USGS Volcano Notice - DOI-USGS-HVO-2026-10-26T18:49:22+00:00

Overview:

The summit eruption of Kīlauea in Halemaʻumaʻu remains paused following episode 55 fountaining on October 17, 2026. After a brief decrease in tilt trends yesterday morning between 3-9 am HST, summit tilt resumed a gradual increase that has continued overnight. Based on current deformation trends and assuming magma chamber inflation follows similar patterns to those established during previous episodes, the forecast window for episode 56 fountaining is November 1–7, 2026.

Summit Observations:

Moderate-to-strong glow persisted at the west vent overnight, while the north vent exhibited weaker incandescence. The south vent remained dark after being buried beneath tephra during episode 55.

Seismic tremor continued throughout the past day, with relatively steady background amplitudes interrupted by occasional stronger pulses. These fluctuations are characteristic of the pauses between fountaining episodes. No earthquakes were observed at Kīlauea summit in the last 24 hours.

Summit tiltmeters have recorded an overall positive trend since the end of episode 55, with several small, short-term oscillations. Approximately 13.4 microradians of tilt have been recovered since the end of fountaining on October 17th, after a total of 21 microradians of rapid deflationary tilt was recorded during fountaining. The general pattern remains consistent with post-fountaining recovery observed during previous inter-episode pauses, although rate of recovery has varied over time. UWD has recorded ~0.7 microradians of gradual, inflationary tilt since 9:15 am HST yesterday. 

Sulfur dioxide (SO₂) emission rates during inter-episode pauses typically range from 1,000 to 5,000 tonnes per day. Light easterly winds are expected to transport volcanic gases west across the Kaʻū Desert today.

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. No significant ground deformation was recorded in either rift zone.

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 gradually over the past 24 hours, following a brief negative trend on October 26. This interruption contributed to shifting the forecast window for episode 56 fountaining to November 1–7, 2026. Given the unusual buildup to episode 55, uncertainty remains as to whether summit deformation will follow a sufficiently consistent pattern to allow for precise forecasting of the next episode.

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.