Hazards: Key Words Flashcards
Acid dome volcanoes
Steep-sided convex cones associated with viscous, silica-rich gaseous lava that solidifies before running too far down slope.
Adaptation
Accepting that natural events re inevitable and adapting our behaviour accordingly.
Asthenosphere
A layer of softer, almost plastic-like rock which moves very slowly and carries the lithosphere on top.
Atmospheric hazards
Hazards driven by processes at work in the atmosphere.
Caldera
Vast pit crater formed by a violent eruption which blows off the volcano’s summit.
Composite cones (strato-volcanoes)
Formed from alternating eruptions of ash, tephra and lava, which builds up the volcano in layers, producing weaknesses that can be exploited by the magma.
Conservative plate margins
When two plates slide past each other and crust is not destroyed by subduction.
Constructive (divergent) plate margins
When two plates separate or diverge.
Core
The centre and hottest part of the Earth, made up of the outer core and inner core.
Crown fire
Wildfire which spreads across tree canopy and affects forested areas.
Crust
The Earth’s outer shell, made up of oceanic crust and continental crust.
Destructive (convergent) plate margins
When two plates collide or converge.
El Niño
A cyclical climatic condition which involves the warming of the Pacific off the west coast of South America and affects global patterns of temperature and rainfall.
Extrusive
Lava that is in contact with the air or sea, resulting in igneous rock which tends to be fine-grained with small crystals.
Eye wall
The bank of cloud which rings the central eye in a tropical storm.
Fatalism
An acceptance that hazards are natural events that we can do little to control and losses have to be accepted.
Fissure eruptions
When lava escapes through a split or crack in the rock, which can create extensive lava plateaus.
Geophysical hazards
Hazards driven by the Earth’s own internal energy sources.
Gravitational sliding
The movement of tectonic plates as a result of gravity.
Ground fire
Wildfire which burns beneath the ground layers of dry organic peat.
Hazard management cycle
A theoretical model of hazard management as a continuous 4-stage cycle involving mitigation, preparation, response and recovery.
Hot spot
An area where radioactive decay within the Earth’s core is concentrated, generating very hot temperatures and heating the lower mantle.
Hydrological hazards
Hazards driven by water bodies (mainly the oceans).
Igneous rocks
Rocks formed by the cooling of molten magma, either underground (intrusive) or on the ground surface (extrusive).
Indian Ocean Dipole (IOD)
A cyclical ocean and atmospheric phenomenon that affects the climate of countries that surround the Indian Ocean Basin.
Intrusive
Magma that cools, crystallises and solidifies slowly below the surface resulting in coarse-grained igneous rocks.
Ladder effect
The process of fires from the forest floor spreading to the tree canopy.
Lahar
Mudflow composed mainly of volcanic ash mixed with water from a crater lake, snowmelt, glacier melt or prolonged torrential rain.
Liquefaction
The jelly-like state of silts and clays resulting from intense ground shaking.
Lithosphere
The outermost solid layer of the Earth, approximately 100km thick, comprising the crust and upper mantle.
Love (L) waves
Seismic waves which travel on the surface and are the slowest waves but cause the most damage.
Magma
Molten rock, gases and liquids from the mantle accumulating in vast chambers at great pressures deep within the lithosphere.
Magma plume
A rising column of hot rock created by hot spots heating the lower mantle, creating localised thermal currents.
Mantle
The widest section of the Earth, where mainly silicate rocks are in a thick, liquid state, which becomes denser with depth.
Mid-ocean ridges
Chains of submarine mountain ridges that extend for thousands of km across the ocean floor, caused by oceanic divergence.
Mitigation
Actions aimed at reducing the severity of an event and lessening its impact which can involve direct intervention of post-event support in the form of aid insurance.
Nuée ardente
Another name doe pyroclastic flows which have resulted from the collapse of a lava dome.
Palaeomagnetism
The study of the Earth’s magnetic field in rocks.
Prediction
Attempts to use technology to work out if a potential activity may lead to a disaster and need to be acted upon.
Preparedness
Increasing people’s awareness of the potential hazards associated with storms, wildfires etc. and through their actions minimising the likely impact of the hazard.
Prevention
Actions aimed at preventing large-scale events from starting.
Primary or pressure (P) waves
The fastest seismic waves and the ones that reach the surface first.
Pyroclastic flows
The result of the bursting of has bubbles within the magma during a volcanic eruption. Lava is fragmented and a dense cloud of fragments is thrown out.
Rayleigh (R) waves
Seismic waves which radiate from the epicentre in complicated low-frequency rolling motions.
Ridge push
The higher elevation at a mid-ocean ridge causes gravity to push the lithosphere that is further from the edge.
Rift valleys
Deep, wide valleys separates by upright blocks of land called horsts.
Saffir-Simpson scale
A scale based on sustained wind speeds, which enables storms of different magnitudes to be compared.
Sea-floor spreading
The concept that the Atlantic sea floor is spreading outwards from the centre, with the newest rocks in the middle and the oldest nearest to the USA and the Caribbean.
Secondary or shear (S) waves
Seismic waves which are half as fast as primary waves and reach the surface after primary waves.
Seismicity
The frequency and distribution of earthquakes in an area.
Shield volcanoes
Shallow-sided and broad volcanoes which are formed by relatively pure basalt that cools as it runs down from the summit crater.
Sial
Another name for continental crust - bodies of mainly granitic rocks known as sial because they are made up of silica and aluminium.
Sima
Another name for oceanic crust - an occasionally broken layer of basaltic rock known as sima because they are made up of silica and magnesium.
Slab pull
A following subduction, the lithosphere sinks into the mantle under its own weight, helping to ‘pull’ the rest of the plate with it.
Storm surge
A surge of high water, typically up to about 3m, which sweeps inland from the sea, flooding low-lying areas.
Subduction
When one plate dives beneath another and is destroyed by melting.
Submarine volcanoes
Volcanoes formed beneath the sea (either single-vent or fissure volcano), where lava is emitted along a crack in the Earth’s crust.
Supervolcano
A huge volcano that often takes the form of a caldera and is associated with massive eruptions capable of having a global impact on people.
Surface fire
Wildfire which burns across surface vegetation.
Tephra
Pyroclastic material that ranges in size from dust to blocks the size of cars.
Transform fault
A fault where two plates slide past each other, often at right angles to a divergent plate boundary.
Tropical storm
An intense low pressure system which must have an average wind speed in excess of 120km/h (75mph).
Tsunami
Waves usually generated by seismic activity such as ocean floor earthquakes of submarine volcanic eruptions.
Vulcanicity
The process of molten rich and gases extruding onto the Earth’s surface or intruding into the Earth’s crust.
Wildfire
An uncontrolled fire, either natural or human-made, that occur in open country or wilderness.
Perception
The way in which an individual or a group views the threat of a hazard event, ultimately determining the course of action taken or the response they expect
Natural hazard
Natural events or processes which are perceived to be a potential threat to people, the built environment and the natural environment
Natural disaster
Natural events or processes where the threat of harm from a hazard becomes a reality leading to social and economic losses
