National Park Service field crews have concluded the explosion at Black Diamond Pool on Tuesday, July 23, in Yellowstone National Park, was not caused by volcanic activity. The explosion resulted from water suddenly transitioning to steam in the shallow hydrothermal system beneath Black Diamond Pool in Biscuit Basin.
Seismicity, ground deformation, and gas and thermal emissions remain at their normal background levels, and there were no detectable precursors to this event, according to a recent NPS news release.
The explosion shot steam and debris hundreds of feet into the air, destroying the nearby boardwalk. Although visitors were there at the time of the explosion and captured it on video, no injuries have been reported.
Debris from the explosion ranged from grapefruit-sized rocks that were shot hundreds of feet from the source to larger blocks that weighed hundreds of pounds nearby. The explosion was primarily directed to the northeast toward the Firehole River. The dark color of the explosion was a result of mud and debris mixed with steam and boiling water.
Just after the eruption, Black Diamond Pool was roiling and spouting water, but no major ongoing activity has been reported.
Both Black Diamond Pool and Black Opal Pool were affected by the explosion, and the shape of Black Diamond has changed. Both pools are murky and surrounded by now-unstable ground, chunks of which have slid back into the water. The water level in both pools is unusually high, sending murky water into the Firehole River.
USGS and NPS geologists have reported that small explosions of boiling water from this area continue to be possible over the coming days to months. These scientists will continue 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 typically occur in the park one to a few times per year, but often in the back country where they may not be immediately detected. Yellowstone NP put out a call to all citizens who observed the event or have photos or videos of Black Diamond Pool, Black Opal Pool, or Wall Pool during the period of July 16-July 23. These “Citizen Scientists” are encouraged to contact the Yellowstone Geology Program at yell_geology@nps.gov.
Yellowstone National Park has closed Biscuit Basin for the remainder of the 2024 season for visitor safety. Grand Loop Road remains open to vehicles, and other nearby thermal basins, like Black Sand Basin, are open. Additional Yellowstone National Park information about visitor access can be found at https://www.nps.gov/yell/index.htm.
