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.
Glossary