Glossary of Glacier Terms

Copyright © 2006 Ellin Beltz

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My Northeastern Illinois University Earth Science #315 students contributed words and definitions to this Class Project in Spring 2000. As in any group project, quality varies. I have received very helpful comments to update it. If you find a typo, a definition error or a word we don't have, please don't hesitate to tell me.


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In glaciers, refers to melting, erosion and evaporation which reduces the area of the ice.
ablation area or zone
The region of a glacier where more mass is lost by melting or evaporation than is gained.
Snow accretion is the growth of precipitation particles by collision of ice crystals with supercooled liquid droplets which freeze on impact.
accretion-gley(see gley)
accumulation area or zone
Where snow falls on a glacier, commonly on a snowfield or cirque.
The percent reflectivity of a surface. Ice may reflect up to 90 percent of incoming solar radiation (albedo = 90), while blacktop asphalt may absorb up to 95 percent (albedo = 5).
Sediment eroded from adjacent areas and deposited by running water in and along rivers and streams.
alpine glaciers (see mountain glaciers)
A period of time in the mid-Holocene when climate was generally warmer. Also called the hypsithermal and/or climatic optimum.
A knife-edged rock divide between two glacial cirques.
One unit of atmospheric pressure is equal to the total weight of the air on the earth's surface at sea level (14.70 pounds per square inch).
A large mass of snow, ice or rock moving down a steep part of the glacier under the influence of gravity. The first sound of an avalanche is often a hissing like sand falling through a small hole. The Snow and Avalanche Center, reports that "Avalanches equal snowpack + terrain + weather."


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basal ice
The basal layer is the part of the glacier in which the nature of the ice is directly affected by proximity to the glacier bed. [Peter Knight]
basal melting
Known specific melting rates for different substances including ice. Depends on temperature and pressure. Can lead to rapid movement.
basal sliding
When the bottom of a glacier slides directly over subglacial bedrock.
basal slip also basal sliding
Subglacial meltwater lubricates and separates the ice and the subsurface which results in the glacier sliding over the subglacial surface.
basal thermal regime
Due to their different basal thermal characteristics, cold-glaciers and warm-glaciers have different basal effects and behaviors.
A large or massive rock outcrop which projects forward from a valley wall or icefield.
The ice wall commonly found at the head of a glacier which has separated slightly from the rock wall of its cirque.
bergy bit
A large chunk of glacial ice (or a very small iceberg) which floats in the sea.
blue ice
Water molecules reflect blue wavelengths of light.
bottom bergs
Icebergs which originate from near the base of a glacier. They are usually black from trapped rock material or dark blue because of old, coarse, bubble-free ice and sit low in the water due to the weight of embedded rocks.
breccia, ice
Large angular ice fragments embedded in finer ice or snow record abrupt changes.


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The amount of heat required to raise the temperature of 1 gram of water by 1° Celsius.
calving **
Ice sheets calve by breaking off flat pieces when the walls of crevasses give way or chunks fall off the front of an ice sheet. The results are called ice bergs, bergy bits and crevasse wall breakaways.
capillary action
A function of hydrogen bonding in the water molecule results in the movement of water into small openings due to the attraction between the liquid and the walls of the opening. Water can be drawn upwards by capillary action.
Celsius or Centigrade
The international unit of measure which uses standard (1 atm) melting/evaporation points of water to divide the scale into units. Freezing occurs at 0° C; evaporation occurs at 100° C. Convert Celsius to Fahrenheit by
° F = [(1.8)° C] + 32
solved example
212° F = [(1.8) 100° C] + 32
Striations or marks left on the postglacial exposed bedrock caused by the striking of englacial debris against the bedrock surface during glacial movement.
cirque (corrie or cwm)
A steep-walled semicircular basin in a mountain caused by glacial erosion. After glaciation, the depression may contain a lake.
A connection across the rock arête dividing two cirques.
One of the three forces (see tension and shear), compression applied to an object causes deformation parallel and perpendicular to the constricting force.
compressive flow
The body of the glacier is shortened and thickened (not elastically compressed) in reaches where velocity is decreasing.
Exothermic physical process by which water vapor becomes liquid water (100C at 1atm). Releases 540 calories per gram.
The transfer of energy due to actual contact of two materials, not their movement relative to each other.
Where two ice streams or glaciers flow together, convergence occurs.
continental glaciers and ice sheets
Glaciers which cover continent size masses, for example, Greenland and Antarctica. In the Pleistocene, vast portions of the Americas and Eurasia were covered by continental glaciers.
The process of heat transfer through gas or liquid due to its own movement.
corrie (cirque or cwm)
A steep-walled semicircular basin in a mountain caused by glacial erosion. After glaciation, the depression may contain a lake.
corrie glaciers
Larger than niche glaciers, smaller than valley glaciers, they occupy hollows on bedrock faces in mountain regions.
corrie glaciation
The development of ice fields between peaks, the growth and coalescence of mountain ice caps into regional ice caps, and the growth of these regional caps into ice sheets.
Elongated open cracks in glacial ice, usually nearly vertical, and subject to change at any moment. Crevasses form due to extensional changes in velocity or gradient. They can be oriented to the glacier transverse, longitudinal or oblique and occur in marginal, central or terminal positions on the ice. A crevasse which causes an ice block to displace has caused calving. Crevasses cannot exceed 50 meters (165 feet) deep because they are closed by plastic flow below that depth.
The perennially frozen regions of the planet, including land-ice, sea-ice, permanent snow cover and permafrost. Another definition suggests it is the frozen water part of the hydrosphere (all the water on Earth) and includes continental and sea ice.
crystal lattice
The definite arrangement of atoms in a solid crystalline substance. Ice is hexagonal.
cubic centimeter
The space occupied by one milliliter of water at 20° C and 1 atm; also a cube one centimeter on each side.
crustal rebound
The earth's crust slowly expands, after the removal of intense confining pressure from the mass of continental ice sheets. Some rebound movements may cause earthquakes.
crustal subsidence
The downwarping of Earth's crust due to the immense mass of continental ice sheets.
A ridge with a gentle slope on one side and a steep slope on the other, often resulting from the movement of a glacier over a rock outcrop. Cuestas are large scale features analogous to rock knobs (roche moutonnée).
cwm (cirque or corrie)
A steep-walled semicircular basin in a mountain caused by glacial erosion. After glaciation, the depression may contain a lake.


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A deposit of sediment that occurs at a river mouth, usually triangular, named after the Greek letter "delta."
Snow dendrites are hexagonal ice crystals with complex and often fernlike branches.
Mass divided by the same unit system in volume stated as "pounds per cubic inch," "pounds per cubic foot," or "grams per cubic centimeter (cc)". Water at 20° is 1 gram/cc so DH2O is equal to 1. Densities less than one are lighter than water. Ice is less dense than water because it floats; but it is more dense than air because it does not float away. Average rock density on Earth is approximately 2.54 grams/cc or stated as density = 2.54.
depth hoar
In snow, relatively large (1 to several mm diameter), cohesionless, coarse, faceted snow crystals resulting from the presence of steep temperature gradients within the snowpack.
An exothermic physical process whereby water vapor passes directly to the frozen state. Releases 680 calories/gram of latent heat. On snowfields and glaciers, if the relative humidity (moisture content) of a packet of air is high enough that the air reaches the dew point as it cools in contact with the snow or ice, condensation occurs, releasing nearly 600 calories/gram of latent heat. Deposition can therefore be thought of as a contributor to melting under these conditions.
Unsorted, unstratified rock debris composed of a wide range of particle sizes. No process of formation is implied by the use of this term. (see till)
In glaciers, the total volume of ice passing through a specified cross section of the glacier during a particular unit of time.
The high, central stable portion of an ice sheet with low rates of accumulation and slow ice movement.
The depth below the water level, usually sea level, to whichthe base (or keel) of an iceberg penetrates is called its draft.
drift (see glacial drift)
Early writers assumed that glacial deposits had drifted in with the Great Flood.
Rock pieces trapped in icebergs and released (dropped) when the iceberg melts.
Poorly understood, streamlined, symmetric hills of drift which may have been formed by reworking of older glacial sediments, or cut from sediments confined by floating ice.


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end moraine
Unlike terminal moraines which mark the furthest advance of the ice sheet or lobe, end moraines record the continuing retreat of the ice.
All the glacial environments which occur within the ice itself are called englacial environments.
equilibrium line
The boundary between the accumulation area and the ablation area.
Wind, water, and movement of glaciers remove material from (erode) the surface of the earth.
A boulder or other rock fragment transported by glacial ice from their place of origin (or a previous glacial resting point) to an area which has a different type of bedrock.
A narrow, sinuous ridge of sorted sands and gravels deposited by a supraglacial, englacial or subglacial stream.
esker fan
A small plain of sand and gravel built at the mouth of a subglacial stream and associated with an esker formed simultaneously.
Endothermic physical process in which liquid water changes into water vapor (100C at 1 atm). Absorbs 540 calories/gram latent heat. Ice evaporating directly to water vapor is called sublimation.


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In tills which have been oriented by flowing water, fabric indicates the preferred orientation of the grains. Sedimentologists would refer to this as "imbrication."
An older form of temperature measurement. See Celsius.
false ogives
Light and dark bands on the glacier formed by rock avalanching.
fast ice
Sea ice permanently attached to its coastal glacier.
A large area blanketed with angular debris from outcrops which have suffered repeated cycles of freezing and thawing.
A deep, long and narrow opening such as a crevasse in a glacier.
A permeable aggregate of small ice grains with densities greater than 0.55 up to 0.82 where begins glacial ice.
firn limit
The dividing line between old ice and new snow at the end of the melting season.
fjords (fiords)
Steep-sided inlets of the sea which occur in flooded glacial troughs.
Glacial ice flows in two ways. (a) Ice behaves as a brittle solid until the pressure is equal to the weight of 50 meters (165 feet) of ice; then it becomes plastic and flow begins. (b) The whole mass of ice can slip along the ground, or along shear planes in the ice.
Long grooves gouged by englacial debris on subglacial pavement parallel to the direction of glacial movement.
Forbes bands
Alternating bands of light and dark ice on a glacier usually found down glacier from steep narrow icefalls and considered to be the result of different flow and ablation rates in summer and winter. Also called band ogives.
foredeepening topography
The ground below an ice sheet may be bowl-shaped with the inner part being deeper than the ground around the edges because glaciers erode preglacial material and subsidence due to the weight of the ice.
frazil ice
Disorganized, slushy ice crystals in the water column, usually near the water surface. Frazil ice is the first stage in the formation of sea ice.
An exothermic physical process in which liquid water changes into solid ice (0C at 1 atm). Releases 80 calories/gram latent heat.
Long grooves in subglacial till or pavement gouged by englacial debris. (see flutes)


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Ice towers such as seracs and penitantes.
glacial (glaciation)
(1) Period of time during an ice age when glaciers advance because of colder temperatures. (2) Involving glaciers and moving ice. Usually pertaining to processes associated with glaciers.
glacial budget
The annual relationship between accumulation and wastage. Not equivalent to fluctuations in terminus position.
glacial drift (also see outwash)
A general term for all material transported and deposited directly by or from the ice, or by water running off the glacier.
glacial ice
Consolidated, relatively impermeable ice crystal aggregates with a density greater than 0.84.
glacial lake
Proglacial lakes form the angle of the land and the angle of the glacier are opposite or in the superglacial/englacial environment. Enormous quantities of fine particles are transported by glacial meltwater, leading to the milky or cloudy appearance of many glacial lakes. After glacial melting, tarn lakes, kettle lakes and Pater Noster lakes remain.
glacial milk
Term used to describe glacial meltwater which has a light colored or cloudy appearance because of clay-sized sediment held in suspension.
glacial outburst flood
A sudden release of melt water from a glacier or glacier-dammed lake sometimes resulting in a catastrophic flood, formed by melting of a channel or by subglacial volcanic activity.
glacial polish
The abrasion of bedrock surfaces by materials carried on the bottom of a glacier. This process leaves these surfaces smooth and shiny.
glacial portal
Cavernous openings in subglacial ice and debris above meltwater streams.
glacial retreat
The backwards movement of the snout of a glacier.
glacial surge
A rapid forward movement of the snout of a glacier. Others describe it as rapid, wavelike downglacial ice movements which cause sudden advances of the ice margin.
glacial trough
Glaciers transform v-shaped stream valleys to u-shaped glacial troughs by erosion.
glacial uplift
Upward movement of the Earth's crust following isostatic depression from the weight of the continental glaciers.
A large long lasting accumulation of snow and ice that develops on land. Most glaciers flow along topographic gradients because of their weight and gravity. Also defined as: A mass of snow and ice flowing mostly down gradient due to gravity.
glacial deposit
Sedimentary material carried by the glacier and left behind when the ice melts.
glacier karst
Stagnant ice covered by debris with surficial lakes, lakes in buried caverns or tunnels, typically found at the ice/soil or ice/water interface of a retreating glacier.
glacier table
A rock sitting on top of a pillar of ice shielded from insolation by the rock's mass.
glacier terminus
Where the glacier ends, the leading edge of the glacier, also called the glacier nose.
glacier trough
Steep U-shaped valley with a flat bottom caused by glacial scour and erosion.
Geomorphic feature whose origin is related to the processes associated with glacial meltwater.
The study of the physical and chemical propeties of snow and ice.
A smooth, clear coat of ice on older ice, rock or any other surface.
A soil formation process that occurs in poorly drained environments. Results in the development of extensive soil organic layer over a layer of chemically reduced clay that takes on a blue color.
Dark gray to black, massive and dense sediment which accumulated slowly in low, wet, poorly drained areas.
grease ice
Thin plates of organized ice crystals on the surface of water.
Highly weathered till which becomes sticky and plastic when wet.
Elevation divided by ground distance, for example, a fall of one kilometer over two kilometers on the ground would result in a 50% gradient. Any units may be used; many American publications give gradients in feet per mile.
In metric units the weight of one cubic centimeter of water at 20° Celsius and 1 atm.
Variations in temperature, migration of liquid and vapor water, and pressure of snow cover may result in rounded snow pellets from 2 to 5 mm diameter. Graupel is visually similar to hail, but lacks the banded outward growth pattern of hail.
As the glacier moves forward, rocks imbedded in the ice scratch the underlying materials. If small, these linear features are called striations. Grooves are larger features which may be regular or irregular and may be helpful in establishing direction of glacial flow.
ground moraine
A gently rolling ground surface underlain by till deposited beneath a glacier and usually bordered by terminal moraines.
grounding line
The place where a glacier extending into the sea or a lake loses contact with the seafloor and begins to float as an ice shelf. The grounding line may be a place with high sediment accumulation.
European glaciation related to North American Nebraskan glaciation.


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hanging glacier
Ice moving out of high cirques can carve hanging valleys unconnected to a lower glacial mass on steep slopes.
hanging valleys
Tributary glaciers are often smaller than the main glacier and do not cut as deeply. When the ice melts, these shallower glacial troughs lead into the deeper main trough, leaving hanging valleys. Waterfalls are common features of hanging valleys (e.g. Bridal Veil Falls in Yosemite).
The steep rock at the top edge of the cirque.
A light, feathery coating of ice.
A peak or pinnacle thinned and eroded by three or more glacial cirques. The Matterhorn of the Swiss Alps was formed in this manner.
A period of time in the mid-Holocene when climate was generally warmer. Also called the altithermal.


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The solid form of water is called ice.
ice age
Reoccuring periods in Earth history when the climate was colder and glaciers expanded to cover larger areas of the Earth's surface.
Floating chunks of ice which calved off the glacier 5/6th underwater 1/6th above. Northern hemisphere bergs are fractured off the glacial edge and tend to have jagged tops, while Southern hemisphere bergs have about 60 to 90 meters above the sea and are flat on top because they fractured from the flat topped ice shelves which project out over the Southern oceans. Icebergs can occur in fresh or salt water.
ice blocks
Chunks of the glacier remain as ice blocks after glacial outburst floods which may remain as kettle lakes.
ice breccia
Large angular ice fragments embedded in finer ice or snow record abrupt changes.
ice caps
Smaller ice sheets which cap many islands in the Arctic Ocean and in and near Iceland.
ice cliff
Walls of ice where glaciers meet the sea, such as at the edge of land or the edge of an ice shelf.
ice contact deposit
The multiple types of accumulated stratified sediment left behind when meltwater flows over, within, and at the base of a motionless, melting terminus. See kame, kame terraces and eskers.
ice crystals
Ice crystals are hexagonal in internal structure. The basal plane is weak and permits slip.
ice density
Pure ice density is rarely attained except in individual crystals but is assigned the value of 0.917.
ice fall
The reaction of glacial snow and ice to subglacial changes in gradient. The icefall is broken by crevasses and moves constantly when conditions are favorable. Downglacier from icefalls are ogives.
ice floes
Areas of broken pack ice, chaotically fractured and floating on the near-frozen sea. A great hazard to Arctic explorers is getting stranded or isolated on a floe. The open water gaps between floes are called leads. Where floes jam together, jagged sutures appear due to compression.
ice islands
Bodies of land ice calved from sheet or shelf.
ice quakes
The beginning of the formation of a crevasse or moulin is often accompanied by shaking ice and a hissing or cracking sound.
ice rafted debris
Material carried by floating ice that eventually melts and is deposited on the floor of the sea or a lake.
ice sheets (see continental glaciers)
ice shelf
A large flat-topped sheet of ice that is attached to land along one side and floats in an ocean or lake. More ice is added from the flow of ice from land and is removed by calving and/or melting.
ice sizzle
Sounds made by glaciers which sound like carbonated soda.
ice streams
In glaciers, ice flows in lineaments which, if they encounter other ice streams, do not mix. River inflow streams eventually mix, although they may remain discrete in their early encounter. Ice streams gouge their bases and carry till. The sides of ice streams may be marked by lateral moraines and where two streams flow, there may be medial moraines of till dividing the ice streams. Ice streams may reach terminus; or may melt away before then leaving lobate terminal moraines.
ice tongue
A long, narrow projection of ice which points out for the coastline where a valley glacier flows rapidly into the sea or a lake.
ice-wedge casts
A vertical structure that results from cracks in frozen ground (by means of ice wedging) which are later filled by sediment. They are similar to infilled mudcracks in drying lakes, but usually larger.
North American glaciation related to European Riss glaciation.
imbrication (see fabric)
The amount of solar radiation received in a specific area. Equatorial areas receive 2.4 times as much as polar areas.
interglacial periods
Times between recognized advances of the ice. Sea level can be hundreds of feet higher in interglacials than in glacial periods. The present time is the latest interglacial period.
internal deformation
One of the ways glaciers flow is by movement across the faces of the ice crystals that make the glacier.
Isostatic rebound adjustment (see glacial rebound)
Up or down warping of the Earth's lithosphere to accommodate for mass being added or removed. Northern Ontario, Canada is rebounding in adjustment to the last glacial retreat 10,000 years ago.


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Pronounced "Yo-kul-hloip," it refers to a glacial outburst flood.


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A low, but steep-sided hill or mound composed of poorly sorted sands and gravels deposited in strata by meltwater plunging into crevasses near the melting edge of an ablating glacier.
Flat-topped ridges built of stratified sand and gravel deposed by a melt water stream between an ablating glacier or a stagnant ice lobe and a higher wall or lateral moraine. The ridge remains after the ice melts away.
North American glaciation related to European Mindel glaciation.
katabatic wind
A wind that flows from a glacier, caused by air cooled by the ice becoming heavier than surrounding air, then draining down-valley.
A shallow basin or bowl shaped depression formed when a large block of ice is buried in outwash or diamicton during ablation. Upon melting and dewatering of the sediment the hole left by the block may become a kettle-lake or a kettle-depression.
kinematic waves
These ice waves move downglacier and are propagated by increasing glacial thickness. Kinematic waves may move two to six times the velocity of surrounding, thinner ice.


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Pertaining to lakes. Lacustrine proglacial deposits usually show confined sorting of fine sized sedimentary particles. They may have dropstones if icebergs once floated in the lake. Other lakes associated with glaciers are supraglacial lakes and kettle lakes.
lateral moraines
A moraine which forms on the side of the ice stream, often where the ice meets the rock wall. Also described as: Piles of loose unsorted rocks along the side margins of a glacier which may fallen there, been pushed there by the ice or dumped from the rounded upper surface of the glacier.
Long, narrow openings or fractures in sea ice.
A thick-in-the-middle/thin-at-the-edges geologic deposit in which the surfaces converge together.
Windblown rock flour of the silt size class. Loess ("luss") deposits are widespread, homogeneous, massive and unconsolidated fine grained deposits which blankets much of Illinois' downstate landscape. Isolated loess lenses have been found in Chicago Lake Plain deposits.
Calcarous concretions found in loess deposits. Called "children of the loess" by the Germans who were the first to describe them because the concretions often take pentacular or homunucular proportions.


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marine-based ice sheet
A large mass of ice with its base grounded below sea level.
mass balance
The balance of glacial input (accumulation), throughput (transport), and output (ablation) of snow and ice.
medial moraines
Concentrations of till in septa dividing ice streams deposits as medial moraines after complete ablation. Also described as: Where two mountain glacier lateral moraines unite, a dark band of rock forms along the centerline.
Water from melted snow or ice.
An endothermic physical process in which solid ice changes into liquid water (0° C at 1 atm). Absorbs 80 calories/gram latent heat.
European glaciation related to North American Kansan glaciation.
Unsorted till (diamicton) deposited either along the sides (lateral moraine) or the ends of an ablating glacier (end or terminal moraine); or the material below a retreating glacier (ground moraine).
A vertical shaft at the downslope end of a transverse fissure. Hence the erotic appeal of "Moulin Rouge," of Paris in the 1890s. Water flowing down moulins often makes load roaring sounds.
mountain glaciers
Glaciers which form in the mountains.


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North American glaciation related to European Gunz glaciation.
net balance
The change in the amount of mass of a glacier from one year to the next.
The upper area of accumulation in a glacier where firn is found.
Newtonian fluid
A fluid which yields to increasing force (stress) at a uniformly increasing rate.
An Inuit (Eskimo) word for mountains or lands which protrude through the ice.


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ogives *
A series of ice waves or bands of lighter and darker material formed below ice falls in some glaciers. Also called Forbes bands, true band ogives are laid down one per year and represent different flow rates through the steep, narrow ice falls. (see false ogives)
outlet glaciers
Valley glaciers which permit ice to move from accumulation areas through mountainous terrain to the sea.
Stratified sands and gravels washed out from glaciers by meltwater streams and deposited in the proglacial environment, or beyond the active glacial margin.
outwash plain
Proglacial meltwater deposits unconfined sorted sediments; stream pattern depends upon angle of topography.


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pack ice (see sea ice and ice floes)
An ancient or buried soil, often used as a stratigraphic marker for interglacial periods.
pancake ice
Coherent plates of ice that can reach a few meters across and grow from thickened grease ice and resembles pancakes or lily pads.
Pater Noster lakes
A string of glacial lakes along the path of a mountain glacier. After the glacier melts, erosional topographic depressions fill with water. The name comes from the similarity to a string of Catholic Christian prayer beads; the first prayer of which begins "Pater Noster..."
patterned ground
Polygonal or circular ground patterns which develop from contrasting size/color soils in poorly drained areas subject to intensive frost action.
A rock surface, often eroded or striated, which underlies glacial till and is exposed in sufficient quantity to resemble a sidewalk or open plaza.
The area around a glacier often characterized by harsh climate.
Soil or rock at or near the ground in Arctic or subarctic regions that has been continuously frozen for a long time.
Physical matter is defined to occur in three phases; solid, liquid and gas.
piedmont glacier
A glacier occurring on the piedmont, the gradually sloping area leading down from a mountain to the plains or to the sea. The Malaspina Glacier is a piedmont glacier. Piedmont glaciers are fed by one or more valley glaciers.
Large mounds of earth-covered ice which form in a permafrost environment which are found in Alaska, Greenland and Antarctica. Pingos may be up to 70 meters tall and 600 meters diameter. The word was borrowed from the Inuit in 1938 by A.E. Porsild after whom Porsild Pingo in Tuktoyaktuk was named. Pingos have an average life-time of about 1,000 years.
In climbing, a unit of measure approximately equal to the length of your rope, or the distance between fixed anchor positions. To go secured from pitch 3 to pitch 4 of a glacier means that you would be protected by a rope and safety gear during that part of the ascent. "Unprotected pitches" include many icefalls and crevasse fields.
Used to refer to angle or gradient. "A steep pitch" would therefore mean a high gradient or high angle.
plastic flow
In glaciers, plastic flow in ice begins at 50 meters (165 feet) from the top of the ice surface.
plastic solid
A perfectly plastic solid yields after a critical threshold of stress has been exceeded. Theoretically, the material yields at an infinite rate after that.
The process of loosening and lifting pieces of rock by a flowing glacier. Meltwater intrudes joints and cracks in the underlying material. The freeze/thaw contraction/expansion series provides the leverage to release large blocks of rock.
Polar plateau
The relatively flat, elevated central region of the East Antarctic Ice Sheet.
The open seawater between pack-ice and the land or the edge of a glacier.
portal **
Cavernous openings in subglacial ice and debris above meltwater streams.
The process by which crystals form from saturated solutions. In meteorology "precipitation" means rain, drizzle, snow, hail and other solid forms.
The area in front of, or just at the outer edge of a glacier.
proglacial ground angle
If the proglacial ground angle and the ice are similar, meltwater flows away. Conversely if the proglacial ground angle and the ice angle are opposite, meltwater fills the resulting topographic low spot.
proglacial lakes (see glacial lakes)


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The most recent period of the Cenozoic Era which began about 2 million years ago; the two epochs of the Quaternary include the Holocene (the present epoch) and the Pleistocene, which lasted from about 2 million years ago to about 10,000 years ago.


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In both streams and glaciers, stretches of the flowing material which are different from those above and below.
The upwarping of Earth's crust after additional weight is removed from it. (see subsidence)
recessional moraines
End moraines created during occasionally stabilization of the ice front during retreat.
The process of localized melting and refreezing of ice, involving no overall change in glacier mass.
relative humidity
Relative humidity is actual humidity of a packet of air divided by maximum possible humidity that air can hold. In glaciers, if the relative humidity of a packet of air is high enough that the air reaches the dew point as it cools in contact with the snow or ice, condensation occurs, releasing +AH4- 680 calories/gram of latent heat.
The vertical difference between the surface in valleys and hilltops or the vertical between the base of a glacier and its top.
The study of flow behavior and characteristics.
Ice deposits formed when supercooled water droplets freeze on contact with an object (deposition).
European glaciation related to North American Illinoian glaciation.
roches moutonnée **
An Alpine term for a rock knob with one smooth side and one steep side, produced by glacial plucking. They are named "fleecy rocks" in French because they often look like a field of giant stone sheep. Roche moutonnee formations are sometimes called "sheepbacks" in English.
rock knob
Carved by the forward advance of the glacier, these knobs have a smooth side and a plucked side. The glacier flowed from the smooth side over the top and plucked out the rock on the down flow side. Central Park, New York City is full of mica-schist rock knobs. Rock knobs and the associated intra-knob depressions may result in the string of lakes known as Pater Noster lakes after the glacier has melted.
rock flour **
Pulverized rock of the smaller size sediment classes (silts and clays) produced by glacial milling can give outwash streams a milky appearance.
rock glaciers
A mass of rock (talus) held together by ice that moves down gradient like a glacier.


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A depression or sag on the ice sheet between domes.
sandar *
Flat outwash plains caused by glacial melting feature braided streams and sinous sand and gravel bars.
saturation vapor pressure of water
The maximum amount of water vapor needed to keep moist air in equilibrium with a surface of pure water. This is the maximum water vapor the air can hold for any given combination of temperature and pressure. (see relative humidity)
To remove or sweep away material.
sea ice
At temperatures of -2° C (28.5° F), freezes directly from ocean water to a thickness of five meters (15 feet). Loosely packed groups of thin floating ice are called ice floes.
Dividing lines between chambers or compartments (such as nasal sinus). In glaciers, vertical partitions between two ice streams or currents within the ice.
Unstable ice pinnacles formed by intersecting crevasse planes, usually in areas of fast glacier movement.
See roche moutonnée.
sheet flow
Unrestricted glaciers including ice caps and ice sheets flow independently of underlying topography. Friction is greatest between the glacier and its base in this form of flow.
slush limit
The highest point from which runoff occurs.
stratified drift
Sediments laid down by glacial meltwater show unconfined sorting.
streaming flow
Where glaciers are constricted, such as in a valley, the flow may or may not be controlled by underlying topography. Friction is greatest at the center and less towards the margins.
snow density
New fallen snow density is near or less than 0.1. Old snow (corn snow) is up to 0.55. Firn density is 0.55 up to 0.82 where begins glacial ice.
The amount of snow which has accumulated since the last observation. Intervals of observation may be measured in any unit of time.
The zone of accumulation sometimes a cirque, cwm or corrie; or a large open collecting point between mountains.
A six-pointed cluster of ice crystals which fall from a cloud is called a snowflake.
snow line
The lower limit of permanent snow cover, below which snow doesn't accumulate.
The total ice and snow on the ground, including fresh and older snow and ice.
A slow, viscous, downslope flow of saturated sediment and rock debris especially in areas underlain by frozen ground.
The result of a physical material to stress.
stratified drift
Layered and sorted sediments deposited by meltwater streams or bodies of water adjacent to the ice.
Force applied to an object per its unit area. Subglacial forces on rock are sufficient to fracture it, and are considered to exceed 60,000 pounds per square inch in some places.
Gouges in bedrock or on glacial sediments which record abrasion by the moving glacier. If on pavement, stria may reveal direction of glacial movement.
The area below the glacier. Subglacial features include deformed sediments, ice caves, and eskers.
An endothermic physical process whereby ice passes directly into the vapor state. Absorbs 720 calories/gram of latent heat. Occasionally meterologists use sublimation for both sublimation and its opposite process, deposition. Sublimation is far more costly in energy than proceeding stepwise through melting then evaporation (80 + 100 + 540 = 720 calories/gram); so it is less effective as an agent of ablation than is melting.
The downwarping of Earth's crust due to additional weight (such as a glacier or a transgressing sea) being applied to it.
A melted bowl-shaped depression in ice due to insolation.
Supercooled water remains in the liquid state even though the its temperature is below its freezing point.
The area on top of the glacier which may be snow, ice, rock fragments or covered with soil, plants or forests.
In water, the condition which occurs in the atmosphere when the relative humidity is greater than 100 percent.
Periods of extremely rapid movements in glacial flow.
surface hoar
Deposition of ice crystals on a surface which occurs when the temperature of the surface is colder than the air above and colder than the frost point of that air.


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tabular iceberg
A flat-topped iceberg, usually formed by breaking off an ice shelf.
tarn lake
After melting, the central depression of a former cirque may hold a tarn lake.
temperature-gradient metamorphism
Process of firnification when large temperature gradients exist within the snowpack, such as within adjacent layers of snow. When all snow is fully converted to ice, the density is about 830-840 kg/cubic meter.
One of the three forces (see compression and shear); in ice, tension creates crevasses.
terminal moraine
A ridge formed by the accumulation of glacial deposits at the point marking the furthest advance of an ablating glacier.
The end of the glacier. Also called a glacial snout.
Land above sea level.
The geological time period before the Quaternary composed of Paleocene, Eocene, Oligocene, Miocene, and Pliocene.
Many writers use till for any glacial deposit. However some (including ISGS) define till to mean only sediments composed of a mixture of grain sizes which were deposited directly onto the subglacial landscape during basal melting. (see diamicton)
till plain
A gently irregular plain of till deposited by an actively retreating glacier.
The shape of a landscape, composed of its relief and position of natural and man-made features.
transient snowline
The line separating transient accumulation and ablation areas, also a transient equilibrium line.
transverse fissure
A vertical crevasse in a glacier which runs in an upslope-downslope direction (see moulin)
Sharp boundaries in vegetation abundance or community type showing the upper margin of a former glaciation. For example, ferns colonize recently deglaciated areas and conifers show that the area has been deglaciated longer.
In glaciers, truncated surfaces occur along the sides of valley glaciers, beneath mountain and continental glaciers, and across the tops of sediments previously laid down.
truncated spurs
Triangular hillside features due to glacial erosion of the headlands between two former streams.
A level to undulating treeless plain characteristic of Arctic and subarctic regions. Depressed by glaciation, the knobby surface has many marshes. It is underlain by dark, mucky soil (gley) and permafrost.
tuya *
Volcanos which erupted beneath glaciers, melts through the ice above and finishes with a subaerial lava flow are called "tuyas" after the type locality, Tuya Butte, Stikine Belt, Northwest British Columbia, Canada. Also called "table mountains," the typical flat-top is created by the explosive interaction of hot magmas and lavas with water and ice. Tuyas reveal the height of the ice at the time of eruption and may be used as part of correlative dating. Similar volcanic structures, called "guyots" or "sea mounts," are created under the oceans when magma hits ocean water.


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United States Geological Survey The USGS provides data on glaciers both in the US and in Antarctica, but links to sites with global information.


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valley glacier
A stream of ice flowing down gradient.
valley train
Outwash confined between two rock walls, moraines or by unmelted ice, ice blocks or calving ablation fields.
Distance traveled per unit time.
A faceted or triangular-shaped stone formed by sandblasting in strong winds, often highly polished.


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wastage area
On a glacier, the terminal end where ablation results in deposition of till and removal of water.
The process of physical and chemical decomposition which changes earth and rock materials in color, texture, composition, firmness or form. These changes are accomplished by the effects of energy and exposure to water, other fluids and the atmosphere.
Elongated mounds or hills shaped by glacier movement may indicate direction of ice flow.
A weather condition in which the horizon cannot be identified and there are no shadows. White snow blends everywhere. All you see is white. (I've been there before, it's scary. Michaelene Cutro)
North American glaciation related to European Wurm glaciation.
European glaciation related to North American Wisconsinan glaciation.


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zone of ablation
The termini of glaciers where loss of ice occurs through calving, melting or evaporation.
zone of accumulation
The snowfields or cirques of mountain glaciers and the snowfields of continental glaciers are called the zone of accumulation because it is here than new snow falls to nourish the glacier.
zone of fracture
The upper 50 meters of glacial ice is brittle and is carried by the ice below it.
zone of wastage
The area or areas on a glacier where there is a net loss of snow and ice from the glacier.


  • Sharp, Robert P. 1960 Glaciers. Congden Lectures. Oregon State University, Eugene.
  • Killey, Myrna M. 1998. Illinois' Ice Age Legacy. GeoScience Education Series 14, Illinois State Geological Survey, Champaign-Urbana.
  • Tarbuck, Edward J. and Frederick K. Lutgens. 1997. Earth Science. Eighth edition. Prentice- Hall, Upper Saddle River, New Jersey.
  • Peter Knight, personal communications.
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Ellin Beltz
December 1, 2006
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