Volcano Watch — One year of Kīlauea’s episodic summit fountaining: highlighting the hazards

“Volcano Watch” is a weekly article and activity update written by US Geological Survey Hawaiian Volcano Observatory scientists and affiliates. 

On Dec, 23, 2024, a unique eruption began in Kīlauea’s Halemaʻumaʻu crater, with a style of activity not seen for nearly 40 years. The eruption, characterized by high lava-fountaining episodes, has continued for nearly a year. Hawaiʻi Volcanoes National Park visitors see remarkable views, but the latest episode reminds us how quickly hazards associated with this dynamic activity can change.

The current eruption stands out in style and our ability to observe, document, and forecast it. Sustained, repeated high fountaining—where molten lava is lofted hundreds of meters—is uncommon at Kīlauea. Only three other similar eruptions have been documented: the 1959 Kīlauea Iki eruption, the initial fountaining phase of the 1969–74 Maunaulu eruption, and the early episodes of Puʻuʻōʻō from 1983 to 1986. 

Volcano Watch articles in January will review these past eruptions, which lacked today’s dense monitoring network, satellite observations, and real-time cameras. Modern technology has allowed the USGS Hawaiian Volcano Observatory (HVO) to document this eruption style in unprecedented detail, as well as provide timely forecasts of eruption onsets. It has also allowed HVO to better understand how quickly hazards can change, sometimes over minutes.

The ongoing eruption began before dawn on Dec. 23, 2024, and quickly evolved into a sequence of forecastable short-lived, but intense, fountaining episodes (5-40 hours) with one-to-three-week inter-eruptive pauses. The repeated high fountaining, sometimes as high as 1500 feet, has dramatically reshaped the landscape around Halemaʻumaʻu. Pre-existing cracks and fault scarps have been blanketed by tephra, potentially leaving void spaces beneath the surface. A new 140 ft tall pu’u (hill) has been constructed on the northwest rim, and the floor of the caldera has been raised by 223 feet. 

Episode 38, on December 6, 2025, underscored that hazards can escalate abruptly. While the 12 hour-long episode began with fountaining from both vents, it quickly became dominated by the south vent. As the episode intensified, the south vent geometry changed causing it to produce powerful inclined fountaining—over 1,000 ft tall—directed south. HVO’s V3 livestream camera, located about 0.4 mi from the vent, captured video of hot spatter and molten lava as it was destroyed; the site is now buried beneath 32 ft of tephra. Hot tephra also fell as far as HVO’s Sand Hill station, about one mile from the vent, melting plastic components there; Sand Hill is now buried beneath about 4 ft of tephra.

These observations reinforce a key safety message: during high fountaining, life-threatening hazards exist within the area of Hawaiʻi Volcanoes National Park that is closed to the public. The areas of highest hazard depend strongly on whether fountains remain mostly vertical or become inclined, as they did during episode 38, and wind can further increase the range of hot tephra and fine volcanic glass. While tradewinds typically result in tephra deposition to the southwest, they are not always present, especially during the winter months. Tephra fell on Uēkahuna Bluff, only about a mile away from the vents, during episode 4 when there were no tradewinds and significant amounts of Pele’s Hair fell around Kīlauea caldera, as well as in communities neighboring Kīlauea summit. Volcanic air pollution (vog) can be even farther reaching, sometimes affecting neighboring islands.  

Behind the scenes, HVO staff continue to closely monitor Kīlauea. Field engineers snowshoe across thick tephra deposits to dig out and revive buried volcano monitoring stations. Geologists measure tephra deposit thickness and collect samples that help us understand how the eruption is evolving. Geodesists track ground deformation and use those data to forecast when the next episode may begin. Seismologists monitor earthquakes and subtle changes that could signal shifts in the magmatic system. IT specialists maintain monitoring data streams, and administrative, facility, and safety personnel ensure that fieldwork can be carried out efficiently and safely. Together, HVO staff actively monitor this prolonged and dynamic eruption.

As of December 15, 2025, the eruption is paused, with intermittent glow at the south vent. The summit has been reinflating since episode 38 ended, and current forecasts indicate episode 39 could begin between Dec. 22 and 27. 

This eruption is once in a lifetime opportunity to view the power and beauty of Hawaiian fountain eruptions. Please follow guidance posted by Hawaiʻi Volcanoes National Park and remember that closed areas are closed for everyone’s safety.

Volcano Activity Updates

Kīlauea has been erupting episodically within the summit caldera since Dec. 23, 2024. Its USGS Volcano Alert level is WATCH.

Episode 38 lava fountaining happened for 12 hours on Dec. 6. The summit is reinflating and glow has been visible intermittently overnight at both vents. Another fountaining episode is likely between Dec. 22 and 27. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone. 

Maunaloa is not erupting. Its USGS Volcano Alert Level is at NORMAL.

No earthquakes were reported felt in the Hawaiian Islands during the past week.

HVO continues to closely monitor Kīlauea and Maunaloa.

Visit HVO’s website for past Volcano Watch articles, Kīlauea and Maunaloa updates, volcano photos, maps, recent earthquake information, and more. Email questions to askHVO@usgs.gov.