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Tectonic processes and hazards

Tectonic processes 1

Enquiry Question 1: Why are some locations more at risk from tectonic hazards?

1.1 The global distribution of tectonic hazards can be explained by plate boundary and other tectonic processes.

  • The global distribution and causes of earthquakes, volcanic eruptions and tsunamis.
  • The distribution of plate boundaries resulting from divergent, convergent and conservative plate movements (oceanic, continental and combined situations).
  • The causes of intra-plate earthquakes, and volcanoes associated with hot spots from mantle plumes.

1.2 There are theoretical frameworks that attempt to explain plate movements.

  • The theory of plate tectonics and its key elements (the earth’s internal structure, mantle convection, palaeomagnetism and sea floor spreading, subduction and slab pull).
  • The operation of these processes at different plate margins (destructive, constructive, collision and transform).
  • Physical processes impact on the magnitude and type of volcanic eruption, and earthquake magnitude and focal depth (Benioff zone).

1.3 Physical processes explain the causes of tectonic hazards

  • Earthquake waves (P, S and L waves) cause crustal fracturing, ground shaking and secondary hazards (liquefaction and landslides).
  • Volcanoes cause lava flows, pyroclastic flows, ash falls, gas eruptions, and secondary hazards (lahars, jökulhlaup).
  • Tsunamis can be caused by sub-marine earthquakes at subduction zones as a result of sea-bed and water column displacement.

Enquiry question 2: Why do some tectonic hazards develop into disasters?

1.4 Disaster occurrence can be explained by the relationship between hazards, vulnerability, resilience and disaster.

  • Definition of a natural hazard and a disaster, the importance of vulnerability and a community’s threshold for resilience, the hazard risk equation.
  • The Pressure and Release model (PAR) and the complex inter-relationships between the hazard and its wider context.
  • The social and economic impacts of tectonic hazards (volcanic eruptions, earthquakes and tsunamis) on the people, economy and environment of contrasting locations in the developed, emerging and developing world.

1.5 Tectonic hazard profiles are important to an understanding of contrasting hazard impacts, vulnerability and resilience.

  • The magnitude and intensity of tectonic hazards is measured using different scales (Mercalli, Moment Magnitude Scale (MMS) and Volcanic Explosivity Index (VEI)).
  • Comparing the characteristics of earthquakes, volcanoes and tsunamis (magnitude, speed of onset and areal extent, duration, frequency, spatial predictability) through hazard profiles.
  • Profiles of earthquake, volcano and tsunami events showing the severity of social and economic impact in developed, emerging and developing countries.

1.6 Development and governance are important in understanding disaster impact and vulnerability and resilience.

  • Inequality of access to education, housing, healthcare and income opportunities can influence vulnerability and resilience.
  • Governance (P: local and national government) and geographical factors (population density, isolation and accessibility, degree of urbanisation) influence vulnerability and a community’s resilience.
  • Contrasting hazard events in developed, emerging and developing countries to show the interaction of physical factors and the significance of context in influencing the scale of disaster.

Enquiry question 3: How successful is the management of tectonic hazards and disasters?

1.7 Understanding the complex trends and patterns for tectonic disasters helps explain differential impacts.

  • Tectonic disaster trends since 1960 (number of deaths, numbers affected, level of economic damage) in the context of overall disaster trends. (6); research into the accuracy and reliability of the data to interpret complex trends
  • Tectonic mega-disasters can have regional or even global significance in terms of economic and human impacts. (ü 2004 Asian tsunami, 2010 Eyafjallajokull eruption in Iceland (global independence) and 2011 Japanese tsunami (energy policy))
  • The concept of a multiple-hazard zone and how linked hydrometeorological hazards sometimes contribute to a tectonic disaster (the Philippines).

1.8 Theoretical frameworks can be used to understand the predication, impact and management of tectonic hazards.

  • Prediction and forecasting (P: role of scientists) accuracy depend on the type and location of the tectonic hazard.
  • The importance of different stages in the hazard management cycle (response, recovery, mitigation, preparedness). (P: role of emergency planners)
  • Use of Park’s Model to compare the response curve of hazard events, comparing areas at different stages of development.

1.9 Tectonic hazard impacts can be managed by a variety of mitigation and adaptation strategies, which vary in their effectiveness.

  • Strategies to modify the event include land-use zoning, hazard – resistant design and engineering defences as well as diversion of lava flows. (P: role of planners, engineers)
  • Strategies to modify vulnerability and resilience include hitech monitoring, prediction, education, community preparedness and adaptation. (F: models forecasting disaster impacts with and without modification).
  • Strategies to modify loss include emergency, short and longer term aid and insurance (P: role of NGOs and insurers) and the actions of affected communities themselves.
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