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Geosciences LibreTexts

23.2: Glossary

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  • For each entry the chapter in which the word first appears is shown in parentheses.


    aa (4) a lava flow that solidifies with a blocky high-relief surface

    ablation (16) melting of ice in the context of glaciation

    ablation till (16) till that is formed when englacial and supraglacial sediments are deposited because the ice that was supporting them melts

    abyssal plain (18) the flat surface of the deep ocean, typically beyond the limits of the continental slopes

    abyssalpelagic zone (18) the deeper parts of the ocean, between 4000 and 6000 m.

    accretion (plate tectonics) (21) the process by which continental blocks (terranes) are added to existing continental areas

    accretion (planetary) (22) the process by which solid celestial bodies are added to existing bodies during collisions

    acid rock drainage (5) the production of acid from oxidation of sulphide minerals (especially pyrite) in either naturally or anthropogenically exposed rock

    aeolian (6) processes related to transportation and deposition of sediments by wind

    aerobic (18) processes that take place in the presence of abundant oxygen

    aerosol (4) an aggregate of fine solid particles or a small droplet of liquid suspended in the air

    aftershock (11) an earthquake that can be shown to have been caused by another earthquake

    aggregate (20) unconsolidated materials (typically sediments) that are used in the construction industry

    albedo (19) the reflectivity of a surface of a planet (expressed as the percentage of light that reflects)

    albite (2) sodium-rich plagioclase feldspar

    alpine glacier (16) a glacier formed in a mountainous region and confined to a valley (same as valley glacier)

    amphibole (2) a double-chain ferromagnesian silicate mineral (e.g., hornblende)

    amphibolite (7) a foliated metamorphic rock in which the mineral amphibole is an important component

    amplification (11) in the context of seismic shaking the process by which the amplitude of the seismic waves are enhanced, especially because the

    amplitude (17) for any type of wave, the difference in height between a crest and the adjacent trough

    anaerobic (18) processes that take place without oxygen

    andesite (3) a volcanic rock of intermediate composition

    anion (2) a negatively charged ion

    angular unconformity (8) a geological boundary at the base of a sedimentary layer where the sedimentary rock beneath has been tilted or folded and then eroded

    anorthite (2) calcium-rich plagioclase feldspar

    Antarctic Bottom Water (18) water at abyssal depths in the ocean that forms from the sinking of dense cold water adjacent to Antarctica

    anticline (12) an upward fold where the beds are known not to be overturned

    anthracite (20) a high grade of coal (92 to 98% carbon) that is formed from deep burial and weak metamorphism

    anthropogenic (19) resulting from the influence of humans

    antiform (12) an upward fold where it is not known if the beds have been overturned

    aphanitic (3) an igneous texture characterized by crystals that are too small to see with the naked eye

    aquifer (14) a body of rock or sediment that has sufficient permeability to allow it to be used as a source of groundwater

    aquitard (14) a body of rock or sediment that has insufficient permeability to allow it to be used as a source of groundwater

    arch (17) a rock weathering remnant in the form of an arch (typically along a coast and resulting from wave erosion)

    arenite (6) a sandstone with less than 15% silt and clay

    arete (16) a sharp ridge that separates adjacent glacially carved valleys

    arkose (6) a sandstone with more than 10% feldspar and more feldspar than lithic fragments

    arkosic arenite (6) an arkose with less than 15% clay/silt matrix

    artesian well (14) a well that is completed in a confined aquifer and in which the water level in the well rises above the top of the aquifer

    asteroid (22) a rocky body orbiting the Sun

    asteroid belt (22) the region between the orbits of Mars and Jupiter that is populated with many asteroids

    asthenosphere (1) the part of the mantle, from about 100 to 200 km below surface, within which the mantle material is close to its melting point, and therefore relatively weak

    asymmetrical (12) in the context of folds, where the two sides of the fold make significantly different angles with respect to the axial plane

    atoll (18) a ring-shaped carbonate (or coral) reef or series of islands

    atomic mass (2) the total number of neutrons plus protons in an atom

    atomic number (2) the total number of protons in an atom

    attitude (12) the orientation of a sloping geological feature, such as a bedding plane or fracture

    auerole (7) a zone of metamorphism around a source of heat such as a magma body

    axial plane (12) a plane that can be traced through all of the hinge lines of a fold


    back reef (6) the zone of shallow water on the shore-side of a reef

    background (geochemistry) (20) the typical level of an element in average rocks or sediments

    backwash (17) the wash of wave water down the slope of a beach

    banded iron formation (6) an iron-bearing sedimentary rock that is rich in minerals such as hematite and magnetite, which may be interbedded with chert

    bank-full stage (13) the water level of stream when it is in flood and just about to flow over its banks

    barrier reef (18) a carbonate (or coral) reef that forms a barrier to waves along a coast

    basal sliding (16) the motion of glacial ice along the base of a glacier that is warm enough to have liquid water

    basalt (1) a volcanic rock of mafic composition

    base level (13) in the context of a stream the base level is the lowest level that it can erode down to, as defined by the ocean, a lake or another stream that it flows into

    batholith (3) an irregular body of intrusive igneous rock that has an exposed surface of at least 100 km2

    bathypelagic zone (18) the moderately deep parts of the ocean, between 1000 and 4000 m.

    baymouth bar (17) a spit that extends across the mouth of a bay

    beach face (17) the part of the beach that is relatively steep and lies between the high and low tide levels

    bed (6) a sedimentary layer

    bed load (6) the fraction of a stream’s sediment load that typically rests on the bottom and is moved by saltation and traction

    bedding (6) repeated layering in a sedimentary rock

    bentonite (15) a type of smectite clay that has strong swelling properties and is effective at absorbing dissolved ions

    berm (17) a flat area of a beach in the backshore area (above the high tide level)

    big-bang theory (22) the theory that the universe started with a giant explosion approximately 13.77 billion years ago

    biotite (2) a sheet silicate mineral (mica) that includes iron and or magnesium, and is therefore a ferromagnesian silicate

    biozone (8) a stratigraphic interval that can be defined on the basis of a specific fossil

    bituminous (20) a medium-grade type of coal with 70 to 92% carbon

    blueschist (7) a metamorphic facies characterized by relatively low temperatures and high pressures, such as can exist within a subduction zone

    body wave (9) a seismic wave that travels through rock (e.g., a P-wave or an S-wave)

    boulder (6) a sediment clast with a diameter of at least 256 mm

    Bowen reaction series (3) the scheme that defines the typical order of crystallization of minerals from magma

    braided (13) a stream pattern which is characterized by abundant sediment and numerous intertwining channels around bars

    breakwater (17) a structure built offshore in order to deflect the energy of waves

    breccia (6) a sedimentary- or volcanic-rock texture characterized by angular clasts

    brunisol (5) a relatively immature forest soil, lacking in well-defined horizons


    caldera (4) a volcanic depression that is many times larger than the volcanic vents within it

    caliche (5) a white calcium-carbonate rich layer within soils in arid regions

    calving (16) the loss of ice from the front of a glacier by collapse into water

    Canadian Shield (21) the exposed part of the continent Laurentia

    carbonate (2) a mineral in which the anion is CO3-2

    carbonate compensation depth (18) the depth in the ocean (typically around 4000 m) below which carbonate minerals are soluble

    cation (2) a positively charged ion

    cementation (6) the process by which minerals are precipitated between grains in sediments

    Cenozoic (1) the most recent of the eras, representing the past 65.5 Ma of geological time

    chemical sedimentary rock (6) a sedimentary rock comprised of material that was transported as ions in solution

    chernozem (5) a black soil typical of grasslands in cold climates such as the Canadian Prairies

    chert (6) a very fine grained sedimentary rock formed almost entirely of silica

    chlorite (2) a ferromagnesian sheet silicate mineral, typically present as fine crystals and forming from the low-temperature metamorphism of mafic rock

    cinder cone (4) a steep-sided volcano comprised almost entirely of loose rock fragments and typically formed during a single eruptive event

    cirque (16) a steep-sided semi-circular basin eroded by a glacier at the head of its valley

    clast (6) a sedimentary fragment of mineral or rock

    clastic sedimentary rock (6) a sedimentary rock comprised of material that was transported as clasts or fragments

    clay (6) sediment particle that is less than 1/256 mm in diameter

    clay mineral (6) a hydrous sheet silicate mineral that typically exists as clay-sized grains

    claystone (6) a sedimentary rock comprised mostly of clay-sized grains

    cleavage (2) the tendency for a mineral to break along smooth planes that are predetermined by its lattice structure

    climate feedback (19) a process by which the physical effects of a climate forcing can have other effects (either negative or positive) on the climate

    climate forcing (19) a mechanism, such as a change in greenhouse gas levels, that forces the climate to change

    coal-bed methane (20) methane that is trapped within the porosity of coal

    coastal straightening (17) the tendency for an irregular coast to be straightened over time by coastal erosion processes

    cobble (6) sediment particle that is between 64 and 256 mm in diameter

    col (16) the low point or pass along a ridge between two glacial valleys

    columnar jointing (4) the fracturing of rock or sediment (but typically volcanic rock) into columns that are typically 6-sided

    composite volcano (or stratovolcano) (4) a volcano that is constructed of alternating layers of pyroclastic debris and lava flows

    concentrate (mining) (20) a product of ore processing that includes a specific ore mineral, separated from the rest of the rock

    concordant (3) parallel to pre-existing layering or foliation within a rock

    cone of depression (14) the depression of the water table around a well that is heavily pumped

    confined aquifer (14) an aquifer that lies below a confining layer

    confining layer (14) an aquitard that overlies an aquifer and restricts the flow of water down from the surface

    conglomerate (6) a sedimentary rock that is comprised predominantly of rounded grains that are larger than 2 mm

    contact metamorphism (7) metamorphism that takes place adjacent to a source of heat, such as a body of magma

    continental drift (10) the concept that tectonic plates can move across the surface of the Earth

    continental glacier (16) a glacier that covers a significant part of a continent and has an area of at least 50,000 km2

    continental shelf (18) the shallow (typically less than 200 m) and flat sub-marine extension of a continent

    continental slope (18) the steeper part of a continental margin, that slopes down from a continental shelf towards the abyssal plain

    contractionism (10) the now discredited theory that mountain ranges formed as a result of the contraction of the Earth

    convergent boundary (10) a plate boundary at which the two plates are moving towards each other

    Cordilleran Ice Sheet (16) the continental glacier that covered part of western North America, including almost all of British Columbia, part of the Yukon, and part of northern Washington, during the Pleistocene glaciations

    core (1) the metallic interior part of the Earth, extending from a depth of 2900 km to the centre

    core-mantle boundary (9) the boundary, at 2900 km depth, between the mantle and the core

    Coriolis effect (18) the tendency for moving bodies (e.g., ocean currents) to rotate on the surface of the Earth, clockwise in the northern hemisphere and counter-clockwise in the southern hemisphere

    cosmic microwave background (22) radiation left over from the an early stage in the development of the universe at the time when protons and neutrons were recombining to form atoms

    country rock (3) the original rock of a region, into which younger rock (typically igneous) rock has been intruded

    covalent bond (2) a bond between two atoms in which electrons are shared

    crater (4) a volcanic depression that is related to a specific volcanic vent

    craton (21) a region of ancient (typically Precambrian) crystalline rock (equivalent to a shield)

    creep (15) the very slow (mm to cm per year) flow of unconsolidated material on a gentle slope

    crest (17) the highest point on a wave

    crevasse (16) an open fissure on the surface of a glacier

    cross bedding (6) small-scale inclined bedding within larger horizontal beds

    crust (4) the uppermost layer of the Earth, ranging in thickness from about 5 km (in the oceans) to over 50 km (on the continents)

    cyanobacteria (6) photosynthetic bacteria that evolved in the early Archean


    D” layer (9) (d-double-prime layer) a low seismic velocity zone within the basal 200 km of the mantle

    debris flow (15) a gravity-driven flow of water and sediment that includes a significant proportion of coarse (cobble to boulder) material

    decline (20) in mining a decline is a sloped tunnel used to access lower parts of a mine with wheeled equipment

    decompression melting (3) melting (or partial melting) of rock resulting from a reduction in pressure without a significant reduction in temperature

    dendritic (13) a pattern of drainage channels that resembles the branches in a tree

    density (2) weight per volume of a substance (e.g., g/cm3) used widely in the context of minerals or rocks

    deranged (13) a pattern of drainage channels that is chaotic

    detrital (6) referring to fragments of rocks or minerals

    diatom (18) photosynthetic algae that make their tests (shells) from silica

    differentiation (22) the un-mixing of a magma, typically by the physical separation of minerals that crystallize early and settle towards the bottom

    diorite (3) an intermediate intrusive igneous rock

    dip (12) the angle below horizontal at which a sedimentary bed or other feature slopes

    discharge (6) the volume of water flow in a stream expressed in terms of volume per unit time (e.g., m3/s)

    discharge area (14) the part of an aquifer where groundwater discharge takes place

    disconformity (8) a boundary between parallel sedimentary layers where some erosion of the lower layer has taken place

    discordant (3) a geological feature that is not parallel to any existing layering in the country rock

    divalent (2) an ion with a charge or +2 or -2

    divergent (10) a plate boundary at which the two plates are moving towards away from each other

    dodecahedron (2) an object with twelve surfaces, such as a garnet crystal

    dolomite (6) a calcium-magnesium carbonate mineral (Ca,Mg)CO3

    dolomitization (6) the addition of magnesium to limestone during which some or all of the calcium carbonate is converted to dolomite

    dolostone (6) a carbonate rock made up primarily of the mineral dolomite

    drainage basin (13) the catchment area of a stream, including the area where all surface water drains into the stream

    drop stone (16) a fragment of rock within otherwise fine-grained sediment that has been dropped from floating ice on a body of water

    drumlin (16) a streamlined glacial erosional feature comprised of sediments and/or bedrock

    dyke (3) a tabular intrusive igneous body that is discordant to any existing layering in the country rock


    eccentricity (19) in the context of Milankovitch Cycles, the degree to which the Sun is offset from the geometric centre of the Earth’s orbit

    eclogite (7) a garnet-pyroxene-glaucophane bearing rock that is the product of high-pressure metamorphism of oceanic crustal rock, typically within a subduction zone

    effusive (4) a volcanic eruption dominated by the relatively gentle flow of lava

    El Niño (19) a periodic climatic situation in which warm water extends all or most of the way to the eastern edge of the equatorial Pacific

    elastic deformation (11) the deformation of material (including rock) from which it can fully recover if the stress is removed

    electron (2) a sub-atomic particle of essentially no mass and a single negative charge

    end moraine (16) a deposit of sediment that accumulates at the front of a glacier

    englacial (16) within a glacier, referring especially to sediment carried within the glacial ice

    epicentre (11) the location on the surface vertically above the location (i.e., “hypocentre” or “focus”) where an earthquake takes place

    epipelagic zone (18) the upper layer of water (0 to 200 m) in areas of the open ocean

    epithermal deposit (20) a mineral deposit formed near to surface in an area of hydrothermal activity, typically associated with a body of magma

    equilibrium line (16) on a glacier, the line between the zone of accumulation and the zone of ablation (in late summer the equilibrium line is the boundary between snow-covered ice and bare ice)

    equipotential lines (14) in the context of groundwater an equipotential line connects locations with equal hydraulic head or water pressure

    esker (16) a ridge of sediment deposited by a sub-glacial stream

    eustatic sea level change (17) sea level change related to a change in the volume of the oceans, typically because of an increase or decrease in the amount of glacial ice on land

    exfoliation (5) the fracturing of rock that results from a reduction in the pressure when overlying rock is eroded away

    exoplanet (22) a planet that orbits a star other than the Sun

    extrusive (3) igneous rock that cooled at surface


    fall (15) in mass wasting, the vertical or near-vertical fall of rock

    fault (12) a boundary in rock or sediment along which displacement has taken place

    feedback (19) a process by which the physical effects of a climate forcing can have other effects (either negative or positive) on the climate

    feldspar (2) a very common framework silicate mineral

    felsic (3) silica rich (>65% SiO2) in the context of magma or igneous rock

    ferric (2) the oxidized form of an ion of iron (Fe3+)

    ferromagnesian (2) referring to a silicate mineral that contains iron and or magnesium

    ferrous (2) the reduced (non-oxidized) form of an ion of iron (Fe2+)

    fetch (17) the distance over which wind blows to form waves

    finger lake (16) a lake that occupies a glacial valley

    firn (16) the granular transitional state between snow and ice within a glacier

    flood plain (13) the area that is occupied by water when a stream floods and overtops its banks

    flow (15) the fluid-like motion of material during mass-wasting

    flow path (14) the path that groundwater flows along between a recharge area and a discharge area

    flowing artesian well (14) an artesian well in which the water level naturally rises above the surface of the ground

    flux melting (3) melting of rock that is facilitated by the addition of a flux (typically water) which lowers the rocks melting point

    focus (earthquake) (11) the actual point below surface at which an earthquake takes place (equivalent to hypocentre)

    foliated (7) the existence of foliation in a metamorphic rock

    foliation (7) the alignment of mineralogical or structural features of a rock – especially a metamorphic rock

    footwall (12) the lower surface of a non-vertical fault

    foraminifera (18) a single-celled protist with a shell that is typically made of CaCO3

    fore-reef (6) the zone on the ocean side of a reef

    formation (6) a unit of sedimentary rock that is lithologically consistent and sufficiently thick and extensive to be shown on a geological map at the scale that is typically used in the area in question

    fracking (20) fracturing rock by injecting water and chemicals down a well at very high pressure (equivalent to hydraulic fracturing)

    fractional crystallization (3) the sequential crystallization of minerals from magma, and the physical separation of early-forming crystals from the magma in the area where they crystallized

    fracture (2) a break within a body of rock in which the rock on either side is not displaced

    fringing reef (18) a reef adjacent to a shoreline where there is either a very narrow back reef area or none at all (in which case the reef is effectively attached to the shore)

    frost line (22) in the context of planetary systems the boundary beyond which volatile components (e.g., water, carbon dioxide, methane, ammonia etc.) are frozen

    frost wedging (5) the situation where the expansion of freezing water pries rock apart


    Ga (1) (gigaannus) billions of years before the present

    gabbro (3) a mafic intrusive igneous rock

    Gaia hypothesis (19) the hypothesis advanced by James Lovelock that the organisms have affected the atmosphere and oceans such that conditions on Earth have been kept habitable, in spite of significantly changing energy received from the Sun

    galaxy (22) a gravitationally-bound system of stars and interstellar matter

    gas giant (22) a large planet composed mostly of hydrogen and helium (e.g. Jupiter)

    geosyncline (10) a kilometres thick deposit of sediments that has accumulated along the edge of a continent and is sufficient mass to depress the crust beneath it

    geothermal gradient (1) the rate of increase of temperature with depth in the Earth (typically around 30˚ C/km within the crust)

    giant impact hypothesis (22) the theory that the Moon formed when a Mars-sized planet (Theia) collided with the Earth at 4.5 Ga

    glacial period (16) a period of Earth’s history during which glacial ice was present over a sufficient extent to have left recognizable evidence

    glacial groove (16) a straight line created on a rock surface by erosion by a rock fragment embedded in the base of glacial ice (larger and deeper than a glacial striation)

    glacial striation (16) a straight line created on a rock surface by erosion by a rock fragment embedded in the base of glacial ice (finer than a glacial groove – typically less than 1 cm wide)

    glacier (16) a long lasting (centuries or more) body of ice on land that moves under its own weight

    glaciofluvial (16) referring to sediments deposited from a stream that is derived from a glacier

    glaciolacustrine (16) referring to sediments deposited within a lake in a glacial environment

    glaciomarine (16) referring to sediments deposited within the ocean in a glacial environment

    glaucophane (7) a blue-coloured sodium-magnesium bearing amphibole mineral that forms during metamorphism at high pressures and relatively low pressures, typically within a subduction zone

    gneiss (7) high-grade metamorphic rock in which the mineral components are separated into bands

    graben (12) a down-dropped fault block, bounded on either side by normal faults

    grade (7) in the context of a mineral deposit, the amount of a specific metal or mineral expressed as a proportion of the whole rock

    graded bedding (6) an individual sedimentary layer that shows a distinctive gradation in grain size (normal graded bedding is finer towards the top, reverse graded bedding is coarser towards the top)

    gradient (13) the slope of a stream bed over a specific distance, typically expressed in m per km

    granite (1) a felsic intrusive igneous rock

    granule (6) a sedimentary particle ranging in size from 2 to 4 mm in diameter

    greenhouse gas (22) a gaseous molecule with 3 or more atoms that is able to absorb infrared radiation

    greenhouse effect (22) in the context of climate, the ability of an atmosphere to absorb infrared radiation due to the presence of greenhouse gases

    greenschist (7) a foliated metamorphosed rock (typically derived from basalt) in which the green colouration is derived from either chlorite, epidote or green amphibole

    greenstone (7) a non-foliated metamorphosed rock (typically derived from basalt) in which the green colouration is derived from either chlorite, epidote or green amphibole

    greywacke (6) a sandstone with more than 15% silt and clay, and with a significant proportion of sand-sized rock fragments

    groundwater (13) water that lies beneath the surface of the ground

    group (6) a stratigraphically-continuous series of related formations

    groyne (17) a man-made structure extending from the shore built to deflect the energy of waves

    gyre (18) a closed circular ocean current


    habit (2) a characteristic crustal form or combination of forms of a mineral

    habitable zone (22) the region around a star that is considered to be suitable for a life-bearing planet

    Hadean (1) the first eon of Earth history, extending from 4.57 to 3.80 Ga

    halide (2) a mineral in which the anion is one of the halide elements (e.g., halite – NaCl or fluorite – CaF2)

    halite (1) NaCl, a halide mineral also known as table salt

    halogen (2) an element in the second-last column of the periodic table that forms anions with a negative-1 charge

    hanging valley (16) a glacial valley created by a tributary glacier which does not erode as deeply as the main-valley glacier that it joins

    hanging wall (12) the upper surface of a non-vertical fault

    headland (17) a point extending out to sea

    horn (16) a peak that has been eroded on at least three sides by glaciers

    hornfels (7) a fine-grained metamorphic rock that is not foliated

    horst (12) an uplifted fault block, bounded on either side by normal faults

    hot spot (10) the surface area of volcanism and high heat flow above a mantle plume

    hydrated mineral (7) a mineral that includes either hydroxyl (OH) or water (H2O) in its chemical formula (e.g., gypsum CaSO4.2H2O)

    hydraulic conductivity (14) an expression of the rate at which a liquid will flow through a porous medium, as determined by the permeability of the medium and the viscosity of the liquid

    hydraulic fracturing (20) fracturing rock by injecting water and chemicals down a well at very high pressure (equivalent to fracking)

    hydrolysis (5) a reaction between a mineral and water in which H+ ions are added to the mineral and a chemically equivalent amount of cations are released into solution

    hydroxide (2) the anion OH- or an mineral that includes that anion

    hydrothermal alteration (7) chemical alteration of minerals by hot water solutions

    hypocentre (11) the actual point below surface at which an earthquake takes place (equivalent to focus)


    ice giant (22) a planet that is comprised mainly of gases heavier than hydrogen and helium, including oxygen, carbon, nitrogen, and sulfur (e.g., Uranus and Neptune)

    igneous (3) a rock formed from the cooling of magma

    illite (2) a clay mineral with a composition similar to that of muscovite mica

    imbricate (6) aligned and overlapping, like the tiles on a roof

    index fossil (8) a fossil with a distinctive appearance and a wide geographic range but from a relatively restricted time range, thus making it useful for dating a correlating rocks from different regions (the most useful index fossils are from organisms that lived for less than a million years)

    inert (2) in chemistry, an element that does not readily react with other elements (e.g., neon)

    infiltration (14) the recharge of groundwater from the downward percolation of surface water

    insolation (19) a measure of the intensity of solar energy at a specific location or time (expressed in W/m2)

    intensity (11) in seismology, a qualitative measure of the amount of shaking at specific location, based on what was felt by observers, or the amount of damage done

    Intergovernmental Panel on Climate Change (19) (IPCC) an international body established in 1988 by the UN’s World Meteorological Organization and the UN Environment Program to prepare periodic reports on the status of global climate change and its mitigation

    intrusive (3) an igneous rock that has cooled slowly beneath the surface

    ionic bond (2) a bond in which electrons are transferred from one atom to another, thus forming ions

    ion (2) an atom that has either gained or lost electrons and has thus become charged (or a group of atoms that also has a charge – e.g., HCO3-)

    isoclinal fold (12) a tight fold in which the limbs are parallel to each other

    isostasy (9) the equilibrium between a block of crust floating on the underlying plastic mantle

    isostatic sea level change (17) the effect on relative sea level of a vertical adjustment of the crust resulting from a change in the mass of the crust (e.g., from losing or gaining ice)

    isotope (8) an form of an element that differs from other forms because it has a different number of neutrons (e.g., 16O has 8 protons and 8 neutrons while 18O has 8 protons and 10 neutrons)


    joint (12) a fracture in rock

    Jovian planet (22) a gas giant


    ka (1) (kiloannus) thousands of years before the present

    kaolinite (2) a clay mineral that does not have cations other than Al and Si

    karst (14) the solutional erosion of an area with soluble rock (typically limestone) to form depressions and caves

    kettle (16) a depression formed at the front of a large glacier when a stranded ice block that was surrounded by sediment eventually melts

    kettle lake (16) a lake that forms within a kettle

    kimberlite (4) an ultramafic volcanic rock that originates at significant depth (> 200 m) in the mantle (some kimberlites include diamonds)

    Kuiper belt (22) a region of the Solar System beyond the orbit of Neptune that is populated by small objects and dwarf planets (including Pluto)


    laccolith (3) concordant intrusion in which the central part has formed an upward dome

    lahar (4) a mudflow or debris flow that is either caused by a volcanic eruption, or forms on the flank of a volcano as a result of flooding not related to an eruption

    landfill gas (14) gases produced within a landfill during the microbial breakdown of landfill components (most are dominated by carbon dioxide and methane)

    large igneous province (4) a very large area of mafic volcanic rock produced by a massive eruption typically related to a mantle plume

    lateral moraine (16) a deposit of rocky material that forms along the margin of a valley or alpine glacier, mostly from the freeze-thaw release of material from the steep slopes above

    lattice (1) the regular and repeating three-dimensional structure of a mineral

    Laurentide Ice Sheet (16) the continental glacier that extended across central eastern North America during the Pleistocene, covering most of Canada and a significant part of the United States

    lava levée (4) a ridge that forms along the edge of a lava flow because the magma at the edge cools faster than that in the middle

    lava tube (4) a tube that forms as mafic lava flows along a channel and lava leveés build up on either side, eventually forming a roof (once a lava tube forms it insulates the flowing magma, allowing it to stay hot a liquid for longer and therefore flow much further)

    leachate (14) in the context of landfills, the liquid (rainwater) that passes through the waste and becomes contaminated with soluble components from the waste

    levée (13) on a stream, the ridge that naturally forms along the edge of the channel during flood events

    level (20) in mining, a horizontal mine opening

    light year (22) the distance that light can travel in one year (9.4607 x 1012 km)

    lignite (20) a low-grade type of coal with less than 70% carbon

    limbs (12) the layers of rock on either side of a fold

    limestone (6) a sedimentary rock that is comprised mostly of calcite

    liquefaction (11) the tendency for unconsolidated and water saturated sediments to lose strength during seismic shaking

    lithic arenite (6) an arenite in which there is more than 10% lithic clasts and in which there are more lithic clasts than feldspar clasts

    lithic clasts (6) fragments of rock (e.g., basalt) that are included in the sand-sized grains in sandstone, or in the larger grains in conglomerate

    lithification (6) the conversion of unconsolidated sediments into rock by compaction and cementation

    lithosphere (1) the rigid outer part of the Earth, including the crust and the mantle down to a depth of about 100 km

    lodgement till (16) sediment that accumulates at the base of a glacier and typically has a wide range of grain sizes (including clay) and is well compacted

    longshore current (17) the movement of water along a shoreline produced by the approach of waves at an angle to the shore

    longshore drift (17) the movement of sediment along a shoreline resulting from a longshore current and also from the swash and backwash on a beach face

    Love wave (11) a surface seismic wave, with horizontal motion, that develops in relatively weak (e.g., unconsolidated) materials at surface

    luvisol (5) a cold climate forest soil formed in which clay has been removed from the A horizon and relocated into the B horizon


    Ma (1) (Megaannus) millions of years before the present

    mafic (3) silica poor (<45% SiO2) in the context of magma or igneous rock

    magma (1) molten rock typically dominated by silica

    magnetic chronology (8) the study of the timing of reversals of the Earth’s magnetic field, and the application of that understanding to dating geological materials

    magnitude (11) a measure of the amount of energy released by an earthquake

    mantle (1) the middle layer of the Earth, dominated by iron and magnesium rich silicate minerals and extending for about 2900 km from the base of the crust to the top of the core

    mantle plume (3) a plume of hot rock (not magma) that rises through the mantle (either from the base or from part way up) and reaches the surface where it spreads out and also leads to hot-spot volcanism

    marble (7) metamorphosed limestone (or dolostone) in which the calcite or dolomite has been recrystallized into larger crystals

    mass wasting (15) the mass failure, by gravity, of rock or unconsolidated material on a slope

    meander cutoff (13) the formation of a shorter stream channel across the narrow boundary between two meanders on a stream

    meandering (13) the sinuous path taken by a stream within a wide flat flood plain

    medial moraine (16) a lateral moraine that has been shifted towards the centre of a valley glacier at a point where two glaciers meet

    member (6) a subdivision of a formation

    mesopelagic zone (18) the upper middle zone of the open ocean extending from 200 to 1000 m depth

    metallic lustre (2) the lustre of a mineral into which light does not penetrate but only reflects off of the surface

    metallic bond (2) a type of bond in which abundant electrons are easily shared amongst cations

    metamorphism (3) the transformation of a parent rock into a new rock as a result of heat and pressure that leads to the formation of new minerals, or recrystallization of existing minerals, without melting

    metasomatism (7) metamorphism facilitated by ion transfer through water

    meteoroid (22) a fragment of either stony or metallic debris in space

    methane hydrate (18) a combination of water ice and methane in which the methane is trapped inside “cages” in the ice

    mica (2) a sheet silicate mineral (e.g., biotite)

    migmatite (7) a rock that is a mixture of metamorphic and igneous rock, formed at very high grades of metamorphism when a part of the parent rock starts to melt

    Milankovitch cycles (19) millennial-scale variations in the orbital and rotational parameters of the Earth that have subtle effects on the Earth’s climate

    Mohorovičić discontinuity (9) the boundary between the crust and the mantle

    moment magnitude (11) a way of estimating earthquake magnitude based on the area of the rupture surface and the amount of displacement

    monogenetic (4) a volcano that forms in a single eruptive event

    moraine lake (16) a finger lake that forms within a glacial valley and is dammed by an end moraine

    mud crack (6) a dessication crack formed in mud that has accumulated in a small body of water that later dries up or drains

    mudflow (15) a mass-wasting event involving the flow of mud (sand, silt and clay) within a channel

    mudrock (6) an inclusive term for mudstone, shale and claystone

    muscovite (2) a potassium-bearing non-ferromagnesian mica


    native element (2) (also native element mineral) a mineral that consists of only one element (e.g., native gold)

    nebula (22) a cloud of interstellar dust and gases

    negative feedback (19) a process that results in a decrease in that process (in the context of climate change it is a process that reduces the change in climate, such as the enhanced growth of vegetation in response to an increase in atmospheric carbon dioxide)

    neutron (2) a sub-atomic particle with a mass of 1 and a charge of 0

    nonconformity (8) a geological boundary where non-sedimentary rock is overlain by sedimentary rock

    non-ferromagnesian mineral (2) a silicate mineral that does not contain iron or magnesium (e.g., feldsspar)

    non-metallic lustre (2) the lustre of a mineral into which light does penetrate

    normal fault (12) a non-vertical fault along which the hanging wall (upper surface) has moved down relative to the footwall

    normal force (15) the component of the gravitational force that acts directly into the slope

    North Atlantic Deep Water (18) deep Atlantic Ocean water that has descended in the far north of the basin in the area between Scandinavia and Greenland

    nunatuk (16) a rocky peak that extends above the ice level of a continental glacier


    obliquity (19) in the context of Milankovitch Cycles, the angle of the tilt of the Earth’s rotational axis with respect to the plane of its orbit around the Sun

    ocean plain (18) the extremely flat surface of the deep ocean floor in areas unaffected by plate tectonic processes and volcanism

    oil window (20) the depth range, which is approximately 2000 to 4000 m, within which the temperature is appropriate for the formation of oil from organic matter in sedimentary rock

    ooid (6) a small (approximately 1 mm) sphere of calcite formed in areas of tropical shallow marine water with strong currents

    olivine (2) a silicate mineral made up of isolated silica tetrahedra and with either iron or magnesium (or both) as the cations

    Oort cloud (22) a spherical cloud of icy objects extending from between about 5,000 and 500,000 astronomical units (Sun-Earth distances) from the Sun (thought to be the source area of comets)

    open-pit mine (20) a mine that is open to the surface

    outcrop (5) a surface exposure of rock that is part of the crust (bedrock)

    outwash plain (16) an extensive region of sand and gravel deposited by streams flowing out of a glacier (same as sandur)

    overturned (12) a geological feature that has been tilted to the point where it is upside down

    oxbow (13) a part of a stream meander that has become isolated from the rest of the stream as the result of a meander cutoff

    oxidation (5) the reaction between a mineral and oxygen

    oxide (2) a mineral in which the anion is oxygen (e.g., hematite Fe2O3)


    pahoehoe (4) a lava flow with a ropy surface texture formed when the surface cools and hardens while the lava beneath is still flowing

    paleomagnetic (10) past variations in the intensity and polarity of the Earth’s magnetic field

    Pangea (10) the supercontinent that existed between approximately 300 and 180 Ma

    paraconformity (8) an interruption representing a period of non-deposition, without tilting or erosion, in a sequence of sedimentary rocks

    parasitic fold (12) a fold within a fold

    parent rock (7) the rock that was already in existence when a process of metamorphism started

    partial melting (3) the process during which a only specific mineral components of a rock melt in response to changing conditions

    parting (6) a narrow gap between individual sedimentary layers

    passive margin (10) a boundary between a continent and an ocean at which there is no tectonic activity (e.g., the eastern edge of North America)

    paternoster lake (16) one of a series of rock basin lakes

    pebble (6) a sedimentary particle ranging in size from 2 to 64 mm (includes granule)

    pelagic (18) the part of a lake or the ocean that is not close to shore

    permafrost (19) ground that remains frozen for two or more years

    permanentism (10) the now discredited theory that the features on the Earth have not changed significantly over geological time

    permeability (14) an expression of the ease with which liquid will flow through a porous medium

    phaneritic (3) a rock texture in which the individual crystals or grains are visible to the naked eye

    Phanerozoic (1) the most resent eon of geological time, encompassing the Paleozoic, Mesozoic and Cenozoic eras

    phenocryst (3) a relatively large crystal within an igneous rock

    phyllosilicate (2) a silicate mineral in which the silica tetrahedra are made up of sheets

    phosphate (2) a mineral in which the anion is PO43-

    photic zone (18) the upper 200 m of the ocean or a lake, where, depending on the turbidity of the water, light can penetrate

    phreatic eruption (4) a steam-drive volcanic eruption that takes place when surface or near-surface water is heated by volcanic activity

    phyllite (7) a metamorphic rock with slaty cleavage and a sheen on the surface produced by aligned micas

    pillow (4) a pillow-shaped mass of volcanic rock (typically basalt) formed when magma erupts beneath the surface

    pillow lava (4) a volcanic rock (typically basalt) that is made up primarily of pillows

    pipe (3) a cylindrical body of igneous rock, typically resulting from a feeder conduit to a volcano

    plate (1) a region of the lithosphere that is considered to be moving across the surface of the Earth as a single unit

    plate tectonics (1) the concept that the Earth’s crust and upper mantle (lithosphere) is divided into a number of plates that move independently on the surface and interact with each other at their boundaries

    plinian eruption (4) a large volcanic eruption in which a column of hot tephra and gases rises many kilometres into the atmosphere

    pluton (3) a body of intrusive igneous rock

    podsol (5) a soil with well-developed horizons formed in temperate forested regions

    podsolization (5) the process of the formation of podsol

    polar wandering path (10) a path of varying magnetic pole positions defined by paleomagnetic data (in fact it is now understood that the continents have wandered, not the poles, so a more appropriate terms is “apparent polar wandering path”)

    polymerize (3) the formation of molecular chains within a fluid (e.g., a magma) that lead to an increase in the fluid’s viscosity

    polymorphs (7) two or more minerals with the same chemical formula but different crystal structures

    porosity (14) the percentage of open pore space within a body of rock or sediment

    porphyritic (3) an igneous texture in which some of the crystals are distinctively larger than the rest

    porphyry deposit (20) a mineral deposit (of copper or molybdenum especially) in which part of the host rock is a porphyritic stock

    positive feedback (19) a process that results in an increase in that process (in the context of climate change it is a process that enhances the change in climate, such as the reduced reflectivity of the Earth’s surface when ice melts)

    potassium feldspar (2) feldspar with the formula KAlSi3O8

    potentiometric surface (14) the imaginary surface defined by the levels to which water would rise in a series of wells drilled into a confined aquifer

    precession (19) in the context of Milankovitch Cycles, the variation in the direction at which the Earth’s rotational axis is pointing

    principle of cross-cutting relationships (6) the principle that a body of rock that cuts across or through another body of rock is younger than that other body

    principle of faunal succession (6) the principle that life on Earth has evolved in an orderly way, and that we can expect to always find fossils of a specific type in rocks of a specific age

    principle of inclusions (6) the principle that inclusions within a body of rock must be older than the rock

    principle of original horizontality (6) the principle that sedimentary beds are originally deposited in horizontal layers

    principle of superposition (6) the principle that in a sequence of layered rocks that is not overturned or interrupted by faulting, the oldest will be at the bottom and the youngest at the top

    proglacial (16) referring to the area in front of a glacier

    proton (2) a sub-atomic particle with a mass of 1 and a charge of 1

    protoplanetary disk (22) a rotating cloud of gas and dust surrounding a young star

    pumice (4) a highly vesicular felsic volcanic rock (typically composed mostly of glass)

    p-wave (9) a seismic body wave that is characterized by deformation of the rock in the same direction that the wave is propagating (compressional vibration)

    pyroclastic (4) volcanic material formed during an explosive eruption

    pyroclastic density current (4) a body of hot pyroclastic rock and gases that is flowing rapidly down the flank of a volcano

    pyroxene (2) a single chain silicate mineral


    quartz (2) a silicate mineral with the formula SiO2

    quartz sandstone (6) a sandstone in which more than 90% of the grains are quartz

    quartzite (7) a metamorphic rock formed from the contact or regional metamorphism of sandstone


    radial (13) a pattern of streams radiating out from a central point, typically an isolated mountain

    radioactivity (9) the natural transformation of unstable isotopes into new elements

    radiolaria (18) microscopic (0.1 to 0.2 mm) marine protozoa that produce silica shells

    Rayleigh wave (11) a surface seismic wave, with vertical motion

    recharge (14) the transfer of surface water into the ground to become groundwater

    recharge area (14) an area of an aquifer where recharge is predominant over discharge

    rectangular drainage (13) a drainage pattern in which tributaries typically flow at right angles to each other and meet at right angles

    recumbent fold (12) a fold that is overturned such that its limbs are close to horizontal

    redshift (22) the increase in wavelength of light resulting from the fact that the source of the light is moving away from the observer

    reef (17) a mound of carbonate formed in shallow tropical marine environments by corals, algae and a wide range of other organisms

    regional metamorphism (7) metamorphism caused by burial of the parent rock to depths greater than 5 km (typically takes place beneath mountain ranges, and extends over areas of hundreds of km2)

    remnant magnetism (10) magnetism of a body of rock that formed at the time the rock formed and is consistent with the magnetic field orientation that existed at that time and place

    reservoir rock (20) rock into which petroleum has migrated and is now trapped

    residual soil (5) soil formed by weathering of the underlying rock or sediment

    retrograde metamorphism (7) metamorphism that takes place at a lower temperature than that at which the rock originally formed or was previously metamorphosed

    reverse fault (12) a non-vertical fault along which the hanging wall (upper surface) has moved up relative to the footwall

    rhyolite (3) a felsic volcanic rock

    ridge push (10) the concept that at least part of the mechanism of plate motion is the push of oceanic lithosphere down from a ridge area

    rip current (17) a strong flow of water outward from a beach

    ripple (6) on a series of small parallel ridges formed within sediment that has accumulated in moving water or wind

    rip-rap (17) angular rock fragments, typically boulder sized, used to armour slopes and shorelines against erosion

    roche moutonée (16) a product of glaciation in which a bedrock protrusion is eroded into a streamlined shape that has a broken or jagged leading (down-ice) edge

    rock avalanche (15) a rapid turbulent flow of broken bedrock fragments down a steep slope

    rock basin lake (16) a lake situated in a rock basin carved at the upper end of an alpine glacier

    rock cycle (3) the series of processes through which rocks are transformed from one type to another

    rock fall (15) the near-vertical fall or bouncing of rock released from a steep slope

    rock slide (15) the translational motion of an essentially intact body of rock down a slope (rock slides are typically slow, because once they start to move fast the rock body becomes fragmented and then flows as a rock avalanche)

    runoff (14) flow of water down a slope, either across the ground surface, or within a series of channels

    rupture (11) breaking of rock subject to stress, typically resulting in an earthquake

    rupture surface (11) the area over which rock rupture takes place during an earthquake


    sackung (15) an escarpment or trough at the top of a slow-moving rock slide (sackungen)

    salatation (13) the bouncing of particles along a stream bottom or desert floor

    sand (6) a mineral or rock fragment ranging in size from 1/16th to 2 mm

    sandstone (1) a rock that is primarily comprised of sand-sized particles

    sandur (16) an extensive region of sand and gravel deposited by streams flowing out of a glacier (same as outwash plain)

    saturated zone (14) the part of an aquifer, or any body of rock, that is saturated with water

    schist (1) a metamorphic rock with visible aligned mica crystals

    sea cave (17) a shallow cave formed on a rocky shore by wave erosion

    sea cliff (17) a coastal escarpment that is typically eroding inland as a result of wave action

    sea-floor spreading (10) the formation of new oceanic crust by volcanism at a divergent plate boundary

    sector collapse (4) the sudden collapse of a significant part of the flank of a volcano

    sedimentary rock (3) rock that has formed by the lithification of sediments

    sediments (3) unconsolidated particles of mineral or rock

    seismic (11) pertaining to earthquakes

    seismic moment (11) a measurement of an earthquake’s energy based on longwave vibrations, or on the product of the fault area and displacement

    seismic reflection sounding (10) measurement of the properties of sediments based on detection of sounds generated at surface and reflected from layers beneath the surface

    septae (8) calcareous partitions between the successive living chambers in a cephalopod

    septic system (14) a system constructed to facilitate the dispersion and detoxification of sewage (typically includes a septic tank and a drainage field)

    shaft (20) a vertical opening at a mine

    shale (6) a silt- and clay-rich rock that has evidence of layering

    shear force (15) the component of the gravitational force in the direction parallel to a slope

    shear strength (15) the strength of a body of rock or sediment that counteracts the shear force

    shear stress (12) the stress placed on a body of rock or sediment adjacent to a fault

    sheeted dykes (10) a series of near-vertical dykes formed in the vicinity of a spreading ridge when magma from depth flows into fractures formed by extensional forces

    sheet silicate (2) a silicate mineral in which the silica tetrahedra are combined within sheets

    sheetwash (5) overland flow of water, typically related to a heavy precipitation event

    shield (4) a region of ancient (typically Precambrian) crystalline rock (equivalent to a craton)

    shield volcano (4) a low-profile volcano formed primarily from eruptions of low-viscosity mafic magma

    SIAL (sialic) (10) referring to rock or magma in which silica and aluminum are the predominant components (generally equivalent to felsic)

    silica (2) a form of the mineral quartz (SiO2)

    silica tetrahedron (2) a combination of 1 silicon atom and 4 oxygen atoms that form a tetrahedron

    silicate (1) a mineral that includes silica tetrahedra

    silicon (2) the 14th element

    silicone (2) resin or caulking made from silicon-oxygen chains and various organic molecules

    sill (3) an igneous intrusion that is parallel to existing layering in the country rock

    silt (6) sedimentary particles ranging is size from 1/256th to 1/16th of a mm

    SIMA (simatic) (10) referring to rock or magma in which silica, magnesium and iron are the predominant components (generally equivalent to mafic)

    skarn (7) the contact metamorphism (and metasomatism) of limestone

    slab pull (10) the concept that at least part of the mechanism of plate motion is the pull of oceanic lithosphere down into the mantle

    slate (7) a fine-grained metamorphic rock that splits easily into sheets

    slaty cleavage (7) the tendency for slate or phyllite to split into sheets (note that this is the only situation in this textbook where the term “cleavage” is applied to a rock as opposed to a mineral)

    slide (15) the downward movement of rock or sediment on a slope as an intact mass

    slump (15) a slide in which the nature of the motion is rotational (typically only develops in unconsolidated sediments)

    smectite (2) a fine-grained sheet silicate mineral that can accept water molecules into interlayer spaces, resulting is swelling

    smelter (20) a refinery at which minerals are processed to produce pure metals

    snowline (22) in astronomy the radius around a star at which represents the boundary between gases (or liquids) and solids

    soil horizon (5) a layer, within a well-developed soil, that is physically or chemically different from layers above or below

    solar system (22) a star and the planets surrounding it

    solar wind (22) a stream of ionized (charged) particles away from the Sun

    solid solution (2) the substitution of one element for another in a mineral (e.g., iron can be substituted for magnesium in the mineral olivine)

    solifluction (15) the flow of water saturated sediment or soil over a stronger and less permeable substrate

    source rock (20) the sedimentary rock from which petroleum originates prior to its migration into a reservoir rock

    speleothem (6) a solutionally-formed feature within a limestone cave (e.g., a stalactite)

    spit (17) a sand or coarser deposit extending from shore out into open water

    spring (14) the flow of groundwater onto the surface

    stack (17) a prominent rocky island that is a remnant of the erosion of a headland

    stage (13) the level of water in a stream

    stalactite (6) a cone-shaped speleothem that is suspended from the roof of a cave

    stalagmite (6) a cone-shaped speleothem that forms on the floor of a cave

    step-pool (13) a characteristic of stream flow in which water flows from one pool to another, typically on a stream with a steep gradient

    stock (3) an irregular pluton with n exposed area less than 100 km2

    stoping (3) the fracturing and incorporation of fragments of country rock as a magma body moves upward through the crust

    strain (12) the deformation of rock that is subjected to stress

    streak (2) the mark left on a porcelain plate when a mineral sample is ground to a powder by being rubbed across the plate (typically considered to provide a more reliable depiction of the colour than the whole sample)

    stream (13) any body of flowing water

    stress (12) a force applied to a rock

    stress transfer (11) the change in the pattern of stress on a region of rock as a result of an earthquake (typically stress is reduced in the area of a rupture zone, but is increased elsewhere in the vicinity)

    strike (12) the compass direction of a horizontal line on a sloped surface (e.g., bedding plane, fracture etc.)

    strike-slip fault (12) a fault that is characterized by motion that is close to horizontal and parallel to the strike direction of the fault

    subaerial eruption (4) a volcanic eruption that takes place on land

    subaqueous eruption (4) a volcanic eruption that takes place under water

    subducted (1) when part of a plate is forced beneath another plate along a subduction zone

    subduction zone (10) the sloping region along which a tectonic plate descends into the mantle beneath another plate

    subglacial (16) beneath a glacier

    sulphate (2) a mineral in which the anion is SO42-

    sulphide (2) a mineral in which the anion is S2-

    supergroup (21) a stratigraphically-continuous series of related groups

    superterrane (21) a number of terranes that are contiguous

    supraglacial (16) on the surface of a glacier

    surf zone (17) the near-shore zone where waves are breaking into surf

    suture (8) the line on the surface of a cephalopod that marks the boundary between a septum and the outer shell

    swash (17) the upward motion of a wave on a beach (typically takes place at the same angle that the waves are approaching the shore)

    s-wave (9) a seismic body wave that is characterized by deformation of the rock transverse to the direction that the wave is propagating

    symmetrical (12) a fold in which the limbs are at the same angle to the hinge

    syncline (12) a downward fold where the beds are known not to be overturned

    synform (12) a downward fold where it is not known if the beds are overturned


    tailings (20) the fine-grained waste rock from a plant used to concentrate ore minerals

    talus slope (15) a sloped deposit of angular rock fragments at the base of a rocky escarpment

    tarn (16) a lake within a rock basin

    tectonic plate (1) a region of the lithosphere that is considered to be moving across the surface of the Earth as a single unit

    tectonic sea level change (17) relative sea level change related to the vertical motion of a crustal block caused by tectonic processes

    tephra (4) fragments of volcanic rock (including volcanic ash) ejected during an explosive eruption

    terminal moraine (16) and end moraine that marks the farthest forward advance of a glacier

    terrane (7) a block of crust that has geological features that are distinctive from neighbouring regions, and is assumed to have been moved from elsewhere by tectonic processes

    terrestrial planet (22) a planet with a rocky mantle and crust and metallic core (e.g., Earth)

    terrigenous (18) referring to sedimentary particles that originated on a continent

    test (6) the shell-like hard parts (either silica or carbonate) of small organisms such as radiolarian and foraminifera

    thrust fault (11) a low angle reverse fault

    till (16) unsorted sediment transported and deposited by glacial ice

    tiltmeter (4) a sensitive instrument used to monitor subtle changes in the tilt of the land, particularly in studies of active volcanoes

    tombolo (17) a sand or coarser deposit connecting an island or rocky prominence to a larger body of land

    traction (13) a force that contributes to the movement of particles situated on a stream bed or desert floor

    transform fault (10) a boundary between two plates that are moving horizontally with respect to each other

    travertine (6) a deposit of calcium carbonate that forms at springs, hot springs or within limestone caves

    trellis (13) a drainage pattern in which tributaries typically flow parallel to one other but meet at right angles

    trigger (15) an event, such as an earthquake or a heavy rainfall, that triggers the onset of a mass wasting event

    trough (17) the lowest point of a wave

    truncated spur (16) the steep end of a ridge or arête that has been eroded by a main-valley glacier

    tsunami (11) a long-wavelength wave produced by the vertical motion of the floor of the ocean or a large lake, typically related either to an earthquake or a sub-marine mass wasting event

    tufa (6) a form of travertine that is especially porous as it forms around existing vegetative material.

    tuya (4) a flat-topped volcanic hill or mountain that formed when an eruption took place beneath a glacier and the melting led to the formation of a lake that then resulted in the wave-erosion of the top of the volcano


    unconfined aquifer (14) an aquifer that is not overlain by a confining layer

    unconformity (8) a geological boundary at the base of a sedimentary layer

    unconformity-type uranium deposit (20) a uranium deposit that has formed at a nonconformity between sandstone and older rock

    uncompressed density (22) the density of planetary material that it would have it was not compressed by the planets gravitational force

    underground storage tank (14) (UST) an underground tank for storing liquids, most commonly for liquid fuel

    unsaturated zone (14) the rock or sediment above the water table

    U-shaped valley (16) a relatively straight valley with a flat bottom and steep sides that has been carved by a valley glacier


    valley glacier (16) a glacier formed in a mountainous region and confined to a valley (same as alpine glacier)

    varve (16) a recognizable layer within sediments that represents a single year of deposition

    vesicular (3) an igneous texture characterized by holes left by gas bubbles

    volcanic glass (2) magma that has cooled within minutes, not allowing time for the formation of crystals

    volcanic-hosted massive sulphide (20) a mineral deposit hosted by volcanic rocks and including zones where most of the rock is made up of sulphide minerals (including ore minerals and pyrite)


    wacke (6) a sandstone with more than 15% clay and silt

    water table (14) the upper surface of the saturated zone in an unconfined aquifer

    wave base (17) the depth of water that is affected by the sub-surface orbital motion of wave action (approximately one-half of the wavelength)

    wave-cut platform (17) a nearly-horizontal bench of rock eroded by waves within the surf zone (equivalent to wave-cut terrace)

    wavelength (17) the distance between the crests of two waves

    weathering (5) a range of processes taking place in the surface environment, through which solid rock is transformed into sediment and ions in solution

    Western Canada Sedimentary Basin (21) a large basin in the western interior of Canada, east of the Rocky Mountains, extending from the northern United States to the Northwest Territories

    Wisconsin Glaciation (16) the most recent advance of the Pleistocene glaciations, extending from 85 to 11 ka


    xenolith (3) a fragment of country incorporated into igneous rock, commonly as a result of stoping


    youthful stream (13) a stream that is actively down-cutting its valley in an area that has recently been uplifted


    zone of ablation (16) the part of a glacier, below the equilibrium line, where there is net loss of ice mass due to melting and calving

    zone of accumulation (16) the part of a glacier, above the equilibrium line, where there is net gain of ice mass because not all of the snow that falls each winter is able to melt during the following summer