Tectonics + Hazards

• Hot Spot


  Volcanoes found away from the plate boundary, due to a magma plume closer to the surface
• Ash


  Fine particles and dust ejected during an eruption, which can remain airborne as clouds or accumulate on the ground
• Degg’s Model


  This model shows that a hazard becomes a disaster if it affects a vulnerable population
• Convection Currents


  The circulation of magma within the mantle (asthenosphere). Magma is heated by radioactive processes in the core and cools at the surface, and so circulates between the two places
• Asthenosphere


  The upper mantle layer of the Earth. It is semi-molten and approximately 2000km wide
• Hazard Mitigation Cycle


  The sequence of governance of a natural hazard: monitoring & prediction, mitigation, preparedness
• Epicentre


  The point on the surface, directly above the earthquake's origin
• Continental Crust


  Crust that forms the continents of the lithosphere, on average 35km thick
• Accretion Wedge is the accumulation of material at the point of subduction
• Focus


  The place in the crust where the pressure/seismic energy is released
• Continental Drift


  The movement of tectonic plates, due to varying weights of crust. It was originally thought that convection currents caused the movement of the plates, but now Slab Pull is thought of as the primary driving force
• Aseismic Buildings are designed to withstand or minimise destruction during an earthquake
• Natural hazards


  • Hot Spot
  • Jokulhaup
  • Lahar
• Oceanic Crust


  Crust, usually thinner than continental crust, that forms the sea floor. It is on average 7km thick
• Love Waves


  A surface earthquake wave with horizontal displacement
• A sudden glacial flood caused by a glacier on top of or near a volcano melting due to the heat from the eruption
• Paleomagnetism


  The alternating polarisation of new land created. As magma cools, the magnetic elements within will align with the Earth’s magnetic field, which can alternate over thousands of years
• Volcanoes found away from the plate boundary due to a magma plume closer to the surface
• A measure of an earthquake's energy released, considered the most accurate measure
• Primary Waves


  An earthquake wave causing compressions within the body of rock
• Lithosphere


  The upper crust of the Earth (average thickness = 100km)
• Partial Melting


  Elements within the lithosphere have different melting points, and so rock is partially melted, partially solid
• Geological features


  • Mid-Ocean Ridge
  • Oceanic Crust
• Pyroclastic Flow


  A mixture of gases and rock fragments, at high temperatures and speeds, that flows down the slopes of a volcano during an eruption
• A flow of mud and debris
• Governance of a natural hazard


  • Monitoring & prediction
  • Mitigation
  • Preparedness
• Park’s Model


  A model describing the decline and recovery of a country over time, following a natural disaster
• Parting oceanic plates at a constructive plate boundary creates a ridge, with new land at the base of the oceanic valley
• Richter Scale is a logarithmic measure of earthquake’s intensity
• Tsunami is caused by initial vertical water displacement (often from a submarine earthquake) creating waves with large destructive power
• Types of seismic waves


  • Primary Waves
  • Secondary Waves
  • Love Waves
  • Rayleigh Waves
• Volcanic Explosivity Index (VEI)


  A measure of the magnitude of a volcano’s eruptions
• Seismic Waves are the energy released during an earthquake, in the form of Primary, Secondary, Love and Rayleigh Waves
• Subduction


  Oceanic plate is forced below continental plate, due to the oceanic plate being more dense than the continental plate
• Rayleigh Waves


  A surface earthquake wave causing both horizontal and vertical displacement
• Wadati-Benioff Zone


  A region of the subducting plate, most affected by pressure and friction, where most destructive margin earthquakes originate
• Volcanic Island Arc


  A series of volcanoes (often in the shape of an arc) that are formed consecutively, as a tectonic plate moves across a magma plume
• Slab Pull


  The force contributing to the movement of tectonic plates. Slab Pull is due to the weight of the plate
• Secondary Waves


  An earthquake wave causing vertical displacement within the body of rock