hazard definitions Flashcards
Accretion Wedge
The accumulation of material at the point of subduction.
Aseismic Buildings
Buildings designed to withstand or minimise destruction during an
earthquake.
Asthenosphere
The upper mantle layer of the Earth. It is semi-molten and approximately 2000km
wide.
Ash
Fine particles and dust ejected during an eruption, which can remain airborne as clouds or
accumulate on the ground.
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.
Controlled Burning
Intentionally burning vegetation with the aim of reducing fuel available for a
wildfire and disrupting the fire’s path
Continental Crust
Crust that forms the continents of the lithosphere, on average 35km thick.
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.
Crown Fires
Wildfires that burn the entirety of a tree (from top to bottom), often the most
destructive and dangerous type of wildfire.
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.
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.
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.
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.
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.
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.
Park’s Model
A model describing the decline and recovery of a country over time, following a natural disaster.
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.
Richter Scale
A logarithmic measure of earthquake’s intensity.
Pyroclastic Flow
A mixture of gases and rock fragments, at high temperatures travelling at rapid
speeds.
Rayleigh Waves
A surface earthquake wave causing both horizontal and vertical displacement.
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.
Volcanic Explosivity Index (VEI)
A measure of the magnitude of a volcano’s eruptions.
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 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
