What is "vog"? How is it related to 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.

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Related Content

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Date published: May 18, 2017

EarthWord–Vog

Just like smog and fog, this EarthWord is not what you want to see while driving...

Date published: August 18, 2016

Living with Vog on an Active Volcano: New Resources

New informational products about the health hazards of volcanic air pollution known as “vog,” are available through a new interagency partnership.

Date published: February 11, 2015

New Study Looks at How People Cope with Vog

A new study to examine how people who live downwind of Kīlauea Volcano cope with volcanic gas emissions, or vog, is currently underway.

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White gas plume rising straight up from Kilauea Volcano summit with distant, bright, full moon.
August 16, 2016

With stagnant winds present, the plume from Halema`uma`u Crater at the summit of Kilauea Volcano, stands straight up, showing off the distant, but bright, full moon.

scientist with camera and spectrometer at the edge of smoking volcanic crater.
August 16, 2016

USGS Hawaiian Volcano Observatory geochemist measuring gases released from Kïlauea with a Fourier transform infrared (FTIR) spectrometer, an instrument that detects gas compositions on the basis of absorbed infrared light. The data obtained from FTIR measurements have been useful in identifying the many components of volcanic-gas emissions, which provide information on the quantity of magma circulating within an eruptive vent. The FTIR spectrometer is aimed at spattering area on summit lava lake surface to measure volcanic-gas composition.

Image: Monitoring Volcanic Gases on Kilauea's East Rift Zone
May 31, 2014

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. Instrumentation at this site measures ambient concentration of noxious sulfur dioxide gas released from the volcano's vents, along with meteorological parameters, transmitting these data back to HVO in real time for display and analysis.

Image: Monitoring Volcanic Gases on Kilauea's East Rift Zone II
May 31, 2014

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. Instrumentation at this site measures ambient concentration of noxious sulfur dioxide gas released from the volcano's vents, along with meteorological parameters, transmitting these data back to HVO in real time for display and analysis.

video thumbnail: Volcano Hazards
July 30, 2012

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:

  • Volcanoes: Monitoring Volcanoes
  • Volcanoes: National Volcano Early Warning System
  • Volcanoes: Science for Public Safety
May 9, 2012

USGS geologist, Angie Diefenbach, describes how she uses GIS, (Geographic Information Systems) software to study volcanic eruptions and their impacts on society.

USGS
June 30, 2011

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? Come join us to explore these questions at this family friendly presentation with hands-on experiments.

Speakers: Janet Hannon and Stan Mroczkowski

Image: Gas-Rich Lava Flow
December 2, 2010

A gas-rich lava flow on the northwest margin of the new shield.

Image: New Gas Vent of Pu’u ‘Ō’ō
June 21, 2010

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.

video thumbnail: Halema'uma'u Gas Vent Huffs and Puffs
August 9, 2009

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. This period of reduced activity persisted for over a month, until August 9, when a new hot gas vent poked through the rubble on the floor of the eruptive cavity in Halema'uma'u. Following this reawakening, the Halema'uma'u vent began emitting a faint nighttime glow for the first time since July 4, 2009.

This thermal video clip, taken from the rim of Halema'uma'u Crater, shows vigorous puffing from the new gas vent, which also produces audible gas-rushing sounds. A thermal camera is used because it can 'see' through the thick fume that typically obscures the eruptive cavity.

For safety reasons, Hawai'i Volcanoes National Park has closed access to the summit vent, which has erupted explosively numerous times since it opened in March 2008. However, the public can see spectacular views the vent—especially the faint orange glow it emits after dark—from an overlook at Jaggar Museum or via HVO Webcams (http://hvo.wr.usgs.gov/cams/).

Video was taken by Matt Patrick, USGS Hawaiian Volcano Observatory geologist, on August 10, 2009, around 4:30 p.m.

video thumbnail: Halema'uma'u Gas Plume Variations (November 17, 2008)
November 16, 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. While ashy plumes released by collapses and explosive events are exciting, even the behavior of the ""typical"" gas plume is interesting and occassionally undergoes rapid changes in plume vigor. This video, from November 17, 2008, shows a day in the life of the gas plume rising from the informally-named Overlook vent. On this day, the plume was especially dynamic with the plume becoming very small several times throughout the day.

The images that comprise this video were acquired by a webcam in the observation tower of the Hawaiian Volcano Observatory about 1.8 kilometers (1.1 miles) north of the vent. The image acquisition rate was roughly 1 frame per minute and the resulting video is played at 15 frames per second.