Glossary

a method of determining the numerical age of rocks. Absolute dating uses isotopic measurements to calculate the time elapsed between a rock-forming event and the present.

observational error that indicates how close measurements are to their true value

minerals that fill vesicles

igneous rock term that describes mineral grain shape that is no longer recognizable

a ridge-shaped fold in which the bedding planes slope downward from the hinge with the oldest layers in the center of the fold

igneous rock texture; individual mineral grains are too small and require a microscope to be seen

the plane or surface that divides the fold symmetrically. The axial plane may be vertical, horizontal, or inclined at any angle

direction from one point to another, shown with a degree measurement

a layer of sediment, sedimentary rock, or volcanic rock "bounded" above and below by more or less well-defined bedding surfaces

a type of chemical sedimentary rock that have a biologic component to their origin.

when rocks fail as rigid blocks or solids

binding together of rock particles by cement

sedimentary rock formed by chemical and organic reprecipitation of the dissolved products of chemical weathering.

sedimentary rocks composed of fragments, or clasts, of pre-existing minerals and rock. These are typically the result of physical weathering.

pieces of rock or mineral that are not grown in the rock

cleavage is a type of foliation that forms within fine grained rocks due to deformation and metamorphism

planes of weak chemical bonds that minerals predictably break along

property of an object that is the result of how the object reflects light

exertion of force on something so that it becomes denser

an instrument with a magnetized pointer that shows the direction of magnetic north and bearings from it.

a type of fracture that has a smoothly curving surface of fine-grained materials. Some say this is shell-like. This forms in material which have no planar surfaces of internal weakness or planes of separation (no cleavage). Such a curving fracture surface is characteristic of glass and other brittle materials with no crystal structure.

curved fracturing that resembles broken glass

a line on a map joining points of equal height above or below sea level

a subset of minerals that are considered essential to the manufacturing or technological needs of companies, industries and nations

a side-on view or diagram showing geologic features in a vertical view to illustrate structure and stratigraphy that is hidden underground. Features can include rock units, faults, topography, and more. These often accompany geologic maps, which are an overhead view, which can help to visualize the three-dimensional structure of the region.

the shape that a mineral grows into

rock texture of interlocking grains that grow together

faults which move along a tilted plane

indicates shape change of a material through bending or flowing during which chemical bonds may become broken but subsequently reformed into new bonds

a textural term describing a rock that has mineral grains all approximately the same size

the transport of sediment grains by wind, water, and ice

igneous rock term that describes a mineral grain shape that is well-formed/close to perfect

rock type which cools rapidly on the surface of the Earth

an observation that's been confirmed many times so scientists can accept it as "true." But everything in science has some uncertainty; nothing is ever scientifically "true" beyond a shadow of a doubt.

Felsic is an igneous rock that is rich in light-colored silicate minerals such as feldspar and quartz (silica).

rock texture when minerals align themselves and create a layered appearance

repetitive layering in metamorphic rocks. Each layer can be as thin as a sheet of paper, or over a meter in thickness.

the block of rock that lies on the beneath an inclined fault or a mineral deposit

unitless ratio of map distance to real-world distance; expressed as 1:x, with x being any number that 1 on the map would be equal to on the surface of the Earth (refer to Chapter 2.2)

the unpredictable breakage of a mineral

a type of thematic map that shows the distribution of rock units in an area

an elongated block of the Earth's crust lying between two normal faults that has been displaced downward

line or bar that corresponds to a stated distance

the "background" mineral grains in a porphyritic rock that surround larger grains

the block of rock that lies on the above of an inclined fault or of a mineral deposit.

physical property of minerals that describes a mineral's resistance to scratching

an imaginary line where the limbs of the fold meet. It is also the line of maximum curvature.

an idea or proposition that can be tested by observations or experiments, about the Earth

Intermediate igneous rocks are moderate amounts of silica (52-63 wt.%) and have nearly equal amounts of felsic and mafic minerals.

rock type which cools within the Earth

smaller area, greater detail

molten rock material erupted on the surface of the Earth

laws of science are statements, based on repeated experiments or observations, that describe or predict a range of natural phenomena

the areas on either side of the axial plane that stick out like arms or legs

a complex process in which loose grains of sediment are converted into rock. Lithification may occur when a sediment is deposited or later.

physical characteristics of a rock or stratigraphic unit

physical property that describes how the surface of a mineral reflects light

Mafic rock is silicate mineral or igneous rock rich in magnesium and iron. Mafic minerals include olivine, pyroxene, amphibole and biotite mica.

molten rock material within the Earth

angle between true north and magnetic north

the direction a magnetic compass points, toward the magnetic north pole; located in northern Canada and moves over time due to Earth’s magnetic field)

clastic sedimentary classification, determined by grain shape, rounding, and sorting

a naturally occurring, inorganic, solid that can be defined by a chemical formula and a crystal structure.

the qualitative ranking of minerals based on the "hardness" (or resistance to scratching)

The Government of Canada publishes topographic maps that cover the country, catalogued under the National Topographic System (NTS). These maps have unique names and number-and-letter identifiers (e.g. 63K). Each 1:250000 NTS area is subdivided into 16 1:50000 maps, then numbered from 63K/01 to 63K/16. This way, users can order and describe topographic maps using the codes and names.

when minerals do not have a preferred orientation

a dip-slip fault in which the block above the fault has moved down relative to the block below

sedimentary rock formed by the accumulation and lithification of organic debris, such as leaves, roots, and other plant or animal (shells or skeletal) material.

leaves, roots, and other plant or animal material

rock formations that are visible on the surface, usually in a cliff or man-made exposure along a road

igneous texture; individual grains are visible without a microscope

large mineral grains in a porphyritic rock that is surrounded by smaller grains

two-dimensional representation of the Earth's surface that does not include elevation

the vertical angle between a horizontal plane and the axis of a feature. Plunge is measured along the axis of a fold, whereas dip is measured along the limbs

having minute spaces or holes through which liquid or air may travel

textural term that describes a rock with two distinct grain sizes

a metamorphic term for large euhedral crystals that form within the rock during metamorphism

metamorphic texture for a finer grained rock that has other, significantly larger grains; similar to porphyritic igneous rocks

observational error that indicates how close measurements are to each other.

a rock that existed before it gets metamorphosed, also called parent rock

The texture of pumice; closely spaced, small, sub-parallel holes (tubes) that make up a significant amount of the rock volume. This makes pumice very light.

a method to determine the order of past events by comparing the ages of different geological events

a fault one in which one side of the fault, the hanging wall, moves up and over the other side, the foot wall

the splitting apart of a region into two or more regions separated by normal faults. Also when a tectonic plate is split into two or more tectonic plates separated by divergent plate boundaries

A series of processes which relate rocks in Earth, including igneous intrusion or extrusion, weathering, erosion, transport, deposition as sediment, which lithifies into sedimentary rock, metamorphism, remelting, and leading again to igneous activity

the degree of smoothing from interaction of sedimentary particles.

the number of digits needed to accurately describe a measurement, starting from the first nonzero digit.

larger area, less detail

distribution of grain sizes in sedimentary rocks

the colour of a mineral's powder

a measurement to describe the orientation of a planar geologic feature. Strike is the direction of an imagined horizontal line across the plane. Dip is the angle of the plane measured downward from horizontal.

a fault in which rock strata are moved in a horizontal direction, parallel to the line of the fault

igneous rock term describing a mineral grain shape that is not perfect, but the shape is still recognizable

a fold with a downward arc or curve with the youngest layers in the center of the fold

size, shape, and arrangement (or fabric) of the mineral grains and crystals

maps that show a specific topic

explains known facts and also allows scientists to make predictions of what they should observe

a reverse fault that is at an incline of less than 45 degrees

map showing the arrangement of the natural and artificial physical features of an area

Ultramafic rocks are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals.

a type of geologic contact-a boundary between rocks usually caused by a period of erosion. It can also by a significant pause in sediment deposition

the scale notation on some old maps; phrased as, for example, "one centimeter per kilometer"

holes in rocks caused by gas bubbles in cooling

texture containing vesicles (small circular or tubular holes which represent gases or liquids which were trapped in the magma during cooling)

the process of being worn by exposure to the atmosphere