esker

[es-ker]
noun Geology.
a serpentine ridge of gravelly and sandy drift, believed to have been formed by streams under or in glacial ice.

Origin:
1850–55; < Irish eiscir ridge of mountains

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World English Dictionary
esker or eskar (ˈɛskə, ˈɛskɑː, -kə)
 
n
Also called: os a long winding ridge of gravel, sand, etc, originally deposited by a meltwater stream running under a glacier
 
[C19: from Old Irish escir ridge]
 
eskar or eskar
 
n
 
[C19: from Old Irish escir ridge]

Collins English Dictionary - Complete & Unabridged 10th Edition
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Etymonline
Word Origin & History

esker
"deposit left by a glacial stream," 1852, from Ir. eiscir "ridge of gravel."
Online Etymology Dictionary, © 2010 Douglas Harper
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American Heritage
Science Dictionary
esker   (ěs'kər)  Pronunciation Key 
A long, narrow, steep-sided ridge of coarse sand and gravel deposited by a stream flowing in or under a melting sheet of glacial ice. Eskers range in height from 3 m (9.8 ft) to more than 200 m (656 ft) and in length from less than 100 m (328 ft) to more than 500 km (310 mi).
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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Encyclopedia Britannica
Encyclopedia

esker

a long, narrow, winding ridge composed of stratified sand and gravel deposited by a subglacial or englacial meltwater stream. Eskers may range from 16 to 160 feet (5 to 50 m) in height, from 160 to 1,600 feet (500 m) in width, and a few hundred feet to tens of miles in length. They may occur unbroken or as detached segments. The sediment is sorted according to grain size, and cross-laminations that show only one flow direction commonly occur. Thus eskers are considered to be channel deposits (left by streams that flowed through tunnels in and below the ice) that were let down onto the ground surface as the glacier retreated. Esker formation presumably takes place after a glacier stagnates, because movement of the ice would likely spread the material and produce ground moraine. Notable areas of eskers are found in Maine, U.S.; Canada; Ireland; and Sweden. Because of ease of access, esker deposits often are quarried for their sand and gravel for construction purposes.

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Encyclopedia Britannica, 2008. Encyclopedia Britannica Online.
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Example sentences
Several large angular fragments are found neat the top of the esker.
Part of an esker, a ridge formed by a glacial stream, extends into the preserve.
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