YELLOWSTONE NATIONAL PARK — Scientists have determined that a small hydrothermal explosion took place at the Norris Geyser Basin in Yellowstone National Park (YNP) in April.
This type of explosion, which happens when water underground suddenly flashes into steam, occurs about once a year in Yellowstone, according to a new report by scientists from the Yellowstone Volcano Observatory on the discovery of the event. This year has now seen two such explosions, with a larger one that broke the surface and spewed into the air occurring at Biscuit Basin July 23.
The first clue that a hydrothermal explosion had happened at the Norris Geyser Basin came in May when geologists doing field work there noticed a crater that hadn’t existed when they last examined the area in 2023. The crater was 1 to 2 meters across and surrounded by disrupted ground. Looking at high-resolution satellite images, researchers noted that the thermal features on Porcelain Terrace at the Norris Geyser Basin had gone from being very active to mostly dormant over the period of April 2 to April 21, which gave them a window of time to examine.
A year earlier, this might have been where the investigation ended, as the park has historically not placed monitoring equipment close to thermal features to avoid the distracting noise of boiling water. But as part of the new Volcano and Earthquake Monitoring Plan for the Yellowstone Caldera System, a monitoring station was installed at the Norris Geyser Basin in September 2023. An examination of the station’s infrasound array, which detects low-frequency acoustic energy, showed that a strong signal had come from the direction of the new crater on April 15 at about 2:56 p.m.
“If you want to be able to monitor these things, you need to be close,” Michael Poland, research geologist with the U.S. Geological Survey, told Buckrail. “You need to have equipment in the geyser basin to track this kind of activity.”
Seismometers also detected a signal that was moving at the speed of sound, indicating a surface event and not an earthquake.
“The data that were recorded unequivocally identified the explosion, which is the first time such an event was recognized using geophysical data in Yellowstone National Park,” the report said.
The success of this monitoring technology in detecting the April explosion is promising for identifying other explosions that would otherwise go undetected and even for spotting the early warning signs of an impending dangerous event, the authors reported.
“Using this example, it may be possible to design alarms that can detect future similar events at Norris Geyser Basin using the new monitoring station,” the report said. “The discovery also demonstrates the utility of continued expansion of hydrothermal monitoring in Yellowstone to detect similar events in the future.”
