USGS Volcano Notice - DOI-USGS-HVO-2025-03-27T02:40:23+00:00

Activity Summary: 

Episode 15 of the ongoing Halemaʻumaʻu eruption ended at 7:10 p.m. HST on March 26 when fountaining at the south vent stopped. North vent fountains had ceased activity earlier, around 12:00 p.m. HST. Overall, episode 15 lasted just over 31 hours with the last 9 hours consisting of high fountains predominantly from the south vent.

Initial activity from episode 15 included cycles of gas pistoning for roughly 24 hours, followed by fountains from both vents. The transition to high fountains began just after 10:00 a.m. HST today, with early fountain heights growing rapidly in the first 30 minutes to greater than 600 feet (180 meters) high. Later fountaining reached maximum heights over 1,000 feet (305 meters). Additional descriptions of the cyclic gas pistoning and the onset of episode 15 can be found in the Kīlauea daily update from this morning and in the status report marking the onset of high fountaining.

Fountain heights were higher in episode 15 than in previous episodes, continuing the pattern of fountain growth with time. Fountaining reached maximum heights just over 1,000 feet (305 meters) between 11:00 a.m. and 12:00 p.m. and again around 1:30 p.m. HST. Fountain heights in excess of 600-800 feet (180-250 meters) occurred sporadically through the rest of the episode, with more sustained fountaining at somewhat lower heights of roughly 600 feet (180 meters). Just after 1:30 p.m. HST, the south vent fountain began to incline, or bend over, with fountaining directed toward the southeast. The directed/inclined fountaining reappeared intermittently through the afternoon hours, with a maximum inclination approaching 45 degrees. By 5:30 p.m. HST the south vent fountains became vertical again with sustained heights of 500-700 feet (150-215 meters).

During episode 15, lava flows covered about 80-90% of the floor of Halemaʻumaʻu within the southern part of Kaluapele (Kīlauea caldera). Weak winds also resulted in deposition of Pele's hair and tephra in public areas of Hawai'i Volcanoes National Park and in populated areas near Kīlauea summit.

The UWD tiltmeter recorded just under 9 microradians of deflation during episode 15, with just under 7 microradians lost on the SDH tiltmeter. Initial deflation was very rapid, but slowed when north vent fountains ceased fountaining around noon. The end of the eruption was coincident with a rapid change in tilt from deflation to inflation at the summit and a decrease in seismic tremor intensity when the fountains ceased at 7:10 p.m. HST. 

Each episode of Halemaʻumaʻu lava fountaining since December 23, 2024, has continued for at least 13 hours, and up to 8 days, and episodes have been separated by pauses in eruptive activity lasting less than 24 hours to 12 days. 

• Timeline of eruption episodes since December 23, 2024: https://www.usgs.gov/volcanoes/kilauea/science/eruption-information 
• Two Kīlauea summit livestream videos are available here: Kīlauea Volcano, Hawaii (West Halemaʻumaʻu crater) v1cam and Kīlauea Volcano, Hawaii (East Halemaʻumaʻu crater)v2cam

No changes have been detected in the East Rift Zone or Southwest Rift Zone. HVO continues to closely monitor Kīlauea and will issue an eruption update tomorrow morning unless there are significant changes before then. 

Kīlauea Volcano Alert Level/Aviation Color Code remain at WATCH/ORANGE. All current and recent activity is within Hawaiʻi Volcanoes National Park.

Hazards: 

This episodic eruption is occurring within a closed area of Hawai'i Volcanoes National Park. High levels of volcanic gas—primarily water vapor (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂)—are the primary hazard of concern, as this hazard can have far-reaching effects downwind. As SO₂ is continuously released from the summit during an eruption, it will react in the atmosphere to create the visible haze known as vog (volcanic smog) downwind of Kīlauea. SO₂ and vog may cause respiratory and other problems at high concentrations. Further information on vog can be found at https://vog.ivhhn.org/.

Additional hazards include Pele's hair and other volcanic fragments from lava fountains that can fall on the ground downwind of the eruptive vent(s). Pele's hair is strands of volcanic glass produced by lava fountaining activity. Strong winds may waft these light particles to greater distances downwind. Pele's hair can sometimes cluster and tangle together on the ground, giving it the appearance of a tumbleweed. The extent of Pele's hair is dependent on lava fountaining activity and current wind conditions. Residents and visitors should minimize exposure to these volcanic particles, which can cause skin and eye irritation. More information about how Pele's hair is formed is available here: https://www.usgs.gov/observatories/hvo/news/volcano-watch-peles-hairs-a-beautiful-hazard-island-hawaii. A Frequently Asked Questions document developed for the 2022 Mauna Loa eruption includes information about potential health effects of Pele's hair and is available here: https://vog.ivhhn.org/sites/default/files/FAQ_on_air_quality_and_health_during_Mauna_Loa_eruption_v1.6.pdf

Hawaiian lava flows generally advance slowly downslope, and during this eruption flows have been confined to Halemaʻumaʻu and the southwest side of Kaluapele, Kīlauea's summit caldera. 

Other significant hazards also remain around Kīlauea caldera from Halemaʻumaʻu wall instability, ground cracking, and rockfalls that can be enhanced by earthquakes within the area closed to the public. This underscores the extremely hazardous nature of Kīlauea's caldera rim surrounding Halemaʻumaʻu, an area that has been closed to the public since late 2007.