GLOSSARY OF SURFICIAL GEOLOGY TERMS
Introduction
The following glossary contains terms used in the text of this report, terms commonly used by Quaternary geomorphologists and geologists, and terms used in the British Columbia Terrain Classification System (Howes and Kenk, 1988). Glossary sources are listed in Part I of the Annotated Bibliography.
*Terms peculiar to the BCTCS and non-standard definitions used in the BCTCS are marked by asterisks.
Italics are used to indicate words that are defined elsewhere in this glossary.
Glossary
ABLATION: The processes whereby mass is removed from a glacier; includes melting, evaporation, and calving of icebergs.
ABLATION MORAINE: A moraine resulting, from ablation; typically hummocks of ablation till formed by melting of stagnant ice.
ABLATION TILL: Material accumulated on top of a melting glacier; coarser textured and less consolidated that basal till; common where glacier recession is dominated by downwasting of stagnant ice.
ACTIVE (STATUS)*: A qualifying descriptor (superscript) used to indicate that a material is undergoing deposition at the present time*.
AERIAL PHOTOGRAPH: See air photo.
AGGREGATE: Granular material of mineral composition such as sand, gravel, crushed rock, slag, or similar inert material, used with a cementing medium to form mortar, concrete, and asphalt, or alone as in railroad ballast, etc.. Aggregate is described as gravel or coarse aggregate if it is retained on a 4.76 mm square (no. 4) sieve screen and as sand or fine aggregate if it passes this mesh size.
AIR PHOTO: A photograph of the earth's surface taken from the air. It is usually a vertical view, and one of a series of photos taken from an aircraft flying a systematic pattern at a given altitude in order to obtain continuous photo coverage for mapping purposes.
AIR PHOTO lNTERPRETATION: The identification of specific earth-surface features and conditions by recognition of the patterns displayed on air photographs.
AIR PHOTO MOSAIC: A photographic reproduction of a series of air photos assembled in such a manner that features such as roads and streams match from one photo to the next and there is no overlap or repetition. CONTROLLED MOSAICS are made by locating some points precisely, as on a map, and using prints that have to some extent been corrected for tilt and topographic distortion, whereas UNCONTROLLED MOSAICS, which are less expensive, are made by matching edges from one photo to the next as well as possible; images are distorted and cannot be used for reliable measurements.
ALLUVIAL: See fluvial.
ALLUVIAL FAN: A fan-shaped deposit of fluvial sand and gravel, usually located at the mouth of a tributary valley; a type of floodplain.
ALLUVIUM: Material deposited by a stream; fluvial materials.
ALLUVIAL PLAIN: (i) See floodplain. (ii) A plain underlain by fluvial deposits, including alluvial (fluvial) fans, and lacustrine deposits (stream transported materials that have accumulated in lakes).
ALLUVIAL TERRACE: See river terrace.
ALPINE: (i) Refers to areas above treeline (adjective). (ii) Pertaining to high mountains.
ANASTOMOSING CHANNEL: Applied to stream channels that diverge and converge around many islands. ("Islands" support mature vegetation and their surfaces are relatively high above mean maximum discharge levels.)
ANGULAR FRAGMENTS: Broken rock with sharp edges.
ANTHROPOGENIC MATERlALS*: Earth materials modified by human activities to the extent that their initial physical properties (e.g., structure, cohesion, consolidation) have been drastically altered. Includes spoil heaps and fill*.
ANTHROPOGENIC SITE*: Cultural sites; archaeological sites; historic sites.
ASPECT: The direction toward which a slope is facing; recorded as a compass direction..
AVALANCHE: A large mass of snow and/or ice, sometimes accompanied by rocks and vegetative debris, moving rapidly down slope.
AVALANCHE CONES: Cones of debris deposited by snow avalanches; similar to talus cones but with concave longitudinal profiles and gentler slopes.
AVALANCHE TRACKS: Paths followed by snow avalanches; readily identified below treeline by their characteristic vegetation of deciduous shrubs and young conifers, and bright green colour.
BASAL TILL: Material that accumulates underneath a glacier from basal ice; includes lodgement till and
basal meltout till.
BASE MAP: The map (usually a topographic map) to which terrain mapping is added, either by drafting directly onto the base map, or by drafting onto a transparent overlay which laid over the base map.
BASIC ELEMENT*: The simplest unit of a landscape, consisting of a single type of material formed by a single process and forming a single landform*. (See 4.1.)
BEACH: The gently sloping shore of a body of water that is washed by waves and usually composed of loose sandy or gravelly material.
BED: (i) The ground on which any body of water lies, limited laterally by a bank or shore. (ii) A single layer of sediment or rock, separated from layers above and below by more or less well defined boundary planes.
BEDDING: Collective term signifying the existence of beds or laminae. WELL BEDDED indicates beds are immediately apparent, clearly defined and can be easily traced across the deposit; POORLY BEDDED means beds are only discernible after careful scrutiny, or bedding planes are discontinuous; MODERATELY BEDDED is intermediate between the other two.
BEDROCK: Solid rock, usually older than Quaternary (except rock formed by cooling of lava); either exposed at the land surface or underlying surficial deposits or regolith of varying thickness.