Yellowstone’s Biscuit Basin has been closed since a hydrothermal explosion damaged the boardwalk near Black Diamond Pool in July 2024. Less than 2 years later, the same basin is changing again.
At 5:09 a.m. MDT on June 13, monitoring equipment near Black Diamond Pool recorded unusual seismic energy and low-frequency acoustic signals. A research camera showed a dark steam plume rising from an area north of the pool, where geologists found newly opened vents, cracked ground, and near-boiling water moving through the basin.
The event was a hydrothermal explosion, which occurs when hot water beneath the surface flashes to steam and forces water, mud, rock, and debris upward. It was much smaller than the July 2024 blast, but it still left a clear mark on an area Yellowstone officials had already deemed unsafe for public access.
Ground Changed Fast
When Yellowstone geologists inspected the site on June 14, they found three groups of vents north of Black Diamond Pool. Hydrothermal water had flowed from the area into the Firehole River, turning the river a milky gray downstream toward Midway Geyser Basin.
One fissure measured about 61 feet long and up to 5 feet wide. The water inside it was 194 degrees Fahrenheit, close to boiling at that elevation. Another vent group closer to Black Diamond Pool held hot water in fractured rubble, while several smaller vents in the area were either steaming, flowing, or already beginning to shut down.
The most notable change came a few days later. Between June 14 and June 16, a pool of gray, silty, boiling water formed near the middle vent group. The pool measured about 21 by 17 feet and appeared to form when the ground collapsed, not from a second explosion. Scientists noted that there was no fresh debris around the pool that would suggest another blast had occurred.
That sequence is part of what makes the event notable. Geologists had walked across the area on June 14, but by June 16, part of that ground had become a boiling pool.
New Pool Sends Water 30 Feet High
The new pool later became active enough to throw water into the air. On June 18, camera footage showed several short spouting episodes, with boiling water rising roughly 20 to 30 feet. When it was not spouting, geologists reported that the pool was still roiling.
It is not clear whether the feature will keep acting like a small geyser system, cool down, dry up, or continue changing. Yellowstone’s thermal features can shift quickly, especially in areas with recent explosive activity. The June 13 explosion also happened in an area that did not have an obvious thermal feature at the surface before the blast.
For visitors, that is the practical warning. In Yellowstone, unstable ground is not always marked by a pool, spring, or visible vent. Biscuit Basin remains closed, and park officials continue to tell visitors to stay on boardwalks and out of closed thermal areas.
Why Scientists Are Watching This One
No one was injured in the June 13 explosion, nor were any injured in the July 2024 explosion — though that larger blast damaged the boardwalk and threw debris across the basin. The ongoing closure of Biscuit Basin likely kept visitors away from the area when the June 13 blast occurred.
For scientists, the smaller explosion may provide unusually useful data. The event happened about 328 feet from a Biscuit Basin monitoring station installed in 2025, close enough that the station may have recorded seismic and infrasound signals before, during, and after the explosion.
That matters because scientists do not currently have a reliable way to predict hydrothermal explosions. Data from this event could help researchers better understand what, if anything, happens beneath the surface before one of these blasts.
Biscuit Basin remains closed while Yellowstone officials and scientists monitor the vents, fissure, and boiling pool. The park’s volcanic system remains at normal background levels.
