This article is about frozen ground. For other meanings, see Permafrost (disambiguation).

Map showing extent and types of permafrost in the Northern Hemisphere

While these two men dig in Alaska to study soil, the hard permafrost requires the use of a jackhammer

In geology, permafrost or permafrost soil is soil at or below the freezing point of water (0 °C or 32 °F) for two or more years. Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent A pneumatic drill or jackhammer is a portable percussive Drill powered by Compressed air. Geology (from Greek γη gê, "earth" and λόγος Logos, "speech" lit The Celsius Temperature scale was previously known as the centigrade scale. Fahrenheit is a temperature scale named after Daniel Gabriel Fahrenheit (1686–1736 a German Physicist who proposed it in 1724 Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground material. Most permafrost is located in high latitudes (i. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the e. land in close proximity to the North and South poles), but alpine permafrost may exist at high altitudes in much lower latitudes. Altitude is the Elevation of a point or object from a known level or datum (plural data

The extent of permafrost can vary as the climate changes. Climate change is any long-term significant change in the “average weather” that a given region experiences Today, approximately 20% of the Earth's land mass is covered by permafrost (including discontinuous permafrost) or glacial ice. EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001 "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Overlying permafrost is a thin active layer that seasonally thaws during the summer. In environments containing Permafrost, the active layer is the top layer of Soil that thaws during the Summer and freezes again during the Autumn Plant life can be supported only within the active layer since growth can occur only in soil that is fully thawed for some part of the year. Plants are living Organisms belonging to the kingdom Plantae. Thickness of the active layer varies by year and location, but is typically 0. 6–4 m (2 to 12 feet) thick. The metre or meter is a unit of Length. It is the basic unit of Length in the Metric system and in the International A foot (plural feet or foot; symbol or abbreviation ft or sometimes &prime – the prime symbol) is a non-SI unit In areas of continuous permafrost and harsh winters the depth of the permafrost can be as much as 1493 m (4510 ft) in the northern Lena and Yana River basins in Siberia. Yana River (Яна is a River in Sakha in Russia, located between the Lena to the west and the Indigirka to the east Siberia (Сиби́рь Sibir) is the name given to the vast region constituting almost all of Northern Asia and for the most part currently serving

Continuous and discontinuous permafrost

Permafrost will typically form in any climate where the mean annual air temperature is less than the freezing point of water. Climate encompasses the temperatures humidity rainfall atmospheric particle count and numerous other meteorogical factors in a given region over long periods of Water is a common Chemical substance that is essential for the survival of all known forms of Life. Exceptions are found in moist-wintered forest climates, such as in Northern Scandinavia and North-Eastern Russia west of the Urals, where snow acts as an insulating blanket. Riphean redirects here For the time period see Riphean stage The Ural Mountains (Ура́льские го́ры Uralskiye The bottoms of glaciers can also be free of permafrost, although this is not common.

Typically, the below-ground temperature will be less variable from season to season than the air temperature, with temperatures tending to increase with depth. Thus, if the mean annual air temperature is only slightly below 0 °C (32 °F), permafrost will form only in spots that are sheltered — usually with a northerly aspect. In Physical geography, aspect generally refers to the direction to which a Mountain slope faces This creates what is known as discontinuous permafrost. Usually, permafrost will remain discontinuous in a climate where the mean annual soil surface temperature is between −5 and 0 °C (23 to 32 °F). In the moist-wintered areas mentioned before, there may not be even discontinuous permafrost down to −2 °C. Discontinuous permafrost is often further divided into extensive discontinuous permafrost, where permafrost covers between 50 and 90 percent of the landscape and is usually found in areas with mean annual temperatures between −2˚ and −4˚C (28˚ and 25˚ F), and sporadic permafrost, where permafrost cover is less than 50 percent of the landscape and typically occurs at mean annual temperatures between 0˚ and −2˚C (32˚ and 28˚F).

In soil science, the sporadic permafrost zone is abbreviated SPZ and the extensive discontinuous permafrost zone DPZ.

There are exceptions in un-glaciated Siberia and Alaska where the present depth of permafrost is a relic of climatic conditions during glacial ages where winters were up to 11 °C (20 °F) colder than those of today. Siberia (Сиби́рь Sibir) is the name given to the vast region constituting almost all of Northern Asia and for the most part currently serving Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent At mean annual soil surface temperatures below −5 °C (23 °F) the influence of aspect can never be sufficient to thaw permafrost and a zone of continuous permafrost (abbreviated to CPZ) forms. There are also "fossil" cold anomalies in the Geothermal gradient in areas where deep permafrost developed during the Pleistocene that still persists down to several hundred metres. The geothermal gradient is the rate of increase in temperature per unit depth in the Earth. The Suwałki cold anomaly in Poland led to the recognition that similar thermal disturbances related to Pleistocene-Holocene climatic changes are recorded in boreholes throughout Poland. [1]

A line of continuous permafrost in the Northern Hemisphere (Frozen Ground 28, 2004, p5) is formed from the most northerly points at which permafrost sometimes melts or is interrupted by regions without permafrost. Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball' North of this 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 climatic changes. Longitude (ˈlɒndʒɪˌtjuːd or ˈlɒŋgɪˌtjuːd symbolized by the Greek character Lambda (λ is the east-west Geographic coordinate measurement In the southern hemisphere, most of the equivalent line would fall within the Southern Ocean if there were land there. Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball' The Southern Ocean, also known as the Great Southern Ocean, the Antarctic Ocean and the South Polar Ocean, comprises the southernmost waters of Most of the Antarctic continent is overlain by glaciers.

Permafrost extent

Location of Permafrost in the Northern Hemisphere. Glaciers and the Greenland Ice Sheet are violet, and Arctic Sea Ice is light blue. from NSIDC

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. Global warming is the increase in the average measured temperature of the Alaska ( Аляска Alyaska) is a state in the United States of America, in the northwest of the North American continent Siberia (Сиби́рь Sibir) is the name given to the vast region constituting almost all of Northern Asia and for the most part currently serving This thawing has led to stands of trees falling, labelled drunken trees, due to insufficient rooting. Drunken trees, tilted trees, or a drunken forest, is a stand of trees displaced from their normal vertical alignment In the Yukon, the zone of continuous permafrost has moved 100 kilometres poleward since 1899, but accurate records only go back 30 years. Yukon (ˈjuːkɒn is the westernmost and smallest of Canada's three territories. It is thought that permafrost thawing could exacerbate global warming by releasing methane and other hydrocarbons, which are powerful greenhouse gases. Methane is a Chemical compound with the molecular formula. It is the simplest Alkane, and the principal component of Natural gas. In Organic chemistry, a hydrocarbon is an Organic compound consisting entirely of Hydrogen and Carbon. Greenhouse gases are gaseous constituents of the atmosphere bothnatural and anthropogenic that absorb and emit radiation at specific wavelengths within the spectrum of thermal infrared ^[1] It also could encourage erosion because permafrost lends stability to barren Arctic slopes. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind

At the Last Glacial Maximum, continuous permafrost covered a much greater area than it does today, covering all of ice-free Europe south to about Szeged and the Sea of Azov (then dry land) and China south to Beijing. The Last Glacial Maximum (LGM refers to the time of maximum extent of the Ice sheets during the last Glaciation (the Würm or Wisconsin glaciation) approximately Szeged ( (approximate pronunciation Seg-ed (known also by alternative names) is the fourth largest City of Hungary, the Regional centre The Sea of Azov (Азо́вское мо́ре - Azovskoye more; Азо́вське мо́ре - Azovs'ke more, Azaq deñizi is the world's shallowest sea linked China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National In North America, only an extremely narrow belt of permafrost existed south of the ice sheet at about the latitude of New Jersey through southern Iowa and northern Missouri. An ice sheet is a mass of Glacier Ice that covers surrounding terrain and is greater than 50000 km² (20000 mile²) New Jersey ( is a state in the Mid-Atlantic and Northeastern regions of the United States. The State of Iowa ( is a state in the Midwestern region of the United States of America. Missouri ( or) is a state in the Midwestern region of the United States bordered by Iowa, Illinois, Kentucky, Tennessee In the southern hemisphere, there is some evidence for former permafrost from this period in central Otago and Argentine Patagonia, but was probably discontinuous. History See also History of Otago The Otago Settlement sponsored by the Free Church of Scotland, materialised in March 1848 with the arrival of the first For a topic outline on this subject see List of basic Argentina topics. Llao LLaojpg|thumb|250px| Lake Nahuel Huapi, near Bariloche, Argentina

Patterned ground

Patterned ground is a term used to describe the distinct, and often symmetrical geometric shapes formed by ground material in periglacial regions. Patterned ground is a term used to describe the distinct and often symmetrical geometric shapes formed by ground material in Periglacial regions

Polygons on the ground	Stone rings on Spitsbergen	Ice wedges seen from top	Solifluction on Greenland
Phoenix landing-day image near north pole of Mars showing flat terrain, containing what appears to be a polygonal pattern, stretching from the foreground to the horizon. Phoenix is a Robotic spacecraft on a Space exploration mission on Mars under the Mars Scout Program. Patterned ground is a term used to describe the distinct and often symmetrical geometric shapes formed by ground material in Periglacial regions

Time to form deep permafrost

It has been calculated that the time required to form the deep permafrost underlying Prudhoe Bay, Alaska is 500,740 years. Prudhoe Bay (ˈpruːdoʊ is a Census-designated place (CDP located in North Slope Borough in the U This time extends over several glacial and interglacial cycles of the Pleistocene and suggests that the present climate of Prudhoe Bay is probably considerably warmer than it has been on average over that period. The Pleistocene ('plaɪstəsin is the epoch from 18 million to 10000 years BP covering the world's recent period Such warming over the past 15,000 years is widely accepted. ^[2] The table to the right shows that the first hundred metres of permafrost forms relatively quickly but that deeper levels take progressively longer.

Construction on permafrost

Utility lines in a permafrost zone must be above ground

Building on permafrost is difficult due to the heat of the building (or pipeline) melting the permafrost and sinking. Pipeline transport is the transportation of goods through a pipe. This problem has three common solutions: using foundations on wood piles; building on a thick gravel pad (usually 1-2 meters/3. A foundation is a Structure that transfers loads to the earth Gravel is rock that is of a specific Particle size range In Geology, gravel is any loose rock that is larger than two millimeters (2mm 3-6. 6 feet thick); or using anhydrous ammonia heat pipes. A heat pipe is a heat transfer mechanism that can transport large quantities of heat with a very small difference in Temperature between the hotter and colder interfaces The Trans-Alaska Pipeline System uses insulated heat pipes to prevent the pipeline from sinking. The Trans-Alaska Pipeline System ( TAPS) usually called the Alyeska Pipeline in Alaska or the Alaska Pipeline elsewhere is a major U Qingzang railway in Tibet was built using a variety of methods to keep the ground cool. The Qingzang railway, Qinghai–Xizang railway, or Qinghai–Tibet railway ( mtsho bod lcags lam མཚོ་བོད་ལྕགས་ལམ། is a high-altitude Definitions of Tibet See also Definitions of Tibet Name In English The English word Tibet, like the word for Tibet in most European

At the Permafrost Research Institute in Yakutsk, it has been found that the sinking of large buildings into the ground (known to the Yakuts before Yakutsk was founded) can be prevented by using stilts extending down to about fifteen metres or more. Yakutsk (Яку́тск Дьокуускай) is a city in the Russian Far East, located about 4° (450 kilometres Yakuts, self-designation Sakha, are a Turkic -speaking people associated with the Sakha (Yakutia Republic. At this depth the temperature does not change with the seasons, remaining at about -5 °C (23F).

References

Conversion Calculator[2]

See also

International Permafrost Association

Permafrost Young Researchers Network

XKCD reference to Permafrost

External links

• What is Permafrost?, Geological Survey of Canada
• How rapidly is permafrost changing? What are the impacts of these changes? from *NOAA
• Melting Russian Permafrost Could Accelerate Global Warming - ENS (7 September 2006)
• Mike W. Smith's page on permafrost in Canada
• Earth's permafrost starts to squelch — BBC (29 December, 2004)
• PERMAFROST: A Building Problem For Alaska
• Permafrost Young Researchers Network (PYRN)
• International Permafrost Association (IPA)
• United States Permafrost Association (USPA)
• Air Conditioning Lubricant named PermaFrost