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active layer
active layer A seasonally thawed surface layer, between a few centimetres and about 3 m thick, that lies above the permanently frozen ground in a periglacial environment. It may be subject to considerable expansion on freezing because of the water contained, and this is especially the case if silt-sized particles dominate, with important engineering implications. See also Mollisols and permafrost.
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MICHAEL ALLABY. "active layer." A Dictionary of Ecology. 2004. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "active layer." A Dictionary of Ecology. 2004. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O14-activelayer.html MICHAEL ALLABY. "active layer." A Dictionary of Ecology. 2004. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O14-activelayer.html |
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active layer
active layer A seasonally thawed surface soil layer, between a few centimetres and about 3 m thick, that lies above the permanently frozen horizon in a periglacial environment. It may be subject to considerable expansion on freezing, especially if silt-sized particles dominate, and during the melt it may become very mobile. See also MOLLISOLS.
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Cite this article
MICHAEL ALLABY. "active layer." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. MICHAEL ALLABY. "active layer." A Dictionary of Plant Sciences. 1998. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O7-activelayer.html MICHAEL ALLABY. "active layer." A Dictionary of Plant Sciences. 1998. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O7-activelayer.html |
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active layer
active layer Seasonally thawed surface layer between a few centimetres and about 3 m thick, lying above the permanently frozen ground in a periglacial environment. It may be subject to considerable expansion on freezing, especially if silt-sized particles dominate, with important engineering implications. See also MOLLISOLS; and PERMAFROST.
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Cite this article
AILSA ALLABY and MICHAEL ALLABY. "active layer." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 1 Jun. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "active layer." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (June 1, 2012). http://www.encyclopedia.com/doc/1O13-activelayer.html AILSA ALLABY and MICHAEL ALLABY. "active layer." A Dictionary of Earth Sciences. 1999. Retrieved June 01, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-activelayer.html |
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