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Glossary of Glacier Terminology


This quarter mile-long mass of glacier ice, formerly a part of Guyot Glacier, is rapidly melting away in Wrangell-St.Elias National Park, Alaska.

Remnant

An isolated melting mass of glacier ice, that has become detached from its source and the remainder of the glacier. Some remnants cover many square miles.


This large mass of ice known as the Muir Remnant was formerly connected to the retreating Muir Glacier, in Glacier Bay National Park, Alaska. Its maximum length was more than 2 miles.

This cirque and valley was recently filled by a much larger icemass that connected it to the surface of the Bering Glacier, which now lies separate in the foreground. Note the well-exposed trimline. Bagley ice valley, Wrangell-St.Elias National Park, Alaska.

Retreat

A decrease in the length of a glacier compared to a previous point in time. As ice in a glacier is always moving forward, its terminus retreats when more ice is lost at the terminus to melting and/or calving than reaches the terminus. During retreat, ice in a glacier does not move back up the valley.


The bedrock in this photo has recently emerged from the shrinking Mendenhall Glacier seen at the upper left of this picture. The Mendenhall Glacier retreats as much as 50 ft per year. Juneau Ice Field, Tongass National Forest, Alaska.

Roche Moutonnée

An elongated, rounded, asymmetrical, bedrock knob produced by glacier erosion. It has a gentle slope on its up-glacier side and a steep- to vertical-face on the down-glacier side.


Glacier erosion has produced this streamilined bedrock mass projecting above the waters of Glacier Bay, Glacier Bay National Park, Alaska.

This large landslide covered more than half the width of Allen Glacier, Chugach Mountains, Alaska.

Rockslide

A mass of unsorted, generally angular rock material that has fallen from the adjacent wall of the bedrock valley onto the surface of a glacier. Many rockslides are triggered by seismic activity.


Several landslides generated by the Great Alaskan Earthquake, Good Friday 1964, fell onto the surface of the so-named glacierin the Chugach Mountains, Alaska.

Rock flour is seen mixing with sedmient-free water at the confluence of a glacial and non-glacial stream in Denali National Park, Alaska.

Rock Flour

Fine-grained, silt-size sediment formed by the mechanical erosion of bedrock at the base and sides of a glacier by moving ice. When it enters a stream, it turns the stream's color brown, gray, iridescent blue-green, or milky white. Also called Glacier Flour or Glacier Milk.


LANDSAT MSS satellite image showing large quantities of suspended sediment, composed of rock flour, in the Gulf of Alaska south of the Copper River, Alaska.

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