A year since the Biscuit explosion… are animals leaving the park? (Yellowstone Monthly Update August 2025)

Just over one year ago, early morning visitors to Yellowstone’s Black Diamond Pool suddenly found themselves filming a spectacular event. The July 23, 2024 hydrothermal explosion threw material hundreds of feet high, including rocks that were a foot or more across. Fortunately, most of the rocks were directed away from the visitors on the boardwalk and no one was injured. But the boardwalk was heavily damaged and the area remains closed.

By closely examining rocks that flew out, we've learned that the explosion occurred when the shallow hydrothermal system became sealed by minerals that had been transported in the water. The minerals clogged up the plumbing system and that allowed pressure to build in shallow levels just beneath the surface. An explosion was inevitable.

Since the July 23, 2024 event, Black Diamond Pool has had many small eruptions. Geologists in November 2024 witnessed a small, muddy eruption that went up a few feet, and a tour group saw the same thing in January 2025. In mid-May, scientists with the Yellowstone Volcano Observatory installed a webcam overlooking Black Diamond Pool and it caught its first eruption on May 31, 2025, a muddy eruption of water that went up to 20 to 30 feet. More small events have followed and there seems to be no pattern to how often these eruptions occur and no precursors to the activity.

In late July 2025, YVO installed another monitoring system in the Black Diamond area, with seismic and acoustic monitoring, a GPS station, and a weather station. It will record more data about hydrothermal activity in Biscuit Basin and in the Upper Geyser Basin. For now, the area remains closed to visitors because of the hydrothermal explosion hazard.

During the month of July 2025, the University of Utah Seismograph Stations, which monitors and operates the Yellowstone seismic network, located 52 earthquakes. Deformation trends (subsidence) continue. Steamboat Geyser had a lot of minor activity but no major water eruption. Yellowstone Volcano remains at normal, background levels of activity.

A special thanks to Park visitors Bill Gruen, Sabrina Harris, Joshua Sells, and Juliet Su, for use of their videos of the July 23, 2024, hydrothermal explosion.