USGS Volcano Notice - DOI-USGS-HVO-2025-10-19T18:26:37+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 Static website content will not be updated until further notice and information may become outdated over time.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 35 of the ongoing Halemaʻumaʻu eruption ended abruptly at 3:32 a.m. HST yesterday, October 18, after 7.5 hours of continuous fountaining. Vent areas and lava flows continue to exhibit slow movement and/or incandescence as they cool and solidify. Kīlauea summit inflation immediately resumed following the end of episode 35, indicating that another fountaining episode is probable, but likely at least two weeks away. The magnitude 4.2 earthquake offshore of Kona this morning had no apparent effect on the ongoing eruption.

Summit Observations:

Intermittent glow, and possibly some flames, continued from both the north and south vents throughout the night, though the north vent was more persistent. Remobilized flows were very active through the day yesterday on the slopes around the cone. Movement slowed significantly by dark, but additional secondary flows and creep of agglutinated tephra is possible in the coming days. The summit continues to rapidly inflate, as is common right after an episode ends. The Uēkahuna tiltmeter (UWD) recorded 2.5 microradians of inflationary tilt over the past 24 hours and 4.7 microradians of inflationary tilt since the end of episode 35. Tremor shows small spikes about every 5 minutes that are characteristic of gas pistoning within the vents. Plumes of gas are rising from both vents this morning and sulfur dioxide gas emissions remain at background levels this morning, typically between 1,200 and 1,500 tonnes per day.

Episode 35 fountains began at approximately 8:05 p.m. HST on October 17 from the north vent. The north vent fountains grew rapidly to heights of 500 feet (150 meters) when the south vent began erupting at 8:50 p.m. The south vent fountains also grew rapidly and within 20 minutes had equaled the north vent fountains in size. By 9:30 p.m. fountain heights from both vents exceeded 1,000 feet (300 meters) and continued to grow. By 10:15 p.m., south vent fountains reached heights of nearly 1,500 feet (460 meters) and north vent fountains reached heights of about 1100 feet (330 meters). These were the highest single fountain and highest pair of fountains seen during this eruption so far. The south vent stopped erupting at approximately 3:29 a.m. followed by the north vent at 3:32 a.m., marking the end of episode 35.

Episode 35 fountains produced an estimated 13 million cubic yards (10 million cubic meters) of lava. The combined average eruption rate was over 500 cubic yards per second (400 cubic meters per second) from the dual fountains. Lava flows from the fountains covered about two thirds of the floor of Halemaʻumaʻu crater. Vent areas and lava flows may continue to exhibit slow movement and/or incandescence as they cool and solidify over the coming days.   

Seismic tremor increased significantly, and summit tilt switched from inflation to deflation last night at about the same time that sustained fountaining began. UWD recorded about 24 microradians of inflationary tilt between the end of episode 34 and the start of episode 35. UWD recorded over 28 microradians of deflationary tilit during episode 35. The end of the eruption was coincident with a rapid change from deflation to inflation at the summit and a decrease in seismic tremor intensity. 

The plume of volcanic gas above episode 35 fountains extended to over 16,000 feet (5,000 meters) above ground level. Volcanic gas emissions greatly decreased after fountaining ended.

The Hawaiʻi County Civil Defense Agency reported that tephra fell on Highway 11 southwest of the vents, and yesterday HVO field crews found tephra along Highway 11 from the 35 mile marker to the 42 mile marker including pumices as large as 6 inches (15 centimeters) in diameter mixed with finer particles and Peleʻs hair. No significant tephra or Pele's hair was reported from the Pāhala or Miloliʻi areas. 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.

Episode 35 was preceded by a series of 35 lava overflow-drainback events at the south vent beginning on October 16 at 7:35 a.m. HST and continuous lava overflows from the north vent beginning on October 17 at 7:28 p.m. The following notices provide more information about earlier parts of episode 35:

• USGS Volcano Notice - DOI-USGS-HVO-2025-10-18T20:28:54+00:00
• USGS Volcano Notice - DOI-USGS-HVO-2025-10-18T10:16:28+00:00
• USGS Volcano Notice - DOI-USGS-HVO-2025-10-18T07:33:48+00:00
• USGS Volcano Notice - DOI-USGS-HVO-2025-10-17T05:15:25+00:00
• USGS Volcano Notice - DOI-USGS-HVO-2025-10-16T21:59:37+00:00

The following links provide more information about the current eruption that began on December 23, 2024:

• 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 pistons: 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 35 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 at least two weeks away based upon the overall deflation of the summit during episode 35.  

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.