Skip to main content
U.S. flag

An official website of the United States government

December 19, 2022

Changes in gas emissions can forewarn of volcanic or hydrothermal activity.  Continuous monitoring of gas concentrations by a station deployed in the Mud Volcano thermal area in 2021 was complemented this year by the installation of a new instrument that measures the rates of release of gas and hydrothermal heat.

Yellowstone Caldera Chronicles is a weekly column written by scientists and collaborators of the Yellowstone Volcano Observatory. This week's contribution is from Jennifer Lewicki, research geologist with the U.S. Geological Survey in Menlo Park, CA.

Interior of SNIF multi-GAS enclosure on Mount St. Helens, Washington
Interior of the SNIF multi-GAS enclosure on Mount St. Helens, Washington

Changes in earthquake activity, ground movement, and gas emissions can signal a volcano’s reawakening. Although many volcanoes around the world have been instrumented over the past decades with sensors that allow scientists to continuously observe earthquakes and ground movement in real time, gas monitoring technologies have only recently begun to catch up with their geophysical counterparts.  Traditionally, volcanic gas monitoring has relied on scientists going to the field and collecting samples within areas that may be potentially hazardous, followed by detailed chemical analysis in the laboratory.  However, recent technological advances now allow scientists to deploy field instruments that can continuously measure the composition and rate of release (“flux”) of gases and transmit these data directly to volcano observatories where they can be integrated with seismic and ground motion data, thus providing a more comprehensive view of what is going on underground within the volcanic system.

In Yellowstone, changes in the compositions and fluxes of gases from its famous expanses of hissing fumaroles, bubbling pools, and steaming ground may be linked to volcanic and hydrothermal activity. Unfortunately, operating continuous gas sensors in Yellowstone is a considerable challenge—harsh winters and remote locations make powering the equipment and radioing the data back to the observatory difficult—but YVO scientists are making progress. A prototype system operated near Norris Geyser Basin during 2018–2020, providing experience with the power requirements needed to survive the winter months and methods for radioing the data back to scientists using satellite links.  Last year, a new multi-GAS (multicomponent Gas Analyzer System) station (“MUD”) was installed at Mud Volcano thermal area and has provided the first real-time year-round measurements of the concentrations of H2O, CO2, H2S, and SO2 in Yellowstone.  These data are available on the YVO monitoring page ( and show that large seasonal variations occur in gas compositions with low wintertime temperatures, when steam condenses and H2S is “scrubbed” by liquid water, reducing the amount that is detected by the monitoring station. 

Eddy covariance station at Mammoth Mountain, California
Photograph of permanent eddy covariance station installed since 2014 in area of volcanic CO2 emissions on Mammoth Mountain, California. USGS photo by Jennifer Lewicki, August 2019.

This year, scientists greatly enhanced gas monitoring capabilities at the Mud Volcano area with the installation of a new eddy covariance station.  Eddy covariance is a technique that has been used for several decades in agricultural and ecosystem studies to measure the fluxes of gases and heat between plant canopies and the atmosphere.  Although it is relatively new to volcano and hydrothermal monitoring, eddy covariance has been successfully used for over eight years to continuously measure volcanic CO2 emissions on Mammoth Mountain, California.  Eddy covariance thus offers an exciting opportunity to monitor fluxes of both gases and hydrothermal heat from Yellowstone’s thermal basins, changes in which may signal potential hydrothermal or volcanic activity.

Preliminary results show that fluxes of CO2 from the Mud Volcano area are very high (up to ~15,000 grams of CO2 per square meter per day, or roughly 1000 times the CO2 flux from a forest soil).  Although the Mud Volcano area was already known to emit large amounts of CO2, real-time continuous monitoring of CO2, H2O, and heat fluxes, along with wind and atmospheric temperature, pressure, and humidity should greatly enhance understanding of how and why these emissions vary over time.   And together, the MUD multi-GAS and eddy covariance stations should provide a powerful tool for real-time detection of changes in gas and heat emissions that could signal potential unrest within the Yellowstone volcanic system.   

Get Our News

These items are in the RSS feed format (Really Simple Syndication) based on categories such as topics, locations, and more. You can install and RSS reader browser extension, software, or use a third-party service to receive immediate news updates depending on the feed that you have added. If you click the feed links below, they may look strange because they are simply XML code. An RSS reader can easily read this code and push out a notification to you when something new is posted to our site.