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Ice is
water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , even though it provide ...

water
frozen
frozen
into a
solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformation (mechanics), deforms (flows) under an applied ...

solid
state. Depending on the presence of
impurities Impurities are chemical substance A chemical substance is a form of matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday objects that can be touched are ...
such as particles of soil or bubbles of air, it can appear transparent or a more or less
opaque Opacity or opaque may refer to: * Impediments to (especially, visible) light: ** Opacities, absorption coefficients ** Opacity (optics), property or degree of blocking the transmission of light * Metaphors derived from literal optics: ** Opaque con ...
bluish-white color. In the
Solar System The Solar SystemCapitalization Capitalization ( North American English) or capitalisation ( British English) is writing a word with its first letter as a capital letter (uppercase letter) and the remaining letters in lower case, in writin ...

Solar System
, ice is abundant and occurs naturally from as close to the Sun as
Mercury Mercury usually refers to: * Mercury (planet) Mercury is the smallest planet in the Solar System and the closest to the Sun. Its orbit around the Sun takes 87.97 Earth days, the shortest of all the Sun's planets. It is named after the Roman g ...

Mercury
to as far away as the
Oort cloud The Oort cloud (), sometimes called the Öpik–Oort cloud, first described in 1950 by the Dutch astronomer An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of ...

Oort cloud
objects. Beyond the Solar System, it occurs as
interstellar iceInterstellar ice consists of grains of volatiles Volatiles are the group of chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure ...
. It is abundant on
Earth Earth is the third planet from the Sun and the only astronomical object known to harbour and support life. 29.2% of Earth's surface is land consisting of continents and islands. The remaining 70.8% is Water distribution on Earth, covered wit ...

Earth
's surfaceparticularly in the polar regions and above the
snow line The climatic snow line is the boundary between a snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further chang ...
and, as a common form of
precipitation In meteorology Meteorology is a branch of the (which include and ), with a major focus on . The study of meteorology dates back , though significant progress in meteorology did not begin until the 18th century. The 19th century saw mod ...

precipitation
and
deposition Deposition may refer to: * Deposition (law), taking testimony outside of court * List of deposed politicians, Deposition (politics), the removal of a person of authority from political power * Deposition (university), a widespread initiation ritual ...
, plays a key role in Earth's
water cycle The water cycle, also known as the hydrologic cycle or the hydrological cycle, describes the continuous movement of water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, ...

water cycle
and
climate Climate is the long-term pattern of weather Weather is the state of the atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a la ...

climate
. It falls as snowflakes and hail or occurs as frost, icicles or
ice spike An ice spike is an ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abundant and occurs naturally from ...

ice spike
s and aggregates from snow as
glaciers A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glaciers
and ice sheets. Ice exhibits at least eighteen
phase Phase or phases may refer to: Science * State of matter, or phase, one of the distinct forms in which matter can exist *Phase (matter) In the physical sciences, a phase is a region of space (a thermodynamic system A thermodynamic system is a ...
s (
packing geometries
packing geometries
), depending on temperature and pressure. When water is cooled rapidly (
quenching 250px, Coke being pushed into a quenching car, Hanna furnaces of the Great Lakes Steel Corporation, Detroit, Michigan, November 1942 In materials science The Interdisciplinarity, interdisciplinary field of materials science, also commonly terme ...

quenching
), up to three types of
amorphous ice Amorphous ice (non-crystalline or "vitreous" ice) is an amorphous solid In condensed matter physics and materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the ...
can form depending on its history of pressure and temperature. When cooled slowly, correlated proton tunneling occurs below (, ) giving rise to
macroscopic quantum phenomena Macroscopic quantum phenomena are processes showing quantum behavior at the macroscopic scale, rather than at the atomic scale where quantum effects are prevalent. The best-known examples of macroscopic quantum phenomena are superfluidity and su ...
. Virtually all ice on Earth's surface and in its atmosphere is of a
hexagonal In geometry, a hexagon (from Ancient Greek, Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon or 6-gon. The total of the internal angles of any simple polygon, simple (non-self-intersecting) hexagon is 720°. Regul ...
crystalline structure In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived from the Greek words ''crystallon'' "cold drop, frozen ...

crystalline structure
denoted as ice Ih (spoken as "ice one h") with minute traces of cubic ice, denoted as ice Ic and, more recently found,
Ice VII Ice VII is a cubic crystalline form of ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abundant and occ ...
inclusions in diamonds. The most common
phase transition In , , and many other related fields, phase transitions (or phase changes) are the of transition between a state of a medium, identified by some parameters, and another one, with different values of the parameters. Commonly the term is used to ...
to ice Ih occurs when liquid water is cooled below (, ) at
standard atmospheric pressure The standard atmosphere (symbol: atm) is a unit Unit may refer to: Arts and entertainment * UNIT Unit may refer to: Arts and entertainment * UNIT, a fictional military organization in the science fiction television series ''Doctor Who'' * Unit ...
. It may also be deposited directly by
water vapor (99.9839 °C) , - , , , - , , 461.5 /(·K) , - , , 2.27 /kg , - , , 1.864 /(kg·K) Water vapor, water vapour or aqueous vapor is the eous phase of . It is one of water within the . Water can be produced from the or of li ...
, 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 of ways, including for cooling, for
winter sport #REDIRECT Winter sports#REDIRECT Winter sports Winter sports or winter activities are competitive sports or non-competitive recreational activities which are played on snow or ice. Most are variations of skiing, ice skating and sledding. Traditi ...
s, and
ice sculpting
ice sculpting
.


Physical properties

As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a
mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

mineral
. It possesses a regular
crystalline A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid, gas and plasma). The molecules in a solid are closely packed together and contain the least amount of kinet ...

crystalline
structure based on the
molecule A molecule is an electrically Electricity is the set of physical phenomena associated with the presence and motion Image:Leaving Yongsan Station.jpg, 300px, Motion involves a change in position In physics, motion is the phenomenon ...

molecule
of water, which consists of a single
oxygen Oxygen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of the chemical elements In chemistry, an element is a pure substance consisting only of atoms that all have the same ...

oxygen
atom
covalently A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs, and the stable balance of attractive and repulsive forces between atoms, when they s ...
bonded to two
hydrogen atom #REDIRECT Hydrogen atom A hydrogen atom is an atom An atom is the smallest unit of ordinary matter In classical physics and general chemistry, matter is any substance that has mass and takes up space by having volume. All everyday o ...

hydrogen atom
s, or H–O–H. However, many of the physical properties of water and ice are controlled by the formation of
hydrogen bond A hydrogen bond (or H-bond) is a primarily electrostatic Electrostatics is a branch of physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department ...

hydrogen bond
s between adjacent oxygen and hydrogen atoms; while it is a weak bond, it is nonetheless critical in controlling the structure of both water and ice. An unusual property of water is that its solid form—ice frozen at atmospheric pressure—is approximately 8.3% less dense than its liquid form; this is equivalent to a volumetric expansion of 9%. The
density The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its per unit . The symbol most often used for density is ''ρ'' (the lower case Greek letter ), although the Latin letter ''D'' can also ...

density
of ice is 0.9167–0.9168 g/cm3 at 0 °C and standard atmospheric pressure (101,325 Pa), whereas water has a density of 0.9998–0.999863 g/cm3 at the same temperature and pressure. Liquid water is densest, essentially 1.00 g/cm3, at 4 °C and begins to lose its density as the water molecules begin to form the
hexagonal In geometry, a hexagon (from Ancient Greek, Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon or 6-gon. The total of the internal angles of any simple polygon, simple (non-self-intersecting) hexagon is 720°. Regul ...
crystal A crystal or crystalline solid is a solid Solid is one of the four fundamental states of matter (the others being liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continually Deformatio ...

crystal
s of
ice Ice is water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It is vital for all known forms of , eve ...

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 slightly with decreasing temperature and has a value of 0.9340 g/cm3 at −180 °C (93 K). When water freezes, it increases in volume (about 9% for fresh water). The effect of expansion during freezing can be dramatic, and ice expansion is a basic cause of
freeze-thaw Frost weathering is a collective term for several mechanical weathering Weathering is the breaking down of Rock (geology), rocks, soils, and minerals as well as wood and artificial materials through contact with water, atmospheric gases, and ...
weathering of rock in nature and damage to building foundations and roadways from
frost heaving Frost heaving (or a frost heave) is an upwards swelling of soil Soil (often stylized as SOiL) is an American rock band that was formed in Chicago (''City in a Garden''); I Will , image_map = , map_caption = Interact ...

frost heaving
. It is also 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 (in its most common form) floats on liquid water, which is an important feature in Earth's
biosphere The biosphere (from βίος ''bíos'' "life" and σφαῖρα ''sphaira'' "sphere"), also known as the ecosphere (from Greek οἶκος ''oîkos'' "environment" and σφαῖρα), is the worldwide sum of all s. It can also be termed the zo ...
. 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 sheet In , an ice sheet, also known as a continental glacier, is a mass of that covers surrounding terrain and is greater than . The only current ice sheets are in and ; during the at (LGM) the covered much of , the ice sheet covered and the c ...

ice sheet
s allow light to pass through while protecting the underside from short-term weather extremes such as
wind chill A chart of wind chill values for given air temperatures and wind speeds Wind-chill or windchill (popularly wind chill factor) is the lowering of body temperature due to the passing-flow of lower-temperature air. Wind chill numbers are always low ...

wind chill
. This creates a sheltered environment for bacterial and algal colonies. When sea water freezes, the ice is riddled with brine-filled channels which sustain sympagic organisms such as bacteria, algae, copepods 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 The emperor penguin (''Aptenodytes forsteri'') is the tallest and heaviest of all living penguin Penguins ( order Sphenisciformes , family In human society, family (from la, familia) is a group of people related either by consan ...

emperor penguins
and minke whales. When ice melts, it absorbs as much
energy In physics Physics is the that studies , its , its and behavior through , and the related entities of and . "Physical science is that department of knowledge which relates to the order of nature, or, in other words, to the regula ...

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 (water) molecules. Energy becomes available to increase the thermal energy (temperature) 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 The enthalpy of fusion of a substance, also known as (latent) heat of fusion is the change in its enthalpy Enthalpy is a property of a thermodynamic system A thermodynamic system is a body of matter and/or radiation, confined in space by walls ...
''. As with water, ice absorbs light at the red end of the spectrum preferentially as the result of an overtone of an oxygen–hydrogen (O–H) bond stretch. Compared with water, this absorption is shifted toward slightly lower energies. Thus, ice appears blue, with a slightly 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,
iceberg An iceberg is a piece of freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color ...

iceberg
s containing impurities (e.g., sediments, algae, air bubbles) can appear brown, grey or green.


Phases

Ice may be any one of the 19 known solid crystalline phases of
water Water (chemical formula H2O) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known li ...
, 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 , water freezes at a temperature ''below'' 0 °C, as shown in the phase diagram below. The melting of ice under high pressures is thought to contribute to the movement of
glacier A glacier (; ) is a persistent body of dense ice Ice is into a state. Depending on the presence of such as particles of soil or bubbles of air, it can appear transparent or a more or less bluish-white color. In the , ice is abunda ...

glacier
s. Ice, water, and
water vapour (99.9839 °C) , - , Boiling point , , - , specific gas constant , 461.5 J/( kg·K) , - , Heat of vaporization , 2.27 MJ/kg , - , Heat capacity , 1.864 kJ/(kg·K) Water vapor, water vapour or aqueous vapor is the gaseous p ...

water vapour
can coexist at the
triple point In , the triple point of a substance is the and at which the three (, , and ) of that substance coexist in .. It is that temperature and pressure at which the curve, curve and the curve meet. For example, the triple point of occurs at a tem ...
, which is exactly 273.16 K (0.01 °C) at a pressure of 611.657  Pa. The
kelvin The kelvin is the base unit of temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can be seen on this hot metalwork. Thermal en ...

kelvin
was in fact defined as of the difference between this triple point and
absolute zero Absolute zero is the lowest limit of the thermodynamic temperature Thermodynamic temperature is the measure of ''absolute temperature'' and is one of the principal parameters of thermodynamics. A thermodynamic temperature reading of zero deno ...
, though this definition
changed Change or Changing may refer to: Alteration * Impermanence, a difference in a state of affairs at different points in time * Menopause, also referred to as "the change", the permanent cessation of the menstrual period * Metamorphosis, or change, ...
in May 2019. Unlike most other solids, ice is difficult to . In an experiment, ice at −3 °C was superheated to about 17 °C for about 250
picosecond A picosecond is an SI unit of time equal to 10−12 or (one trillionth) of a second The second (symbol: s, abbreviation: sec) is the SI base unit, base unit of time in the International System of Units (SI) (French: Système International d ...
s. Subjected to higher pressures and varying temperatures, ice can form in 19 separate known crystalline phases. With care, at least 15 of these phases (one of the known exceptions being ice X) can be recovered at ambient pressure and low temperature in
metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's ground state, state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. I ...

metastable
form. The types are differentiated by their crystalline structure, proton ordering, and density. There are also two
metastable In chemistry and physics, metastability denotes an intermediate energetic state within a dynamical system other than the system's ground state, state of least energy. A ball resting in a hollow on a slope is a simple example of metastability. I ...

metastable
phases of ice under pressure, both fully hydrogen-disordered; these are IV and XII. Ice XII was discovered in 1996. In 2006, XIII and XIV were discovered. Ices XI, XIII, and XIV are hydrogen-ordered forms of ices Ih, V, and XII respectively. In 2009, ice XV was found at extremely high pressures and −143 °C. At even higher pressures, ice is predicted to become a
metal A metal (from Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is appro ...

metal
; this has been variously estimated to occur at 1.55 TPa or 5.62 TPa. As well as crystalline forms, solid water can exist in amorphous states as
amorphous ice Amorphous ice (non-crystalline or "vitreous" ice) is an amorphous solid In condensed matter physics and materials science The interdisciplinary field of materials science, also commonly termed materials science and engineering, covers the ...
(ASW) of varying densities. Water in the
interstellar medium In astronomy Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a natural science that studies astronomical object, celestial objects and celestial event, phenomena. It uses math ...
is dominated by amorphous ice, making it likely the most common form of water in the universe. Low-density ASW (LDA), also known as hyperquenched glassy water, may be responsible for
noctilucent clouds Noctilucent clouds, or night shining clouds, are tenuous cloud In meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry and atmospheric physics, with a major focus on weather forecasting. ...

noctilucent clouds
on Earth and is usually formed by
deposition Deposition may refer to: * Deposition (law), taking testimony outside of court * List of deposed politicians, Deposition (politics), the removal of a person of authority from political power * Deposition (university), a widespread initiation ritual ...
of water vapor in cold or vacuum conditions. High-density ASW (HDA) is formed by compression of ordinary ice Ih or LDA at GPa pressures. Very-high-density ASW (VHDA) is HDA slightly warmed to 160K under 1–2 GPa pressures. In outer space, hexagonal crystalline ice (the predominant form found on Earth) is extremely rare. Amorphous ice is more common; however, hexagonal crystalline ice can be formed by volcanic action. Ice from a theorized
superionic water Superionic water, also called superionic ice or ice XVIII is a phase of water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color of water, nearly colorless chemical su ...
may possess two crystalline structures. At pressures in excess of such ''superionic ice'' would take on a
body-centered cubic 200px, A network model of a primitive cubic system In crystallography, the cubic (or isometric) crystal system is a crystal system where the unit cell is in the shape of a cube. This is one of the most common and simplest shapes found in cryst ...
structure. However, at pressures in excess of the structure may shift to a more stable
face-centered cubic 200px, A network model of a primitive cubic system In crystallography Crystallography is the experimental science of determining the arrangement of atoms in crystalline solids (see crystal structure). The word "crystallography" is derived fro ...

face-centered cubic
lattice. It is speculated that superionic ice could compose the interior of ice giants such as Uranus and Neptune.Phys.org
"New phase of water could dominate the interiors of Uranus and Neptune"
Lisa Zyga, 25 April 2013


Friction properties

The low coefficient of friction ("slipperiness") of ice has been attributed to the pressure of an object coming into contact with the ice, melting a thin layer of the ice and allowing the object to glide across the surface. For example, the blade of an ice skate, upon exerting pressure on the ice, would melt a thin layer, providing lubrication between the ice and the blade. This explanation, called "pressure melting", originated in the 19th century. It, however, did not account for skating on ice temperatures lower than , which is often skated upon. A second theory describing the coefficient of friction of ice suggested that ice molecules at the interface cannot properly bond with the molecules of the mass of ice beneath (and thus are free to move like molecules of liquid water). These molecules remain in a semi-liquid state, providing lubrication regardless of pressure against the ice exerted by any object. However, the significance of this hypothesis is disputed by experiments showing a high
coefficient of friction Friction is the force In physics Physics (from grc, φυσική (ἐπιστήμη), physikḗ (epistḗmē), knowledge of nature, from ''phýsis'' 'nature'), , is the natural science that studies matter, its Motion (physics), ...
for ice using
atomic force microscopy Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very-high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer The nanometre (international spelling as u ...
. A third theory is "friction heating", which suggests that friction of the material is the cause of the ice layer melting. However, this theory does not sufficiently explain why ice is slippery when standing still even at below-zero temperatures. A comprehensive theory of ice friction takes into account all the above-mentioned friction mechanisms. This model allows quantitative estimation of the friction coefficient of ice against various materials as a function of temperature and sliding speed. In typical conditions related to winter sports and tires of a vehicle on ice, melting of a thin ice layer due to the frictional heating is the primary reason for the slipperiness. The mechanism controlling the frictional properties of ice is still an active area of scientific study.


Natural formation

The term that collectively describes all of the parts of the Earth's surface where water is in frozen form is the ''
cryosphere The cryosphere (from the Greek ''kryos'', "cold", "frost" or "ice" and ''sphaira'', "globe, ball") is an all-encompassing term for those portions of Earth Earth is the third planet from the Sun and the only astronomical object known to ...
.'' Ice is an important component of the global climate, particularly in regard to the water cycle. Glaciers and
snowpack Snowpack forms from layers of snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes. It consists of f ...
s are an important storage mechanism for fresh water; over time, they may sublimate or melt.
Snowmelt In hydrology Hydrology (from Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population is approxim ...
is an important source of seasonal fresh water. The
World Meteorological Organization The World Meteorological Organization (WMO) is a specialized agency United Nations Specialized Agencies are autonomous organizations working with the United Nations The United Nations (UN) is an intergovernmental organization that aims ...
defines several kinds of ice depending on origin, size, shape, influence and so on."WMO SEA-ICE NOMENCLATURE"

Multi-language
) ''World Meteorological Organization'' / ''
Arctic and Antarctic Research Institute , image = , image_upright = , alt = , caption = , latin_name = , motto = , founder = , established = , mission = , focus = Research ...
''. Retrieved 8 April 2012.
Clathrate hydrate Clathrate hydrates, or gas hydrates, clathrates, hydrates, etc., are crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, f ...
s are forms of ice that contain gas molecules trapped within its crystal lattice.


On the oceans

Ice that is found at sea may be in the form of
drift ice Drift ice, also called brash ice, is sea ice that is not attached to the shoreline or any other fixed object (shoals, grounded icebergs, etc.).Leppäranta, M. 2011. The Drift of Sea Ice. Berlin: Springer-Verlag. Unlike fast ice, which is "fastene ...
floating in the water,
fast ice Fast ice (also called ''land-fast ice'', ''landfast ice'', and ''shore-fast ice'') is sea ice Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an e ...
fixed to a shoreline or
anchor ice Anchor ice is defined by the World Meteorological Organization The World Meteorological Organization (WMO) is a specialized agency United Nations Specialized Agencies are autonomous organizations working with the United Nations The ...
if attached to the sea bottom. Ice which
calves Calves is a hamlet in Póvoa de Varzim Póvoa de Varzim (, ) is a Portugal, Portuguese city in Norte Region, Portugal, Northern Portugal and sub-region of Greater Porto, 30 km from its city centre. It sits in a sandy coastal plain, a cuspa ...
(breaks off) from an
ice shelf An ice shelf is a large floating platform of ice that forms where a or flows down to a line and onto the ocean surface. Ice shelves are only found in , , , and the . The boundary between the floating ice shelf and the (resting on bedrock) ...
or glacier may become an iceberg. Sea ice can be forced together by currents and winds to form pressure ridges up to tall. Navigation through areas of sea ice occurs in openings called "
polynya A polynya () is an area of open water surrounded by sea ice Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice cove ...
s" or "
leads Lead is a chemical element with symbol Pb and atomic number 82. Lead may also refer to: Animal handling * Leash, or lead * Lead (leg), the leg that advances most in a quadruped's cantering or galloping stride * Lead (tack) Arts, entertainment ...
" or requires the use of a special ship called an "
icebreaker An icebreaker is a special-purpose ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep Sea lane, waterways, carrying goods or passengers, or in support of specialized missions, such as defense, rese ...
".


On land and structures

Ice on land ranges from the largest type called an "
ice sheet In , an ice sheet, also known as a continental glacier, is a mass of that covers surrounding terrain and is greater than . The only current ice sheets are in and ; during the at (LGM) the covered much of , the ice sheet covered and the c ...

ice sheet
" to smaller
ice cap In glaciology Lateral moraine on a glacier joining the Gorner Glacier, Zermatt">Gorner_Glacier.html" ;"title="moraine on a glacier joining the Gorner Glacier">moraine on a glacier joining the Gorner Glacier, Zermatt, Swiss Alps. The moraine is ...
s and
ice field An ice field (also spelled icefield) is a mass of interconnected valley glaciers (also called mountain glaciers or alpine glaciers) on a mountain mass with protruding rock ridges or summits. They are often found in the colder climates and highe ...
s to glaciers and
ice stream Velocity map of Antarctica. Ice streams can be seen with increasing speeds (blue-yellow-white) flowing toward the coast. An ice stream is a region of fast-moving ice within an ice sheet. It is a type of glacier, a body of ice that moves under its ...
s to the
snow line The climatic snow line is the boundary between a snow Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further chang ...
and
snow field A snow field, snowfield or neve is an accumulation of permanent snow and ice, typically found above the snow line, normally in mountainous and glacial terrain. Glaciers A glacier ( or ) is a persistent body of dense ice that is constantl ...
s.
Aufeis Aufeis, ( ), ( for "ice on top") is a sheet-like mass of layered that forms from successive flows of ground water during freezing temperatures. This form of ice is also called overflow, icings, or the term, naled. The term was first used in 185 ...
is layered ice that forms in Arctic and subarctic stream valleys. Ice, frozen in the stream bed, blocks normal groundwater discharge, and causes the local water table to rise, resulting in water discharge on top of the frozen layer. This water then freezes, causing the water table to rise further and repeat the cycle. The result is a stratified ice deposit, often several meters thick.
Freezing rain Freezing rain is rain Rain is liquid water in the form of droplet Raindrops in a plant. A drop or droplet is a small column of liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continua ...

Freezing rain
is a type of winter storm called an
ice storm #REDIRECT Ice storm#REDIRECT Ice storm An ice storm is a type of winter storm characterized by freezing rain, also known as a ''glaze event'' or, in some parts of the United States, as a ''silver thaw''. The U.S. National Weather Service define ...

ice storm
where rain falls and then freezes producing a of ice. Ice can also form icicles, similar to
stalactite A stalactite (, ; from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its population ...

stalactite
s in appearance, or
stalagmite A stalagmite (, ; from the Greek#REDIRECT Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλάδα, , ), officially the Hellenic Republic, is a country located in Southeast Europe. Its populati ...

stalagmite
-like forms as water drips and re-freezes. The term "ice dam" has three meanings (others discussed below). On structures, an ice dam is the buildup of ice on a sloped roof which stops melt water from draining properly and can cause damage from water leaks in buildings.


On rivers and streams

Ice which forms on moving water tends to be less uniform and stable than ice which forms on calm water.
Ice jam Ice jams occur when floating river ice accumulates at a natural or man-made feature that impedes the progress of the ice downstream with the river current. Ice jams can significantly reduce the flow of a river and cause upstream flooding—some ...
s (sometimes called "ice dams"), when broken chunks of ice pile up, are the greatest ice hazard on rivers. Ice jams can cause flooding, damage structures in or near the river, and damage vessels on the river. Ice jams can cause some
hydropower Hydropower (from el, ὕδωρ, "water"), also known as water power, is the use of falling or fast-running water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and th ...
industrial facilities to completely shut down. An ice dam is a blockage from the movement of a glacier which may produce a
proglacial lake In geology, a proglacial lake is a lake formed either by the damming action of a moraine A moraine is any accumulation of unconsolidated debris (regolith and rock), sometimes referred to as glacial till, that occurs in both currently and fo ...
. Heavy ice flows in rivers can also damage vessels and require the use of an icebreaker to keep navigation possible. Ice discs are circular formations of ice surrounded by water in a river.
Pancake ice Pancake ice is a form of sea ice Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's su ...

Pancake ice
is a formation of ice generally created in areas with less calm conditions.


On lakes

Ice forms on calm water from the shores, a thin layer spreading across the surface, and then downward. Ice on lakes is generally four types: primary, secondary, superimposed and agglomerate. Primary ice forms first. Secondary ice forms below the primary ice in a direction parallel to the direction of the heat flow. Superimposed ice forms on top of the ice surface from rain or water which seeps up through cracks in the ice which often settles when loaded with snow. occurs when floating pieces of ice are driven by the wind piling up on the windward shore.
Candle ice Rotten ice is a loose term for ice Ice is water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in which it acts as a ). It i ...

Candle ice
is a form of
rotten ice Rotten ice is a loose term for ice that is melting or structurally disintegrating due to being honeycombed by liquid water, air, or contaminants trapped between the initial growth of ice crystals. It may appear transparent or splotchy grey, and it i ...
that develops in columns perpendicular to the surface of a lake. An
ice shove An ice shove (also known as an ice surge, ice push, ice heave, shoreline ice pileup, ice piling, ice thrust, ice tsunami, ice ride-up, or ''ivu'' in Iñupiat, Inupiat) is a surge of ice from an ocean or large lake onto the shore. Ice shoves are c ...

ice shove
occurs when ice movement, caused by ice expansion and/or wind action, occurs to the extent that ice pushes onto the shores of lakes, often displacing sediment that makes up the shoreline.


In the air


Rime

Rime is a type of ice formed on cold objects when drops of water crystallize on them. This can be observed in
fog Fog is a visible aerosol consisting of tiny water drop (liquid), droplets or ice crystals suspended in the air at or near the Earth's surface. Reprint from Fog can be considered a type of low-lying cloud usually resembling stratus cloud, s ...

fog
gy weather, when the temperature drops during the night.
Soft rime Rime ice forms when supercooled water liquid droplets freeze onto surfaces. Meteorology, Meteorologists distinguish between three basic types of ice forming on vertical and horizontal surfaces by deposition of supercooled water droplets. There are ...
contains a high proportion of trapped air, making it appear white rather than transparent, and giving it a density about one quarter of that of pure ice.
Hard rime Rime ice forms when liquid droplets freeze onto surfaces. s distinguish between three basic types of ice forming on vertical and horizontal surfaces by deposition of supercooled water droplets. There are also intermediate formations. *Soft rime ...
is comparatively dense.


Pellets

Ice pellets Ice pellets are a form of precipitation (meteorology), precipitation consisting of small, translucent balls of ice. Ice pellets are different from graupel ("soft hail") which is made of frosty white hard rime, rime, and from rain and snow mixed, ...

Ice pellets
are a form of precipitation consisting of small,
translucent In the field of optics, transparency (also called pellucidity or diaphaneity) is the physical property of allowing light to pass through the material without appreciable scattering of light. On a macroscopic scale (one in which the dimensions are ...
balls of ice. This form of precipitation is also referred to as "sleet" by the United States
National Weather Service The National Weather Service (NWS) is an agency Agency may refer to: * a governmental or other institution Institutions, according to Samuel P. Huntington, are "stable, valued, recurring patterns of behavior". Institutions can refer to m ...
. (In
British English British English (BrE) is the standard dialect A standard language (also standard variety, standard dialect, and standard) is a language variety that has undergone substantial codification of grammar and usage and is employed by a populatio ...
"sleet" refers to a mixture of rain and snow.) Ice pellets are usually smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with
freezing rain Freezing rain is rain Rain is liquid water in the form of droplet Raindrops in a plant. A drop or droplet is a small column of liquid A liquid is a nearly incompressible fluid In physics, a fluid is a substance that continua ...

freezing rain
. The
METAR METAR is a format for reporting weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur ...
code for ice pellets is ''PL''. Ice pellets form when a layer of above-freezing air is located between above the ground, with sub-freezing air both above and below it. This causes the partial or complete melting of any snowflakes falling through the warm layer. As they fall back into the sub-freezing layer closer to the surface, they re-freeze into ice pellets. However, if the sub-freezing layer beneath the warm layer is too small, the precipitation will not have time to re-freeze, and freezing rain will be the result at the surface. A temperature profile showing a warm layer above the ground is most likely to be found in advance of a
warm front A warm front is a density discontinuity located at the leading edge of a homogeneous warm air mass upright=1.25, Different air masses which affect North America as well as other continents, tend to be separated by frontal boundaries In meteo ...

warm front
during the cold season, but can occasionally be found behind a passing
cold front A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough Trough may refer to: In science * Trough (geology), a long depression less steep than a tren ...

cold front
.


Hail

Like other precipitation, hail forms in storm
cloud In meteorology, a cloud is an aerosol consisting of a visible mass of minute liquid drop (liquid), droplets, ice crystals, frozen crystals, or other particulates, particles suspended in the atmosphere of a planetary body or similar space. Wate ...

cloud
s when
supercooled Supercooling, also known as undercooling, is the process of lowering the temperature of a liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isoc ...
water droplets freeze on contact with
condensation nuclei Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles typically 0.2 µm, or 1/100 the size of a cloud In meteorology Meteorology is a branch of the atmospheric sciences which includes atmospheric chemistry a ...
, such as
dust Dust is made of s of solid . On Earth, it generally consists of particles in the that come from various sources such as lifted by wind (an ), , and . Dust in homes is composed of about 20–50% dead . The rest, and in offices, and other ...
or
dirt Dirt is an unclean matter, especially when in contact with a person's clothes, skin, or possessions. In such cases, they are said to become dirty. Common types of dirt include: * Dust: a general powder of Organic matter, organic or Mineral, ...

dirt
. The storm's
updraft In meteorology Meteorology is a branch of the atmospheric sciences Atmospheric science is the study of the Earth's atmosphere File:Atmosphere gas proportions.svg, Composition of Earth's atmosphere by volume, excluding water vapor. Lowe ...
blows the hailstones to the upper part of the cloud. The updraft dissipates and the hailstones fall down, back into the updraft, and are lifted up again. Hail has a diameter of or more. Within
METAR METAR is a format for reporting weather Weather is the state of the atmosphere, describing for example the degree to which it is hot or cold, wet or dry, calm or stormy, clear or cloud cover, cloudy. On Earth, most weather phenomena occur ...
code, GR is used to indicate larger hail, of a diameter of at least and GS for smaller. Stones just larger than
golf ball A golf ball is a special ball A ball is a round object (usually spherical, but can sometimes be ovoid An oval (from Latin ''ovum'', "egg") is a closed curve in a plane which resembles the outline of an egg. The term is not very specif ...

golf ball
-sized are one of the most frequently reported hail sizes. Hailstones can grow to and weigh more than . In large hailstones,
latent heat Latent heat (also known as latent energy or heat of transformation) is energy released or absorbed, by a body or a thermodynamic system A thermodynamic system is a body of matter In classical physics and general chemistry, matter is any su ...
released by further freezing may melt the outer shell of the hailstone. The hailstone then may undergo 'wet growth', where the liquid outer shell collects other smaller hailstones. The hailstone gains an ice layer and grows increasingly larger with each ascent. Once a hailstone becomes too heavy to be supported by the storm's updraft, it falls from the cloud. Hail forms in strong
thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning Lightning is a naturally occurring electrostatic discharge Electrostatic discharge (ESD) is the sudden fl ...

thunderstorm
clouds, particularly those with intense updrafts, high liquid water content, great vertical extent, large water droplets, and where a good portion of the cloud layer is below freezing . Hail-producing clouds are often identifiable by their green coloration. The growth rate is maximized at about , and becomes vanishingly small much below as supercooled water droplets become rare. For this reason, hail is most common within continental interiors of the mid-latitudes, as hail formation is considerably more likely when the freezing level is below the altitude of . Entrainment of dry air into strong thunderstorms over continents can increase the frequency of hail by promoting evaporational cooling which lowers the freezing level of thunderstorm clouds giving hail a larger volume to grow in. Accordingly, hail is actually less common in the tropics despite a much higher frequency of thunderstorms than in the mid-latitudes because the
atmosphere An atmosphere (from the greek words ἀτμός ''(atmos)'', meaning 'vapour', and σφαῖρα ''(sphaira)'', meaning 'ball' or 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in ...

atmosphere
over the tropics tends to be warmer over a much greater depth. Hail in the tropics occurs mainly at higher elevations.


Snow

Snow crystals form when tiny ed cloud droplets (about 10 μm in diameter)
freeze Freeze may refer to: Liquids turning to solids *Freezing, the physical process of a liquid turning into a solid Cessation of movement or change *Freeze (b-boy move), the halting of all movement in a clever position *Freeze (command), freez ...

freeze
. These droplets are able to remain liquid at temperatures lower than , because to freeze, a few molecules in the droplet need to get together by chance to form an arrangement similar to that in an ice lattice; then the droplet freezes around this "nucleus". Experiments show that this "homogeneous" nucleation of cloud droplets only occurs at temperatures lower than . In warmer clouds an aerosol particle or "ice nucleus" must be present in (or in contact with) the droplet to act as a nucleus. Our understanding of what particles make efficient ice nuclei is poor – what we do know is they are very rare compared to that cloud condensation nuclei on which liquid droplets form. Clays, desert dust and biological particles may be effective, although to what extent is unclear. Artificial nuclei are used in
cloud seeding Cloud seeding is a type of weather modification Weather modification (also known as weather control) is the act of intentionally manipulating or altering the weather Weather is the state of the atmosphere, describing for example the de ...
. The droplet then grows by condensation of water vapor onto the ice surfaces.


Diamond dust

So-called "diamond dust", also known as ice needles or ice crystals, forms at temperatures approaching due to air with slightly higher moisture from aloft mixing with colder, surface-based air. The METAR identifier for diamond dust within international hourly weather reports is ''IC''.


Ablation

Ablation of ice refers to both its
melting Melting, or Enthalpy of fusion, fusion, is a physical process that results in the phase transition of a chemical substance, substance from a solid to a liquid. This occurs when the internal energy of the solid increases, typically by the applic ...

melting
and its
dissolution Dissolution may refer to: Arts and entertainment Books * Dissolution (Forgotten Realms novel), ''Dissolution'' (''Forgotten Realms'' novel), a 2002 fantasy novel by Richard Lee Byers * Dissolution (Sansom novel), ''Dissolution'' (Sansom novel), a 2 ...
. The melting of ice means entails the breaking of
hydrogen bonds A hydrogen bond (or H-bond) is a primarily Electrostatics, electrostatic force of attraction between a hydrogen Hydrogen is the chemical element Image:Simple Periodic Table Chart-blocks.svg, 400px, Periodic table, The periodic table of ...
between the water molecules. The ordering of the molecules in the solid breaks down to a less ordered state and the solid melts to become a liquid. This is achieved by increasing the internal energy of the ice beyond the
melting point The melting point (or, rarely, liquefaction point) of a substance is the temperature Temperature ( ) is a physical quantity that expresses hot and cold. It is the manifestation of thermal energy Thermal radiation in visible light can b ...

melting point
. When ice melts it absorbs as much energy as would be required to heat an equivalent amount of water by 80 °C. While melting, the temperature of the ice surface remains constant at 0 °C. The rate of the melting process depends on the efficiency of the energy exchange process. An ice surface in
fresh water Fresh water or freshwater is any naturally occurring liquid or frozen water Water (chemical formula H2O) is an , transparent, tasteless, odorless, and , which is the main constituent of 's and the s of all known living organisms (in ...

fresh water
melts solely by free convection with a rate that depends linearly on the water temperature, ''T'', when ''T'' is less than 3.98 °C, and superlinearly when ''T'' is equal to or greater than 3.98 °C, with the rate being proportional to (T − 3.98 °C)''α'', with ''α'' =  for ''T'' much greater than 8 °C, and α =  for in between temperatures ''T''. In salty ambient conditions, dissolution rather than melting often causes the ablation of ice. For example, the temperature of the
Arctic Ocean The Arctic Ocean is the smallest and shallowest of the world's five major s. It spans an area of approximately and is also known as the coldest of all the oceans. The (IHO) recognizes it as an ocean, although some call it the Arctic Medit ...

Arctic Ocean
is generally below the melting point of ablating sea ice. The phase transition from solid to liquid is achieved by mixing
salt Salt is a mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure fo ...

salt
and water molecules, similar to the dissolution of
sugar Sugar is the generic name for sweet-tasting, soluble carbohydrate is a disaccharide A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosacc ...

sugar
in water, even though the water temperature is far below the melting point of the sugar. Thus the dissolution rate is limited by salt transport whereas melting can occur at much higher rates that are characteristic for heat transport.


Role in human activities

Humans have used ice for cooling and
food preservation Food preservation includes food processing practices which prevent the growth of microorganisms, such as yeasts (although some methods work by introducing benign bacteria or fungi to the food), and slow the redox, oxidation of fats that cause Ran ...

food preservation
for centuries, relying on harvesting natural ice in various forms and then transitioning to the mechanical production of the material. Ice also presents a challenge to transportation in various forms and a setting for winter sports.


Cooling

Ice has long been valued as a means of cooling. In 400 BC Iran,
Persian Persian may refer to: * People and things from Iran, historically called ''Persia'' in the English language ** Persians, Persian people, the majority ethnic group in Iran, not to be conflated with the Iranian peoples ** Persian language, an Iranian ...

Persian
engineers had already mastered the technique of storing ice in the middle of summer in the desert. The ice was brought in during the winters from nearby mountains in bulk amounts, and stored in specially designed, naturally cooled ''refrigerators'', called (meaning ''ice storage''). This was a large underground space (up to 5000 m3) that had thick walls (at least two meters at the base) made of a special mortar called ''
sarooj Sarooj is a traditional water-resistant Waterproofing is the process of making an object or structure waterproof or water-resistant so that it remains relatively unaffected by water or resisting the ingress of water under specified conditions ...
'', composed of sand, clay, egg whites, lime, goat hair, and ash in specific proportions, and which was known to be resistant to heat transfer. This mixture was thought to be completely water impenetrable. The space often had access to a qanat, and often contained a system of windcatchers which could easily bring temperatures inside the space down to frigid levels on summer days. The ice was used to chill treats for royalty.


Harvesting

There were thriving industries in 16th–17th century England whereby low-lying areas along the Thames Estuary were flooded during the winter, and ice harvested in carts and stored inter-seasonally in insulated wooden houses as a provision to an icehouse often located in large country houses, and widely used to keep fish fresh when caught in distant waters. This was allegedly copied by an Englishman who had seen the same activity in China. Ice was imported into England from Norway on a considerable scale as early as 1823. In the United States, the first cargo of ice was sent from New York City to Charleston, South Carolina, in 1799, and by the first half of the 19th century, ice harvesting had become a big business. Frederic Tudor, who became known as the "Ice King", worked on developing better insulation products for long distance shipments of ice, especially to the tropics; this became known as the ice trade. Trieste sent ice to Egypt, Corfu, and Zante; Switzerland, to France; and Germany sometimes was supplied from Bavarian lakes. The Hungarian Parliament building used ice harvested in the winter from Lake Balaton for air conditioning. Ice house (building), Ice houses were used to store ice formed in the winter, to make ice available all year long, and an early type of refrigerator known as an icebox was cooled using a block of ice placed inside it. In many cities, it was not unusual to have a regular ice Delivery (commerce), delivery service during the summer. The advent of artificial refrigeration technology has since made delivery of ice obsolete. Ice is still harvested for List of ice and snow sculpture events, ice and snow sculpture events. For example, a swing saw is used to get ice for the Harbin International Ice and Snow Sculpture Festival each year from the frozen surface of the Songhua River.


Mechanical production

Ice is now produced on an industrial scale, for uses including food storage and processing, chemical manufacturing, concrete mixing and curing, and consumer or packaged ice.ASHRAE. "Ice Manufacture". ''2006 ASHRAE Handbook: Refrigeration.'' Inch-Pound Edition. . Most commercial icemakers produce three basic types of fragmentary ice: flake, tubular and plate, using a variety of techniques. Large batch ice makers can produce up to 75 tons of ice per day. In 2002, there were 426 commercial ice-making companies in the United States, with a combined value of shipments of $595,487,000. Home refrigerators can also make ice with a built in icemaker, which will typically make ice cubes or crushed ice. Stand-alone icemaker units that make ice cubes are often called ice machines.


Transportation

Ice can present challenges to safe transportation on land, sea and in the air.


Land travel

Ice forming on roads is a dangerous winter hazard. Black ice is very difficult to see, because it lacks the expected frosty surface. Whenever there is freezing rain or snow which occurs at a temperature near the melting point, it is common for ice to build up on the windows of vehicles. Driving safely requires the removal of the ice build-up. Ice scrapers are tools designed to break the ice free and clear the windows, though removing the ice can be a long and laborious process. Far enough below the freezing point, a thin layer of ice crystals can form on the inside surface of windows. This usually happens when a vehicle has been left alone after being driven for a while, but can happen while driving, if the outside temperature is low enough. Moisture from the driver's breath is the source of water for the crystals. It is troublesome to remove this form of ice, so people often open their windows slightly when the vehicle is parked in order to let the moisture dissipate, and it is now common for cars to have rear-window defrosters to solve the problem. A similar problem can happen in homes, which is one reason why many colder regions require Insulated glazing, double-pane windows for insulation. When the outdoor temperature stays below freezing for extended periods, very thick layers of ice can form on lakes and other bodies of water, although places with flowing water require much colder temperatures. The ice can become thick enough to drive onto with automobiles and trucks. Doing this safely requires a thickness of at least 30 cm (one foot).


Water-borne travel

For ships, ice presents two distinct hazards. First, spray and freezing rain can produce an ice build-up on the superstructure of a vessel sufficient to make it unstable, and to require it to be hacked off or melted with steam hoses. Second,
iceberg An iceberg is a piece of freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water Water is an Inorganic compound, inorganic, Transparency and translucency, transparent, tasteless, odorless, and Color ...

iceberg
s – large masses of ice floating in water (typically created when glaciers reach the sea) – can be dangerous if struck by a ship when underway. Icebergs have been responsible for the sinking of many ships, the most famous being the RMS Titanic, ''Titanic''. For harbors near the geographical pole, poles, being ice-free, ideally all year long, is an important advantage. Examples are Murmansk (Russia), Pechengsky District, Petsamo (Russia, formerly Finland), and Vardø (town), Vardø (Norway). Harbors which are not ice-free are opened up using
icebreaker An icebreaker is a special-purpose ship A ship is a large watercraft that travels the world's oceans and other sufficiently deep Sea lane, waterways, carrying goods or passengers, or in support of specialized missions, such as defense, rese ...
s.


Air travel

For aircraft, ice can cause a number of dangers. As an aircraft climbs, it passes through air layers of different temperature and humidity, some of which may be conducive to ice formation. If ice forms on the wings or control surfaces, this may adversely affect the flying qualities of the aircraft. During the Transatlantic flight of Alcock and Brown, first non-stop flight across the Atlantic, the British aviators Captain John Alcock (RAF officer), John Alcock and Lieutenant Arthur Whitten Brown encountered such icing conditions – Brown left the cockpit and climbed onto the wing several times to remove ice which was covering the engine air intakes of the Vickers Vimy aircraft they were flying. One vulnerability effected by icing that is associated with reciprocating internal combustion engines is the carburetor. As air is sucked through the carburetor into the engine, the local air pressure is lowered, which causes adiabatic cooling. Thus, in humid near-freezing conditions, the carburetor will be colder, and tend to ice up. This will block the supply of air to the engine, and cause it to fail. For this reason, aircraft reciprocating engines with carburetors are provided with Carburetor heat, carburetor air intake heaters. The increasing use of fuel injection—which does not require carburetors—has made "carb icing" less of an issue for reciprocating engines. Jet engines do not experience carb icing, but recent evidence indicates that they can be slowed, stopped, or damaged by internal icing in certain types of atmospheric conditions much more easily than previously believed. In most cases, the engines can be quickly restarted and flights are not endangered, but research continues to determine the exact conditions which produce this type of icing, and find the best methods to prevent, or reverse it, in flight.


Recreation and sports

Ice also plays a central role in winter recreation and in many sports such as ice skating, tour skating, ice hockey, bandy, ice fishing, ice climbing, curling, broomball and sled racing on bobsled, luge and Skeleton (sport), skeleton. Many of the different sports played on ice get international attention every four years during the Winter Olympic Games. A sort of sailboat on blades gives rise to ice yachting. Another sport is ice racing, where drivers must speed on lake ice, while also controlling the skid of their vehicle (similar in some ways to dirt track racing). The sport has even been modified for ice rinks.


Other uses


As thermal ballast

* Ice is used to cool and preserve food in iceboxes. *Ice cubes or crushed ice can be used to cool drinks. As the ice melts, it absorbs heat and keeps the drink near . * Ice can be used as part of an Ice storage air conditioning, air conditioning system, using battery- or solar power, solar-powered fans to blow hot air over the ice. This is especially useful during heat waves when power is out and standard (electrically powered) air conditioners do not work. * Ice can be used (like other cold packs) to reduce swelling (by decreasing blood flow) and pain by pressing it against an area of the body.


As structural material

* Engineers used the substantial strength of pack ice when they constructed Antarctica's first floating ice pier in 1973. Such ice piers are used during cargo operations to load and offload ships. Fleet operations personnel make the floating pier during the winter. They build upon naturally occurring frozen seawater in McMurdo Sound until the dock reaches a depth of about . Ice piers have a lifespan of three to five years. * Structures and ice sculptures are built out of large chunks of ice or by spraying waterMakkonen, L. (1994) "Ice and Construction". E & FN Spon, London. . The structures are mostly ornamental (as in the case with Ice palace, ice castles), and not practical for long-term habitation. Ice hotels exist on a seasonal basis in a few cold areas. Igloos are another example of a temporary structure, made primarily from snow. * In cold climates, roads are regularly prepared on iced-over lakes and archipelago areas. Temporarily, even a railroad has been built on ice. * During World War II, Project Habbakuk was an Allied programme which investigated the use of pykrete (wood fibers mixed with ice) as a possible material for warships, especially aircraft carriers, due to the ease with which a vessel immune to torpedoes, and a large deck, could be constructed by ice. A small-scale prototype was built, but the need for such a vessel in the war was removed prior to building it in full-scale. * Ice has even been used as the material for a variety of musical instruments, for example by percussionist Terje Isungset.


Non-water

The solid phases of several other volatile substances are also referred to as ''ices''; generally a volatile is classed as an ice if its melting point lies above or around 100 K. The best known example is dry ice, the solid form of carbon dioxide. A "magnetic analogue" of ice is also realized in some insulating magnetic materials in which the magnetic moments mimic the position of protons in water ice and obey energetic constraints similar to the Bernal-Fowler ice rules arising from the geometrical frustration of the proton configuration in water ice. These materials are called spin ice.


See also

* * * * * * *


References


External links


Webmineral listing for Ice



Estimating the bearing capacity of ice




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