Everything about Ice Cave totally explained
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This article is about caves that contain ice. For caves formed in ice, see glacier 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 °
C (32 °
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.
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 can't 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
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 that doesn't readily absorb heat. Although the portion of a cave within this permafrost zone will be below freezing, permafrost generally doesn't allow water
percolation, so ice formations are often limited to
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 don't 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's 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
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 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's coarsely crystalline, akin to
glacier ice. True underground glaciers are rare.
Ice formations - Water that freezes before ponding may form
icicles, ice-
stalagmites,
ice columns or frozen
waterfalls.
Airborne moisture (water vapor) – Freezing vapor can form
frost crystals,
frost feathers and two-dimensional
ice plates 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.
Further Information
Get more info on 'Ice Cave'.
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