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Glossary of Glacier Terminology

Glacial Groove/Glacial Furrow

A linear depression, inches to miles in length, produced by the removal of rock or sediment by the erosive action of a glacier.


August 1996 north-looking oblique aerial photograph of a recently-exposed area adjacent to the terminus of the Bering Glacier, the largest Alaskan glacier, located east of Cordova. Features present include numerous parallel glacial grooves and furrows, several eskers, and several recessional moraines. The debris-covered glacier terminus is at the top edge of the photograph. From left to right, the field of view is ~ 1.5 miles across. Bering Glacier flows through Wrangell-Saint Elias National Park. Chugach Mountains, Alaska.

July 1995 oblique aerial photograph of part of a semi-circular, blue water, supra-glacial lake on the surface of Bering Glacier. The part of the lake in the foreground consists of numerous water-filled, snow-covered crevasses. The lake formed during the 1993-95 surge of the glacier. The lake has a diameter of ~ 1/4 mile. Bering Glacier flows through Wrangell-Saint Elias National Park. Chugach Mountains, Alaska.

Glacial Lake

An accumulation of standing liquid water on (supraglacial), in (englacial), or under (subglacial) a glacier.


July 1995 oblique aerial photograph of most of a circular, blue water, supra-glacial lake on the surface of Bering Glacier, the largest Alaskan glacier, located east of Cordova. The lake formed during the 1993-95 surge of the glacier. The lake has a diameter of ~ .5 miles. Bering Glacier flows through Wrangell-Saint Elias National Park. Chugach Mountains, Alaska.

Southeast-looking photograph of a subglacial stream discharging from the terminus of Harriman Glacier, Chugach National forest, Prince William Sound, Alaska. The width of the stream channel is ~ 50 ft.

Glacial Stream

A channelized accumulation of liquid water on (supraglacial), in (englacial), or under (subglacial) a glacier, moving under the influence of gravity.


Photograph of a subglacial stream discharging from beneath Reid Glacier, Glacier Bay National Park, Alaska. Note the blue ice, and the natural levee on the right bank of the stream.

Northwest-looking photograph of the terminus of Roaring Glacier, a hanging glacier, located in Harriman Fiord, Prince William Sound, Alaska. Almost all of this glacier is experiencing ablation. Note the large bare bedrock area, located below the terminus. This area was exposed by glacier retreat during the 20th century.

Glacier

A large, perennial accumulation of ice, snow, rock, sediment and liquid water originating on land and moving down slope under the influence of its own weight and gravity; a dynamic river of ice. Glaciers are classified by their size, location, and thermal regime.


North-looking oblique aerial photograph of the lower reaches of an unnamed Alaskan valley glacier, informally known as Five Stripe Glacier, showing lateral and medial moraines, trimlines, outwash sediment, the firn line, and many other related glacial features, Chugach Mountains, Alaska. Both ablation and accumulation areas are shown.

Southwest-looking photograph of the mouth of a subglacial ice cave at the terminus of a large remnant of glacier ice, separated from the retreating Guyot Glacier, near Icy Bay. This cave was formerly a subglacial stream channel. The width and height of the cave are both ~ 25 ft. Wrangell - St Elias National Park, St Elias Mountains, Alaska.

Glacier Cave

A cave formed in or under a glacier, typically by running water. Steam or high heat flow can also form glacier caves. Also called Ice Cave.


Northeast-looking photograph of the interior of a subglacial ice cave located at the base of a large remnant of glacier ice, separated from the retreating Guyot Glacier, near Icy Bay. This cave, formerly a subglacial stream channel, still has a small stream flowing on its floor. The width and height of the cave are both ~ 25 ft, while its length is ~ 1/4 mile. Wrangell - St Elias National Park, St Elias Mountains, Alaska.

August 1994 near-vertical aerial photograph of part of the surface of the Bering Glacier showing a number of tightly folded and contorted crevasses. During the 1993-1995 surge many complex flow features were observed on the glacier's surface. Bering Glacier flows through Wrangell-Saint Elias National Park. Chugach Mountains, Alaska. The field of view is ~ 1/8 mile.

Glacier Flow

The movement of ice in a glacier, typically in a downward and outward direction, caused by the force of gravity. 'Normal' flow rates are in feet per day. 'Rapid' flow rates (i.e. surge) are in 10s or 100s of feet per day.


July 1994 near-vertical photograph of part of the ground surface adjacent to the terminus of Bering Glacier. The top several inches of moss- and algae-covered sediment have been tightly folded and contorted by the upward and right-ward push of the adjacent ice. During the 1993-1995 surge many complex ice push features were observed adjacent to the glacier. Bering Glacier flows through Wrangell-Saint Elias National Park. Chugach Mountains, Alaska. The field of view is ~ 6 ft wide.

Northeast-looking photograph of the surface of Taku Glacier showing a fault plane formed by thrust faulting. The vertical offset is ~ 1 ft. The length of the rupture was ~ 1/8 mile. Glacier ice experiences the same types of deformation as other rock types. The field of view from top to bottom is ~ 45 ft. Juneau Icefield, Tongass National Forest, Alaska.

Glacier Ice

A mono-mineralic type of rock, composed of crystals of the mineral ice, formed through metamorphism of snowflakes. Metamorphism results in recrystallization, increased density, and the growth of hexagonal crystals. This ice comprises the majority of the mass of a glacier. Intermediate stages include Firn and Névé.


Photograph of a large melting ice crystal, collected at the terminus of the Mendenhall Glacier. This crystal had a length of ~ 1 ft. Juneau Icefield, Tongass National Forest, Alaska.

Northeast-looking photograph of the surface of Taku Glacier showing a fault plane formed by normal faulting. The horizontal offset is ~ 2 ft. The length of the rupture was ~ 100 ft. Glacier ice experiences the same types of deformation as other rock types. The field of view from top to bottom is ~ 3 ft. Juneau Icefield, Tongass National Forest, Alaska.

Northwest-looking photograph of the surface of the Vaughn Lewis Glacier showing a glacier table formed by differential melting. The angular granodiorite boulder that makes the table top is ~ 4 ft-long. Juneau Icefield, Tongass National Forest, Alaska.

Glacier Table

A rock that is balanced on a pedestal of ice, and elevated above the surface of a glacier. The rock protects the pedestal of ice from melting by insulating it from the sun.


North-looking photograph of part of the surface of Bering Glacier showing a glacier table formed by differential melting. The angular crystalline boulder that makes the table top is ~ 10 ft-long. Wrangell-Saint Elias National Park. Chugach Mountains, Alaska. The field of view is ~ 40 ft wide.

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