YELLOWSTONE NATIONAL PARK — Following Tuesday’s hydrothermal explosion in Yellowstone National Park (YNP), the park and the U.S. Geological Survey (USGS) have shared an update, noting that volcanic conditions appear normal near Biscuit Basin but that the area will remain closed for the rest of the 2024 season for visitor safety.
After investigating, geologists determined that the explosion “resulted from water suddenly transitioning to steam in the shallow hydrothermal system beneath Black Diamond Pool and was not caused by volcanic activity,” YNP and USGS said in the statement. “Seismicity, ground deformation and gas and thermal emissions remain at their normal background levels, and there were no detectable precursors to this event.”
The explosion saw steam towering hundreds of feet in the air, turned grey and black by mud and debris. The force ejected “grapefruit-sized rocks,” with some reaching the size of 3 feet wide, weighing hundreds of pounds, per the park. Black Diamond Pool and Black Opal Pool were both affected by the explosion, with Black Diamond changing in shape.
Both pools are still murky from debris, and the edges of the pools remain unstable ground. Black Diamond Pool exhibited “minor roiling and water spouting” immediately after the event. Its water level rose following the explosion, and by Tuesday afternoon, the pool saw bursts of hot water reaching approximately 8 feet in height.
By Wednesday morning, YNP said both Black Diamond and Black Opal pools were overflowing, sending murky water into the Firehole River, but the water bursts at Black Diamond appeared to stop.
“Given the recent changes to the hydrothermal plumbing system, small explosions of boiling water from this area in Biscuit Basin continue to be possible over the coming days to months,” the statement said. “USGS and NPS geologists will be monitoring conditions, mapping the debris field and sampling water to assess any changes in the shallow hydrothermal system over the next several days.”
Hydrothermal explosions are not unprecedented in Yellowstone. YNP notes that Porkchop Geyser saw “similar, although smaller” hydrothermal explosions in 1989, and Porcelain Terrace also saw a smaller one this April. Biscuit Basin’s Wall Pool saw a small explosion in 2009.
“Significant hydrothermal explosions, probably similar in size to that of July 23, 2024, occurred in the 1880s at Excelsior Geyser, in Midway Geyser Basin,” the statement said.
