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Volatiles are the group of
chemical element In chemistry, an element is a pure Chemical substance, substance consisting only of atoms that all have the same numbers of protons in their atomic nucleus, nuclei. Unlike chemical compounds, chemical elements cannot be broken down into simp ...
s and
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entity, molecular entities) composed of atoms from more than one chemical element, element held together by chemical bonds. A homonuclear molecule, m ...
s that can be readily
vaporized File:10. Ладење при испарување.ogv, 280px, Demonstration of evaporative cooling. When the sensor is dipped in ethanol and then taken out to evaporate, the instrument shows progressively lower temperature as the ethanol evapora ...
. In contrast with volatiles, elements and compounds that are not readily vaporized are known as
refractory A refractory material or refractory is a material that is resistant to decomposition by heat, pressure, or chemical attack, and retains strength and form at high temperature Temperature is a physical quantity that expresses hot and cold. ...
substances. On planet Earth, the term 'volatiles' often refers to the volatile components of
magma Magma () is the molten or semi-molten natural material from which all igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others ...

magma
. In
astrogeology Surface of Mars in a false-color photograph by the Viking 2 lander December 9, 1977. Planetary geology, alternatively known as astrogeology or exogeology, is a planetary science Planetary science or, more rarely, planetology, is the scientif ...
volatiles are investigated in the crust or
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
of a planet or moon. Volatiles include
nitrogen Nitrogen is the chemical element upright=1.0, 500px, The chemical elements ordered by link=Periodic table In chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science ...

nitrogen
,
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
,
ammonia Ammonia is a compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fort ...

ammonia
,
hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. Hydrogen is the lightest element. At standard temperature and pressure, standard conditions hydrogen is a gas of diatomic molecules having the che ...

hydrogen
,
methane Methane (, ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Earth ...
,
sulfur dioxide Sulfur dioxide (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering OrganizationsNational Adhering Organizations in chemistry are the organizations that work as the autho ...
,
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 ...

water
and others.


Planetary science

Planetary scientists often classify volatiles with exceptionally low melting points, such as hydrogen and
helium Helium (from el, ἥλιος, helios Helios; Homeric Greek: ), Latinized as Helius; Hyperion and Phaethon are also the names of his father and son respectively. often given the epithets Hyperion ("the one above") and Phaethon ("the shining" ...

helium
, as gases (as in
gas giant A gas giant is a giant planet The giant planets constitute a diverse type of planet A planet is an astronomical body orbiting a star or Stellar evolution#Stellar remnants, stellar remnant that is massive enough to be Hydrostatic equilib ...
), whereas those volatiles with
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
s above about 100 
K
K
(–173 °C, –280 °F) are referred to as ices. The terms "gas" and "ice" in this context can apply to compounds that may be solids, liquids or gases. Thus,
Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant A gas giant is a giant planet composed mainly of hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and at ...

Jupiter
and
Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It only has one-eighth the average density of Earth; how ...

Saturn
are gas giants, and
Uranus Uranus is the seventh planet from the Sun. Its name is a reference to the Greek god of the sky, Uranus, who, according to Greek mythology Greek mythology is the body of myths originally told by the Ancient Greece, ancient Greeks, and ...

Uranus
and
Neptune Neptune is the eighth and farthest-known Solar planet from the Sun. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. It is 17 times the mass of Earth, slightly mor ...

Neptune
are
ice giant An ice giant is a giant planet composed mainly of elements heavier than hydrogen Hydrogen is the chemical element with the Symbol (chemistry), symbol H and atomic number 1. With a standard atomic weight of , hydrogen is the lightest el ...
s, even though the vast majority of the "gas" and "ice" in their interiors is a hot, highly dense fluid that gets denser as the center of the planet is approached. Inside of Jupiter's orbit, cometary activity is driven by the sublimation of water ice. Supervolatiles such as
CO
CO
and
CO2
CO<sub>2</sub>
have generated cometary activity as far out as .


Igneous petrology

In
igneous petrologyIgneous petrology is the study of igneous rock Igneous rock (derived from the Latin Latin (, or , ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken in the ar ...
the term more specifically refers to the volatile components of
magma Magma () is the molten or semi-molten natural material from which all igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others ...

magma
(mostly
water vapor (99.9839 °C) , - , Boiling point The boiling point of a substance is the temperature at which the vapor pressure 280px, The ''pistol test tube'' experiment. The tube contains alcohol and is closed with a piece of cork. By heating th ...
and carbon dioxide) that affect the appearance and explosivity of
volcanoes A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plat ...
. Volatiles in a magma with a high viscosity, generally
felsic In geology Geology (from the Ancient Greek γῆ, ''gē'' ("earth") and -λoγία, ''-logia'', ("study of", "discourse")) is an Earth science concerned with the solid Earth, the rock (geology), rocks of which it is composed, and the processes ...
with a higher silica (SiO2) content, tend to produce eruptions that are explosive. Volatiles in a magma with a low viscosity, generally
mafic A mafic mineral or rock is a silicate mineral Silicate minerals are rock-forming mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composit ...
with a lower silica content, tend to vent and can give rise to a
lava fountain of pāhoehoe lava, Hawaii, United States , Iceland in 1984 Lava is molten Rock (geology), rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon. Magma is generated by the inte ...
.


Volatiles in magma

Some
volcanic eruption Several types of volcanic eruptions—during which lava Lava is magma once it has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or t ...

volcanic eruption
s are
explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion An explosion is a rapid expansion in volume Volume is a expressing the of enclosed by a . ...

explosive
because the mixing between
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 ...

water
and
magma Magma () is the molten or semi-molten natural material from which all igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others ...

magma
reaching the surface, releases energy suddenly. Moreover, in some cases, the eruption is caused by volatiles dissolved in the magma. (2008): Fundamentals of Physical Volcanology. Blackwell Publishing, Malden USA Approaching the surface,
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

pressure
decreases and the volatiles evolve creating bubbles that circulate in the
liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physics concerned with the motions of physical objects, ...

liquid
. The bubbles are connected together forming a network. This especially increments the fragmentation into small
drops Drop, DROP, drops or DROPS may refer to: * Drop (liquid) 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 continually Deformation ...
or spray or coagulate clots in
gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

gas
. Generally, 95-99% of magma is liquid rock. However, the small percentage of
gas Gas is one of the four fundamental states of matter In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

gas
present, represents a very large
volume Volume is a scalar quantity expressing the amount Quantity or amount is a property that can exist as a multitude Multitude is a term for a group of people who cannot be classed under any other distinct category, except for their shared fact ...

volume
when it expands on reaching
atmospheric pressure Atmospheric pressure, also known as barometric pressure (after the barometer A barometer is a scientific instrument that is used to measure air pressure Atmospheric pressure, also known as barometric pressure (after the barometer), is the ...
. Gas is a preponderant part in a volcano system because it generates explosive eruptions. Magma in the
mantle Mantle may refer to: *Mantle (geology) A mantle is a layer inside a planetary body A planet is an astronomical body Astronomy (from el, ἀστρονομία, literally meaning the science that studies the laws of the stars) is a n ...
and lower crust has lot of volatiles within and water and
carbon dioxide Carbon dioxide (chemical formula A chemical formula is a way of presenting information about the chemical proportions of s that constitute a particular or molecule, using symbols, numbers, and sometimes also other symbols, such as pare ...

carbon dioxide
are not the only volatiles that
volcanoes A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plat ...
release. Also they leak
hydrogen sulfide Hydrogen sulfide is a chemical compound A chemical compound is a 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 havi ...

hydrogen sulfide
and
sulfur dioxide Sulfur dioxide (IUPAC The International Union of Pure and Applied Chemistry (IUPAC ) is an international federation of National Adhering OrganizationsNational Adhering Organizations in chemistry are the organizations that work as the autho ...
. Sulfur dioxide is usually possible to find in
basaltic Basalt (, ) is a fine-grained extrusive A volcanic rock from Italy with a relatively large six-sided phenocryst (diameter about 1 mm) surrounded by a fine-grained groundmass, as seen in thin section under a petrographic microscope Extr ...

basaltic
and
rhyolite Rhyolite ( ) is the most silica Silicon dioxide, also known as silica, is an oxide An oxide () is a chemical compound A chemical compound is a chemical substance A chemical substance is a form of matter In classical physics and ...

rhyolite
rocks. Volcanoes also release a high amount of
hydrogen chloride The compound Compound may refer to: Architecture and built environments * Compound (enclosure), a cluster of buildings having a shared purpose, usually inside a fence or wall ** Compound (fortification), a version of the above fortified with ...

hydrogen chloride
and
hydrogen fluoride Hydrogen fluoride is a chemical compound with the chemical formula . This colorless gas or liquid is the principal industrial source of fluorine, often as an aqueous solution called hydrofluoric acid. It is an important feedstock in the preparation ...

hydrogen fluoride
as volatiles.


Solubility of volatiles

There are three main factors that affect the dispersion of volatiles in magma: confining
pressure Pressure (symbol: ''p'' or ''P'') is the force In physics Physics is the natural science that studies matter, its Elementary particle, fundamental constituents, its Motion (physics), motion and behavior through Spacetime, space ...

pressure
, composition of magma,
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 energy refers to several distinct physical concept ...

temperature
of magma. Pressure and composition are the most important parameters. To understand how the magma behaves rising to the surface, the role of ''solubility'' within the magma must be known. An empirical
law Law is a system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its bounda ...
has been used for different magma-volatiles combination. For instance, for water in magma the
equation In mathematics Mathematics (from Greek: ) includes the study of such topics as numbers ( and ), formulas and related structures (), shapes and spaces in which they are contained (), and quantities and their changes ( and ). There is no ge ...

equation
is n=0.1078 P where ''n'' is the amount of dissolved gas as weight percentage (wt%), ''P'' is the pressure in
megapascal The pascal (symbol: Pa) is the SI derived unit of pressure used to quantify internal pressure, stress (physics), stress, Young's modulus, and ultimate tensile strength. The unit, named after Blaise Pascal, is defined as one Newton (unit), newton ...
(MPa) that acts on the magma. The value changes, for example for water in rhyolite n = 0.4111 P and for the carbon dioxide n = 0.0023 P. These simple equations work if there is only one volatile in a magma. However, in reality, the situation is not so simple because there are often multiple volatiles in a magma. It is a complex chemical interaction between different volatiles. Simplifying, the solubility of water in rhyolite and basalt is function of pressure and depth below the surface in absence of other volatiles. Both basalt and rhyolite lose water with decreasing pressure as the magma rises to the surface. The solubility of water is higher in rhyolite than in basaltic magma. Knowledge of the solubility allows the determination of the maximum amount of water that might be dissolved in relation with pressure. If the magma contains less water than the maximum possible amount, it is ''undersaturated'' in water. Usually insufficient water and carbon dioxide exist in the deep crust and mantle, so magma is often ''undersaturated'' in these conditions. Magma becomes ''saturated'' when it reaches the maximum amount of water that can be dissolved in it. If the magma continues to rise up to the surface and more water is dissolved, it becomes ''supersaturated''. If more water is dissolved in magma, it can be ejected as ''bubbles'' or water vapor. This happens because pressure decreases in the process and velocity increases and the process has to balance also between decrease of solubility and pressure. Making a comparison with the solubility of carbon dioxide in magma, this is considerably less than water and it tends to exsolve at greater depth. In this case water and carbon dioxide are considered independent. What affects the behavior of the magmatic system is the depth at which carbon dioxide and water are released. Low solubility of carbon dioxide means that it starts to release bubbles before reaching the magma chamber. The magma is at this point already supersaturated. The magma enriched in carbon dioxide bubbles, rises up to the roof of the chamber and carbon dioxide tends to leak through cracks into the overlying caldera. Basically, during an eruption the magma loses more carbon dioxide than water, that in the chamber is already supersaturated. Overall, water is the main volatile during an eruption.


Nucleation of bubbles

Bubble
nucleation Nucleation is the first step in the formation of either a new thermodynamic phase or a new structure via self-assembly File:Iron oxide nanocube.jpg, upright=1.2, Transmission electron microscopy image of an iron oxide nanoparticle. Regularly ar ...

nucleation
happens when the a volatile becomes saturated. Actually the bubbles are composed of molecules that tend to aggregate spontaneously in a process called homogeneous nucleation. The
surface tension Surface tension is the tendency of liquid A liquid is a nearly incompressible In fluid mechanics Fluid mechanics is the branch of physics concerned with the mechanics Mechanics (Ancient Greek, Greek: ) is the area of physi ...

surface tension
acts on the bubbles shrinking the surface and forces them back to the liquid. The nucleation process is greater when the space to fit is irregular and the volatile molecules can ease the effect of surface tension. The nucleation can occur thanks to the presence of solid
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, which are stored in the magma chamber. They are perfect potential nucleation sites for bubbles. If there is no nucleation in the magma the bubbles formation might appear really late and magma becomes significantly supersaturated. The balance between supersaturation pressure and bubble's radii expressed by this equation: ∆P=2σ/r, where ∆P is 100 MPa and σ is the surface tension. If the nucleation starts later when the magma is very supersaturated, the distance between bubbles becomes smaller. Essentially if the magma rises rapidly to the surface, the system will be more out of equilibrium and supersaturated. When the magma rises there is competition between adding new molecules to the existing ones and creating new ones. The distance between molecules characterizes the efficiency of volatiles to aggregate to the new or existing site. Crystals inside magma can determine how bubbles grow and nucleate.


See also

*
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


References


External links


Glossary
of planetary astronomy terms

of Costa Rican volcanoes.

Planetary Science Research Discoveries {{meteorites Petrology Volcanology Planetary geology Ice Astrobiology Origins Prebiotic chemistry