|(from Geology and Geological Features: Examples from
Newfoundland and Labrador - A Photographic Slide Collection compiled by
B.F. Kean, 1993)
adit - A nearly horizonal tunnel for entering a mine from the
algae - A varied group of plants that generally live in the sea
or in fresh water; modern examples are pond scum and seaweed.
amphibole - An important group of silicate minerals containing
iron, magnesium and calcium.
andesite - A dark-coloured, fine-grained, volcanic rock composed
of feldspar and biotite, hornblende or pyroxene; the name is derived
from the Andes Mountains; it is the volcanic equivalent of diorite.
anorthosite - A coarse-grained igneous intrusive rock consisting
mainly of calcium-rich feldspar, known as labradorite.
anticline - (see antiform)
antiform - A fold in which the limbs dip away from the axis of
the fold. If the oldest rocks are in the central core, it is called an
aphanitic - Refers to grain size in an igneous rock in which the
crystals are not distinguishable by the unaided eye.
archeocyathid - A simple, reef-building, marine organism that
lived during the Cambrian period of geological time (i.e., 500-600
million years ago).
asbestos - A white to green, fibrous form of the mineral
serpentine which is used widely in fire-retardant and heat- resistant
applications; can be hazardous to one's health if dust is inhaled over
a period of time.
augen - Eye-shaped mineral grains in a mylonite schist or gneiss;
German for eye.
barachois - (see barasway)
barasway - A body of water separated from the sea by a bar or
ridge of sand, gravel, etc., built up by waves and currents. Also known
as a lagoon.
barite - A white, heavy mineral, the main ore of barium, used in
paints, drilling muds and TV screens.
basalt - A dark-coloured, fine-grained volcanic rock composed of
feldspar, pyroxene and sometimes olivine; it is the volcanic equivalent
of diabase and gabbro.
batholith - A very large body of intrusive rock, usually granite.
baymouth bar - A narrow, usually submerged, ridge of sand and
gravel deposited across the mouth of a bay. Commonly formed by the
extension of spits and may connect two headlands, thus straightening
bed, bedding - Layers in sedimentary rocks formed during
deposition and reflecting different compositions or grain sizes in the
original sediment; originally horizontal in most cases (see
bedrock - The continuous, solid rock that underlies soil and
loose sediment everywhere; an exposure of bedrock is called an outcrop.
biotite - The black variety of the mica group of minerals
containing potassium, aluminum, magnesium and iron; it splits easily
into thin, translucent sheets.
boudinage - Layer, such as bed, dyke, etc., that has been pulled
apart into sausage-like pieces.
brachiopod - A type of shelled animal with two unequal shell
halves, which usually lived attached to the seafloor by a stalk.
breccia - A rock consisting of angular fragments in a finer
grained matrix which may or may not be similar to the larger fragments;
it may be formed from any rock type by fracturing (in a fault),
explosion (volcanic), intrusion (intrusion breccia) or sedimentation
calcite - A common, white mineral composed of calcium carbonate,
and the principal constituent of limestone.
carbonate - A general term used to describe a rock composed
mainly of the carbonate minerals, calcite and dolomite.
chalcopyrite - A brassy yellow, metallic mineral composed of
copper, iron and sulphur, and an important source of copper.
chlorite - A dark green, soft, flaky mineral similar to mica; it
is common as an alteration or metamorphic mineral formed from
chilled margins - Edge of dyke or other intrusive body where
magma has cooled quickly in contact with relatively cold wall rock;
crystals close to margin are much smaller than those farther inside the
cirque - A bowl-shaped depression formed at the head of glacial
valleys by frost wedging and ice plucking.
cleavage - The tendency of a mineral or rock to break along a
preferred direction in smooth parallel planes. In metamorphic rocks,
this is also called foliation or schistosity (see schistosity).
columnar jointing - A system of polygonal fractures, resulting
from cooling of molten magma, that splits a rock body into long prisms
or columns. It is characteristic of lava flows and shallow intrusive
conglomerate - A coarse-grained sedimentary rock composed of
rounded fragments which may vary in size from pebbles to boulders.
consolidated - the condition of sediments when they have hardened
into rock from their original, soft state.
contact - The surface separating two different rock types or
coral - A bottom-dwelling, reef-building marine invertebrate
organism of the class Anthozoa. It produces a skeleton of calcium
country rock - The rock intruded by and surrounding an igneous
intrusion (see wall rock).
crag and tail - An elongate hill or ridge resulting from
glaciation, having at the stoss end a steep, often precipitous, face or
knob of ice smoothed bedrock (crag) obstructing the movement of the
glacier and at the lee end a tapering, streamlined, gentle slope (tail)
crinoid - A marine animal related to modern starfish and sea
urchins; it lives attached to the seafloor by a stalk.
cross-bedding - Bedding that was inclined when originally
deposited; it formed by variable current or wave action, or by wind
crystal - Solid material bounded by natural flat surfaces that
result from a regular internal arrangement of atoms; almost all
minerals can form crystals but in most rocks the flat surfaces do not
have room to develop.
delta - A large body of sediment deposited at the mouth of a
diabase - A dark-coloured intrusive rock, found as dykes or
sills, composed of mainly feldspar, pyroxene and/or olivine; it is the
shallow intrusive equivalent of basalt and gabbro.
dimension stone - Natural building stone that may be cut to
specific size requirements. It includes granite, gabbro, anorthosite,
marble, limestone, slate and sandstone. It can be rough or finished
diorite - A grey intrusive igneous rock composed of mostly
feldspar and biotite, pyroxene or amphibole; it forms dykes and small
stocks; it is the intrusive equivalent of andesite.
dip - The angle between the horizontal and a sloping surface
such as a bedding plane; dip is measured perpendicular to strike
dolomite - A creamy-white mineral composed of calcium and
magnesium carbonate and the principal component of dolostone.
dolostone - A sedimentary rock formed by precipitation from
seawater; composed mainly of dolomite (calcium - magnesium carbonate).
dyke - a sheet of intrusive rock that cuts across the
epidote - A greenish-yellow mineral consisting of calcium,
aluminum, iron and silica; it is common in metamorphic rocks,
especially as a coating on joint surfaces.
erosion - The processes that break up or wear down rocks or
unconsolidated sediment and moves them from one place to another; the
forces of erosion include water, ice, wind and gravity.
erratic - A large boulder carried by glacial ice to an area
removed from its point of origin. It is left behind when the ice melts.
esker - A narrow, sinuous ridge of sand and gravel deposited by
a stream flowing under a glacier or ice sheet.
extrusive rock - Rock formed from magma that has erupted
explosively or has flowed onto the earth's surface from a volcano (see
fault - A surface along which one body of rock has moved
relative to another.
feldspar - A common group of rock-forming minerals composed of
silicates of aluminum and one or more of potassium, sodium or calcium.
felsic - An acronym derived from feldspar and silica and used to
describe an igneous rock containing light-coloured minerals, such as
quartz and feldspar; also applied to those minerals. Rhyolite and
granite are felsic rocks. Opposite of mafic.
felsite - A light-coloured, fine-grained extrusive or
shallow-intrusive igneous rock with or without phenocrysts and composed
chiefly of quartz and feldspar.
felsitic - A syn. of aphanitic.
ferromagnesium minerals - A variety of silicate minerals
containing abundant iron and magnesium, e.g., olivine, pyroxene,
amphibole and biotite.
fiord - A glaciated valley flooded by the sea to form a long,
narrow, steep-walled inlet.
flow (volcanic) - Volcanic rock formed from lava that flowed out
onto the earth's surface.
flysch - A thick marine sequence of sedimentary rocks
characterized by thinly interbedded sandy shale, mudstone, sandstone
and conglomerate; flysch is indicative of rapid erosion of a nearby
newly formed mountain belt.
fold - A bend, buckle or flexure in a rock formed by compressive
foliation - In metamorphic rocks, the layering of minerals
caused by oriented growth of mineral grains in response to pressure
formation - A distinctive body of rock that is given a name and
separated from other rocks on a geological map (see Group).
fossil - Remains, traces or imprints of animals or plants that
have been preserved in rocks; includes bones, shells, casts and tracks.
fossiliferous - Containing fossils.
gabbro - Dark-coloured, coarse-grained, intrusive igneous rock
composed of calcium-rich feldspar, pyroxene and sometimes olivine; it
is the deep intrusive equivalent of basalt and diabase.
garnet - A silicate mineral that usually occurs as small,
rounded, red or pink crystals mainly in metamorphic rocks but is rarely
also found in granite veins.
gastropod - Any mollusc belonging to the class Gastropoda
characterized by a distinct head with eyes and tentacles and, in most,
by a single calcareous shell that is closed at the apex, sometimes
spiralled, not chambered, and generally asymmetrical, e.g., a snail.
glacier - A large mass of ice formed by the compaction of snow
that survives from year to year without completely melting; glaciers
vary in size from small valley glaciers to huge ice sheets of
gneiss - A coarse-grained metamorphic rock having banding of
alternate light and dark minerals (gneissosity).
gneissic, gneissose - Pertaining to features of a gneiss.
Gondwana - The ancient continental landmass, comprising the
present South America, Africa, India, Australia and Antarctica, that
split apart during Mesozoic time.
gossan - An iron-rich, rusty-coloured, weathering product formed
over rocks commonly containing sulphide minerals, in particular iron
graded bedding - A type of bedding in which each layer is
characterized by a progressive decrease in grain size from the bottom
to the top of the bed.
grain - Particles or discrete crystals which comprise a rock or
grain size - Size of the particles or crystals that constitute a
rock or sediment; hence fine-, medium-, or coarse-grained.
granite - Light-coloured, coarse-grained felsic igneous intrusive
rock composed of quartz, feldspar and ferromagnesium minerals such as
mica and hornblende; it is the intrusive equivalent of rhyolite.
graptolite - An extinct animal, the fossil remains of which look
like tiny, serrated black rods.
group - In geologic mapping, a unit that consists of two or more
gypsum - A soft, white mineral consisting mainly of calcium
sulphate, formed during the evaporation of sea water; it is used in the
manufacture of plaster of paris and wallboard.
hanging valley - In a glaciated landscape, a tributary valley
whose mouth is in the steep wall of the main valley high above its
hematite - A grey, metallic or earthy iron oxide mineral, which
powders to a red colour; the principal ore of iron; specular hematite
is a shiny, hard variety of the mineral and is used for jewellery as
"Alaska Black Diamond".
hornblende - A black or dark-green mineral that forms
needle-shaped or fibrous crystals; it is the most common member of the
amphibole group and occurs in both igneous and metamorphic rocks.
igneous rock - Rock that has crystallized from molten material,
known as magma.
intrusion - A mass of igneous rock that, while it was liquid,
intruded into older rock, then solidified.
intrusion breccia - A rock composed of angular pieces of country
rock in a matrix of intrusive igneous rock.
intrusive rock - Igneous rock that forms intrusions; as opposed
to volcanic or extrusive rock which is erupted from a volcano.
joint - A crack in a rock along which there has been no relative
Laurasia - The ancient continent that split apart in Mesozoic
time to form Europe, Asia, North America and Greenland.
Laurentia - The ancient North American continent that lay on the
west side of the Iapetus (or proto-Atlantic) Ocean in Cambrian time,
500 million years ago.
lava - Liquid rock that comes out of a volcano and is extruded
onto the earth's surface; also refers to the same material that has
solidified by cooling.
limestone - A sedimentary rock type composed of mostly calcium
carbonate, that formed by chemical precipitation from sea water or by
accumulation of fossils with carbonate shells.
mafic (mineral) - A dark-coloured silicate mineral rich in iron
and/or magnesium; ferromagnesium minerals, include olivine, pyroxene,
amphibole and biotite. It is the opposite of silicic or felsic.
mafic (rock) - An igneous rock that is dark in colour containing
more than 50 percent ferromagnesium minerals such as amphibole,
pyroxene and olivine (e.g., basalt, gabbro).
magma - Liquid from which all igneous rock crystallizes, either
as volcanic rock or intrusive rock.
magma chamber - A space within the earth occupied by molten rock
magnesite - A white mineral composed of magnesium carbonate and
an important source of magnesium; magnesite is a common alteration
mineral in ultramafic rocks.
magnetite - A black, magnetic, iron oxide mineral, and an
important source of iron.
mantle - The part of the earth's interior between the crust and
the core; composed mainly of ultramafic rocks.
marble - A metamorphic rock type formed by metamorphosism of
limestone or dolostone.
matrix - The finer grained rock material filling the spaces
between larger particles or crystals in a rock.
meander - A broad, looping bend in a river.
metamorphic rock - A rock converted from pre-existing rock in
the earth's crust by changes in temperature and pressure or by chemical
action of fluids.
mica - A group of silicate minerals that cleave perfectly into
thin sheets (see biotite, muscovite).
migmatite - A mixture of igneous and metamorphic rocks in which
thin dykes and stringers of granitic material interfinger with
mine - Underground excavation and workings for the purpose of
mineral - A naturally occurring substance that has a fixed
chemical composition and a characteristic crystal form.
moraine - A mound or ridge of debris left by melting glaciers,
composed of a mixture of rock fragments, gravel, sand and clay.
mud crack - A crack formed in a layer of mud or silt resulting
from the contraction that accompanies drying; they are generally
muscovite - A light-coloured variety of the mica group of
minerals containing potassium and aluminum; muscovite splits easily
into thin transparent sheets.
mylonite - A fine-grained metamorphic rock formed by extreme
crushing and pulverizing along a fault zone.
oceanic crust - That part of the earth's crust that underlies
the main ocean basins; it is composed of mafic igneous rocks covered by
a thin veneer of sediments and is continually renewed at mid-ocean
ridges and consumed at subduction zones (see ophiolite).
olivine - A green, iron-magnesium silicate mineral found
particularly in basalt, gabbro and ultramafic rock: gem varieties are
known as peridot.
ophiolite - A group of rocks originally formed as oceanic crust,
consisting of ultramafic rock, gabbro, diabase, basalt and deep-sea
ore - The naturally occurring materials from which minerals of
economic value can be profitably extracted; also the mineral(s) thus
orogeny - A major period of mountain-building.
outcrop - An exposure of bedrock.
oxbow lake - A lake formed in the channel of an abandoned
meander, i.e., the river forms a new channel, isolating the bend or
pegmatite - A very coarse-grained igneous rock type, usually
found as dykes or veins, and commonly composed of quartz, feldspar and
peridotite - Dark-coloured, igneous rock, composed of mainly
olivine and pyroxene (see serpentinite).
perched boulder - A large block of rock that has been left by
melting ice in a prominent and relatively precarious position.
pillow lava - Rounded masses of volcanic rock, usually basalt,
that have been formed by rapid cooling of lava under water.
plate tectonics - The theory that the earth's crust is composed
of a number of individual plates that move in response to convection in
the upper mantle. Margins of plates are sites of considerable geologic
activity. Plate tectonics explains how continents drift and oceans open
porphyritic - A texture in igneous rocks in which some crystals
are distinctly larger than others.
porphyroblast - Large grains or crystals, commonly perfectly
shaped, developed in schists during metamorphism.
porphyry - An igneous rock which has porphyritic texture.
plutonic rock - Igneous rock formed deep beneath the Earth's
surface. These rocks generally cooled slowly therefore their crystals
are large, i.e., coarse-grained.
pyrite - A metallic, pale yellow, cubic mineral composed of iron
and sulphur, commonly known as "fool's gold".
pyroclastic - Pertaining to fragmental material formed by
pyroxene - A common, dark-coloured, silicate mineral which
contains iron and magnesium and is a common constituent of gabbro,
anorthosite and some ultramafic rocks.
quarry - An open pit from which rock such as slate, limestone or
building stone is extracted.
quartz - An important rock-forming mineral that is glassy, white
and relatively hard; it consists of silicon and oxygen.
quartzite - A white or brownish metamorphic rock consisting
mainly of quartz, and formed by the metamorphism of quartz-rich
raised beach - An ancient beach that is located above the
present shoreline; it indicates that sea level has fallen and/or land
reef - A ridge of rocks, sand or gravel that stands above the
level of the sea floor and reaches to the surface; many modern reefs
consist of the hard skeletons of corals and fossil reefs have been
formed by corals, archeocyathids and algae.
rhyolite - A generally light-coloured volcanic rock, high in
quartz content; rhyolite is the extrusive equivalent of granite.
ripple marks - Small ridges produced on a surface of sand or mud
by the movement of wind or water.
roìche moutonneÇe - A knob of bedrock that has been striated and
rounded by glaciers, with a gentle slope facing the up-ice direction.
sandstone - A sedimentary rock composed of sand-sized particles.
schist - A medium- or coarse-grained metamorphic rock that is
rich in mica or chlorite, and has a strong foliation, allowing it to
split easily in one direction.
schistosity - The type of foliation that characterizes schist,
resulting from the parallel arrangement of coarse-grained platy
minerals, such as mica, chlorite and talc.
scree slope - A steep slope consisting of loose, broken rock
fragments. Also called talus slope.
sediment - Unconsolidated material such as gravel, sand or mud
that is transported and deposited by wind, water, ice or gravity.
sedimentary rock - Rock formed by accumulation and cementing of
loose sediment (e.g., sandstone), the deposition of chemical compounds
held in solution in water (e.g., limestone), or by the accumulation of
animal or plant debris (e.g., coal).
serpentine - A greenish metamorphic mineral characterized by long,
waxy or fibrous crystals; asbestos is one form of serpentine; usually
associated with ultramafic rocks.
shale - A fine-grained, layered sedimentary rock formed from mud
sichelwannen - Curved grooves on rock surfaces formed by water
that was under immense pressure at the base of a glacier.
silicate - A silica-rich igneous rock or magma, e.g., granite
sill - A sheet of igneous rock that has intruded along the
layering of sedimentary or metamorphic rock.
silt - Unconsolidated sediment that contains particles larger
than those in clay but smaller than those in sand.
siltstone - A fine-grained sedimentary rock composed mostly of
slate - A fine-grained, metamorphic rock formed from shale, that
has excellent cleavage; it tends to split easily into thin layers, and
is used for roofing and floors (see cleavage).
specular hematite (or specularite) - A type of hematite (iron
oxide) that is very hard, has a metallic lustre and is known as "Alaska
Black Diamond", used for jewellery.
sphalerite - A mineral composed of zinc, sulphur and some iron
and the main source of zinc; colour ranges from yellow to black ("black
jack") as iron content increases.
spit - A sandy bar projecting from the mainland into open water.
Spits are formed by deposition of sediment moved by longshore currents.
stack - A pillar-shaped body of rock close to the shoreline that has
been separated from the land by the erosion of intervening rocks.
staurolite - A brown, iron-rich silicate mineral that tends to form
cross-shaped crystals; it is found in metamorphic rocks.
stock - A small, roughly circular intrusion of igneous rock, usually
less than 100 square km.
stoss and lee - An arrangement of small hills or prominent rocks in
glaciated terrain having gentle slopes on the stoss side and somewhat steeper,
pitched slopes on the lee side, the reverse direction of crag and tail.
stratified - Layered or bedded; refers to sedimentary rock.
striations - Scratches formed on a rock surface by rock fragments
frozen into the bottom of a moving glacier.
strike - The direction of a horizontal line on a plane (e.g.,
bedding, cleavage or fault plane); strike is perpendicular to dip
direction (see dip).
stromatolite - A generally domal- shaped, laminated, calcareous
sedimentary structure, formed in a shallow-water environment under the
influence of a mat or assemblage of sediment-binding blue-green algae
that trap fine, silty detritus and precipitate calcium carbonate and
that commonly develop colonies.
syenite - An intrusive igneous rock consisting of mostly
feldspar, with a little hornblende or biotite.
syncline - (see synform)
synform - A fold in which the limbs dip toward the axis of the
fold. If the youngest rocks are in the central core of the fold, it is
called a syncline
talus slope - See scree slope.
terrace - A level surface part of the way up a slope, and often
made by waves or a flowing stream.
till - Unsorted (all sizes of particles mixed together) and
unstratified loose material deposited by a glacier.
tillite - A rock formed by consolidation of glacial till.
tourmaline - A silicate mineral that contains boron and usually
occurs as long, black, three-sided, striated crystals; tourmaline is
common in granite pegmatite veins and some metamorphic rocks.
trilobite - An extinct marine animal found as fossil remains
that is distantly related to crabs and lobsters; they had a segmented
exterior skeleton that was divided into 3 main parts - head, body and
tail, and which was shed periodically as the animal grew.
tuff - A fine-grained rock composed of volcanic ash.
ultramafic rock - An igneous rock composed of mainly olivine and
pyroxene; it forms an important part of oceanic crust.
unconformity - A discontinuity in the succession of rocks, which
represents a gap in time and deposition. A surface separating younger
rocks from much older rocks.
vein - A thin, sheet-like body of igneous rock or of minerals
such as quartz, calcite, barite, etc., deposited in a crevice or
fracture in a rock.
vesicle - A small round hole formed in volcanic rock by a gas
bubble trapped when the rock solidified.
volcanic rock - Igneous rock that solidified on surface following
a volcanic eruption; extrusive rock or lava; generally cools quickly,
therefore is fine grained.
wall rock - The rock enclosing a vein or mineral deposit; the
rock intruded by and surrounding an igneous intrusion (see country rock).
younging direction - A term used to identify the top of a
sedimentary sequence. Moving towards the top of a sedimentary sequence
the material becomes younger or more recently deposited.