Hazards

• Accretion Wedge - The accumulation of material at the point of subduction.
• Aseismic Buildings - Buildings designed to withstand or minimise destruction during an earthquake.
• 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.
• Controlled Burning - Intentionally burning vegetation with the aim of reducing fuel available for a wildfire and disrupting the fire’s path.
• Asthenosphere - The upper mantle layer of the Earth. It is semi-molten and approximately 2000km wide.
• Crown Fires - Wildfires that burn the entirety of a tree (from top to bottom), often the most destructive and dangerous type of wildfire.
• Continental Crust - Crust that forms the continents of the lithosphere, on average 35km thick.
• 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.
• 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.
• Fatalism - The belief that hazards are uncontrollable, so any losses should be accepted and mitigation is unnecessary.
• Fire Breaks - The felling of trees and clearing vegetation to create a gap to disrupt a wildfire’s path.
• 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.
• Hot Spot - Volcanoes found away from the plate boundary, due to a magma plume closer to the surface.
• Jokulhaup - A sudden glacial flood caused by a glacier on top of or near a volcano melting due to the heat from the eruption.
• Lahar - A flow of mud and debris.
• Lithosphere - The upper crust of the Earth (average thickness = 100km).
• Love Waves - A surface earthquake wave with horizontal displacement.
• Mid-Ocean Ridge - Parting oceanic plates at a constructive plate boundary creates a ridge, with new land at the base of the oceanic valley.
• Oceanic Crust - Crust, usually thinner than continental crust, that forms the sea floor. It is on average 7km thick.
• 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.
• Partial Melting - Elements within the lithosphere have different melting points, and so rock is partially melted, partially solid.
• Primary Waves - An earthquake wave causing compressions within the body of rock.
• Pyroclastic Flow - A mixture of gases and rock fragments, at high temperatures travelling at rapid speeds.
• Secondary Waves - An earthquake wave causing vertical displacement within the body of rock.
• Seismic Waves - The energy released during an earthquake, in the form of Primary, Secondary, Love and Rayleigh Waves.
• Slab Pull - The force contributing to the movement of tectonic plates. Slab pull is due to the weight of the plate.
• 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.
• 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.
• Wadati-Benioff Zone - A region of the subducting plate, most affected by pressure and friction, where most destructive margin earthquakes originate.
• Wildfire - A large, uncontrolled fire that quickly spreads through vegetation.