Hazards - key AQA terms in the exam specification

Natural hazard

A naturally occurring physical event that has the potential to cause loss of life, injury, damage to property, economic disruption, or environmental degradation.

Geophysical hazard

A natural hazard originating from processes within the Earth's crust, such as earthquakes, volcanic eruptions, and tsunamis.

Atmospheric hazard

A natural hazard caused by atmospheric processes, including tropical storms, heatwaves, droughts, and severe weather events.

Hydrological hazard

A hazard resulting from the movement, distribution, or storage of water, including river flooding, storm surges, and rainfall-triggered landslides.

Lithosphere

The rigid outer layer of the Earth, consisting of the crust and upper mantle, divided into tectonic plates.

Atmosphere

The layer of gases surrounding the Earth that controls weather and climate and protects life from harmful solar radiation.

Geospatial mapping

The use of geographic data and technologies such as GIS and remote sensing to represent, analyse, and interpret the spatial distribution of hazards.

Hazard nature

The inherent physical characteristics of a hazard, including its causes and processes.

Hazard form

The specific physical expression of a hazard, such as lava flows, floodwaters, or seismic waves.

Hazard perception and its economic and cultural determinants

The way hazards are understood and responded to by individuals or communities, influenced by income, education, experience, beliefs, and cultural values.

Human responses to hazards

Strategies used to reduce hazard impacts, ranging from acceptance of risk (fatalism) to scientific forecasting, behavioural change, physical protection, coordinated planning, and the spreading of financial risk.

Short-term responses to hazards

Immediate actions taken during or shortly after a hazard event, such as emergency services, evacuation, and humanitarian aid.

Long-term responses to hazards

Measures implemented over months or years to reduce future risk and rebuild communities, including reconstruction, policy changes, and education.

Hazard incidence

The number of hazard events occurring in a given area over a specific period of time.

Hazard intensity

The severity of a hazard at a particular location, such as ground shaking strength or wind speed.

Hazard magnitude

The total energy released by a hazard event, often measured using logarithmic scales.

Hazard frequency

How often a hazard occurs in a particular area.

Hazard distribution

The spatial pattern of hazard occurrence across the Earth's surface.

Hazard predictability

The extent to which the timing, location, and magnitude of a hazard can be forecast accurately.

Hazard regularity

The degree to which hazards occur at consistent or predictable intervals.

Hazard resilience

The ability of people or systems to absorb, recover from, and adapt to hazard impacts.

Risk

The likelihood of a hazard occurring combined with the potential severity of its impacts.

Country level of development

The extent of a country's economic, social, and technological progress, commonly measured using indicators such as HDI and GNI.

Park model

A model illustrating changes in quality of life before, during, and after a hazard event and the speed of recovery.

Hazard Management Cycle

A model outlining the stages of hazard management: mitigation, preparedness, response, and recovery.

Hazard preparedness

Actions taken before a hazard event to ensure effective response, such as planning, training, and early warning systems.

Hazard mitigation

Measures aimed at reducing the severity or impact of hazards.

Hazard prevention

Actions designed to stop a hazard from occurring, where possible.

Hazard adaptation

Long-term adjustments to reduce vulnerability to hazards.

Earth structure

The layered composition of the Earth, including the crust, mantle, outer core, and inner core.

Earth internal energy sources

Heat from radioactive decay and residual heat from Earth's formation that drives tectonic processes.

Plate tectonic theory of crustal evolution

The theory that the Earth's crust is divided into moving plates whose interactions shape landforms and cause hazards.

Tectonic plates

Large sections of the lithosphere that move slowly over the asthenosphere.

Plate movement

The motion of tectonic plates driven by internal Earth energy.

Gravitational sliding

The downslope movement of tectonic plates under the influence of gravity.

Ridge push

A force caused by the elevated position of mid-ocean ridges, pushing plates apart.

Slab pull

The force exerted by a dense, subducting plate sinking into the mantle.

Convection currents

The circular movement of heated mantle material that transfers energy and drives plate motion.

Sea-floor spreading

The formation of new oceanic crust at constructive plate margins as magma rises and solidifies.

Destructive plate margin

A plate boundary where plates converge and one is subducted, generating earthquakes and volcanoes.

Constructive plate margin

A boundary where plates diverge and new crust is created.

Conservative plate margin

A boundary where plates slide past each other without crust being created or destroyed.

Seismicity

The frequency and distribution of earthquakes.

Vulcanicity

The movement of magma and gases from the mantle to the Earth's surface.

Young fold mountains

Mountain ranges formed by compression at convergent plate boundaries.

Rift valleys

Linear depressions formed where the crust is pulled apart at divergent margins.

Ocean ridges

Submarine mountain chains formed at constructive plate boundaries.

Deep sea trenches

Long, narrow ocean depressions formed at subduction zones.

Island arcs

Chains of volcanic islands formed above subduction zones.

Volcanoes

Openings in the Earth's crust through which magma, ash, and gases erupt.

Magma plumes and their relationship to plate movement

Columns of rising hot mantle material that cause hotspot volcanism independent of plate boundaries.

Volcanic hazards

Primary and secondary dangers associated with volcanic activity.

Nuées ardentes

Fast-moving, superheated pyroclastic flows of gas and ash.

Lava flows

Streams of molten rock that destroy infrastructure and land.

Mudflows (lahars)

Rapid flows of volcanic ash mixed with water, often following eruptions.

Pyroclastic and ash fallout

Volcanic material ejected into the atmosphere that later settles on the Earth's surface.

Volcanic gases and acid rain

Gases such as sulphur dioxide released during eruptions that can cause air pollution and acidic precipitation.

Tephra

All solid volcanic material ejected during an eruption.

Primary impact

The immediate effects of a hazard event.

Secondary impact

Indirect effects that result from primary impacts.

Environmental, social, economic and political impacts

The effects of hazards on ecosystems, populations, economies, and governance.

Seismic hazards

Hazards caused by the sudden release of energy in the Earth's crust.

Earthquakes

Sudden ground movements caused by stress release along faults.

Shockwaves

Seismic waves that transmit earthquake energy through the Earth.

Tsunamis

Large ocean waves generated by underwater seismic activity.

Liquefaction

The loss of soil strength when saturated ground behaves like a liquid during shaking.

Landslides

The downslope movement of rock, soil, or debris due to gravity.

Tropical storm

A large rotating storm system that forms over warm oceans and produces strong winds and heavy rainfall.

Storm hazards

The damaging effects associated with storm systems.

High winds

Strong atmospheric air movement capable of causing structural damage.

Storm surge

A rise in sea level caused by storm winds and low atmospheric pressure.

Coastal flooding

The inundation of coastal land by seawater.

River flooding

The overflow of rivers onto surrounding land. A secondary hazard associated with tropical storms.

Wildfires

Uncontrolled fires that spread through natural vegetation.

Pyrophytic vegetation

Plant species adapted to survive or regenerate after fire e.g. chaparral vegetation like Chamise.

Fire behaviour

The manner in which a fire spreads and intensifies, influenced by fuel, weather, and topography.

Causes of fires

Natural or human factors that ignite wildfires. 3 conditions are needed for wildfires: fuel, ignition and key atmospheric conditions (hot, dry and windy)

Multi-hazardous environments

Areas exposed to more than one type of natural hazard.

Economic, social and political community character

The characteristics of a population that influence vulnerability and resilience, including wealth, inequality, governance, and social cohesion.

Pyroclastic flow

A fast-moving, superheated avalanche of volcanic ash, rock fragments (tephra), and gas that rushes down a volcano's slopes, capable of reaching hundreds of kilometers per hour and temperatures up to 1000°C (1800°F)