Hazards

• Accretion Wedge - The accumulation of material at the point of subduction.
• 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.
• Coriolis Effect - The Earth’s spin affects the movement of air masses and winds, depending on a location’s latitude.
• Asthenosphere - The upper mantle layer of the Earth. It is semi-molten and approximately 2000km wide.
• Degg’s Model - This model shows that a hazard becomes a disaster if it affects a vulnerable population.
• Epicentre – The point on the surface, directly above the earthquake's origin.
• 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.
• Focus – The place in the crust where the pressure/seismic energy is released.
• Ground Fires - Wildfires that burn through the peat and vegetation beneath the surface, making them slow but difficult to extinguish.
• Hazard Management Cycle - The sequence of governance of a natural hazard: preparedness, response, recovery, and mitigation.
• Controlled Burning - Intentionally burning vegetation with the aim of reducing fuel available for a wildfire and disrupting the fire’s path.
• Jokulhaup - A sudden glacial flood caused by a glacier on top of or near a volcano melting due to the heat from the eruption.
• Lithosphere - The upper crust of the Earth (average thickness = 100km).
• Love Waves - A surface earthquake wave with horizontal displacement.
• Moment Magnitude Scale - A measure of an earthquake's energy released, considered the most accurate measure.
• Oceanic Crust - Crust, usually thinner than continental crust, that forms the sea floor. It is on average 7km thick.
• Mid-Ocean Ridge - Parting oceanic plates at a constructive plate boundary creates a ridge, with new land at the base of the oceanic valley.
• Pyroclastic Flow - A mixture of gases and rock fragments, at high temperatures travelling at rapid speeds.
• Primary Waves - An earthquake wave causing compressions within the body of rock.
• Rayleigh Waves - A surface earthquake wave causing both horizontal and vertical displacement. Richter Scale - A logarithmic measure of earthquake’s intensity.
• Secondary Waves - An earthquake wave causing vertical displacement within the body of rock.
• Subduction - Oceanic plate is forced below continental plate, due to the oceanic plate being more dense than the continental plate.
• Surface Fires - Wildfires that only burn the leaf litter, and so are the easiest kind to extinguish.
• Tropical Storm - A low pressure system of spiralling winds (due to the Coriolis Effect). Also called hurricanes, cyclones, and typhoons depending on the location they occur in.
• Tsunami - Initial vertical water displacement (often from a submarine earthquake) creates waves, with large destructive power.
• Volcanic Explosivity Index (VEI) - A measure of the magnitude of a volcano’s eruptions.
• Wildfire - A large, uncontrolled fire that quickly spreads through vegetation.
• Wadati-Benioff Zone - A region of the subducting plate, most affected by pressure and friction, where most destructive margin earthquakes originate.