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Introduction | Glossary of Terms | Ice Age in Maine

Common glossary terms and definitions:

Delta: A body of sand and gravel deposited where a stream enters a lake or ocean and drops its sediment load. Glacially deposited deltas in Maine usually consist of two parts: (1) coarse, horizontal, often gravelly "topset beds" deposited in stream channels on the flat delta top, and (2) underlying, finer-grained, inclined "foreset beds" deposited on the advancing delta front.

Deposit: General term for any accumulation of sediment, rocks, or other earth materials.

Drumlin: An elongate, oval-shaped hill, usually composed of till, that has been shaped by the flow of glacial ice, such that its long axis is parallel to the direction of ice flow.

End Moraine: A ridge of sediment deposited along the margin of a glacier. Usually consists of till and/or sand and gravel in various proportions.

Esker: A ridge of sand and gravel deposited at least partly by meltwater flowing in a tunnel within or beneath glacial ice.

Fluvial: Term used to describe river or stream-related features or processes. Fluvial deposits are sediments left by the flowing water of a stream.

Glacier: A body of ice, consisting largely of recrystalized snow, that shows evidence of downslope or outward movement due to the stress of its own weight.

Glaciolacustrine: Refers to sediments or processes involving a lake which received meltwater from glacial ice.

Glaciomarine: Refers to sediments and processes related to environments where marine water and glacial ice were in contact.

Grounding-line moraine: These moraines are formed below sea level along the grounding line where a glacier terminating in the sea goes afloat. Holocene: The time period from about 10,000 years ago to the present. It is often used synonymously with "postglacial," because most of New England has been free of glacial ice since that time.

Ice Age (aka: Pleistocene): The time period between 2-3 million years ago and 10,000 years ago, during which there were several glaciations of continental proportions. Also called the Ice Age.

Ice Contact: Refers to any sedimentary deposit or other feature that formed adjacent to glacial ice. Many such deposits show irregular topography and internal disturbance due to melting of the supporting ice against which they were laid down.

Kettle: A depression on the ground surface, ranging in outline from circular to very irregular, left by the melting of a mass of glacial ice that had been surrounded by glacial sediments. Many kettles now contain ponds or wetlands.

Lacustrine: Pertaining to a lake.

Late Wisconsinan: The most recent part of Pleistocene time, during which the latest continental ice sheet covered all or portions of New England (approx. 25,000-10,000 years ago).

Late-Glacial: Refers to the time when the most recent glacial ice sheet was receding from Maine, approximately 15,000-10,000 years ago.

Moraine: General term for sediment deposited directly from glaciers, but often used as short form of "end-moraine."

Outwash: Sediment derived from melting glacial ice, and deposited by meltwater streams in front of a glacier.

Outwash Head: The end of an outwash stream that was closest to the glacier. It helps to show where the end of a retreating glacier was when there are no glacial moraines.

Quaternary: Term for the era between 2-3 million years ago to the present. Includes both the Pleistocene and Holocene.

Striation: A narrow scratch on bedrock or a stone, produced by the abrasive action of rock debris-laden glacial ice.

Submarine Fan: A somewhat fan-shaped deposit of sand and gravel that formed by meltwater streams entering the ocean at the margin of a glacier. Similar to a delta, but was not built up to the water surface.

Till: A heterogeneous, usually non-stratified sediment deposited directly from glacial ice. Particle size may range from clay through silt, sand and gravel to large boulders.