The Global Distribution of Tectonic Hazards


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  • The Global Distribution of Hazards.
    • ? A hazard is a potential threat to human life and property. ? A natural hazard can be either hydro-meteorological (caused by climatic processes) or geophysical (caused by land processes).
    • What are Ocean Fracture Zones (OFZs) and Continental Fracture Zones (CFZs)
      • The OFZ is a belt of activity through the oceans and along the mid-ocean ridges through Africa, the Red Sea, the Dead Sea
      • The CFZ is  a belt of activity along the mountain ranges from Spain through the Alps to the Middle East and to the Himalayas.
    • Tectonic Trends since 1960
      • The total number of recorded hazards has increased.
      • The number of fatalities has decreased, but there are some spikes during mega disasters.
      • The total number of people being affected by tectonic hazards is increasing, due to population growth
      • The economic costs associated with hazards and disasters has increased significantly.
        • Partly due to increases in development as infrastructure in more developed countries costs more to repair.
        • Also, increasing number of insurance policies, especially in developed countries, heightens the costs.  
      • Reporting disaster impacts (e.g. fatalities) is very difficult and controversial for several reasons
        • Depends on whether you look at the direct deaths so those killed in the disaster straight away or indirectly by looking at how many people died of diseases that spread after the disaster. Some impacts take time to become apparent. 
        • The location is important as rural and isolated areas are hard to reach and so it may be hard to collect data from them. Similarly, data may be difficult to collect in areas with very high population densities.
        • Different methods may be used by different organisations so as a result different sources may quote different numbers of deaths and injuries  
        • The number of deaths quoted by a government could be subject to bias. For example, during the 2004 Indian Ocean tsunami, the Burmese government claimed there were 0 deaths Burma. This may be to try and show that the government is doing a good job in terms of aid, protection etc.
    • Geophysical hazards occur near plate boundaries. These plates move at different speeds and directions which can cause collisions, earthquakes and volcanic activity as shown in the map above.  
    • May also be in middle of plates (called intra-plate). The causes of this are not fully understood but it is assumed that plates have pre-existing weaknesses which become reactivated, forming seismic waves. 
    • Volcanic hotspots, such as the Ring of Fire, are also situated amongst the centre of plates. A localised area of the lithosphere (Earth’s crust and upper mantle) which has an unusually high temperature.
    • At hotspots, such as the Hawaii hotspot, magma rises as plume (hot rock). Usually, the most powerful earthquakes occur at convergent or conservative boundaries.

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