A small hydrothermal explosion shook Yellowstone National Park’s Biscuit Basin early on the morning of June 13, sending hot water and sediment toward the Firehole River and leaving behind new vents, cracks, and a boiling pool that did not exist just days earlier.
The explosion occurred at about 5:09 a.m. near Black Diamond Pool, in the same general area where a larger, more dramatic hydrothermal explosion occurred in July 2024.
According to the U.S. Geological Survey, monitoring equipment in Biscuit Basin detected unusual seismic energy and a low-frequency acoustic signal called infrasound. A monitoring camera later showed a dark steam plume shooting from the ground north of Black Diamond Pool at 5:09:50 a.m.
No one was hurt. Biscuit Basin has been closed to the public since the 2024 explosion.
Firehole River Turned Milky After the Explosion
As the sun came up, Yellowstone staff noticed something unusual downstream.
The Firehole River had turned a light gray, milky color from Biscuit Basin downstream to Midway Geyser Basin, a distance of about 3.7 miles. USGS said the cloudy color came from suspended sediment that flowed into the river after the explosion.
Geologists also saw new runoff channels from Biscuit Basin into the river.
At first, scientists looked at whether Black Diamond Pool had exploded again. Temperature data from the pool did not show the kind of sharp change normally tied to one of its eruptions. That suggested Black Diamond Pool was not the source of the June 13 event.
Instead, the activity came from newly formed vents north of the pool.
Geologists Found New Vents and a 61-Foot Crack
Yellowstone National Park geologists visited the area the next day and found three groups of newly formed vents.
The northern vent group included a crack about 61 feet long and up to 5 feet wide in some places. Water in the crack measured about 194 degrees Fahrenheit, which is near boiling at that elevation.
The crack was surrounded by rocks thrown out during the explosion, but USGS said the rocks were only tossed a few yards. That means the event was relatively low-energy compared with the July 2024 explosion in the same basin.
A middle group of five small vents had also formed. By the next day, those vents were mostly steaming, but still hot, with temperatures around 185 degrees Fahrenheit.
A southern vent, closer to Black Diamond Pool, was about 49 feet long and had sent hot water and sediment toward the river. Water in the fractured rubble was still about 192 degrees Fahrenheit when geologists checked it.
Then a New Boiling Pool Appeared
When Yellowstone’s geology team returned two days later, they found one of the most striking changes.
A new pool of boiling, gray, silty water had formed near the middle vent group. USGS said the pool was about 21 by 17 feet in size.
The timing is part of what makes the story so remarkable. Ground that geologists had walked across on Sunday had become an actively boiling pool by Tuesday morning.
USGS said the pool did not appear to form from an explosion because there was no surrounding debris. Instead, it likely formed when the ground collapsed.
The pool was not calm. Geologists reported a noticeable thumping sound caused by steam bubbles forming and collapsing inside the pool. On June 18, camera observations showed the pool intermittently spouting water roughly 20 to 30 feet into the air.
Why This Happens in Yellowstone
Hydrothermal explosions happen when hot water underground suddenly flashes into steam.
In a confined space, that rapid change can release enough energy to blast apart the surface above it. Yellowstone has many areas where superheated water, steam, and fragile ground exist close together.
That is why visitors are repeatedly warned to stay on boardwalks and trails in thermal areas. The ground can be thin, unstable, and much hotter than it looks.
Biscuit Basin is one of Yellowstone’s more active and hazardous thermal areas. The area around Black Diamond Pool has produced multiple hydrothermal explosions over more than a century.
Scientists May Learn From This One
Although the June 13 explosion was small by Yellowstone standards, it happened in an unusually useful place for scientists.
USGS said the event occurred about 328 feet from a new Biscuit Basin monitoring station installed in 2025. That means seismic, acoustic, and other instruments may have recorded the event in unusual detail.
Scientists will now review the data to see whether there were any warning signs before the explosion.
That does not mean these events can be predicted yet. USGS said no hydrothermal explosion has ever occurred this close to a monitoring station, which makes the June 13 event an unusual opportunity to study one of Yellowstone’s more unpredictable hazards.
For visitors, the lesson is simpler: Yellowstone’s thermal areas are beautiful, but they are not static. They can change quickly, and sometimes violently.
No one was injured in this case because Biscuit Basin was already closed. But the new boiling pool, the 61-foot crack, and the milky river show how fast the ground can change in one of America’s most visited national parks.
Write a comment