RE+-+Glossary

Crust:the outer layer of the earth Plate: a section of the earth's crust Plate margin: the boundary where two plates meet Mantle: the dense mostly solid layer between the outer core and the crust Convection currents: the circular currents of heat in the mantle Subduction: the sinking of oceanic crust at a destructive plate margin Collision: the meeting of two plates of continental crust. They are both the same type so they meet 'head on' and buckle Fold mountains: large mountain ranges where rock layers have been crumpled as they have been forced together Ocean trenches: deep sections of the ocena, usually where an oceanic plate is sinking below a continental plate Composite volcano: a steep-sided volcano that is made up of a vairety of materials, such as lava and ash Shield volcanoes: a broad volcanoe that is mostly made up of lava Subsistence: farming to provide food and other resources for the farmer's own family Terraces: steps cut into hillsides to create areas of flat land Irrigation: artificial watering of the land Hydroelectric power: the use of flowing water to turn turbines to generate electricity Natural hazard: an occurence over which people have little control, which poses a threat to people's lives and possessions. This is different from a natural event as volcanoes can erupt in unpopulated areas without being a hazard Primary effects: the immediate effects of the eruption, caused directly by it Secondary effects: the after-effects that occur as an indirect effect of the eruption on a longer timescale Aid: money, food, training and technology given by richer countries to help poorer ones, either to help with an emergency or to encourage long-term development Earthquake: a sudden and often violent shift in the rocks forming the earth's crust, which is felt at the surface Immediate responses: how people react as the diaster happens and in the immediate aftermath Long-term responses: later reactions that occur in the weeks, months and years after the event Vent: the opening - usually central and single - in a volcano from which magma is emitted Lahar: these secondary effects of a volcanic eruption are mudflows resulting from ash mixing with melting ice or water Supervolcano: a mega colossal volcano that erupts at least 1,000km cubed of ash Caldera: the depression of the supervolcano marking the collapsed magma chamber fissures: extended openings along a line of weakness that allow magma to escape Geothermal: water that is heated beneath the ground, which comes to the surface in a variety of ways Geyser: a geothermal feature in which water erupts into the air under pressure Hot spot: a section of the earth's crust where plumes of magma rise, weakening the crust, These are away from plate boundaries Focus: the point in the earth's crust where the earthquake originates Richter scale: a logarithmic scale used for measuring earthquakes, based on scientific recordings of the amount of movement Epicentre: the point at the earth's surface directly above the focus Shock waves: seismic waves generated by an earthquake that pass through the earth's crust Mercalli scale: a means of measuring earthquakes by describing and comparing the damage done, on a scale of I to XII Debt: money owed to other, to a bank or to a global organisation such as the world bank The three Ps: the collective term for prediction, protection and preparation Prediction: attempts to forecast an event - where and when it will happen - based upon current knowledge Protection: constructing buildings so that they are safe to live in and will not collapse Preparation: organising activities and drills so that people know what to do in the event of an earthquake Tsunami: a special type of wave where the entire depth of the sea or ocean is set in motion by an event, often an earthquake, which displaces the water above it and creates a huge wave