Ice cave
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2008-04-28T00:47:02Z
VoABot II
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BOT - Reverted edits by [[Special:Contributions/76.110.30.225|76.110.30.225]] {[[User:VoABot_II/Help#Revert_reasons|possible vandalism]]} to last version by [[Special:Contributions/Ian mckenzie|Ian mckenzie]].
::''This article is about caves that contain ice. For caves formed in ice, see [[glacier cave]].''
[[Image:Icemass2.jpg|thumb|350px|right|Ponded water ice inside an '''ice cave'''.]]The term '''ice cave''' refers to any type of natural [[cave]] (most commonly [[lava tubes]] or [[limestone]] caves) that contains significant amounts of perennial (year-round) [[ice]]. At least a portion of the cave must have a temperature below 0 °[[Celsius|C]] (32 °[[Fahrenheit|F]]) all year round, and [[water]] must have traveled into the cave’s cold zone.
The term '''ice cave''' is often used to describe a cavity formed ''within'' ice, which is properly called a [[glacier cave]].
==Temperature Mechanisms==
[[Bedrock]] caves are thermally [[insulated]] from the surface, so commonly assume a near-constant [[temperature]] approximating the annual average temperature at the surface. In some cold environments, average surface (and thus cave) temperatures are below freezing, and with surface water available in summer, ice caves are possible. However, many ice caves exist in [[temperate]] climates, due to mechanisms that result in cave temperatures being ''colder'' than average surface temperatures.
[[Image:Iceplate2.jpg|thumb|200px|left|[[Ice plate]]s]]''Cold traps'' - Certain cave configurations allow seasonal [[convection]] to import cold [[air]] from the surface in [[winter]], but not warm air in [[summer]]. A typical example is an underground chamber located below a single entrance. In winter, cold [[dense]] air settles into the cave, displacing any warmer air which rises and exits the cave. In summer, the cold cave air remains in place as the relatively warm surface air is lighter and cannot enter. The cave will only exchange air when the surface air is cooler than the cave air. Some cold traps may ensnare surface [[snow]] and shade it from the summer [[sun]]’s [[Sunlight|rays]], which may further contribute to the colder cave temperature.
''Permafrost'' - Even temperate environments can include pockets of bedrock that are below freezing year round, a condition called [[permafrost]]. For example, winter wind and an absence of snow cover may allow freezing deep enough to be protected from summer thaw, particularly in light-colored [[Rock (geology)|rock]] that does not readily absorb heat. Although the portion of a cave within this permafrost zone will be below freezing, permafrost generally does not allow water [[percolation]], so ice formations are often limited to [[Ice crystal|crystals]] from [[vapor]], and deeper cave passages may be arid and completely ice-free. Ice caves in permafrost need not be cold-traps (although some are), provided they do not draught significantly in summer.
''Evaporative cooling'' - In winter, dry surface air entering a moisture-saturated cave may have an additional cooling effect due to the [[latent heat]] of [[evaporation]]. This may create a zone within the cave that is cooler than the rest of the cave. Because many caves have seasonally-reversing draughts, the corresponding warming of the cave through [[condensation]] in summer may occur at a different location within the cave, but in any event a moisture-saturated cave environment is likely to experience much more [[evaporative cooling]] than condensative warming.
==Types of Ice in Ice Caves==
[[Image:Iceextrud.jpg|thumb|175px|right|Ice extrusions]]
Different freezing mechanisms result in visually and structurally distinct types of perennial cave ice.
''Ponded water'' - Surface water that collects and ponds in a cave before freezing will form a clear ice mass, and can be tens of metres thick and of great age. Large ice masses are plastic and can slowly flow in response to gravity or pressure from further accumulations. Sculpting from air flow and [[sublimation (chemistry)|sublimation]] may reveal ancient accumulation bands within the ice.
''Accumulated snow'' - Compressed under the weight of ongoing accumulations, snow sliding or falling into a cave entrance may eventually form ice that is coarsely crystalline, akin to [[glacier]] ice. True underground glaciers are rare.
''Ice formations'' - Water that freezes before ponding may form [[icicle]]s, ice-[[stalagmite]]s, [[ice column]]s or frozen [[waterfall]]s.
''Airborne moisture (water vapor)'' – Freezing vapor can form [[frost]] crystals, [[frost feather]]s and two-dimensional [[ice plate]]s on the cave walls and ceiling.
''Extrusions'' - Infiltrating water that freezes within the bedrock can sometimes be forced into the cave passage as ice extrusions.
''Intrusions'' - The weight of a surface glacier perched atop a cave entrance can force glacial ice a short distance into the cave. The only known examples of this phenomenon are the several 'ice plugs' at the back of [[Castleguard Cave]] in [[Alberta]].
==References==
Macdonald, W.D. ''Mechanisms for Ice Development in Ice Caves of Western [[North America]]'' [[The Canadian Caver]] 25/1 and 25/2, 1993
Rachlewicz, G., Szczuciński, W. "Seasonal, annual and decadal ice mass balance changes in Jaskinia Lodowa w Ciemniaku, the [[Tatra Mountains]], [[Poland]]" Theoretical and Applied [[Karstology]], 17: 11-18, 2004.
==External links==
* [http://users.unimi.it/icecaves/ Speleoglacio Ice Cave Research Group]
* [http://users.unimi.it/icecaves/citterio/papers/CITTERIO%20-%20Morphology%20LoLc1650%20-%20IAG2005%20-%20public.pdf An ice cave in Italy]
* [http://www.eisriesenwelt.at/ Eisriesenwelt Ice Cave photos] (click on "Gallery")
[[Category:Ice caves| ]]
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