The loss of ice from a glacier or ice sheet by melting.

Absolute age dating

Age dating of rocks and sediments by means of radiometric methods


The space available to be filled by sediment, between sea-level and a basin floor. See Sites: C69

Accreted terrane

An extensive block of crust that was formerly a landmass or a piece of the ocean floor, that collided with, and adhered to another during an orogeny. For example, the Grenville province of Ontario is composed of many different terranes arising from the Grenville orogeny between 1. 3 and 1 billion years ago. Much of Canada's western Cordillera is likewise composed of far travelled terranes containing oceanic crust (see also ophiolite).


Refers to the collision of crustal blocks and the generation of a larger continent. See Sites: N109

Active margin

Leading edge of a lithospheric plate where it collides with another plate. Same as convergent margin.

Aeromagnetic survey

An airborne magnetic geophysical survey designed to identify burie.g.ological structures such as faults using a magnetometer.


Very coarse grained rock composed of angular fragments (see breccia) formed by volcanic processes typical violent eruptions of andesitic volcanoes.


General term for sand and gravel used in construction of roads, buildings etc. See Sites: C41


In a geological sense it refers to crustal elements (terranes) brought in from elsewhere and added to a continent. Contrast with autochthonous.


A metamorphic rock consisting of mainly amphibole and feldspar. See Sites: C107, S143


Fine-grained igneous rock that is intermediate in composition. See Sites: C19

Andesitic volcano

Volcanoes above subduction zones and characterised by explosive eruptions that produce huge volumes of tephra and debris and pyroclastic flows.


A crystal that shows no clear crystal form.


Negatively charged ion. See Sites: C92


Coarse-grained igneous intrusive rock related to gabbro but rich in pale coloured feldspar minerals (Also known as Moon rock). See Sites: C5, S133


Lacking oxygen. See Sites: S23


A fold that is upward convex. See Sites: E41


A sand dune that is migrating upstream in a flooding river. They are rarely preserved in the rock record.

Aphanitic texture

When individual mineral crystals in an igneous rock are too small to be seen by the eye. The result of rapid cooling of the parent magma which prevents growth of larger crystals (contrast with phaneritic).


A layer of permeable rock or sediment below the Earth's surface which groundwater moves through. See Sites: W36


A layer of impermeable sediment or rock which can confine (seal) an aquifer.


Refers to updomed portions of the Canadian shield. These are long lived and have influenced sedimentation during the last 600 million years, often controlling the shorelines of large seas that have flooded the shield. See Sites: C6, C59, C125, E13, E17, E18, E48, N16, N29, N38, N53, N81, N87, N88, N103, S72, S87, S108, S121, S129, S130, S137, W33, W46, S101


The division of geologic time (called an eon) between 4-2. 5 billion years ago or rocks belonging to that time period (eonothem). See Sites: N16, N29, N53, N81, N87


Large landmass that included an early North American continent (called by some Kenorland) that had formed by about 2. 7 ga.See Sites: N44


Low-grade Metasedimentary rock composed mainly of shale or slate


A sedimentary rock that is rich in quartz and feldspar, formed through the weathering of feldspar rich igneous or metamorphic rock.

Artesian water

Groundwater within a confined aquifer which is under enough pressure to rise above the surface when drilled into.

Artesian well

A well where water rises under pressure above the ground surface. Associated with confined aquifers.


Slabs of rock used for building stone.


The incorporation of surrounding country rock into an igneous magma (se.x.nolith).


A relatively soft, plastic layer of the Earth lying below the lithosphere, about 60-300 kilometres below the surface.


Refers to the gaseous sphere that surrounds planet Earth. See Sites: N52


A circular halo-like reef that typically grows around extinct volcanoes that eventually become completely submerged to become seamounts or guyots.


The smallest unit of an element, composed of Neutrons, electrons and protons.

Atomic mass

The total number of protons and neutrons in the nucleus of the element.

Atomic number

The number of protons in the nucleus of an element.


To be diluted e.g. Where contaminants are diluted by movement through wet sediment.


Refers to an eye-like inclusion of minerals in gneiss.


A narrow ancient rift (graben) formed when a continent broke up and now filled an buried. They extend into the interior of modern continents and usually are marked by large rivers (e.g., Ottawa graben).


Formed in situ.


The centre line of a fold i.e. Along the crest of an anticline or along the trough of a syncline. See Sites: C92, C137, E70, E72, C138, C140, C141

B horizon

The layer within a soil profile lying below the A horizon.


Obsolete term (used in the 1950s) to refer to limestone sediment formed i.e.vironments similar to the modern Bahamas platform.

Banded iron formation

Rocks (usually older than 750 million years) made up of alternating layers of Silvery Magnetite and red Hematite (see bif). See Sites: N52, N81, N109, N111, N116

Banded iron formation (bif)

Rocks with distinct banded reddish layers signifying the constituent iron rich materials like Magnetite and Hematite.


A physiographic barrier occurring between the open sea and a protected lagoon or inland sea. Formed by accumulation of wave-formed sand beaches or by the growth of organic reefs in shallow water. See Sites: C14, C86, N67


A fine-grained, mafic igneous rock lacking in silica. Flows readily and is produced by non-explosive volcanoes at mid-ocean ridges and hot spots. See Sites: E8, N15, N18, N57, N81, N103, N107, N109


A term for magma of mafic composition. See Sites: E8


The water contribution to streams from groundwater springs. Usually measured in summer when surface runoff from rainfall is at a minimum.

Basement complex

Igneous and metamorphic rocks which underlay stratified rocks of a region.


An area of the Earth's crust that is depressed and usually covered by water and which is receiving sediments. See Sites: C15, C60, C131, N17, N18, N28, N31, N41, N44, N56, N69, N98, N102, N113, S5, S35, S36, S103, W1, W10, E63, E64, E65, S142


Very large igneous intrusion of regional extent, which cooled at depth giving rise to a coarse grained rock such as granite (see also pluton).


The oldest innermost part of a continent composed of archean and Proterozoic rocks. The North American craton is the largest in the world.


The process of building continents by accretion. Sometimes used specifically to refer to formation of the earliest continental landmasses now preserved as cratons.


The very slow movement of rock or soil downslope under the effect of gravity. See Sites: W17, W21, W24, W28


Sedimentary structures in sand deposited by currents of water. The term 'cross' refers to the fact that they are not horizontal but have a gentle dip. See Sites: S57

Crustal rebound

Increase i.e.evation of crust when freed from weight of large ice sheet (see also glacial rebound and glacioisostatic).


A homogeneous solid with an orderly internal atomic structure. See Sites: C21, C37, C61, C62, C106, C110, C112, C119, C120, C136, N37, S65, W31, S141, S144, S146

Crystal form

The external geometric shape of a perfectly formed crystal.

Crystal settling

The process whereby the minerals that crystallize at high temperature settle out of the magma due to higher density then the magma.

Crystalline structure

Atoms are arranged in an orderly repeating structure.


The development and growth of crystals during cooling of magma or during evaporation of salt water (see evaporite). See Sites: S141


Simple prokaryotic bacteria capable of photosynthesis first found about 3. 5 billion years ago. See Sites: E22


A succession of sedimentary facies that is repeated several or many times within a formation or sequence See Sites: N71, S114


A particular type of coal-bearing cycle first defined in the Upper Paleozoic succession of the US Midcontinent


An volcanic igneous rock that is very simular to rhyolite, it is intermediate in composition containing quartz and plagioclase feldspar.

Dansgaard-oeschger cycles

Short episodes of abrupt climate cooling and warming recorded in ocean sediments deposited during the last ice age.

Daughter atom

The product of radioactive decay of an unstable isotope


Chaotic mixture of sediment or rock formed by the collapse of a cliff or from a glacier or volcano. See Sites: C31, C48, C110, C137, C131, E46, N28, N31, N40, N93, S9, S95, S135, E69, C138, C140, C141, C143, C144

Debris fall

Free-falling mass of debris usually from a cliff.

Debris flow

The rapid movement of water-saturated debris downslope as a fluid. See Sites: N93


Refers to angular difference between magnetic north as identified by a magnetic compass and true north.

Deformation till

Poorly sorted, often bouldery deposit left by an ice sheet or glacier resulting from deformation and mixing of sediments overridden by the ice.


Term introduced by Herodotus in the 5th century BC for the triangular plain that develops at the mouth of a river where i.e.ters a lake or sea. The shape of the plain resembles the Greek capital letter 'delta'. See Sites: W3


Mass per unit volume. See Sites: S134


Synonym for décollement.


Used in structural geology to refer to sense of movement of one crustal block to another (e.g., dextral strike slip fault). In this case, to move to the right of the observer. Equivalent to 'right lateral'.


Dark-coloured igneous rock lacking much silica and related to basalt but coarse.g.ained, and commonly found in dikes and sills. See Sites: C7, N5, N34, N51, N61


The chemical and physical changes that occur in sediment or rocks at relatively shallow depths and thus at low temperatures (contrast with metamorphism).


Generic term given toa poorly sorted rock composed of large and small particles, regardless of origin whether volcanic, glacial etc. Diamictite is a lithified diamict. See Sites: S148


Carbon that is crystallized at great depth (150kilometres) in the Earth's mantle and under very high pressure and temperature. See Sites: C87, E37, S134


The sequential formation of different minerals from a cooling magma (see Bowen's Reaction series).


A vertical wall-like igneous intrusion that cross cuts older rocks and/or other structures. Also spelt as dyke. See also sill. See Sites: C7, C8, C19, C62, C116, C119, C133, C136, E13, N29, N34, N48, N51, N67, N81, N97, N99, N115, S143

Dike swarms

A large number of dikes intruded at about the same time forming criss-crossing intrusions. Usually associate with the stretching (extension) of the Earth's crust and takes pace at mid-ocean ridges and in continents.


A coarse-grained igneous rock of intermediate composition. See Sites: C56, E6, E7


The angle between a tilted rock layer and the horizontal. Refers to the direction in which a drop of water would flow down such a layer. See Sites: C27, C56, C59, C109, C116, E6, E7, E40, N22, N33, N99, W4, W6


An unconformity where beds above and below are parallel. Usually separates formations of strata.

Displaced fauna

Fossil fauna contained in rocks that are exotic relative to those of adjacent rocks, and commonly indicating affinities to distant biogeographic provinces. Such faunas are part of the evidence incorporated into terrane analysis.


Weathering process whereby rocks or sediments are eroded by passing directly into solution within water. It is a very common process affecting limestones of Southern Ontario (see karst). See Sites: E11, E43, N79, S60, S94, W14

Divergent plate boundary

The boundary separating two plates moving away from each other. Grabens and mid-ocean ridges occur here.


Area of high ground separating two drainage basins. See Sites: N115, S117


The arrival and suturing of one terrane against another during an orogeny.


Carbonate mineral with the composition CaMg (CO3) 2. A limestone rich in the mineral dolomite is called a dolostone. See Sites: C59


Hard sedimentary rock that contains the mineral dolomite. Dolostone forms the Niagara escarpment in Ontario. Results from diagenesis of limestone by circulating water (diagenesis) at shallow depths underground. See Sites: C102, E3, E22, N41, N43, N77, S18, S22, S30, S47, S48, S52, S53, S77, S104, S122, S127, S132, W30, W31, W38, W43

Double refraction

The splitting of light rays moving through a crystal due to the atomic arrangement of the crystal.

Drainage basin

The total area drained by a stream and its tributaries; also known as a watershed. Divides separate one drainage basin from another.


Nineteenth century 'umbrella' term still used for all unconsolidated sediment deposited by a glacier or by meltwater derived from a glacier (see till and outwash). See Sites: C48, E21, E28, S3, S16, W22, C138


Long streamlined hill made up of till and other sediment; resembles an upturned boat with the bow (the sharp end) facing upglacier. See Sites: C42, C48, C71, C122, C137, E50, N43, N44, E64, E66, E67, E69, E70, E71, E72, E73, E76, E77, C138, C139, C140, C141, C142, C143, C144, C146, C147

Dynamic topography

Refers to slow uplift and subsidence of continental interiors in response to thermal changes in the upper mantle. Also known as epeirogeny.


Near-horizontal surface above which crustal rocks have been displaced laterally by thin-skinned tectonics.


Sudden shaking of the ground as the result of a sudden release of energy created by movement along a fault. See Sites: E15, N2, N6, N11, N35, N95, N96, N116, S3, S20, S42, S59, S61, S110, W37


Single negatively-charged particle.


A substance that cannot be broken down to other substances by ordinary chemical methods. Characterized by the number of protons in the nucleus. See Sites: E19, N24


Sediments or landforms formed by the action of wind (e.g., sand dunes) See Sites: C30, S134


Division of geological time e.g. Phanerozoic eon referring to the time between 570 million years and the present day. See Sites: C80, E50, N67, S32, W45, E64, E65, C146


Strata or rocks that were deposited during any one eon.


Refers to primarily vertical movements of continental interiors that have affected large areas in contrast to the more localized effects of orogenic activity (i.e. Mountain building). In reality the two are related in that orogeny along a plate margin particularly the subduction of large slabs of oceanic crust, can have far reaching epeirogeni.e.fects in the plate interior. See also dynamic topography.


The point on the Earth's surface lying immediately above the focus of an earthquake.


The uppermost layer of a lake which are warmed as a result of solar radiation and which is less dense than deeper, colder layers.


A subdivision of geologic time e.g., Pleistocene epoch from 1. 8 million to 10, 000 years ago (see series)


Division of geologic time smaller than an eon e.g., Mesozoic era between 245 and 66. 4 million years ago. See Sites: C21, C33, C34, C38, C41, C42, C47, C48, C51, C52, C53, C54, C56, C59, C66, C67, C69, C80, C84, C85, C90, C98, C99, C103, C109, C114, C116, C118, C119, C120, C124, C126, C128, C129, C133, C134, C135, E2, E5, E6, E7, E9, E12, E14, E18, E21, E22, E25, E28, E30, E31, E32, E40, E42, E43, E44, E47, E52, E54, E62, N1, N7, N13, N18, N19, N34, N44, N45, N46, N59, N62, N63, N82, N90, N92, N94, N96, N109, N110, N113, N118, S2, S6, S15, S17, S20, S21, S27, S39, S40, S47, S49, S50, S53, S54, S56, S60, S65, S66, S77, S82, S84, S85, S92, S93, S94, S98, S109, S111, S117, S121, S123, S129, S134, W1, W13, W14, W26, W31, W36, W37, W39, W41, W44, E63, E65, E67, E69, E72, C138, S141, S143, S144, S146, S147


Strata or rocks that were deposited during any one era.


The physical removal of broken rock particles or sediment by running water, ice or wind. See Sites: C57, C58, C137, E10, E38, E42, N40, N61, N92, S13, S19, S36, S100, S110, S134, W26, W31, W32, E64, C138, C142, C146, C148, S141


An glacier-transported boulder that is now found a long way from its source. See Sites: C21, C32, C45, C71, S51, S63, S68, S96, S105, S115, S132, S133, S140, S142, E85


A cliff or very steep slope. See Sites: C25, C27, C48, C86, E11, E29, E50, N37, N42, N43, N86, S17, S18, S22, S26, S27, S28, S30, S31, S33, S36, S37, S40, S41, S44, S47, S52, S53, S55, S77, S79, S80, S82, S87, S88, S90, S92, S97, S98, S104, S109, S122, S123, S127, S132, W13, W14, W15, W16, W17, W18, W19, W20, W21, W22, W24, W26, W27, W28, W30, W31, W33, W38, W43, E64, E65, E66, E67, E69, E70, E72, E73, C138, C148, S147


A long sinuous ridge of sand and gravel deposited by water flowing under a glacier or ice sheet. See Sites: C28, C41, C48, E64, E67, E69, E70

Etch plain

Term used for the surface of Canadian shield that has experienced cycles of deep weathering and repeated stripping of rotten rock resulting in an etched landscape where weaker layers or zones of Fractured rock have been removed by erosion.


Obsolete (pre-plate-tectonic) term for the belt of deep-water sediments and volcanic rocks that commonly forms the centre of many orogenic belts. Now known to represent the remnants of vanished (subducted) oceans and their continental margins.


A crystal that has a perfect form.


Complex bacteria that first appeared around 2. 8 ga having a distinct nucleus in which DNA is stored.


Term used to refer to world wide changes in sea level such as for example, created when large continental ice sheets grow.


A rock that forms by precipitation of dissolved minerals during evaporation of seawater. Examples of evaporite minerals are halite and gypsum.


Refers to water lost to the atmosphere by evaporation from land and water surface, and vegetation.


The re-exposure of an ancient landscape by present-day erosion.


Place where rock or sediment i.e.posed at the Earth's surface (also called an outcrop). See Sites: N17, N47, N91, S24, E64, C141


The simultaneous termination of many different varieties of animal and plant life. At least five major extinctions are known to have occurred during the last 600 million years, including that at the end of the Permian and that which terminated the dinosaurs at the end of the Cretaceous (65 million years ago).

Extrusive igneous rock

Molten rock (magma) that reaches the earth's surface see lava and pyroclastic debris. Contrast with intrusive igneous rock.


The overall orientation of clasts within sediment or of structures within a rock.


Latin for 'appearance of' from which the word 'face' is derived. Used by geologists to identify different characteristics within any one rock or sediment unit. Geologists speak of metamorphic, igneous and sedimentary facies referring to slightly different appearances (and thus origin) of such strata. Rocks may simply be a different colour (e.g., red facies), grain size (e.g. Coarse grained facies) or origin (e.g., fluvial sandstone facies, shallow marine limestone facies etc). See Sites: E69, C141

Failed arm

The third arm in a three-armed graben (rift) that ceases to develop further when continental crust breaks apart (also known as an aulacogen).

Fallback breccia

Poorly sorted rock that results from meteorite impact and the ejection of broken and pulverized rock.


Conglomerates deposited on an alluvial fan.


A fracture in bedrock along which movement has taken place of the blocks either side (see normal and Reverse faults). See Sites: C87, E21, E27, E28, N4, N5, N6, N11, N21, N78, N84, N92, N93, N95, N100, N109, N117, S3, S110, E66, E68, E73, C138

Fault gouge

Intensely sheared and comminuted rock found along a fault plane and recording abrasion of rock during faulting. Commonly show slickensides.

Fault plane

The planar surface or contact along which rocks have been faulted. Commonly associated with fault gouge.


Most common mineral group (making up 60% of the Earth's crust) composed of silicate minerals (various elements combined with silica and alumina) occurring as components of virtually all rocks. When they weather they produce much of the clay in soils. See Sites: C21, C34, C38, C53, C55, C62, C119, C136, N15, S121, S134, S141, S144, S146


A term (derived from feldspar and silica) for an igneous rock that is rich in silica and which also contains high amounts of potassium and sodium feldspars (e.g. Granite).


A narrow coastal inlet in mountainous coastal areas that was carved by a glacier. The bedrock floor lies deep below sea level. Also spelt as fjord.


Coarse, sugary snow on the upper part of a glacier or ice sheet remaining from previous winters. With burial below later layers, firn turns into glacier ice.


A deep crack in a rock. Often found in Southern Ontario along the crest of the Niagara escarpment as a narrow cave formed by downslope creep of large blocks of rock. See Sites: E11, S94, W14, W21, W22, E67

Flash flood

Refers to abrupt increase in flow velocity and volume in a river. In Southern Ontario it is associated with the rapid runoff of rainfall or snowmelt from urban areas underlain by large areas of impermeable material such as asphalt, concrete, roofs etc.


A sedimentary form of the mineral quartz commonly used for tools and fire amougst primative humans. See Sites: C100, N77, N113

Flute marks

Small erosional pits elongated in the direction of current movement, caused by turbulent water motion at the base of turbidity currents. They are good paleocurrent indicators.


Relating to processes and sediments and sedimentary structures associated with rivers e.g., a fluvial sandstone is one which was deposited by a river. See Sites: C41, S134, E64, C142


The area below the Earth's surface where an earthquake is generated. The point on the Earth's surface immediately above the focus is called the epicentre. See Sites: C116, E52, S32, E64


Rock that has been bent by heat and pressure (see also syncline and anticline). See Sites: C2, C6, C8, C53, C59, C113, C115, C130, E41, E54, N33, N42, N45, N96, N111, N116, S143

Fold and thrust belt.

Region of deformed rocks produced during an orogeny. Usually associated with the formation of high mountains.


The banded appearance seen in metamorphic rocks such as gneiss. See Sites: E54, S143


A mass of rock lying below a fault plane. See Sites: E66

Foreland basin

Sedimentary basin formed by loading of the edge of a continental plate by overthrust rock masses.


Gently dipping beds of silt and sand formed on the front of a delta (see bottomset, topset)


Term used for agroup of beds or strata lying on top of the other to form a package that shows similar overall characteristics. Separated by disconformities marking non-deposition or slight erosion. See Sites: C29, C31, C37, C40, C51, C56, C77, C85, C107, C114, C124, C127, E3, E6, E7, E8, E13, E27, E43, E50, N8, N9, N10, N19, N27, N35, N41, N52, N58, N59, N63, N78, N81, N96, N103, N109, N111, N113, N114, N116, N119, S8, S9, S21, S22, S29, S42, S43, S59, S61, S62, S68, S82, S116, S121, W7, W8, W10, W22, W26, W31, W41, W47, E63, E64, E66, E69, E70, C138, S143


Remains of plants or animals preserved in rock or sediment. See Sites: C31, C60, C73, C80, C127, E29, E31, E43, E52, N40, N74, N77, N78, S15, W7, W34, W41, S147

Fossil fuel

Energy stored by plants and animals in the geological past and preserved as organic compounds (e.g., coal, oil).


The way a substance breaks where not controlled by cleavage. See Sites: C21, C59, C61, C133, N29


A highly effective weathering process that acts to disintegrate rock by infiltration of water into joints and fractures which then freezes. Volume expansion accompanying the formation of ice splits the rock. Later thawing allows further infiltration of water.


Abbreviation for Giga-annum to refer to the age of an event or rock in billions of years (e.g. 1, 000, 000, 000 years or 109 years). See also ma and ka. See Sites: C14, C16, C19, C23, C25, C29, C36, C37, C39, C41, C48, C54, C55, C58, C59, C60, C64, C78, C83, C85, C86, C87, C90, C99, C100, C103, C116, C126, C127, C128, E10, E11, E14, E15, E16, E17, E20, E21, E22, E24, E28, E32, E37, E41, E45, E53, E50, E54, E56, E58, E59, N8, N9, N10, N23, N32, N36, N37, N38, N41, N42, N43, N44, N46, N49, N50, N52, N64, N65, N81, N83, N91, N99, N103, N104, N107, N115, N119, S11, S12, S17, S22, S23, S26, S27, S28, S29, S30, S31, S32, S33, S34, S35, S36, S37, S38, S40, S41, S42, S43, S44, S45, S47, S48, S49, S50, S51, S52, S53, S54, S55, S56, S57, S58, S59, S67, S68, S71, S72, S73, S77, S79, S80, S82, S84, S87, S88, S90, S92, S94, S95, S97, S98, S102, S104, S109, S112, S116, S117, S118, S119, S122, S123, S126, S127, S132, S134, S135, W3, W9, W10, W11, W13, W14, W15, W16, W17, W18, W19, W20, W21, W22, W23, W24, W25, W26, W27, W28, W29, W30, W31, W33, W34, W36, W38, W43, E64, E65, E71, C140, C141, C142, E80, S141, S147, S148


A dark coloured, coarse-grained and dense rock of mafic composition (i.e. One rich in iron and magnesium.) See Sites: C37, N99, N104, N107, E80, S141


Waste minerals of no value associated with an ore body. See Sites: N119

Gas hydrate

A snow like substance formed in deep cold sediments on ocean floors that are able to trap methane gas.

Geological province

Long standing term used by geologists to refer to distinct regions of the North American craton where rocks are similar but very different from surrounding areas; often used interchangeably with terrane.


Canadian term first used in 1969 and now widely adopted in reference to mapping the form and topography of the earth's surface in all its forms whether natural or man made, using new survey technology afforded by satellite positioning systems etc.


The application of physics to discover burie.g.ological features below the ground surface.


Literally means the 'rocky sphere' i.e. The Earth's crust and its rocks.

Geosynclinal cycle

Obsolete term referring to the typical sedimentary fill of foreland Basins, which characteristically reveals a gradual shallowing of the basin with time.


Term, now no longer used by geologists, to refer to a deep sedimentary basin. Term was introduced in 1859 long before appreciation of how planet Earth works. Geologists identify many types of sedimentary basins related to different tectonic settings.

Geothermal gradient

(Or geotherm) The rate of temperature increase with depth below the Earth's surface, approximately 25oC/kilometres.

Glacial rebound

The upward movement of the Earth's crust afterhaving been depressed below the weight of a large ice sheet (see also glacio-isostatic and isostasy).


A large mass of ice, formed on land by the compaction and recrystallization of snow and firn, and which moves (flows) under the influence of gravity (see ice sheet). See Sites: C41, C42, C48, C65, C131, E53, N41, N43, N58, N69, N93, N103, S133, C144


Refers to deposition or erosion by glacial meltwaters. See Sites: C41, C142


Refers to vertical movements of the Earth's surface caused by loading and unloading caused by growth and decay of large ice sheets.

Glacioisostatic depression

The downward movement of the Earth's crust under the load of a thick ice sheet.


Scientist who studies glaciers and Ice sheets


Soils in wet boggy areas with grey coloured b horizons due to inability of iron to oxidize.


A high-grade metamorphic rock composed of alternating light and dark mineral layers (see foliation). See Sites: C2, C4, C6, C7, C8, C19, C20, C56, C73, C80, C87, C92, C109, C110, C111, C124, C130, C136, E6, E7, E13, E32, E44, E48, E54, N29, N99, N115, S96, S105, S143, S145


The southern part of the supercontinent pangea that was composed of the continents India, South America, Africa, Australia and Antarctica.


Rusty coloured iron-bearing cap of weathered sulphides. Used by prospectors in search of mineral deposits.


A topographic low formed by the subsidence of large blocks of rock between faults (see aulacogen and rift). See Sites: E21, E28, N11, N68, N82, N84, N86, S3

Graded bed

A bed of sediment or sedimentary rock that shows a systematic upward change in particle size resulting from deposition by a turbidity current. Also known as a bouma sequence.


A progressive change in grain size throughout a bed. See Sites: C40


A coarse-grained plutonic and felsic igneous rock that consists mainly of feldspar, quartz and mica. See Sites: C7, C8, C20, C21, C34, C58, C59, C65, C73, C84, C88, C97, C100, E42, E46, N16, N36, N51, N53, N70, N92, N98, N114, N115, S96, S103, S118, S119, S144, S146


A term for a magma or igneous rock of felsic composition; synonymous with rhyolitic. See Sites: C62, C109


A light colored rock that is very simular to granite, but contains less potassium feldspar and more plagioclase feldspar giving it lighter color and may contain hornblende.


Sediment composed of particles (clasts) that are larger than 2mm in diameter. When cemented it forms a rock called a conglomerate or breccia according to the dominant shape of the clasts. See Sites: C26, C29, C41, C88, N30, S24, S25, S39, W46, E65, C142


Old (German) term used for poorly sorted sandstones deposited by turbidity currents before origin was fully recognized. Turbidite is a more appropriate modern usage.

Greenstone belt

A common component of archean crust in Canada where large volumes of basalt were erupted on the ocean floor. The term refers to the green colour of metamorphosed basalt. These belts are examples of lipS. See Sites: N16, N17, N18, N19, N87


Old (German) term used for poorly sorted sandstones deposited by turbidity currents before origin was fully recognised. Turbidite is a more appropriate modern usage.


The fine-grained matrix in a porphyritic igneous rock.


Subsurface water that is contained within the pore spaces of rocks and sediments and which is able to flow under the influence of gravity or pressure (see head). See Sites: N114, N119, S48, S120, W36


Several stratigraphic formations that are lumped together to form a thicker package of strata that can be kilometres in thickness. Groups are separated by major unconformities. See Sites: C6, C65, C134, E22, E24, N28, N47, N87, N90, S40, S76, S126, W9, W47, E64, S143


Flat-topped underwater mountain on the ocean floor. They originate as tall volcanoes that became extinct, were eroded by waves to form atolls. With time they slowly sink below sea level as underlying oceanic crust ages and becomes more dense. Named after Arnold Guyot a nineteenth-century geologist.


A common sulfate mineral (CaSO4, H2O) formed by evaporation of seawater. See Sites: S60


The time it takes for a given amount of a radioactive isotope to be reduced to one half by decay (see daughter atom).


Sodium chloride (NaCl) formed by evaporation of seawater.

Hanging wall

The mass of rock that lies above a fault plane (see footwall).


The resistance of any material to being scratched. Used to identify different mineral types (see mohs hardness scale from Talc to diamond). See Sites: S144

Hash layer

A layer within a sedimentary rock such as limestone composed of fossil debris; usually formed by storms and large waves stirring up the seafloor.


Water pressure that builds up in an aquifer as groundwater flows from one elevation to another. See Sites: C67, C73, E26, N13, N24, S120, S136, W8, W18, W46, E80

Heavy oil

Oil found at shall depths where lighter components have been flushed by groundwater leaving a sticky bitumen adhering to sand grains.

Heinrich layer

Layers of ice rafted sand grains found in northern ocean sediments recording massive outbursts of icebergs from the last ice sheets.


The current interglacial that began c. 10, 000 years ago with the final melt of northern hemisphere continental ice sheets. Once seen as a period of uniform climate, there is now evidence of major swings in temperature e.g., little ice age etc.


A non-foliated rock with uniform grain size formed from high temperature metamorphism; often found in a metamorphic aureole near igneous intrusions.

Hot spot

An area on the Earth's surface lying directly above a mantle plume. Marked by volcanoes that occur in the middle of lithospheric plates (e.g., Hawaii) rather than, as normal, at their margins. See Sites: E8, N2

Hot spot tracks

Linear chain of volcanoes resulting from the movement of the lithosphere over a mantle plume whose position remains fixed (hot spot). Study of hot spot tracks provided a critical test of the theory of plate tectonics in the 1960's.

Hummocky cross-stratification

Curved laminations arranged i.e.ther a convex or concave fashion in sandstones deposited below large waves during storms in seas and lakes.


Lava broken into fragments during rapid cooling, upon being erupted under water.


The scientific study of groundwater.


The record of changing water levels or velocities along a river.


Weathering process whereby feldspar minerals in igneous rocks breakdown to produce clay.


Literally means the 'watery sphere', i.e. The envelope of water and water vapour that surrounds planet Earth.


The action of very hot water circulating through rocks.


Adjective describing the property of a water body with higher salinity than sea water, because of a high content of dissolved rock materials. A modern example is the Dead Sea.

Ice sheet

A glacier that is large enough to cover all or part of continents. Southern Ontario has been buried many times by the Laurentide ice sheet. The last one only disappeared 12, 000 years ago. Ice sheets have fundamentally changed the topography of Canada. See Sites: C15, C21, C26, C32, C41, C42, C45, C71, C73, C130, C131, E1, E39, E45, E46, E51, E50, N6, N8, N9, N10, N30, N38, N40, N44, N56, N69, N79, N98, N102, S9, S17, S68, S91, S96, S105, S128, W11, W12, W18, W35, W36, W47, E76, E77, C138, C143, C146, C148, S140, S142, E85

Ice wedge

Vertical structure formed in sediment by cracking of the ground during severe cold of an ice age. Surface water fills the crack and freezes. Successive episodes of cracking and freezing give rise to a carrot shaped mass of ice. When the ice age ends, the ice wedge melts and the crack fills with debris to leave an ice wedge cast as a record of severe cold.

Ice wedge cast

Fossil ice wedge.

Igneous intrusion

Body of igneous rock intruded into older surrounding rock. Found as sills, dikes, or plutons or batholiths. See Sites: C34, C114, C116, E33, E34, N60, N61, N97

Igneous rock

A rock formed from the solidification of a magma; can occur either at the Earth's surface (Extrusive igneous rocks) or underground (intrusive igneous rocks). See Sites: C7, C19, C58, C114, E32, E37, E48, N5, N59, N60, N61, N64, N66, N67, N82, N104, N107, S133, S141, S143, S144, S146


An extrusive igneous rock that is formed from a pyroclastic flow.

Impact crater

The depression on the Earth's (and Moon's) surface created from the impact of a meteorite. See Sites: N1, N80, N90


A rock or sediment that does not allow water to pass through (see aquitard and permeable).


Any part of an igneous rock or mineral which is distinctly different from the materialthat encloses it (se.x.nolith).

Index fossil

Fossils of organisms thatevolved quickly such that the time range of any one type is short. Very useful for correlating the rocks found in one area with another.

Index minerals

Minerals used to identify different degrees of metamorphism.


Refers to an area of older strata surrounded by younger rocks. An example would be where glaciers have excavated through younger cover rocks to expose the Canadian shield below. Opposite of outlier. See Sites: C22


The group of silicate minerals where tetrahedra are connected in single or double chains.


A brief period of warm climate between major glaciations. We live in the current interglacial called the holocene. It too will end in a few thousand years. See Sites: N8, N9, N10, S15


The area between two lobes of an ice sheet e.g., the interlobate Oak Ridges moraine of Southern Ontario.


A term for a rock that has a silica composition between mafic and felsic compositions (e.g., andesite, diorite).


Body of magma that intrudes other rocks such as a dike, sill or pluton. These are composed of intrusive igneous rocks. See Sites: C34, C59, C114, C116, C136, E33, E34, E38, N60, N61, N64, N97

Intrusive igneous rocks

Those formed by cooling of molten rock (magma) below the Earth's surface.


An electrically charged atom or group of atoms. See Sites: C2, C4, C6, C8, C9, C10, C13, C16, C19, C20, C22, C25, C29, C31, C33, C34, C35, C36, C37, C39, C40, C43, C46, C47, C51, C53, C56, C57, C58, C59, C63, C65, C68, C69, C70, C71, C72, C73, C74, C75, C76, C77, C78, C80, C81, C83, C84, C85, C86, C89, C92, C94, C96, C99, C101, C102, C103, C104, C105, C106, C107, C108, C109, C111, C112, C113, C114, C116, C117, C118, C120, C122, C124, C125, C126, C127, C128, C129, C130, C137, C133, C136, E2, E3, E4, E6, E7, E8, E9, E10, E11, E12, E14, E15, E16, E13, E17, E18, E20, E21, E22, E24, E25, E27, E28, E29, E30, E31, E32, E33, E34, E36, E37, E38, E40, E41, E42, E43, E44, E45, E46, E47, E48, E49, E51, E52, E50, E54, E55, E56, E57, E58, E59, E60, E61, N2, N5, N6, N8, N9, N10, N13, N14, N15, N16, N17, N18, N19, N20, N21, N23, N25, N27, N28, N31, N32, N33, N34, N35, N37, N38, N39, N40, N41, N42, N44, N45, N47, N48, N49, N52, N54, N57, N58, N59, N60, N61, N63, N64, N66, N67, N68, N69, N70, N75, N76, N78, N79, N80, N81, N82, N83, N84, N85, N86, N87, N88, N89, N90, N91, N92, N93, N95, N96, N97, N98, N99, N100, N102, N103, N104, N105, N106, N107, N108, N109, N111, N112, N113, N114, N116, N117, N118, N119, S1, S3, S4, S6, S7, S8, S9, S10, S11, S13, S15, S17, S19, S20, S21, S22, S23, S24, S28, S29, S31, S32, S34, S36, S37, S38, S40, S41, S42, S43, S44, S45, S46, S48, S49, S50, S53, S54, S55, S56, S57, S59, S60, S61, S62, S65, S66, S67, S68, S69, S72, S73, S75, S76, S77, S78, S79, S82, S83, S84, S85, S86, S89, S90, S91, S92, S94, S98, S99, S100, S102, S103, S104, S105, S106, S107, S108, S110, S112, S114, S115, S116, S117, S119, S120, S121, S125, S126, S127, S129, S131, S132, S133, S134, S137, W3, W5, W6, W7, W8, W10, W11, W12, W14, W16, W22, W23, W25, W26, W27, W29, W31, W32, W33, W34, W36, W37, W41, W43, W44, W45, W46, W47, E63, E64, E65, E66, E68, E69, E70, E72, E73, E74, E75, E78, C138, C140, C141, C142, C145, C146, C148, E80, S140, S141, S142, S143, S144, S146, S147, S148

Iron meteorite

A meteorite that is mainly composed of iron-nickel alloy.


Lines drawn on a geologic map akin to contours, showing the thickness of any one rock type or strata.


Refers to the relationship between relatively rigid crust of the Earth and the relatively soft underlying mantle. Any additional weight placed on the crust (such as where the crust is thickened during an orogeny and large mountains form, or by the growth of an ice sheet) results in isostatic depression or down warping.


An atom that has a different number of neutrons but the same number of protons as another atom of the same species. Some are unstable and breakdown (see radioactive decay).


A fracture or crack in bedrock along which essentially no displacement has occurred. See also fissure. See Sites: C21, C61, E3, N41, S8, S94, W22, W32


Shortened version of kilo annum (a thousand years). Unlike the prefixes Mega and Giga, the k is not capitalized. See Sites: C26, C29, C44, C58, C65, C66, C79, C85, C87, C91, C116, C119, C124, C130, E3, E5, E9, E29, E33, E34, E43, E51, E54, N2, N4, N5, N6, N11, N17, N36, N40, N50, N59, N65, N66, N71, N79, N81, N82, N84, S47, S63, S66, S82, S94, S105, S106, S115, S134, W2, W14


A hill composed of sand and gravel deposited by waters flowing under or from a glacier or ice sheet (see esker). See Sites: C26


Refers to processes and landforms associated with dissolution of carbonate bedrock such as limestone to form an underground cave system (see also thermokarst). See Sites: E3, E29, E43, E51, N79, S47, S94, W14


Fossilized organic material derived from plantsthat can be converted to petroleum by distillation.

Kettle lake

A lake within a shallow enclosed depression created by the melt of glacier ice that was buried by glacial sediment during the retreat of an ice sheet. See Sites: N18, S17


Dark coloured ultramafic igneous rocks found in kimberlite pipes which originate from deep within the Earth's mantle. May contain diamonds. See Sites: E37

Kimberlite pipe

Carrot shaped body of igneous rock derived from the Earth's mantle. See Sites: E37


Indonesian word for mudflow moving down the slopes of a volcano and composed of large volumes of ash and other pyroclastic debris; can be extremely destructive in populated areas.


Thin (<1cm) layers within a sedimentary rock.


Term used for a waste dump or where waste materials have been used to fill topography to create flat land for construction. See Sites: S2, S12

Lapilli tuff

A lithified volcanic ash formed of fragments between 2 and 64 mm.


Name given to the North American continent that broke out from rodinia after 750 ma. See Sites: N21, N26, N86, N115


Name given to an enlarged laurentia when it collided with the Baltic and Siberian plates after about 440 ma.


Magma found on the earth's surface and associated with extrusive igneous rocks. See Sites: E8, N15, N16, N17, N18, N48, N57, N68, N103, S73


The liquid produced within a landfill or waste dump by the interaction of rainwater with waste and chemicals in the dump.


To dissolve and remove the soluble constituents of a rock or soil.

Left lateral

Where the opposing block of a fault moves to the left of an observer looking across the fault.


Also known as brown coal, it is a low grade coal formed by the compression of peat.


A sedimentary rock that is composed of over 90% calcium carbonate. See Sites: C1, C8, C13, C22, C24, C25, C31, C35, C36, C48, C56, C60, C61, C63, C68, C79, C84, C88, C93, C103, C105, C112, C122, E2, E3, E6, E7, E11, E12, E14, E19, E24, E27, E29, E32, E34, E41, E42, E43, E44, E45, E47, E51, E53, E50, E62, N6, N37, N42, N43, N44, N73, N74, N77, N78, N79, N91, N94, S4, S29, S30, S40, S47, S51, S52, S53, S60, S64, S70, S72, S74, S75, S79, S83, S86, S94, S96, S107, S108, S132, W4, W6, W7, W14, W25, W29, W35, W43, W47, E64, E65, E66, E67, E68, E69, E71, E72, E73, E77, C138, C140, C141, C143, C144, C146, C147, C148, S140, S147, E85


Any structures in old rocks buried below younger strata which are identified by geophysical surveys but whose origin is unclear.


Acronym for Large Igneous province. These record short lived volcani.e.ents when enormous volumes of magma were erupted on the floor of the oceans (oceanic plateau) on land as continental flood basalts) or intruded (such as dike swarms). Possibly associated with momo events. See Sites: N5, N95, S37, W40


Adjective describing the tendency of faults to flatten out downwards. Typically they end at a near-horizontal surface of décollement or detachment.


Usually applied to sandstones composed of bedrock fragments produced by the weathering and erosion of other rocks. Usually form close to source areas where transport is insufficient to breakout smaller particles composed of minerals such as quartz or feldspar (see also arenite and arkose).


The processes by which sediment is converted into a sedimentary rock usually by cementation. See Sites: N27

Lithoprobe project

A multidisciplinary project, funded by government, industry and the universities, to explore and interpret the deep crustal structure of Canada. The project extended from 1982-2005 and involved hundreds of scientists. Crustal seismic-reflection profiling constituted the main basis of the project, together with supplementary geophysical and surface geological studies.


The relatively rigid outer layer of the Earth which is composed of continental and oceanic crust.

Lithospheric plates

The Earth's lithosphere is broken into 20 or so major plates that are moving and interacting with each other. Each plate has a passive margin where new crust is being formed and an active margin where crust is being destroyed (subduction) below adjoining plates or being compressed against other plates (obduction).

Little ice age

Period of cool temperatures and glacier expansion from about 1300 to 1900 A. D.


Wind blown silt that accumulates to considerable thickness in parts of northwest Canada (e.g., Yukon) which remained unglaciated but severely cold and dry.

Longshore drift

Refers to movement of water and sediment along the shorelines of lakes and seas in response to waves (see spit).


The way light reflects from a surface of a mineral. See Sites: W9


Well-developed mature soil found in Southern Ontario having a clear internal structure composed of different horizons.


Abbreviated form of Mega-annum meaning a million years. The initial letter is always capitalized (unlike ka). See also ga. See Sites: C3, C6, C7, C11, C12, C13, C15, C16, C18, C19, C20, C21, C23, C24, C25, C26, C27, C29, C31, C34, C35, C36, C37, C38, C39, C40, C41, C45, C47, C48, C50, C51, C53, C55, C56, C57, C58, C59, C60, C62, C63, C64, C65, C66, C68, C70, C71, C73, C75, C76, C77, C78, C79, C80, C81, C82, C84, C85, C86, C87, C88, C89, C90, C92, C93, C96, C97, C98, C99, C100, C101, C102, C104, C105, C106, C107, C109, C110, C111, C112, C113, C114, C115, C116, C117, C118, C119, C121, C122, C124, C125, C126, C127, C128, C129, C130, C137, C131, C132, C133, C134, C136, E2, E3, E4, E5, E6, E7, E8, E10, E11, E12, E14, E15, E16, E13, E17, E18, E19, E20, E22, E25, E27, E29, E30, E31, E32, E33, E35, E37, E39, E40, E41, E42, E43, E44, E45, E46, E47, E51, E52, E53, E50, E56, E57, E58, E59, E62, N1, N2, N5, N7, N8, N9, N10, N11, N12, N13, N14, N16, N19, N20, N21, N22, N23, N27, N30, N32, N33, N34, N35, N36, N37, N38, N39, N40, N41, N42, N43, N44, N45, N46, N47, N49, N50, N51, N52, N53, N54, N56, N57, N58, N59, N60, N61, N62, N63, N68, N69, N71, N72, N73, N74, N75, N76, N77, N78, N79, N81, N82, N83, N84, N87, N88, N89, N90, N91, N93, N94, N95, N96, N97, N98, N99, N100, N102, N103, N106, N107, N108, N109, N110, N111, N112, N113, N114, N115, N116, N118, N119, S1, S2, S3, S5, S6, S7, S8, S9, S10, S11, S12, S13, S14, S15, S18, S20, S21, S22, S23, S24, S25, S28, S29, S30, S31, S32, S33, S35, S36, S37, S38, S39, S40, S41, S42, S43, S44, S45, S47, S48, S50, S51, S52, S53, S59, S61, S62, S65, S68, S69, S71, S72, S73, S74, S75, S76, S77, S78, S79, S80, S81, S82, S83, S85, S86, S87, S88, S89, S90, S91, S92, S94, S95, S96, S97, S100, S102, S103, S104, S105, S106, S107, S108, S109, S112, S113, S114, S116, S117, S118, S119, S120, S121, S124, S125, S126, S127, S128, S129, S131, S132, S133, S134, S135, S136, S137, W1, W2, W7, W8, W9, W10, W13, W14, W15, W17, W18, W19, W20, W22, W23, W24, W25, W26, W27, W28, W29, W30, W31, W32, W33, W34, W35, W36, W37, W39, W41, W44, W45, W46, W47, E63, E64, E65, E66, E67, E68, E69, E70, E73, C138, C143, C144, C146, C147, C148, E80, S140, S141, S142, S143, S144, S145, S146, S147, S148


The term for a rock such as basalt which is rich in iron and magnesium silicates (ferromagesian Minerals) such as olivine and amphibole. See Sites: C113, C114


Molten igneous rock with suspended crystals and gases within it. See Sites: C58, C62, C133, N82, S141, S144, S146

Magmatic underplating

Usually refers to the widespread invasion of continental margins by granite and other intrusions. Can occur along a newly rifted margin impacted by a mantle plume or along an active margin where subduction is taking place. Results in thickening and strengthening of continental crust.

Magnetic anomaly

A deviation in the strength of Earth's magnetic field from the average value resulting from structures such as faults, plutons etc. Identified by a ground, marine or aeromagnetic survey using a magnetometer.

Magnetic dating

Dating of sediments and rocks by comparing their magnetic record to the magnetic polarity timescale of age-dated magnetic reversals.

Magnetic declination

The angular difference between true north and magnetic north. Varies across Canada.

Magnetic north

The point on the Earth's surface which a compass needle points to.

Magnetic polarity timescale

Refers to succession of magnetic reversals in a whose age is known. Used to age-date other strata most commonly igneous rocks showing a similar magnetic history.

Magnetic reversal

A change in the polarity of the Earth's magnetic field.

Magnetic stripes

Refers to alternatingbands of normal and reversed polarity either side of mid-ocean ridges. Can be age dated according to the magnetic polarity timescale.


An instrument used to measure very small variations in the Earth's magnetic field. Can be towed behind a boat (a marine magnetometer) or used from a airplane (an airborne magnetometer).


The zone in the earth's interior that lies between the lithosphere andthe Earth's core. See Sites: C37, E37, N82, N99, S5, W22, E67, E70

Mantle plume

Column of hot material rising toward the Earth's surface as a result of large-scale convection in the mantle (think of a lava lamp).


A coarse-grained metamorphic rock with large grains of Calcite or dolomite formed by heating of a limestone or dolostone. See Sites: C18, C47, C50, C53, C59, C100, C105, C106, C107, C109, C111, C112, C113, C114, C115, C127, E2, E4, E16, E43, E44, N68, S69, S108, S140

Marine limit

Highest elevation at which marine deposits occur along a glaciated coastline. Results from marine flooding of coastline when depressed by weight of ice sheet (see glacioisostatic) and subsequent crustal rebound.


The fine-grained material that fills in between large.g.ains in igneous and sedimentary rocks. Also called groundmass. See Sites: N93, C143, C144

Mechanical weathering

The breakdown of a rock into smaller pieces (sediment) by physical processes such as by glacial abrasion and freeze-thaw.


From the French word 'mixture'. Rock composed of fragments and blocks of all sizes, set in a fine matrix. Can be produced by a wide variety of process such as tectonic shearing, landsliding etc.

Meromictic lake

A lake that has a permanent internal stratification of water of different temperature and density.

Metamorphic aureole

The zone affected by intense metamorphism around an igneous intrusion such as a pluton.


The transformation of pre-existing rock into a new rock as a result of pressure and temperature but without the rock melting. See Sites: C40, C100, C127, E9, E32, S145


Metamorphosed sedimentary rock See Sites: C47, C59, C87, E9, N115


Describes the growth of new minerals as a result of precipitation from hot water circulating through rock at depth in the Earth's crust. Equivalent to Hydrothermalalteration.


Streak of light produced by a particle entering the Earth's atmosphere from space (a fireball). See Sites: E12, N1, N26, N27, N29, N31, N80, N90, N93


A meteor that hits the Earth's surface. See Sites: E12, N1, N26, N27, N29, N31, N80, N90, N93

Mid-ocean ridge

A continuous submarine mountain range up to 3 kilometres high, extending throughout the middle of the ocean basins (over 84, 000 kilometres). Consists of a central rift valley associated with the intrusion and eruption of new oceanic crust (dominantly basalt) by numerous dikes. Repeated intrusion of dikes gives rise to ridge push that drives new oceanic crust apart and is one of the driving forces for plate tectonics (see also slab pull). See also magnetic stripes.


A high grade metamorphic rock where partial melting has occurred. Typically associated with gneiss and mylonite and very common across the Canadian shield See Sites: S145


A naturally occurring inorganic compound or element having an orderly internal structure, physical properties and chemical composition. See Sites: C21, C33, C34, C38, C51, C52, C53, C54, C59, C80, C109, C116, C118, C119, C120, E5, E31, E32, E44, E52, E54, N7, N13, N18, N90, N110, S47, S60, S65, S85, S94, S121, S134, W13, W14, W41, S141, S143, S144, S146, S147


Obsolete (pre-plate-tectonic) term for the wedge of largely shallow-marine and nonmarine sediments flanking an orogenic belt, originally deposited on a stretched and thinned continental margin. (Commonly abbreviated to miogeocline)


The boundary between the Earth's crust and the mantle; short for Mohorovicic discontinuity named after its discoverer. P-waves show an abrupt change in velocity (from 7 to 10 kilometres/sec) across the contact that occurs at about 6 kilometres depth under the oceans and 40 kilometres under continents.

Mohs hardness scale

A list of ten minerals with known hardness; used to determine hardness and thus identify other minerals.

Momo events

Huge mantle plumes that deliver enormous volumes of magma to the Earth's surface either on the ocean floor or on the continents (see LIPS).


A step-like bend affecting strata.


A plutonic igneous rock that's simular to syenite but with more plagioclase feldspar than potassium feldspar.


A ridge or pile of debris deposited along the edge of a glacier or ice sheet. See Sites: C29, C48, C75, C84, C95, E53, S17, S125, S130, S131, E63, E65, E67, E69, E70, C148


A mixture of silt and clay. See Sites: C36, E47, N8, N9, N10, N11, N96, S4, S9, S62, E63, S148


Intensely sheared metamorphic rock with a fine laminated structure produced by faulting at high temperatures and pressures. Commonly part of shear zones marking boundaries of crustal blocks within Canadian shield. See Sites: C92

Native element

Minerals that are made up of a single element and not combined with others (e.g., sulphur, carbon).

Native metal

Metallic minerals made of a single metal (e.g., Silver, Gold, Copper).


An early North American continent including much of northern Europe that existed between 1. 9 and about 1. 3 billion years ago. Acronym for northern Europe and north America. Some employ the term Nuna (an Innuit word for northern lands). Thought to be part of a supercontinent called columbia.


Geologically-recent tectonic activity i.e. Within the last 5 million years or so.

Nepheline syenite

A coarse-grained plutonic formed beneath the crust as it was being torn apart. They contain pegmatites that contain other minerals and elements like uranium. See Sites: C53, C110, S66


The silicate group of minerals composed of isolated tetrahedron and other cations.


A particle within an atom that i.e.ectrical neutral.

Non-point sources

Areal source of contaminants that may enter groundwater such as road salt put on roads or agricultural pesticides on fields.


A mafic intrusive igneous rock containing large crystals of plagioclase and pyroxene, very simular in appearance to gabbro. See Sites: N28

Normal fault

A fault where the hanging wall moves downwards relative to the foot wall. Indicates that rocks have been subject to stretching and have been pulled apart (see graben). See Sites: E27


Innuit word use for mountain top that protrudes through an ice cap and is thus entirely surrounded by ice.

Nuée ardente

A cloud of incandescent volcanic ash. These typically move very fast downslope unde.g.avity.


The collision and overthrusting of one continent over another; subduction and related volcanic activity does not occur. Oceans and their floors are destroyed in the process with remnants preserved as ophiolites.


Volcanic glass formed by very rapid cooling of magma which prevents growth of mineral crystals.

Oceanic crust

The crust underneath the ocean that is on average 6 kilometres thick and composed mainly of basalt. It is formed at mid-ocean spreading centres.


Small (0. 25- 2mm) rounded particles (after the Gk, 'oon' for egg) showing concentric layers of calcium carbonate around a sand grain or shell fragment. Usually form in shallow warm wave agitated waters. Limestones entirely made up of oolites are said to be oolitic


Refers to regionally extensive belts or blocks composedof oceanic crust and of the mantle that originally formed on or deep within mid-ocean spreading centres and now exposed on continents as a result of ocean closure between converging continents.


A naturally occurring material from which a mineral can be extracted economically (contrast with gangue). Usually used for metallic ores. See Sites: C1, C2, C7, C12, C13, C14, C15, C18, C19, C21, C22, C29, C30, C37, C42, C48, C51, C59, C60, C62, C65, C66, C73, C74, C75, C77, C81, C85, C87, C88, C89, C92, C93, C96, C98, C99, C101, C107, C108, C112, C114, C118, C119, C127, C128, C137, C131, C132, C133, C134, C135, C136, E1, E15, E17, E22, E24, E26, E32, E35, E37, E45, E49, E53, E58, E60, N6, N14, N15, N19, N23, N24, N28, N31, N38, N43, N44, N51, N53, N54, N55, N59, N69, N80, N83, N87, N92, N93, N94, N99, N100, N101, N102, N103, N104, N105, N106, N107, N108, N110, N112, N113, N116, N117, N118, N119, S3, S5, S10, S12, S13, S17, S21, S25, S38, S39, S40, S43, S44, S49, S56, S60, S63, S65, S72, S73, S80, S87, S88, S91, S94, S96, S105, S107, S109, S110, S111, S113, S114, S118, S120, S124, S125, S126, S130, S131, S135, W4, W5, W6, W9, W10, W18, W33, W34, W35, W39, W40, W41, W46, E68, C140, C141, C142, C144

Ore mineral

A mineral that has commercial value.

Organic minerals

Materials that are made by organic processes; commonly used in jewelry (e.g., pearl).

Organic sedimentary rock

A rock that is composed mainly of remains from plants and animals (e.g., coal).

Orogenic belts

A regionally extensive belt of strata that has undergone folding and deformation during an orogeny. Usually expressed topographically as mountains. Synonymous with fold and thrust belt such as the Rocky Mountain fold and thrust belt.


Refers to large-scale deformation processes within the earth's crust arising from the collision of lithospheric plates. Gives rise to subduction and obduction and fold and thrust belt.. Continents grow in size when orogenies result in addition of terranes. See Sites: C4, C36, C37, C39, C53, C92, C111, C112, C113, C115, C133, E2, E8, E9, E21, E44, E54, N33, N36, N42, N99, N113, S143


Place where rock or sediment i.e.posed at the Earth's surface and can be studied by geologists. Synonymous with exposure. See Sites: C5, C6, C18, C19, C27, C54, C56, C60, C92, C105, C106, C107, C108, C110, C111, C112, C113, C114, C124, C126, E2, E4, E6, E7, E9, E11, E16, E29, E32, E34, E37, E41, E45, E48, N8, N9, N10, N19, N29, N41, N43, N57, N69, N77, N78, N109, N115, N116, N117, S3, S4, S24, S51, S52, S53, S57, S58, S110, W27, E66


Refers to an of younger rocks, usually a remnant of a formerly more extensive cover, surrounded by older strata. Imagine an isolated area of cover rocks sitting on and surrounded by the Canadian shield. Opposite of inlier. See Sites: C79, N6, S18, S98


Sediment (gravel, sand and silt) deposited by meltwaters flowing from a glacier or ice sheet See Sites: N30, C141


Sediments, most commonly of glacial origin, that rest on bedrock.


Term used to refer to glaciated valleys whose bedrock floors now lie at elevations well below sea level or show enclosed basins that could not have been cut by rivers. These valleys have been deepened by glacial erosion and are commonly filled with deep lakes or very thick sediment fills. Along the coasts of British columbia and i.e.stern Canada in Newfoundland, Labrador and in the eastern Arctic, these valleys have been invaded by rising sea level to form deepwater fiords.

Overlap succession

Refers to rocks that extend across and cover the boundary of two terranes and thus whose age gives a minimum for the collisional event (orogeny) that brought the terranes together.


Minerals that contain oxygen combined with one or more metals (e.g., iron such as Hematite and Magnetite).

P wave

Energy released by an earthquake consisting of alternating pulses of compression and extension and able to pass through liquids and solids (see s wave).


Hawaiian for smooth, this type of basaltic lava was cooled and solidified on land giving it an distinct ropy appearance.


Literally "old currents.” Directions of river, tidal, turbidity, and other currents, as deduced from the orientations of ripples, crossbedding, sole marks and other features.


The study of how ancient organisms interacted with themselves and thei.e.vironment.


The record of past changes in the Earth's magnetic field.


The study of fossils and ancient life forms.


A placer mineral deposit found in a gravel that has experienced burial and been lithified into conglomerate rock. Uranium occurs in paleoplacers that are at least 2. 4 billion years old in Ontario.


An ancient soil now found as a rock layer most commonly resting on an unconformity.


As in "palinspastic reconstruction.” The act of unfaulting faults and unfolding folds to restore a rock mass to its original configuration


The last supercontinent that formed about 350 million years ago and which broke apart some 200 million years ago to form the present continents and oceans. See Sites: C19, E21, E28, N4, N6

Panthalassa ocean

Ancestral ocean that lay on the western margin of laurentia after 750 ma.

Parent atom

The initial radioactive isotope before it undergoes radioactive decay to produce daughter atoms.

Parent rock

The original rock before undergoing metamorphism.

Partial melting

Where a rock experiences incomplete melting during metamorphism (see migmatite). See Sites: S145

Parting lineation

A sedimentary structure formed on sand by the flow of water and consisting of a flat surface with faint ridges that form parallel to the current. As a result the sandstone splits very easily (i.e.'parts') and was favoured by stonemasons.

Passive margin

The trailing edge of a continent which lies opposite to its active margin. Eastern North America is a passive margin; western North America is the active margin where it is colliding with the Pacific plate.


A bare rock surface that is smooth.


A plutonic igneous rock containing very large crystals formed by very slow cooling of a granitic magma deep underground. See Sites: C62, C116, C119, C136, N97, S146


Another word for mudstone.


Gem quality olivine.


An ultramafic coarse-grained igneous rock composed of olivine and pyroxene minerals. Can be found in basalts.


The term for processes, sedimentary deposits and associated structures that are formed under cold climates.


Name given to division of geologic time e.g., Quaternary period, the last 1. 8 million years (see series). See Sites: C31, C116, E27, E59, N79, S23, S90, S93


Refers to the formation of thick underground ice in areas of severe cold such as Canada's Arctic.


Term for a sediment or rock that will allow liquids or gases to pass through freely. See impermeable.

Phaneritic texture

Refers to a coarse-grained igneous rock that cooled slowly from a magma.


Any large crystal in a very coarse-grained (porphyritic) igneous rock e.g., pegmatite.

Phosphate minerals

Minerals that contain the (PO4)-3 complex bonded to cations.


Fine-grained metamorphic rock that has a silky sheen derived from the recrystallization of clay minerals to form mica.


The silicate group where tetrahedron are linked together to form sheets.


The scientific name for scenery. Geologists speak of different physiographic regions.

Pillow lava

Bulbous masses of basalt that were erupted underwater such as at mid-ocean ridges. See Sites: E8, N15, N16, N17, N18, N57


Innuit word for small hill formed by deep freezing of groundwater and upward extrusion of water and bulging of overlying sediment. Typical of areas of permafrost.

Pinnacle reef

A pillar or tower-like limestone reef that grows in deep water.


Uranium ore, in reference to its black colour. See Sites: C120

Placer deposit

Refers to gravel deposits where the concentration of Minerals, typically Gold, is high enough to be mined. These record winnowing by rivers or waves leaving lags of heavier minerals. Placers are common in British columbia and the Yukon, where Gold bearing volcanic rocks underwent weathering in warm climates before the beginning of ice ages of the last 3 million years. Weathered bedrock debris (regolith) was reworked by rivers as climates cooled forming Gold placers. See Sites: S134

Planar cross-stratification

A sedimentary structure found in sedimentary rocks deposited by rivers or by wind where layers are straight but show a gentle dip (cross-bedding). Created by the downstream migration of the front of sand dunes.

Plate tectonics

Refers to formation, movement and destruction of lithospheric plates on planet Earth. It recognizes that Earth's crust and underlying mantle is in constant motion (see wilson cycle). See Sites: N109, S16, S143


A wide area of continental shelf at the continental margin covered by shallow seas See Sites: C61


A narrow column of molten magma that is rising in the Earth's mantle (see hot-spot and pluton)


Local column-shaped or mushroom-shaped body of igneous rock intruded into surrounded rock and which cools underground to form rock such as granite. Generally regarded as being smaller than a batholith. See Sites: C34, C38, C58, C59, C100, E38, N16, N53, S141, S144, S146

Plutonic rock

Igneous rock formed by cooling of magma deep within the Earth's crust. A very coarse-grained texture results from slow cooling (e.g., granite, pegmatite, gabbro). See Sites: N16

Point sources

Localized source of contaminants that may enter groundwater such as a landfill (see leachate) or leaks from underground storage tanks.

Polar wandering

The movement of the position of the magnetic north pole over time.


The term for upward buckling of near-surface layers of rock in response to horizontal compressional stresses resulting from movement of the continents over the mantle (see Neotectonics).

Pore space

The open space betwee.g.ains or particles in a rock or sediment. If connected, then fluids and gases can move through the rock (e.g., oil, gas, groundwater) and it is said to be permeable or porous. If unconnected, the material is said to be impervious.


The amount (usually expressed as a percentage) of the volume of a rock or sediment that is composed of pore space.

Porphyritic texture

The name for the texture seen in igneous rocks that have a bimodal distribution in grain size, where large crystals occur in a fine-grained or glassy groundmass.


Industrial term that refers to a family of potassium salts such as potassium chloride.


Long standing term for the time before the Paleozoic era (i.e. Older than 570 million years). Not much used now; the terms Proterozoic (570 to 2500 million years), archean (2500 to 4000 million years) and Hadean (older than 4000 million) are preferred. See Sites: C22, C79, C91, E18, E32, E48, N61, N94, S115, E64, E68, C138, E85


Force per unit area (equivalent to stress). See Sites: C107, C109, C124, C132, E2, E9, E37, E54, N92, N93, S40, W35, S143, S145

Principle of cross-cutting relationships

This states that any geological feature (faults, dikes, plutons, unconformities etc) that cross-cuts other layers must be younger than the strata that is cross-cut.

Principle of original horizontality

This principle states that when sediments are deposited they are deposited horizontally.

Principle of stratigraphic superposition

This principle states that undisturbedsediments are deposited as layers such that the oldest layer occurs at the base, the youngest on top.


Building of sediment masses outward from a basin margin or continental edge by processes such as the construction of delta s.


A small continental mass formed mainly of volcanic rocks that developed very early in Earth's history.


The original parent of a rock subsequently metamorphosed. Often impossible to determine where the grade of metamorphism is very high (e.g. Gneiss).


A positively-charged particle within an atom.


Olde.g.ological term for large crustal block within a continental craton very different from its neighbours. Now explained in terms of terrane accretion during the early history of continents. See Sites: C25, C33, C35, C58, C127, C128, E5, E14, E13, N8, N9, N10, N16, N21, N32, N99, N109, N115, S20, S89, W36, W37, E80, S142


A type of volcanic glass that forms during the instantaneous cooling of gas rich lava.


Debris and ash (tephra) produced by a violent volcani.e.uption.

Pyroclastic flow

The avalanching and flow of pyroclastic material and hot gases down the sides of an andesitic volcano. Also called a nuee ardente (a glowing cloud); leaves a deposit called an ignimbrite.


An ultramafic igneous rock composed of large pyroxene mineral crystals such as bronzite, Diopside and Augite.


A metamorphic rock formed by alteration of sandstone and which shows interlocking crystals of quartz. See Sites: E40, E41, E45, N34, N36, N39, N42, S84


Glacial clay of marine origin found i.e.stern Canada noted for its ability to turn from a solid to a liquid when disturbed. See Sites: E30

Radiation-effect methods

Age dating method that measure the amount of radiation a rock or sediment has been exposed to after deposition.

Radioactive decay

The ability of some elements for the nuclei of atom to decay spontaneously and emit alpha, beta and/or gamma rays (see parent, Daughter atoms).

Radioactive isotope

An isotope that undergoes radioactive decay.


The radioactive isotope of carbon (carbon 14) which is formed in the atmosphere.

Radiogenic heat

The heat generated from radioactive decay deep within the interior of the planet (see geothermal gradient)

Radioisotope methods

Dating method that uses radioactive isotopes and their half-life to determine ages of material.

Radiometric age dating

See radioisotope methods used to determine absolute age of rock (e.g., this rock is 55 million years old). Contrast with relative dating where it is only possible to state that this rock is older/younger than that one.


The downward movement of rainwater or snowmelt through sediment or rock to replenish groundwater. See Sites: E64


The reorganization of elements to form new or larger crystals within a rock that has undergone changes in pressure and/or temperature.


A mound or pinnacle like seafloor structure built by organisms and composed of shells and coral. Also called a bioherm. See Sites: C22, C36, N77, S4, S42, W25, W29, W34


Synonym for seismic-reflection


A poorly developed ofte.g.anular soil foundin areas where sediment is still being created and deposited. As soils age they develop distinct stratification (called horizons) and higher clay contents produced by chemical processes.


The withdrawal of the sea from the land as a result of a fall in sea level. Opposite ofTransgression.

Relative age

The age of a rock or event as compared to another rock or event.

Relative dating

Dating determined from looking at a sequence of events or rocks in a chronological order; based on principles of superposition, original horizontally, faunal succession and crosscutting.


The vertical difference (in metres or feet) between the highest and lowest parts of an area. See Sites: C63, C92, C129, N33

Reverse fault

A fault in which the hanging wall has moved upwards relative to the foot wall. Indicates rock has been under compression. Also known as a thrust fault and typical of fold and thrust belt..


A fine-grained igneous rock of felsic composition; found around volcanoes above subduction zones.


A crack in the earth's surface resulting from the crust being stretched (see graben, aulacogen) See Sites: C48, E8, E21, E28, N4, N5, N6, N48, N64, N68, N81, N82, N84, N86, N103, N104, N107, S3, S16, W22, C138

Right lateral

Where the opposing block of a fault moves to the right of an observer looking across the fault. Typical of many of the strike slip faults of British columbia.

Ripple cross-lamination

Sedimentary structure in sandstone produced by migration of ripples on a seafloor or bed of a river or desert sand dunes.

Rock cycle

Refers to rocks being formed, weathered, eroded and reformed by the operation of geological processes within and on the Earth's surface.

Rock forming minerals

The most commonly occurring minerals that make up the bulk of the Earth's crust such asFeldspar, quartz, olivine, pyroxene, amphibole, mica, Calcite, dolomite, halite, gypsum and the clay minerals.


The large supercontinent that existed between about 1100 and 750 million years ago. See Sites: C37, C92, C127, E21, E28

S wave

Seismic wave energy propagated in the form of alternating sideways movements (shearing motion). Because shearing creates a change in shape of the material s waves cannot pass through liquid and thus cannot travel through the Earth's core. See Sites: S25

Salt dome

Dome formed from the upward movement of a large body of salt under the load of overlying rock (also called a salt diapir).


Sediment composed or fragments ranging in size from 0. 06 to 2mm. See Sites: C6, C7, C14, C15, C20, C26, C29, C30, C35, C36, C40, C41, C61, C72, C81, C88, C97, C101, C102, C104, C106, C135, E15, E13, E17, E18, E40, E41, E43, E45, E46, E48, E62, N30, N32, N47, N69, N89, N96, S5, S7, S20, S24, S30, S39, S44, S46, S51, S52, S53, S57, S58, S59, S80, S82, S85, S87, S88, S90, S107, S121, S123, S134, S137, W1, W9, W35, W46, E65, E69, C142, C144, C147, S142

Sand dunes

Inear ridge of sand being moved by wind or water; results in a sedimentary structure called cross-bedding. See Sites: C101, E40, E45, E48, W9


Sedimentary rock that is composed mostly of sand-size.g.ains cemented together. See Sites: C35, C40, E15, E18, E40, E41, E45, E48, N32, N47, S20, S30, S51, S52, S53, S57, S58, S59, S80, S82, S85, S87, S88, S90, S121, S123, S137


Refers to erosion of soft sediment layers at the base of a cliff or escarpment. This causes the overlying layers to collapse.


Clay-rich layer of chemically-weathered bedrock resting on intact rock below.


Medium-grained metamorphic rock with a strong schistosity created by sheets of mica.


The platy structure seen in some metamorphic rocks created by the formation of sheet-like minerals.


The accumulation of rock debris at the bottom of a slope or cliff (also called scree).

Sea-floor spreading

The continuous addition of new oceanic crust by igneous activity at mid-ocean ridges. In this way, old crust is pushed away from the ridge.


Flat-topped underwater mountain on the ocean floor. They originate as tall volcanoes that became extinct, were eroded by waves to form atolls. With time they slowly sink below sea level as underlying oceanic crust ages and becomes more dense. Named after Arnold Guyot a nineteenth-century geologist.


Loose particles and fragments of rocks such as sand or gravel produced by weathering. Can be transported by wind, water and ice to form sedimentary rocks. See Sites: C28, C31, C40, C41, C45, C47, C48, C56, C59, C87, C105, C112, C122, C127, E1, E6, E7, E9, E14, E15, E18, E30, E32, E36, E39, E40, E42, E48, E53, N8, N9, N10, N16, N17, N18, N27, N33, N35, N48, N53, N60, N66, N67, N69, N83, N87, N94, N96, N109, N113, N115, N117, S3, S4, S5, S6, S7, S9, S13, S15, S17, S23, S72, S95, S134, W15, W36, W45, E64, E69, C138, C140, C143, C144, C147, S142, S147

Sediment gravity flow

The general term for mass movement of large volumes of wet sediment under the influence of gravity. Debris flows and turbidity currents are the most common types of flow.

Sedimentary basin

Usually a topographic depression in the Earth's crust onland or offshore where thick sediments accumulate. The plate tectonic setting controls the size, shape and depth of the basin. Rift basins are those created where tectonic plates breakup and start from narrow steep sided basins to major oceans. Very deep 'forearc' basins are found in subduction zones, very broad normally shallow 'foreland' basins occur inland of major mountains where the bulk of the thickened crust making up the mountains depresses the surrounding crust.

Sedimentary rock

A rock formed either from lithification of sediment, such as sandstone, precipitation from water (such as rock salt) or consolidation of plant or animal material (such as coal). See Sites: C45, C56, C112, C127, E6, E7, E9, E14, E15, E18, E32, E36, E40, E42, E48, N16, N17, N18, N27, N33, N48, N53, N60, N66, N67, N87, N94, N96, N109, S147


Short lived episode of high water and accompanying flooding that occurs on the downwind side of a large lake.

Seismic reflection survey

A geophysical method where artificially created energy is released at surface. The energy returns to the surface after reflecting from layers of rock or sediment below the ground surface. Returning waves are recorded on an instrument called an exploration seismograph that depicts strata at depth.

Seismic stratigraphy

The documentation and description of strata based on seismic-reflection data.

Seismic wave

Waves of energy produced naturally by an earthquake or artificially by an explosion or other device.


An instrument designed to detect seismic waves and earth motions resulting from earthquakes. Also used to identify buried strata using man-made energy sources (called an exploration seismograph).


A widespread succession of strata bounded at top and bottom by unconformities. See Sites: N48, N93, S60


Name given to rocks or sediments that are deposited during any one epoch. See Sites: C30, C127, E32, N17, S32, S40, S41, S55, S120, W36, E64, E80


A rock composed of serpentine minerals once found on the ocean floor of plate boundaries.


Refers to extensive alteration of ocean floor basalts by hot waters (see hydrothermal).


A fine-grained sedimentary rock derived from mud. See Sites: C31, C56, C73, E6, E7, N32, S4, S19, S21, S24, S29, S52, S53, S57, S58, S61, S62, S110, W7, W8, W23, W24, W27, W28, W43, E64

Shear zones

Deeply buried strata that has been stretched and thinned due to the relative movement of toe crustal blocks. Such zones criss-cross the North American craton often marking the intensely faulted boundaries of different geological provinces and terranes. See Sites: N109

Sheet silicate structure

See phylloSilicate.

Sheeted dykes

A near-surface layer of oceanic crust, formed by sea-floor spreading. Repeated injection of basaltic magma as vertical dyke.g.nerates a body of rock entirely composed of vertical and mutually intrusive basalt dykes.


Old archean and Proterozoic rocks exposed over a large area of the inner parts of continents and forming a surface of low relief (see craton). See Sites: C1, C7, C9, C17, C20, C24, C25, C33, C45, C48, C53, C63, C68, C70, C71, C73, C74, C79, C80, C85, C87, C88, C92, C93, C97, C103, C108, C127, C129, C131, E2, E14, E13, E29, E32, E40, E41, E42, E43, E44, E45, E46, E48, E53, E54, N6, N11, N16, N17, N18, N20, N37, N41, N42, N71, N73, N83, N87, N94, N109, N111, S63, S66, S68, S69, S76, S94, S105, S115, S128, S133, S134, S136, E64, E67, E69, E70, C148, S140, S141, S142, S143, S144, S145, E85


Old term for continental crust; from silica and alumina which dominate such rocks (e.g., granite). See sima. See Sites: S65

Side-scan sonar

Geophysical instrument towed behind boat for mapping the floors of lakes and seas.


Elements that dissolve in molten iron.


Very common mineral formed by bonding of silicon and oxygen atoms (synonymous with quartz). See Sites: C59, E47, N114, N119

Silica tetrahedron

The basic building block of silicate minerals. Four oxygen and one silicon atom are arranged with the silicon in the middle with oxygen around it.


Minerals that are built of silica tetrahedron in different arrangements. See Sites: C59


A sheet-like igneous intrusion; see also dike. See Sites: E34, N5, N60, N61, N64, N97


Sediment composed of particles with a diameter between 0. 004 and 0. 06 mm. See Sites: C40, C94, N117, C140, C144


A clastic sedimentary rock whose grain sizes are inbetween sandstones and Claystones. Contains more quartz than clay compared to shale. See Sites: C40


An old term for oceanic crust formed at Mid-ocean ridges; from silica and magnesia the dominant component of such rocks e.g., basalt. See sial.


Where one crustal block moves along a fault to the left of an opposing block (see dextral).


A crater-like depression created from the collapse of underground caves formed where water has dissolved rock such as limestone. See Sites: W14


Old Swedish mining term referring to mineral deposit (rich in iron, sulphides) formed where igneous rocks come into contact with carbonate rich sedimentary rocks such as limestones.

Slab pull

Force created by sinking of cold dense oceanic crust at a subduction zone.

Slab push

Force created by the intrusion of dikes at a mid-ocean spreading centre and which results in oceanic crust being pushed away from the centre.


A fine-grained metamorphic rock which easily splits along flat parallel planes. See Sites: N90


Fine scratches and ridges found on the surface of a fault and created by intense friction during faulting (see fault gouge)


Surface layer produced from the disintegration and weathering of rock or sediment. Usually rich in organic material and shows an internal structure composed of distinct layers called horizons. See Sites: C24, C48, C61, C70, C91, C98, C122, E39, E53, N73, S19, S39, S52, C146

Sole markings

Scratches, grooves, and erosional pits (flute marks) caused by the passage of a sediment-laden current across a soft mud bed. They are useful paleocurrent indicators.


Acronym (sound, navigation, ranging) describing use of sound energy to map sediments and rocks lying below the floor of seas and lakes.

Source rock

A sedimentary rock that contains sufficient organic matter that can be converted to hydrocarbons (oil, gas) by heating below the Earth's surface.


Elongate beach composed of sand and gravel built out into a bay by sediment being moved by longshore drift. See Sites: C30, E53, N101, S12, S13, S15, S25, S111, S112, S113, W1, W40, W46


A place where groundwater emerges at the Earth's surface to feed surface rivers (see baseflow). See Sites: C102, C128, N73, N107, S48, S120, S136, W4, W5, W6, W39, W46

Stony meteorites

These are composed of silicate minerals and typical of the crustal material of planets. They account for about 60% of known meteorites.

Stony-iron meteorites

Rarely found meteorites composed of mixture of nickel-iron and silicate minerals akin to akin to rocks found in the mantle of planets.


Refers to any change in shape or structure experienced by a rock or sediment in response to an applied force (stress). See Sites: C10, C112, E55

Strain ellipsoid

A graphical device to illustrate rock deformation. The three axes of a three-dimensional ellipsoid figure are scaled to indicate the degree of extension or contraction direction


Plural of stratum, meaning layers of rock. See Sites: C22, C127, S30, S127, E80


The layered structure of sedimentary rock created by deposition of successive beds of sediment. Also found in some igneous rocks where magmatic differentiation has occurred.


The sub discipline of geology concerned with establishing the order and age of rock strata whether igneous, metamorphic or sedimentary in origin. See Sites: C35, N28, S30


The colour produced by a mineral being rubbed across unglazed porcelain which produces a fine powder. Porcelain has a Mohs hardness of about 7. See Sites: C130


A force that acts on a rock or sediment that causes changes in shape and internal structure (strain). Generates folds and faults. See Sites: S3, S18, S61, W22, E68


Scratches and elongate gouges on the surface of a rock formed by debris dragged below a sliding glacier or ice sheet. See Sites: E45, E46, E50, N79, N98, S42, E64, E65, S140


The direction or trend of a geological structure such as a fault or bedding plane where it i.e.posed on the Earth's surface (see dip). Expressed as a bearing with respect to North (e.g., N 60 degrees East or 060o) See Sites: N13, N95, S32

Strike-slip fault

A fault where movement (slip) occurs in a horizontal direction either side of the fault and thus parallel to its strike.


A columnar or dome-like structure created by blue-green algae and made of calcium carbonate. These provide a record of Earth's earliest life occurring in rocks 3. 6 billion years old. See Sites: E22

Structural geology

The sub discipline of geology that deals with the results of deformational processes such as faulting, folding and igneous intrusion and analysis of the stress responsible for deformation.


Downward sliding of oceanic crust under a continent or island arc into the mantle.

Subduction complex

A large body of rocks formed at the contact between the two plates in a subduction zone. Typically consists mainly of deep-water sediments deposited in the trench


A crystal that shows some crystal faces but not all.


Sinking of the land caused by tectonic forces, or by compaction of the underlying rocks due to settling of the grains or removal of groundwater.


Minerals that have (SO4)-2 complexes bonded to cations e.g., the mineral gypsum (Ca SO4).


Minerals that have sulphur atoms bonded to cations e.g., the mineral Galena (PbS) or Lead ore.


A grouping by plate-tectonic activity of several to many of the earth's plates into giant continents (at least as large as present-day Asia). See Sites: C19, C37, C92, C127, N4, N6, N82

Surface wave

Seismic waves that travels outward from the focus of an earthquake by travelling along the surface of the Earth (opposite of body waves).


The contact between two continents joined by plate tectonics. Also refers to the belt of rocks formed at the contact, commonly including ophiolites (verb suturing)


A concave upward fold (opposite of anticline). See Sites: N45


Adjective for a geological process (such as sedimentation) occurring at the same time as tectonic deformation and tectonic activity.


Rocks or sediments deposited during any one period of geologic time. See Sites: C24, C28, C30, C78, C88, C93, C101, E25, E32, E58, N4, N5, N73, S1, S114, S130, W14, W15, W20, W21, W45


The accumulation of rock debris at the bottom of a slope or cliff (also called scree).


The study of motion and deformation of rocks that operate on a regional to global scale as a result of plate tectonic processes. See Sites: N109, S16, S143


A silicate mineral in which all the silica tetrahedron are bonded to one another in a complex three-dimensional framework.


Volcanic ash.


Term used to describe areas of the Earth's surface that have distinct topographic features, such as relief or landforms e.g., glaciated terrain. Easily confused with terrane. See Sites: C74, S19, S107


Term used for a region of the Earth's crust having distinct geological characteristics distinct from adjacent terranes. See also province. See Sites: C111, C112, C113, C127, E18, E54, N109

Terrane accretion

The welding together of terranes by plate tectonic processes to form larger landmasses.

Terrane concept

Refers to the idea that continents are the product of far travelled crustal blocks (terranes) having accreted together.


Adjective, meaning "from the land” i.e. Terrigenous sediment.

Thermohaline circulation system

Circulation system of the oceans involving the movement of dense cold and highly saline waters equatorward with returning poleward flows of warm light water. In this way, heat is transferred around the planet.


Refers to degradation of permafrost in Canada's north in response to climate warming or disturbance by man. Usually involves subsidence of the ground surface as ice turns to water with a consequent loss of volume.

Thin-skinned tectonics

Deformation confined to the upper, brittle layers of the earth's crust (down to about 40-50 kilometres).


Refers to very hot, iron-rich basaltic magma produced at mid-oceanridges.


A term used for poorly-sorted, concrete-like mixture of clay, silt, sand and gravel, often with large boulders; deposited by glaciers or ice sheets. See Sites: C10, C11, C15, C16, C22, C48, C53, C70, C73, C123, C137, E1, E55, N3, N4, N6, N8, N9, N10, N13, N25, N38, N88, N91, N92, N102, N117, S5, S72, S75, S91, S93, S96, S109, S112, S132, S134, W6, W18, W24, W28, E69, C138, C140, C141, C142, C143, C144, E80, S140


Lithified till (rock) recording ancient ice ages.


Relating to the shape, form and the physical features of the Earth's surface. The term is synonymous with physiography and geomorphology. See Sites: C9, C48, E54, N59, E70


Flat lying beds of gravel and sand deposited by rivers on the upper surface of a delta (see also foreset and bottomset).

Trace fossils

The marks left in soft sediment (and now preserved in Sedimentary rocks) as a result of the movement, digging, feeding etc of organisms (e.g., footprints)

Transform faults

A strike-slip fault cutting and offsetting mid-ocean ridges which allows crustal spreading to take place on the curved surface of the Earth.


The gradual flooding of the land caused by a rise in sea-level. Opposite of regression.


Transcurrent (strike-slip) faulting combined with compression


Transcurrent (strike-slip) faulting combined with extension (tension)


Deep-water trough formed over the downgoing oceanic plate at a subduction zone

Triple junction

A three-armed rift where continental crust begins to break apart. Only two arms will widen leaving one 'failed rift' or aulacogen.

Trough cross-stratification

A variety of cross-bedding produced by the movement of sand in rivers.

True north

The direction to the Earth's rotational axis (i.e.North Pole); contrast with magnetic north.

Trunk river

The largest river within a region, the watershed of which (including tributaries) may encompass much of a mountain belt or an entire inland basin.


A wave produced by abrupt movement of the floors of oceans, seas and lakes resulting from faulting and accompanying earthquake activity.


A consoliation of volcanic ash and glass. See Sites: C39, W10


Describes dirty river, lake or sea water having a high concentration of suspended sediment such as mud. See Sites: C40, N16, N17, N18, N96, N109, N116, N117


A bed of sandstone or conglomerate deposited underwater by a turbidity current. Beds have a characteristic internal structure called a bouma sequence where grain size decreases upward (said to be graded). See Sites: C40, N16, N17, N18, N109, N116, N117

Turbidity current

A turbulent suspension of water and sediment moving downslope under water. Leaves a characteristic sedimentary deposit called a graded bed or turbidite. See Sites: N96, N117


Flat topped volcano found in British columbia resulting from an eruption underneath a cover of glacial ice.


Refers to plutonic igneous rocks such as gabbro and peridotite that are composed of dark coloured ferromagnesian minerals dominantly Augite and olivine.

Unconfined aquifer

An aquifer that is not overlain with an impermeable bed (i.e. An aquitard).


An erosional surface within rock strata recording non-deposition and erosion of underlying strata. Where underlying strata are tilted and deformed marking tectonic activity and uplift it is referred to as an angular unconformity (contrast with disconformity). Fossil soils (Paleosols) are common on unconformities because they are essentially fossil landscapes preserved below younger rocks. See Sites: C38, C56, C57, E10, E14, E13, E18, E40, E41, E42, E48


The general principle that assumes that Earth history can be interpreted using modern day geological processes. 'The present is the key to the past' (see catastrophism)

Valley glacier

A glacier that is confined by a valley in a mountainous area.


Refers to a distinct layer of sediment in a lake (or sea) recording deposition in summer and the following winter. Those in lakes dammed by glaciers (glaciolacustrine varves) are common deposits in Canada and consist of a couplet of a light summer layer composed of silt and a dark winter layer composed of mud deposited when the lake surface was frozen.


Narrow fractures in a rock that are typically filled with minerals (e.g., quartz) See Sites: C38, C109, C110, C133, E5, N14, N16, N19


The ability of a material to flow. Rocks have a viscosity as they can deform under heat and pressure. The term is commonly applied to magmas at the Earth's surface and used to distinguish stiff, highly viscous magmas containing silica, from the highly fluid basaltic magmas typical of shield volcanoes.


Acronym for volcanogenic massive sulphides. These are rich deposits of Copper, Silver, Lead and Gold formed by hot waters circulating through rocks formed at mid ocean ridges.

Volcanic glass

Glassy rock created from very quick cooling of magma (see obsidian).


A small unfilled cavity in a rock usually dolostone. These are created when limestone is transformed to dolostone during diagenesis.


The total area drained by a stream and its tributaries; also known as a watershed. Divides separate one drainage basin from another. See Sites: C29, C83, N75, S100


The upper surface of the saturated zone below the ground surface.


The process by which rocks are broken down by chemical and physical means. See Sites: C106, C108, E3, S94

Well head protection

Refers to the practice of protecting groundwater by restricting land use within the recharge areas of aquifers.

Wilson cycle

The term used in honour of the Toronto geophysicist J. Tuzo Wilson, for the repeated cyclic occurrence of supercontinent formation and breakup that has characterised much of Earth's history.


A fragment of rock distinct from the igneous rock the encloses it. Fragments of country rock are commonly incorporated into igneous intrusions such as in sills, dikes or plutons.