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Ash Small particles of solid material blasted out of a volcano when it erupts.
Asthenosphere A relatively weak layer in the mantle immediately below the lithosphere.
Biological weathering The breakdown of rock material brought about by the action of plants and animals, eg by growth of tree roots, by acid produced by lichens etc.
Batholith A very large mass of intrusive igneous rock, many cubic kilometres in volume.
Biomass The total dry mass of an animal or plant population.
Borehole A hole in the Earth’s crust, produced by drilling from a rig.
Cement A material that helps the binding of rock, mineral and / or fossil fragments together by precipitation of minerals from water in the pores of the sediment to form a harder sedimentary rock.
Cementation The action of binding rock, mineral and / or fossil fragments together by crystallisation of minerals from water in the pores of the sediment to form a harder sedimentary rock.
Cementing The action of binding rock, mineral and/or fossil fragments together by crystallisation of minerals from pore waters to form a harder sedimentary rock.
Cementing agent A material that helps the binding of rock, mineral and/or fossil fragments together by crystallisation of minerals from pore waters to form a harder sedimentary rock.
Chalk A soft white limestone, composed of the calcium carbonate remains of minute organisms (mostly from planktonic algae).
Chemical weathering The breakdown of rock material brought about by the action of chemicals, usually in aqueous solution.
Calcareous Containing calcium carbonate.
Calcareous algae Simple plants which can extract calcium carbonate from dissolved carbonates in water, and use it to build their ‘skeletons’.
Carbohydrates A group of compounds containing carbon, hydrogen and oxygen which, when they are oxidised, provide energy.
Carbon Element, symbol C. Carbon compounds are the basis of all living matter.
Carbon cycle The movement of carbon through the surface, interior and atmosphere of the Earth.
Carbon dioxide Gas containing carbon and oxygen, present in the atmosphere, and given off by volcanoes.
Carbon sink A component of the Earth system that absorbs carbon compounds, otherwise known as a reservoir or pool, eg the ocean.
Charcoal Solid carbon-rich residue derived from incomplete burning of organic material.
Climatic cycle Changes in the environment brought about by the changes in the climate.
Coal Carbon-containing rocks, derived from plant remains altered by increased pressure and temperature and various chemical processes. A fossil fuel.
Collision zone Another name for a destructive plate margin, ie the region on the Earth’s surface where two tectonic plates meet as they move towards each other.
Compound A substance made of up two or more elements chemically combined.
Conglomerate A sedimentary rock consisting of rounded pebbles of rock fragments in a matrix of smaller particles and cement.
Constructive margin A junction between two tectonic plates where they are moving apart.
Contact metamorphism The processes by which solid rocks are altered by increased temperatures when they are close to a hot igneous body, such as an intrusion of granite.
Convection current Movement of material under the influence of heat. It is believed that very slow convection in the solid rocks of the Earth’s mantle can move the plates above.
Contact metamorphic rocks Rocks which are altered and changed into a different crystal form in the solid state by the action of heat from a nearby hot igneous body.
Core The innermost parts of the Earth, lying between 2900 km depth and the centre of the Earth at over 6300 km depth.
Country rock Rock which is already in place before being intruded by a hot magma.
Cross-cutting One geological feature that cuts across an earlier one, and can be used to establish relative dates, eg an igneous dyke cutting through older sedimentary rocks.
Crust The part of the Earth lying above the mantle. It is thickest below mountains and thinnest below oceans.
Dendroclimatologist A scientist who uses the patterns of the rings in tree trunks to work out changes in the climate during the lifetime of the tree.
DNA Deoxyribonucleic acid, a polynucleotide containing the sugar deoxyribose – it contains the information needed by a cell to make proteins.
Dolerite A dark igneous rock of medium grain size which is relatively rich in iron and magnesium minerals.
Ductile Capable of being drawn out; of low rigidity and so able to flow slowly.
Earth's magnetic field The area around the Earth where a magnetic force can be detected. It is thought to be due to fluid motion within the liquid outer core of the Earth.
Earthquake A sudden release of energy caused by rock material breaking under stress. Shock waves transmit the energy from the focus of the fracture to the surface.
Element One of the 100 or so chemical substances that cannot be decomposed into anything simpler.
Emissions Gases that are produced by a variety of sources and are given off to the atmosphere.
Epicentre The point on the Earth’s surface directly above the focus of an earthquake.
Erosion A process in which rocks are worn away by mechanical action (associated with water, wind, ice or gravity).
Extrusive Produced by volcanic activity.
Extrusive igneous rocks Rocks which have been produced by the solidification of hot magma at the Earth’s surface, eg lavas, volcanic glass and volcanic ashes.
Fault A fracture in rocks, where the rocks on one side of the fracture have moved relative to those on the other side.
Faulting The processes by which rocks fracture under stress, and move relative to rocks on the other side of a fracture.
Folding Processes whereby rocks are bent, ie deformed in a relatively plastic state.
Fossil fuel Fuels formed from the remains of plants or animals by increases in pressure and temperature and by biological and chemical processes.
Freeze-thaw The repetitive action of alternate freezing and thawing of water in cracks, resulting in the breakdown of rock masses.
Gabbro A dark igneous rock of coarse grain size, which is relatively rich in iron and magnesium minerals.
Global warming The increase in temperature of the Earth – a possible factor is the increase in greenhouse gases due to human activities.
Gneiss A coarse-grained metamorphic rock, where the minerals occur in bands. Some gneisses are produced by the regional metamorphism of an original shale or mudstone; others represent igneous rocks that have been metamorphosed.
Graded bedding The arrangement of the particles in a sediment, with larger ones at the base, passing gradually upwards into finer grain sizes.
Granite

A pale coloured igneous rock of coarse grain size, which is relatively rich in silicates such as quartz, feldspar and mica.

Granitic Like granite. Can be applied to an igneous rock, or as a general chemical description of a magma rich in silica, which could crystallise to from granite or any of its finer grained equivalents.
Greenhouse effect The heating of the atmosphere by the trapping of long-wave radiation re-emitted by the Earth from incoming solar energy.
Greenhouse gas A gas that traps / absorbs long-wave radiation emitted by the Earth
Hydroacoustic Refers to a series of specialised microphones placed in water.
Igneous rock Rocks that have cooled and solidified from molten rock (magma).
Igneous intrusion A body of rock that has formed by the solidification of magma below ground after being intruded into the surrounding rock.
Infrasound Sound of such low frequency that it falls outside the human range of hearing.
Intrusion A body of igneous rock that was forced, as a liquid, into pre-existing rocks, it is always younger than the rock it has cross-cut.
Intrusive Adjective applied to the ways in which magmas can force their way into older rocks and cool to form intrusive igneous rocks.
Intrusive igneous rocks Igneous rocks that have cooled and solidified from a magma below ground, eg granite.
Lava Molten rock that is extruded (forced out) from a volcano.
Lime Calcium oxide, produce by heating limestone (calcium carbonate).
Limestone A sedimentary rock consisting largely of calcium carbonate. May be formed from calcareous skeletal remains.
Lithosphere The strong, rigid outermost layer of the Earth. It is composed of the crust, plus the outermost 100 km or so of the mantle.
Magma A largely molten fluid formed within the crust or upper mantle that may solidify to form an igneous rock.
Magma chamber A space in the Earth’s crust or mantle which contains a volume of molten rock, ie magma.
Mantle The portion of the Earth's interior lying below the crust and above the core - it is mostly solid.
Metamorphic aureole The zone in the country rock around an igneous body, where the effects of the heat have altered (metamorphosed) the existing rock, but without melting it.
Metamorphic rock Rock which has been altered and changed in crystalline form, in the solid state, by the effects of heat and / or increased pressure.
Metamorphism The process by which existing rocks of any origin are altered and changed in crystalline form in the solid state by the action of heat and / or increased pressure.
Microgranite A pale coloured igneous rock of medium grain size, which is relatively rich in silicates such as quartz, feldspar and mica.
Mineral A naturally occurring chemical compound of definite chemical composition and atomic structure. Minerals are the ‘building blocks’ of rocks: others occur as economic materials in their own right.
Mudstone A sedimentary rock formed from very small particles, mainly of clay minerals. The particles are less than 0.004 mm in diameter.
Normal magnetism Rocks may be magnetised by the Earth’s field. When the magnetisation in a rock is in the same direction as the Earth’s field of today, we call it ‘normal’.
Oceanic ridge A significant rise on the ocean floor, forming a long, linear ridge, often 4 km or so above the general level of the deep ocean floor. Oceanic ridges are associated with constructive plate margins.
Orogeny A period of intense mountain building.
Outer core The liquid part of the Earth’s core, lying between about 2900 km and 5100 km depth.
P-wave A longitudinal shock wave, produced by fracture of rocks at the focus of an earthquake. They travel faster than S-waves.
Palaeoclimatic Relating to the climate of former times, usually as deduced from the evidence of the rocks and fossils.
Photosynthesis The use of light energy to drive chemical reactions resulting in the conversion of carbon from carbon dioxide into carbohydrates.
Physical weathering Breakdown of rock material by mechanical processes, including freeze-thaw, heat-cold, wetting-drying etc.
Plankton Minute organisms floating in the seas, rivers, ponds, lakes as distinct from those which are attached or crawl upon the bottom.
Planktonic algae Simple plant life, usually microscopic, which floats or swims near the surface of the sea or lakes.
Plate A large rigid slab of lithosphere, distinguished from neighbouring plates by frequent earthquake activity along its edges.
Plate margin The boundary of a tectonic plate. Margins are defined by frequent earthquake activity, mostly, but not always, accompanied by volcanic activity.
Plate tectonics A theory explaining slow movements of parts of the Earth's outer surface (lithosphere) known as plates. This movement is associated with convection currents in the largely solid mantle. The theory explains both recent and remote events in Earth's history.
Pumice Lava which has been ‘frothed up’ by gases given off as a volcanic eruption takes place.
Radionuclide A radioactive isotope of an element.
Regional metamorphism The alteration of existing rocks by the effects of heat and increased pressure acting together.
Respiration The release of energy from organic compounds in living cells.
Reversed magnetism Rocks may become magnetised by the Earth’s field. When the magnetisation in a rock is in the opposite direction to the Earth’s field of today, it is called ‘reversed’.
Rhyolite A pale coloured igneous rock of fine grain size, which is relatively rich in silicates such as quartz, feldspar and mica. Most rhyolites form as lavas, and may show complex flow banding.
Rock cycle A concept whereby rocks are thought of as being recycled repeatedly, eg from sediment to sedimentary rock to metamorphic rock to igneous rock etc.
S-wave A transverse shock wave, produced by fracture of rocks at the focus of an earthquake. They travel more slowly than P-waves.
Sandstone A sedimentary rock formed from sand-sized particles.
Schist A rock produced by the regional metamorphism of an original shale or mudstone. It is medium grained and ‘shiny’ in appearance, produced by the sub-parallel arrangement of tiny mica crystals.
Sea floor spreading The processes whereby new material rises from the mantle beneath the oceanic ridges and is added to the crust above.
Seasonal cycle Changes in the environment brought about by the changes in the seasons- winter, spring, summer, autumn.
Sediment Deposited material including particles formed by the weathering and erosion of pre-existing rock and particles of chemical and biological origin.
Sedimentary rock Rocks such as sandstone, and conglomerate that are composed of compacted and cemented fragments of older rocks. Some sedimentary rocks (eg limestone) are of organic or chemical origin.
Seismic waves Waves that pass through or around the Earth caused by an earthquake.
Seismogram The record (electronic or on paper) of the output of a seismometer (a device for measuring seismic waves).
Seismology The study of earthquakes and the evidence they provide about the interior of the Earth.
Seismometer An instrument for measuring seismic waves generated by earthquakes or man-made explosions.
Sequence The order in which rocks occur, eg one sedimentary layer on top of another, or an igneous intrusion cutting across older rocks etc.
Shadow zone An area of the Earth’s surface where seismic waves are not recorded, although it is known that an earthquake has occurred on the other side of the globe.
Shale A type of sedimentary rock made from very small particles, (less than 0.004 mm in diameter), which form closely spaced layers. Shale splits easily along these layers.
Shear waves Same as S-waves.
Sheet lava flow A widespread sheet of lava, many metres thick, formed when a very mobile lava such as basalt erupts, especially from fissure eruptions.
Solution A mixture (usually of a solid in a liquid in which the components are mixed at the molecular level).
Subduct The processes whereby one plate is pulled down beneath another, probably driven by convection currents below.
Subduction zone A zone in the Earth’s crust and mantle, where one tectonic plate is being pulled down beneath another, less dense, one.
Superposition Where two or more beds of rock lie one above the other, the uppermost bed is normally the younger. This is known as the Principle of Superposition.
Surface wave A seismic wave which travels around the outer surface of the Earth, but which does not pass through the Earth.
Sustainability Whether or not a resource can be exploited without it running out.
Sustainable development The exploitation of a resource in such a way that it can be replaced within a reasonable time scale (in human terms).
Tectonic plate A large rigid slab of lithosphere, distinguished from neighbouring plates by seismic activity along its edges.
Texture The grain size of a rock, the shapes of the grains and the ways in which they are arranged.
Transport The movement of sedimentary material. The main agents are the sea, wind, ice, running water and gravity.
Transportation Same as transport.
Tree ring Seasonal growth in trees results in concentric rings being formed in the trunk, where each ring represents a summer or a winter season.
Volcanic bomb A blob of lava which is shot out of a volcano and falls back to the surface as a solidifying mass May be up to several cubic metres in diameter.
Volcano A feature in the Earth's crust through which molten magma, volcanic ashes and hot gases escape. It may be on land or under the sea.
Weather The conditions resulting from a combination of all atmospheric processes operating at one time in any one place.
Weathering The processes by which rocks are broken down by physical, chemical or biological processes in such a way that no movement of solid materials away from the site takes place. The movement away of solid materials is erosion.