USGS Volcano Notice - DOI-USGS-HVO-2026-11-03T17:31:38+00:00

Overview:

Lava flows began yesterday, November 2, from the north vent in Halemaʻumaʻu and are continuing this morning. Minor deflation that began just around 1:00 p.m. yesterday has slowed and may be turning back to inflation. Seismic tremor at the summit is elevated with fluctuations in tremor associated with the beginning and end of lava overflows. SO₂ emission rates are elevated. Episode 56 high fountaining remains a possibility today or anytime through November 8 based upon prior behavior once precursory flows have begun.

Summit Observations:

Voluminous overflows of lava began erupting from the north vent yesterday at 11:43 a.m. HST. The first two flows lasted over an hour and were highly degassed. The third overflow began at 3:35 p.m. and lasted approximately 40 minutes, forming a small but active dome fountain, which signaled the arrival of more gas-rich magma. Subsequent overflows produced dome fountains approximately 6-7 meters (20-23 feet) high. These typically lasted about 15-20 minutes with breaks of 5-15 minutes in between when lava drained back but remained visible near the top of the vent. After 29 overflows, dome fountains began decreasing around 4:00 a.m. The last few overflows this morning did not produce dome fountains, and lava appears to be retreating further into the vent, disappearing from view between overflows. There have been 42 overflows from the north vent since the start of activity yesterday. One small overflow escaped from the combined southwest vent yesterday at 4:22 p.m. and lasted less than two minutes. Strong glow could be seen from the southwest vent overnight, along with occasional spatter and flames.

Background seismic tremor increased yesterday around 3:30 p.m. and remains elevated as of this morning. Periodic strong tremor bursts associated with the vigorous drain back of lava marking the end of each overflow have diminished since around 3 a.m. HST. Deformation reversed from deflationary tilt to slow inflationary tilt at that time and dome fountains began to drop in size until they were no longer present during overflows this morning.

The Uēkahuna tiltmeter (UWD) had recovered a total of 18.1 microradians of tilt since the end of episode 55 by approximately 12:30 p.m. yesterday. Minor deflation began around 1:00 p.m. yesterday and continued until about 3:00 a.m. this morning. In that time, the UWD tiltmeter recorded a little over one microradian of deflationary tilt. Slow inflationary tilt has occurred since then, though this trend could change at any time.

Sulfur dioxide (SO₂) emission rates averaged 2200 tonnes per day (t/d) yesterday morning. Around 1:00 p.m. they began to increase, and by about 2:30 p.m. average SO₂ emission rates reached approximately 4000 t/d. SO₂ emissions remain elevated this morning, and strong trade winds are carrying volcanic gases southwest toward Kaʻū.

Rift Zone Observations:

Rates of seismicity and ground deformation remain low in the East Rift Zone and Southwest Rift Zone. SO₂ emissions from the East Rift Zone remain below the detection limit. 

Analysis:

Following episode 55 on October 17, 2026, summit tiltmeters initially recorded a typical post-fountaining recovery, with a steady upward trend that gradually slowed and was interrupted by several small fluctuations. Tilt has continued to increase slowly following a brief negative trend on October 26. While the there have been minor fluctuations in tilt over the past week, the overall tilt pattern has been a slow, steady increase until precursory overflows began yesterday, November 2. The UWD tiltmeter recorded a little over one microradian of deflationary tilt before reversing early this morning. Voluminous precursory overflows began before the UWD tiltmeter had the full 21 microradians of tilt lost during episode 55 fountaining, and it appears unlikely to reach that level of inflation with the current fluctuations related to the overflows. Inflation based models are probably not reliable unless steady inflationary tilt returns to the summit. The onset of precursory overflows usually indicates that a new episode of fountaining is within 1-6 days (excluding the period prior to episode 56 marked by new vents and an intrusion). It is reasonable to estimate that the onset of episode 56 fountaining will occur between now and November 8, provided conditions remain stable at the summit.

Kīlauea has been erupting episodically since December 23, 2024, from two primary vents (north and south) within Halemaʻumaʻu at the summit. Lava fountaining episodes generally last less than 12 hours and are separated by pauses of two or more weeks. The buildup to episode 55 differed substantially from previous episodes, with summit tiltmeters recording positive tilt beyond levels typically observed before fountaining, suggesting continued pressurization of the summit magma chamber. This prolonged buildup was punctuated by extended periods of negative or relatively stable tilt, rather than the more consistent upward trends observed before earlier episodes. Episode 55 was also preceded by 39 days of intermittent lava overflows, the longest period of precursory activity recorded before a fountaining episode in the current eruption. During this interval, several short-lived vents opened within Halemaʻumaʻu, and a shallow dike was emplaced beneath Kaluapele.

HVO continues to closely monitor Kīlauea and remains in contact with Hawaiʻi Volcanoes National Park and the Hawaiʻi County Civil Defense Agency regarding eruptive hazards. Kīlauea's volcano alert level and aviation color code remain at ADVISORY/YELLOW.

Summary of episode 55:

A detailed account of episode 55 is given in the HVO Daily Update for October 17: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2026-10-17T15:47:29+00:00  

• Episode 55 of the ongoing Halemaʻumaʻu eruption began at 3:19 a.m. HST on October 17 and ended abruptly at 9:03 a.m. HST on the same day.
• The maximum lava fountain height was approximately 720 feet (220 meters) above ground level from the north vent. The south and west vents never fountained during this episode but did produce overflows prior to the fountaining episode.
• The maximum plume height was approximately 25,000 (7,500 meters) above mean sea level. 
• Tephra fall was restricted mostly to the closed area of Hawaiʻi Volcanoes National Park, southwest of the active Halemaʻumaʻu vents.  

Other notices related to episode 55:

• VAN VONA issued at end of eruption: USGS Volcano Notice - DOI-USGS-HVO-2026-10-17T19:04:00+00:00
• VAN VONA issued at peak fountain heights: USGS Volcano Notice - DOI-USGS-HVO-2026-10-17T14:51:56+00:00
• VAN VONA issued at onset of episode 55 fountaining:  USGS Volcano Notice - DOI-USGS-HVO-2026-10-17T13:25:52+00:00
• NOTE: Changes in the fountain activity have also been posted here: https://www.usgs.gov/observatories/hvo/observatory-messages

Hazards:

Eruptive activity since December 2024 has been occurring within a closed area of Hawai'i Volcanoes National Park. However, recent intrusions highlight that the location of eruptive activity could change. Intrusions can also be hazardous with potential to cause earthquakes, ground cracks, and small landslides. The primary hazards at Kīlauea due to eruptive activity and/or intrusions are:

• Volcanic Gas: High levels of volcanic gas—primarily water vapor (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂)—are continually released during an eruption. Emissions can remain locally hazardous in the areas immediately downwind of the vents, even when the vents are not actively erupting. SO₂ reacts in the atmosphere to create vog (volcanic air pollution) downwind. SO₂ and vog may cause respiratory and other problems at high concentrations. Further information on vog can be found at https://vog.ivhhn.org/
• Tephra: Small glassy volcanic fragments—volcanic ash, pumice, scoria, Pele’s hair and reticulite—are created by the lava fountains. A combination of fountaining dynamics and wind conditions determines where tephra fall may occur for any given eruption episode. Larger particles fall near the vents while light particles may be wafted greater distances. These particles may be remobilized during windy conditions following recent eruptive episodes. Residents and visitors should minimize exposure to these fragments, which can cause skin, eye, and respiratory irritation. More information and guidance on tephra fall hazards is available at https://seagrant.soest.hawaii.edu/resource-and-guidance-for-volcanic-tephra-fall/ and https://vog.ivhhn.org/sites/default/files/PelesHair_FAQs_v2.pdf 
• Lava flows: Hawaiian lava flows generally advance slowly downslope but destroy everything in their paths. Lava flows that erupt within Halemaʻumaʻu remain confined to the crater, including those during the eruption that started in December 2024. However, intrusive activity could result in lava flows outside of Halemaʻumaʻu. Hazards associated with active or recent lava flows include hot and glassy (sharp) surfaces that can cause serious burns, abrasions, and lacerations upon contact with unprotected or exposed skin; uneven and rough terrain can lead to falls and other injuries; hot temperatures that can cause heat exhaustion or dehydration, or in heavy rain can produce steamy ground-fog that can be acidic, severely limiting visibility and sometimes causing difficulty breathing.
• Earthquakes and ground cracks: Shallow magma movement and eruptions can produce minor to severe ground fractures and subsidence features. These ground cracks can continue to widen and offset as magma migration continues, may have unstable overhanging edges, and should be avoided. Other significant hazards exist around Kīlauea caldera from Halemaʻumaʻu crater wall instability, ground cracking, and rockfalls that can be enhanced by earthquakes.

Additionally, close to the eruptive vents, the tephra material on the crater rim is prone to cracking, slumping, and small landslides that sometimes expose hot and molten material within. 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.