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[pur-muh-frawst, -frost] /ˈpɜr məˌfrɔst, -ˌfrɒst/
(in arctic or subarctic regions) perennially frozen subsoil.
Also called pergelisol.
Origin of permafrost
1943; perma(nent) + frost Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for permafrost
  • It is the largest river in the world that is completely underlain by permafrost.
  • They show a surface broken into polygonal slabs by repeated freezing and thawing of the sort that happens above permafrost.
  • Vast reaches of the planet have been locked for millennia in stunning permafrost formations.
  • Thawing permafrost may soak up greenhouse gas before it begins to spew it out.
  • However, seasons are well defined and permafrost hides here on north-facing slopes and in sheltered hollows.
  • Research has begun to find the best way to unlock the energy potential of hydrates under permafrost.
  • The rest is thought to be underground as permafrost.
  • In this tough climate, bare bedrock is common, and permafrost lies beneath the rest of the area.
  • Nuclear explosions underground could quickly melt the deep permafrost.
  • Around one-fifth of the world's land area lies within the permafrost zone.
British Dictionary definitions for permafrost


ground that is permanently frozen, often to great depths, the surface sometimes thawing in the summer
Word Origin
C20: from perma(nent) + frost
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for permafrost

1943, coined in English by Russian-born U.S. geologist Siemon W. Muller (1900-1970) from perm(anent) frost.

Online Etymology Dictionary, © 2010 Douglas Harper
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permafrost in Science
A layer of soil or bedrock that has been continuously frozen for at least two years and as long as tens of thousands of years. Permafrost can reach depths of up to 1,524 m (4,999 ft). It is found throughout most of the polar regions and underlies about one fifth of the Earth's land surface.
The American Heritage® Science Dictionary
Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
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