Glossary
- a'a
- A’a
-
Lava surface with jagged blocks
- Ablate
-
To removing atoms or ions from the surface of a solid material
- Ablation
-
Loss of ice from a glacier
- Abrasion
-
Physical weathering caused by contact between moving rock fragments and larger rock surfaces
- Absolute zero
-
The lowest possible temperature, at which molecules have no kinetic energy
- Acceleration
-
The increase in the rate of movement of an object
- Accumulation
-
Gain of ice in a glacier
- Achondrite
-
A silicate-bearing meteorite that lacks chondrules (spherical glassy fragments); achondrites
probably represent the remains of mantle material from planets in the early Solar System.
- Acid
-
Acid, acidic: having a higher concentration of hydrogen (hydronium) ions than pure water
- Acoustic impedance
-
The resistance of a substance to seismic waves passing through it; acoustic impedance is a
function of the substance’s density multiplied by the velocity of seismic waves travelling through
the material.
- Active continental margin
-
A continental margin that coincides with a plate boundary
- Active layer
-
The surface layer of sediment or rock above permafrost that thaws seasonally
An organism is described as adapted if it has traits that benefit its survival and/or reproduction.
- actualism
-
The principle that events in the past can be explained in terms of physical, chemical, or biological processes and laws that operate at the present day
- Adamantine
-
A type of lustre in which different wavelengths of light are refracted differently, typical of
diamond
- Adaptive radiation
-
The sudden evolution of a diverse array of taxa from a single clade in the wake of open niches in an ecosystem
- adiabatic
-
A change to a system is adiabatic no heat energy is gained or lost during the change
- adiabatic lapse rate
-
The rate at which air cools with elevation as it rises adiabatically (without heat transfer) within the atmosphere. The adiabatic lapse rate may be expressed in degrees per kilometre of elevation.
- Advance
-
The movement of the terminus of a glacier in the same direction as ice flow, so that more land is progressively covered by ice; Typically occurs when accumulation exceeds ablation.
- Aerosol
-
Small particles or droplets suspended in the atmosphere.
- aggregate
-
Material composed of numerous rock fragments, as used by humans in construction
- Albedo
-
The proportion of light that is reflected from the surface of a substance
- Alga (plural: algae)
-
Alga (plural: algae). A photosynthetic eukaryote (plant) with simple unicellular or multicellular body structure, lacking leaves and vascular (water-carrying) tissues found in land plants.
- Alkali metal
-
A metal in group 1 of the periodic table, having one electron it its outer electron shell
- Alkali, alkaline
-
A substance that absorbs positive hydrogen ions and/or contributes negative hydroxyl ions when dissolved in water, leading to a high pH.
- Allotropes
-
Different minerals consisting of the same native element. (Synonymous with "polymorphs," but
used only for minerals that are native elements.)
- Alluvial fan
-
A seimi-circular or triangular body of coarse sediment formed at a break in slope in a river system
- Altocumulus
-
A broad, short clumped cloud typically formed at moderately high altitudes.
- Altostratus
-
A thin, laterally continous transparent cloud similar to stratus but formed at moderately high altitudes. Altostratus clouds typically allow sunlight to penetrate through.
- Ammonite
-
A group of cephalopod molluscs with chambered shells, similar to modern nautiloids
- Ammonium ions NH₄⁺
-
A form of reduced nitrogen consisting of positively charged ions with one nitrogen atom bonded to four hydrogen atoms NH4+
- Amplitude
-
The difference between the maximum and minimum value of a wave-like phenomenon. May
also refer to the difference between the maximum and the mean value.
- Amygdule
-
A vesicles in an igneous rock such as pumice that has been infilled with minerals
- analysis
-
Breaking down something into its component parts
- Andean orogen
-
Mountain belt that formed due to the subduction of oceanic underneath continental lithosphere.
Named after the Andes mountain range; also called a cordilleran orogen.
- Andes
-
An active mountain range (orogen) in western South America
- Anion
-
A negatively charged ion, that has gained one or more electrons relative to its constituent atom(s)
- Antarctic
-
Referring to the South Pole and the surrounding region
- Antarctic Circle
-
The southernmost area of the Earth that experiences constant darkness at the Summer solstice, and constant daylight at the Winter solstice
- Antarctic Circumpolar Current
-
An eastward current formed by the movement of oceanic gyres north of Antarctica.
- Antarctica
-
The southernmost continent on Earth
- Anthropogenic
-
Generated by humans
- Anthroposphere
-
The system comprising the human species and the parts of the Earth that humans have modified
- Anticyclone
-
A region of high pressure with diverging air circulation at low altitude, clockwise in the northern hemisphere, counterclockwise in the southern hemisphere
- Aphelion
-
The point in the Earth's elliptical orbit that is closest Sun
- aphotic
-
Describes the zone in the ocean where no light penetrates
- Apparent polar wander path
-
The path of one of the Earth’s magnetic poles over geologic time, as it appears relative to a
given continent
- Aquiclude
-
Impermeable unit within the Earth's crust that slows or stops the flow of groundwater
- Aquifer
-
Unit within the Earth's crust that is a reservoir of groundwater usable by humans
- Aquifers
-
Units in the outer part of the Geosphere that can supply water at a rate useful to humans
- Aragonite
-
A form of calcium carbonate CaCO3; that is produced by many organisms but is less stable than the more common polymorph calcite.
- Archaea
-
A group of Prokaryotic single-celled organisms that diverged from Bacteria early in Earth history
- Archean Eon
-
An eon early in Earth history prior to the Proterozoic from ~4 Ga to 2.5 Ga
- Archimedes' principle
-
When a body is partially or completely immersed in a fluid, it experiences an upthrust equal to the weight of fluid displaced.
- Arctic
-
Referring to the North Pole and the surrounding region
- Arctic amplification
-
A positive feedback phenomenon whereby more of the effect of climate change is felt in Arctic or Antarctic latitudes than is felt at the equator.
- Arctic Circle
-
The northernmost area of the Earth which experiences constant daylight at the summer solstice, and constant darkness at the winter solstice
- Arête
-
A jagged ridge between two glacial valleys
- Argon
-
An inert gas, element 18
- Arthropod
-
A member of the largest phylum of invertebrates, the Arthropoda, characterised by their jointed legs and chitinous exoskeletons. Arthropods include insects, spiders, crustaceans. and several other groups
- Artificial levees
-
Structures build by humans along the banks of rivers, with the purpose of preventing or reducing flooding.
- Artificial selection
-
The selective breeding of organisms with traits desired by humans in order to produce offspring more suitable for human purposes. Examples include varieties of dogs and crops.
- Ash fall
-
Near vertical descent of ash from the atmosphere to the surface of the Earth.
- Asteroid
-
A small object which orbits the Sun in the Solar System, ranging in size from 1 m to 850 km
- Asteroid Belt
-
A belt of small objects (asteroids) whose orbit lies between those of Mars and Jupiter
- Asthenosphere
-
The layer of the mantle lying beneath the lithosphere and capable of plastic flow
- Astronomical unit
-
The average distance between the Earth and Sun; 1.5 x 109 metres
- Atmosphere
-
The envelope of gas surrounding a planet
- Atmospheric Science
-
The study of the atmosphere of a planet (usually Earth).
- Atoll
-
A ring-shaped reef
- Atomic mass number
-
The total number of particles (neutrons plus protons) in the nucleus of an atom
- Atomic nucleus
-
The heavy, positively-charged central body in an atom of an atom.
- Atomic number
-
The number of protons in the nucleus of an atom of an element, equal to the number of electrons if the atom is not ionized
- Atomic weight
-
Atomic weight (relative atomic mass): The mass of an atom expressed on relative a scale in which the most common isotope of Carbon is given a value 12.
- Aureole
-
A halo of metamorphic rock developed around an igneous intrusion, resulting from contact
metamorphism.
- Aurora australis
-
Visible light produced in the southern hemisphere by solar wind’s interaction with particles in Earth’s thermosphere; southern lights
- Aurora borealis
-
Visible light produced in the northern hemisphere by solar wind’s interaction with particles in Earth’s thermosphere; northern lights
- autotroph
-
An organism that captures its own energy, usually by photosynthesis
- Avogadro’s number
-
The number of atoms or molecules in a mole of a substance.6.022 x 1023
- Bacteria
-
Prokaryotic single-celled organisms; distinguished from Archaea by the chemistry of their cell membranes and ribosomes.
- Banded iron formation
-
Layers of iron-rich minerals and chert that were particularly common in the Proterozoic Eon
- Bar
-
A depositional landform, typically of sand or gravel, in a river
- Barrier beach
-
A beach that is partly or completely separated from the land by a lagoon or inlet
- Barrier reef
-
A reef that is separated from the land by a shallow lagoon or shelf
- Barycentre
-
The centre of gravity of a system; the pivot point about which a system rotates when freely spinning.
- Basalt
-
The extrusive product of mafic magma. Basalt has a fine grain-size and a dark colour.
- Base flow
-
Water transported into a channel through groundwater flow into the base of the stream
- Base level
-
The elevation at which a river enters the sea or a lake
- Basic
-
Describes a substance that is able to accept hydrogen ions or generate hydroxyl ions. Alkaline.
- Batholith
-
Pluton larger than 40 km2 in area.
- Bathymetric
-
Describes maps of the ocean based on seafloor depth.
- Bathymetry
-
Measurement of the depth of the sea floor.
- Bed
-
A layer of sedimentary rock more than 1 cm thick
- Bed load
-
Sediment carried along the water-bottom (usually of a river) through rolling, sliding, and saltation
- Bedding
-
The presence of layers at centimetre or larger scale, having distinct composition an/or texture, typical of sedimentary rocks
- Benthic
-
Referring to the ocean’s bed, and the fauna that live there.
- Bergeron process
-
A typical process for the formation of snow. Vapour condenses first as supercooled water droplets. As the temperature falls the droplets release vapour which condenses as ice.
- Beta particles
-
High-speed electrons released during the conversion of a neutron to a proton in an unstable
isotope
- Bicarbonate
-
A negatively charged ion with the formula HCO3-, or a compound containing such ions
- Bimodal
-
Describes a statistical distribution that has two peaks or modes
- Biogeochemical cycle
-
The flow of an element through not only the Biosphere and and other spheres of the Earth
- Biogeography
-
The study of the spatial distribution of plants and animals
- biome
-
A collection of ecosystems having similar characteristics of climate, terrain, and energy flow
- Biosphere
-
The Earth system that comprises all living things and their non-living remains
- Biostratigraphic zone
-
A subdivision of strata recognized on the basis of characteristic fossil forms.
- Bird’s-foot delta
-
A delta with multiple distributaries separated by bays
- Birefringence
-
Double refraction; the splitting of light into two polarised beams refracted in slightly different directions, yielding a double image
- Blueschist
-
A metamorphic rock formed at high pressure and relatively low temperature; named for the presence of the blue sodium-bearing silicate mineral glaucophane.
- Blueschist facies
-
A metamorphic environment characterized by high pressure and relatively low temperature;
named for the presence of the blue sodium-bearing silicate mineral glaucophane.
- Body waves
-
Seismic waves that travel through the interior of the Geosphere
- Bold text
-
Text that is written with thicker lines than the rest of the text on a page
- Brackish
-
Having a salinity intermediate between that of freshwater and seawater.
- Braided
-
Braided streams have multiple branches that branch and rejoin
- Break in slope
-
A sudden change in slope from steep to gentle.
Brine
Water with a concentration of salt exceeding that of normal sea-water
- Breccia
-
Rock with gravel-sized angular grains
- Bridgmanite
-
A magnesium silicate mineral theoretically dominating the mineral content of the lower mantle;
(Mg,Fe)SiO3
- brine
-
Water having a salinity greater than normal sea water (35 parts per thousand)
- Brittle
-
Describes a material or process of deformation in which strength is suddenly lost across a fracture plane or planes
- Calcareous ooze
-
Deep-sea sediment comprising mainly the calcium-carbonate skeletons of foraminifera and coccolithophores
- Calcite
-
CaCO3; the most common mineral form of calcium carbonate
- Calcium carbonate
-
Compound with the formula CaCO3, the main component of limestone and the shells of marine
animals
- caldera
-
A broad crater with a rim that is low in relation to the crater diameter
- Caldera eruption
-
Highly explosive eruption that largely collapses a conical volcano leaving a broad circular crater
- Calving
-
The break-off of icebergs from glacier ice that is at sea level
- Cambrian Explosion
-
The adaptive radiation of animal forms in the marine environment of the early Paleozoic. Modern body plans rapidly appeared in the Cambrian, along with unique, extinct forms.
- Carbohydrate
-
Covalently-bonded compounds of carbon, hydrogen, and oxygen, in which hydrogen and oxygen are present in the same proportions as in water
- Carbon
-
Element 6, symbol C, contained in all living things. The most abundant isotope is carbon-12, containing 6 protons and 6 neutrons
- carbon cycle
-
A cycle describing the flow of the element Carbon through the Earth system.
- Carbon dioxide
-
A gas in which each molecule combines one atom of carbon with two of oxygen; formula: CO2
- Carbon-13
-
A stable isotope of carbon with seven neutrons that makes up a minority of natural carbon atoms.
- Carbon-14
-
An unstable isotope of carbon with eight neutrons. Carbon-14 is used for radiocarbon dating.
- Carbonaceous
-
A substance with a high content of reduced carbon
- Carbonate
-
Negatively charged ions with the formula CO₃ ²⁻; or, a substance containing such ions
- Carbonate ions
- Carbonate mud
-
Fine-grained sediment composed mainly of microscopic calcium carbonate grains
- Carbonate Platform
-
A flat continental shelf where the rate of carbonate sedimentation is able to keep up with
subsidence producing great thicknesses of shallow-marine carbonate rock
- Carbonate shelf
-
A continental shelf where most of the sediment is composed of carbonate mineral grains rather
than clastic, silicate grains
- Carbonate shoreline
-
A shoreline where carbonate minerals form most of the sediment
- Carbonate–silicate weathering cycle
-
A process whereby the chemical weathering of silicate minerals to form carbonate minerals controls the amount of silica, carbonate, and carbon dioxide in the Hydrosphere and Atmosphere.
- Carbonic acid
-
A weak acid formed in solution when carbon dioxide dissolves in water: formula H2CO3;.
- Cation
-
Positively charged ion
- Cell
-
The smallest unit of living things, including genetic material and cytoplasm surrounded by a cellular membrane.
- Cellulose
-
A polymeric carbohydrate found in plant del wals and bacterial biofilms; the most abundant organic substance in the biosphere
- Cement
-
Mineral matter deposited by groundwater in the pore space of a rock.
- Cenozoic Era
-
The current era in geologic time from ~65 Ma to the present day.
- Chalk
-
Soft limestone formed mainly from the calcite plates of unicellular planktonic plants called
coccolithophores.
- Changes that occur in living things over time
-
Changes that occur in living things over time as a result of natural selection
- chatter marks
-
Short notches, transverse to movement direction, found on glacially eroded or faulted surfaces
- Chemical weathering
-
Changes in the mineral composition of rocks as they are exposed to air and water at the Earth's surface, producing new minerals and dissolved material
- Chemosynthesis
-
A form of autotrophic metabolism where an organism obtains energy from chemical reactions without the assistance of sunlight
- Chert
-
A hard rock composed of very fine interlocking grains of silica SiO2.
- Chilled margin
-
The edge of an igneous intrusion where rapid cooling due to contact with cold host rock
produces finer-grained rock than is found in the interior of the intrusion.
- China Clay
-
Clay almost exclusively composed of the mineral kaolinite; used in the manufacture of porcelain
- Chinook
-
Warm orographic wind adjacent to the Rocky Mountains of Canada. Cooler air descends from high altitudes and is warmed by adiabatic compression.
- Chlorophyll
-
An organic compound responsible for the absorption of light during photosynthesis.
- Chloroplasts
-
Organelles within plant cells that contain chlorophyll, and are responsible for photosynthesis in plants and photosynthetic microbes; chloroplasts are descended from free-living cyanobacteria.
- Chondrite
-
A type of meteorite characterized by small, roughly spherical particles of glass or former glass, known as chondrules
- Chondrules
-
Small spheres interpreted as the remains of liquid droplets from the early Solar System.
- Chordate
-
Animal belonging to the phylum Chordata, characterized by a stiff dorsal rod or notochord accompanied by a hollow nerve cord; includes all vertebrates and a number of smaller, related groups.
- Chromite
-
Chromium oxide, a dark mineral often concentrated in the layers of layered igneous intrusions.
Formula Cr2O3
- Cinder Cone
-
A small, steep volcano composed of loose tephra fragments known as scoria
- Cirque
-
A bowl-shaped glacial valley that is approximately as short as it is wide (equant)
- Cirque Glacier
-
A small glacier in a cirque – a bowl-shaped depression on the side of a mountain formed by glacial erosion.
- Cirrocumulus
-
High-altitude clouds composed of ice particles, but having a clumped appearance similar to lower-altitude cumulus.
- Cirrostratus
-
A layer of ice cloud in the upper troposphere, typically above 6 km, that is thicker and more continuous than cirrus.
- Cirrus
-
Wispy, high altitude clouds that typically form above 6 km up to the tropopause. They are typically ice-particle clouds.
- Class
-
A category in taxonomy larger than an order but smaller than a phylum
- Clast
-
A solid fragment of sediment
- Clastic
-
Sediment formed from the solid products of weathering
- Clastic texture
-
The texture of clastic sedimentary rocks, where individual grains rest against each other without
interlocking
- Clay
- Clay (grain-size)
-
Clay (grain-size): Clastic sediment with a grain-size finer than 4 μm, deposited under very low-energy conditions.
- Clay (rock)
-
Clay (sediment or rock) A sediment or soft rock composed largely of clay minerals finer than 4 μm, used in the manufacture of pottery and porcelain.
- Clay mineral
-
Clay mineral: A fine-grained hydrous mineral; clay minerals are mainly sheet silicates, most characteristically
formed by chemical weathering
- Cleavage (mineral)
-
Cleavage (mineral): The behaviour of a mineral that splits along flat surfaces controlled by its crystalline structure
- Cleavage (rock)
-
Cleavage (rock):The behaviour of a fine-grained rock like slate that splits along flat surfaces because of the
preferred orientation of its mineral grains.
- Climate
-
Long-term trends in Earth’s atmosphere which may affect weather, but take effect for much longer. Climate is weather averaged over periods longer than a single year
- Climatologist
-
An atmospheric scientist who studies long-term changes in the Atmosphere
- Closed lake
-
A lakes that receives input, yet lacks an outflow other than evaporation.
- Closed system
-
A system that exchanges energy but not matter with its surroundings
- Cloud
-
A visible mass of aerosol water droplets suspended in the Atmosphere
- Coal
-
Carbon-rich sedimentary rock formed from solidified organic material that originated as peat
- Coal seam
-
A layer, or bed, of coal
- Coccolith
-
Small oval scale of calcium carbonate secreted by a coccolithophore
- Coccolithophore
-
Unicellular phytoplankton that secretes plates (coccoliths) of calcium carbonate to cover their bodies. Chalk is formed from these plates.
- Cold front
-
A boundary between cold and warm air where the cold air is advancing into the area previously occupied by warm air. The denser cold air pushes the warm air upwards, causing precipitation.
- Cold-based ice
-
Glacial ice that is below its freezing point at the base of a glacier
- Collisional orogen
-
A mountain chain formed where continental crust enters a subduction zone, coming into contact with another continent or an oceanic volcanic arc.
- Colour
-
A mineral property of limited usefulness in diagnosis. Minerals quartz may display a wide range
of colours.
- Columnar joints
-
Hexagonal structures formed due to cracks in thick lava flows that have shrunk during cooling.
- Comet
-
A small body in the Solar System with composition including large components of ices; comets develop a tail as they approach the Sun along eccentric elliptical orbits
- communities
-
Interacting populations of different species
- compaction
-
Reduction in volume of a sediment or soil due to the expulsion of air or water
- Composite volcano
-
A typically conical volcano consisting of layers of both tephra and lava; stratovolcano.
- Conchoidal
-
A curved or ribbed shape, seen in the fracture surfaces of many minerals and a few rocks such as chert and volcanic glass
- Concordant
-
Having a parallel orientiation to adjacent rock structures.
- Concrete
-
An anthropogenic mixture of cement and coarse sediment (sand or gravel), used in
construction.
- Condensation
-
The phase change of gas to liquid, or gas to solid, usually due to decreasing temperature.
- conduction
-
A process of movement of heat or electricity which does not involve the movement of the material through which it travels
- Conduction (electricity)
-
The transfer of electric energy from one part of an object to another due to a difference in electric potential between the two parts
- Conduction (heat)
-
The transfer of heat energy from one part of an object to another due to a difference in temperature between the two parts
- Cone of Depression
-
A lowering of the water table in an unconfined aquifer caused by the withdrawal of groundwater at one or more wells
- Confined aquifer
-
An aquifer where the upper boundary is defined by an aquiclude.
- Conglomerate
-
Coarse clastic sedimentary rock composed of gravel-size (>2 mm) grains.
- Conservation of momentum
-
A principal in mechanics in which the product of mass times velocity is conserved
- Contact metamorphism
-
Metamorphism spurred by physical contact with high-temperature magma. Grain size increases, while fabric may be eliminated. Thermal metamorphism.
- Continent-arc collision
-
A process of orogenesis that occurs where a plate carrying continental crust enters a subduction zone at an oceanic volcanic arc. Continental crust undergoes shortening and thickening, producing mountains.
- Continent-continent collision
-
A process of orogenesis that occurs where two converging plates both carry continental crust. Continental crust undergoes shortening and thickening, typically producing high mountains.
- Continental crust
-
Relatively low-density, thick crust that underlies the continents and the continental shelves.
- Continental drift
-
A theory that explains features of the Earth by slow movement of the continents over geologic time. The theory of continental drift has largely been incorporated into the later theory of plate tectonics, which also explains movements of the ocean floor.
- Continental margin
-
The fringe of a continent were it shares a boundary with oceanic crust.
- Continental rise
-
A gently-sloping zone of deposited sediment at the base of the continental slope, transitional the
deep-sea floor or abyssal plain.
- Continental shelf
-
An area of shallow sea (<200 m) at the edge of a continent, underlain by continental crust.
- Continental slope
-
Inclined sea-floor descending from the edge of the continental shelf down to the continental rise.
- Convection Currents
-
A cyclic motion of gas or liquid as it is heated. As the material is heated, it rises due to the lower density. Once it moves far enough from the heat source, it begins to cool, causing it to sink again, returning it to the heat source.
- Conventional hydrocarbon
-
Hydrocarbon deposits where a porous reservoir rock has enough permeability to yield oil or natural gas when penetrated by drilling.
- Convergent plate boundaries
-
The boundary between two plates moving towards one another. Convergent boundaries are the sites of subduction of one plate beneath the other.
- Coral
-
Sedentary suspension feeders, closely related to sea anemones and jellyfish, which may build exoskeletons of calcium carbonate. They are major reef-builders in Earth’s oceans.
- Cordillera
-
A mountain range at the western edge of North or South America, formed by plate convergence.
- Cordilleran Orogeny
-
Mountain-building episodes that occurred along the North or South American continental margin with the Pacific Ocean.
- Core
-
The central part of the Earth below about 2900 km from the surface, composed largely of metallic iron
- Core-mantle boundary
-
A major discontinuity and seismic reflector ~2900 km below the Earth's surface, separating the silicate mantle from the metallic core
- Cores
-
Cores (drilling): Narrow cylinders of sediment recovered, typically from lake beds or the sea floor during scientific investigation or during the search for mineral deposits
- Coriolis Effect
-
The apparent deflection of objects travelling over the surface of a rotating sphere, because of different rotation speeds at different latitudes
- Correlation
-
The match the sedimentary layers displayed by two or more different stratigraphic columns.
- covalent
-
Described bonding of atoms by the sharing of electrons
- Covalent bond
-
Atomic bonds wherein two atoms share electrons so as to acquire full outer electron shells.
- Craton
-
The core of a continent that has been stable since at least 500 Ma
- Creep
-
Slow, distributed movement of Earth material either down a slope (mass wasting), or within the Earth (as part of tectonic deformation)
- crevasse
-
A deep crack in the surface of glacier ice
- Crust
-
A thin, surface layer of the Earth that lies above the Moho; differentiated into thicker, lighter continental crust and thinner, denser oceanic crust
- Crustacea
-
Marine arthropods with chitinous shells augmented with calcium carbonate.
- crustaceans
-
A large group of Arthropoda with calcite-reinforced exoskeletons
- Crysophere
-
A system containing all Earth's ice
- Crystal lattice
-
The regularly repeating three-dimensional arrangement of atoms and/or ions in a crystalline solid material such as a mineral
- Crystal system
-
A category of crystal lattice distinguished by its symmetry
- Cumulate
-
Intrusive rock in which minerals that formed early have sunk and accumulated at the bottom of a magma chamber
- Cumulonimbus
-
Towering clumped rain-producing cloud, typically terminated at the top with an anvil-shaped ice-cloud. Typically produces lighning and thunder.
- Cumulus
-
Cloud with clumped domed tops and flat bases formed at low altitude where rising air reaches its dew point to form water droplets.
- Curie Point
-
The temperature at which a mineral acquires the ambient magnetic field orientation during its cooling; for the common magnetic mineral magnetite the Curie point is 570oC.
Daughter isotope
An isotope produced as a result of isotopic decay.
- Cyanobacteria
-
Single-celled prokaryotes capable of photosynthesis and the release of oxygen. Cyanobacteria were responsible for the original oxygenation of the Earth’s atmosphere.
- Cyclone
-
A region of low pressure with converging air circulation at low altitude, clockwise in the southern hemisphere, counterclockwise in the northern hemisphere
- Cytoplasm
-
Complex fluid mixture fills the cells of prokaryotes; in eukaryotes it surrounds the organelles, nucleus, and ribosomes.
- darcy
-
A unit of permeability. A permeability of one darcy allows one cubic centimetre per second of fluid having a viscosity of one centipoise through a sample with a cross-section of one square centimetre under a pressure gradient of one atmosphere per centimetre. The SI equivalent of one darcy would be 9.87 x 10⁻¹² m².
- Daughter isotope
-
An isotope that is a product of a nuclear decay reaction
- Debris flow
-
Mass transport in which large fragments are supported by the strength of a wet mud matrix that flows
.
- Decay
-
The breakdown of an atomic nucleus of an unstable isotope.
- Decay constant
-
A constant that relates the number of atoms that undergo radioactive decay per unit time to the
total number of remaining atoms; typically represented by Greek lambda (λ)
- Declination
-
The direction relative to the north of Earth’s magnetic field.
- Deep time
-
An expression for geologic time that emphasizes the challenge of imagining enormous lengths of time involved
- Deep-ocean trench
-
A deep, linear feature of the ocean floor that marks a convergent plate boundary
- Deep-sea clay
-
The finest-grained clastic sediment on the deep-sea floor.
- Deformation
-
Change in the shape, size, orientation, or position of materials over time in the Geosphere
- Deleterious
-
A characterization of a mutation that harms an organism’s ability to survive or reproduce
- Delta
-
A sediment deposit formed from the flow of a channel into a standing water body.
- Dendrochronology
-
Dates obtained from the number of annual rings in tree wood, typically obtained from core samples.
- Denitrification
-
The production of atmospheric nitrogen from ammonium ions by aerobic bacteria.
- Density
-
Mass per unit of volume of a substance.
- Deposit(-ion)
-
The accumulation of sediment in an area distant from the site of erosion.
- Depositional landforms
-
Landscape features formed from deposited sediment.
- Deuterium
-
A hydrogen isotope with an atomic mass number of 2, in which each atom contains one proton and one neutron, represented 2H or D
- dew point
-
For an undersaturated body of air, the dew point is the temperature at which the air would become saturated. The dew point is always equal to or lower than the actual temperature of the air.
- Dextral
-
A fault where the side opposite to an observer appears to be moving to the observer's right.
- Diagenesis
-
A change in sediment after it is deposited
- Diagenetic
-
Referring to changes in a sediment after it is deposited
- Diamond
-
A crystalline mineral form of elemental carbon the hardest known mineral.
- Diatomaceous ooze
-
Sediment formed from the silica skeletons of unicellular plants called diatoms
- Diatoms
-
Photosynthetic, unicellular plankton that inhabit oceans and lakes. Diatoms are notable for their siliceous skeletons of opal.
- Differential stress
-
Stress that acts with different intensity in different directions
- Differentiation
-
A process that causes a body of magma or rock to change composition, most commonly by the settling of early-formed minerals during cooling
- digital elevation model
-
A data set of points that are equally spaced in two horizontal directions (usually E and N); each point is associated with an elevation.
- Dipole field
-
The magnetic field produced by a magnetized body with north and south poles on opposite sides
- Discharge
-
The total rate of flow passing through a point of a stream, calculated as a volume per second or alternatively the product of velocity and cross-sectional area
- Discordant
-
Geological features that are not parallel to one another
- Dissolved load
-
Material that travels in flowing water in solution, rather than as solid particles
- Dissolved organic carbon
-
Reduced arbon that is carried in water in solution, including carbohydrates and amino acids
- Distributary
-
Channels that branch from a main channel in the downstream direction, typical of alluvial fans and deltas
- Disulfide bonds
-
Links within proteins between sulfur atoms in amino acids, that are important in defining protein shape and structure
- Divergent
-
The movement of two objects (such as portions of the Earth’s lithosphere) away from one another.
- Divergent plate boundary
-
The boundary between two plates moving apart from one another; divergent boundaries are commonly the sites of rift valleys and ocean-floor spreading.
- DNA
-
Deoxyribonucleic acid: A double-stranded nucleic acid that preserves genetic information
- Dodecahedron
-
A solid shape with twelve faces
- Domain
-
The largest taxonomic category recognized; living things are commonly divided into three domains (Archaea, Bacteria and Eukarya) but in some classifications two domains (Prokarya and Eukarya) are recognized
- Downcutting
-
The erosion of the base of a steeply sloping stream, particularly near the headwaters of a river.
- Downwelling
-
A downward flow of water, typically due Ekman transport that forces water towards a coast
- Drag
-
The force that operates between a flowing liquid and an adjacent solid
- Drainage basin
-
The total area that delivers water into a single channel or waterbody.
- Drainage divide
-
A border between drainage basins.
- Dripstone
-
A deposit of calcium carbonate formed by evaporation of water in caves
- Dropstone
-
A clast of rock that has fallen from floating ice into sediment below
- Drowned forest
-
A former forest where relative rise in the level of the sea or a lake has led to the death of trees; often a result of eustatic sea level rise during glacial melt.
- Drumlin
-
A tear-drop-shaped hill, a subglacial landform formed by ice sheets moulding subglacial sediment
- Dull
-
The lustre of a mineral whose surfaces reflect light poorly. Similar to earthy
- Dust storm
-
A suspension of mud-sized particles in the troposphere by powerful winds.
- Dwarf planet
-
A body in the Solar System with diameter larger than 850 km yet smaller than the planet Mercury
- Dyke
-
Dyke (USA — dike): A sheet-like igneous intrusion that is not concordant with any layering in its host rock
- Dynamic metamorphism
-
Metamorphism caused mainly by the extreme physical deformation of a rock; high strain produces small grain sizes and strong fabrics.
- Earth
-
The third planet from the Sun in the Solar System, and the principal object of study for geoscientists; the only planet known to possess life.
- Earth flow
-
A debris flow on the land surface
- Earth systems science
-
The study of the Earth as a set of interlinked systems, integrating subjects such as atmospheric science, oceanography, geology etc.
- Earthquake
-
An event in which stored elastic energy is rapidly released by sudden movement on a fault
surface
- Earthquake risk
-
The chance that an earthquake of a given magnitude will occur in a given area during a given time interval.
- Earthy
-
The lustre of a granular mineral whose surfaces reflect light poorly. Similar to dull
- Eccentricity
-
The length of the long axis in relation to the length of the short axis of an ellipse; a measure of the difference between the ellipse and a perfect circle.
- Echinoderm
-
A marine invertebrate in the phylum Echinodermata characterized by a skeleton of calcite crystal plates and a water vascular system; includes starfish and sea urchins.
- Ecliptic
-
The plane of Earth’s orbit around the Sun.
- Eclogite
-
A metamorphic rock formed at high pressure and moderate to high temperature; components of feldspar become dissolved in red garnet and green pyroxene
- ecological niche
-
The position of a species in an ecosystem, including its physical environment, predators, and energy sources
- ecology
-
The study of relationships between groups of organisms interacting with their physical environment
- ecosystem
-
A community plus its associated non-living systems (soil, air, water etc.)
- Ediacaran fauna
-
A diverse group of late Proterozoic extinct organisms of uncertain relation to modern animals
- Ekman spiral
-
The helical path of a downward water stream due to the Coriolis effect
- Ekman Transport
-
The net transport of water at 90 degrees an the original wind direction as a result of the Coriolis effect.
- El Niño
-
Warming of the central and east Pacific Ocean surface resulting in the supression of normal December upwelling off the coast of South America
- Elastic
-
Deformation where strain and stress are proportional. Energy is then stored in elastically deformed rocks and released when the stress is reduced.
- Electromagnetic radiation
-
A common type of energy movement characterized by oscillating electric and magnetic fields, including radio, infra-red, visible, and ultraviolet light, x-rays and gamma rays
- ellipsoid
-
A three-dimensional shape with only elliptical cross-sections
- Empirical
-
A scientific description or hypothesis drawn directly from observation or experiment
- End moraine
-
A moraine formed at the terminus of a glacier.
- Energy cycle
-
The transfer of energy through the various spheres and systems of the Earth
- ENSO
-
El Niño southern oscillation (ENSO) is an oscillating behaviour of the atmosphere–ocean system defined by changes in the temperature of east-Pacific surface waters over periods of several years
- Entropy
-
The amount of energy in a system that is not available to do physical work; also a measure of the degree of disorder in a system.
- Eon
-
The largest subdivision of geologic time
- epicentre
-
A point on the Earth's surface located vertically above the focus, or hypocentre, of an earthquake
- Equant
-
Having approximately equal length and width
- Equatorial counter current
-
A west-to-east (in mariner's terms, westerly) current that flows along the equator, opposite to the north and south equatorial Currents.
- Equatorial Currents
-
Westward currents (easterly in mariner's terms) formed by the movement of gyres north and south of the Equator.
- Equilibrium
-
For a chemical or physical reaction, a state in which the reaction occurs in both directions at the same rate; the amounts or concentrations of the reacting materials do not change over time.
- Equinox
-
A time in an Earth year when which the tilt of the Earth's axis is perpendicular to the line between the Earth and the Sun, resulting in equal lengths of daylight and darkness
- Erosion
-
The removal of material from a site of weathering on the Earth's surface.
- Erratic
-
A block of rock that has been moved by a glacier so that it appears foreign to the bedrock that it rests on
- Eruption column
-
Vertical eruptions of tephra from a volcanic vent, which may further expand in the atmosphere
- Esker
-
A ridge of well-sorted sand and gravel deposited by streams flowing beneath ice
- Estuary
-
A partially enclosed bay or river mouth in which freshwater and seawater mix
- Eukaryote
-
A unicellular or multicellular organism with cells that contain a distinct nucleus surrounded by cytoplasm with organelles
- Eukaryotic
-
Having cells that contain a distinct nucleus surrounded by cytoplasm with organelles
- Eustatic
-
Relating to global sea level, and its rise and fall through time
- Evapo-transpiration
-
The combination of evaporation and transpiration that transfers water vapour into the Atmosphere from the land surfaces
- Evaporation
-
The conversion of a substance from a liquid state to a gas
- Evaporite
-
Minerals or rocks produced by
precipitation of minerals from high-salinity water (such as seawater) during evaporation
- Evapotranspiration
-
The combined processes by which water is transferred from liquid at Earth’s surface to vapour in the atmosphere, comprising both physical evaporation and transpiration by plants
- Evolution
-
Changes in the characteristics of organisms, and the Biosphere as a whole, over periods of many generations.
- Evolved
-
Having undergone evolution
- Exfoliation
-
The splitting of solid rocks into sheets roughly parallel to the surface, due to volume changes and stresses during uplift, weathering and erosion
- Exponential decay
-
A reduction in the amount of material at a rate proportional to the amount of remaining material.
- Exponential format
-
A way of representing large or small numbers using a coefficient or mantissa (typically a number with one digit to the left of the decimal point) multiplied by an exponent (a power of 10)
- Extensional
-
Describes deformation, particularly at plate boundaries, in which rocks are stretched horizontally; divergent.
- Extensive
-
A quantity, such as heat energy or mass, which varies in proportion to the amount of material considered
- External forcings
-
Forcings that originate outside the system under consideration
- Extrusive
-
Describes igneous rock formed from magma that cooled at the Earth’s surface; volcanic.
- Eye
-
The cloud-free centre of a tropical cyclone where winds are at their calmest.
- Eyewall
-
The wall of cloud surrounding the eye of a tropical cyclone where winds are particularly fast
- Fabric
-
The structure of a rock defined by the preferred orientation of mineral grains or other components parallel to a line or plane, or both
- Family
-
A taxonomic category larger than a genus but smaller than an order.
- Fan delta
-
A body of sediment formed at a break in slope on the edge of a water body, combining characteristics of a delta and an alluvial fan
- Fault
-
A fracture in Earth’s crust where bodies of rock may slide past each other.
- Feedback
-
The process whereby a change in one part of a cycle causes changes throughout the cycle, which then affect the part originally changed
- feedbacks
- Feldspar
-
An abundant group of framework silicates containing aluminum together with some combination of
potassium, sodium and calcium
- Felsic
-
Igneous rock or magma with more than about 65% silica. Felsic rocks typically contain quartz
with potassium and/or sodium feldspar.
- Ferromagnesian minerals
-
Silicate minerals that contain large amounts of magnesium and/or iron, typically in solid solution, and a relatively low amount of silica.
- Fertilisation
-
A stage in sexual reproduction of metazoa at which gametes fuse to form a cell with double the number of chromosomes.
- Fetch
-
The distance over which wind can blow across the surface of a body of water to develop waves.
- Fieldwork
-
The gathering of samples and information by investigators working outdoors
- Firn
-
Ice particles formed by the loss of air in snow that has been resting on the surface of the Earth for more than a year
- Fissility
-
The ability of a rock to split into thin flakes or sheets parallel to sedimentary layers.
- Fissure Eruptions
-
The eruption of magma as lava through cracks in the crust.
- Fixation
-
The transformation of atmospheric nitrogen into a form more usable by organisms.
- Fixed
-
Nitrogen is described as fixed when it has been converted from its atmospheric form into a form more usable by organisms
- Fjord or Tidewater Glacier
-
A valley glacier that flows into a submerged valleys and terminates in the sea.
- Floodplain
-
The land surrounding a river channel which becomes submerged during high-discharge events (floods).
- Flow
-
Any movement of material down a slope in which the material behaves as a fluid, deforming continuously as it moves.
- Flowering Plants
-
Angiosperms; plants that reproduce via flowers as reproductive organs and fruits as dispersal units.
- Flows
-
Movement of fluid material along the surface of the Earth.
- Fluvial
-
Pertaining to rivers.
- Flux
-
The rate of flow into or out of a reservoir in a cycle
- Focus (earthquake)
-
The point within the Earth where an earthquake begins, and from which seismic waves radiate
- Focus (ellipse); plural foci
-
The focus points of an ellipse are two special points that lie on the long axis of the ellipse, symmetrically on either side of the centre at a distance apart f = √(p2-q2) where p and q are the major and minor diameters of the ellipse. The more eccentric the ellipse, the farther apart are the two foci.
- Foliation
-
A fabric seen in metamorphic rocks where grains or components are aligned parallel to a particular plane.
- Food Chain
-
A simplified diagram of consumers in a community, showing the transfer of energy through trophic levels.
- Food Web
-
A diagram showing all the producer–consumer predatory relationships between organisms in a community.
- Fool’s gold
-
A colloquial name for pyrite, due to its resemblance to gold.
- Footwall
-
The block of rock that lies below a sloping fault surface.
- Foraminifera
-
A diverse group of marine single-celled organisms whose preserved exoskeletons (or tests) may be preserved as fossils in marine sediments.
- Forcing
-
An effect that changes the balance of fluxes in a system and therefore cause the system to depart from a steady state
- Foreland Basins
-
A depression in the lithosphere created by the isostatic effect of an adjacent mountain belt.
- Formation
-
A layer of rock that appears on a geologic map
- Fossil
-
Remains of ancient organisms, buried in rocks
- Fossil Fuels
-
Carbon-rich substances found in the geosphere and formed from the remains of past-living organisms. Fossil fuels contain sufficient concentration of reduced carbon to produce usable heat when burnt in air.
- Fractionated
-
Having a disproportionate concentration of an isotope due to that isotope's heavier or lighter weight
- Fracture
-
Any surface across which a rock or mineral loses its strength, that is not controlled by the mineral structure
- Frazil
-
A form of sea ice consisting of separate needles, typically 3–4 mm long, floating in water
- Freeze
-
A phase change from liquid to solid, due to decreasing temperature.
- Frequency
-
For a wave-like phenomenon, the number of waves that pass a point in one second; measured in hertz (Hz).
- Friction
-
The resistance between two solids moving against one another
- Fringing Reefs
-
Elongated reefs that form adjacent to and parallel to a shoreline, without wide lagoon to separate the reef from land.
- Fronts
-
A border between air masses of different temperatures; usually associated with precipitatoin and changes in wind direction.
- Frost Action
-
The mechanical weathering effect of water as it freezes to form ice, due to expansion.
- Frost Heaving
-
The mechanical weathering effect of water trapped in spaces just below the surface of the Geosphere, raising rock or soil as it freezes to form ice.
- Frost Wedging
-
The mechanical weathering effect of water in thin cracks as it freezes to form ice, splitting rocks apart as a result of expansion.
- Frozen ground
-
Solid Earth material with pore spaces filled by ice
- Ga
-
Billion years before the present.
- Gabbro
-
Intrusive mafic igneous rock.
- Gaining Stream
-
Streams that increase their discharge in a downstream direction as a result of base flow from groundwater.
- Galena
-
Lead sulphide (PbS), a mineral displaying a cubic habit and metallic lustre.
- Garnet
-
A group of hard silicate minerals with isolated silicate tetrahedra containing combinations of aluminum, iron, magnesium, calcium and other elements. Garnets are most common in metamorphic rocks
- General Circulation Model (GCM)
-
Computer models for the atmosphere which which work as hypotheses for predictions about future weather and climate.
- Genes
-
Units of DNA in an organism which code for particular proteins, and, therefore, particular characteristics.
- Genetic Drift
-
Evolution that does not arise from selection pressure, but rather from chance.
- Genus
-
The taxonomic group above species and below family.
- Geode
-
A pore space partially filled by minerals.
- Geoid
-
A equipotential surface that approximates the Earth's surface. Gravity pulls at 90 degrees to the geoid surface everywhere.
- Geologist
-
A scientist who studies the Geosphere using on observations of Earth materials
- Geology
-
The study of the Geosphere, particularly the parts that can be studied by direct observation at the surface.
- Geomagnetic Poles
-
The north and south poles of Earth's magnetic field
- Geophysicist
-
A scientists who studies the interior of the Earth mainly through remote sensing methods using physical properties of the Earth.
- Geophysics
-
The study of the Earth using physical properties to probe parts that cannot be directly observed.
- Geoscientists
-
Geologists and geophysicists.
- Geosphere
-
The solid Earth
- Geostrophic Flow
-
Air that flows in a direction parallel to isobars, as a result of a balance between the pressure-gradient force and the Coriolis effect.
- Geothermal Energy
-
Energy originating from within the Earth, either from radioactive decay or from the orignal heat trapped at the planet's formation
- Geothermal Gradient
-
The rate of rise of temperature with pressure or with depth below the surface.
- Giga-annum
-
A billion years before present. Symbol: Ga
- Gigatonne
-
A billion tonnes, equivalent to 1012 kilograms; sometimes called a petagram.
- GIS
-
Geographic information systems
- Glacial
-
Pertaining to ice or glaciers. During cold episodes of Earth history, glacial periods are periods of more ice cover.
- Glacial/Interglacial Cycle
-
The oscillation of Earth’s climate between periods with more and less ice.
- Glacier
-
Masses of ice capable of slow movement over the land surface
- Glaciofluvial
-
Describes environments with rivers derived from melting of glacier ice
- glaciolacustrine
-
Describes lake environments associated with glaciers
- Glaciologist
-
A scientist who studies glaciers and ice in the Earth system
- Glaciomarine
-
Describes environments in the sea that are influcence by nearby glacier ice.
- Glaucophane
-
A blue chain-silicate mineral formed during the recrystallization of ferromagnesian minerals and feldspar under high-pressure conditions.
- global climate models
-
Computer-based models of how the atmosphere behaves. Although these models can be very complex, they represent simplified versions of the real atmosphere. Global climate models are typically types of general circulation model. The same abbreviation (GCM) applies to both.
- Global Positioning System
-
Global positioning system (GPS): A satellite-based navigation system that has additionally provided evidence of plate motion
- glossary
-
A list of terms that contains a definition or explanation of each
- Gneiss
-
High-grade coarse-grained metamorphic rock formed mainly of silicate minerals, typically displaying a strong banded fabric.
- Gold
-
A dense yellow metal element (Au), atomic number 79.
- Gondwana
-
A supercontinent assembled during the Proterozoic Eon, that was incorporated in the larger supercontinent Pangea during the Paleozoic Era. Parts of Gondwana form modern South America, Africa, Antarctica, Australia, and India.
- GPS
-
global positioning system
- Grade (metamorphic)
-
Metamorphic grade: The degree to which a rock has been metamorphosed, mainly as a consequence of temperature.
- Grade (Mineral deposits)
-
Grade (mineral deposits): The concentration of a desired element in rocks
- Graded Bed
-
A bed which has coarse sediment at the base but becomes progressively finer-grained towards to top..
- Grain-Size
-
The average diameter of a particle within a rock.
- Granite
-
Coarse-grained felsic igneous rock containing quartz and potassium feldspar.
- Granofels
-
Coarse-grained silicate metamorphic rock formed by thermal metamorphism.
- Graphite
-
A soft form of mineral carbon containing sheets of hexagonally linked carbon atoms weakly bound together
- Gravel
-
Sediment consisting of particles larger than 2 mm in diameter.
- Gravimeter
-
A device used to measure the slight variations in gravity seen at Earth’s surface due to differing rock density below.
- Gravity
-
A fundamental force between all masses in the universe
- Gravity Anomalies
-
Variations in the force of gravity due to differing rock densities below.
- Gravity Flow
-
The downward movement of a sediment-water mixture due to gravity. Debris flows and deep-sea turbidity currents are examples of gravity flows.
- Great Oxygenation Event
-
The mass emission of free molecular oxygen into the atmosphere by cyanobacteria at approximately 2.4–2.0 Ga.
- Greenhouse
-
A warm state of Earth’s climate, without continental ice sheets.
- Greenhouse Effect
-
The absorbtion of outgoing infra-red radiation by atmospheric gases, leading to heading of the Earth’s atmosphere.
- Greenhouse Gas
-
A compounds in the Earth’s atmosphere which absorbs infra-red radiation, preventing or delaying its escape into space.
- Greenstone
-
A dark green metamorphic formed through the metamorphism of a mafic igneous protolith, without strong fabric.
- gross primary production
-
The amount of inorganic carbon, or the amount of energy, captured by autotrophs in an ecosystem
- Grounding line
-
The line on the sea-floor between glacier ice that is floating and glacier ice that is resting on the bottom
- Groundwater
-
Water that occupies spaces within the Geosphere
- group
-
In geologic mapping, several formations that occur together
- Growth
-
Increase in size of a living organism, or part of a living organism
- Gulf Stream
-
A combination of thermohaline and surface currents in the North Atlantic that transports warm water from SW to NE, warming Europe.
- Gypsum
-
A mineral form of hydrated calcium sulphate (CaSO₄·2H₂O)
- Gyres
-
Circular movements of a fluid; typically applied to Coriolis-driven movements in the Atmosphere and oceans.
- Hadley Cell
-
A circulation of air that first rises near the equator before cooling and descending at the "horse latitudes"
- Half-Life
-
The amount of time required for a mass of a particular isotope to decay until only 50% of the parent isotope remains.
- Halite
-
The mineral form of table salt (NaCl)
- Halocline
-
The segment of the ocean’s depth where the most rapid increase in salinity with depth.
- Halogens
-
Group 17 of the periodic table. Elements with 7 electrons in their outer shell.
- Halokinesis
-
The flow of rock salt within the Geosphere.
- Hanging valley
-
A small glacial valley that enters a larger glacial valley high on the side of the larger valley
- Hanging Wall
-
The block of rock that lies above a dipping fault surface.
- Headward erosion
-
The extension of the head of a river valley in an upstream direction, resulting from downcutting, coupled with downslope movement of material.
- Headwaters
-
The upstream part of a river or stream, closer to the river source.
- Heat
-
The total thermal kinetic energy of all the molecules in a body or system
- Helium
-
Element 2, an inert gas
- Hematite
-
; A mineral form of oxidised iron (Fe₂O₃)
- Heterotrophs
-
Organisms which consume other organisms in order to release energy through respiration.
- Himalaya
-
The mountain range, or orogen, at the boundary between the Indian subcontinent and the rest of Asia; currently the highest mountain range in the world
- Hindcasting
-
The application of historical data to a climate model in order to test the predictive ability of the model against present observations
- Homo
-
The genus containing modern humans and our closest extinct relatives.
- Homo sapiens
-
The species containing modern humans
- Horn
-
A jagged peak formed in glaciated terrain where three or more arêtes meet
- Hornfels
-
A mostly fine-grained metamorphic rock without fabric formed through contact metamorphism.
- Host Rocks
-
The rock units into which magma intrudes.
- Hotspots
-
A localized region at the Earth's surface located above an unusually hot part of the mantle.
- Hurricane
-
A tropical cyclone a in the Atlantic and East Pacific
- Hurricane force
-
Wind speed >120 km/hr; the wind speed required for a tropical system to be considered a tropical cyclone.
- hydraulic fracturing
-
A process of pumping pressurized fluid into rock, causing fractures that increase permeability
- Hydraulic head
-
Tthe height of a water column that would produce the observed groundwater pressure difference between two locations. Groundwater flows from the location of high head to low head.
- Hydrocarbon
-
A compound constructed from carbon-carbon and carbon-hydrogen bonds.
- Hydrogen
-
Element 1, the most abundant element in the Universe and in the Sun
- Hydrogen bonds
-
Weak bonds between polar molecules, seen in water for instance, where the positive poles of one molecule are drawn to the negative poles of another.
- Hydrogen ion
-
A positively-charged hydrogen atom that has lost its only electron; responsible for the formation of hydronium ions H3O+ in water.
- Hydrogen sulfide (H2S)
-
A reduced form of sulfur that is emitted from hydrothermal vents where it provides a source of energy for chemosynthetic autotrophs in the absence of sunlight and oxygen.
- hydrogeologist
-
A scientist who studies groundwater
- hydrogeology
-
The study of water within the Geosphere
- Hydrographs
-
Graphs of river discharge over extended periods of time, indicating the rise and fall of total flow.
- Hydrologist
-
A scientist who studies the flow of water at the Earth's surface
- Hydrolysis
-
A reaction involving the breakdown of a mineral through the action of water which provides hydrogen and hydroxyl ions.
- Hydronium Ion
-
A positively charged ion H3O⁺ formed by the addition of a positive hydrogen ion to a molecule of water.
- Hydrosphere
-
All the free water on Earth, in the forms of water vapour, liquid water, and solid ice.
- Hydrostatic Stress
-
Pressure; stress that acts equally in all directions, particularly when applied by water.
- Hydrothermal
-
Hydrothermal describes groundwater that has been heated by geothermal energy
- Hydrothermal Mineral Deposits
-
Concentrations of minerals deposited by hot groundwater.
- Hydrothermal Vents
-
Openings, typically on the ocean floor, from which hot water or steam is able to escape.
- Hydroxyl Ion
-
A negatively charged ion OH⁻ formed when a water molecule loses a hydrogen ion.
- Hypocentre
-
The focus of an earthquake; the point within the Earth from which seismic waves begin to radiate.
- hypothesis
-
An statement that explains or predicts observations, and is therefore testable
- Hypsometric
-
A graph representation of the prevalence of different elevations across Earth’s surface.
- Ice
-
Water in its solid, crystalline form
- ice age
-
A period of Earth history during which large areas are covered by glaciers
- Ice cap
-
Small (<50,000 km²) areas of continental ice cover that are not confined by topograpy.
- Ice cores
-
Cylindrical samples of glaciers acquired by drilling.
- Ice field
-
An area of coalesced valley glaciers; similar to an ice cap, but constrained by topography and lacking a dome-like shape.
- Ice sheet
-
A large masses of glacial ice unconstrained by topography.
- ice shelf
-
A floating extension of a land-based glacier
- Ice Wedge
-
A V-shaped mass of ice formed by repeated shrinkage, cracking, infiltration of water, and freezing; found in periglacial areas.
- Ice-albedo feedback
-
A positive feedback wherein the melting of ice reduces the albedo of Earth’s surface, allowing further warming and additional ice melting.
- Icehouse
-
The Earth’s climatic state during times of cyclic expansion and retreat of ice sheets.
- Igneous
-
Relating to or formed from molten rock.
- Igneous Intrusions
-
Bodies of igneous rock formed when magma solidifies within the Geosphere.
- Igneous Rocks
-
Rocks formed from the cooling of molten material (magma).
- Incised
-
Describes a stream channel formed by downcutting of underlying rock, especially when it preserves shapes (eg meanders) formed before the downcutting episode.
- Inclination
-
The steepness of Earth’s magnetic field.
- Inertia
-
The resistance of an object to changes in movement, requiring that a force is necessary to change its velocity
- Infra-red Radiation
-
Heat energy in the form of electromagnetic waves with relatively wavelengths from ~1 mm to ~700 nm, the limit of visible light
- Inorganic
-
Describes carbon compounds that lack carbon–hydrogen bonds.
- Insolation
-
The amount of solar radiation received by a unit surface area in a given time period
- Intensity
-
Earthquake intensity measures the amount of ground shaking at a point. Intensity typically decreases away from the focus of the earthquake.
- Intensive variable
-
A value which is independent of the amount of material under consideration, such as temperature or chemical concentration.
- Interglacial
-
An interval during an ice age where warmer temperatures cause worldwide glacial retreat.
- Intermediate
-
An igneous rock or magma with between 52% and 65% silica
- Internal Forcings
-
Forcings that originate within the system under consideration.
- Intertropical Convergence Zone (ITCZ)
-
A low pressure band in the Earth’s atmosphere lying approximately along the equator
- Intrusion
-
A process whereby magma solidifies within the Geosphere.
- Intrusive Igneous Rocks
-
Igneous rock formed when magma solidifies within the Geosphere.
- Ion
-
An atom or group of atoms that has lost or gained one or more electrons, resulting in a net positive or negative electric charge
- Ionic bonds
-
Bonds between atoms formed by the transfer of electrons from one atom to another. The resulting negatively and positively charged ions are attracted together.
- Ionised
-
Of atoms or groups of atoms: Having lost or gained electrons producing a positive or negative charge.
- ionization
-
Addition or removal or of electrons to/from atoms or groups of atoms, forming ions
- Ionosphere
-
The layer of Earth’s atmosphere, including the mesosphere and thermosphere, where solar radiation may add or remove electrons from atoms, creating ions
- Iron II
-
Iron that has lost two electrons from each atom. Formerly known as ferrous iron
- Iron III
-
Iron that has lost or shared three electrons from each atom; oxidized iron. Formerly known as ferric iron.
- Iron Meteorites
-
A minority of meteorites, composed primarily of iron material probably derived from the cores of early proto-planetary bodies in the Solar System.
- Irradiance
-
The solar energy flux, typically measured as a rate of energy flow per square metre at the top of the Earth's atmosphere
- Island Arc
-
A chain of volcanic islands formed above a subduction zone.
- Isolated system
-
A system that exchanges neither matter nor energy with its surroundings
- Isostasy
-
The behaviour of upper layers of the Earth as if floating on the more deformable Asthenosphere below; lower density material corresponds to higher elevations.
- Isostatic Equilibrium
-
The behaviour of upper layers of the Earth as if floating on the more deformable Asthenosphere below; lower density material corresponds to higher elevations.
- Isostatic Rebound
-
The phenomenon in which the lithosphere rises when a surface load (such as an ice sheet) is removed.
- Isostatic Subsidence
-
The phenomenon in which the lithosphere falls when a surface load (such as an ice sheet) is added.
- isotopes
-
Isotopes of an element are atoms that have the same atomic number but different atomic mass, because of different numbers of neutrons in the nucleus
- Isotopic Dating
-
The use of unstable isotopes with known half-lives to calculate the approximate age of a sample.
- Jet stream
-
West-to-east winds moving at the top of the troposphere, following a pressure gradient. The jet stream typically meanders, and roughly follows to the polar front.
- Jovian
-
Relating to planet Jupiter and the other outer planets.
- Jovian or Outer Planets
-
The four outermost planets in the Solar System, having small rocky cores wrapped in thick atmospheres and a multitude of natural satellites.
- Jupiter
-
The fifth planet from to the Sun, and the largest
- ka
-
Kilo-annum; thousand years before present.
- Kame terrace
-
A glacial landform made of sand or gravel deposited by water flowing along the edge of a glacier
- Kaolinite
-
A clay mineral formed of hydrous aluminium silicate. AlSi₂O₅(OH)₄
- Katabatic wind
-
The descent of cold, dense air cooled by higher-altitude glaciers towards lower ground.
- Kenorland
-
An early supercontinent that may have formed around 2.7 Ga in the late Archean.
- Kepler
-
Johannes Kepler. A German natural philosopher who determined three laws of planetary motion, relating to each planet’s elliptical orbit about the Sun.
- Kerogen
-
Organic matter in sediment or sedimentary rock that is insoluble in organic solvents and that may form oil and gas if heated.
- Kettle
-
A lake or depression in a periglacial area, typically formed as a result of the melting of a stranded ice block during glacier retreat
- Kilo-annum
-
Thousands of years before present; ka.
- Kimberlite
-
Ultramafic tuff produced by explosive volcanic eruptions sourced from the mantle; the main source of diamonds.
- Kimberlite Pipes
-
Large cylindrical structures preserving ultramafic tephra sourced from the mantle; the main source of diamond.
- kinetic
-
Having to do with movement
- Kinetic energy
-
The energy possessed by a mass in motion.
- Kingdoms
-
A high taxonomic level in most classifications of organisms; kingdoms rank above phyla but below domains.
- Komatiite
-
Extrusive ultramafic volcanic rock.
- Kuiper Belt
-
A belt of mainly comets hypothesized to orbit around the Sun beyond the orbit of Neptune
- La Niña
-
A phase of El Niño southern oscillation (ENSO) in which west-Pacific rise of air is intensified and the equatorial east Pacific is unusually cold
- Lagoon
-
An area of shallow water protected from large waves by a barrier reef or atoll.
- Lahar
-
A debris flow generated by volcanic activity
- Lake
-
A body of surface water that is isolated from the world's oceans.
- lamina
-
Lamina (plural laminae): a thin layer (less than 1 cm thick)
- Laminar
-
Sheet-like; applied to flow of fluids, it describes flow along sub-parallel lines, lacking the gyres typical of turblence.
- Land breeze
-
Wind that flows from land to sea, typically caused as a high-pressure region forms on land as air cools rapidly at night
- Landforms
-
Distinctive landscape shapes characteristic of particular Earth-surface processes
- Lapilli
-
Large fragments of tephra 2 to 64 mm in diameter.
- Large Igneous Provinces
-
Regions of the Earth where large amounts of magma (usually mafic) have been generated in a geologically short time.
- Last glacial maximum
-
A time about 20 thousand years ago when glaciers reached a maximum extent.
- Latent energy (heat)
-
Energy released or absorbed in phase changes.
- Lateral Blast
-
Volcanic explosion that expels tephra in a near-horizontal direction.
- Lateral Erosion
-
The widening of a river valley by a low-gradient river. This process typically occurs when the bends of rivers reach the valley sides.
- Lateral moraine
-
An accumulation of till or rock fragments along the edge of an Alpine glacier
- Lava
-
Magma (molten rock) that has emerged onto the surface of the Earth.
- Lava Domes
-
Small, steep-sided volcanoes typically formed by felsic lava.
- Lava Lake
-
A body of liquid lava ponded in the crater or caldera of a volcano.
- Layered Igneous Intrusions
-
Bodies of mafic magma that cooled within the Geosphere, in which layers of different composition have formed.
- Left-lateral
-
Sinistral: fault motion such that the far wall of a fault appears displaced to the observer's left
- Legumes
-
A family of flowering plants (including peas and beans) capable of fixing nitrogen through symbiosis with nitrogen-fixing bacteria. Nodules within the legumes’ roots provide an anaerobic environment in which nitrogen fixation can occur.
- Lignin
-
An organic polymer found within the cells walls of plants, and especially in wood.
- Lime mud
-
Fine-grained calcium carbonate
- Limestone
-
Sedimentary rock composed mainly of calcium carbonate
- Limiting Nutrients
-
Nutrients which, when scarce, prevent cell division or growth from occurring, even in conditions where other nutrients are abundant of other nutrients.
- Lineation
-
The fabric seen in metamorphic rocks where grains or other components are oriented parallel to a line.
- Lipids
-
Organic, chain-like compounds, including oils, fats, and waxes, that are non-polar as whole, though they may have polar and nonpolar ends. As a result, lipids are not easily soluble in water, and are important for cells in forming cell membranes.
- Liquidus
-
A boundary on a phase diagram separating fully liquid material from material with some solid components, marking the completion of melting.
- Lithification
-
The solidification of sediment into solid sedimentary rock
- Lithified
-
Sedimentary material that has solidified into sedimentary rock
- Lithium
-
Element 3, the lightest metallic element
- Lithosphere
-
The rigid outer part of the Geosphere that is divided into plates, consisting of the crust and outer layer of the mantle
- Lithosphere–asthenosphere boundary
-
A boundary typically between 50 and 250 km deep within the Mantle, separating rigid plates above from slowly deforming material below
- Lithospheric Upper Mantle
-
The portion of the Lithosphere below the Moho and above the Lithosphere-Asthenosphere boundary
- Little Ice Age
-
A short period of cooling from 1400 to 1850 CE. The little ice age was not a true glacial interval, but rather a temporary decline in temperatures across the world.
- Littoral Zone
-
The zone of the shore that is exposed to air dry during low tide, but submerged during high tide.
- Lobe
-
A rounded part of a delta’s depositional structure.
- Local base level
-
The elevation of a river at a point where the speed of flow is near zero, typically at a lake.
- Longitudinal Profile
-
A plot of elevation versus downstream distance in a river.
- Longshore current
-
the gradual movement of water parallel to the shore resulting from obliquely impinging waves.
- Longshore drift
-
The transportation of sediment by longshore currents.
- Losing stream
-
Streams that lose discharge downstream by recharging groundwater.
- Love Waves
-
Seismic surface waves in which motion is horizontal and perpendicular to the wave propagation direction
- Low-Velocity Zone
-
A zone in the upper mantle where both P- and S-waves slow down, corresponding approximately to the Asthenosphere
- Lower Mantle
-
The portion of the mantle below ~650 km, below the transition zone.
- Lustre
-
Lustre (USA: luster): The quality of light reflected from a mineral’s surface.
- Ma
-
Mega-annum; Million years before the present.
- Macrofossils
-
Fossils large enough to be viewed by the unaided eye.
- Mafic
-
Of silicate minerals and rocks, having large amounts of magnesium and iron; mafic rocks have silica contents of 45–50%.
- Mafic Igneous Rock
-
Igneous rocks with low amounts of silicates, of only 45-50%, in their original magma.
- Magma
-
Molten rock
- Magma Differentiation
-
Changes in the composition of magma due to the removal of certain chemical components, often as a result of mineral settling.
- Magnetic Anomalies
-
Regions where Earth’s magnetic field is stronger or weaker than predicted by a simple dipole model of the magnetic field.
- Magnetic Field
-
A region within which the direction of magnetic force can be determined
- Magnetic Reversals
-
Geologically rapid exchange of the polarity of Earth’s magnetic north and south poles.
- Magnetite
-
An iron oxide mineral with the formula Fe₃O₄
- Magnitude
-
A measure of the energy release from an earthquake, scaled to the logarithm of displacement at a standardized distance.
- Mammals
-
A class of vertebrates characterized by lactation, three middle ear bones, and hair. Mammals make up the majority of megafauna in the Cenozoic Era.
- Mantle
-
The layer within the Earth or other inner planet that overlies the core and makes up the majority of the planet, composed chiefly of magnesium- and iron-rich silicates
- Mantle Plume
-
An uprise of mantle material that cause a hotspot in the Earth’s lithosphere.
- Mantle Wedge
-
The mantle that in a subduction zone rests above the subducted lithosphere, and is overlain by a volcanic arc.
- Marble
-
The metamorphosed product of limestone. Marble contains coarse, interlocking calcite grains, sometimes together with other minerals.
- Mars
-
The fourth planet from the the Sun
- Mass balance
-
The difference between the amount of ice that a glacier accumulates and the amount lost by ablation.
- Mass Spectrometer
-
A device used to measure and count atomic masses.
- Mass wasting
-
Processes that move dense solid material down slopes on the surface of the Geosphere due to the force of gravity.
- Maturation
-
The transformation over time of raw organic matter into fossil fuel.
- Maunder Minimum
-
An interval during the late 17th to early 18th century CE when sunspots were at a minimum
- Meandering
-
River behaviour characterized by large changes in channel direction (bends).
- mechanical
-
related to movement and forces
- Mechanical weathering
-
The physical breakdown of rock into smaller particles at the surface of the Geosphere.
- Medial moraine
-
A linear accumulation of till in the middle of an Alpine glaciar, formed by the merging of two lateral moraines
- Mega-annum
-
Million years before present; Ma.
- Meiosis
-
The two-stage process of cell division in sexual reproduction, whereby four daughter cells are created each with half of a full set of chromosomes.
- Melanic
-
Black coloration seen as a variation in moths.
- Membranes
-
Barriers composed of phospholipids that are barriers within and around cells.
- Mercury
-
The nearest planet to the Sun, and the smallest planet.
- Mesopause
-
The boundary separating the mesosphere and thermosphere, where the temperature of the atmosphere reaches its lowest point
- Mesosphere
-
The layer of Earth’s atmosphere directly above the stratosphere, divided from it by the stratopause. In the mesosphere, the temperature decreases with elevation.
- Mesozoic
-
An era in the Phanerozoic Eon of Earth history, from about 200 Ma to about 65 Ma
- Messenger RNA
-
A type of RNA responsible for the transfer of genetic information transcribed from DNA in the nucleus to ribosomes in the cytoplasm, where proteins are synthesised
- Metabasalt
-
Metamorphic rock derived from basalt.
- Metabolism
-
The capture, transfer, and use of energy by complex carbon-containing molecules in living things
- Metallic
-
Relating to the properties of metals, substances that tend to conduct electricity and to form bonds by losing electrons
- Metallic Bonding
-
The form of bonding in metals, whereby a cloud of free electrons is held by a lattice of metal ions.
- Metallic Lustre
-
High-quality reflection of light from the surfaces of a mineral.
- Metamorphic
-
Describes rock formed through transformation of older rock by heat and pressure, without melting
- Metamorphic Facies
-
Environments of formation metamorphic rock characterized by the stability ranges (in temperature and pressure) of particular mineral assemblages.
- Metamorphic rock
-
Rocks that have recrystallized while solid, as a result or heat, pressure, and/or deformation
- Metamorphism
-
The transformation of a rock in the solid state due to high temperature and/or pressure.
- Metasandstone
-
Metamorphic rock derived from sandstone.
- Metastable
-
A state wherein a system is not in equilibrium, but an input of energy would be required to move it to an equilibrium state.
- Metavolcanic Rock
-
Metamorphic rock derived from volcanic rock.
- Metazoa
-
Multicellular animals
- Meteorite
-
The extraterrestrial rock mass that has reached the Earth’s surface through impact.
- Meteoroids
-
Bodies in the Solar System smaller in size than asteroids, with diameters less than a metre.
- Meteorologists
-
Atmospheric scientists who study short term changes in the atmosphere known as weather.
- Meteors
-
Meteoroids as they enter Earth’s atmosphere. Friction with the atmosphere causes a glowing tail to form in the wake of the meteoroid.
- Methane
-
A gaseous compound of carbon and hydrogen CH4. Methane is the principal component of natural gas. In the Earth's atmosphere it acts as a greenhouse gas.
- Mica
-
A group of sheet-silicate minerals with a sheet-like habit and perfect cleavage.
- Microfossils
-
Fossils requiring magnification for study; fossils too small for the unaided eye to see features.
- Micronutrients
-
Elements or compounds that, while essential for life functions, are only required in small quantities.
- Mid-Ocean Ridges
-
Elevated regions on the ocean floor centred on divergent plate boundaries.
- Migmatites
-
Gneisses formed through partial melting, containing a mixture of igneous and metamorphic material.
- Milankovitch cycles
-
Repetitive variations in the Earth’s tilt, axis orientation and elliptical orbit shape, that cause climate forcing.
- millidarcy
-
A unit of permeability equal to one thousadth of a darcy
- Mineral
-
A naturally occurring crystalline solid with a fixed or limited range of compositions
- Mitochondria
-
Organelles within the cells of eukaryotes are the site of respiration within eukaryotic cells
- Mitosis
-
The most common process of cell division whereby both daughter cells acquire full copies of the parent cell’s genetic material
- model
-
A simplified or theoretical version of a complex natural system, either a physical model using analog materials, or a mathematical model run on a computer.
- Modified Mercalli Scale
-
A scale for measuring the intensity of an earthquake
- Moho
-
Mohorovičić Discontinuity: The boundary at the base of the Earth’s crust where seismic P-waves abruptly increase in velocity.
- Mohorovičić Discontinuity
-
Moho: The boundary at the base of the Earth’s crust where seismic P-waves abruptly increase in velocity..
- Moist Adiabatic Lapse Rate
-
The rate of cooling as mass of moist air rises without exchanging heat with its surroundings, while water vapour in the air condenses. The rate of adiabatic cooling is offset by the release of latent energy during condensation
- Mole
-
An amount of an element or compound such that the number of grams of the substance is equal to the atomic or molecular weight; one mole of any substance contains a number of atoms or molecules equal to Avogadro’s number.
- Molecular Phylogenetics
-
A method by which DNA from two or more organisms is compared to determine their relatedness
- Mollusca
-
A phylum of invertebrates which typically produce shells composed of calcium carbonate; Mollusca include snails, clams, and octopus (a group that has secondarily lost the shell)
- Moment Magnitude
-
A scale of earthquake size that depends on the amount of slip and the slipped area of the fault surface. The moment magnitude is commonly calibrated to the older Richter scale but gives a more precise measure of earthquake size.
- Monsoon
-
Climate characterised by oscillating dry and extremely wet seasons, caused by northward and southward movement of the intertropical convergence zone (ITCZ)
- Moon
-
Earth's only natural satellite; also (with lowercase m) any natural satellite of a planet
- Moons
-
Natural satellites of planets are sometimes known as moons.
- Moraine
-
An accumulation of glacial till
- Moraines
-
Accumulations of till associated with glaciers.
- Mountain Wind
-
The descent of cool, dense air from high ground into adjacent valleys
- Mud
-
Sediment composed of particles with a diameter less than 1/16 mm.
- Mudflow
-
A flow of fine-grained sediment mixed with water
- Mudstone
-
Clastic sedimentary rock with a grain-size below 1/16 mm
- Multi-year ice
-
Sea ice that has lasted more than one year
- multicellular
-
Having a body comprising numerous cells separated by membranes from one another
- Mutations
-
Changes in the genetic material carried by a cell or an organism caused by copying errors during cell division, by exposure to certain chemicals and types of radiation, or other essentially random processes
- Mylonite
-
A dynamic metamorphic rock formed through the extreme deformation that has reduced the size of its mineral grains
- Native Elements
-
Minerals or other substances composed wholly of a single element.
- Natural arch
-
A feature of cliffs that have been undercut as a result of weathering and erosion, producing a hole or window through solid rock.
- Natural Gas
-
Hydrocarbon-rich gas derived from sedimentary organic matter.
- Natural levee
-
A raised bank along the edge of a river channel due to deposition during flooding.
- Natural satellites
-
Objects in the solar system that orbit around a planet
- Natural Selection
-
The evolutionary process whereby the environment favours that survival of particular characteristcs in a population
- Neap tide
-
A tidal phenomenon caused by a 90 degree angle between the Sun and the Moon, resulting in reduced tidal range.
- Nebula; nebulae (plural)
-
Interstellar clouds of dust and gas
- Negative Feedback
-
A cycle in which the products of a process act as inputs inhibiting the same process, reducing the effects of the process.
- Negative Slope
-
A feature of a graph in which the value of the dependent variable decreases when the independent variable increases; in cartesian x-y coordinates, the graph slopes downward to the right.
- Neptune
-
The eighth planet from the Sun.
- Neritic Zone
-
The zone of the ocean that is covered by water at all tidal stages directly above the continental shelf, with a maximum depth of about 200 metres.
- Neutron
-
A neutrally-charged particle within an atom’s nucleus
- Névé
-
Partially compacted snow in its first year.
- Newton
-
Isaac Newton: an English natural philosopher who developed the laws of gravity and inertia
- Niche
-
An organism’s position in an ecosystem.
- Nimbostratus
-
Horizontal low-altitude cloud layers (stratus) that produce steady precipitation.
- Nitrate Ions
-
Negatively charged ions formed by the oxidation of nitrogen; NO³⁻.
- Nitrogen
-
Element 7. In the molecular form N2, the most abundant gas in Earth’s atmosphere.
- Nitrogen Cycle
-
The process by which nitrogen is exchanged between the Atmosphere, Hydrosphere, and the Biosphere, undergoing oxidation and reduction reactions in the process
- Nitrous oxide
-
A gas composed of nitrogen and oxygen, produced as part of the nitrogen cycle, which acts as a greenhouse gas in the atmosphere; N₂O
- Non-Renewable Resource
-
Materials such as fossil fuels and minerals which do not form at a rate fast enough to replace their consumption by humans.
- Nuclear fusion
-
A process in which the two light atomic nuclei join together to form a single more massive nucleus, releasing energy
- Nuclear Radiation
-
Particles or electromagnetic waves released by the decay of atomic nuclei in unstable isotopes.
- nucleation energy
-
Energy required to form the first stable particle or droplet of a substance (usually water or ice fomed during a condensation process)
- Nucleic Acids
-
Long, chain-like molecules (polymers) composed of linked units called nucleotides. Two major kinds of nucleic acids exist: DNA and RNA.
- Nucleus (biology)
-
An membrane-bounded body within eukaryotic cells that contains the genetic material in the form of DNA
- Nucleus (physics); nuclei (plural)
-
The central part of an atom, carrying positive charge and almost all of the atom's mass
- Nuna
-
A supercontinent which may have formed 1.8 billion years ago in the early Proterozoic Eon.
- Nunatak
-
An exposed rock mountain top projecting through an ice sheet or ice cap
- Nutrients
-
Elements or compounds essential for life processes.
- Oblate Spheroid
-
A ellipsoid with circular symmetry about an axis which is shorter than its other radii; a flattened sphere.
- Obliquely
-
Diagonal; at an angle that is not a multiple of 90°.
- Obliquity
-
The angle at which the Earth’s axis of rotation is tilted towards the ecliptic.
- Oceanic Crust
-
Thinner crust is composed mostly of mafic rock.
- Oceanic zone
-
The reagion beyond the continental shelf, where water depth is greater than 200 m.
- Oceanography
-
The study of Earth's seas and oceans
- Oil
-
Liquid Petroleum; organic matter that has undergone burial and subsequently been transformed into hydrocarbon-rich liquid.
- Oil Reservoir
-
A region within the Geosphere where liquid petroleum is present within porous, permeable rock.
- Oil Shale
-
Fine-grained sedimentary rock which holds a large proportion of hydrocarbons.
- Olivine
-
A silicate of iron and/or magnesium with separate silicate tetrahedra in its structure; (Mg,Fe)₂SiO₄.
- Oort Cloud
-
A spherical collection of comets outside the orbits of all other planets, at distances between 2,000 tand100,000 astronomical units from the Sun.
- Ooze
-
Fine-grained deep-sea sediment composed of the remains of the skeletons of plankton.
- Opal
-
Non crystalline silica, sometimes including a small proportion of water; SiO₂·nH₂O.
- Open lakes
-
Lakes with an outlet, such a stream, with discharge equal to that of the lake’s input; open lakes typically contain fresh water.
- Open system
-
A system that exchanges both matter and energy with its surroundings
- ophiolite
- Ophiolites
-
Sections of mafic or ultramafic rock from oceanic lithosphere that have been uplifted on land.
- Optical Mineralogy
-
The study of minerals under the microscope in order to identify them.
- Orbital Forcings
-
Changes in Earth’s obliquity, eccentricity, and the precession of equinoxes which affect the flow of energy through Earth systems
- Orders
-
A taxonomic group of organisms larger than a family but smaller than a class
- Organelles
-
Structures within cells that accomplish important functions, typically relating to respiration, production of organic compounds, or reproduction
- Organic
-
Any reduced carbon compound containing carbon–hydrogen bonds (or, rarely carbon–halogen bonds); elemental forms of carbon (with only carbon–carbon bonds) are regarded as inorganic.
- Organic Matter
-
Matter containing reduced carbon that originated in a living organism.
- Orogen
-
A mountain belt formed by shortening of the crust.
- Orogenesis
-
A mountain-building process that occurs as crust shortens during the convergence of the lithosphere.
- Orographic Lifting
-
The rise of air as wind blows over hills or mountains
- Orographic Winds
-
Wind patterns associated with mountains
- orthogonally
-
At right angles or 90°
- Outburst channel
-
A channel carved by a sudden release of glacial meltwater
- Outer Core
-
The layer of the core directly below the mantle, composed mainly of liquid iron.
- Outwash
-
Gravel and sand deposited by meltwater beyond the terminus of glaciers.
- Overland flow
-
Flow of water in a sheet over the land surface, without channel formation
- Oversaturated
-
Describes a situation where a substance (e.g. water vapour) is more concentrated in a mixture (e.g. air) than the amount that would be in equilibrium with a separate phase (e.g. liquid water or solid ice)
- Ox-bow Lake
-
A lake formed when a meander channel is abandoned during hte evolution of a river.
- Oxidation
-
The combination of an element with oxygen, or more generally, any chemical process resulting in electron loss
- Oxidation States
-
An element has different oxidation states when it can lose or share different numbers of electrons to form ions
- Oxidised
-
Oxidised or oxidized: The state of an atom that has lost one or more electrons during a chemical reaction; named because oxygen is the most common remover of electrons.
- Oxidised Carbon
-
Carbon which has lost or shared all four of its outer shell electrons with oxygen
- Oxygen
-
Element 8. In the molecular form O2, the second most abundant gas in Earth’s atmosphere.
- Ozone
-
A compound consisting of three oxygen atoms O3 which exists in small amounts in the atmosphere due to both natural and anthropogenic activity.
- P-waves
-
Seismic body waves in which the vibration direction is parallel to the propagation (travel) direction.
- pack ice
-
Sea ice that covers more than 70% of the sea surface with slabs metres to kilometres across
- Pahoehoe
-
A ropy lava surface formed when high-temperature flows of mafic lava cool.
- Paleobiologist
-
A scientist who studies the remains, lives, and evolution of ancient living things
- paleobotany
-
The study of fossil plants
- Paleomagnetism
-
The study of preserved magnetism in ancient rocks
- Paleontology; also palaeontology
-
The study of fossil animals; often used to describe the study of all fossils, including plants, where “paleobiology” would be more strictly correct.
- Paleozoic Era
-
The first era of the Phanerozoic Eon, in which multicellular organisms prominently radiated in the Cambrian Explosion, and multicellular life emerged onto land
- Pancake ice
-
A stage in the development of sea ice, characterized by roughly oval ice masses 30 cm – 3 m in diameter
- Pangea
-
Pangea (UK: Pangaea): A supercontinent formed during the late Paleozoic Era and dispersed during the Mesozoic and Cenozoic eras
- Panning
-
The practice of shaking sediment grains in water to separate gold and other other high-density minerals.
- Paradigm
-
A new collection of objectives, methods, and theories for a scientific discipline, developed during a scientific revolution
- Parent isotope
-
An unstable isotope which decays and yields a daughter isotope.
- Partial Melting
-
Melting of rock material to produce a mixture of solid and liquid.
- Partial Pressure
-
The pressure exerted by a single gas within a gas mixture; the partial pressure of each gas is proportional to its fraction of molecules in the mixture.
- Partially Molten
-
Rock material that is a mixture of solid and liquid
- Passive Continental Margins
-
A continental margin that does not coincide with a a plate boundary.
- Patterned Ground
-
Geometric patterns that form on surfaces experiencing intense freezing and thawing.
- Peat
-
Carbon-rich material formed from compressed plant remains; a first stage in coal formation.
- Pelagic
-
Describes the open water column of the ocean; the environment away from the seafloor in which planktonic and nektonic organisms live.
- Peptide Bonds
-
The carbon-nitrogen bonds between amino acids that build peptides and proteins.
- Peridot
-
Gem-quality olivine
- Peridotite
-
Utramafic rock composed mostly of pyroxene, usually together with olivine
- Periglacial
-
The landscape surrounding glaciers.
- Perihelion
-
The furthest from the Sun of the Earth in its elliptical orbit.
- Periodic Table
-
A visual representation of the known elements, by order of their atomic number. Columns represent elements having similar outer-shell electron configurations, and hence similar chemical properties
- Permafrost
-
Material near the Geosphere surface that remains frozen for two or more years.
- Permeability
-
The ability of a solid to and allow fluid to move through it.
- Petroleum
-
Naturally occurring liquid and gaseous hydrocarbons: Oil and natural gas.
- petroleum reservoir
-
A volume of porous rock within the Geosphere that contains oil or natural gas in sufficient quantity to be extracted
- pH
-
The standard scale of a substance’s acidity or alkalinity; minus the logarithmic concentration of hydrogen ions; acids have low pH; alkalis (bases) have high pH.
- Phanerozoic Eon
-
The current eon, following the Proterozoic, from about 539 Ma to the present day, characterized by abundant remains of muticellular organisms
- Phase
-
The part of a system that is separated from other parts by distinct boundary surfaces; for example water exists in three phases: solid ice, liquid, and vapour, which do not mix.
- Phase boundary
-
The line or surface separating phases in the real world, or in a "phase diagram" representing the stability conditions of different phases.
- Phase changes
-
The transition of a compound from one phase to another, typically in response to a change in temperature or pressure.
- Phase diagram
-
A graphical representation showing the conditions of temperature, pressure, or composition in which different phases are stable
- Phospholipids
-
Lipids involving a phosphate (PO₄)³⁻ group that gives one end of the molecule hydrophilic characteristics. Phospholipids are essential to the formation of cell membranes.
- Phosphorus
-
The fifteenth element of the periodic table, essential to living things in the formation of membranes and the transfer of energy
- Photic
-
Relating to the zone where sunlight can penetrate into a waterbody.
- Photosphere
-
The visible surface of the Sun.
- Photosynthesis
-
The production of reduced carbon compounds from water and carbon dioxide using light as an energy source, carried out by cyanobacteria, many algae, and plants.
- Phyllite
-
Metamorphic rocks intermediate in grain-size between slate and schist
- Phylum
-
A taxonomic group larger than a class but smaller than a kingdom.
- Physical Weathering
-
Weathering that forms fragments of rock, without chemical change.
- phytoplankton
-
free-floating plants
- Piedmont Glacier
-
A glacier formed when one or more valley glaciers flow out into a broad lowland or a larger valley.
- Pillow Lava
-
Masses of mafic rock formed when mafic lava in the ocean rapidly cools by contact with water, forming balloon-like bodies.
- Placer Deposits
-
Mineral deposits formed at the Earth's surface by sedimentary processes, typically the concentration of dense minerals by water flow.
- Planet
-
A large, approximately spherical body (diameter greater than 850 km) of rock, liquid and/or gas in orbit around the Sun or another stars
- Planktonic
-
Organisms capable of suspension within the water column due to their small size
- Plasma
-
A high-temperature form of matter wherein the electrons of each atom are freed from the nuclei.
- Plastic flow
-
Continuous deformation of crystalline materials that takes place after a yield stress is exceeded
- Plate
-
A rigid, moving part of the Lithosphere
- plate tectonics
-
A theory that the Earth has a lithosphere that is divided into relatively rigid moving plates that interact along plate boundaries
- Platforms
-
Portions of a craton that have been covered in sedimentary rock.
- Platinum group elements
-
Six metallic elements with similar properties: Ruthenium, Rhodium, Palladium, Osmium, Iridium and Platinum.
- plucking
-
Glacial plucking describes a process where a moving glacier removes bedrock fragments that have become surrounded by ice
- Plumbline
-
A vertically hanging thread suspending a weight, used to define the vertical direction using the force of gravity.
- Pluto
-
A dwarf planet once considered the ninth planet from the Sun.
- Plutons
-
Large igneous intrusions
- point cloud
-
A data set of arbitrarily located points, each of which is represented by three coordinates, typically representing an easting, a northing, and an elevation
- Point-bar
-
The inner edge of a river’s meander, where sediment can accumulate due to the slower flow of water.
- Polar (Arctic) Amplification
-
The phenomenon whereby changes in the energy cycle have greater effect near the poles
- polar (latitude)
-
Close to either the North Pole or the South Pole
- Polar (substance)
-
A molecule with distinct positive and negative electric charges on either end
- Polar Easterlies
-
Low altitude polar winds that move air from east to west and towards the polar front.
- Polar Front
-
A low-pressure belt where warm air from the tropics and cold air from the pole converge, typically producing cloud and preciptitation
- Pollen
-
Microscopic grains containing the male reproductive cells of plants, dispersed through air or by pollinating insects
- Polymers
-
Long, chain-like molecules with repeating components.
- polymorph
- Polymorphs
-
Minerals with the same chemical composition, yet a different structure.
- Polythermal
-
A glacier with both cold-based and warm-based ice in different areas or at different times
- poorly sorted
-
Having a very wide range of grain sizes
- population
-
Multiple individuals of one species living in the same area
- Porosity
-
The proportion or percentage of space in a solid that may be filled by fluids.
- Porphyry
-
Igneous rocks with both fine and coarse mineral grains.
- Porphyry Copper
-
Copper sulphide deposits typically associated with porphyritic igneous rock.
- Positive Feedback
-
A cycle in which the products of a process act as inputs increasing the activity of the same process
- Potash
-
An evaporite rock composed mainly of potassium-rich minerals that precipitated from evaporating brine.
- Precession of the equinoxes
-
The rotation of the Earth’s tilted axis of rotation, which causes a change in the position and timing timing of the solstices and equinoxes relative to the axes of the Earth's elliptical orbit
- Precipitation
-
Water or ice condensed from the Atmosphere that falls on the Earth's surface
- Presolar nebula
-
The hypothesized nebula where the Sun and Solar System condensed from more dispersed dust and gas
- Pressure
-
The force per unit area exerted by a fluid on its surroundings
- Pressure Solution
-
The dissolution of mineral grains due to compressive stress.
- Pressure-Gradient Flow
-
The flow of air from a region of high pressure to one of low pressure.
- primary porosity
-
Porosity developed at the time a rock is formed
- Primary Producers
-
Autotrophs such as plants and phytoplankton that capture energy from their inorganic environment, represent the first trophic level in an ecosystem
- Primates
-
An order of mammals that includes lemurs, monkeys, great apes, and humans.
- Principle of Original Horizontality
-
A principle which states that strata were initially formed as approximately horizontal layers, parallel to the Earth's surface.
- Principle of Superposition
-
A principle in geology which states that the younger strata formed above older strata.
- Proglacial
-
Formed in the environment immediately outside the terminus of a glacier
- Prograde
-
The counterclockwise rotation (when viewed from above Earth's north pole) that a majority of objects in the Solar System show.
- Prograding
-
The expansion of a sediment body into the sea as a result of high sediment supply (e.g. from a river).
- projection
-
In map making (cartography) projection is the process that transforms the 3-dimensional Earth onto a 2-dimensional page or computer screen.
- Prokaryotes
-
Unicellular organisms whose cells lack a nucleus and complex organelles
- protein
- Proteins
-
Molecules consisting of chains of amino acids linked by peptide bonds, that perform innumerable tasks within and outside cells
- Proterozoic Eon
-
The eon before the Phanerozoic, from 2500 to about 539 Ma, during which atmospheric oxygenation, the evolution of multicellular organisms, and Snowball Earth conditions occurred.
- Protists
-
Unicellular eukaryotes that are not plants, fungi, or animals; protists fall into multiple taxonomic groups
- Protolith
-
The original rock-type from which a metamorphic rock was formed
- Proton
-
A particle found in the nucleus of all atoms: protons carry a positive charge.
- Protoplanetary Disk
-
All of the material in the primeval Solar System which did not condense directly into the Sun. This material would instead form the planets, their natural satellites, the asteroids, meteoroids and comets.
- Proxy
-
Information that is not a direct measurement of a physical quantity such as temperature, but which allows the value of that physical quantity to be estimated.
- Pull-Apart Basin
-
A sedimentary basin formed as at releasing bend on a fault such as a transform fault, where motion is near-horizontal.
- Pumice
-
Igneous rock with a foamy texture formed by volatiles in magma that left abundant vesicles in the rock as it cooled.
- Pycnocline
-
The zone within the ocean’s where there is the greatest rate of increase in density with depth occurs.
- Pyrite
-
A mineral sulfide of iron FeS₂ that has yellow colour and metallic lustre.
- Pyroclastic
-
Describes products of explosive volcanic eruptions that produce rock fragments.
- Pyroclastic Flows
-
Fluid mixtures of tephra and hot gas that quickly travel down the flank of a volcano
- Pyroxenes
-
A group of mainly ferromagnesian single-chain silicate minerals common in mafic rocks
- Qualitative
-
Information gathered only through description, without a numerical measurement.
- Quantitative
-
Information gathered as numbers or amounts (for instance, temperature and distance).
- Quartz
-
Silica SiO₂ in its most common mineral form.
- Quartzite
-
Metamorphic rock consisting largely of quartz, commonly formed by metamorphism of sandstone. (Sandstones that are unmetamorphosed but cemented by quartz are sometimes termed orthoquartzite, in which case metaquartzite can be used to distinguish the metamorphic rock.)
- Quaternary Period
-
The most recent and current period of the Cenozoic Era, beginning about 2.6 million years ago. The Quaternary included significant glacial and interglacial intervals.
- Radiant heat
-
Infra-red radiation released by heated objects
- Radiative Forcing
-
The effect of carbon dioxide on the absorption and reflection of solar irradiance as it reaches Earth’s atmosphere.
- Radioactivity
-
The tendency of unstable isotopes to decay and release radioactive particles and gamma rays.
- Radiolaria
-
A group of unicellular marine plankton that construct silica skeletons that settle to the ocean floor
- Radiolarian Ooze
-
A form of siliceous ooze originating from the exoskeletons of Radiolaria
- Radiometric dating
-
Radiometric or isotopic dating: determination of the age of a substance using amounts of elements involved in radioactive decay
- Rain shadows
-
A region of dry conditions on the downwind side of a mountain belt, due to precipitation of moisture as air moves over the mountains.
- Raised beach
-
Elevated terraces along shores that arise uplift, typically due isostatic rebound following the removal of glacial ice.
- Ranks
-
Divisions recognized between coal types, based on increasing carbon content.
- Rayleigh Waves
-
Seismic surface waves that produce vertical motions of the ground surface.
- Recessional Moraines
-
Bodies of till left by successive positions of a glacier terminus during glacier retreat of a glacier.
- Recharge
-
The addition of water over time to a groundwater reservoir
- Recurrence Interval
-
The average time between successive floods greater than or equal to a specified magnitude.
- Reduced
-
The state of an atom when an additional electron is added during a reaction; opposite of oxidation
- Reduced Carbon
-
Carbon that has gained electrons by bonding with other carbon atoms and/or hydrogen
- Reduction
-
The removal of oxygen or the addition of hydrogen to an element or compound, or, more generally, any chemical reaction that results in a gain of electrons
- Reef
-
A raised, wave-resistant mound or ridge on the sea-floor, formed mainly of calcium carbonate deposited by organisms such as corals and algae
- refraction
-
A phenomenon affecting all kinds of waves, whereby waves impinging obliquely on a boundary where their velocity changes experience a change in the direction of wave propagation
- Region of discharge
-
An area groundwater flows out through the surface of the Geosphere, for example at springs or as baseflow into streams.
- Regional Metamorphism
-
Metamorphism that affects large areas of orogenic belts, produced by temperature, pressure and deformation
- Regolith
-
Weathered material that remains in its original position, without removal by erosion. Regolith mixed with plant material is called soil.
- relative humidity
-
The vapour pressure of water in air at a given temperature divided by the saturation vapour pressure at the same temperature.
- relativity
-
A group of theories in physics that state that the laws of mechanics and the speed of light are the same for all observers, even if those observers are moving relative to each other
- Releasing Bends
-
A bend on a fault where the two walls of the fault move slightly apart
- Remanent Magnetism
-
Permanent magnetism that was acquired at the time of rock formation and preserved until the present day.
- Renewable resources
-
Materials or energy supplies, useful to humans, that are replenished at a rate comparable to that of human consumption.
- Reproduction
-
The copying and replication of molecules and organisms
- Reserves
-
Resources that can be exploited economically under present conditions.
- Residence time
-
The average time that a molecule remains in a reservoir; obtained by dividing the size of the reservoir by the flux in or out of the reservoir
- Resources
-
Naturally occurring accumulations of useful material in concentrations and amounts that make extraction by humans currently or potentially feasible.
- Respiration
-
The oxidation of reduced (organic) carbon compounds by an organism to yield energy, carbon dioxide and water
- Restraining Bends
-
Bends along the sides of a fault where both sides push slightly together.
- retreat
-
The movement of the terminus of a glacier in the opposite direction to ice flow, so that less land is progressively covered by ice; Typically occurs when ablation exceeds accumulation.
- Retrograde
-
The clockwise rotation (when viewed from above Earth's north pole) that a minority of objects in the Solar System show.
- Rhombohedron
-
A solid shape the faces of which are all parallelograms.
- Rhyolite
-
A hard extrusive felsic igneous rock, the fine-grained equivalent of granite.
- Richter Magnitude
-
A measure of earthquake magnitude based on displacement at a standardized distance; in modern work, largely superseded by moment magnitude
- Ridge-push force
-
One of the driving forces of plate tectonics, caused by the tendency of plates to move down the flanks of mid-ocean ridges because of the force of gravity.
- Rift
-
A belt of stretched lithosphere, typically marked by one or more fault-bounded valleys
- Rifting
-
Stretching of the lithosphere along a belt marked by faults
- Right-lateral
-
Dextral: fault motion such that the far wall of a fault appears displaced to the observer's right
- Rip current
-
A narrow current of water flowing offshore, supplied by longshore currents.
- River capture (or river piracy)
-
The diversion of water from one stream into another channel, as a result of progressive river erosion (usually headward erosion).
- River terraces
-
Flat areas on the sides of a river valley, and elevated above present-day floodplain level. Terraces are formed when renewed downcutting carves through a former floodplain.
- RNA
-
Ribonucleic acid. A single-stranded nucleic acid that acts as to transfer genetic information in the production of proteins
- Roche moutonnée
-
Rock affected by glacial erosion that has a smooth upstream side due to abrasion and a rugged downstream side due to plucking
- rock
-
A naturally occurring mixture of minerals, and in some cases other solid materials, that occurs in the Geosphere
- Rock Cycle
-
The process by which igneous, sedimentary, and metamorphic rocks arise through cycling of material through the Earth's outer layers
- Rock Salt
-
The rock composed mainly of the mineral halite NaCl
- Rodinia
-
An ancient supercontinent preceding Pangaea. Rodinia existed during the Proterozoic Eon.
- Rolling
-
Rotating movement of particles along the bed of a river.
- Rossby Waves
-
Large-scale undulations of the polar front and the jet stream
- Rotational slide
-
The movement of a rock mass down slope along a curved failure surface.
- Runaway Feedback
-
The change of a system towards an extreme position relative to its starting state, as a result the amplification of an initial change by positive feedback
- Runout
-
The extent of a flow beyond the slope on which it originated
- Rupture
-
A slipped region of a fault surface
- S-Waves
-
Seismic body waves in which the vibration direction is at 90° to the propagation (travel) direction
- Saline
-
Containing a high concentration of dissolved salts
- Salinity
-
The concentration of dissolved salts in water.
- Salt Domes
-
Upwarped regions in the crust produced by rising columns of rock salt and other evaporite rocks
- Salt Glaciers
-
A flow of salt that emerges onto the Earth’s surface and then flows slowly down slope
- Saltation
-
The movement of particles in water as part of bed load, with a jumping motion. Particles are pulled briefly upward out of the bed by pressure effects, and carried downstream as they fall back to the bed.
- Sand
-
Clastic sediment with a grain-size finer than 2 mm but coarser than 1/16 mm
- Sandstone
-
Clastic sedimentary rock formed from lithified sand (sediment with grains finer than 2 mm, but coarser than 1/16 mm)
- Sandstorms
-
A suspension of sand in the troposphere by powerful winds.
- Satin Spar
-
A crystal form of gypsum with long fibres.
- Saturated
-
The maximum or equilibrium amount of a substance that can be held in another. Saturated solutions contain the maximum amount of dissolved material that is in equilibrium with adjacent solid. The saturated zone of groundwater has porosity entirely filled with liquid.
- Saturated Zone
-
The groundwater zone where pore spaces are entirely filled by water.
- Saturation Vapour Pressure
-
The maximum concentration of water vapour in air when at equilibrium with liquid water or solid ice.
- Saturn
-
The sixth planet from the Sun; a Jovian planet noted for its visible ring system
- Schist
-
A metamorphic rock with a strong fabric (foliation) usually due to oriented, sheet-like grains of mica.
- scientific law
-
A theory or part of a theory that has withstood repeated testing and can be succinctly stated in words or as a mathematical equation.
- Scoria
-
Porous, highly vesicular rock derived from lava; may form on the surface of a lava flow, or during its pyroclastic disruption.
- Scree
-
Fallen rock material that accumulates at the base of a steep slope.
- Sea Breeze
-
Wind that blows from sea to land, typically during the day, caused when low pressure develops because of heating of the land by the sun. Cooler air from the sea replaces rising air over land.
- Sea ice
-
Ice that has formed on the sea surface by freezing of seawater
- Sea ice extent
-
the proportion of the ocean covered in ice at a given time.
- Sea stacks
-
Upstanding masses of rock isolated from adjacent sea cliffs by erosion.
- Seam
-
A layer, or bed, of coal
- secondary porosity
-
Porosity formed by solution, at some time after deposition of the rock
- Sediment
-
Material derived ultimately from weathering, that is transported and/or deposited as grains on the surface of the Geosphere
- Sediment gravity flows
-
The transportation of mixed sediment and water down slope through gravity.
- Sedimentary
-
Relating to sediment, material derived ultimately from weathering, that is transported and/or deposited as grains on the surface of the Geosphere
- Sedimentary rock
-
Rock deposited on the surface of the Geosphere by the action of the Atmosphere, Hydrosphere or Biosphere, formed from the products of the weathering and erosion of older rock
- Seeps
-
Areas on the surface of the Geosphere where petroleum (oil or natural gas) escapes.
- Seismic
-
Relating to earthquakes.
- Seismic reflection
-
The behaviour of seismic waves that encounter a boundary within the Earth, causing some of the energy to return away from the boundary on the same side as their source
- Seismic Waves
-
Disturbances generated by a natural earthquake or by artificial means, that propagate as vibrations through the Geosphere and over its surface.
- Seismographs
-
A device used to create a record of shaking resulting from an earthquake
- Seismologists
-
Physicists who study earthquakes and the propagation of waves through the solid Earth
- Seismometer
-
A device used to measure shaking resulting from an earthquake
- Selection Pressure
-
The action of environmental conditions in causing natural selection by favouring the survival of certain variants of a species over others.
- Selenite
-
A crystal form of gypsum that is transparent and colourless.
- Shadow Zone
-
An area on the Earth's surface where seismic body waves from an earthquake are blocked by the Core
- Shale
-
Mudstone that is fissile (ie with clay minerals aligned due to compaction causing it to break into thin flakes.
- Shale Gas
-
Natural gas is trapped within fine-grained sedimentary rock.
- Shear Stress
-
The component of stress that acts parallel to a given surface within the Earth.
- shear stress
-
Force per unit area acting parallel to a surface
- Shear Zones
-
Narrow zones of intense deformation accommodating movement between more rigid blocks of rock.
- Sheet Silicates
-
Silicates whose crystal structure contains sheets in which three oxygen atoms are shared between silicate tetrahedra.
- Sheeting
-
The cracking of previously buried rocks into sheets as they are brought close to Earth’s surface
- Shield Volcanoes
-
Gently-sloping volcanoes formed by mafic lava flows that travel over long distances.
- Shields
-
Areas of cratons (stable continental crust) where Archean or Proterozoic metamorphic and igneous rocks are exposed.
- Silica
-
Silicon dioxide SiO₂
- Silicate
-
A substance containing covalently bonded silicon and oxygen groups in its atomic structure
- Silicate Minerals
-
Naturally occurring crystalline solids whose composition includes groups of silicon and oxygen atoms, typically in a covalently bonded tetrahedral arrangement
- Silicate Tetrahedron
-
Silicate Tetrahedron (Also silica tetrahedron or SiO₄ tetrahedron; plural tetrahedra): A group of four oxygen atoms covalently bonded to a silicon atom; the basic building block of silicate minerals.
- Silicates
-
Substances with silicon–oxygen groups in their atomic structure
- Siliceous ooze
-
Deep-sea deposits of fine grained sedimentary opal derived from organisms with silica skeletons such as diatoms and Radiolaria.
- Sills
-
Sheet-like igneous intrusions are concordant with layers in their host rock
- Silt
-
Mud particles with diameters between 1/16 mm and 1/256 mm (or 4 μm)
- Sinistral
-
Fault motion such that the far wall of a fault appears displaced to the observer's left
- Sinks
-
Reservoirs in a system where the residence time is so long that it effectively remove material from a cycle
- Sinuous
-
Having a large number of bends (e.g. of a river channel)
- Slab-pull
-
One of the driving forces of plate tectonics; the force produced by high-density metamorphic rocks in a subducted slab of oceanic lithosphere.
- Slate
-
A low-grade metamorphic rock with fine grain size and fabric (cleavage) that typically causes the rock to split into thin flakes or sheets
- Slide (bed-load behaviour)
-
The movement of particles along the bed of a river without rotation.
- Slide (mass wasting)
-
Mass downslope of coherent material along a basal failure surface
- Slip
-
The relative movement of blocks on either side of a fault
- Slope
-
The deviation of a surface from horizontal; may be measured as an angle or as a tangent (rise or fall divided by horizontal "run").
- Slot canyon
-
A valley with exceedingly steep sides, created when a channel downcuts through strong rocks.
- Slow Carbon Cycle
-
The flows of carbon through inorganic processes within the Geosphere, with residence times measured in millions of years
- Slumps
-
Slides in which the moving mass is significantly deformed; transitional into flows.
- Snow
-
Ice crystals formed by condensation directly from water vapour, that fall as precipitation
- Snowball Earth
-
A climate state in which a majority of the Earth's surface is covered with snow or ice. Snowball Earth conditions are believed to have occurred during several intervals in the Proterozoic Eon.
- snowline
-
The level on a glacier, or more generally on any sloping land surface, above which snow persists year-round
- Soil
-
A mixture of weathered, fragmented rock and organic matter at the surface of the Geosphere
- Solar energy flux
-
The rate of energy input from the Sun that could theoretically be received by a unit area of the Earth’s surface.
- Solar Forcings
-
Changes in the energy output of the sun which may affect Earth’s climate.
- Solar System
-
The Sun and all of the natural objects (including planets, their natural satellites, dwarf planets, comets, asteroids and meteoroids) in its orbit.
- Solar Wind
-
Matter (plasma specifically) released from the surface of the Sun that carries small amounts of energy throughout the solar system.
- Solid Solution
-
A mineral or mineral group in which two (or more) different elements may be present in a continuous range of proportions.
- Solidus
-
A boundary on a phase diagram separating fully solid material from material with some liquid; the start of melting.
- Solifluction
-
Creep observed when groundwater freezes and thaws, allowing sediment grains to move down the slide at an annual rate.
- Solifluction lobes
-
Rounded bodies of soil or sediment formed by creep of the active layer when it is saturated and lies on a slope.
- Solstice
-
Two times in an Earth year at which one of the poles is directly tilted towards the Sun.
- Sorting
-
The process in sedimentation wherein particles are separated on the basis of size, or the degree to which the particles in a sediment have been sorted, producing a narrow range of sizes.
- Southern Oscillation (ENSO)
-
A two-stage climate pattern operating over periods of several years in which water in the central and easter Pacific Ocean is alternately warmer and colder than average, impacting the flow of water in the Pacific and global weather patterns
- Species
-
The smallest conventional taxonomic group; typically defined as a group of organisms capable of reproducing and producing with viable offspring that can also reproduce. Species are grouped into genera.
- Specular Hematite
-
A black variety of hematite with a highly reflective metallic lustre
- Spinel
-
A mineral oxide of magnesium and aluminum; also, a mineral group of similar structure in which different metallic ions are present (eg Fe, Mn, Cr).
- Spit
-
Peninsulas of beach sediment extending away from the shore into the sea:
A depositional landform formed by longshore drift of sediment.
- Sponges
-
Primitive multicellular animals that lack true tissues and organs; most are filter-feeders
- spreading centre
-
A plate boundary where plates are moving apart, away from the boundary
- Spring
-
Natural points of groundwater discharge that occur when the water table or a permeability boundary intersects the land surface.
- Spring tide
-
A tidal phenomenon caused by the alignment of the Moon, Sun, and Earth along a single line, producing a maximum tidal range and accentuating tidal effects.
- Stable
-
A state wherein a compound is unlikely to undergo a phase change or chemical reaction.
- Stable Isotopes
-
An isotope that is able to persist over long periods of time without decay
- Stalactites
-
Dripstone formations that taper downward from the ceilings of caves.
- Stalagmites
-
Dripstone formations that rise upward from the floor of caves.
- Starch
-
A complex carbohydrate polymer used by plants to store energy.
- Steady State
-
A system without a net flux of materials in or out; a steady state describes a system that remains unchanging over time.
- stomata
-
Openings on plant leaves that allow plants to exchange gases with their surroundings
- Stone Age
-
A phase in human history when tools were made primarily from rock materials
- Storm surge
-
Local rise in sea level along a coast beneath a major storm due to the combined effect of onshore wind and reduced air pressure
- Strain
-
A change in shape or volume
- Stratigraphic Column
-
A description of sedimentary layers in the form of a columnar diagram, with the oldest layers at the bottom and the youngest at the top
- Stratocumulus
-
Low altitude clouds that are generally horizontally extensive, like stratus, though displaying domed or clumped features resembling cumulus
- Stratopause
-
The boundary dividing the mesosphere and stratosphere in Earth’s atmosphere. Here, the temperature reaches its peak between the two layers.
- Stratovolcanoes
-
Conical volcanoes consisting of alternating layers of lava and tephra, typical of intermediate magma compositions.
- Stratum
-
Stratum (plural strata): a layer of rock, typically sedimentary
- Stratus
-
Clouds that form horizontal, flat layers at low altitudes. Typical of warm fronts.
- Streak
-
The colour of mineral when finely powdered
.
- Streak Plate
-
An unglazed tile used to obtain a streak colour by abrading the mineral against its surface
- Stream flow
-
The movement of water through confined channels over Earth’s surface.
- Stress
-
The force per unit area exerted on a plane, or the combination of all such forces exerted at a point within a solid.
- Striae or striations
-
Grooves carved in bedrock as a result of glacier movement
- Strike Slip
-
Near-horizontal movement between two blocks separated by a fault.
- Stromatolites
-
Finely layered (laminated) mounds or pillars of calcium carbonate deposited by cyanobacteria
- Subduction
-
The plate tectonic process whereby one plate descends beneath another as plates converge
- Subduction Zone
-
A convergent plate boundary where one plate descends beneath another.
- Subglacial
-
Formed below a glacier
- Subglacial lake
-
A lake hidden below glacier ice
- Sublimation
-
The phase change of solid directly to gas, without liquid as an intermediary step.
- Submarine canyons
-
Steeply descending valleys in the sea-floor, typical of the continental slope.
- Submarine Fans
-
Seafloor sediment bodies typically formed at the downslope end of submarine canyons. Sediment is distributed by turbidity currents over an area that is often roughly semi-circular.
- Substitute
-
An element or ion in a crystal lattice that replaces another, typically of similar size and electron configuration
- Substitution
-
A phenomenon where by an element or ion in a crystal lattice is replaced by a different element
- Sulfate Ions
-
Negative ions consisting of sulfur and oxygen: SO₄²⁻
- Sulfate Minerals
-
Minerals containing oxidized sulfur in the form of sulfate ions with the formula SO₄²⁻
- Sulfides
-
Minerals containing negative ions of reduced sulfur.
- Sunspot
-
A dimmer patch on the photosphere of the Sun associated with magnetic storms
- Sunspot Cycle
-
The 11 year-long rise and fall in sunspot activity across the surface of the Sun, associated with a minor change in irradiance
- Supercontinent
-
A large conglomeration of continental lithosphere, typically including the majority of continental crust on Earth at a given time.
- supercritical fluid
-
High pressure fluid that combines properties of a liquid and a gas
- Surf zone
-
The coastal area in which wave crests move faster than deeper water inhibited by drag against the seafloor. As a result, turbulence occurs as waves break over one another.
- Surface currents
-
Ocean currents at the top of the top of the water column, caused by wind and tides, additionally deflected by the Coriolis effect.
- Surface Tension
-
A feature of liquid surfaces that tends to reduce the area of surface.
- Surface Waves
-
Seismic waves that travel along the surface of the Geosphere
- Suspend
-
The process whereby particles remain above the bed of a body of water, because they are carried upward by fluid turbulence at a rate faster than their speed of settling.
- Suspended Load
-
Fine-grained sediments that may be suspended within turbulent waters.
- Symbiogenesis
-
The evolutionary process whereby eukaryotic organisms developed from prokaryotic ancestors: one prokaryote evolved to enclose another in a mutually supportive relationship chloroplasts and mitochondria developed through symbiogenesis.
- Symbiosis
-
A close association between two organisms, whereby both gain benefits from the relationship
- System
-
A portion of the universe that can be regarded as separate from its surroundings for some scientific purpose.
- Talus
-
Scree; fallen rock materail accumulated at the base of a cliff or other steep slope
- Taxonomy
-
The categories and methods used by biologists to classify living organisms
- Tectonic
-
Relating to movements of the Earth's lithosphere
- temperature
-
A measure of the average kinetic energy of the atoms or molecules in a material, typically measured on the Celsius (°C) or Kelvin (K) scale
- Tephra
-
Rock fragments generated by volcanic eruptions
- Terminal Moraine
-
A body of till marking the furthest extent of a glacier’s ice.
- Terminus
-
The lower limit of a glacier
- Terrestrial
-
Associated with the Earth
- Terrestrial (Inner) Planets
-
The four innermost planets of the solar system believed to have iron-rich cores surrounded by rocky mantles, without the thick atmospheres characteristic of the outer planets.
- Terrigenous
-
Sediment originating from land.
- Texture
-
The sizes, shapes, and relationships between the mineral grains that make up a rock.
- theory
-
A hypothesis, or group of hypotheses, that has survived many experimental or observational tests, leading to general acceptance of its explanatory power
- Thermocline
-
The depth zone within the ocean’s where the greatest rate of downward temperature decrease is observed.
- Thermohaline Circulation
-
The movement of water currents throughout the oceans as a consequence of differemces om temperature and salinity
- Thermohaline Currents
-
Deep ocean currents driven by differences in temperature and salinity.
- Thermosphere
-
The layer of the Atmosphere above the Mesopause, where temperature increases with elevation.
- Thrust Fault
-
A gently sloping fault where the hanging wall has moved up the slope of the fault over the footwall.
- Thunderstorm
-
A severe weather system with rain and/or hail together with electrical discharges (lightning) that cause thunder
- Tidal Range
-
The vertical distance between high and low tide levels at a point on the Earth's surface.
- Tides
-
The change in Earth’s surface elevation (particularly water surfaces) due to changes in the gravitational pull of the Moon and Sun.
- Till
-
Unsorted sediments deposited directly from glacier ice
- Tillite
-
Lithified till: Unsorted sediments deposited directly from glacier ice, subsequently solidified
- Topography
-
The variation in elevation from place to place on the surface of the Geosphere, on land. (The corresponding measurement of the seafloor is bathymetry.)
- Tornado
-
A narrow and intense spiral updraft that commonly develops from a funnel cloud, and features very low pressure at its centre.
- Toxic
-
Describes a substance that inhibits the growth, reproduction, or survival of an organism
- Toxins
-
a substance that inhibits the growth, reproduction, or survival of an organism
- Trace Fossils
-
Structures in rocks that preserve evidence of past organisms’ movement or other activity; also known as ichnofossils.
- traction
-
Force per unit area; also known as stress
- Trade Winds
-
Persistent east-to-west winds in the tropics that were used for trade by sailing ships. The term "tropical easterlies" is preferred in this text.
- transcurrent
-
Describes tectonic motion that is mostly horizontal and parallel to a tectonic boundary
- Transform Fault
-
A plate boundary where relative plate motion is parallel to the boundary.
- Translational Slide
-
The movement of a rock mass down slope along a planar failure surface.
- Transpiration
-
The transfer of liquid water to water vapour in the atmosphere at plant surfaces.
- Tree Rings
-
Cylindrical structures developed in the woody stems of trees, typically one per year
- Trench
-
Deep troughs on the ocean floor where oceanic lithosphere is subducted at a convergent plate boundary
- Tributaries
-
Smaller streams that flow and converge downstream into a larger channel.
- Triple Point
-
A point in a phase diagram where a substance (such as water) can remain in equilibrium in the liquid, gas, and solid states simultaneously.
- Tropical Cyclone
-
A cyclonic storm that develops north or south of the intertropical convergence zone. A storm must achieve a windspeed >120 km/hr to be considered a tropical cyclone.
- Tropical Easterlies
-
Persistent east-to-west winds that flow in the tropics
- Tropical storm
-
A cyclonic storm with a wind speed less than >120 km/hr that nevertheless forms from warm moist air north or south of the intertropical convergence zone
- Tropopause
-
The boundary lying between the troposphere and the stratosphere, where temperatures reach a minimum after decreasing with altitude in the troposphere, and before increasing once again in the stratosphere.
- Troposphere
-
The lowest part of Earth’s atmosphere directly in contact with the surface of the Earth, which warms it from below, leading to an upward decrease in temperature. The troposphere contacts the stratosphere at the tropopause.
- Tsunami
-
A wave on the ocean surface resulting from an earthquake, volcanic eruption or a landslide.
- Tuff
-
Solid pyroclastic rock formed from lithified tephra.
- Turbid
-
Cloudy water caused by suspended load.
- Turbidity Current
-
A turbulent flow of sediment-rich water moving down slope under clearer water due to the action of gravity.
- Turbulence
-
Swirling movements in a fluid that developed due to the velocity of a current.
- Turbulent
-
Having turbulence: wirling movements in a fluid.
- Turbulent flow
-
Fluid movement where swirling and mixing within the fluid allows sediment suspension.
- Twin Planes
-
A plane within a crystal across which the crystal lattice adopts a reflected or rotated orientation
- Typhoon
-
A tropical cyclone in the North Indian Ocean or West Pacific
- Ultramafic
-
Magma or igneous rock with a silica content of less than 45%
- Ultraviolet
-
Electromagnetic radiation with wavelength slightly shorter than visible light, and frequency slightly higher, lying beyond violet in the electromagnetic spectrum.
- Unconfined aquifer
-
An aquifer where the upper boundary is the water table
- Unconformity
-
An ancient erosion surface where younger sediment was deposited on eroded older rock
- unconventional
-
Unconventional hydrocarbons are those contained in low-permeability rocks, that do not flow out of the rocks without intervention
- unicellular
-
consisting of a single biological cell
- uniformitarianism
-
The principle that processes that operated in the Earth's past can all be explained by processes that continue to operate at the present day. Strict application of uniformitarianism in Earth science has largely been replaced by actualism
- Unstable Isotope
-
An isotope whose nucleus undergoes randomly decay.
- Upwelling
-
Rise of deeper water to the surface, typically due to Ekman transport that forces water away from a coasts.
- Uranus
-
The seventh planet from the Sun. Uranus is a Jovian planet with a rotational axis with obliquity of nearly 90°
- UTM
-
Universal transverse Mercator
- Vadose zone
-
In groundwater study, the zone above the water table where pore spaces are partly filled by water. (Also known as the aerated zone.)
- Valley Glacier
-
An elongated glacier formed as ice from higher elevations flows between exposed rocky slopes.
- Valley wind
-
The rise of warm air up mountain sides during the day
- Varves
-
Alternating layers deposited in lakes, representing annual glacial melt events.
- Veins
-
Cracks in rock that have been filled by minerals.
- Velocity
-
A measure rate of motion that includes both speed and direction.
- Velocity gradient
-
The rate of change (with distance) of velocity in a fluid such as water
- Vents
-
Pipe-like channels up which magma may flow.
- Venus
-
The third planet from the Sun known for its similar size to Earth; the brightest planet in Earth's night sky
- Vesicles
-
Rounded cavities in igneous rock formed by gas bubbles in the magma.
- Vine-Matthews-Morley Hypothesis
-
The hypothesis that symmetrical patterns of linear magnetic anomalies on the ocean-floor have been produced by ocean-floor spreading combined with reversals of the Earth's magnetic field.
- virus
-
A particle usually consisting of nucleic acid wrapped in protein that can reproduce when it invades a host organism and takes over some of the host's living processes to achieve reproduction
- Viscosity
-
A measure of the resistance of a fluid to shearing; measured as the force concentration needed to achieve a given velocity gradient. In everyday terms, a measure of hhow 'thick' a fluid is.
- Viscous
-
Describes liquids with high ability to resist flow
- Viscous Behavior
-
The behaviour of liquids (or solids near their melting point) in which the material deforms at a rate proportional to the applied stress.
- Vitreous Lustre
-
Vitreaous (glassy) lustre: Describes the image-forming reflection of light from the surfaces of a mineral that also has some transparency.
- Volatile
-
Dissolved water and gas in magma, or the behaviour of such material
- Volcanic
-
Relating to volcanoes: places where magma reaches the surface of the Geosphere as lava
- Volcanic Arc
-
A chain of volcanoes that lies above a downgoing slab of lithosphere at a subduction zone
- Volcanic Ash
-
Fine-grained tephra less than 2 mm in diameter.
- Volcanic Bombs
-
Volcanic fragments larger than 64 mm in diameter that are released in explosive eruptions.
- Volcanic Glass
-
Igneous rock formed by rapid cooling of lava, such that crystal lattices are unable to form; rock with the structure of a supercooled liquid.
- Volcanic Massive Sulfide
-
Metal sulphide deposits formed typically where hydrothermal vents allow hot water to deposit metal-bearing sulfide minerals within and upon ocean floor.
- volcanic massive sulphide
-
A type of mineral deposit formed by hydrothermal fluids flowing through igneous rock, typically rich in copper and other elements
- Volcanoes
-
Places where magma reaches the Geosphere surface.
- Wadati-Benioff Zone
-
A sloping zone of deep earthquakes associated with a convergent plate boundary
- Warm front
-
A boundary between air masses where warm air advances towards and over cold air
- Warm-based Ice
-
Glacial ice that is close to freezing point, and has liquid water at base.
- Water
-
A compound critical for life on Earth, consisting of two hydrogen atoms and one oxygen: H2O.
- Water Cycle
-
The continuous transport of water between the various spheres of the Earth through a series of reservoirs
- Water table
-
The divide between the saturated and vadose zones of groundwater.
- Water vapour
-
Water in its gaseous state, a colourless invisible gas
- Watershed
-
A synonym for drainage basin, in North America. In UK English, the drainage divide between two drainage basins
- Wave Orbitals
-
The circular or elliptical motion of particles beneath a wave
- Wave-base
-
The maximum depth below the water surface at which sediment is affected by motion from waves.
- Wavelength
-
The distance between the two successive maximum values or crests in any wave-like phenomenon.
- Weather
-
Short-term changes in Earth’s atmosphere
- Weathering
-
The breakdown of rock material at the Geosphere surface due to the action of the Atmospher, Biosphere, and or Hydrosphere.
- Well Sorted
-
Sedimentary deposits with particles of about the same size.
- Westerlies
-
Winds that blow from west to east, most typically at mid-latitudes, where they are driven by a combination of pressure-gradient flow and the Coriolis effect
- WGS84
-
world geodetic system 1984
- Xenoliths
-
Fragments of host rocks that are embedded within an igneous intrusion.
- Year Without A Summer
-
The year 1816 CE; a short-term cooling in climate occurred during the growing seasons of the Northern Hemisphere, possibly due to the long-term effects of a volcanic eruption of Mount Tambora, Indonesia