Glossary

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

processes related to transportation and deposition of sediments by wind

Sodium-rich plagioclase feldspar.

the texture in a rock composed of very fine non-crystalline material created by organic or chemical activity

A double-chain ferromagnesian silicate mineral (e.g., hornblende).

a foliated metamorphic rock in which the mineral amphibole is an important component

a extrusive (volcanic) rock of intermediate composition

A negatively charged ion.

Calcium-rich plagioclase feldspar.

resulting from the influence of humans

an upward fold where the beds are known not to be overturned

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

a sandstone with less than 15% clay/silt matrix

a sandstone with more than 10% feldspar and more feldspar than lithic fragments

a sandstone with less than 15% clay/silt matrix, and with >10% feldspar clasts and more feldspar clasts than lithic clasts

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

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

the orientation of a sloping geological feature, such as a bedding plane or fracture

a plane that can be traced through all of the hinge lines of a fold

The direction, measured in degrees (000° to 360°) away from magnetic north (000°).

the zone of shallow water on the shore-side of a reef

the typical level of an element in average rocks or sediments

the water level of stream when it is in flood and just about to flow over its banks

a mafic extrusive (volcanic) rock

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

a layer with geographic information that serves as a background, provides context for additional layers or data plotted on the map

an irregular body of intrusive igneous rock that has an exposed surface of at least 100 km2

The smallest formal lithostratigraphic unit of sedimentary rocks.

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

repeated layering in a sedimentary rock

the texture in a rock formed from the accumulation of fragmented remains of living organisms, most commonly shell fragments

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

a cubic or rectangular model used for study purposes to display geology in three-dimensions

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

a sediment clast with a diameter of at least 256 millimetres

the scheme that defines the typical order of crystallization of minerals from magma

a stream pattern which is characterized by abundant sediment and numerous intertwining channels around bars

a sedimentary- or volcanic-rock texture characterized by angular clasts

A mineral in which the anion group is CO3−2

the four main points of a compass: north, south, east, and west

standard elements on a map that help the reader understand what is being presented and how it relates to places and distances in the real world

A positively charged ion.

Crystals, commonly calcite, quartz, or hematite, formed between grains in a clastic sedimentary rock during lithification. Without cementation, a sedimentary rock is merely a deposit of loose, unconsolidated sediment.

the process during lithification by which minerals are precipitated between grains in sediments such that the grains are glued together

The most recent of the eras, representing the past 65.5 Ma of geological time.

a type of soft white limestone formed from the skeletal remains of sea creatures

a sedimentary rock comprised of material that was transported as ions in solution

a microcrystalline chemical sedimentary rock formed almost entirely of silica

A ferromagnesian sheet silicate mineral, typically present as fine crystals and forming from the low-temperature metamorphism of mafic rock.

a sedimentary fragment of mineral or rock

a rock texture consisting of grains of pre-existing geologic material cemented together

a sedimentary rock comprised of material that was transported as clasts or fragments

sediment particle that is less than 1/256 millimetres in diameter

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

a sedimentary rock comprised mostly of clay-sized grains

The tendency for a mineral to break along smooth planes that are predetermined by its lattice structure.

sediment particle that is between 64 and 256 millimetres in diameter

stress that tends to squeeze something together

a product of ore processing that includes a specific ore mineral, separated from the rest of the rock

a type of fracture distinguished by smooth, curved mineral surfaces resembling broken glass

a sedimentary rock that is comprised predominantly of rounded grains that are larger than 2 mm

the surface that represents the boundary between two different bodies of rock.

metamorphism that takes place adjacent to a source of heat, such as a body of magma

A chain of volcanoes formed on the upper plate at a ocean-continent convergent boundary. Volcanoes are built on continental crust.

The relatively thick and buoyant outermost layer of Earth's internal structure composed of predominantly intermediate to felsic igneous rocks, as well as sedimentary and metamorphic rocks.

the concept that tectonic plates can move across the surface of the Earth

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

the difference in elevation between two adjacent topographic contour lines

imaginary lines on Earth's surface that connect points of equal elevation

a plate boundary at which the two plates are moving towards each other

A set of numbers referring to a grid system used to specify an exact location on Earth.

a weak, poorly-cemented type of limestone consisting almost entirely of shells and shell fragments

The metallic interior part of the Earth, extending from a depth of 2900 kilometres to the centre.

A bond between two atoms in which electrons are shared.

small-scale inclined bedding within larger horizontal beds

The uppermost layer of the Earth, ranging in thickness from about 5 kilometres (in the oceans) to over 50 kilometres (on the continents).

a rock composed of interlocking crystals

A steep stream bank on the outside of a meander formed by erosion.

an assumed surface used as a reference for the measurement of elevations and depths

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

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

In geology, deformation refers to folding (ductile bending) or faulting and fracturing (brittle breaking) of rocks in response to stress.

In the context of the geographic grid system, a distance equal to 60 minutes.

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

photosynthetic algae that make their tests (shells) from silica

an intermediate intrusive igneous rock

the angle below horizontal at which a planar layer of rock (e.g., sedimentary bed), or other planar feature, slopes

direction of maximum dip, the direction water poured onto a dipping plane would flow

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

An ion with a charge or +2 or −2.

a plate boundary at which the two plates are moving towards away from each other

An object with twelve surfaces, such as a garnet crystal.

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

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

a carbonate rock made up primarily of the mineral dolomite

The eastward-measured distance, or x-coordinate, used in the Universal Transverse Mercator (UTM) grid system. Reported in metres.

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

the deformed rock returns to its original shape and size when the deforming stress is removed

Parallel of latitude defined to be 0°.

the action of surface processes (like running water or wind) that remove soil, rock, or dissolved material from one location on or near the Earth's surface, and then transports it to another location.

various different types of minerals and rocks that form when bodies of water evaporate

A situation clearly beyond your control such as an academic conflict, documented illness or family emergency.

Please note that work-related commitments do not qualify as an exceptional circumstance for which accommodation may be sought.

wavy, irregular ‘veiny’ lines that may appear as a slightly different colour than the rest of the feldspar crystal (e.g., paler pink, cloudy more opaque white)

igneous rock that cooled at surface

a boundary in rock or sediment along which displacement has taken place

A very common family of framework silicate minerals.

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

The oxidized form of an ion of iron (Fe3+).

Referring to a silicate mineral that contains iron and or magnesium.

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

a low-lying area adjacent to a river, formed mainly of river sediments and subject to flooding.

the smallest formal lithostratigraphic unit of volcanic rocks. A discrete volcanic rock body distinguishable by texture, composition, order of superposition, paleomagnetism, or other objective criteria.

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

the texture of a metamorphic rock with a foliation

the lower surface of a non-vertical fault

a single-celled protist with a shell that is typically made of CaCO3

the zone on the ocean side of a reef

A body of rock identified by lithic characteristics and stratigraphic position; it is prevailingly but not necessarily tabular and is mappable at the Earth’s surface or traceable in the subsurface.

a rock that contains the remains of living organisms (fossils) or evidence of past life (footprints, burrows)

A break within a body of rock in which the rock on either side is not displaced.

a broken surface of a mineral that might be described as irregular, splintery, or conchoidal

the situation where the expansion of freezing water pries rock apart

(Giga annum) billions of years before the present.

a mafic intrusive igneous rock

A grid system used to specify locations on Earth using coordinates of latitude and longitude.

a written description of the timeline of geological processes responsible for the sequence of rocks in an area

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

referring to sediments deposited from a stream that is derived from a glacier

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

high-grade metamorphic rock in which the mineral components are separated into bands

Type of foliation defined by segregation bands of light and dark coloured minerals in a gneiss.

a down-dropped fault block, bounded on either side by normal faults

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

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

A felsic intrusive igneous rock.

a sedimentary particle ranging in size from 2 to 4 millimetres in diameter

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

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

A shortened version of full UTM coordinates for a specific location on Earth's surface.

A system used to divide the Earth's surface into squares using two sets of perpendicular lines for the purpose of specifying locations and navigation.

finer grained, typically aphanitic, crystals surrounding distinctly larger crystals (phenocrysts) in an igneous rock that formed from two-staged cooling

The lithostratigraphic unit next higher in rank to formation; a stratigraphically-continuous series of related formations.

A characteristic crustal form or combination of forms of a mineral.

The first eon of Earth history, extending from 4.57 to 3.80 Ga.

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

NaCl, a halide mineral also known as table salt.

An element in the second-last column of the periodic table that forms anions with a negative-1 charge.

the upper surface of a non-vertical fault

a fine-grained metamorphic rock that is not foliated

an uplifted fault block, bounded on either side by normal faults

the surface area of volcanism and high heat flow above a mantle plume

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

The anion OH− or an mineral that includes that anion.

a rock formed from the cooling of magma

A clay mineral with a composition similar to that of muscovite mica.

specific metamorphic minerals indicative of a particular metamorphic grade or range of pressure and temperature conditions

includes all materials extracted from the Earth except for fuels, metallic ores, water, and gemstones.

an igneous rock that has cooled slowly beneath the surface

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

A bond in which electrons are transferred from one atom to another, thus forming ions.

A chain of volcanoes formed on the upper plate at a ocean-ocean convergent boundary. Volcanoes are built on oceanic crust.

a tight fold in which the limbs are parallel to each other

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

the absolute dating (dating in years) of a geologic material using the decay of radio-isotopes within the material

a fracture in rock

(Kilo annum) thousands of years before the present.

A clay mineral that does not have cations other than Al and Si.

A measurement of the angular distance north or south from the equator of a point on Earth's surface. Coordinates are reported in degrees, minutes, and seconds.

The regular and repeating three-dimensional structure of a mineral.

along a stream, the ridge that naturally forms along the edge of the channel during flood events

in mining, a horizontal mine opening

the layers of rock on either side of a fold

a sedimentary rock that is comprised mostly of calcite

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

the conversion of unconsolidated sediments into rock by compaction and cementation

The rigid outer part of the Earth, including the crust and the mantle down to a depth of about 100 kilometres.

A measurement of the angular distance on Earth's surface east or west from the Prime Meridian in Greenwich, England. Coordinates are reported in degrees, minutes, and seconds.

(Mega annum) millions of years before the present.

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

Molten rock typically dominated by silica.

an instrument used to measure the intensity of a magnetic field

The middle layer of the Earth, dominated by iron and magnesium rich silicate minerals and extending for about 2900 kilometres from the base of the crust to the top of the core.

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

In the context of a geological map, this refers to how a rock unit is drawn on the map, or the way a rock unit looks in map view.

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

the mass failure, by gravity, of rock or unconsolidated material on a slope

the texture of a metamorphic rock that is not foliated

a mud-filled curved scar on the flood plain that marks the former location of an oxbow lake.

the sinuous path taken by a stream within a wide flat flood plain

the physical breakdown of rock into smaller fragments

A formal lithostratigraphic unit next in rank below a formation and is always a part of some formation. It is named as a member within a formation because it possesses characteristics distinguishing it from adjacent parts of the formation.

Imaginary lines that run north-south and are used to measure longitude in the geographic grid system.

The lustre of a mineral into which light does not penetrate but only reflects off of the surface.

a descriptive term for the relative temperature and pressure conditions under which metamorphic rocks form e.g., low grade, intermediate grade or high grade

a rock formed by metamorphic processes that change the composition, texture or both of a preexisting parent rock (protolith)

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

A sheet silicate mineral (e.g., biotite).

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

In the context of the geographic grid system, a distance equal to 60 seconds.

a rock composed of a single mineral

an inclusive term for mudstone, shale and claystone

A potassium-bearing non-ferromagnesian mica.

The system used by Natural Resources Canada for providing general purpose topographic maps of the country.

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

A silicate mineral that does not contain iron or magnesium (e.g., feldsspar).

The lustre of a mineral into which light does penetrate.

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

The northward-measured distance, or y-coordinate, used in the Universal Transverse Mercator (UTM) grid system. Reported in metres.

Volcanic glass formed by quenched lava in which few (if any) crystals form. Has obvious conchoidal fracture.

The relatively thin and dense outermost layer of Earth's internal structure predominantly composed of mafic igneous rocks including gabbro intrusions, sheeted dikes, and pillow basalts. Formed by partial melting of the mantle beneath a spreading centre (ocean-ocean divergent boundary).

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

Spheroidal particles <2 mm in diameter composed of thin concentric layers of calcite or quartz precipitated from a solution around a nucleus. Typically formed in warm, shallow water with strong currents.

a rock containing ooids (spheroidal particles <2 mm in diameter composed of thin concentric layers of calcite or quartz precipitated from a solution around a nucleus)

a mine that is open to the surface

the direction found at the point equally between each cardinal direction: northeast (NE), southeast (SE), southwest (SW), and northwest (NW)

a natural occurrence of rock or sediment that contains enough minerals with economically important elements that can be extracted at a profit

To a geologist, an outcrop is an exposure of bedrock, the solid rock of the crust.

a geological feature that has been tilted to the point where it is upside down

a part of a stream meander that has become isolated from the rest of the stream as the result of a meander cutoff

the reaction between a mineral and oxygen

A mineral in which the anion is oxygen (e.g., hematite Fe2O3).

past variations in the intensity and polarity of the Earth’s magnetic field

Imaginary lines that run east-west and are used to measure latitude in the geographic grid system.

the process during which a only specific mineral components of a rock melt in response to changing conditions

a narrow gap between individual sedimentary layers

a sedimentary particle ranging in size from 2 to 64 millimetres (includes granule)

a rock texture in an igneous rock in which the individual crystals or grains are visible to the naked eye

The most resent eon of geological time, encompassing the Paleozoic, Mesozoic and Cenozoic.

a relatively large crystal within an igneous rock that is distinctly coarser grained than the crystals forming the groundmass

A mineral in which the anion is PO43−

a foliated metamorphic rock and a sheen on the surface produced by aligned micas (phyllitic foliation).

A silicate mineral in which the silica tetrahedra are made up of sheets.

in the form of a plane, meaning a flat or level surface

The deformed rock cannot return to an un-deformed state once the deforming stress is removed. Irreversible strain.

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

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

a body of intrusive igneous rock

Formed on the inside of a meander, where flow velocity is lower, by the deposition of sediment.

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

two or more minerals with the same chemical formula but different crystal structures

an igneous texture in which some of the crystals (called phenocrysts) are distinctly larger than the rest

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

Feldspar with the formula KAlSi3O8.

The line of longitude defined to be 0°. Located in Greenwich, England.

the principle that a body of rock that cuts across or through another body of rock is younger than that other body

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

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

the principle that sedimentary beds are originally deposited in horizontal layers

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

a series of principles used to interpret strata (layers of rocks) and determine the geologic history of a given sequence of rocks

the original, un-metamorphosed parent rock from which a given metamorphic rock is formed

A sub-atomic particle with a mass of 1 and a charge of 1.

a highly vesicular felsic volcanic rock (typically composed mostly of frothy glass fragments)

A single chain silicate mineral.

A silicate mineral with the formula SiO2.

a non-foliated metamorphic rock formed from the contact or regional metamorphism of sandstone

A purely physical process (no change in composition) that occurs in a solid-state during metamorphism. Atoms in a mineral are re-organized and typically grain size increases.

a fold that is overturned such that its limbs are close to horizontal

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

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

the interpretation of a relative order of events applied to a sequence of rocks using the principles of stratigraphy

the amount of variation in elevation and slope in an area

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

A fixed ratio (e.g., 1:50,000) between linear measurements on the map and the corresponding distances on the ground. An R.F. of 1:50,000 implies that 1 cm on the map represents 50,000 cm on the ground.

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

a felsic extrusive (volcanic) rock

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

the series of processes through which rocks are transformed from one type to another

The degree of smoothing of a clast or grain due to abrasion of other sediments. Described by the terms: very angular, angular, sub-angular, sub-rounded, rounded, or well-rounded. Does not imply sphericity.

a general rule for determining dip direction of dipping planar contacts deflected or bent as they cross a valley or stream

a mineral or rock fragment ranging in size from 1/16th to 2 millimetres

A clastic sedimentary rock that is primarily comprised of sand-sized particles.

graphic or visual representation of the scale of a map

A foliated metamorphic rock with visible aligned mica crystals.

Type of foliation defined by scaly layers of visible mica minerals or other platy or elongate minerals. Rocks with this texture appear shiny or sparkly, as the light glints off cleavage planes of the aligned minerals.

Curved ridges on the flood plain surface associated with the growth of a meander bend. Formed by sediment deposited on point bars.

the formation of new oceanic crust by volcanism at a divergent plate boundary

In the context of the geographic grid system, a measurement of distance. Sixty seconds corresponds to one minute.

rock that has formed by the lithification of sediments

unconsolidated particles of mineral or rock

Station containing seismographs, which are instruments used to measure the vibrations produced by earthquakes. Data recorded by a seismograph are used to pinpoint the exact location and depth of an earthquake.

a vertical opening at a mine

a silt- and clay-rich rock that has evidence of layering

the stress placed on a body of rock or sediment adjacent to a fault

A silicate mineral in which the silica tetrahedra are combined within sheets.

A form of the mineral quartz (SiO2).

A combination of 1 silicon atom and 4 oxygen atoms that form a tetrahedron.

A mineral that includes silica tetrahedra.

The 14th element.

A flexible synthetic material made up of Si–O chains with attached organic molecules

sedimentary particles ranging is size from 1/256th to 1/16th of a millimetres

a fine-grained foliated metamorphic rock that splits easily into sheets

Type of foliation defined by closely spaced, flat surfaces along which a slate splits. Formed by the growth of microscopic mica minerals.

A fine-grained sheet silicate mineral that can accept water molecules into interlayer spaces, resulting is swelling.

a refinery at which minerals are processed to produce pure metals

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

describes the distribution or range of grain sizes, either in unconsolidated sediments or in clastic sedimentary rocks

A number representing the ratio of a mineral's weight to the weight of an equal volume of water. A measure that geologist's use to describe the density of a mineral.

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

the flow of groundwater onto the surface

a cone-shaped speleothem that is suspended from the roof of a cave

a cone-shaped speleothem that forms on the floor of a cave

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

the deformation of rock that is subjected to stress

layers of sedimentary, extrusive
igneous, metasedimentary, or metavolcanic rocks

a single layer of sedimentary, extrusive igneous, metasedimentary, or metavolcanic rock

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

The physical boundaries of a stream (or a river), consisting of a bed and stream (or river) banks.

describes the force per unit area that acts on a rock unit to change its shape or volume

a growth pattern that looks like a set of hairline grooves or faint parallel lines, visible on crystal faces of some minerals

the compass direction of a horizontal line on a dipping planar surface (e.g., bedding plane, fracture etc.)

a fault that is characterized by motion that is close to horizontal and parallel to the strike direction of the fault

When part of a plate is forced beneath another plate along a subduction zone.

A mineral in which the anion is SO42−.

A mineral in which the anion is S2a mineral in which the anion is S2-.

a fold in which the limbs are at the same angle to the hinge

a downward fold where the beds are known not to be overturned

the fine-grained waste rock from a plant used to concentrate ore minerals

a sloped deposit of angular rock fragments at the base of a rocky escarpment or cliff

A region of the lithosphere that is considered to be moving across the surface of the Earth as a single unit.

stress that tends to pull something apart

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

a fragment of rock or mineral cut and ground to a thickness of ~0.03 mm, and mounted on a glass slide to be closely examined under a petrographic microscope

a low angle reverse fault

unsorted sediment transported and deposited by glacial ice

a boundary between two plates that are moving horizontally in opposing directions with respect to each other

a boundary between two plates that are moving horizontally with respect to each other in opposing directions

a deposit of calcium carbonate that forms at springs, hot springs or within limestone caves

a form of travertine that is especially porous as it forms around existing vegetative material

a geological boundary representing a period of erosion and/or non-deposition, where a portion of the rock record is missing

A grid system used to specify locations on Earth's surface using easting and northing coordinates measured in metres.

a small open cavity in a volcanic rock, produced by gas bubbles

an igneous texture characterized by holes left by gas bubbles

Magma that has cooled rapidly or quenched, not allowing time for the formation of crystals.

a sandstone with more than 15% clay and silt

a range of processes taking place in the surface environment, through which solid rock is physically broken into smaller fragments and transformed into sediment and ions in solution

a fragment of "foreign rock", typically a fragment of the surrounding rock into which magma is intruding, incorporated into an igneous rock

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