Officials revealed details from a preliminary assessment of this week's hydrothermal explosion that sent visitors running and destroyed a boardwalk at Biscuit Basin in Yellowstone National Park. According to Wednesday's announcement, officials say "water suddenly transitioning to steam in the shallow hydrothermal system beneath Black Diamond Pool" caused the explosion on July 23. They also clarified that the explosion "was not caused by volcanic activity" and that "seismicity, ground deformation, and gas and thermal emissions remain at their normal background levels."
The explosion at Biscuit Basin
Video of the incident shows visitors walking along the boardwalk when all of a sudden the ground bursts with a dark cloud. The explosion sent steam and debris hundreds of feet above the ground. And dozens of visitors begin running away for safety. In the announcement, officials describe the extent of the damage, saying the explosion destroyed the boardwalk and ejected grapefruit-sized rocks. "Some blocks closest to the explosion site are about 3 feet (1 meter) wide and weigh hundreds of pounds," officials said. Despite the explosion's destructive power, officials reported no injuries.
As a result of the explosion, officials say that it changed the shape of the Black Diamond Pool "somewhat." But both pools remain murky due to debris and unstable ground around the edges, which occasionally slides into the water. The water level in the pool rose throughout the day, causing roiling to transition to occasional bursts of hot water reaching as high as eight feet in height. By Wednesday, water levels at both Black Diamond and Black Opal Pool rose high enough that they overflowed and sent murky water into the Firehole River, but the bursts had stopped.
The explosions happened, now what?
An aerial view of Biscuit Basin after the July 23, 2024, explosion in Yellowstone National Park. Credit: Joe Bueter/NPS
Because of the changes to the hydrothermal "plumbing" system at Biscuit Basin, officials say small explosions could possibly happen again in the coming days or months. Therefore, geologists with the Park Service and the U.S. Geological Survey will continue to monitor the area. Therefore, they closed off the area for the remainder of the 2024 season.
Officials added that hydrothermal explosions happen inside Yellowstone a few times per year, but they often occur in the backcountry where no people might not notice. They also explained that there have been multiple events of hydrothermal explosions documented throughout the years, including at Porkchop Geyser in 1989, at Porcelain Terrace Area in April 2024, and even another one at Biscuit Basin in 2009.
