Glossary of Definitions - Hazardous Earth

A comprehensive glossary of terms and definitions related to hazardous Earth science.

Asthenosphere

The semi-molten layer at the top of the mantle which flows due to convection currents, moving the solid lithosphere above.

Atmospheric circulation

The general movements of air around the Earth due to pressure and temperature.

Climate change

A distinct change in global or regional patterns of climate, such as changes in temperature or precipitation patterns.

Conservative plate boundary

A plate boundary where two plates are moving alongside each other.

Continental crust

The thicker, less dense crust that makes up the continents.

Convection current

The movement of a fluid caused by a difference in temperature or density.

Convergent plate boundary

A plate boundary where two plates are moving towards each other.

Coriolis Effect

The effect of the Earth’s rotation on wind movements.

Cyclone

A tropical cyclone that hits Oceania or Madagascar.

Divergent plate boundary

A plate boundary where two plates are moving away from each other.

Eccentricity

The changing of the orbit of the Earth around the Sun from a circular shape to an ellipse.

Eye

An area of a tropical cyclone with extremely low pressure and calm conditions.

Eyewall

An area of a tropical cyclone with the most intense, powerful winds and torrential rain.

Ferrel Cell

At around 60° either side of the equator, moist air rises, and travels to lower latitudes at around 30° where it sinks.

Fossil fuels

Fuels made up of the remains of organic material, such as oil, coal and gas.

Geological hazard

A hazard caused by processes on the land.

Greenhouse Gases

Gases in the Earth’s atmosphere that trap energy in the Earth’s system and contribute to the greenhouse effect.

Hadley Cell

At the equator, hot moist air rises, moves to higher latitudes (30°) and sinks.

Hazard risk

The probability that a natural hazard will negatively affect a population.

Hotspot

An area where unusually hot magma breaks through the middle of a plate and travels up to the surface, creating a volcano.

Hurricane

A tropical cyclone that hits the USA, Latin America or the Caribbean.

Ice core

A cylinder of ice extracted from an ice sheet or glacier, used to analyse past environmental conditions.

Immediate responses

Actions taken as soon as the hazard happens and in its immediate aftermath.

Inner core

A solid ball of iron/nickel at the Earth’s centre.

Inter-Tropical Convergence Zone (ITCZ)

An area surrounding the equator where global winds converge, causing an area of low pressure with rainy conditions.

Lithosphere

Solid rock that lies on top of the asthenosphere.

Long-term responses

Actions taken after the immediate responses when the effects of the hazard have been minimised.

Magma

Molten rock found beneath the Earth’s surface.

Mantle

The area underneath the crust which contains magma.

Milankovitch Cycles

The cyclical variations in the Earth’s orbit around the Sun.

Natural hazard

A naturally occurring event that is a threat to a population.

Obliquity (or axial tilt)

The tilt of the Earth’s axis, which changes from 21.5° and 24.5°.

Ocean currents

The predictable, continuous circulation of ocean water which transfers heat around the globe.

Oceanic crust

The thinner, denser crust that makes up the ocean floor.

Outer core

A molten layer of iron and nickel that surrounds the inner core.

Plate boundary

The point at which two plates meet.

Polar Cell

At 60° north or south of the equator, moist air rises, and travels to the poles (90°), where it sinks.

Precession

The ‘wobble’ of the Earth’s axis.

Pressure belt

A region of the Earth which is generally under the same pressure.

Primary effects

The effects that are directly caused by the hazard itself.

Quaternary Period

The geological time period that started 2.6 million years ago and extends into the present.

Richter scale

A logarithmic scale used to measure the magnitude of earthquakes.

Secondary effects

The effects that are a result of the primary effects.

Storm surge

A rise in sea level caused when a tropical cyclone pushes a large amount of sea water onto the shore.

Subduction

A process that occurs at a destructive plate boundary when a plate is pushed below another plate.

Tectonic hazard

A natural hazard caused by the physical processes and movements of tectonic plates.

Tectonic plates

Large slabs of the Earth’s crust that sit and move on top of the liquid mantle.

The Enhanced Greenhouse Effect

A process where the Earth’s surface is heated by the greenhouse effect at a higher rate due to increased greenhouse gas emissions.

The Greenhouse Effect

A natural process where greenhouse gases trap the energy from the Sun inside the Earth’s atmosphere.

Track

A typical pathway that a tropical cyclone takes which is driven by global wind circulation.

Tree rings

A ring in a tree trunk that grows annually, indicating the conditions in the year it grew.

Tropical cyclone

A very large, spinning storm with high winds and torrential rain that forms in the tropics.

Tsunami

A large wave caused by a large amount of water being displaced when plates move.

Typhoon

A tropical cyclone that hits India, Japan or the Philippines.