Dec. 23, 2025 marks one year since the ongoing eruption at Kīlauea began, bringing glowing displays of lava and fountains sometimes as tall as the Empire State Building. It's the first eruption of its kind from Kīlauea in nearly 40 years, according to the U.S. Geological Survey.
“We've only had three similar eruptions in Kīlauea’s history where we've had these episodic fountains,” said Geologist Katie Mulliken of the USGS Hawaiian Volcano Observatory.
Those eruptions from Kīlauea Iki (1959), Maunaulu (1969-1974), and Puʻuoʻo (1983-2018) had between 12 and 44 fountaining episodes. Puʻuoʻo holds the record for the most fountaining episodes, while Kīlauea Iki had the highest fountains recorded, at 1,900 feet.
The current eruption in the Halemaʻumaʻu crater has had 38 episodes so far, with its highest fountain measured during Episode 35 at 1,500 feet. Episode 3 produced the most volume of lava for the eruption, while the most recent episode on December 6th nearly matched it in a much shorter timespan.
“Episode 3 occurred over the span of a week,” explained USGS Geophysicist Ingrid Johanson. “So for these episodes that have been lasting just on the order of hours, it was our largest volume.”
Episode 38 on Dec.6 also gave us a new perspective after a change at a vent caused one of the fountains to quickly switch directions, burying a livestream camera in about 50 feet of tephra, which is small fragments of volcanic rock.
“It was definitely scientifically interesting to watch the camera get engulfed, you can see the particles are incandescent and really hot as they’re falling,” Mulliken describes the footage. “It’s also a good reminder of why the National Park Service keeps that area closed to the public and even, you know, scientists from the Hawaiian Volcano Observatory are very cautious about entering any closed area during these eruptive episodes, because that fallout can happen anywhere along that part of the rim.”
USGS recently replaced the camera and they continue to monitor for signs of the next episode, which is predicted to occur anytime between now and Dec. 26.
“Fundamentally, what we're watching for is for the pressure in the magma chamber to reach a certain level that's sort of similar to where it was in the previous fountaining,” Johanson explains.
So far, scientists haven’t seen a correlation between how much time passes between episodes and how much magma is produced. They are learning that bubbles from escaped gases can make the fountaining more vigorous.
“So as the fountaining itself is getting triggered and you’re starting to see runaway bubble grown, which is very similar to opening a bottle of soda and having it explode all over you, it’s that process and little variations on how that process plays out that are the more likely culprit for the size and vigor of the fountaining” Johanson said.
That process is also what forms tephra which can range from volcanic ash to large light weight rocks. Some of that has landed on the crater rim, forming a puʻu (hill) that Mulliken says now stands about 150 feet above the crater rim.
Each episode has produced an average of about 8 to 12 million cubic meters of lava, adding a total of 200 million cubic meters of lava to the caldera since the eruption began.
“Nearly half of the volume that the caldera collapsed in 2018 has been filled back in,” Mulliken said. “This eruption alone has filled in about a quarter of that 2018 collapse. So the caldera has changed a lot.”
The eruption is also bringing thousands of spectators to the summit. Hawaiʻi Volcano National Park’s monthly use report for November shows visitor numbers for the year were up nearly 15% compared to the same time last year.
“So if you're planning to see the next eruption of Kīlauea or trying to plan to see it, please be patient,” said Public Affairs Specialist Jessica Ferracane. “It is going to be extraordinarily busy, like you have never seen, especially during an eruption. Please listen to park rangers, only park in designated areas, and bring your aloha with you.”
Check the Hawaiʻi Volcanoes National Park website for the latest visitor information and the Hawaiian Volcano Observatory website for eruption information.
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