Dynamic Planet/Glacier Vocabulary

This page contains vocabulary words that may be useful for Dynamic Planet/Glaciers. It is important to note that several of these terms, especially those derived from non-English languages, go by other names. One notable example is cirque, which also goes by corrie (Scottish) and cwm (Welsh).

A

 * Ablation Area: The area of a glacier where more glacier mass is lost than gained.
 * Ablation Hollows: Depressions in the snow surface caused by the sun or warm, gusty wind.
 * Ablation Moraine: Mound 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 Season: Period during which glaciers lose more mass than they gain; usually coincides with summer.
 * Ablation Zone: Area or zone of a glacier where snow and ice ablation exceed accumulation.
 * Accumulation Area: Area of a glacier where more mass is gained than lost.
 * Accumulation Season: Period during which a glacier gains more mass than it loses usually coincides with winter.
 * Accumulation Zone: Area of a glacier where more mass is gained than lost.
 * Advance: When a mountain glacier’s terminus extends farther down valley than before; glacial advance occurs when a glacier flows down valley faster than the rate of ablation at its terminus.
 * Alpine Glacier: A glacier that is confined by surrounding mountain terrain; also called a mountain glacier.
 * Arête: Sharp, narrow ridge formed as a result of glacial erosion from both sides.

B

 * Band Ogives: Alternate 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 Sliding: The sliding of a glacier over bedrock.
 * Bergschrund: Crevasse that separates flowing ice from stagnant ice at the head of a glacier.
 * Branched-Valley 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.

C

 * Catchment Glacier: A semi permanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a snowdrift glacier or a drift glacier.
 * Chattermarks: Striations or marks left on the surface of exposed bedrock caused by the advance and retreat of glacier ice.
 * Cirque: Bowl shaped or amphitheater usually sculpted out of the mountain terrain by a cirque glacier. Also called a corrie or cwm.
 * 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 Glacier: Glacier 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 Flow: Flow that occurs when glacier motion is decelerating down-slope.
 * Constructive Metamorphism: Snow metamorphism that adds molecules to sharpen the corners and edges of an ice crystal.
 * Crevasse: Open fissure in the glacier surface.
 * Crevasse Hoar: 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.

D

 * Dead Ice: Any part of a glacier which has ceased to flow; dead ice is usually covered with moraine.
 * Dirt Cone: A 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 Channel: Preferred path for meltwater to flow from the surface through a snow cover.
 * Drift Glacier: A semi-permanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a snowdrift glacier.
 * Drumlin: Remnant 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.
 * Dump Moraine: A mound or layer of moraine formed along the edge of a glacier by rocks that fall off the ice; sometimes called a ground moraine.

E

 * End Moraine: An arch-shaped ridge of moraine found near the end of a glacier.
 * Equilibrium Zone: Zone of a glacier in which the amount of precipitation that falls is equal to the amount that melts the following summer.
 * Esker: A sinuous ridge of sedimentary material (typically gravel or sand) deposited by streams that cut channels under or through the glacier ice.
 * Extending flow: when glacier motion is accelerating down-slope.

F

 * False ogives: bands of light and dark on a glacier that were formed by rock avalanching.
 * Fjord: glacial troughs that fill with seawater.
 * Foliation: layering 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 bands: alternate 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 stripes: shallow, parallel grooves on the face of a large melting ice crystal.

G

 * Geyser: Fountain that develops when water from a conduit is forced up to the surface of a glacier; also called a negative mill.
 * Glacial advance: when 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 Erratic: a 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.
 * Glacial grooves: grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial striations.
 * Glacial retreat: 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.
 * Glacial striations: grooves or gouges cut into the bedrock by gravel and rocks carried by glacial ice and meltwater; also called glacial grooves.
 * Glacial till: accumulations of unsorted, unstratified mixtures of clay, silt, sand, gravel, and boulders; the usual composition of a moraine.
 * Glacial trough: a large u-shaped valley formed from a v-shaped valley by glacial erosion.
 * Glaciated: land covered in the past by any form of glacier is said to be glaciated.
 * Glacier: a 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.
 * Glacier cave: 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.
 * Glacier fire: a phenomenon in which strong reflection of the sun on an icy surface causes a glacier to look like it is on fire.
 * Glacier flood: a sudden outburst of water released by a glacier.
 * Glacier flour: a 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 ice: well-bonded ice crystals compacted from snow with a bulk density greater than 860 kilograms per cubic meter (55 pounds per cubic-foot).
 * Glacier mill: a 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 pothole: potholes 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 whirlpools; at the bottom of the glacier, the water is under very high pressure, leading to erosion of underlying rocks.
 * Glacier remainie: a 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 snout: the lowest end of a glacier; also called glacier terminus or toe.
 * Glacier sole: the bottom of the ice of a glacier.
 * Glacier table: a rock that resides on a pedestal of ice; formed by differential ablation between the rock-covered ice and surrounding bare ice.
 * Glacier terminus: the lowest end of a glacier; also called glacier snout or toe.
 * Glacier toe: the lowest end of a glacier; also called glacier snout or terminus.
 * Glacier trough: u-shaped valleys transformed from v-shaped stream valleys due to erosion caused by passing glaciers.
 * Glacieret: a very small glacier.
 * Glacierized: land overlaid at present by a glacier is said to be covered; the alternative term glacierized has not found general favour.
 * Ground moraine: continuous layer of till near the edge or underneath a steadily retreating glacier.

H

 * Hanging glacier: a glacier that terminates at or near the top of a cliff.
 * Hanging valley: a valley formed by a small glacier that has a valley bottom relatively higher than nearby valleys formed by larger glaciers.
 * Headwall: a steep cliff, usually the uppermost part of a cirque.
 * Horn: a peak or pinnacle thinned and eroded by three or more glacial cirques.

I

 * Ice apron: a mass of ice adhering to a mountainside.
 * Ice cap: a 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).
 * Ice cave: 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.
 * Ice covered: land overlaid at present by a glacier is said to be covered; the alternative term glacierized has not found general favor.
 * Ice divide: the boundary separating opposing flow directions of ice on a glacier or ice sheet.
 * Ice quake: a shaking of ice caused by crevasse formation or jerky motion.
 * Ice sheet: a 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 glacier: a rock glacier that has interstitial ice a meter or so below the surface.
 * Ice-cored glacier: a rock glacier that has a buried core of ice.
 * Icefall: part of a glacier with rapid flow and a chaotic crevassed surface; occurs where the glacier bed steepens or narrows.
 * Ice field: a mass of glacier ice; similar to an ice cap, and usually smaller and lacking a dome-like shape; somewhat controlled by terrain.

J

 * Jokulhlaup: (1) a large outburst flood that usually occurs when a glacially dammed lake drains catastrophically (2) any catastrophic release of water from a glacier.

L

 * Lateral moraine: a ridge-shaped moraine deposited at the side of a glacier and composed of material eroded from the valley walls by the moving glacier.

M

 * Marginal crevasse: a 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 moraine: a 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 conduit: a 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.
 * Moraine: a mound, ridge, or other distinct accumulation of glacial till.
 * Moraine shoal: glacial moraine that has formed a shallow place in water.
 * Moulin: a 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 glacier: a glacier that is confined by surrounding mountain terrain; also called an alpine glacier.

N

 * Negative mill: a geyser; a fountain that develops when water from a conduit is forced up to the surface of a glacier.
 * Niche glacier: very small glacier that occupies gullies and hollows on north-facing slopes (northern hemisphere); may develop into cirque glacier if conditions are favorable.
 * Nunatak: a rocky crag or small mountain projecting from and surrounded by a glacier or ice sheet.

O

 * Ogives: alternate bands of light and dark ice seen on a glacier surface.
 * Outburst flood: 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 glacier: a valley glacier which drains an inland ice sheet or ice cap and flows through a gap in peripheral mountains.

P

 * Paternoster lakes: a series of tarns connected by a single stream or a braided stream system.
 * Piedmont glacier: large ice lobe spread out over surrounding terrain, associated with the terminus of a large mountain valley glacier.
 * Polar 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.
 * Pothole: a 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 moraine: moraine built out ahead of an advancing glacier.

R

 * Randkluft: a fissure that separates a moving glacier from its headwall rock; like a bergschrund.
 * Reconstituted glacier: a 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 glacier: a 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.
 * Regelation: motion 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 glacier: a 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.
 * Retreat: when a mountain glacier's terminus doesn't extend as far downvalley as it previously did; occurs when ablation surpasses accumulation.
 * Retreating glacier: a glacier whose terminus is increasingly retreating upvalley compared to its previous position due to a higher level of ablation compared to accumulation.
 * Rock flour: a 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 glacier: looks 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.

S

 * Sedimentary ogives: 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.
 * Serac: an isolated block of ice that is formed where the glacier surface is fractured.
 * Sintering: the bonding together of ice crystals.
 * Snowdrift glacier: a semipermanent mass of firn formed by drifted snow behind obstructions or in the ground; also called a catchment glacier or a drift glacier.
 * Splay crevasse: a crevasse pattern that forms where ice slowly spreads out sideways; commonly found near a glacier terminus.
 * Sub polar glacier: a glacier whose temperature regime is between polar and temperate; usually predominantly below freezing, but could experience extensive summer melt.
 * Surging glacier: a 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.

T

 * Tarn: a small mountain lake or pool.
 * Terminus: the lowest end of a glacier, also called the glacier toe or glacier snout.
 * Thomson crystal: a large ice crystal found in deep, stagnant water-filled cavities of a glacier.
 * Tidewater glacier: mountain glacier that terminates in the ocean.
 * Tongue: 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 glacier: a small glacier that flows into a larger glacier.

V

 * Valley glacier: a mountain glacier whose flow is confined by valley walls.

W

 * Wave ogives: ogives 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 ice: glacier ice that has been exposed to sun or warm wind so that the boundaries between ice crystals are partly disintegrated.