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Geology LibreTexts

Glossary

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

A

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

B

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

C

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

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

E

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

F

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

G

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

H

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)

 

I

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)

J

joint (12) a fracture in rock

Jovian planet (22) a gas giant

K

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)

L

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

M

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

N

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

O

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)

P

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

Q

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

R

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

S

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

T

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

U

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

V

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)

W

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

X

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

Y

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

Z

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

Contributors