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Glossary
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the area of a glacier where more glacier mass is lost than gained.
ablation hollowsdepressions in the snow surface caused by the sun or warm, gusty wind.
ablation morainemound or layer of moraine in the ablation zone of a glacier; the rock has been plucked from the mountainside by the moving glacier and is melting out on the ice surface.
ablation seasonperiod during which glaciers lose more mass than they gain; usually coincides with summer.
ablation zonearea or zone of a glacier where snow and ice ablation exceed accumulation.
accumulation areaarea of a glacier where more mass is gained than lost.
accumulation seasonperiod during which a glacier gains more mass than it loses; usually coincides with winter.
accumulation zonearea of a glacier where more mass is gained than lost.
advancewhen a mountain glacier's terminus extends farther downvalley than before; glacial advance occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.
alpine glaciera glacier that is confined by surrounding mountain terrain; also called a mountain glacier.
sharp, narrow ridge formed as a result of glacial erosion from both sides.
band ogivesalternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter.
basal slidingthe sliding of a glacier over bedrock.
bergschrundcrevasse that separates flowing ice from stagnant ice at the head of a glacier.
glacier that has one or more tributary glaciers that flow into it; distinguished from a simple valley glacier that has only a single tributary glacier.
a semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a snowdrift glacier or a drift glacier.
chattermarksstriations or marks left on the surface of exposed bedrock caused by the advance and retreat of glacier ice.
bowl shape or amphitheater usually sculpted out of the mountain terrain by a cirque glacier.
glacier that resides in basins or amphitheaters near ridge crests; most cirque glaciers have a characteristic circular shape, with their width as wide or wider than their length.
cold glacierglacier in which most of the ice is below the pressure melting point; nonetheless, the glacier's surface may be susceptible to melt due to incoming solar radiation, and the ice at the rock/ice interface may be warmed as a result of the natural (geothermal) heat from the earth's surface.
compression flowflow that occurs when glacier motion is decelerating down-slope.
constructive metamorphismsnow metamorphism that adds molecules to sharpen the comers and edges of an ice crystal.
crevasseopen fissure in the glacier surface.
a kind of hoarfrost; ice crystals that develop by sublimation in glacial crevasses and in other cavities with cooled space and calm, still conditions under which water vapor can accumulate; physical origin is similar to depth hoar.
dead iceany part of a glacier which has ceased to flow; dead ice is usually covered with moraine.
dirt conea cone-shaped formation of ice that is covered by dirt; a dirt cone is caused by a differential pattern of ablation between the dirt covered surface and bare ice.
drain channelpreferred path for meltwater to flow from the surface through a snow cover.
drift glaciera semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a snowdrift glacier.
drumlinremnant elongated hills formed by historical glacial action; it is not clear exactly how they are formed and why they form only in some glaciated regions.
a mound or layer of moraine formed along the edge of a glacier by rock that falls off the ice; sometimes called a ground moraine.
end morainean arch-shaped ridge of moraine found near the end of a glacier.
equilibrium zonezone of a glacier in which the amount of precipitation that falls is equal to the amount that melts the following summer.
eskera sinuous ridge of sedimentary material (typically gravel or sand) deposited by streams that cut channels under or through the glacier ice.
extending flowwhen glacier motion is accelerating down-slope.
false ogivesbands of light and dark on a glacier that were formed by rock avalanching.
fjordglacial troughs that fill with sea water.
foliationlayering in glacier ice that has distinctive crystal sizes and/or bubbles; foliation is usually caused by stress and deformation that a glacier experiences as it flows over complex terrain, but can also originate as a sedimentary feature.
forbes bandsalternate bands of light and dark on a glacier; usually found below steep narrow icefalls and thought to be the result of different flow and ablation rates between summer and winter.
forel stripesshallow, parallel grooves on the face of a large melting ice crystal.
geyserfountain that develops when water from a conduit is forced up to the surface of a glacier; also called a negative mill.
glacial advancewhen a mountain glacier's terminus extends farther downvalley than before; occurs when a glacier flows downvalley faster than the rate of ablation at its terminus.
glacial erratica boulder swept from its place of origin by glacier advance or retreat and deposited elsewhere as the glacier melted; after glacial melt, the boulder might be stranded in a field or forest where no other rocks of its type or size exist.
grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial striations.
when the position of a mountain glacier's terminus is farther upvalley than before; occurs when a glacier ablates more material at its terminus than it transports into that region.
grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial grooves.
accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders; the usual composition of a moraine.
glacial trougha large u-shaped valley formed from a v-shaped valley by glacial erosion.
land covered in the past by any form of glacier is said to be glaciated.
glaciera mass of ice that originates on land, usually having an area larger than one tenth of a square kilometer; many believe that a glacier must show some type of movement; others believe that a glacier can show evidence of past or present movement.
a cave of ice, usually underneath a glacier and formed by meltwater; cave entrances are often enlarged near a glacier terminus by warm winds; most common on stagnant portions of glaciers.
a phenomenon in which strong reflection of the sun on an icy surface causes a glacier to look like it is on fire.
glacier flooda sudden outburst of water released by a glacier.
glacier floura fine powder of silt- and clay-sized particles that a glacier creates as its rock-laden ice scrapes over bedrock; usually flushed out in meltwater streams and causes water to look powdery gray; lakes and oceans that fill with glacier flour may develop a banded appearance; also called rock flour.
glacier icewell-bonded ice crystals compacted from snow with a bulk density greater than 860 kilograms per cubic-meter (55 pounds per cubic-foot).
glacier milla nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses.
glacier potholepotholes formed at the bottom of glaciers through erosion caused by sand and gravel in melt-water; melt-water seeps through crevasses in the glaciers, sometimes forming whirpools; at the bottom of the glacier, the water is under very high pressure, leading to erosion of underlying rocks.
glacier remainiea glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier, then re-adhering; also called reconstituted, reconstructed or regenerated glacier.
glacier snoutthe lowest end of a glacier; also called glacier terminus or toe.
the bottom of the ice of a glacier.
glacier tablea rock that resides on a pedestal of ice; formed by differential ablation between the rock-covered ice and surrounding bare ice.
the lowest end of a glacier; also called glacier snout or toe.
the lowest end of a glacier; also called glacier snout or terminus.
u-shaped valleys transformed from v-shaped stream valleys due to erosion caused by passing glaciers.
glaciereta very small glacier.
land overlaid at present by a glacier is said to be covered; the alternative term glacierized has not found general favour.
ground morainecontinuous layer of till near the edge or underneath a steadily retreating glacier.
hanging glaciera glacier that terminates at or near the top of a cliff.
a valley formed by a small glacier that has a valley bottom relatively higher than nearby valleys formed by larger glaciers.
headwalla steep cliff, usually the uppermost part of a cirque.
horna peak or pinnacle thinned and eroded by three or more glacial cirques.
a mass of ice adhering to a mountainside.
ice capa dome-shaped mass of glacier ice that spreads out in all directions; an ice cap is usually larger than an icefield but less than 50,000 square-kilometers (12 million acres).
a cave of ice, usually underneath a glacier and formed by meltwater; cave entrances are often enlarged near a glacier terminus by warm winds; most common on stagnant portions of glaciers.
land overlaid at present by a glacier is said to be covered; the alternative term glacierized has not found general favour.
ice dividethe boundary separating opposing flow directions of ice on a glacier or ice sheet.
ice quakea shaking of ice caused by crevasse formation or jerky motion.
ice sheeta dome-shaped mass of glacier ice that covers surrounding terrain and is greater than 50,000 square kilometers (12 million acres) (e.g., the Greenland and Antarctic ice sheets).
ice stream(1) a current of ice in an ice sheet or ice cap that flows faster than the surrounding ice (2) sometimes refers to the confluent sections of a branched-valley glacier (3) obsolete synonym of valley glaciers.
ice-cemented glaciera rock glacier that has interstitial ice a meter or so below the surface.
ice-cored glaciera rock glacier that has a buried core of ice.
icefallpart of a glacier with rapid flow and a chaotic crevassed surface; occurs where the glacier bed steepenes or narrows.
a mass of glacier ice; similar to an ice cap, and usually smaller and lacking a dome-like shape; somewhat controlled by terrain.
(1) a large outburst flood that usually occurs when a glacially dammed lake drains catastrophically (2) any catastrophic release of water from a glacier.
lateral morainea ridge-shaped moraine deposited at the side of a glacier and composed of material eroded from the valley walls by the moving glacier.
marginal crevassea crevasse near the side of a glacier formed as the glacier moves past stationary valley walls; usually oriented about 45 degrees up-glacier from the side wall.
medial morainea ridge-shaped moraine in the middle of a glacier originating from a rock outcrop, nunatak, or the converging lateral moraines of two or more ice streams.
meltwater conduita channel within, underneath, on top of, or near the side of a glacier that drains meltwater out of the glacier; usually kept open by the frictional heating of flowing water that melts the ice walls of the conduit.
morainea mound, ridge, or other distinct accumulation of glacial till.
glacial moraine that has formed a shallow place in water.
moulina nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses; also called a pothole.
mountain glaciera glacier that is confined by surrounding mountain terrain; also called an alpine glacier.
a geyser; a fountain that develops when water from a conduit is forced up to the surface of a glacier.
niche glaciervery small glacier that occupies gullies and hollows on north-facing slopes (northern hemisphere); may develop into cirque glacier if conditions are favorable.
nunataka rocky crag or small mountain projecting from and surrounded by a glacier or ice sheet.
ogivesalternate bands of light and dark ice seen on a glacier surface.
any catastrophic flooding from a glacier; may originate from trapped water in cavities inside a glacier or at the margins of glaciers or from lakes that are dammed by flowing glaciers.
outlet glaciera valley glacier which drains an inland ice sheet or ice cap and flows through a gap in peripheral mountains.
piedmont glacierlarge ice lobe spread out over surrounding terrain, associated with the terminus of a large mountain valley glacier.
a glacier entirely below freezing, except possibly for a thin layer of melt near the surface during summer or near the bed; polar glaciers are found only in polar regions of the globe or at high altitudes.
potholea nearly vertical channel in ice that is formed by flowing water; usually found after a relatively flat section of glacier in a region of transverse crevasses; also called a moulin.
push morainemoraine built out ahead of an advancing glacier.
a fissure that separates a moving glacier from its headwall rock; like a bergschrund.
reconstituted glaciera glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier then re-adhering; also called reconstructed glacier, regenerated glacier, or glacier remainie.
reconstructed glaciera glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier then re-adhering; also called reconstituted glacier, regenerated glacier, or glacier remainie.
regelationmotion of an object through ice by melting and freezing that is caused by pressure differences; this process allows a glacier to slide past small obstacles on its bed.
regenerated glaciera glacier that is reconstructed or reconstituted out of other glacier material; usually formed by seracs falling from a hanging glacier then re-adhering; also called reconstituted or reconstructed glacier, or glacier remainie.
retreatwhen a mountain glacier's terminus doesn't extend as far downvalley as it previously did; occurs when ablation surpasses accumulation.
a glacier whose terminus is increasingly retreating upvalley compared to its previous position due to a higher level of ablation compared to accumulation.
rock floura fine powder of silt- and clay-sized particles that a glacier creates as its rock-laden ice scrapes over bedrock; usually flushed out in meltwater streams, causing water to look powdery gray; lakes and oceans that fill with glacier flour may develop a banded appearance.
rock glacierlooks like a mountain glacier and has active flow; usually includes a poorly sorted mess of rocks and fine material; may include: (1) interstitial ice a meter or so below the surface (“ice-cemented”), (2) a buried core of ice (“ice-cored”), and/or (3) rock debris from avalanching snow and rock.
alternating bands of light and dark at the firn limit of a glacier; the light bands are usually young and lightest at the highest level up-glacier, becoming increasingly older and darker as they progress down-glacier.
seracan isolated block of ice that is formed where the glacier surface is fractured.
sinteringthe bonding together of ice crystals.
snowdrift glaciera semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a drift glacier.
splay crevassea crevasse pattern that forms where ice slowly spreads out sideways; commonly found near a glacier terminus.
subpolar glaciera glacier whose temperature regime is between polar and temperate; usually predominantly below freezing, but could experience extensive summer melt.
surging glaciera glacier that experiences a dramatic increase in flow rate, 10 to 100 times faster than its normal rate; usually surge events last less than one year and occur periodically, between 15 and 100 years.
a small mountain lake or pool.
terminusthe lowest end of a glacier, also called the glacier toe or glacier snout.
a large ice crystal found in deep, stagnant water-filled cavities of a glacier.
tidewater glaciermountain glacier that terminates in the ocean.
a projection of the ice edge up to several km in length caused by wind and current; usually forms when a valley glacier moves very quickly into a lake or ocean.
tributary glaciera small glacier that flows into a larger glacier.
valley glaciera mountain glacier whose flow is confined by valley walls.
wave ogivesogives that show some vertical relief on a glacier; usually the dark bands are in the hollows and the light bands are in the ridges; form at the base of steep, narrow ice falls.
weathered iceglacier ice that has been exposed to sun or warm wind so that the boundaries between ice crystals are partly disintegrated.
References:
American Meteorological Society. "Glossary of Meteorology." http://amsglossary.allenpress.com/glossary [Accessed August 16, 2006].
Beltz, Ellin. "Glossary of Glacier Terms." http://ebeltz.net/glacier/glacglos.html [Accessed August 16, 2006].
CO2 Science. "Global Change Dictionary." http://www.co2science.org/scripts/CO2ScienceB2C/education/dictionary/define.jsp [Accessed December 19, 2006].
Ferguson, Sue A., 1992. Glaciers of North America: A field guide. Golden, CO: Fulcrum Publishing.
Huschke, Ralph E., ed. 1959. Glossary of Meteorology. Boston: American Meteorological Society.
Khromov, S. P. and L. A. Mamontova, 1974. Glossary of Meteorology. Lenningrad: Gidrometeoizdat.
Van Everdingen, ed. 1994. Multilanguage Glossary of Permafrost and Related Ground-Ice Terms. Alberta: Arctic Institute of North America.
"Wikipedia." http://en.wikipedia.org/wiki/Main_Page [Accessed August 16, 2006].
1992. International Meteorological Vocabulary. Geneva, Switzerland: World Meteorological Organization.
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