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Glossary of Glacier Terminology


Northeast-looking photograph of a ~6-foot diameter, sub-rounded granite erratic boulder sitting on an outcrop of schist. The erratic was deposited by the Mendenhall Glacier, seen in the background. Coast Mountains, Juneau Icefield, Tongass National Forest, AK.

Erratic

A rock of unspecified shape and size, transported a significant distance from its origin by a glacier or iceberg and deposited by melting of the ice. Erratics range from pebble-size to larger than a house and usually are of a different composition that the bedrock or sediment on which they are deposited.


Southeast-looking photograph of an area recently exposed by the retreat of Steller Glacier in August 1996, the western-most part of Bering Glacier's piedmont lobe. The ground surface is covered by glacial sediment deposited as lodgement and ablation till. The erratic is an angular, ~ 20-ft-high piece of gneiss. Bering Glacier, Alaska. Bering Glacier flows through Wrangell-Saint Elias National Park.

Esker

A meandering, water-deposited, generally steep-sided sediment ridge that forms within a subglacial or englacial stream channel. Its floor can be bedrock, sediment, or ice. Subsequent melting of the glacier exposes the deposit. Generally composed of stratified sand and gravel, eskers can range from feet to miles in length and may exceed 100 feet in height.


Northeast-looking oblique aerial photograph of several meandering eskers and other glacially-produced sedimentary features, adjacent to the margin of the retreating Casement Glacier, St Elias mountains, Glacier Bay National Park, Alaska.

Eustacy

Fluctuations in the worldwide sea-level regime caused by changes in the quantity of seawater available. The greatest changes are caused by water being added to, or removed from, glaciers.


Color-coded DEM of Monterey Bay. The white line represents the current coastline. Note Monterey Canyon valley in the center of the image. DEM taken from USGS TerraWeb.

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