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Encyclopedia > Permafrost
While these two men dig in Alaska to study soil, the hard permafrost requires the use of a jackhammer
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. 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 (e.g. North and South poles), but alpine permafrost exists at high altitudes. Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution‎ (2,816 × 2,112 pixels, file size: 1. ... Image File history File links Metadata Size of this preview: 800 × 600 pixelsFull resolution‎ (2,816 × 2,112 pixels, file size: 1. ... For other uses, see Alaska (disambiguation). ... This article is about the construction tool. ... This article includes a list of works cited but its sources remain unclear because it lacks in-text citations. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... For other uses, see Fahrenheit (disambiguation). ... This article is about the geographical term. ... Altitude is the elevation of an object from a known level or datum. ...

The extent of permafrost can vary as the climate changes. Today, approximately 20% of the Earth's land mass is covered by permafrost (including discontinuous permafrost) or glacial ice. Overlying permafrost is a thin active layer that seasonally thaws during the summer. 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. Thickness of the active layer varies by year and location, but is typically 0.6–4 m (2 to 12 feet) thick. 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. Variations in CO2, temperature and dust from the Vostok ice core over the last 450,000 years For current global climate change, see Global warming. ... This article is about Earth as a planet. ... This article is about the geological formation. ... This does not cite its references or sources. ... For other uses, see Plant (disambiguation). ... This article is about the unit of length. ... A foot (plural: feet or foot;[1] symbol or abbreviation: ft or, sometimes, ′ – a prime) is a unit of length, in a number of different systems, including English units, Imperial units, and United States customary units. ... The Lena (Russian: Ле́на) in Siberia is the 10th longest river in the world and has the 9th largest watershed. ... The Yana River (Яна in Russian), a river in Sakha in Russia, located between the Lena to the west and the Indigirka to the east. ... This article is about Siberia as a whole. ...


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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. 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. The bottoms of glaciers can also be free of permafrost, although this is not common. Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... Map of the Ural Mountains The Ural Mountains (Russian: , Uralskiye gory) (also known as the Urals, the Riphean Mountains in Greco-Roman antiquity, and known as the Stone Belt) are a mountain range that runs roughly north and south through western Russia. ...

Typically, the 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. 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 geography, aspect generally refers to the direction to which a mountain slope faces. ...

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. 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 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] This article is about Siberia as a whole. ... For other uses, see Alaska (disambiguation). ... penis, hahaha big long penis. ...

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. 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. In the southern hemisphere, most of the equivalent line would fall within the Southern Ocean if there were land there. Most of the Antarctic continent is overlain by glaciers. Northern hemisphere highlighted in yellow. ... Longitude is the east-west geographic coordinate measurement most commonly utilized in cartography and global navigation. ... southern hemisphere highlighted in yellow (Antarctica not depicted). ... For other uses, see Antarctica (disambiguation). ...

Permafrost extent

Polygons on the ground.
Polygons on the ground.

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. This thawing has led to stands of trees falling, labelled drunken trees, due to insufficient rooting. In the Yukon, the zone of continuous permafrost has moved 100 kilometres poleward since 1899, but accurate records only go back 30 years. It is thought that permafrost thawing could exacerbate global warming by releasing methane and other hydrocarbons, which are powerful greenhouse gases.[1] It also could encourage erosion because permafrost lends stability to barren Arctic slopes. Image File history File links Polygon on the ground. ... Image File history File links Polygon on the ground. ... Global warming refers to the increase in the average temperature of the Earths near-surface air and oceans in recent decades and its projected continuation. ... This article is considered orphaned, since there are very few or no other articles that link to this one. ... This article is about Yukon Territory in Canada. ... Methane is a chemical compound with the molecular formula CH4. ... Oil refineries are key to obtaining hydrocarbons; crude oil is processed through several stages to form desirable hydrocarbons, used in fuel and other commercial products. ... Greenhouse gases are gaseous components of the atmosphere that contribute to the greenhouse effect. ... For morphological image processing operations, see Erosion (morphology). ...

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. 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. In the southern hemisphere, there is some evidence for former permafrost from this period in central Otago and Argentine Patagonia, but was probably discontinuous. Temperature proxies for the last 40,000 years The Last Glacial Maximum refers to the time of maximum extent of the ice sheets during the last glaciation, approximately 21 thousand years ago. ... For other uses, see Europe (disambiguation). ... Szeged and the Tisza river. ... The shallow Sea of Azov is clearly distinguished from the deeper Black Sea. ... Peking redirects here. ... North America North America is a continent[1] in the Earths northern hemisphere and (chiefly) western hemisphere. ... An ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² (19,305 mile²).[1] The only current ice sheets are in Antarctica and Greenland; during the last ice age at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much... This article is about the U.S. state. ... Official language(s) English Capital Des Moines Largest city Des Moines Largest metro area Des Moines metropolitan area Area  Ranked 26th  - Total 56,272 sq mi (145,743 km²)  - Width 310 miles (500 km)  - Length 199 miles (320 km)  - % water 0. ... Official language(s) English Capital Jefferson City Largest city Kansas City Largest metro area St Louis[1] Area  Ranked 21st  - Total 69,709 sq mi (180,693 km²)  - Width 240 miles (385 km)  - Length 300 miles (480 km)  - % water 1. ... Otago (help· info) is one of the regions of New Zealand and lies in the south-east of the South Island. ... Patagonia, as most commonly defined (in orange). ...

Time to form deep permafrost

Time taken for permafrost to reach depth
Time (yr) Permafrost Depth (m)
1 4.44 (0.002759 mi.)
350 79.9 (0.049648 mi.)
3500 219.3
35000 461.4
100000 567.8
225000 626.5
775000 687.7

It has been calculated that the time required to form the deep permafrost underlying Prudhoe Bay, Alaska is 500,740 years. 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. 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. Prudhoe Bay (IPA: ) is a census-designated place (CDP) located in North Slope Borough in the U.S. state of Alaska. ... The Pleistocene epoch (IPA: ) on the geologic timescale is the period from 1,808,000 to 11,550 years BP. The Pleistocene epoch had been intended to cover the worlds recent period of repeated glaciations. ...

Construction on permafrost

Utility lines in a permafrost zone must be above ground
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. This problem has three common solutions. Using foundations on wood piles, building on a thick gravel pad (usually 1-2 meters/3.3-6.6 feet thick), or using anhydrous ammonia heat pipes. The Trans-Alaska Pipeline System uses insulated heat pipes to prevent the pipeline from sinking. Qingzang railway in Tibet was built using a variety of methods to keep the ground cool. Image File history File links Metadata No higher resolution available. ... Image File history File links Metadata No higher resolution available. ... A foundation is a structure that transmits loads from a building or road to the underlying ground. ... Look up Pile in Wiktionary, the free dictionary. ... Gravel (largest fragment in this photo is about 4 cm) Gravel is rock that is of a certain particle size range. ... A heat sink (aluminium) with heat pipe (copper) A heat pipe is a heat transfer mechanism that can transport large quantities of heat with a very small difference in temperature between the hot and cold interfaces. ... Map of the pipeline The Trans-Alaska Pipeline System (TAPS), usually called the Alyeska Pipeline in Alaska or the Alaska Pipeline elsewhere, is a major U.S. oil pipeline connecting oil fields in northern Alaska to a sea port where the oil can be shipped to the Lower 48 states... Map of the railway The worlds highest railway, which traverses the vast terrain of Tibet. ... This article is about historical/cultural Tibet. ...

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. At this depth the temperature does not change with the seasons, remaining at about -5 °C (23F). Yakutsk (Russian: ; Yakut: ) is a city in the Russian Far East, located about 4° (450 kilometres) below the Arctic Circle. ... Yakuts, self-designation: Sakha, are a Turkic people associated with the Sakha (Yakutia) Republic. ...


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See also

International Permafrost Association The International Permafrost Association (IPA), founded in 1983, has as its objectives to foster the dissemination of knowledge concerning permafrost and to promote cooperation among persons and national or international organisations engaged in scientific investigation and engineering work related to permafrost and seasonally frozen ground. ...

Permafrost Young Researchers Network The Permafrost Young Researcher’s Network (PYRN) is a network formed in 2005 to formally facilitate and strengthen contacts among young scientists in the permafrost community. ...

External links

  Results from FactBites:
Yukon Geological Survey- Permafrost Summary (1377 words)
Permafrost may be well over 300 m thick in the more westerly, unglaciated portions of the Yukon Coastal Plain (Rampton 1982), but it thins rapidly to the south, and is usually absent beneath glacial ice and lakes.
Permafrost in uplands of central and southern Yukon is a result of short, cool summers, for in winter the ground is protected by a thick snow cover.
Water may be injected into near-surface permafrost in autumn (Pollard and French 1984), and the growth of ice wedges by snowmelt infiltrating winter thermal contraction cracks, also contributes to high ice contents in the uppermost 10 m of the ground (Pollard and French 1980).
SOTC: Permafrost (890 words)
Permafrost underlies 12 to 18 percent of the exposed land surface in the Northern Hemisphere.
Permafrost occurs as far north as 84°N in northern Greenland, and as far south as 26°N in the Himalayas.
The IPA map shows the distribution of permafrost and ground ice for the continental land masses, areas of mountain and plateau permafrost, sub-sea and relict permafrost, relative abundance of ice wedges, massive ice bodies and pingos, and for ranges of permafrost temperature and thickness (Brown et al.
  More results at FactBites »



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