Some Yellowstone National Park visitors may be keeping an eye out for Sasquatch — a cryptid believed to dwell in the deep forests of North America. At the same time, the Yellowstone Volcano Observatory (YSO) — part of the United States Geological Survey — is also looking for Sasquatch, but in the form of events.
Sasquatch events are rare and mysterious eruptions that occur in thermal pools within Yellowstone National Park. Just like laying eyes on Sasquatch is a captivating event, so too is observing one of these eruptions.
In July of 2024, a large eruption sent debris like mud, rocks, and water about 400 feet into the air at Biscuit Basin. Since then, YSO researchers have been monitoring Black Diamond Pool, where the event occurred within Biscuit Basin, for more eruptions. Catching a glimpse of these eruptions is rare — just like Sasquatch. However, in May of 2025, the researchers finally had their Sasquatch event sighting.
Hydrothermal Explosion History
According to the YSO, Black Diamond Pool has a long and explosive history. It’s even thought that it formed during a hydrothermal explosion between 1902 and 1912.
After the eruption in July 2024, the research team believed these eruptions continued around the pool as more rock and debris were spotted. The monitoring equipment around the pool also indicated that there was some type of activity; however, there were only two other confirmed eruption sightings that fall and winter.
These events disrupted seismic equipment, burying them in mud, knocking them over, and even washing them down a river. Though disrupted, the equipment alerted the research team that at least eight events occurred, though the size and duration data were not available. The data was incomplete, but the little evidence of activity reminded the research team of Sasquatch sightings, and thus they dubbed these events “Sasquatch Events.”
Read More: New Hydrothermal Feature Emerges at Yellowstone National Park
Capturing Sasquatch Events
In an effort to capture these events, the research team installed a webcam at the site. The camera was set up to send images to a public website every 15 minutes. On May 21, 2025, as dawn broke, images showed the area covered in new, loose sediment chunks around the pool, likely from an overnight eruption.
On May 31, 2025, a citizen scientist, observing from the website, also noted recently displaced rocks and damp ground at 8:45 p.m. Those rocks hadn’t been in the 8:30 p.m. image.
With this note, the YSO research team downloaded the camera footage between 8:30 p.m. and 8:45 p.m. and found that an eruption had occurred at 8:39 p.m. The video showed a four-second eruption of steam, water, and sediment that reached nearly 30 feet high.
Finally, the team had their Sasquatch sighting.
Monitoring for Safety
During that eruption, other seismic equipment was able to detect a temperature increase from about 125.2 degrees Fahrenheit to 146.5 degrees Fahrenheit and then back down to 125.4 degrees Fahrenheit during the four-minute eruption. The pool returned to normal about an hour after the event.
Since then, the new camera has captured other eruptions as well, including one in June and two in July. Combined with the seismic equipment already in the field, the video camera adds more to the YSO’s data collection.
“Hydrothermal explosions or eruptions, like the 'Sasquatch' events observed at Black Diamond Pool, are caused by pressure changes resulting from the transition of liquid water to steam," the YSO researchers wrote in a statement. “These explosions are not triggered directly by magma or magmatic gases interacting with shallow groundwater; rather, when water boils in a confined space, expanding steam bubbles build enough pressure to eventually overcome the strength of sealed rock, causing an explosion.”
According to the YSO research team, the July 2024 eruption at Biscuit Basin likely changed the pool's plumbing system, leading to more frequent eruptions. The area still remains closed to visitors as it is unsafe and eruptions are unpredictable. Thanks to the new camera, the park can continue to keep visitors safe.
If you want to take part in some citizen science, you can observe the Black Diamond Pool and report any findings here!
Read More: Yellowstone Bison Meets Tragic End at Hot Spring, Showing the Danger of Hydrothermal Features
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