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permanently frozen soil, subsoil, or other deposit, characteristic of arctic and some subarctic regions; similar conditions are also found at very high altitudes in mountain ranges. In 1962 measurements in a borehole drilled on Melville Island, Northwest Territories, Canada, showed that the ground was frozen to a depth of at least 1,475 ft (450 m); comparable thicknesses have been found in other far north regions. Tundrastundra
, treeless plains of N North America and N Eurasia, lying principally along the Arctic Circle, on the coasts and islands of the Arctic Ocean, and to the north of the coniferous forest belt.
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, though underlaid by permafrost, today support centers of population in Alaska, Canada, and Siberia. Permafrost is a very fragile system that may easily be damaged or destroyed by the presence of human-generated heat. A controversy developed in the late 1960s and early 70s over the construction of an oil pipeline from the Alaska North Slope to the southern part of the state. Critics of the project argued that if the pipeline containing hot oil ever came into contact with the permafrost, it would melt the permafrost; the pipeline would then sink and eventually break. The oil spilled during the breakage would result in a major ecological disaster. It was decided to build the pipeline with insulated pipe raised above the permafrost or on gravel beds in order to prevent melting and thus preserve both the pipeline and the ecosystem.



a vague term of many meanings applied to the phenomenon of the cooling of rocks on the upper part of the earth’s crust to temperatures of zero and below; the rocks themselves that have hardened as a result of the freezing of the moisture they contained; and the stratum (layer) or zone (region of horizontal spread) of rocks that do not thaw for a long time.

The term “permafrost” was introduced into scientific usage in 1927 by the founder of the school of Soviet geocryologists, M. I. Sumgin, who defined it as ground frost that exists for two to several thousand years. The phrase “ground frost” was not clearly defined in this formulation, and this led to the use of permafrost in various meanings.

As geocryology developed, investigators found themselves increasingly inconvenienced by the word “permafrost,” and as a result it was sharply criticized by P. F. Shevtsov, L. A. Meister, and others in the 1950’s at the V. A. Obruchev Institute of Geocryology of the Academy of Sciences of the USSR. This led to a prolonged discussion of all geocryological terminology. Of the many scientific terms suggested to replace “permafrost,” “perennial frozen rocks” and “perennial cryolithozone” are in widest use.


Osnovy geokriologii (merzlotovedeniia), parts 1-2. Moscow, 1959.
Materialy po obshchemu merzlotovedeniiu. Moscow, 1959.
Popov, A. I. Merzlotnye iavleniia v zemnoi kore (kriolitologiia). Moscow, 1967.
Dostovalov, B. N., and V. A. Kudriavtsev. Obshchee merzlotovedenie. Moscow, 1967.



Perennially frozen ground, occurring wherever the temperature remains below 0°C for several years, whether the ground is actually consolidated by ice or not and regardless of the nature of the rock and soil particles of which the earth is composed.


Permanently frozen soil, subsoil, or other deposits in arctic or subarctic regions.


ground that is permanently frozen, often to great depths, the surface sometimes thawing in the summer
References in periodicals archive ?
Researchers have discovered permafrost in the northern hemisphere stores massive amounts of natural mercury, a finding with significant implications for human health and ecosystems worldwide as exposure to mercury - even small amounts - can cause serious health problems.
There's no doubt that the permafrost will remain in the mountainside where the seeds are," said Marie Haga, head of the Bonn-based Crop Trust that works with Norway to run the vault.
He said: "The warmer the Earth becomes, the more permafrost is likely to be released, ultimately resulting in more greenhouse gases causing the earth to warm further.
When the Arctic permafrost tipping point or climate threshold has been passed, the permafrost begins to deliver ever-increasing amounts of heat-trapping gases to the atmosphere in response to global warming.
By academic definition, permafrost is any ground that stays below freezing year-round for more than two years in a row," Currey says.
Fears of methane release have most often focused on melting permafrost releasing the gas byproducts of rotting organic matter.
The new five projects include INVACOST: Invasive Insects and Their Cost Following Climate Change; CPATEMP: Continental PAst TEMPeratures since the last glacial cycle and recently developed organic biomarkers; APT: Acceleration of Permafrost Thaw by Snow-Vegetation Interactions; SOCLIM: Southern Ocean and Climate; and FATES: FAst Climate Changes, New Tools to Understand and Simulate the Evolution of the Earth System.
A final report on the project in 2007 found the system still functioning to maintain the permafrost below the structure (the heat pump itself had been replaced once) 14 years after its initial installation (McFadden, 2007).
But thawing, drilling and mining of ancient permafrost could potentially unleash viruses that infect people, say the discoverers of the oversized microbe.
Since 2005, about 20 GPS stations have been installed in permafrost across Mackenzie Delta.
The research team incubated a 30,000-year-old Siberian permafrost core sample taken from coastal tundra in Chukotka, near the East Siberia Sea, with acanthamoeba castellanii-a common host of giant viruses, Daily Mail reported.
A tricky challenge for moving Alaska's North Slope natural gas to market is designing a pipe that will remain safely buried for decades in hundreds of miles of chilled earth, permafrost and discontinuous permafrost.