Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
What is "vog"? How is it related to sulfur dioxide (SO2) emissions?
Vog (volcanic smog) is a visible haze comprised of gas and an aerosol of tiny particles and acidic droplets created when sulfur dioxide (SO2) and other gases emitted from a volcano chemically interact with sunlight and atmospheric oxygen, moisture, and dust. Volcanic gas emissions can pose environmental and health risks to nearby communities.
Vog is a hazard that's associated with Hawaiian volcanoes in particular. See the Hawaii Interagency Vog Information Dashboard for detailed information and current conditions.
Learn more:
- Volcanic gases can be harmful to health, vegetation, and infrastructure
- Volcanic gas hazards from Kilauea Volcano
- USGS Hawaiian Volcano Observatory FAQs about volcanic smog (vog)
Related Content
What gases are emitted by Kīlauea and other active volcanoes?
Ninety-nine percent of the gas molecules emitted during a volcanic eruption are water vapor (H 2 O), carbon dioxide (CO 2 ), and sulfur dioxide (SO 2 ). The remaining one percent is comprised of small amounts of hydrogen sulfide, carbon monoxide, hydrogen chloride, hydrogen fluoride, and other minor gas species. Learn more: Volcanic gases can be harmful to health, vegetation and infrastructure
Who monitors volcanic gases emitted by Kīlauea and how is it done?
The U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) determines the amount and composition of gases emitted by Kīlauea Volcano. Changes in gas emissions can reveal important clues about the inner workings of a volcano, so they are measured on a regular basis. HVO scientists use both remote and direct sampling techniques to measure compositions and emission rates of gas from Kīlauea...
Does vog (volcanic smog) impact plants and animals?
The sulfuric acid droplets in vog have the corrosive properties of dilute battery acid. When vog mixes directly with moisture on the leaves of plants it can cause severe chemical burns, which can damage or kill the plants. Sulfur dioxide (SO 2 ) gas can also diffuse through leaves and dissolve to form acidic conditions within plant tissue. Farmers on Hawai`i Island, particularly in the Ka`u...
How much sulfur dioxide (SO2) gas does Kīlauea emit?
Kīlauea typically emits between 500 and 14,000 metric tons of sulfur dioxide gas (SO 2 ) per day during periods of sustained eruption. During the 2018 eruption at Kīlauea’s Lower East Rift Zone, SO 2 emissions were over 100,000 metric tons per day, in keeping with the increased vigor of that eruption. Methods for calculating emission rates for SO 2 can be complicated and challenging in the high...
Where and how do sulfur dioxide and volcanic gases (vog) affect air quality in Hawaii?
The most critical factors that determine how much vog impacts an area are wind direction and speed. Air temperature, humidity, rainfall, location of the source, and the amount of sulfur dioxide (SO2) being emitted are also factors. During prevailing trade (from northeast) wind conditions, any SO2 emitted from Pu`u `Ō`ō is blown out to sea, while any SO2 from the summit vent often creates vog in Ka...
Should I cancel my plans to visit Hawai`i Island because of sulfur dioxide (SO2) and vog?
Predicting the vog levels that visitors might experience during a short stay in Hawai`i is as difficult as predicting the weather. Once volcanic emissions are in the atmosphere, they are distributed by prevailing winds. Where and how bad the vog is ultimately depends on several factors including wind direction, wind speed, air temperature, humidity, and rainfall, as well as the location of the...
What health hazards are posed by vog (volcanic smog)?
Vog poses a health hazard by aggravating preexisting respiratory ailments. Sulfur dioxide (SO 2 ) gas can irritate skin and the tissues and mucous membranes of the eyes, nose, and throat, and can penetrate airways, producing respiratory distress in some individuals. Aerosol particles in vog can also penetrate deep into human lungs and, at elevated levels, can induce symptoms of asthma. Physical...
Does ash ever erupt from Kīlauea Volcano?
Kīlauea Volcano is renowned for its relatively benign eruptions of fluid lava flows. Therefore, many people were surprised by the small explosions that occurred in Halema`uma`u Crater in 2008 and 2018, and even more surprised to learn that volcanic ash was being erupted from a new gas vent. However, ash emissions from Halema`uma`u Crater are part of the volcano's legacy. Kīlauea's summit has...
How hot is a Hawaiian volcano?
Very hot!! Here are some temperatures recorded at different times and locations: The eruption temperature of Kīlauea lava is about 1,170 degrees Celsius (2,140 degrees Fahrenheit). The temperature of the lava in the tubes is about 1,250 degrees Celsius (2,200 degrees Fahrenheit). The tube system of episode 53 (Pu'u O'o eruption) carried lava for 10 kilometers (6 miles) from the vent to the sea...
Is it dangerous to work on volcanoes? What precautions do scientists take?
Volcanoes are inherently beautiful places where forces of nature combine to produce awesome events and spectacular landscapes. For volcanologists, they're FUN to work on! Safety is, however, always the primary concern because volcanoes can be dangerous places. USGS scientists try hard to understand the risk inherent in any situation, then train and equip themselves with the tools and support...
Why is it important to monitor volcanoes?
There are 161 potentially active volcanoes in the United States. According to a 2018 USGS assessment , 57 volcanoes are a high threat or very high threat to public safety. Many of these volcanoes have erupted in the recent past and will erupt again in the foreseeable future. As populations increase, areas near volcanoes are being developed and aviation routes are increasing. As a result, more...
Monitoring Volcanic Gases on Kilauea's East Rift Zone
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Monitoring Volcanic Gases on Kilauea's East Rift Zone II
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Volcano Hazards
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
The Air We Breathe…It’s a Gas!
We live at the bottom of an ocean of air. Most adults take around 29,000 breaths a day, children breathe a little faster; but what is in this air we breathe? What are the gases in the air? How much of each gas is there? Do these gases have different weights? How cold are liquid nitrogen and dry ice, and where did those names come from?
We live at the bottom of an ocean of air. Most adults take around 29,000 breaths a day, children breathe a little faster; but what is in this air we breathe? What are the gases in the air? How much of each gas is there? Do these gases have different weights? How cold are liquid nitrogen and dry ice, and where did those names come from?
Gas-Rich Lava Flow
A gas-rich lava flow on the northwest margin of the new shield.
A gas-rich lava flow on the northwest margin of the new shield.
New Gas Vent of Pu’u ‘Ō’ō
The new gas vent on the east wall of Pu`u `Ō `ō crater opening up next to an older vent (the dark opening to the right of the new gas vent) that sealed shut in the past few months. The new vent has been incandescent at night for the past few days.
The new gas vent on the east wall of Pu`u `Ō `ō crater opening up next to an older vent (the dark opening to the right of the new gas vent) that sealed shut in the past few months. The new vent has been incandescent at night for the past few days.
Halema'uma'u Gas Vent Huffs and Puffs
The ongoing eruption in Halema'uma'u Crater at the summit of Kilauea Volcano has experienced several significant interruptions in activity since it began in March 2008. The latest disruption began on June 30, 2009, when a large collapse of the vent rim dumped rubble onto the lava surface and dramatically reduced gas emissions.
The ongoing eruption in Halema'uma'u Crater at the summit of Kilauea Volcano has experienced several significant interruptions in activity since it began in March 2008. The latest disruption began on June 30, 2009, when a large collapse of the vent rim dumped rubble onto the lava surface and dramatically reduced gas emissions.
Halema'uma'u Gas Plume Variations (November 17, 2008)
The erupting vent within Halema'uma'u Crater at Kilauea's summit (see http://hvo.wr.usgs.gov/kilauea/timeline/ for links describing eruptive activity at the summit of Kilauea Volcano) typically produces a white to gray gas plume dominated by steam.
The erupting vent within Halema'uma'u Crater at Kilauea's summit (see http://hvo.wr.usgs.gov/kilauea/timeline/ for links describing eruptive activity at the summit of Kilauea Volcano) typically produces a white to gray gas plume dominated by steam.
USGS Hawaiian Volcano Observatory Monitors Kilauea's Summit Eruption
The USGS Hawaiian Volcano Observatory (foreground) is located on the caldera rim of Kilauea Volcano, Hawai'i—the most active volcano in the world. The observatory's location provides an excellent view of summit eruptive activity, which began in 2008.
The USGS Hawaiian Volcano Observatory (foreground) is located on the caldera rim of Kilauea Volcano, Hawai'i—the most active volcano in the world. The observatory's location provides an excellent view of summit eruptive activity, which began in 2008.
Ash-rich plume rises out of Halemaʻumaʻu Crater, Kilauea Volcano Hawaiʻi
Ash-rich plume rises out of Halemaʻumaʻu Crater, Kilauea Volcano Hawaiʻi.
Ash-rich plume rises out of Halemaʻumaʻu Crater, Kilauea Volcano Hawaiʻi.
Vog from Kilauea
The rim of Kīlauea Volcano’s summit caldera, normally clear on trade-wind days (left), became nearly obscured by vog (right) on some non-trade wind days beginning in 2008, when sulfur dioxide emissions from the volcano’s summit increased to unusually high levels. (This photo has been edited.)
The rim of Kīlauea Volcano’s summit caldera, normally clear on trade-wind days (left), became nearly obscured by vog (right) on some non-trade wind days beginning in 2008, when sulfur dioxide emissions from the volcano’s summit increased to unusually high levels. (This photo has been edited.)
Gas-Pistoning at Drainhole Vent in Pu'u 'O'o Crater (June 28, 2006)
Gas-pistoning is an interesting phenomenon seen at Kilauea and other volcanoes. It is caused by the accumulation of gas within, or the rise of a gas slug through, a column of lava. In either case, the gas pushes up the overlying lava (the "piston"). Eventually, the gas breaches the surface and escapes, sometimes as a forceful jet of fume and spatter.
Gas-pistoning is an interesting phenomenon seen at Kilauea and other volcanoes. It is caused by the accumulation of gas within, or the rise of a gas slug through, a column of lava. In either case, the gas pushes up the overlying lava (the "piston"). Eventually, the gas breaches the surface and escapes, sometimes as a forceful jet of fume and spatter.
Gas Sampling around the Mount St. Helens Dome
USGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.
USGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.
Halema'uma'u Vent Gas Plume
Over the past several days, the lava surface within the vent in Halema'uma'u has occasionally, and temporarily, reached to within about 115 m (375 ft) below the floor of Halema'uma'u Crater, as seen in this photo. During these high-lava stands, the gas plume is generally fairly wispy, providing the rare naked-eye view of the lava surface.
Over the past several days, the lava surface within the vent in Halema'uma'u has occasionally, and temporarily, reached to within about 115 m (375 ft) below the floor of Halema'uma'u Crater, as seen in this photo. During these high-lava stands, the gas plume is generally fairly wispy, providing the rare naked-eye view of the lava surface.
Related Content
- FAQ
What gases are emitted by Kīlauea and other active volcanoes?
Ninety-nine percent of the gas molecules emitted during a volcanic eruption are water vapor (H 2 O), carbon dioxide (CO 2 ), and sulfur dioxide (SO 2 ). The remaining one percent is comprised of small amounts of hydrogen sulfide, carbon monoxide, hydrogen chloride, hydrogen fluoride, and other minor gas species. Learn more: Volcanic gases can be harmful to health, vegetation and infrastructure
Who monitors volcanic gases emitted by Kīlauea and how is it done?
The U.S. Geological Survey's Hawaiian Volcano Observatory (HVO) determines the amount and composition of gases emitted by Kīlauea Volcano. Changes in gas emissions can reveal important clues about the inner workings of a volcano, so they are measured on a regular basis. HVO scientists use both remote and direct sampling techniques to measure compositions and emission rates of gas from Kīlauea...
Does vog (volcanic smog) impact plants and animals?
The sulfuric acid droplets in vog have the corrosive properties of dilute battery acid. When vog mixes directly with moisture on the leaves of plants it can cause severe chemical burns, which can damage or kill the plants. Sulfur dioxide (SO 2 ) gas can also diffuse through leaves and dissolve to form acidic conditions within plant tissue. Farmers on Hawai`i Island, particularly in the Ka`u...
How much sulfur dioxide (SO2) gas does Kīlauea emit?
Kīlauea typically emits between 500 and 14,000 metric tons of sulfur dioxide gas (SO 2 ) per day during periods of sustained eruption. During the 2018 eruption at Kīlauea’s Lower East Rift Zone, SO 2 emissions were over 100,000 metric tons per day, in keeping with the increased vigor of that eruption. Methods for calculating emission rates for SO 2 can be complicated and challenging in the high...
Where and how do sulfur dioxide and volcanic gases (vog) affect air quality in Hawaii?
The most critical factors that determine how much vog impacts an area are wind direction and speed. Air temperature, humidity, rainfall, location of the source, and the amount of sulfur dioxide (SO2) being emitted are also factors. During prevailing trade (from northeast) wind conditions, any SO2 emitted from Pu`u `Ō`ō is blown out to sea, while any SO2 from the summit vent often creates vog in Ka...
Should I cancel my plans to visit Hawai`i Island because of sulfur dioxide (SO2) and vog?
Predicting the vog levels that visitors might experience during a short stay in Hawai`i is as difficult as predicting the weather. Once volcanic emissions are in the atmosphere, they are distributed by prevailing winds. Where and how bad the vog is ultimately depends on several factors including wind direction, wind speed, air temperature, humidity, and rainfall, as well as the location of the...
What health hazards are posed by vog (volcanic smog)?
Vog poses a health hazard by aggravating preexisting respiratory ailments. Sulfur dioxide (SO 2 ) gas can irritate skin and the tissues and mucous membranes of the eyes, nose, and throat, and can penetrate airways, producing respiratory distress in some individuals. Aerosol particles in vog can also penetrate deep into human lungs and, at elevated levels, can induce symptoms of asthma. Physical...
Does ash ever erupt from Kīlauea Volcano?
Kīlauea Volcano is renowned for its relatively benign eruptions of fluid lava flows. Therefore, many people were surprised by the small explosions that occurred in Halema`uma`u Crater in 2008 and 2018, and even more surprised to learn that volcanic ash was being erupted from a new gas vent. However, ash emissions from Halema`uma`u Crater are part of the volcano's legacy. Kīlauea's summit has...
How hot is a Hawaiian volcano?
Very hot!! Here are some temperatures recorded at different times and locations: The eruption temperature of Kīlauea lava is about 1,170 degrees Celsius (2,140 degrees Fahrenheit). The temperature of the lava in the tubes is about 1,250 degrees Celsius (2,200 degrees Fahrenheit). The tube system of episode 53 (Pu'u O'o eruption) carried lava for 10 kilometers (6 miles) from the vent to the sea...
Is it dangerous to work on volcanoes? What precautions do scientists take?
Volcanoes are inherently beautiful places where forces of nature combine to produce awesome events and spectacular landscapes. For volcanologists, they're FUN to work on! Safety is, however, always the primary concern because volcanoes can be dangerous places. USGS scientists try hard to understand the risk inherent in any situation, then train and equip themselves with the tools and support...
Why is it important to monitor volcanoes?
There are 161 potentially active volcanoes in the United States. According to a 2018 USGS assessment , 57 volcanoes are a high threat or very high threat to public safety. Many of these volcanoes have erupted in the recent past and will erupt again in the foreseeable future. As populations increase, areas near volcanoes are being developed and aviation routes are increasing. As a result, more...
- Multimedia
Monitoring Volcanic Gases on Kilauea's East Rift Zone
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Monitoring Volcanic Gases on Kilauea's East Rift Zone IIHawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Hawaiian Volcano Observatory Geochemist Jeff Sutton and CSAV international volcanology students visit a continuous gas monitoring site on Kilauea's east rift zone during field studies portion of the summer training course.
Volcano HazardsThe United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
The United States has 169 active volcanoes. More than half of them could erupt explosively, sending ash up to 20,000 or 30,000 feet where commercial air traffic flies. USGS scientists are working to improve our understanding of volcano hazards to help protect communities and reduce the risks.
Video Sections:
The Air We Breathe…It’s a Gas!We live at the bottom of an ocean of air. Most adults take around 29,000 breaths a day, children breathe a little faster; but what is in this air we breathe? What are the gases in the air? How much of each gas is there? Do these gases have different weights? How cold are liquid nitrogen and dry ice, and where did those names come from?
We live at the bottom of an ocean of air. Most adults take around 29,000 breaths a day, children breathe a little faster; but what is in this air we breathe? What are the gases in the air? How much of each gas is there? Do these gases have different weights? How cold are liquid nitrogen and dry ice, and where did those names come from?
Gas-Rich Lava FlowA gas-rich lava flow on the northwest margin of the new shield.
A gas-rich lava flow on the northwest margin of the new shield.
New Gas Vent of Pu’u ‘Ō’ōThe new gas vent on the east wall of Pu`u `Ō `ō crater opening up next to an older vent (the dark opening to the right of the new gas vent) that sealed shut in the past few months. The new vent has been incandescent at night for the past few days.
The new gas vent on the east wall of Pu`u `Ō `ō crater opening up next to an older vent (the dark opening to the right of the new gas vent) that sealed shut in the past few months. The new vent has been incandescent at night for the past few days.
Halema'uma'u Gas Vent Huffs and PuffsThe ongoing eruption in Halema'uma'u Crater at the summit of Kilauea Volcano has experienced several significant interruptions in activity since it began in March 2008. The latest disruption began on June 30, 2009, when a large collapse of the vent rim dumped rubble onto the lava surface and dramatically reduced gas emissions.
The ongoing eruption in Halema'uma'u Crater at the summit of Kilauea Volcano has experienced several significant interruptions in activity since it began in March 2008. The latest disruption began on June 30, 2009, when a large collapse of the vent rim dumped rubble onto the lava surface and dramatically reduced gas emissions.
Halema'uma'u Gas Plume Variations (November 17, 2008)The erupting vent within Halema'uma'u Crater at Kilauea's summit (see http://hvo.wr.usgs.gov/kilauea/timeline/ for links describing eruptive activity at the summit of Kilauea Volcano) typically produces a white to gray gas plume dominated by steam.
The erupting vent within Halema'uma'u Crater at Kilauea's summit (see http://hvo.wr.usgs.gov/kilauea/timeline/ for links describing eruptive activity at the summit of Kilauea Volcano) typically produces a white to gray gas plume dominated by steam.
USGS Hawaiian Volcano Observatory Monitors Kilauea's Summit EruptionThe USGS Hawaiian Volcano Observatory (foreground) is located on the caldera rim of Kilauea Volcano, Hawai'i—the most active volcano in the world. The observatory's location provides an excellent view of summit eruptive activity, which began in 2008.
The USGS Hawaiian Volcano Observatory (foreground) is located on the caldera rim of Kilauea Volcano, Hawai'i—the most active volcano in the world. The observatory's location provides an excellent view of summit eruptive activity, which began in 2008.
Ash-rich plume rises out of Halemaʻumaʻu Crater, Kilauea Volcano HawaiʻiAsh-rich plume rises out of Halemaʻumaʻu Crater, Kilauea Volcano Hawaiʻi.
Ash-rich plume rises out of Halemaʻumaʻu Crater, Kilauea Volcano Hawaiʻi.
Vog from KilaueaThe rim of Kīlauea Volcano’s summit caldera, normally clear on trade-wind days (left), became nearly obscured by vog (right) on some non-trade wind days beginning in 2008, when sulfur dioxide emissions from the volcano’s summit increased to unusually high levels. (This photo has been edited.)
The rim of Kīlauea Volcano’s summit caldera, normally clear on trade-wind days (left), became nearly obscured by vog (right) on some non-trade wind days beginning in 2008, when sulfur dioxide emissions from the volcano’s summit increased to unusually high levels. (This photo has been edited.)
Gas-Pistoning at Drainhole Vent in Pu'u 'O'o Crater (June 28, 2006)Gas-pistoning is an interesting phenomenon seen at Kilauea and other volcanoes. It is caused by the accumulation of gas within, or the rise of a gas slug through, a column of lava. In either case, the gas pushes up the overlying lava (the "piston"). Eventually, the gas breaches the surface and escapes, sometimes as a forceful jet of fume and spatter.
Gas-pistoning is an interesting phenomenon seen at Kilauea and other volcanoes. It is caused by the accumulation of gas within, or the rise of a gas slug through, a column of lava. In either case, the gas pushes up the overlying lava (the "piston"). Eventually, the gas breaches the surface and escapes, sometimes as a forceful jet of fume and spatter.
Gas Sampling around the Mount St. Helens DomeUSGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.
USGS geologists gathered samples by hand from vents on the dome and crater floor. Additionally, sulfur dioxide gas was measured from a specially equipped airplane before, during, and after eruptions to determine "emission rates" for the volcano.
Halema'uma'u Vent Gas PlumeOver the past several days, the lava surface within the vent in Halema'uma'u has occasionally, and temporarily, reached to within about 115 m (375 ft) below the floor of Halema'uma'u Crater, as seen in this photo. During these high-lava stands, the gas plume is generally fairly wispy, providing the rare naked-eye view of the lava surface.
Over the past several days, the lava surface within the vent in Halema'uma'u has occasionally, and temporarily, reached to within about 115 m (375 ft) below the floor of Halema'uma'u Crater, as seen in this photo. During these high-lava stands, the gas plume is generally fairly wispy, providing the rare naked-eye view of the lava surface.
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