|A GLACIER GLOSSARY
Avalanche: A large mass of snow, ice and rock in swift motion
down a mountainside or over a precipice.
Cleaver: A high, exposed backbone of rock that
divides two glaciers.
Cornice: An overhanging mass of wind-drifted snow,
ice or rock that forms a ledge that can break off and cause an avalanche.
Crampon: A spiked traction device that fits on a
Crevasse: A stress crack in a glacier's surface
caused by the glacier's slow downhill movement, not to be confused with crevices that form
Glacier: A large flowing body of ice that moves
slowly down a slope or valley. They exist where, over a period of years, snow remains on
the ground in all seasons.
Icefall: Refers both to an area of jagged ice
blocks, seracs and crevasses caused by a glacier's movement down a steep incline, and to
falling ice, analogous to waterfalls in rivers.
Rime Ice: Freezing, wind-blown moisture that
collects against objects and forms opaque ice crystals.
Serac: A large tower of ice usually found in or
Snow Bridge: A thick layer of snow and ice
covering a crevasse or seasonal creek that is easily broken through when a person crosses
Terminus: The down-valley end of a glacier,
sometimes referred to as the glacier snout.
Tree Well: A trench surrounding the base of a tree
caused by fallen and windblown snow. In areas of heavy snow, tree wells can be more than a
dozen feet deep on the windward side.
Whiteout: A blizzardlike weather condition peculiar
to glaciers and high altitudes in which no object casts a shadow, the horizon cannot be
seen and only dark objects are discernible. It may or may not be accompanied by snow, wind
or daylight and is described as walking inside a cloud.
Source: USGS, 1999, and Mount Rainier: A Climbing Guide, 1999.