Science Olympiad Dynamic Planet - Glaciers

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 winds

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 of 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 or 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 is lost; usually coincides with winter

Accumulation Zone

Area of a glacier where more mass is gained than lost

Advance

When a mountain glaciers terminus extends farther than the valley than before; glacial advance occurs when a glacier flows down a valley faster than the rate of ablation at it's 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

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 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 tributaries that flow into it; distinguished from a simple valley glacier that has only a single tributary glacier

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

a half-open steep-sided hollow at the head of a valley or on a mountainside, formed by glacial erosion.

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

a deep open crack, especially one in a glacier.

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.

Dead Ice

Any part of a glacier that 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 Glaciera

A semi-permeant 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

End Moraine

An arch-shaped ridge of moraine found near the edge 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

Geyser

Fountain that develops when water from a conduit is forced to the surface of a glacier, also called a negative mill

Glacial Advance

when a mountain glacier's terminus extends farther down the valley than before; occurs when a glacier flows downvalley faster than the rate of ablation at it's terminus

Glacial Erratic

A boulder swept from it's place of origin by glacial advance or glacial 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 it's 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 is father upvalley than before; occurs when a glacier ablates more material 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, sand, gravel, and boulders; the usual composition of 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; other believe 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 portion of glaciers

Glacial Fire

A phenomenon in which strong reflection of the sun in an icy surface causes a glacier to look like it is on fire

Glacier Flood

A sudden outburst of water released by a glacier

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 ice falls 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.

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.

Jokulhlaup

Type of glacial outburst flood that occurs when a dam containing a glacial lake fails

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/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 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.

(cutting ice with a wire)

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.

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.

frost wedging

mechanical weathering of a rock caused by the expansion of water when it freezes