Editing Permafrost (section)

== Manifestations ==
{| class="wikitable floatright" style="margin: 1em auto; text-align:center;"
|+ Time required for permafrost to reach depth at [[Prudhoe Bay, Alaska]]<ref name="Lunardini1995" />{{rp|35}}
! Time (yr) !! Permafrost depth
|-
| 1      || {{Convert|4.44|m|ft|abbr=on}}
|-
| 350    || {{Convert|79.9|m|ft|abbr=on}}
|-
| 3,500   || {{Convert|219.3|m|ft|abbr=on}}
|-
| 35,000  || {{Convert|461.4|m|ft|abbr=on}}
|-
| 100,000 || {{Convert|567.8|m|ft|abbr=on}}
|-
| 225,000 || {{Convert|626.5|m|ft|abbr=on}}
|-
| 775,000 || {{Convert|687.7|m|ft|abbr=on}}
|}

=== Base depth ===
Permafrost extends to a base depth where geothermal heat from the Earth and the mean annual temperature at the surface achieve an equilibrium temperature of {{convert|0|°C|°F|abbr=on}}.<ref name="Ostercamp-Burn2003">{{Cite book |last1=Osterkamp |first1=T. E. |last2=Burn |first2=C. R. |contribution=Permafrost |title=Encyclopedia of Atmospheric Sciences |year=2003 |editor-last=North |editor-first=Gerald R. |editor-last2=Pyle |editor-first2=John A. |editor-last3=Zhang |editor-first3=Fuqing |volume=4 |pages=1717–1729 |url=http://curry.eas.gatech.edu/Courses/6140/ency/Chapter11/Ency_Atmos/Permafrost.pdf |publisher=Elsevier |isbn=978-0-12-382226-0 |access-date=8 March 2016 |archive-url=https://web.archive.org/web/20161130124841/http://curry.eas.gatech.edu/Courses/6140/ency/Chapter11/Ency_Atmos/Permafrost.pdf |archive-date=30 November 2016 |url-status=live }}</ref> This base depth of permafrost can vary wildly – it is less than a meter (3&nbsp;ft) in the areas where it is shallowest,<ref name="IPADefinition" /> yet reaches {{convert|1493|m|ft|abbr=on}} in the northern [[Lena River|Lena]] and [[Yana River]] basins in [[Siberia]].<ref name="Desonie2008">{{cite book| last=Desonie |first=Dana |title=Polar Regions: Human Impacts |publisher=Chelsea Press |year=2008 |location= New York |isbn=978-0-8160-6218-8 |url=https://archive.org/details/polarregionshuma0000deso }}</ref> Calculations indicate that the formation time of permafrost greatly slows past the first several metres. For instance, over half a million years was required to form the deep permafrost underlying [[Prudhoe Bay, Alaska]], a time period extending over several glacial and interglacial cycles of the [[Pleistocene]].<ref name="Lunardini1995">{{cite report |last=Lunardini |first=Virgil J. |title=Permafrost Formation Time |date=April 1995 |work=CRREL Report 95-8 |publisher=US Army Corps of Engineers Cold Regions Research and Engineering Laboratory |id={{DTIC|ADA295515}} |location=Hanover NH }}</ref>{{rp|18}}

Base depth is affected by the underlying geology, and particularly by [[thermal conductivity]], which is lower for permafrost in soil than in [[bedrock]].<ref name="Ostercamp-Burn2003" /> Lower conductivity leaves permafrost less affected by the [[geothermal gradient]], which is the rate of increasing temperature with respect to increasing depth in the Earth's interior. It occurs as the Earth's internal [[thermal energy]] is generated by [[radioactive decay]] of unstable [[isotope]]s and flows to the surface by conduction at a rate of ~47 [[terawatts]] (TW).<ref>{{cite journal |last1=Davies |first1=J. H. |last2=Davies |first2=D. R. |date=22 February 2010 |title=Earth's surface heat flux |volume=1 |issue=1 |pages=5–24 |journal=Solid Earth |doi=10.5194/se-1-5-2010 |bibcode=2010SolE....1....5D |doi-access=free }}</ref> Away from tectonic plate boundaries, this is equivalent to an average heat flow of 25–30&nbsp;°C/km (124–139&nbsp;°F/mi) near the surface.<ref name="IPCC2008">{{cite report |first1=Ingvar B. |last1=Fridleifsson |first2=Ruggero |last2=Bertani |first3=Ernst |last3=Huenges |first4=John W. |last4=Lund |first5=Arni |last5=Ragnarsson |first6=Ladislaus |last6=Rybach |date=11 February 2008 |title=The possible role and contribution of geothermal energy to the mitigation of climate change |editor=O. Hohmeyer and T. Trittin |location=IPCC Scoping Meeting on Renewable Energy Sources, Luebeck, Germany |pages=59–80 |url=https://www.researchgate.net/publication/284685252 |access-date=27 September 2023 |archive-url=https://web.archive.org/web/20130312182133/http://ipcc.ch/pdf/supporting-material/proc-renewables-lubeck.pdf | archive-date=12 March 2013 }}</ref>

=== Massive ground ice ===
[[File:Coulombe 2019 ground ice diagram.png|thumb|Labelled example of a massive buried ice deposit in [[Bylot Island]], Canada<ref name="Coulombe2019" />]]

When the ice content of a permafrost exceeds 250 percent (ice to dry soil by mass) it is classified as massive ice. Massive ice bodies can range in composition, in every conceivable gradation from icy [[mud]] to pure ice. Massive icy beds have a minimum thickness of at least 2&nbsp;m and a short [[diameter]] of at least 10&nbsp;m.<ref name="Mackay1973">{{Cite conference |last=Mackay |first=J. Ross |title=Problems in the origins of massive icy beds, Western Arctic, Canada |conference=Permafrost: North American Contribution – Second International Conference |volume=2 |pages=223–228 |year=1973 |isbn=978-0-309-02115-9 |url=https://books.google.com/books?id=SjErAAAAYAAJ&pg=PA191 }}</ref> First recorded North American observations of this phenomenon were by European scientists at [[Canning River (Alaska)]] in 1919.<ref name="French2007">{{cite book |last=French |first=H. M. |title=The Periglacial Environment |publisher=Wiley |edition=3 |date=26 January 2007 |location=Chichester |chapter=5 |pages=83–115 |isbn=978-1-118-68493-1 |doi=10.1002/9781118684931.ch5 }}</ref> Russian literature provides an earlier date of 1735 and 1739 during the Great North Expedition by P. Lassinius and [[Khariton Laptev]], respectively. Russian investigators including I. A. Lopatin, B. Khegbomov, S. Taber and G. Beskow had also formulated the original theories for ice inclusion in freezing soils.<ref name="Shumskiy-Vtyurin1963">{{Cite conference |last1=Shumskiy |first1=P. A. |last2=Vtyurin |first2=B. I. |title=Underground ice |conference=Permafrost International Conference |issue=1287 |pages=108–113 |year=1963 |url=https://books.google.com/books?id=3jErAAAAYAAJ&q=utilidors+in+permafrost&pg=PA441 }}</ref>

While there are four categories of ice in permafrost – pore ice, ice wedges (also known as vein ice), buried surface ice and intrasedimental (sometimes also called constitutional<ref name="Shumskiy-Vtyurin1963" />) ice – only the last two tend to be large enough to qualify as massive ground ice.<ref name="Mackay1992">{{Cite journal |last1=Mackay |first1=J. R. |last2=Dallimore |first2=S. R. |title=Massive ice of Tuktoyaktuk area, Western Arctic coast, Canada |journal=Canadian Journal of Earth Sciences |volume=29 |issue=6 |pages=1234–1242 |doi=10.1139/e92-099 |year=1992 |bibcode=1992CaJES..29.1235M }}</ref><ref name="Lacelle2022">{{Cite journal |last1=Lacelle |first1=Denis |last2=Fisher |first2=David A. |last3=Verret |first3=Marjolaine |last4=Pollard |first4=Wayne |date=17 February 2022 |title=Improved prediction of the vertical distribution of ground ice in Arctic-Antarctic permafrost sediments |journal=Communications Earth & Environment |volume=3 |issue=31 |page=31 |doi=10.1038/s43247-022-00367-z |bibcode=2022ComEE...3...31L |s2cid=246872753 }}</ref> These two types usually occur separately, but may be found together, like on the coast of [[Tuktoyaktuk]] in western [[Arctic Canada]], where the remains of [[Laurentide Ice Sheet]] are located.<ref>{{cite journal |last1=Murton |first1=J. B. |last2=Whiteman |first2=C. A. |last3=Waller |first3=R. I. |last4=Pollard |first4=W. H. |last5=Clark |first5=I. D. |last6=Dallimore |first6=S. R. |date=12 August 2004 |title=Basal ice facies and supraglacial melt-out till of the Laurentide Ice Sheet, Tuktoyaktuk Coastlands, western Arctic Canada  |journal=Quaternary Science Reviews |volume=24 |issue=5–6 |pages=681–708 |doi=10.1016/S0277-3791(01)00149-4 }}</ref>

Buried surface ice may derive from snow, frozen lake or [[sea ice]], [[aufeis]] (stranded river ice) and even buried glacial ice from the former [[Pleistocene]] ice sheets. The latter hold enormous value for paleoglaciological research, yet even as of 2022, the total extent and volume of such buried ancient ice is unknown.<ref name="Coulombe2022">{{cite journal |last1=Coulombe |first1=Stephanie |last2=Fortier |first2=Daniel |last3=Bouchard |first3=Frédéric |last4=Paquette |first4=Michel |last5=Charbonneau |first5=Simon |last6=Lacelle |first6=Denis |last7=Laurion |first7=Isabelle |last8=Pienitz |first8=Reinhard |title=Contrasted geomorphological and limnological properties of thermokarst lakes formed in buried glacier ice and ice-wedge polygon terrain |journal=The Cryosphere |date=19 July 2022 |volume=16 |issue=7 |pages=2837–2857 |doi=10.5194/tc-16-2837-2022 |bibcode=2022TCry...16.2837C |doi-access=free }}</ref> Notable sites with known ancient ice deposits include [[Yenisei River]] valley in [[Siberia]], Russia as well as [[Banks Island|Banks]] and [[Bylot Island]] in Canada's [[Nunavut]] and [[Northwest Territories]].<ref>{{Cite journal |last1=Astakhov |first1=Valery I. |last2=Isayeva |first2=Lia L. |title=The 'Ice Hill': An example of 'retarded deglaciation' in siberia |journal=Quaternary Science Reviews |year=1988 |volume=7 |issue=1 |pages=29–40 |doi=10.1016/0277-3791(88)90091-1 |bibcode=1988QSRv....7...29A }}</ref><ref>{{Cite journal |last1=French |first1=H. M. |last2=Harry |first2=D. G. |title=Observations on buried glacier ice and massive segregated ice, western arctic coast, Canada |journal=Permafrost and Periglacial Processes |year=1990 |volume=1 |issue=1 |pages=31–43 |doi=10.1002/ppp.3430010105 |bibcode=1990PPPr....1...31F }}</ref><ref name="Coulombe2019">{{cite journal |last1=Coulombe |first1=Stephanie |last2=Fortier |first2=Daniel |last3=Lacelle |first3=Denis |last4=Kanevskiy |first4=Mikhail |last5=Shur  |first5=Yuri |title=Origin, burial and preservation of late Pleistocene-age glacier ice in Arctic permafrost (Bylot Island, NU, Canada) |journal=The Cryosphere |date=11 January 2019 |volume=13 |issue=1 |pages=97–111 |doi=10.5194/tc-13-97-2019 |bibcode=2019TCry...13...97C |doi-access=free }}</ref> Some of the buried ice sheet remnants are known to host [[Thermokarst#Thermokarst lakes|thermokarst lake]]s.<ref name="Coulombe2022" />

Intrasedimental or constitutional ice has been widely observed and studied across Canada. It forms when subterranean waters freeze in place, and is subdivided into intrusive, injection and segregational ice. The latter is the dominant type, formed after crystallizational differentiation in wet [[sediment]]s, which occurs when water migrates to the freezing front under the influence of [[van der Waals force]]s.<ref name="French2007" /><ref name="Mackay1973" /><ref name="Mackay1992" /> This is a slow process, which primarily occurs in [[silt]]s with [[salinity]] less than 20% of [[seawater]]: silt sediments with higher salinity and [[clay]] sediments instead have water movement prior to ice formation dominated by [[rheological]] processes. Consequently, it takes between 1 and 1000 years to form intrasedimental ice in the top 2.5 meters of clay sediments, yet it takes between 10 and 10,000 years for [[peat]] sediments and between 1,000 and 1,000,000 years for silt sediments.<ref name="Lacelle2022" />

[[File:Massive ice - retrogressive thaw slump - Herschel Island.png|thumb|center|900px|Cliff wall of a retrogressive thaw slump located on the southern coast of [[Herschel Island]] within an approximately {{convert|22|m|ft|adj=on}} by {{convert|1300|m|ft|adj=on}} headwall.]]

=== Landforms ===
{{See also|Patterned ground}}
Permafrost processes such as [[thermal contraction]] generating cracks which eventually become [[ice wedge]]s and [[solifluction]] – gradual movement of soil down the slope as it repeatedly freezes and thaws – often lead to the formation of ground polygons, rings, steps and other forms of [[patterned ground]] found in arctic, periglacial and alpine areas.<ref>{{cite journal |last1=Black |first1=Robert F. |year=1976 |title=Periglacial Features Indicative of Permafrost: Ice and Soil Wedges |journal=Quaternary Research |volume=6 |issue=1 |pages=3–26 |doi=10.1016/0033-5894(76)90037-5 |bibcode=1976QuRes...6....3B |s2cid=128393192 }}</ref><ref>{{cite journal |last1=Kessler |first1=M. A. |last2=Werner |first2=B. T. |title=Self-organization of sorted patterned ground |journal=Science |volume=299 |issue=5605 |pages=380–383 |date=17 January 2003 |pmid=12532013 |doi=10.1126/science.1077309 |bibcode=2003Sci...299..380K |s2cid=27238820 }}</ref> In ice-rich permafrost areas, melting of ground ice initiates [[thermokarst]] landforms such as [[thermokarst lake]]s, thaw slumps, thermal-erosion gullies, and active layer detachments.<ref>{{cite journal |last1=Li |first1=Dongfeng |last2=Overeem |first2=Irina |last3=Kettner |first3=Albert J. |last4=Zhou |first4=Yinjun |last5=Lu |first5=Xixi |title=Air Temperature Regulates Erodible Landscape, Water, and Sediment Fluxes in the Permafrost-Dominated Catchment on the Tibetan Plateau |journal=Water Resources Research |date=February 2021 |volume=57 |issue=2 |pages=e2020WR028193 |doi=10.1029/2020WR028193 |bibcode=2021WRR....5728193L |s2cid=234044271 }}</ref><ref>{{cite journal |last1=Zhang |first1=Ting |last2=Li |first2=Dongfeng |last3=Kettner |first3=Albert J. |last4=Zhou |first4=Yinjun |last5=Lu |first5=Xixi |title=Constraining Dynamic Sediment-Discharge Relationships in Cold Environments: The Sediment-Availability-Transport (SAT) Model |journal=Water Resources Research |date=October 2021 |volume=57 |issue=10 |pages=e2021WR030690 |doi=10.1029/2021WR030690 |bibcode=2021WRR....5730690Z |s2cid=242360211 }}</ref> Notably, unusually deep permafrost in Arctic [[moorland]]s and [[bog]]s often attracts meltwater in warmer seasons, which pools and freezes to form [[ice lense]]s, and the surrounding ground begins to jut outward at a slope. This can eventually result in the formation of large-scale land forms around this core of permafrost, such as [[palsa]]s – long ({{cvt|15|-|150|m|abbr=on|0}}), wide ({{cvt|10|-|30|m|abbr=on|0}}) yet shallow (<{{cvt|1|-|6|m|abbr=on|0}} tall) [[peat]] [[mound]]s – and the even larger [[pingo]]s, which can be {{cvt|3|-|70|m|abbr=on|0}} high and {{cvt|30|-|1000|m|abbr=on}} in [[diameter]].<ref>{{cite web|last=Pidwirny|first=M|title=Periglacial Processes and Landforms|url=http://www.physicalgeography.net/fundamentals/10ag.html|work=Fundamentals of Physical Geography|year=2006}}</ref><ref>{{Cite journal|last1=Kujala|first1=Kauko|last2=Seppälä |first2=Matti|last3=Holappa|first3=Teuvo|date=2008|title=Physical properties of peat and palsa formation |url=http://www.sciencedirect.com/science/article/pii/S0165232X07001644 |journal=Cold Regions Science and Technology|language=en|volume=52|issue=3|pages=408–414|doi=10.1016/j.coldregions.2007.08.002|bibcode=2008CRST...52..408K |issn=0165-232X}}</ref>

<gallery mode="packed" heights="150px">
File:Palsaaerialview.jpg|A group of [[palsa]]s, as seen from above, formed by the growth of ice lenses.
File:Injection ice in a pingo.jpg|Injection ice in a pingo, Mackenzie delta area.
File:Pingos near Tuk.jpg|[[Pingo]]s near [[Tuktoyaktuk]], [[Northwest Territories]], Canada
File:Permafrost - polygon.jpg|[[Patterned ground#Polygons|Ground polygons]]
File:Permafrost stone-rings hg.jpg|[[Patterned ground#Circles|Stone rings]] on [[Spitsbergen]]
File:Polygons in Padjelanta.jpg|[[Helicopter]] view of ground polygons and ice lenses at [[Padjelanta National Park]], Sweden
File:Ice-wedge hg.jpg|[[Ice wedge]]s seen from top
File:Permafrost soil-flow hg.jpg|[[Solifluction]] on [[Svalbard]]
File:Permafrost pattern.jpg|Contraction crack ([[ice wedge]]) polygons on Arctic sediment.
</gallery>

=== Ecology ===
[[File:Peat Plateau Complex.jpg|thumb|A peat plateau complex south of [[Fort Simpson]], [[Northwest Territories]].]]
Only plants with shallow [[root]]s can survive in the presence of permafrost. [[Black spruce]] tolerates limited rooting zones, and dominates [[flora]] where permafrost is extensive. Likewise, animal [[species]] which live in dens and [[burrow]]s have their habitat constrained by the permafrost, and these constraints also have a secondary impact on interactions between species within the [[ecosystem]].<ref>{{cite web |url=https://www.srs.fs.usda.gov/pubs/misc/ag_654/volume_1/picea/mariana.htm |title=Black Spruce |publisher=[[USDA]] |access-date=27 September 2023 }}</ref>

[[File:Storflaket.JPG|thumb|left|Cracks forming at the edges of the [[Storflaket]] permafrost bog in Sweden]]
While permafrost soil is frozen, it is not completely inhospitable to [[microorganism]]s, though their numbers can vary widely, typically from 1 to 1000&nbsp;million per gram of soil.<ref>{{cite journal | last1 = Hansen |display-authors=etal | year = 2007 | title = Viability, diversity and composition of the bacterial community in a high Arctic permafrost soil from Spitsbergen, Northern Norway | journal = Environmental Microbiology | volume = 9 | issue = 11| pages = 2870–2884 | doi=10.1111/j.1462-2920.2007.01403.x| pmid =  17922769|bibcode=2007EnvMi...9.2870H }}</ref><ref>{{cite journal | last1 = Yergeau |display-authors=etal  | year = 2010 | title = The functional potential of high Arctic permafrost revealed by metagenomic sequencing, qPCR and microarray analyses | journal = The ISME Journal | volume = 4 | issue = 9| pages = 1206–1214 | doi=10.1038/ismej.2010.41| pmid =  20393573| doi-access = free |bibcode=2010ISMEJ...4.1206Y }}</ref>
The [[permafrost carbon cycle]] (Arctic Carbon Cycle) deals with the transfer of carbon from permafrost soils to terrestrial vegetation and microbes, to the atmosphere, back to vegetation, and finally back to permafrost soils through burial and sedimentation due to cryogenic processes. Some of this carbon is transferred to the ocean and other portions of the globe through the global carbon cycle. The cycle includes the exchange of [[carbon dioxide]] and [[methane]] between terrestrial components and the atmosphere, as well as the transfer of carbon between land and water as methane, [[dissolved organic carbon]], [[dissolved inorganic carbon]], [[particulate inorganic carbon]] and [[particulate organic carbon]].<ref name=mcguire>{{Cite journal |doi=10.1890/08-2025.1 |author1=McGuire, A. D. |author2=Anderson, L. G. |author3=Christensen, T. R. |author4=Dallimore, S. |author5=Guo, L. |author6=Hayes, D. J. |author7=Heimann, M. |author8=Lorenson, T. D. |author9=Macdonald, R. W. |author10=Roulet, N. |title=Sensitivity of the carbon cycle in the Arctic to climate change |journal=Ecological Monographs |volume=79 |issue=4 |pages=523–555 |year=2009 |bibcode=2009EcoM...79..523M |hdl=11858/00-001M-0000-000E-D87B-C |s2cid=1779296 |hdl-access=free }}</ref>

Most of the bacteria and fungi found in permafrost cannot be cultured in the laboratory, but the identity of the microorganisms can be revealed by [[DNA]]-based techniques. For instance, analysis of 16S [[rRNA]] genes from late [[Pleistocene]] permafrost samples in eastern [[Siberia]]'s [[Kolyma Lowland]] revealed eight [[phylotype]]s, which belonged to the phyla [[Actinomycetota]] and [[Pseudomonadota]].<ref>{{Cite journal|last1=Kudryashova|first1=E. B.|last2=Chernousova|first2=E. Yu.|last3=Suzina|first3=N. E.|last4=Ariskina|first4=E. V.|last5=Gilichinsky|first5=D. A.|date=2013-05-01|title=Microbial diversity of Late Pleistocene Siberian permafrost samples|journal=Microbiology |volume=82|issue=3|pages=341–351 |doi=10.1134/S0026261713020082|s2cid=2645648 }}</ref>  "Muot-da-Barba-Peider", an alpine permafrost site in eastern Switzerland, was found to host a diverse microbial community in 2016. Prominent bacteria groups included phylum [[Acidobacteriota]], [[Actinomycetota]], AD3, [[Bacteroidota]], [[Chloroflexota]], [[Gemmatimonadota]], OD1, [[Nitrospirota]], [[Planctomycetota]], [[Pseudomonadota]], and [[Verrucomicrobiota]], in addition to [[eukaryotic]] fungi like [[Ascomycota]], [[Basidiomycota]], and [[Zygomycota]]. In the presently living species, scientists observed a variety of adaptations for sub-zero conditions, including reduced and anaerobic metabolic processes.<ref>{{Cite journal|last1=Frey|first1=Beat|last2=Rime|first2=Thomas|last3=Phillips|first3=Marcia|last4=Stierli|first4=Beat|last5=Hajdas|first5=Irka|last6=Widmer|first6=Franco|last7=Hartmann|first7=Martin|date=March 2016|editor-last=Margesin|editor-first=Rosa|title=Microbial diversity in European alpine permafrost and active layers|journal=FEMS Microbiology Ecology |volume=92|issue=3|pages=fiw018|doi=10.1093/femsec/fiw018|pmid=26832204 |doi-access=free}}</ref>

=== Construction on permafrost ===

There are only two large cities in the world built in areas of continuous permafrost (where the frozen soil forms an unbroken, below-zero sheet) and both are in Russia – [[Norilsk]] in [[Krasnoyarsk Krai]] and [[Yakutsk]] in the [[Sakha Republic]].<ref name="NY11022">{{cite magazine|author1=Joshua Yaffa|date=January 20, 2022|title=The Great Siberian Thaw|magazine=The New Yorker|url=https://www.newyorker.com/magazine/2022/01/17/the-great-siberian-thaw|access-date=January 20, 2022}}</ref> Building on permafrost is difficult because the heat of the building (or [[pipeline transport|pipeline]]) can spread to the soil, thawing it. As ice content turns to water, the ground's ability to provide structural support is weakened, until the building is destabilized. For instance, during the construction of the [[Trans-Siberian Railway]], a [[steam engine]] factory complex built in 1901 began to crumble within a month of operations for these reasons.<ref name="Chu2020" />{{rp|47}} Additionally, there is no [[groundwater]] available in an area underlain with permafrost. Any substantial settlement or installation needs to make some alternative arrangement to obtain water.<ref name="NY11022" /><ref name="Chu2020" />{{rp|25}}

A common solution is placing [[foundation (architecture)|foundations]] on wood [[Deep foundation|piles]], a technique pioneered by Soviet engineer [[Mikhail Kim]] in Norilsk.<ref>{{Cite magazine|last=Yaffa|first=Joshua|date=2022-01-07|title=The Great Siberian Thaw|url=https://www.newyorker.com/magazine/2022/01/17/the-great-siberian-thaw|access-date=2022-01-12|magazine=The New Yorker }}</ref> However, warming-induced change of [[friction]] on the piles can still cause movement through [[Creep (deformation)|creep]], even as the soil remains frozen.<ref>{{Cite book|last=Fang|first=Hsai-Yang|url=https://books.google.com/books?id=X8hEt3l1SPQC&q=foundations+on+permafrost&pg=PA735|title=Foundation Engineering Handbook|date=1990-12-31|publisher=Springer Science & Business Media|isbn=978-0-412-98891-2|page=735 }}</ref> The [[Melnikov Permafrost Institute]] in Yakutsk found that pile foundations should extend down to {{convert|15|m}} to avoid the risk of buildings sinking. At this depth the temperature does not change with the seasons, remaining at about {{convert|-5|C}}.<ref>{{Cite book|last1=Sanger|first1=Frederick J.|url=https://books.google.com/books?id=YDArAAAAYAAJ&q=yakutsk+pile+foundations+on+permafrost&pg=PA786|title=Permafrost: Second International Conference, July 13–28, 1973 : USSR Contribution|last2=Hyde|first2=Peter J.|date=1978-01-01|publisher=National Academies|isbn=978-0-309-02746-5|page=786 }}</ref>

Two other approaches are building on an extensive [[gravel]] pad (usually {{cvt|1-2|m}} thick); or using [[anhydrous ammonia]] [[heat pipe]]s.<ref name="ASCE">{{cite book |last=Clarke |first=Edwin S. |title=Permafrost Foundations—State of the Practice |series=Monograph Series |publisher=American Society of Civil Engineers |year=2007 |url=https://books.google.com/books?id=O-voTug5apsC&pg=PA34 |isbn=978-0-7844-0947-3}}</ref> The [[Trans-Alaska Pipeline System]] uses [[Heat pipe#Permafrost cooling|heat pipes built into vertical supports]] to prevent the pipeline from sinking and the [[Qingzang railway]] in Tibet employs a variety of methods to keep the ground cool, both in areas with [[Frost heaving#Frost-susceptible soils|frost-susceptible soil]]. Permafrost may necessitate special enclosures for buried utilities, called "[[Utility tunnel#In Arctic towns|utilidors]]".<ref>{{Cite book|last=Woods|first=Kenneth B.|url=https://books.google.com/books?id=3jErAAAAYAAJ&q=utilidors+in+permafrost&pg=PA441|title=Permafrost International Conference: Proceedings|date=1966|publisher=National Academies|pages=418–57 }}</ref>

{{Clear}}
<gallery mode="packed" heights="150px">
File:PICT4417Sykhus.JPG|A building on elevated piles in permafrost zone.
File:Trans-Alaska Pipeline (1).jpg|[[Heat pipe#Permafrost cooling|Heat pipes in vertical supports]] maintain a frozen bulb around portions of the [[Trans-Alaska Pipeline]] that are at risk of thawing.<ref>{{Cite web |url=http://apps.dtic.mil/dtic/tr/fulltext/u2/a073597.pdf |title=C. E. Heuer, "The Application of Heat Pipes on the Trans-Alaska Pipeline" Special Report 79-26, United States Army Corps of Engineers, Sept. 1979. |access-date=2013-10-22 |archive-date=2013-10-22 |archive-url=https://web.archive.org/web/20131022022419/http://www.dtic.mil/dtic/tr/fulltext/u2/a073597.pdf |url-status=live }}</ref>
File:Yakoutsk Construction d'immeuble.jpg|Pile foundations in [[Yakutsk]], a city underlain with continuous permafrost.
File:Raised pipes in permafrost.jpg|[[District heating]] pipes run above ground in Yakutsk.
</gallery>