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Glacier Power is a curriculum supplement developed by NASA’s Alaska Satellite Facility Distributed Active Archive Center (ASF DAAC).

Glossary of Terms

Ablation, Ablation zone

Processes (especially melting) by which a glacier loses ice and snow: melting, evaporation, calving, and erosion. The area of a glacier where ablation occurs.

Accumulation, Accumulation zone

Process (especially snowfall and compression) by which a glacier gains snow and ice. The area of a glacier where accumulation occurs.

Arete

Sharp, narrow ridges formed on a mountain by a glacier.

Basal Slip

The sliding of a glacier over its bed.

Bedrock

The solid rock under a glacier or ice sheet.

Boulder

Also called, “erratic boulder.” Large boulders are sometimes left behind when a glacier recedes or retreats.

Calving

Glaciers calve icebergs, which are chunks of ice that break off glaciers and fall into water.

Cirque

A bowl or basin carved out of a mountain by a young glacier.

Crevasse

An open crack in the glacier surface. (See also Types of Crevasses).

Compression

To make more compact, press together into less volume or space.

Debris

Geology: An accumulation of relatively large rock fragments: glacial debris.

Discharge

To let go; to empty out; to pour forth.

Drumlin

Smooth rounded mounds of glacial till (rock, dirt, and debris) deposited under a glacier.

ERS-1

European Remote Sensing Satellite-1.

Firn

Rounded and compact snow that is older than one year.

Fjords

Deep U-shaped coastal valleys, originally eroded by a glacier but now filled by the sea. Some fjords still contain a glacier.

Folia/Foliations

Individual layers or bands of ice crystals produced during the metamorphic process that changes snow to glacier ice.

Glacier

A large accumulation of many years of snow, ice, rock, sediment and water that originates on land and moves down slope under the influence of its own weight and gravity.

Glacier Flour

The very finely ground particles of rock, silt, or clay created by a glacier when its rock-filled ice scrapes over bedrock and which flow out from beneath a glacier in the meltwater.

Glacier Table

A boulder sitting on a pedestal of ice. The boulder protects the ice from melting during sunny weather.

Hanging Glacier

A glacier that spills out from a high level cirque or clings to a steep mountainside.

Horns

Steep-sided peaks, shaped like pyramids, formed when cirque glaciers erode on three or more sides of a mountain.

Ice Ages

A time when large sheets of ice covered a large amount of the earth because of cooler temperatures.

Ice Apron

A steep mass of ice that clings to steep rock at the summits of high peaks. (A common source of ice avalanches.)

Iceberg

See “Calving“.

Ice Cap

A steep mass of ice that clings to high peaks.

Ice Fall

Jumbled and broken ice which forms when a glacier flows over a steep drop-off.

Ice Sizzle

A crackling or sizzling sound, similar to soda or Rice Krispies, that is produced by an iceberg while it is melting. The sound is caused by the release of air bubbles that were trapped in the glacier ice during its formation under high pressure. This is also called “bergy seltzer.”

Ice Stream

A stream of ice flowing down-valley.

Ice Tongue

A floating extension of an ice stream or valley glacier projecting into the sea.

Ice Worm

Ice worms are the only earthworms known to inhabit snow and ice. They thrive in temperatures just above freezing.

Interglacials

The relatively warmer periods between each ice age when the ice sheets retreat.

Isostatic rebound

Land that was once pushed down by the heavy weight of glacial ice may experience actual rising at the small rate of about a centimeter per year after the ice melts away.

Jokulhlaup

(Outburst Flood) A tremendous release of water that was trapped behind a glacier or underneath a glacier.

Kame

Steep-sided hills of sand and gravel deposited by glacial streams or in crevasses.

Kettle

The result of a very large block of ice being left behind as a glacier recedes. The melting forms potholes which are sometimes filled with water in a glacier, till, or outwash plain. Vegetation may grow up around kettles.

Lateral Moraine

A large mass of glacial material on the sides of a glacier.

Mass Balance

The difference between the amount of material that a glacier accumulates and the amount lost during ablation is called its mass balance. The equilibrium line moves down or up a glacier as the mass balance changes.

Medial Moraine

A central moraine formed where two glaciers join to form a large glacier.

Meltwater

Water produced by melting glacier ice, firn, and surface snow. Meltwater flows down the bed of the glacier and emerges from the end as a stream often colored gray-green by the rock flour it contains.

Metamorphic

Something that undergoes changes in structure or composition, texture, or internal structure by (for glaciers) heat or pressure.

Moraine

A glacial deposit of rocks and debris that forms through direct action or contact with glacier ice.

Moulin

A hole or tube in a glacier into which water flows. Moulin is French for mill, so called because of the loud, roaring noise made by the falling water.

Neve

The area of a glacier covered with snow throughout the year.

Nunatak

Mountain peaks or ridges which poke through the ice, forming islands within the glacier.

Ogives

Repeated curved bands created within glaciers at the base of ice falls.

Outwash Plain

A broad, gentle plain composed of sand and gravel washed out of a glacier and deposited by meltwater streams.

Piedmont Glaciers

The parts of glaciers, fed by mountain glaciers, that have spread out over broad lowlands.

Rock Flour

Same as “Glacier Flour.”

SAR

Synthetic Aperture Radar (SAR) can “see” through clouds and can “see” in the dark like a bat! SAR is a microwave radar used to penetrate through clouds or darkness to obtain images of the earth.

Snow

Frozen precipitation in the form of white or translucent six-sided ice crystals that fall in soft, white flakes.

Snowflake

A single flake or crystal of snow.

Surge

A short period when a glacier can go as much as one hundred times faster that it normally goes. This happens when a glacier slides downstream on water trapped beneath it.

Surge Front

The leading edge of the wave or bulge of moving ice which represents the surge before it reaches the terminus of the glacier.

Tarn

A small lake filling a hollow which was eroded out by ice or dammed by a moraine. Frequently found with cirques.

Terminus

The snout, end, or leading edge of a glacier.

Tidewater Glacier

A glacier that ends in the sea.

Till

The rock, dirt, and debris deposited beneath a glacier.

Valley Glacier

A glacier which flows from a high mountain, from an ice cap, or from an ice sheet into a valley.

Watershed

The region draining into a river, river system, or other body of water.