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

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

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

 

 

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