Earth

Restless Earth

1. Case studies

   • Earthquake in Kobe, Japan 1995
     • Magnitude 7.2
     • 5000 dead, 26000 injured
     • Disrupted transport/communication
     • £100 billion in damages
     • Caused homelessness and unemployment
   • Eruption at Mt. Nyiragongo, Congo 2002
     • 1000km wide river of fast-flowing basalt lava
     • 100 died, 400 000 evacuated
     • 12 500 homes destroyed

2. Tectonic plates

   • Plate boundaries
     • Destructive
       • Two plates collide and one flows beneath the other (subduction)
       • Causes earthquakes and volcanoes
       • Form composite volcanoes
     • Constructive
       • Convection currents pull the crust apart, forming a volcanic ridge
       • Form shield volcanoes
     • Conservative
       • Two plates slide past eachother
       • Creates fault lines
       • Causes earthquakes
     • Collision
       • Two continental plates collide, causing them to buckle
       • Causes earthquakes
   • Convection currents
     • 1. Core heats molten rock in mantle
     • 2. Heated rock rises to Earth's surface
     • 3. Current moves tectonic plates
     • 4. Molten rock cools and flows downwards
   • Crust
     • Continental crust
       • Less dense, granite rocks
     • Oceanic crust
       • Denser basaltic rocks

3. Hazards

   • Volcanoes
     • Shield volcanoes
       • Formed on constructive plate boundaries
         • Eruptions of thin runny lava flow a long distance before solidifying
           • Gently sloping sides and a wide base
       • Contain basaltic magma
         • Very hot, but with low silica and gas content
       • Frequent, but not violent, eruptions
     • Composite volcanoes
       • Formed on destructive plate boundaries
         • Eruptions of viscous and sticky lava/ash which don't flow very far
           • Steep sloping sides and a narrow base
           • Thick layers of lava/ash
       • Contain andesitic magma
         • Less hot than basaltic magma, but with higher silica and gas content
       • Erupt infrequently but violently
       • Causes pyroclastic flows
         • Fast moving current containing a mixture of ash, gases and rock
   • Earthquakes
     • Can be large amounts of death or injury
     • Expensive property damage
     • Remote areas cannot easily get help

4. Managing hazards

   • Earthquake-resistant design
     • Very strong framework
     • Rubber/steel foundations which move slightly
     • Shock absorbers
     • Deeper foundations
     • Strengthened walls
   • Predicting earthquakes and eruptions
     • Difficulties - we don't know...
       • When/where they could happen
       • How big of an impact they will have
       • How many people live there/will be affected
     • What can help us predict them?
       • Strange animal and bird activity/migration
       • Increases in gas emissions or soil temperature
       • Volcano swelling
       • Small earthquakes getting more frequent
       • Water getting warmer
   • Relief
     • Volunteers/emergency services
       • Clear debris + help injured
     • Clean water prevents spread of disease
     • Food and medical help
     • Radio communication
     • Evacuation plan

Imagens e arquivos do mapa