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The extent of permafrost can vary as the climate changes, approximately 20% of the Earth's land mass is underlain by permafrost. Seasonal frost commonly overlays permafrost and is called the active layer as it will thaw during the summer. The active layer can support plant life, permafrost will not. Thickness of the active layer varies by year and location but is typically 2 to 12 feet thick. Thickness of the permafrost can go to hundreds of feet (1330 feet measured at Barrow, Alaska).
The line of continuous permafrost in the Northern Hemisphere is the edge made of the furthest-northward points at which the permafrost sometimes melts or is interrupted by regions without permafrost; north of the line all land is covered by permafrost or glacial ice. The "line" of continuous permafrost lies further north at some longitudes than others and can gradually move northward or southward due to regional climactic changes. In the southern hemisphere, most of the equivalent line would fall within the Southern Ocean if there were land there; most if not all of the antarctic continent is covered not with frozen soil but with glacial ice.
Building on permafrost is difficult due to the heat of the building (or pipeline) melting the permafrost and sinking downwards. This sinking problem has three common solutions: building up on wood piles, building on a thick gravel pad (usually 4 to 6 feet thick), or using anhydrous ammonia heat pipes. The Alaskan Oil Pipeline uses insulated heat pipes to keep the pipeline from sinking into the permafrost.
Measurement of the depth and extent of permafrost may be an indicator of global warming as recent years (1998 and 2001) have seen record thawing of permafrost in Alaska and Siberia. However accurate records only go back 30 years.
See also global warming controversy, tundra.
Permafrost is the name of a character on the Static Shock television series; see Permafrost (Static Shock)Permafrost is the name of a one-off fictional character from the animated US television series Static Shock''. Her real name is Maureen Connor. When she was younger she lived with her mother and step-father. Her mother collapsed and died at Christmas, she. It is also the name of a fictional city in EverQuestEverQuest EQ is a massively multiplayer online role-playing game ( MMORPG) released in March 1999. The original design is credited to Brad McQuaid, Steve Clover, and Bill Trost. 989 Studios funded development and initially published the game, before Veran : Permafrost (EverQuest)