YELLOWSTONE NATIONAL PARK — Continuous infrasound monitoring has been established in Yellowstone National Park (YNP), and scientists at the Yellowstone Volcano Observatory (YVO) are listening in on the underground activity of geysers.
According to this week’s Caldera Chronicles written by YVO and Scientist-in-Charge Michael Poland, infrasound refers to low-frequency acoustic energy that is below the range of human hearing. It travels at a significantly slower speed than seismic waves and experiences little atmospheric absorption, which means it can travel great distances and still be detectable.
“Even though infrasound is not something humans can hear, this sound energy can be important for monitoring processes that occur within Earth’s atmosphere,” Poland wrote in Caldera Chronicles.
In September 2023, the first permanent three-sensor infrasound microphone system was installed in YNP in Norris Geyser Basin. This station tracks activity at Steamboat Geyser and has found that infrasound energy from those eruptions is detectable for several hours, indicating an energetic source.
Poland described a three-sensor array in the shape of a triangle as important because it can measure the direction from where an infrasound signal originates. Prior to 2023, infrasound recordings in YNP were from temporary deployments designed to study specific geysers or single microphones that could not determine the location of origin.
The new infrasound station also recorded a powerful sound that lasted about a minute on April 15, 2024. This event was from a small, unwitnessed hydrothermal explosion near Porcelain Basin that left a small crater surrounded by disturbed ground.
“Infrasound therefore provides a powerful means of detecting hydrothermal explosions that might otherwise go unnoticed,” Poland wrote.
Though the station did not detect any sound from the Biscuit Basin hydrothermal explosion last summer, it did record a sound from a “bright fireball in the sky” over the region on May 3, 2025.
YVO hopes to deploy more infrasound stations in the region in the coming years.
YVO also shared a monthly update on Youtube, seen below, that includes information about YNP’s magma chamber and footage of a small hydrothermal explosion in Biscuit Basin captured on the new webcam.
