USGS/Cascades Volcano Observatory, Vancouver, Washington
DESCRIPTION:
Volcanic Gases and Emissions,
Fumaroles and Solfataras
Volcanic Gases and Emissions
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MSH81_collecting_gas_samples_base_dome_09-24-81.jpg
USGS geologists collect gas samples around the dome. Samples were gathered from vents on the dome and crater floor, and were used to monitor changes in chemical composition. Additionally, sulfur dioxide gas was measured from a specially-equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano. During eruptions, emission rates typically increased to 5 to 10 times their pre-eruptive value.
USGS Photograph taken on September 24, 1981, by Thomas J. Casadevall.
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From:
Miller, 1989,
Potential Hazards from Future Eruptions in California:
USGS Bulletin 1847
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All magmas contain dissolved gases that are released during eruptions as
well as between eruptive episodes. Gas emission often precedes eruptions,
and gases can issue from fumaroles
for hundreds or thousands of years
after an eruption has ended.
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Volcanic gases usually consist predominantly of steam, followed in
abundance by carbon dioxide and compounds of sulfur and chlorine. Minor
amounts of carbon monoxide, fluorine and boron compounds, ammonia,
and several other compounds are found in some volcanic gases.
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Distribution of volcanic gases is mostly controlled by the wind; gases may
be concentrated near a vent but become diluted rapidly downwind. Even
very dilute gases can have a noticeable odor and can harm plants and
some animals tens of kilometers downwind from a vent.
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Close to a vent, volcanic gases can endanger life and health as well as
property. Acids and ammonia and other compounds present in volcanic
gases can damage eyes and respiratory systems of people and animals,
and accumulation in closed depressions of gases heavier than air, like
carbon dioxide, can suffocate people or animals that enter such basins. Other
harmful effects of volcanic gases on plants and animals, and corrosion of
metals and other property, can be severe near and downwind form
especially active vents.
From:
Myers, et.al., 1997,
What Are Volcanic Hazards?:
USGS FactSheet 002-97
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Volcanoes emit gases during eruptions.
Even when a volcano is not erupting,
cracks in the ground allow gases to reach the surface through small
openings called fumaroles.
Ninety percent of all gas emitted by volcanoes
is water vapor (steam), most of which is heated ground water (underground
water from rain fall and streams). Other common volcanic gases are carbon
dioxide, sulfur dioxide, hydrogen sulfide, hydrogen, and fluorine. Sulfur
dioxide gas can react with water droplets in the atmosphere to create
acid rain,
which causes corrosion and harms vegetation. Carbon dioxide is
heavier than air and can be trapped in low areas in concentrations that are
deadly to people and animals. Fluorine, which in high concentrations is
toxic, can be adsorbed onto volcanic ash particles that later fall to the
ground. The fluorine on the particles can poison livestock grazing on
ash-coated grass and also contaminate domestic water supplies.
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Cataclysmic
eruptions, such as the
June 15, 1991, eruption of Mount Pinatubo
(Philippines), inject huge amounts of sulfur dioxide gas into the
stratosphere, where it combines with water to form an aerosol (mist) of
sulfuric acid. By reflecting solar radiation, such aerosols can
lower the Earth's average surface temperature
for extended periods of time by several
degrees Fahrenheit. These sulfuric acid aerosols also contribute to
the destruction of the ozone layer by altering chlorine and nitrogen
compounds in the upper atmosphere.
From:
Hoblitt, et.al., 1987,
Volcanic Hazards with Regard to Siting Nuclear-Power Plants
in the Pacific Northwest:
USGS Open-File Report 87-297.
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All magmas contain dissolved gases that are released both during and
between eruptive episodes.
Volcanic gases generally consist predominantly of steam (H2O),
followed in abundance by carbon dioxide
and compounds of sulfur and chlorine ...
Minor amounts of carbon
monoxide, fluorine and boron compounds, ammonia, and several other
compounds are found in some
volcanic gases. ...
From:
Wright and Pierson, 1992, Living With Volcanoes, The
U.S. Geological Survey's Volcano Hazards Program:
USGS Circular 1973
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Volcanic gases:
The most common gases associated with active volcanoes are water vapor, carbon
dioxide, sulfur dioxide, hydrogen sulfide, hydrogen, helium, carbon monoxide,
and hydrochloric acid. Lesser amounts of hydrofluoric acid, nitrogen, argon,
and other compounds are commonly associated with active volcanoes as well.
Volcanic gases rarely reach populated areas in lethal concentrations, although
sulfur dioxide can react with the atmosphere downwind and fall as acid rain to
cause corrosion and a host of other effects. People with respiratory or heart
diseases are especially susceptible to volcanic gases (fume). Carbon
dioxide is heavier than air and tends to collect in depressions, where it can
occur in lethal concentrations and cause suffocation. On occasion, toxic
concentrations of fluorine from hydrofluoric acid have been absorbed onto ash
and ingested by livestock or leached into domestic water supplies.
From:
Tilling, 1985,
Volcanoes:
USGS General Interest Publication
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Fumaroles,
which emit mixtures of steam and other gases,
are fed by conduits that pass through the water table
before reaching the surface of the
ground. Hydrogen sulfide (H2S), one of the typical gases issuing from fumaroles,
readily oxidizes to sulphuric acid and native sulfur. This accounts for the
intense chemical activity and brightly colored rocks in many
thermal areas.
From:
Gardner, et.al., 1995,
Potential Volcanic Hazards from Future Activity of
Mount Baker, Washington:
USGS Open-File Report 95-498
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Fumarole - a vent that releases volcanic gases,
including water vapor (steam).
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Fumarolic activity - volcanic gas emissions, that may be accompanied by a
change in the temperature of the gases of fluids emitted.
From:
Tilling, 1985,
Volcanoes:
USGS General Interest Publication
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Fumaroles (also called solfataras),
which emit mixtures of steam and other gases,
are fed by conduits that pass through the water table before reaching the surface of the
ground. Hydrogen sulfide (H2S), one of the typical gases issuing from fumaroles,
readily oxidizes to sulphuric acid and native sulfur. This accounts for the
intense chemical activity and brightly colored rocks in many
thermal areas.
From:
Myers and Brantley, 1995,
Volcano Hazards Fact Sheet: Hazardous Phenomena at Volcanoes:
USGS Open-File Report 95-231
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Volcanoes emit gases during eruptions. Even when
a volcano is not erupting, cracks in the ground allow gases to vent
to the surface through fumaroles.
Mount St. Helens, Washington - 1980-81
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MSH83_USGS_scientists_COSPEC_on_SugarBowl_10-21-83.jpg
USGS scientists use a COSPEC (correlation spectrometer), to measure sulfur-dioxide gases being emitted from the dome. Setup on Sugar Bowl, located on the northwest flank of Mount St. Helens.
USGS Photograph taken on October 21, 1983, by Lyn Topinka.
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[TIF Format, 18 M]
From:
Brantley and Topinka, 1984,
Volcanic Studies at the U.S. Geological Survey's David A. Johnston Cascades
Volcano Observatory, Vancouver, Washington:
Earthquake Information Bulletin, March-April 1984, v.16, no.2
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Gas emissions are measured
regularly in conjunction with seismicity and ground
deformation to monitor eruptive activity. Mount St. Helens continuously emits
volcanic gas from fumaroles on and around the dome. Most of the gas emitted by
the volcano is water vapor, but emissions also include sulfur dioxide, carbon
dioxide, hydrogen, and lesser amounts of helium, carbon monoxide, hydrogen
sulfide, and hydrogen chloride.
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Gas studies include (1) frequent airborne measurements of sulfur dioxide and,
in 1980 and 1981, carbon dioxide in the plume and (2) less frequent sampling of
gases from crater fumaroles.
The emissions of sulfur dioxide are measured in the plume by a
correlation spectrometer (COSPEC) designed originally
for pollution studies. The instrument
measures the amount of solar ultraviolet light absorbed by sulfur dioxide
in the plume and compares it with an internal standard.
Three to six traverses are made beneath the plume at right angles to
the plume trajectory several times
each week to calculate daily emission rates.
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The emission rates of sulfur dioxide peaked during summer 1980 at about 1,500
tons per day, decreased rapidly in late 1980, and remained low at about 100 tons
per day through 1983. Emission rates of carbon dioxide decreased rapidly in
late 1980 until they were below the detection limit of 1,000 tons per day.
These patterns correspond generally to a change in eruptive style from the
explosive activity of 1980 to the now predominantly nonexplosive activity. The
patterns suggest steady outgassing of a single batch of magma under the volcano
to which no significant new magma has been added since mid-1980.
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Increased rates of sulfur dioxide emissions measured before several nonexplosive
eruptions are interpreted as the result of accelerated degassing of a small
volume of magma as it moved toward the surface. During the nonexplosive
eruptions, gas emissions remained elevated during the active extrusion of lava
and generally dropped to preeruption levels once extrusion stopped. The
occasional outbursts of gas and tephra are accompanied by brief, sudden
increases in the emission rate of sulfur dioxide, water vapor, and probably
other gases as well. It is not known whether this increase in gas is derived
directly from magma within the dome or released during periodic, geyserlike
flashing of a shallow hydrothermal system.
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Mount St. Helens Volcanic Gas Emissions Menu
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Baker81_gas_sampling_fumarole_mount_baker_1981.jpg
Sampling gases, fumarole, on top of Mount Baker, Washington.
USGS Photograph taken in 1981 by W. Chadwick.
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From:
Hyde and Crandell, 1978,
PostGlacial Volcanic Deposits at Mount Baker, Washington,
and Potential Hazards from Future Eruptions:
USGS Professional Paper 1022-C
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Most hydrothermal activity at Mount Baker
is concentrated within Sherman Crater,
although a small area of fumaroles,
known as the Dorr Fumarole Field, is
present on the north flank of the volcano at an altitude of 2,300 to 3,500
meters.
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Mount Baker Volcano Menu
From:
Swanson, et.al., 1989,
IGC Field Trip T106: Cenozoic Volcanism in the Cascade Range and
Columbia Plateau, Southern Washington and Northernmost Oregon:
American Geophysical Union Field Trip Guidebook T106
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Jökulhlaups (glacial-outburst floods) have been recorded from the
Zigzag, Ladd, Coe, and White River Glaciers (at Mount Hood). ...
The more frequent outbursts from White River Glacier
may be due in part to an increase in size of the
fumarole field at the head of the glacier at Crater Rock.
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Mount Hood Volcano Menu
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[Volcanic Gas Menu] ...
[PROJECT: Volcanic Emissions Menu] ...
[Glossary of Hazards, Features, and Terminology] ...
URL for CVO HomePage is:
<http://vulcan.wr.usgs.gov/home.html>
URL for this page is:
<http://vulcan.wr.usgs.gov/Glossary/Emissions/description_gases.html>
If you have questions or comments please contact:
<GS-CVO-WEB@usgs.gov>
05/12/05, Lyn Topinka