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 (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2). 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 at our website for Volcanic Gas.

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Image: Monitoring Gas Emissions from Kilauea Volcano
November 10, 2010

Monitoring Gas Emissions from Kilauea Volcano

Sulfur dioxide gas emissions from the crater of Pu‘u ‘Ō ‘ō on Kīlauea’s east rift zone and the vent within Halema‘uma‘u Crater at Kīlauea’s summit create volcanic pollution that affects the air quality of downwind communities.  Here, a USGS Hawaiian Volcano Observatory gas geochemist measures Pu‘u ‘Ō‘ō gas emissions using an instrument that detects gas compositions on the

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Image: Deploying a FTIR on Pu’u ‘Ō’ō crater
June 3, 2010

Deploying a FTIR on Pu’u ‘Ō’ō crater

HVO gas geochemists deployed a FTIR spectrometer on the east rim of Pu`u `Ō `ō crater. The FTIR measures the composition of the East Wall vent gases by "looking" through the plume at an infrared lamp (obscured by fume in this photo)

Attribution:
Image: Deploying a FTIR on Pu’u ‘Ō’ō crater
June 3, 2010

Deploying a FTIR on Pu’u ‘Ō’ō crater

This photo was taken from the lamp on the other side of the plume. The FTIR is the small dark silhouette on the rim across the crater gap.

Attribution:
video thumbnail: Halema'uma'u Gas Plume Variations (November 17, 2008)
November 16, 2008

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. While ashy plumes released by collapses and explosive events are

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Attribution:
A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06.
January 24, 2006

A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06.

A gas plume arising from Augustine Volcano during it's eruptive phase 2005-06. This photo was taken during  a FLIR/maintenance flight on January 24, 2006.

Image: Measuring a Superheated Fumarole
September 30, 1998

Measuring a Superheated Fumarole

USGS geochemist Bill Evans measures the temperature of a superheated (hotter than the boiling point) fumarole in Lassen Volcanic National Park.

Image: Finding the Fumarole Vent
August 11, 1992

Finding the Fumarole Vent

USGS hydrologist Michael Sorey tries to locate the steam vent at a fumarole in the Bumpass Hell area in Lassen Volcanic National Park.

Image: Sampling a Fumarole
July 31, 1990

Sampling a Fumarole

USGS geochemist Cathy Janik (left) and Iceland Geosurvey chemist Jón Örn Bjarnason (right) collect a gas sample from a fumarole in Lassen Volcanic National Park.

Image shows two scientists on the slopes of Mount St. Helens with steam rising around them
September 24, 1981

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.

Image:  ARRA-funded Student Sampling Gas at Augustine Volcano

ARRA-funded Student Sampling Gas at Augustine Volcano

ARRA-funded student Taryn Lopez (Univ. Alaska-Fairbanks) sampling gas emissions at fumarole next to dome at the summit of Augustine volcano.

Attribution: Natural Hazards
Image: Taryn Lopez Measuring Temperature of Gas Emissions

Taryn Lopez Measuring Temperature of Gas Emissions

Taryn Lopez measuring the temperature of gas emissions near summit of Augustine Volcano.

Image: Halema'uma'u Vent Gas Plume

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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