hazardous environments vocabs

Natural hazard

A natural event, such as an earthquake or flood, that has the potential to cause damage or harm.

Natural disaster

Occurs when people, property, or businesses are actually affected by natural hazards, resulting in human or economic loss.

Magnitude

A measurement of the strength or power of a hazard event.

Frequency

How often a specific hazard event occurs in a given area.

Duration

The length of time a hazard event lasts, such as a long-term drought or short-term flash flood.

Geophysical hazards

Hazards caused by processes occurring within or on the surface of the Earth, including tectonic and geomorphological events.

Tectonic hazards

A subtype of geophysical hazard caused specifically by the movements of the Earth's plates, such as earthquakes and volcanoes.

Hydrological hazards

Hazards caused by the movement or distribution of water, such as floods.

Meteorological hazards

Hazards caused by short-term weather events, like storms or tornadoes.

Atmospheric hazards

Hazards related to the weather and atmosphere, including extreme temperatures and tropical cyclones.

Climatological hazards

Hazards caused by long-term climate conditions, such as drought.

Biological hazards

Hazards caused by living organisms, including pests, insects, and disease epidemics.

Crust

The solid outer layer of rock on the Earth's surface, varying in thickness from approximately 5km to 100km.

Mantle

The semi-liquid layer of molten rock (magma) located between the crust and the core, which moves due to convection currents.

Outer Core

The liquid portion of the Earth's core.

Inner Core

The solid centre of the Earth, composed primarily of iron and nickel, with temperatures reaching 5,500°C.

Lithosphere

The rigid outer part of the Earth, consisting of the crust and the very top of the upper mantle.

Oceanic Crust

A thinner, denser type of crust (mainly basalt) that is younger and capable of sinking into the mantle.

Continental Crust

A thicker, lighter type of crust (mainly granite) that is older and cannot sink.

Convection currents

The cycle of heating, rising, cooling, and sinking of magma in the mantle that drives the movement of tectonic plates.

Plate boundary (Margin)

The edge or limit where two tectonic plates meet.

Constructive (Divergent) margin

A boundary where plates move away from each other, allowing magma to rise, cool, and form new crust.

Destructive (Convergent) margin

A boundary where plates move towards each other, and the denser oceanic plate is forced down into the mantle.

Subduction

The process at a destructive margin where a denser plate sinks beneath a less dense plate.

Collision margin

A type of convergent boundary where two continental plates of similar density collide, forcing the land upwards to form fold mountains.

Conservative (Transform) margin

A boundary where plates slide past each other in opposite directions or at different speeds, creating friction and pressure.

Ridge push

A process at constructive margins where gravity causes new, elevated lithosphere to slide down and away from an ocean ridge.

Slab pull

A process at destructive margins where the weight of a cold, dense subducting plate pulls the rest of the plate down into the mantle.

Hotspot

A plume of magma that escapes through the Earth's crust in the middle of a tectonic plate rather than at a boundary.

Focus

The specific point below the surface where an earthquake originates.

Epicentre

The point on the Earth's surface directly above the focus.

Seismic waves

Energy released from an earthquake that travels through the Earth's crust in the form of ripples or vibrations.

Fault

A weakness or crack in the Earth's rock structure where pressure builds and plates eventually jolt free.

Richter Scale

A logarithmic scale used to measure the magnitude or energy released by an earthquake.

Mercalli Scale

A scale used to measure the intensity and damage of an earthquake based on qualitative observations.

Seismometer

An instrument that detects and measures the vibrations caused by an earthquake.

Soil liquefaction

A secondary hazard where violent shaking causes water-saturated soil to lose its strength and behave like a liquid.

Magma

Molten rock found beneath the Earth's surface.

Lava

Molten rock that has broken through the Earth's surface during an eruption.

Volcanic Explosivity Index (VEI)

A scale from 0 to 8 used to measure the explosiveness and magnitude of a volcanic eruption.

Viscosity

The thickness or stickiness of lava; high-viscosity lava is thick like toothpaste, while low-viscosity lava is runny like water.

Shield volcano

A wide, gently sloping volcano formed by runny lava, typically found at constructive margins or hotspots.

Composite volcano (Stratovolcano)

A tall, steep-sided volcano made of layers of ash and lava, typically found at destructive margins and known for violent eruptions.

Tephra

All fragments of rock and debris ejected into the air by an erupting volcano.

Pyroclastic flow

A fast-moving, extremely hot (up to 700°C) current of gas and ash that destroys everything in its path.

Lahar

A secondary hazard consisting of a volcanic mudflow.

Magma chamber

A large underground pool of liquid rock found beneath a volcano.

Vent

An opening in the Earth's surface through which volcanic materials escape.

Tropical cyclone

A huge, rotating low-pressure storm system that forms over warm tropical waters (also called hurricanes or typhoons).

Storm surge

A rising of the sea as a result of atmospheric pressure changes and wind associated with a storm.

Coriolis force

The force caused by the Earth's rotation that helps tropical cyclones to spin.

Eye

The calm, cloudless centre of a tropical cyclone.

Drought

A prolonged period of abnormally low rainfall, leading to a water shortage.