Volcanic Gases Volcanic Gases and temperature of the magma and the gas content determines if an eruption will be effusive or explosive. On a global scale, volcanic gases produced our atmosphere and our oceans. Without the atmosphere and oceans, life would not have evolved on Earth. Gases emitted by volcanoes continue to influence the atmosphere but not to the extent of man-made sources. Gases also pose a hazard at many volcanoes. At other volcanoes, the gradual release of gas acts as an irritant and may pose a long-term health hazard. Right: gas sampling at vents on the floor of Halemaumau Crater, Kilauea volcano, Hawaii. Photo by Steve Mattox. Average Compositions and Trace Gases Most Common Gases Water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2) are the most common volcanic gases.

Other Gases In lesser amounts, volcanoes release carbon monoxide (CO), hydrogen sulfide (H2S), carbonyl sulfide (COS), carbon disulfide (CS2), hydrogen chloride (HCl), hydrogen (H2), methane (CH4), hydrogen flouride (HF), boron, hydrogen bromine (HBr), mercury (Hg) vapor, organic compounds, even gold. From Cadle (1980). Mercury is released by most volcanoes and has been measured at Kilauea, Mauna Loa, Hekla, Erebus, at Mount St. Helens (Siegel and Siegel, 1987). Kilauea produces about 270 tons of mercury each year and has been identified as the source for mercury on Oahu, 320 km away. Condensates, sublimates, and incrustations were studied at Merapi volcano by Symonds and others (1987).

The following elements were found: Se, Re, Bi, and Cd at concentrations 100,000 that in the ; Au, Br, In, Pb, and W at concentrations 100,000 to 10,000 that in the magma; Mo, Cl, Cs, S, Sn, and Ag at concentrations 10,000 to 1,000 that in the magma; As, Zn, F, and Rb at concentrations 1,000 to 100 that in the magma; Cu, K, Na, Sb, Ni, Ga, V, Fe, Mn, and Li at concentrations 100 to 1 that in the magma. Gold has condensed from volcanic gases. Meeker and others (1991) reported gold at Mount Erebus, Antarctica. They found gold in the plume near the , in the air up to 1000 km from the volcano and in near surface samples. Most of these gases originate in the mantle and are transported to the crust and surface by complex interactions with magma and rocks encountered along the way. In general, the gases are dissolved in the magma.

At shallow depths, as pressure on the magma decreases, the gases leave the magma (exsolve). The gases can interact with surrounding rocks or continue to the surface. Inset Image: Sulfur deposits near the summit of Griggs volcano, Alaska. Photo by Jay Robinson. Gas Compositions and Tectonic Setting Symonds, Rose, Bluth, and Gerlach (1994) published a list of compositions of high-temperature volcanic-gas samples. They also have a comprehensive list of published sources for high-quality volcanic-gas data . Convergent-plate volcanoes: Etna, Mount St. Helens, Merapi Divergent-plate volcanoes: Erta Ale, Surtsey Hot-spot volcano: Kilauea Equilibrium compositions, temperatures, and log fO2 values of high-temperature and low-pressure (1 bar) volcanic gases. Concentrations are in mole %; log fO2 given in log bars.

There are three primary ways that gas geochemists collect data: Estimates from Rocks, Minerals, and Inclusions Scientists can determine the amount and types of gas in a rock, in the minerals within a rock, or in the gas inclusions in minerals or glass (Ihinger and others, 1994). The methods fall into four classes: bulk extraction, energetic particle bombardment, vibrational spectroscopic techniques, and phase equilibrium studies. These method are used in experimental studies and for rocks from all tectonic settings, historic eruptions, and large pre-historic eruptions. Some methods have been found to underestimate the observed amount of gas released during some historic eruption. Thus, the methods may give an estimate of the minimum amount of gas released. For example, Gerlach and McGee (1994) used melt inclusion data to estimate 0.08 Mt of SO2 emitted by the Mount St. Helens eruption. TOMS, COSPEC and leachate data provide an estimate of 2 Mt. Gerlach and McGee suggested a vapor phase carried most of the SO2.

Direct Sampling The easiest, but often the most difficult, way to collect a sample is by hand, placing a container directly in the gases. This method was perfected by the late Werner Giggenbach. Difficulty arises because of the high temperatures, dangers associated with being close to vents, and the possibility of contamination of the sample by the atmosphere. Left diagram: Evacuated-bottle sampling scheme. Direct samples are most commonly collected in solution-filled bottles (4N NaOH in a titanium or silica tube) and then returned to the lab for analyses. In the drawing on the left, the enlargement shows an evacuated glass bottle. The solution contains NaOH and collected H20), H2S, SO2, HCl, HF, and CO2. The headspace contains collected H20, H2, CH4, O2, CO, N2, Ar, Ne. Right diagram: Flow-through sampling scheme. Figure from Sutton and others, 1992). Right: Volcanic gases from Kilauea collected using the flow-through sampling scheme. Photo by Steve Mattox. Another way to measure gases released by a volcano is to collect fresh ash samples (before it rains) and pour distilled water through the ash.

Then after the liquid passes through the ash it is collected. This is the leachate. The leachate is analyzed for Cl (chloride), F, SO4 and pH. The ratio of Cl to S increases prior to eruptions. Leachates were measured prior to the 1980 eruption at Mount St. Helens (Nehring and Johnston, 1981). Cl and SO4 were measured in the field and the S/Cl ratio was observed to increase gradually from March 28 to May 18. The S/Cl ratio increased 30 times over its initial value prior to an eruption of Asama volcano in Japan. At Fuego, in Guatemala, the S/Cl ratio increased 5 times over its initial value and the size of the change was proportional to eruption size. Continuous direct sampling is a relatively new method to monitor gases. Results of measurements are telemetered to safe locations off the volcano. At Mount St. Helens, upward-moving fresh Remote Sensing The COSPEC (correlation spectrometer) Volcanologist found an application for an instrument used to measure pollution.

A correlation spectrometer (COSPEC) is designed to measure the amount of sulfur dioxide in a passing air mass (or volcanic plume). The spectrometer compares the amount of solar ultraviolet light absorbed by sulfur dioxide in the plume to an internal standard. Numerous measurements are made to achieve reliable results. COSPEC used to measure SO2 released by Merapi Volcano. Use of vehicle-mounted (left) and tripod-mounted (right) ground-based COSPEC. A. Side view. B. Front view. C. Typical data. From Sutton and others (1992). Balloons Balloons are used to take samples in or to carry instruments into aerosol layers. For example, Sheridan and others (1992) collected samples of atmospheric particles from the Pinatubo eruption by releasing balloons from Laramie, Wyoming. Most of the fine particles were H2SO4 droplets. Other larger particles were supermicrometer sulfate particles and composite sulfate/crustal particles. Deshler and others (1992) also used balloons to study the aerosols in the Pinatubo layer.

Their study showed that 90% of the SO2 had been converted to H2SO4 aerosol within one month of the eruption. They also measured pressure, temperature, ozone, and particle density. LIDAR LIDAR is a ground-based remote sensing method that is used to measure the distribution and amounts of several gases in the atmosphere. NOAA has a fine page that explains LIDAR data. TOMS TOMS image of the Mt. Pinatubo SO2 plume two days after the June 15th eruption The red dot marks the location of the volcano. The concentration of sulfur dioxide is expressed in units of milli-atmosphere centimeters, which gives the total column abundance in the atmospheric column Image created by Gregg Bluth and Arlin Krueger, NASA Goddard Space Flight Center. The Total Ozone Mapping Spectrometer(TOMS) is used for high resolution mapping and measurements of the ozone layer. TOMS also detects volcanic eruptions and measures the amount of sulfur dioxide released. TOMS was used to measure the sulfur dioxide clouds from three explosive eruptions of the Peak vent of Mount Spurr during the Summer of 1992.

AVHRR The Advanced Very High Resolution Radiometer (AVHRR) is used to track the aerosol layer produced by eruptions. For example, during the Pinatubo eruption, AVHRR showed that the layer circled the Earth in 21 days and that it had inhomogeneities that persisted for more than two months. The layer covered 42% of the Earth after only two months, over twice the area of El Chichon in the same amount of time. Data gathered allowed an estimate of the net global cooling effect of 0.5 degree C for a period of 2-4 years after the eruption (Stowe and others, 1992). Maps show thickness of aerosol optical products prior to and 20 days after the 1991 eruption of Pinatubo. Photo credit: G.J., Orme, Department of the Army. Monitoring Volcanic Gases (By S. Grocke, 2010) Understanding volcanic gases is essential to understanding how and why volcanoes erupt. First, it is important to realize that gases can be both dissolved in a .

Gas emissions as well as the wind speed and wind direction are periodically sampled and get transmitted every 10 minutes to HVO. This allows HVO to monitor degassing at the active vent almost instantaneously. The Origin of the Atmosphere The Origin of the Atmosphere Two models are most favored for the origin of the atmosphere: outgassing or accretion. Outgassing is related to the differentiation of the Earth and the release of gases by volcanoes. Assuming that the gases we presently observe were also released by early volcanoes the atmosphere would be made of water vapor (H2O), carbon monoxide (CO), carbon dioxide (CO2), hydrochloric (HCl), methane (CH4), ammonia (NH3), nitrogen (N2), & sulfur gases. The atmosphere was reducing (no free oxygen). The present-day atmosphere is quite different: 78% nitrogen, 21% oxygen, 1% argon, 0.03% carbon dioxide plus small amounts of water vapor Early in Earth history, water vapor formed clouds, rain, and ultimately all of the surface water (oceans, ground water, lakes, rivers, glaciers).

The presence of the ancient oceans and lakes is recorded by different types of sedimentary rocks. Perhaps the best geologic evidence for the composition of the early atmosphere is the presence and abundance of Banded Iron Formations. These rocks are made of layers of sulfide minerals (evidence for a reducing environment) and chert or fine-grained quartz. These rocks are not present in rocks younger than 1.8 - 2.5 billions of years ago, when oxygen starting becoming more abundant. The amount of carbon dioxide was reduced by chemical weathering of minerals at the surface: CaSiO3 + CO2 <-> CaCO3 + SiO2. The amount of oxygen increased due to early life forms, like the algae in stromatolites. The introduction of red beds, sedimentary rocks with ferric oxide (hematite) cement, to the rock record indicates the addition of free oxygen to the atmosphere. Photo Inset: Gas plume as enters the Pacific Ocean at Kilauea volcano, Hawaii. Photo copyrighted by Paul J. Buklarewicz. Kasting, J.F., 1993: Earth's early atmosphere. Science, v. 259, p.

920-926. Man Versus the Volcano Do humans add more gases to the atmosphere or do volcanoes? It's a simple question with a complicated answer. Reaching a good estimate is important in guiding global policy for standards to reduce emissions from man-made sources of gases. Carbon Dioxide Present-day carbon dioxide (CO2) emissions from subaerial and submarine volcanoes are uncertain at the present time. Gerlach (1991) estimated a total global release of 3-4 x 10E12 mol/yr from volcanoes. While this is a conservative estimate, man-made (anthropogenic) CO2 emissions overwhelm this estimate by at least 150 times. Sulfur Emissions Andres and Kasgnoc (1997) estimated the time-averaged inventory of subaerial volcanic sulfur emissions. There inventory was based upon the 25 year history of making sulfur measurements, primarily sulfur dioxide (SO2), at volcanoes. Actual measurements of subaerial volcanic sulfur dioxide emissions indicate a time-averaged flux of 13 Tg/yr sulfur dioxide from early 1970 to 1997.

[Note: a Tg is equal to 10E12 grams]. About 4 Tg come from explosive eruptions and 9 Tg is released by passivedegassing, in an average year. When considering the other sulfur species also present in volcanic emissions, a time-averaged inventory of subaerial volcanic sulfur emissions is 10.4 Tg/yr sulfur. Volcanoes and other natural processes release approximately 24 Tg of sulfur to the atmosphere each year. Thus, volcanoes are responsible for 43% of the total natural S flux each year. Man's activities add about 79 Tg sulfur to the atmosphere each year. In an average year, volcanoes release only 13% of the sulfur added to the atmosphere compared to anthropogenic sources. Andres and Kasgnoc (1997) noted that the bulk of the anthropogenic flux is located in the northern hemisphere while volcanic fluxes occur in much more focused belts around the world. Gases from Kilauea provides a comparison of a man-made sulfur dioxide gas leaked at a refinery to the gas released by a volcano.

Annual Average Global Emissions of HCl, HF, and HBr, in Tg Source Data compiled by Cadle (1980). Most of the gases emitted by the ocean return to the oceans. Heavy Metals Volcanoes also release heavy metal elements as particulate matter. Buat-Menard and Arnold (1978) looked at heavy metals released by Etna. Compared to anthropogenic (man-made) sources, the amount of lead released by Etna is insignificant, the amounts of cadmium, mercury, copper, and zinc are comparable; and the amount of selenium is greater than other sources in the Mediterranean atmospheric environment. Sources of Information: Andreae M.O., 1990, Ocean-atmosphere interaction in the global biogeochemical sulfur cycle: Marine Chemistry, v. 30: 1-29. Andres, R.J., and Kasgnoc, A.D., Global Emissions Inventory Activity, 1997, Global Emissions Inventory Activity: Time-Averaged Inventory of Volcanic Sulfur Emissions.

Barnes, Ivan, Irwin, W.P., and White, D.E., 1978, Global distribution of carbon dioxide discrages, and major zones of seismicity: U.S. Geological Survey Water Resources Investigation 78-79, Open-File Report, 12 p. Bates, T.S., Lamb, B.K., Guenther, A., Dignon, J., Stoiber, R.E., 1992, Sulfur emissions to the atmosphere from natural sources. Journal of Atmospheric Chemistry 14:315-337. Buat-Menard, P., and Arnold, M., 1978, The heavy metal chemistry of atmospheric particulate matter emitted by Mount Etna volcano: Geophysical Research Letters, v. 5, p. 245. Cadle, R.D., 1980, A comparison of volcanic with other fluxes of atmospheric trace gas constituents: Reviews of Geophysics and Space Physics, v. 18, p. 746-752. Tamar Elias, written communication, , 28 May 1997.

Gerlach, T.M., 1991, Present-day CO2 emissions from volcanoes: Transactions of the American Geophysical Union (EOS), v. 72, p. 249, and 254-255. Gerlach, T.M., 1991, Etna's Greenhouse Pump: Nature, 351, p. 352-353. Gerlach, T.M., 1990, Natural Sources of Greenhouse gases: CO2 emissions from volcanoes. Geothermal Resources Council Transactions, vol. 14, part I, pp. 639-641, Deadly Gases At certain concentrations some volcanic gases can be fatal. In historic time, deaths have been caused by sulfur dioxide, carbon dioxide, and carbonic and hydrogen sulfide. The following information is compiled from Volcanoes of the World by Simkin and Siebert (1994), and the Bulletin of the Global Volcanism Program. Right: Photo of dead buffalo at Lake Nyos, Cameroon. Jack Lockwood, U.S. Geological Survey. Vesuvius, Italy at Vesuvius killed about 400 people.

Several people died from carbon dioxide. In 1872, an unknown number of fatalities were caused by carbon dioxide. Seven people died of gas inhalation in 1873. Etna, Italy The 1650 eruption of Etna caused about 40 deaths; some caused by opthalmias from sulfurous vapors and suffocation. The crew of a ship suffocated as it passed the volcano. Oku Volcanic Field, Africa In August, 1984, 37 people were killed when carbon dioxide was released from Lake Monoun. In August, 1986, 1,700 people were killed when a large amount of carbon dioxide was released from Lake Nyos. At least 300 people were hospitalized. Karthala, Indian Ocean with at least 16 historic eruptions. In June of 1923, three boys were killed by asphyxiating gas. Carbonic acid and hydrogen sulfide were involved. The volcano was not erupting. Papandayan, Java, Indonesia Papandayan is a stratovolcano with three historic eruptions.

In December of 1924, a volcanological observer died, probably by suffocation due to hydrogen sulfide. Dieng Plateau, Java, Indonesia The Dieng Plateau, a complex volcano, has had at least 16 historic eruptions. In February of 1979, at least 149 people died from poisonous gas(es) (either crbon dioxide or carbon dioxide and hydrogen sulfide) as they fled eruptions at Sinila and Sigludung Craters. Hakone, Honshu, Japan Hakone, a complex volcano, has not erupted in 1,000 years. In May of 1933, one person was killed in association with fumarolic activity. Aso, Japan In December, 1997, two men died when sulfur dioxide concentrations reached ~5 to ~8 ppm. Since 1980, 71 people have been hospitalized due to inhalation of volcanic gases at Aso. Seven of these people died.

Tseax River Cone, British Columbia, Canada The Tseax River Cone, a in 1907, Carran maar in 1955, and Mirador in 1979. Two people were killed by gases during the 1955 eruption. Vestmannaeyjar (Heimaey), Iceland During the 1973 eruption near Vestmannaeyjar a sleeping man was killed by carbon dioxide as it pooled in the of his house. La Palma, Canary Islands La Palma is a stratovolcano with seven historic eruptions. Two eruptions caused fatalities. In 1677, one man and many animals were killed by gas. Volcanic gases in Hawaii are not fatal but vog (volcanic smog) may degrade lung function and compromise peoples immune systems, especially in children, individuals with chronic asthma or other respiratory impairments, or people with circulatory problems. Source of Information: Simkin, T., and Siebert, L., 1994, Volcanoes of the World: Geoscience Press, Tucson, Arizona, 349 p. Case Studies eruptions.

The Toba eruption may have caused about 3 to 4 degree C cooling at the surface but this impact is hard to detect because of concurrent glacial conditions (Sigurdsson, 1990). For More Information Relevant peer reviewed journal references include: Alverez, W. and Asaro, F., 1990, An extraterrestrial impact: Scientific America, v. 256, p. 44-60. American Geophysical Union, 1992, Volcanism and Climate Change, AGU Special Report: Washington DC, American Geophysical Union. Buat-Menard, P., and Arnold, M., 1978, The heavy metal chemistry of atmospheric particulate matter emitted by Mount Etna volcano : Geophysical Research Letters, v. 5, p. 245. Bluth, G.J.S., Rose, W.I., Sprod, I.E., and Krueger, A.J., 1997, Stratospheric loading from explosive volcanic eruptions: Jour. Geology, v. 105, p. 671-683.

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409. Zreda-Gostynska, G., Kyle, P.R., Finnegan, D. 1993. Chlorine, fluorine, and sulfur emissions from Mount Erebus, Antarctica and estimated contributions to the Antarctic atmosphere: Geophysical Research Letters, v. 20, p. 1959-1962. USGS: Volcano Hazards Program Volcano Hazards Program View Movie Your browser does not support HTML 5 video. Magma contains dissolved gases, which provide the driving force that causes most volcanic eruptions. As magma rises towards the surface and pressure decreases, gases are released from the liquid portion of the magma (melt) and continue to travel upward and are eventually released into the atmosphere. Large eruptions can release enormous amounts of gas in a short time. The 1991 eruption of Mt. Pinatubo is thought to have injected more than 250 megatons of gas into the upper atmosphere on a single day. However, even if magma never reaches the surface, gases can often escape continuously into the atmosphere from the soil, volcanic vents , fumaroles , and hydrothermal systems.

By far the most abundant volcanic gas is water vapor, which is harmless. However, significant amounts of carbon dioxide, sulfur dioxide, hydrogen sulfide and hydrogen halides can also be emitted from volcanoes. Depending on their concentrations, these gases are all potentially hazardous to people, animals, agriculture, and property. Carbon dioxide (CO2) trapped in low-lying areas can be lethal to people and animals. Carbon dioxide constitutes approximately 0.04% of the air in the Earth's atmosphere. In an average year, volcanoes release between about 180 and 440 million tonnes of carbon dioxide. When this colorless, odorless gas is emitted from volcanoes, it typically becomes diluted to low concentrations very quickly and is not life threatening. However, because cold carbon dioxide gas is heavier than air it can flow into in low-lying areas where it can reach much higher concentrations in certain, very stable atmospheric conditions. This can pose serious risks to people and animals. Breathing air with more than 3% CO2 can quickly lead to headaches, dizziness, increased heart rate and difficulty breathing. At mixing ratios exceeding about 15%, carbon dioxide quickly causes unconsciousness and death.

In volcanic or other areas where CO2 emissions occur, it is important to avoid small depressions and low areas that might be CO2 traps. The boundary between healthy air and lethal gas can be extremely sharp; even a single step upslope may be adequate to escape death. In 2006, three ski patrol members were killed at Mammoth Mountain ski resort after falling into a snow depression surrounding a volcanic fumarole and filled with cool CO2 gas. High concentrations of CO2 gas in soils can also damage or destroy vegetation, as is visible in several areas on Mammoth Mountain . In addition to their direct hazard, volcanic CO2 emissions also have the capacity to affect the global climate , but scientific studies indicate that the average global volcanic output is insignificant when compared to emissions from human activity. Sulfur dioxide (SO2) is irritating to eyes, skin and respiratory system. Sulfur dioxide is a colorless gas with a pungent odor that irritates skin and the tissues and mucous membranes of the eyes, nose, and throat.

SO2 emissions can cause acid rain and air pollution downwind of a volcano—at Kīlauea volcano in Hawaii, high concentrations of sulfur dioxide produce volcanic smog (VOG) causing persistent health problems for downwind populations. During very large eruptions, SO2 can be injected to altitudes of greater than 10km into the stratosphere. Here, SO2 is converted to sulfate aerosols which reflect sunlight and therefore have a cooling effect on the Earth's climate. They also have a role in ozone depletion, as many of the reactions that destroy ozone occur on the surface of such aerosols. Please see our discussion of volcanic gases and climate change for additional information. Hydrogen sulfide (H2S) is very toxic in high concentrations. Hydrogen sulfide is a colorless, flammable gas with a strong, offensive odor. It is sometimes referred to as sewer gas. Interestingly, the human nose is more sensitive to H2S than any gas monitoring instrument we have today: air mixtures with as little as 0.000001% H2S are associated with a rotten egg smell.

Unfortunately, however, our sense of smell is not a reliable alarm - at mixing ratios above about 0.01%, H2S becomes odorless and very toxic, causing irritation of the upper respiratory tract and, during long exposure, pulmonary edema. Exposure to 500 ppm can cause a human to fall unconscious in 5 minutes and die in an hour or less. Hydrogen halides (HF, HCl, HBr) are strong, toxic acids. When magma ascends close to the surface, volcanoes can emit the halogens fluorine, chlorine and bromine in the form of hydrogen halides (HF, HCl and HBr). These species are all strong acids and have high solubility; therefore they rapidly dissolve in water droplets within volcanic plumes or the atmosphere where they can potentially cause acid rain. In an ash -producing eruption, ash particles are also often coated with hydrogen halides. Once deposited, these coated ash particles can poison drinking water supplies, agricultural crops, and grazing land.

Question: What name is given to a vent on a volcano that emits smoke and gas?
Answer: Fumarole