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 vog
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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.
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.)
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. The lava then drains
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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.
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.
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. The far (north) side of the vent
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