General Hazards

• 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
• 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
• 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 (carbon dioxide, methane, water vapour and nitrous oxides)
• 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
• 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 (hours, days, and potentially a week or so after the event)
• 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 (weeks, months, and years after the event)
• Magma

  Molten rock found beneath the Earth's surface
• Mantle


  The area underneath the crust which contains magma
• 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 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 point at which two plates meet
• Pressure belt


  A region of the Earth which is generally under the same pressure
• 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
• 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, forcing it to sink into the asthenosphere
• Tectonic hazard

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