A static webcam overlooking Black Diamond Pool in Yellowstone National Park has already captured footage of an eruption, only two weeks after it was installed.
At 8:39 p.m. Saturday, Black Diamond Pool in the Biscuit Basin sent hot, muddy water several feet into the air. The eruption only lasted a few seconds, but it sent a torrent of water out of the crater before subsiding.
The eruption wasn’t anything on the scale of the hydrothermal explosion that occurred on July 23, 2024, but it’s a sign that the pool is active and erratic.
For scientists like Mike Poland, scientist-in-charge of the Yellowstone Volcano Observatory, the footage was exciting and vindicating. They’ve wanted more monitoring equipment at Biscuit Basin since the July 24 explosion, and now they have footage of a recent eruption to analyze.
“Two weeks after we had the thing installed, we had an event like this,” Poland told Cowboy State Daily. “We had the feeling these kinds of things were happening. Now, we can see them, and this will help us better understand the new normal for Black Diamond Pool.”
Small But Significant
Poland has analyzed all the footage recorded before and after the latest eruption. He believes this eruption was caused by “an accumulation of steam” in the subterranean plumbing that feeds Black Diamond Pool.
“In the second before the burst happened, you can see the surface of the pool rise up as if there was a large bubble that was being released,” he said. “It was probably an accumulation of pressure, due to steam that rises to a conduit, then drives that bubble out.”
Poland classified this event as an eruption rather than an explosion, mainly because Black Diamond Pool sent water and only water into the air.
“We usually reserve ‘hydrothermal explosion’ for an event that throws out rocks and either creates a crater or enlarges an existing crater,” he said. “It’s hard to see what's going on in Black Diamond Pool because it's filled with water, but these appear to be a series of repeated smallish eruptions through a pool and not necessarily making a big crater, throwing large amounts of rock, or enlarging an existing crater.”
The July 23 hydrothermal explosion was caused by the energy created when water rapidly expands into steam in a confined space, expanding over 1,000 times its original size. That event sent water hundreds of feet into the air, destroyed the Biscuit Basin boardwalk, and launched large rocks far from the pool.
Nothing that significant has occurred at Biscuit Basin since then, but the ongoing activity is enough to merit observation and raise concerns about the future of Black Diamond Pool.
No Warning
Poland analyzed the footage of Black Diamond Pool before its 8:39 p.m. eruption. He didn’t see anything that indicated an imminent eruption.
“There was nothing obvious,” he said. “A few small bubbles were coming up here and there in the pool, but that's the way this pool works.”
Two eruptions of Black Diamond Pool have been witnessed since July 23, 2024.
On Nov. 5, 2024, scientists were collecting gas samples in Biscuit Basin when Black Diamond Pool had another small eruption. Yet another eruption was observed Jan. 3, 2025, as a winter tour group passed the area. Both events were verified by seismic monitoring, which detected the eruptions as they occurred.
Poland and other scientists are trying to understand “the new normal” for Black Diamond Pool post-explosion. They believe the July 23 event permanently altered the pool’s behavior and plumbing system and have yet to establish its new pattern of behavior.
“We think these smaller eruptions may be a new mode of behavior for the pool, but we didn't have any visual recordings of anything until Saturday night,” he said. “This is the sort of monitoring we need to do in this area to better understand the new behavior of this feature after the big explosion last summer.”
Caught In The Act
Now that a post-explosion eruption of Black Diamond Pool has been caught on video, it will be circulated to volcanologists and geyser experts around the world. Their input will help the Yellowstone Volcano Observatory understand and possibly anticipate what’s happening underneath its 148-degree water.
“I'm sure this sort of activity has been witnessed in other places,” Poland said. “We'll have to spend a lot more time looking at that video and sharing it with geyser experts.”
Saturday’s eruption lasted a few seconds before it was over. Black Diamond Pool is closed to the public for the foreseeable future, which is why the webcam is so valuable for scientists like Poland.
“These events have gone largely unwitnessed because they’re very brief, and you'd have to be in the right place at the right time to see them,” he said. “When we combine what the camera gives us with what we'll have from permanent acoustic and seismic monitoring equipment being installed this summer, we'll have a really nice record of all these events.”
Yellowstone superintendent Cam Sholly has already said the National Park Service won’t reopen Biscuit Basin until they get the go-ahead from the scientists. Those scientists, including Poland, won’t give that go-ahead until they have a degree of confidence in how Black Diamond Pool is going to behave going forward.
For Poland, the eruption was “exciting confirmation” of the need for more monitoring in Biscuit Basin. This event was the first of many he expects to be captured by the webcam, which will help them understand the new, dynamic behavior of Black Diamond Pool and keep visitors safe when it reopens.
“We were all excited by the idea of this webcam, so it’s wonderful to have such quick confirmation of the importance of putting it out there,” he said. “I expect that we will see more of these types of events, so we need to track and document how many times it happens and see whether or not there's any pattern to these eruptions.”
Andrew Rossi can be reached at arossi@cowboystatedaily.com.
