تويت
commonly lava tubes or limestone
Limestone
Limestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geologic record...
caves) that contains significant amounts of perennial (year-round) ice
Ice
Ice is a solid phase, usually crystalline, of a non-****llic substance that is liquid or gas at room temperature, such as carbon dioxide ice , ammonia ice, or methane ice. However, the predominant use of the term ice is for water ice, technically restricted to one of the 15 known crystalline phases...
. At least a portion of the cave must have a temperature below 0 °C
Celsius
Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
(32 °F
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the physicist Daniel Gabriel Fahrenheit . Today, the scale has been replaced by the Celsius scale in most countries; it is still in use for non-scientific purposes in the United States and a few other nations, such as...
) all year round, and water
Water
Water is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
must have traveled into the cave’s cold zone.
The term ice cave is often used to describe a cavity formed within ice, which is properly called a glacier cave
Glacier cave
A glacier cave is a cave formed within the ice of a glacier. Glacier caves are often called ice caves, but this term is properly used to describe bedrock caves that contain year-round ice.-Overview:...
.
Temperature Mechanisms
Bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
caves are thermally insulated
Thermal insulation
The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer....
from the surface, so commonly assume a near-constant temperature
Temperature
In physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
approximating the annual average temperature at the surface. In some cold environments, average surface (and thus cave) temperatures are below freezing, and with surface water available in summer, ice caves are possible. However, many ice caves exist in temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. But in continental areas, such as central North America the variations between summer...
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
Convection
Convection is the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer...
to import cold air from the surface in winter, but not warm air in summer. A typical example is an underground chamber located below a single entrance. In winter, cold dense air settles into the cave, displacing any warmer air which rises and exits the cave. In summer, the cold cave air remains in place as the relatively warm surface air is lighter and cannot enter. The cave will only exchange air when the surface air is cooler than the cave air. Some cold traps may ensnare surface snow
Snow
Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by external pressure. Snowflakes...
and shade it from the summer sun
Sun
The Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
’s rays
Sunlight
Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. Near the poles in summer, the days are longer and the...
, 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
Permafrost
In geology, permafrost or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground...
. For example, winter wind and an absence of snow cover may allow freezing deep enough to be protected from summer thaw, particularly in light-colored rock
Rock (geology)
.gif)
In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and ****morphic...
that does not readily absorb heat. Although the portion of a cave within this permafrost zone will be below freezing, permafrost generally does not allow water percolation
Percolation
In physics, chemistry and materials science, percolation concerns the movement and filtering of fluids through porous materials. Examples include the movement of solvents through filter paper and the movement of petroleum through fractured rock. Electrical analogs include the flow of electricity...
, so ice formations are often limited to crystals from vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical temperature....
, and deeper cave passages may be arid and completely ice-free. Ice caves in permafrost need not be cold-traps (although some are), provided they do not draught significantly in summer.
Evaporative cooling - In winter, dry surface air entering a moisture-saturated cave may have an additional cooling effect due to the latent heat
Latent heat
The expression latent heat refers to the amount of energy released or absorbed by a chemical substance during a change of state that occurs without changing its temperature, meaning a phase transition such as the melting of ice or the boiling of water...
of evaporation
Evaporation
Evaporation is the vaporization of a liquid and the reverse, of condensation. A type of phase transition, it is the process by which molecules in a liquid state spontaneously become gaseous . Generally, evaporation can be seen by the gradual disappearance of a liquid from a substance when exposed...
. This may create a zone within the cave that is cooler than the rest of the cave. Because many caves have seasonally-reversing draughts, the corresponding warming of the cave through condensation
Condensation
Condensation is the change of the physical state of aggregation of matter from gaseous phase into liquid phase and the reverse of evaporation. When the transition happens from the gaseous phase into the solid phase directly, bypassing the liquid phase, the change is called deposition...
in summer may occur at a different ******** within the cave, but in any event a moisture-saturated cave environment is likely to experience much more evaporative cooling than condensative warming.
Types of Ice in Ice Caves
Different freezing mechanisms result in visually and structurally distinct types of perennial cave ice.
Ponded water - Surface water that collects and ponds in a cave before freezing will form a clear ice mass, and can be tens of metres thick and of great age. Large ice masses are plastic
Plasticity (physics)
In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of ****l or plastic being bent or pounded into a new shape displays plasticity as permanent changes occur within...
and can slowly flow in response to gravity or pressure from further accumulations. Sculpting from air flow and sublimation may reveal ancient accumulation bands within the ice.
Accumulated snow - Compressed under the weight of ongoing accumulations, snow sliding or falling into a cave entrance may eventually form ice that is coarsely crystalline, akin to glacier
Glacier
A glacier is a perennial mass of ice which moves over land. A glacier forms in ********s where the mass accumulation of snow and ice exceeds ablation over many years...
ice. True underground glaciers are rare.
Ice formations - Water that freezes before ponding may form icicle
Icicle
An icicle is a spike of ice formed when water dripping or falling from an ****** freezes. Typically, icicles will form when ice or snow is melted by either sunlight or some other heat source , and the resulting melted water runs off into an area where the ambient temperature is below the freezing...
s, ice-stalagmite
Stalagmite
A stalagmite is a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate. The corresponding formation on the ceiling of a cave is known as a stalactite...
s, ice columns or frozen waterfall
Waterfall
A waterfall is a place where flowing water rapidly drops in elevation as it flows over a steep region or a cliff.-Formation :Typically, a river flows over a large step in the rocks that may have been formed by a fault line. As it increases its velocity at the edge of the waterfall, it plucks...
s.
Airborne moisture (water vapor) – Freezing vapor can form frost
Frost
Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air. Frost crystals' size differ depending on time and water vapor available. Frost is also usually translucent in appearance. There are many types of...
crystals, frost feathers and two-dimensional ice plates on the cave walls and ceiling.
Needle ice
Needle ice
Needle ice is a phenomenon that occurs when the temperature of the soil is above 0°C and the surface temperature of the air is below 0°C. The subterranean moisture is brought to the surface via capillary action....
- 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
Castleguard Cave
Castleguard Cave is a limestone cave located at the north end of Banff National Park in the Rocky Mountains of Canada. With 20,357m of surveyed passages , it is Canada’s longest cave, and its fifth deepest at 384m...
in Alberta
Alberta
Alberta is one of Canada's prairie provinces. It became a province on September 1, 1905.Alberta is located in western Canada, bounded by the provinces of British Columbia to the west and Saskatchewan to the east, the Northwest Territories to the north, and the U.S. state of Montana to the south....
.
Limestone
Limestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geologic record...
caves) that contains significant amounts of perennial (year-round) ice
Ice
Ice is a solid phase, usually crystalline, of a non-****llic substance that is liquid or gas at room temperature, such as carbon dioxide ice , ammonia ice, or methane ice. However, the predominant use of the term ice is for water ice, technically restricted to one of the 15 known crystalline phases...
. At least a portion of the cave must have a temperature below 0 °C
Celsius
Celsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
(32 °F
Fahrenheit
Fahrenheit is the temperature scale proposed in 1724 by, and named after, the physicist Daniel Gabriel Fahrenheit . Today, the scale has been replaced by the Celsius scale in most countries; it is still in use for non-scientific purposes in the United States and a few other nations, such as...
) all year round, and water
Water
Water is an ubiquitous chemical substance that is composed of hydrogen and oxygen and is essential for all known forms of life.In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam. Water covers 71%...
must have traveled into the cave’s cold zone.
The term ice cave is often used to describe a cavity formed within ice, which is properly called a glacier cave
Glacier cave
A glacier cave is a cave formed within the ice of a glacier. Glacier caves are often called ice caves, but this term is properly used to describe bedrock caves that contain year-round ice.-Overview:...
.
Temperature Mechanisms
Bedrock
Bedrock
In stratigraphy, bedrock is the native consolidated rock underlying the surface of a terrestrial planet, usually the Earth. Above the bedrock is usually an area of broken and weathered unconsolidated rock in the basal subsoil...
caves are thermally insulated
Thermal insulation
The term thermal insulation can refer to materials used to reduce the rate of heat transfer, or the methods and processes used to reduce heat transfer....
from the surface, so commonly assume a near-constant temperature
Temperature
In physics, temperature is a physical property of a system that underlies the common notions of hot and cold; something that feels hotter generally has the higher temperature. Temperature is one of the principal parameters of thermodynamics...
approximating the annual average temperature at the surface. In some cold environments, average surface (and thus cave) temperatures are below freezing, and with surface water available in summer, ice caves are possible. However, many ice caves exist in temperate
Temperate
In geography, temperate or tepid latitudes of the globe lie between the tropics and the polar circles. The changes in these regions between summer and winter are generally mild, rather than extreme hot or cold. But in continental areas, such as central North America the variations between summer...
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
Convection
Convection is the movement of molecules within fluids . Convection is one of the major modes of heat transfer and mass transfer...
to import cold air from the surface in winter, but not warm air in summer. A typical example is an underground chamber located below a single entrance. In winter, cold dense air settles into the cave, displacing any warmer air which rises and exits the cave. In summer, the cold cave air remains in place as the relatively warm surface air is lighter and cannot enter. The cave will only exchange air when the surface air is cooler than the cave air. Some cold traps may ensnare surface snow
Snow
Snow is a type of precipitation in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by external pressure. Snowflakes...
and shade it from the summer sun
Sun
The Sun is the star at the center of the Solar System. The Earth and other matter orbit the Sun, which by itself accounts for about 99.86% of the Solar System's mass....
’s rays
Sunlight
Sunlight, in the broad sense, is the total spectrum of the electromagnetic radiation given off by the Sun. On Earth, sunlight is filtered through the atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon. Near the poles in summer, the days are longer and the...
, 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
Permafrost
In geology, permafrost or permafrost soil is soil at or below the freezing point of water for two or more years. Ice is not always present, as may be in the case of nonporous bedrock, but it frequently occurs and it may be in amounts exceeding the potential hydraulic saturation of the ground...
. For example, winter wind and an absence of snow cover may allow freezing deep enough to be protected from summer thaw, particularly in light-colored rock
Rock (geology)
In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock. In general rocks are of three types, namely, igneous, sedimentary, and ****morphic...
that does not readily absorb heat. Although the portion of a cave within this permafrost zone will be below freezing, permafrost generally does not allow water percolation
Percolation
In physics, chemistry and materials science, percolation concerns the movement and filtering of fluids through porous materials. Examples include the movement of solvents through filter paper and the movement of petroleum through fractured rock. Electrical analogs include the flow of electricity...
, so ice formations are often limited to crystals from vapor
Vapor
A vapor or vapour is a substance in the gas phase at a temperature lower than its critical temperature....
, and deeper cave passages may be arid and completely ice-free. Ice caves in permafrost need not be cold-traps (although some are), provided they do not draught significantly in summer.
Evaporative cooling - In winter, dry surface air entering a moisture-saturated cave may have an additional cooling effect due to the latent heat
Latent heat
The expression latent heat refers to the amount of energy released or absorbed by a chemical substance during a change of state that occurs without changing its temperature, meaning a phase transition such as the melting of ice or the boiling of water...
of evaporation
Evaporation
Evaporation is the vaporization of a liquid and the reverse, of condensation. A type of phase transition, it is the process by which molecules in a liquid state spontaneously become gaseous . Generally, evaporation can be seen by the gradual disappearance of a liquid from a substance when exposed...
. This may create a zone within the cave that is cooler than the rest of the cave. Because many caves have seasonally-reversing draughts, the corresponding warming of the cave through condensation
Condensation
Condensation is the change of the physical state of aggregation of matter from gaseous phase into liquid phase and the reverse of evaporation. When the transition happens from the gaseous phase into the solid phase directly, bypassing the liquid phase, the change is called deposition...
in summer may occur at a different ******** within the cave, but in any event a moisture-saturated cave environment is likely to experience much more evaporative cooling than condensative warming.
Types of Ice in Ice Caves
Different freezing mechanisms result in visually and structurally distinct types of perennial cave ice.
Ponded water - Surface water that collects and ponds in a cave before freezing will form a clear ice mass, and can be tens of metres thick and of great age. Large ice masses are plastic
Plasticity (physics)
In physics and materials science, plasticity describes the deformation of a material undergoing non-reversible changes of shape in response to applied forces. For example, a solid piece of ****l or plastic being bent or pounded into a new shape displays plasticity as permanent changes occur within...
and can slowly flow in response to gravity or pressure from further accumulations. Sculpting from air flow and sublimation may reveal ancient accumulation bands within the ice.
Accumulated snow - Compressed under the weight of ongoing accumulations, snow sliding or falling into a cave entrance may eventually form ice that is coarsely crystalline, akin to glacier
Glacier
A glacier is a perennial mass of ice which moves over land. A glacier forms in ********s where the mass accumulation of snow and ice exceeds ablation over many years...
ice. True underground glaciers are rare.
Ice formations - Water that freezes before ponding may form icicle
Icicle
An icicle is a spike of ice formed when water dripping or falling from an ****** freezes. Typically, icicles will form when ice or snow is melted by either sunlight or some other heat source , and the resulting melted water runs off into an area where the ambient temperature is below the freezing...
s, ice-stalagmite
Stalagmite
A stalagmite is a type of speleothem that rises from the floor of a limestone cave due to the dripping of mineralized solutions and the deposition of calcium carbonate. The corresponding formation on the ceiling of a cave is known as a stalactite...
s, ice columns or frozen waterfall
Waterfall
A waterfall is a place where flowing water rapidly drops in elevation as it flows over a steep region or a cliff.-Formation :Typically, a river flows over a large step in the rocks that may have been formed by a fault line. As it increases its velocity at the edge of the waterfall, it plucks...
s.
Airborne moisture (water vapor) – Freezing vapor can form frost
Frost
Frost is the solid deposition of water vapor from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air. Frost crystals' size differ depending on time and water vapor available. Frost is also usually translucent in appearance. There are many types of...
crystals, frost feathers and two-dimensional ice plates on the cave walls and ceiling.
Needle ice
Needle ice
Needle ice is a phenomenon that occurs when the temperature of the soil is above 0°C and the surface temperature of the air is below 0°C. The subterranean moisture is brought to the surface via capillary action....
- 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
Castleguard Cave
Castleguard Cave is a limestone cave located at the north end of Banff National Park in the Rocky Mountains of Canada. With 20,357m of surveyed passages , it is Canada’s longest cave, and its fifth deepest at 384m...
in Alberta
Alberta
Alberta is one of Canada's prairie provinces. It became a province on September 1, 1905.Alberta is located in western Canada, bounded by the provinces of British Columbia to the west and Saskatchewan to the east, the Northwest Territories to the north, and the U.S. state of Montana to the south....
.
تعليق