An ice cave is any type of natural cave that contains significant amounts of perennial ice. At least a portion of the cave must have a temperature below 0 °C all year round, water must have traveled into the cave’s cold zone; this type of cave was first formally described by Englishman Edwin Swift Balch in 1900, who suggested the French term glacieres should be used for them though the term ice cave was as now used to refer to caves containing year-round ice. Among speleologists, ice cave is the proper English term. A cavity formed within ice is properly called a glacier cave. Ice caves occur as static ice caves, such as Durmitor Ice Cave, dynamic or cyclical ice caves, such as Eisriesenwelt. In most of the world, bedrock caves are thermally insulated from the surface and so assume a near-constant temperature approximating the annual average temperature at the surface. In some cold environments, such as that surrounding Mount Erebus, average surface temperatures are below freezing, with surface water available in summer, ice caves are possible and are sometimes overlain by fumarolic ice towers However, many ice caves exist in temperate climates, due to mechanisms that result in cave temperatures being colder than average surface temperatures where they formed.
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 warm surface air is lighter and cannot enter; the cave will only exchange 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 in light-colored rock that does not absorb heat. Although the portion of a cave within this permafrost zone will be below freezing, permafrost does not allow water percolation, so ice formations are limited to crystals from vapor, deeper cave passages may be arid and ice-free.
Ice caves in permafrost need not be cold-traps, provided they do not draught 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, 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 to experience much more evaporative cooling than condensative warming. 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, can be tens of metres thick and of great age. Large ice masses are plastic and can 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 form ice, 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 – Freezing vapor can form frost crystals, frost feathers and two-dimensional ice plates on the cave walls and ceiling. Needle ice - Infiltrating water that freezes within the bedrock can sometimes be forced into the cave passage. 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. Bandera Volcano Ice Cave Bixby State Preserve Booming Ice Chasm Bortig Pit Cave Canyon Creek Ice Cave Castleguard Cave Coudersport Ice Mine Decorah Ice Cave State Preserve Demänovská Ice Cave Dobšinská Ice Cave UNESCO World Heritage site Eisriesenwelt Grotte Casteret Ice Mountain Kungur Ice Cave Narusawa Ice Cave, Niter Ice Cave Sam's Point Preserve Scărișoara Cave Shawangunk Ridge Speilsalen collapsed in 2007 Víðgelmir 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 and decadal ice mass balance changes in Jaskinia Lodowa w Ciemniaku, the Tatra Mountains, Poland Theoretical and Applied Karstology, 17: 11-18, 2004.. The Virtual Cave: Ice Formations in Ice Caves goodearthgraphics.com Video of an ice cave in the Big Snowy Mountains of Montana YouTube video
Hair ice known as ice wool or frost beard, is a type of ice that forms on dead wood and takes the shape of fine, silky hair. It is somewhat uncommon, has been reported at latitudes between 45–55 °N in broadleaf forests; the meteorologist and discoverer of continental drift, Alfred Wegener, described hair ice on wet dead wood in 1918, assuming some specific fungi as the catalyst, a theory confirmed by Gerhart Wagner and Christian Mätzler in 2005. In 2015, the fungus Exidiopsis effusa was identified as key to the formation of hair ice. Hair ice forms on moist, rotting wood from broadleaf trees when temperatures are under 0 °C and the air is humid; each of the smooth, silky hairs has a length of up to 20 cm. The hairs take the shape of curls and waves, they can maintain their shape for hours and sometimes days. This long lifetime indicates that something is preventing the small ice crystals from recrystallizing into larger ones, since recrystallization occurs quickly at temperatures near 0 °C; the hairs appear to root at the mouth of wood rays, their thickness is similar to the diameter of the wood ray channels.
A piece of wood that produces hair ice once may continue to produce it over several years. In the year 2015, German and Swiss scientists identified the fungus Exidiopsis effusa as key to the formation of hair ice; the fungus was found on every hair ice sample examined by the researchers, disabling the fungus with fungicide or hot water prevented hair ice formation. The fungus shapes the ice into fine hairs through an uncertain mechanism and stabilizes it by providing a recrystallization inhibitor similar to antifreeze proteins. Needle ice Frost flower Hair ice photos for WDR 5 Leonardo feature Video footage of Hair Ice with narration
An ice cap is a mass of ice that covers less than 50,000 km2 of land area. Larger ice masses covering more than 50,000 km2 are termed ice sheets. Ice caps are not constrained by topographical features. By contrast, ice masses of similar size that are constrained by topographical features are known as ice fields; the dome of an ice cap is centred on the highest point of a massif. Ice flows away from this high point towards the ice cap's periphery. Ice caps have significant effects on the geomorphology of the area. Plastic moulding and other glacial erosional features become present upon the glacier's retreat. Many lakes, such as the Great Lakes in North America, as well as numerous valleys have been formed by glacial action over hundreds of thousands of years. On Earth, there are about 30 million km3 of total ice mass; the average temperature of an ice mass ranges between −20 °C and −30 °C. The core of an ice cap exhibits a constant temperature that ranges between −15 °C and −20 °C. A high-latitude region covered in ice, though not an ice cap, are called polar ice caps.
Vatnajökull is an example of an ice cap in Iceland
Ice XI is the hydrogen-ordered form of Ih, the ordinary form of ice. Different phases of ice, from ice II to ice XVI, have been created in the laboratory at different temperatures and pressures; the total internal energy of ice XI is about one sixth lower than ice Ih, so in principle it should form when ice Ih is cooled to below 72 K. The low temperature required to achieve this transition is correlated with the low energy difference between the two structures. Water molecules in ice Ih are surrounded by four semi-randomly directed hydrogen bonds; such arrangements should change to the more ordered arrangement of hydrogen bonds found in ice XI at low temperatures, so long as localized proton hopping is sufficiently enabled. Correspondingly, ice XI is believed to have a triple point with hexagonal ice and gaseous water at. Ice XI has an orthorhombic structure with space group Cmc21 containing eight molecules per unit cell, its lattice parameters are a=4.465 Å, b=7.859 Å, c=7.292 Å at 5 K. There are 16 crystallographically inequivalent hydrogen-ordered configurations of ice with an orthorhombic structure of eight atoms per unit cell, but electronic structure calculations show Cmc21 to be the most stable.
Another possible configuration, with space group Pna21 is of interest, as it is an antiferroelectric crystal, which Davidson and Morokuma incorrectly suggested as the most stable structure in 1984. In practice, ice XI is most prepared from a dilute KOH solution kept just below 72 K for about a week; the hydroxide ions create defects in the hexagonal ice, allowing protons to jump more between the oxygen atoms. More each hydroxide ion creates a Bjerrum L defect and an ionized vertex. Both the defect and the ion can ` assist' with proton reordering; the positive K+ ion may play a role because it is found that KOH works better than other alkali hydroxides. The exact details of these ordering mechanisms are still poorly understood and under question because experimentally the mobility of the hydroxide and K+ ions appear to be low around 72 K; the current belief is that KOH acts only to assist with the hydrogen reordering and is not required for the lower-energy stability of ice XI. However, calculations by Toshiaki Iitaka in 2010 call this into question.
Iitaka argues that the KOH ions compensate for the large net electric dipole moment of the crystal lattice along the c-axis. The aforementioned electronic structure calculations are done assuming an infinite lattice and ignore the effects of macroscopic electric fields created by surface charges; because such fields are present in any finite size crystal, in non-doped ice XI, domains of alternating dipole moment should form as in conventional ferroelectrics. It has been suggested that the ice Ih => ice XI transition is enabled by the tunneling of protons. Although ice XI is thought to be a more stable conformation than ice Ih, the transformation is slow. According to one report, in Antarctic conditions it is estimated to take at least 100,000 years to form without the assistance of catalysts. Ice XI was sought and found in Antarctic ice, about 100 years old in 1998. A further study in 2004 was not able to reproduce this finding, after studying Antarctic ice, around 3000 years old; the 1998 Antarctic study claimed that the transformation temperature is −36 °C, far higher than the temperature of the expected triple point mentioned above.
Ice XI was found in experiments using pure water at low temperature and low pressure – conditions thought to be present in the upper atmosphere. Small domains of ice XI were found to form in pure water. Ice Ih, transformed to ice XI and back to ice Ih, on raising the temperature, retains some hydrogen-ordered domains and more transforms back to ice XI again. A neutron powder diffraction study found that small hydrogen-ordered domains can exist up to 111 K. There are distinct differences in the Raman spectra between ices Ih and XI, with ice XI showing much stronger peaks in the translational, librational and in-phase asymmetric stretch regions. Ice Ic has a proton-ordered form; the total internal energy of ice XIc was predicted as similar as ice XIh Hints of hydrogen-ordering in ice had been observed as early as 1964, when Dengel et al. attributed a peak in thermo-stimulated depolarization current to the existence of a proton-ordered ferroelectric phase. However, they could not conclusively prove that a phase transition had taken place, Onsager pointed out that the peak could arise from the movement of defects and lattice imperfections.
Onsager suggested that experimentalists look for a dramatic change in heat capacity by performing a careful calorimetric experiment. A phase transition to Ice XI was first identified experimentally in 1972 by others. Ice XI is ferroelectric. To qualify as a ferroelectric it must exhibit polarization switching under an electric field, which has not been conclusively demonstrated but, implicitly assumed to be possible. Cubic ice has a ferrolectric phase and in this case the ferroelectric properties of the ice have been experimentally demonstrated on monolayer thin films. In a similar experiment, ferroelectric layers of hexagonal ice were grown on a platinum surface; the material had a polar
Black ice, sometimes called clear ice, is a thin coating of glaze ice on a surface on roads. The ice itself is not black, but visually transparent, allowing the black road below to be seen through it; the low levels of noticeable ice pellets, snow, or sleet surrounding black ice means that areas of the ice are practically invisible to drivers or people stepping on it. There is, thus, a risk of slippage and subsequent accident due to the unexpected loss of traction; the term "black ice" in the United States is incorrectly used to describe any type of ice that forms on roadways when standing water on roads turns to ice as the temperature falls below freezing. Defined, black ice is formed on dry roads, rendering it invisible to drivers, it occurs when the textures present in all pavements slightly below the top of the road surface contain water or moisture, thereby presenting a dry surface to tires until that water or moisture freezes and expands. Three other definitions of black ice by the World Meteorological Organization are: A thin ice layer on a fresh or salt water body which appears dark in colour because of its transparency.
The American Meteorological Society Glossary of Meteorology includes the definition of black ice as "a thin sheet of ice dark in appearance, may form when light rain or drizzle falls on a road surface, at a temperature below 0 °C." Because it represents only a thin accumulation, black ice is transparent and thus difficult to see as compared with snow, frozen slush, or thicker ice layers. In addition, it is interleaved with wet pavement, nearly identical in appearance; this condition makes driving, cycling or walking on affected surfaces dangerous. Deicing with salt is effective down to temperatures of about −18 °C. Other compounds such as magnesium chloride or calcium chloride have been used for cold temperatures since the freezing-point depression of their solutions is lower. At low temperatures, black ice can form on roadways when the moisture from automobile exhaust condenses on the road surface; such conditions caused multiple accidents in Minnesota when the temperatures dipped below −18 °C for a prolonged period of time in mid-December 2008.
Salt's ineffectiveness at melting ice at these temperatures compounds the problem. Black ice may form when the ambient temperature is several degrees above the freezing point of water 0 °C, if the air warms after a prolonged cold spell that has left the surface of the roadway well below the freezing point temperature. On December 1, 2013, heavy post-Thanksgiving weekend traffic encountered black ice on the westbound I-290 expressway in Worcester, Massachusetts. A chain reaction series of crashes resulted, involving three tractor-trailers and over 60 other vehicles; the ice formed on a long downward slope, surprising drivers coming over the crest of a hill, who could not see crashed vehicles ahead until it was too late to stop on the slick pavement. Bridges and overpasses can be dangerous. Black ice forms first on bridges and overpasses because air can circulate both above and below the surface of the elevated roadway when the ambient temperature drops, causing the bridge pavement temperature to fall more rapidly.
In the United States, road warning signs with the advisory Bridge May Be Icy indicate dangerous roadways above bridge structures. Similar road signs exists throughout Canada, but warnings sometimes appear without words to comply to bilingual requirements; the Canadian sign features a vehicle with skid marks and snow flakes. The same sign's official and undisclosed description is defined as "Pavement is slippery when wet". Additional signs may be attached with various different wording in Canadian provinces that do not have bilingual requirements: Bridge Ices Slippery When Wet Road Ices Slippery When Frosty Icy Bridge Deck Bridge Ices Before Road The I-35W Mississippi River bridge in Minneapolis, was well known for its black ice before it collapsed in 2007 into the Mississippi River, it had caused several pileups during its 40-year life. On December 19, 1985, the temperature reached −34 °C. Cars crossing the bridge experienced black ice and there was a massive pile up of crashed vehicles on the bridge on the northbound side.
In February and in December 1996, the bridge was identified as the single most treacherous cold-weather spot in the local freeway system, because of the frictionless thin layer of black ice that formed when temperatures dropped below freezing. The bridge's proximity to Saint Anthony Falls contributed to the icing problem and the site was noted for frequent spinouts and collisions. By January 1999, Mn/DOT began testing magnesium chloride solutions and a mixture of magnesium chloride and a corn-processing byproduct to see whether either would reduce the black ice that appeared on the bridge during the winter months. In October 1999, the state embedded temperature-activated nozzles in the bridge deck to spray the bridge with potassium acetate solution to keep the area free of winter black ice; the system came into operation in 2000. When the temperature is below freezing and the wind is calm, such as under a high atmospheric pressure at night in the fall, a thin layer of ice will form over open water of a lake.
If the depth of the body of water is large enough, its color is black and can be seen through the ice, thus
Diamond dust is a ground-level cloud composed of tiny ice crystals. This meteorological phenomenon is referred to as ice crystals and is reported in the METAR code as IC. Diamond dust forms under otherwise clear or nearly clear skies, so it is sometimes referred to as clear-sky precipitation. Diamond dust is most observed in Antarctica and the Arctic, but can occur anywhere with a temperature well below freezing. In the polar regions of Earth, diamond dust may persist for several days without interruption. Diamond dust is similar to fog in. Fog refers to a cloud composed of liquid water. Fog is a dense enough cloud to reduce visibility, while diamond dust is very thin and may not have any effect on visibility. However, diamond dust can reduce the visibility, in some cases to under 600 m; the depth of the diamond dust layer can vary from as little as 20 to 30 m to 300 metres. Because diamond dust does not always reduce visibility it is first noticed by the brief flashes caused when the tiny crystals, tumbling through the air, reflect sunlight to the eye.
This glittering effect gives the phenomenon its name since it looks like many tiny diamonds are flashing in the air. Serial photos of Diamond Dust These ice crystals form when a temperature inversion is present at the surface and the warmer air above the ground mixes with the colder air near the surface. Since warmer air contains more water vapor than colder air, this mixing will also transport water vapor into the air near the surface, causing the relative humidity of the near-surface air to increase. If the relative humidity increase near the surface is large enough ice crystals may form. To form diamond dust the temperature must be below the freezing point of water, 0 °C, or the ice cannot form or would melt. However, diamond dust is not observed at temperatures near 0 °C. At temperatures between 0 °C and about −39 °C increasing the relative humidity can cause either fog or diamond dust; this is because small droplets of water can remain liquid well below the freezing point, a state known as supercooled water.
In areas with a lot of small particles in the air, from human pollution or natural sources like dust, the water droplets are to be able to freeze at a temperature around −10 °C, but in clean areas, where there are no particles to help the droplets freeze, they can remain liquid to −39 °C, at which point very tiny, pure water droplets will freeze. In the interior of Antarctica diamond dust is common at temperatures below about −25 °C. Artificial diamond dust can form from snow machines; these are found at ski resorts. Diamond dust is associated with halos, such as sun dogs, light pillars, etc. Like the ice crystals in cirrus or cirrostratus clouds, diamond dust crystals form directly as simple hexagonal ice crystals — as opposed to freezing drops — and form slowly; this combination results in crystals with well defined shapes - either hexagonal plates or columns - which, like a prism, can reflect and/or refract light in specific directions. While diamond dust can be seen in any area of the world that has cold winters, it is most frequent in the interior of Antarctica, where it is common year-round.
Schwerdtfeger shows that diamond dust was observed on average 316 days a year at Plateau Station in Antarctica, Radok and Lile estimate that over 70% of the precipitation that fell at Plateau Station in 1967 fell in the form of diamond dust. Once melted, the total precipitation for the year was only 25 mm. Diamond dust may sometimes cause a problem for automated airport weather stations; the ceilometer and visibility sensor do not always interpret the falling diamond dust and report the visibility and ceiling as zero. However, a human observer would notice clear skies and unrestricted visibility; the METAR identifier for diamond dust within international hourly weather reports is IC. Crepuscular rays Halo Light beam Light pillar Sun dog False sunrise False sunset Greenler, R.. Rainbows and Glories. Milwaukee: Peanut Butter Publishing. Pp. 195 pp. ISBN 0-89716-926-3. — An excellent reference for optical phenomena including photos of displays in Antarctica caused by diamond dust. Schwerdtfeger, W..
"The climate of the Antarctic". In S. Orvig. Climates of the Polar Regions. World Survey of Climatology. Vol. 14. Elsevier. Pp. 253–355. ISBN 0-444-40828-2. Radok, U. and R. C. Lile. "A year of snow accumulation at Plateau Station". In J. A. Businger. Meteorological Studies at Plateau Station, Antarctica. Antarctic Research Series. Vol. 25. American Geophysical Union. Pp. 17–26. ISBN 0-87590-125-5. Manual of Surface Weather Observations. Atmospheric Environment Service of Canada. Photo of artificial Diamond Dust A remarkable video filmed in Japan. 1min 22sec HQ Longer version of the above video. 5min 10sec HD Note that images are different from naked eye in that they capture out-of-focus crystals which are shown as large, blurred objects. By naked eye, Diamond dust looks more like the photo below: A night photo that presents closer to naked eye observation
Ice is water frozen into a solid state. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color. In the Solar System, ice is abundant and occurs from as close to the Sun as Mercury to as far away as the Oort cloud objects. Beyond the Solar System, it occurs as interstellar ice, it is abundant on Earth's surface – in the polar regions and above the snow line – and, as a common form of precipitation and deposition, plays a key role in Earth's water cycle and climate. It occurs as frost, icicles or ice spikes. Ice molecules can exhibit more different phases that depend on temperature and pressure; when water is cooled up to three different types of amorphous ice can form depending on the history of its pressure and temperature. When cooled correlated proton tunneling occurs below −253.15 °C giving rise to macroscopic quantum phenomena. All the ice on Earth's surface and in its atmosphere is of a hexagonal crystalline structure denoted as ice Ih with minute traces of cubic ice denoted as ice Ic.
The most common phase transition to ice Ih occurs when liquid water is cooled below 0 °C at standard atmospheric pressure. It may be deposited directly by water vapor, as happens in the formation of frost; the transition from ice to water is melting and from ice directly to water vapor is sublimation. Ice is used in a variety including cooling, winter sports and ice sculpture; as a occurring crystalline inorganic solid with an ordered structure, ice is considered to be a mineral. It possesses a regular crystalline structure based on the molecule of water, which consists of a single oxygen atom covalently bonded to two hydrogen atoms, or H–O–H. However, many of the physical properties of water and ice are controlled by the formation of hydrogen bonds between adjacent oxygen and hydrogen atoms. An unusual property of ice frozen at atmospheric pressure is that the solid is 8.3% less dense than liquid water. The density of ice is 0.9167–0.9168 g/cm3 at 0 °C and standard atmospheric pressure, whereas water has a density of 0.9998–0.999863 g/cm3 at the same temperature and pressure.
Liquid water is densest 1.00 g/cm3, at 4 °C and becomes less dense as the water molecules begin to form the hexagonal crystals of ice as the freezing point is reached. This is due to hydrogen bonding dominating the intermolecular forces, which results in a packing of molecules less compact in the solid. Density of ice increases with decreasing temperature and has a value of 0.9340 g/cm3 at −180 °C. When water freezes, it increases in volume; the effect of expansion during freezing can be dramatic, ice expansion is a basic cause of freeze-thaw weathering of rock in nature and damage to building foundations and roadways from frost heaving. It is a common cause of the flooding of houses when water pipes burst due to the pressure of expanding water when it freezes; the result of this process is that ice floats on liquid water, an important feature in Earth's biosphere. It has been argued that without this property, natural bodies of water would freeze, in some cases permanently, from the bottom up, resulting in a loss of bottom-dependent animal and plant life in fresh and sea water.
Sufficiently thin ice sheets allow light to pass through while protecting the underside from short-term weather extremes such as wind chill. This creates a sheltered environment for algal colonies; when sea water freezes, the ice is riddled with brine-filled channels which sustain sympagic organisms such as bacteria, algae and annelids, which in turn provide food for animals such as krill and specialised fish like the bald notothen, fed upon in turn by larger animals such as emperor penguins and minke whales. When ice melts, it absorbs as much energy as it would take to heat an equivalent mass of water by 80 °C. During the melting process, the temperature remains constant at 0 °C. While melting, any energy added breaks the hydrogen bonds between ice molecules. Energy becomes available to increase the thermal energy only after enough hydrogen bonds are broken that the ice can be considered liquid water; the amount of energy consumed in breaking hydrogen bonds in the transition from ice to water is known as the heat of fusion.
As with water, ice absorbs light at the red end of the spectrum preferentially as the result of an overtone of an oxygen–hydrogen bond stretch. Compared with water, this absorption is shifted toward lower energies. Thus, ice appears blue, with a greener tint than liquid water. Since absorption is cumulative, the color effect intensifies with increasing thickness or if internal reflections cause the light to take a longer path through the ice. Other colors can appear in the presence of light absorbing impurities, where the impurity is dictating the color rather than the ice itself. For instance, icebergs containing impurities can appear grey or green. Ice may be any one of the 18 known solid crystalline phases of water, or in an amorphous solid state at various densities. Most liquids under increased pressure freeze at higher temperatures because the pressure helps to hold the molecules together. However, the strong hydrogen bonds in water make it different: For some pressures higher than 1 atm, water freezes at a temperature below