USGS Volcano Notice - DOI-USGS-HVO-2025-10-01T17:33:50+00:00

During the lapse in appropriations, the USGS Hawaiian Volcano Observatory (HVO) continues to maintain monitoring networks and issue updates and notifications of volcanic activity via the Hazard Notification Service. Volcano monitoring data will continue to be available on the HVO website. Static website content will not be updated until further notice and information may become outdated over time. For more information on the shutdown, please visit the Department of the Interior website at www.doi.gov. 

Activity Summary:

Episode 34 lava fountaining ended this morning, October 1, at 7:03 a.m. HST after approximately 6 hours of continuous eruption. Minor incandescence of the cones and lava flow field may be observed in the coming days as these recently active areas cool. Kīlauea summit region resumed inflation following the end of episode 34, indicating that another fountaining episode is possible, but likely more than a week away.

Summit Observations:

Episode 34 precursory activity began at approximately 9:47 p.m. HST on September 28, with gas pistoning events that produced small, sporadic spatter fountains 10 feet (3 meters) high, and numerous short overflows. Over 120 gas pistoning events occurred intermittently between then and 11:43 p.m. HST on September 30, when sustained overflows and low-level fountaining began within the north vent. Lava fountains within the north vent began to increase in size and volume along with the onset of deflation at 12:53 a.m. on October 1, marking the start of episode 34. Lava fountains from the north vent increased in vigor quickly, reaching up to 330 feet or 100 meters and were inclined slightly to the northeast. At 1:45 a.m. HST on October 1, the south vent began erupting and became the dominant fountain as the episode progressed, reaching vertically up to an estimated 1300 ft (400 m). Fountaining from both vents persisted for just over 6 hours but gradually declined in height.  The two vents generated lava flows that covered a large portion of the western part of Halemaʻumaʻu crater floor with channelized lava flows. The south vent stopped erupting at approximately 7:00 a.m. and the north vent followed shortly after at 7:03 a.m. HST, marking the end of episode 34. Deflationary tilt at UWD totaled approximately 26 microradians during the fountaining, with an estimated volume of approximately 12 million cubic yards (9 million cubic meters or 2.5 billion gallons) of lava erupted overnight. The dual fountains also produced a record combined effusion of 500 cubic yards per second, about twice the maximum eruptive rate measured in previous episodes.  After eruptive activity ceased at 7:03 a.m. HST, the caldera this morning has been quiet with a passive outgassing plume rising from the vents. Scattered incandescence on the lava flow field, due to residual heat, may continue in the coming days as these recently erupted deposits cool over time.  Currently the UWD tiltmeter shows that inflationary tilt has resumed since the end of episode 34, with less than a microradian recorded so far. 

Elevated degassing continues from the vent. Average sulfur dioxide (SO₂) emission rates during pauses are typically 1,200 to 1,500 t/d, though emission rates can vary on short time scales.

Strands of volcanic glass known as Pele’s hair are present throughout the summit area of Hawaiʻi Volcanoes National Park and surrounding communities and can be remobilized by wind even after lava fountaining has ceased.

• Eruption resources, including the most recent map and a timeline of eruption episodes since December 23, 2024: https://www.usgs.gov/volcanoes/kilauea/science/eruption-information
• Three Kīlauea summit livestream videos that show eruptive lava fountains are available here: https://www.youtube.com/@usgs/streams
• Summit eruption webcams: https://www.usgs.gov/volcanoes/kilauea/summit-webcams
• Volcano Watch article on gas pistoning: https://www.usgs.gov/observatories/hvo/news/volcano-watch-so-what-earth-or-least-kilauea-a-gas-piston

Rift Zone Observations:

Rates of seismicity and ground deformation remain very low in the East Rift Zone and Southwest Rift Zone, with no significant earthquake activity in the past 24 hours outside of the summit. Sulfur dioxide (SO₂) emissions from the East Rift Zone remain below the detection limit.

Analysis:

The onset of inflationary tilt following the end of episode 34 indicates that the summit magma reservoir is repressurizing, as in previous episodes, and may produce another lava fountaining episode in the future.  More time and data are needed to calculate an inflation rate and determine when a subsequent lava fountaining episode could occur, but it is likely more than a week away.  

The current eruption has been characterized by episodic lava fountaining not seen in any eruptions since the 1983–86 episodic fountains at the beginning of the Puʻuʻōʻō eruption. Lava fountains and flows have erupted from two vents within Halemaʻumaʻu crater that we refer to as the north vent and south vent. Each of the previous fountaining episodes lasted from a few hours to over a week and was accompanied by strong deflation of the summit region. Pauses between the lava fountaining episodes have been marked by an immediate switch from deflation to inflation as the magma chamber recharges and repressurizes. Lava fountaining episodes have occurred approximately once per week since the start of the current eruption on December 23, 2024.

HVO continues to closely monitor Kīlauea and is in contact with Hawai‘i Volcanoes National Park and the Hawai‘i County Civil Defense Agency about eruptive hazards.

Please see the Hawaiʻi Volcanoes National Park website for visitor information: https://www.nps.gov/havo/index.htm

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 one major 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/

Another major hazard is fallout of Pele's hair and other volcanic fragments from lava fountains. Pele's hair is strands of volcanic glass often produced by lava fountaining activity that can be carried well over 10 miles (15 kilometers) from the vent. Other hot glassy volcanic fragments (tephra) including volcanic ash, pumice, scoria, and reticulite can fall on the ground within 1–3 miles (1–5 kilometers) of the eruptive vent(s), with the highest concentrations immediately downwind of the vent(s). Various volcanic fragments have fallen on Highway 11 west of Hawai'i Volcanoes National Park at times, depending on wind and eruption conditions. Strong winds may waft light particles, including Pele's hair, to greater distances downwind. Once on the ground, Pele's hair can sometimes cluster and tangle together, giving it the appearance of a tumbleweed. The extent of Pele's hair deposition is dependent on lava fountaining activity and wind conditions. Residents and visitors should minimize exposure to Pele's hair and other glassy volcanic fragments, which can cause skin and eye irritation and can also contaminate catchment water supplies. More information about how Pele's hair, its hazards, and what to do is available here: https://www.usgs.gov/observatories/hvo/news/volcano-watch-recent-lava-fountains-highlight-peles-hair-hazards. A recently updated Frequently Asked Questions document that includes information about potential health effects of Pele's hair is available here: https://vog.ivhhn.org/sites/default/files/PelesHair_FAQs_v2.pdf

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

Other significant hazards also remain around Kīlauea caldera from Halemaʻumaʻu crater 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 crater, an area that has been closed to the public since late 2007.