Definitions

• 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, along with air travelling from the equator.
• 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, which is 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. Radioactive decay within the inner core provides Earth’s internal energy
• 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. The top of the lithosphere is the crust, which is broken up into tectonic plates.
• 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.
• 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.
• Obliquity (or axial tilt) 


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


  A naturally occurring event that is a threat to a population.
• Outer core 


  A molten layer of iron and nickel that surrounds the inner core and transfers energy by convection currents.
• 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.