USGS Volcano Notice - DOI-USGS-HVO-2026-10-17T15:47:29+00:00

Summit Observations:

Lava fountain episode 55 in Halemaʻumaʻu at the summit of Kīlauea began at 3:19 a.m. HST October 17, 2026, and ended at 9:03 a.m. HST on October 17, 2026, after about 6 hours of continuous fountaining from the north vent.

The onset of episode 55 fountain began at 3:19 a.m. HST as fountains from the north vent began to rapidly increase in height. Maximum fountain heights of 720 feet (220 m) were recorded between 4:50 and 5:10 a.m. HST with the plume cloud reaching up to 25,000 feet (7500 m) above sea level (a.s.l.) during that time. The fountain dropped quickly back to 650 feet and then to 500 feet by 7:00 a.m. HST this morning and was down to about 300 feet (100 m) high by 8:00 a.m. HST. Likewise, the plume cloud dropped to under 13,000 feet (4000 m) a.s.l. by 7:30 a.m. HST. Waning behavior was noted at around 8:50 a.m. and by 9:03 a.m. fountaining had ended. This was accompanied by a return of inflationary tilt patterns and a decrease in summit RSAM. The instantaneous effusion rate peaked at about 1000 cubic yards (770 cubic meters) per second at approximately 5:00 a.m. HST, with an average effusion rate of 380 cubic yards (290 cubic meters) per second for the entire fountaining episode. Preliminary estimates indicate about 9 million cubic yards (7 million cubic meters) of lava erupted during this episode. The repose period leading up to episode 55 was the longest and most complex since the eruption began on December 23, 2024. Initial precursory flows erupted on September 7 preceding episode 55 fountains by 39 days. The next longest period of precursory activity was 6 days. The repose period prior to episode 55 included a series of new vents opening up on September 14-16 along the base of the cliffs on the west side of Halemʻamaʻu as well as an intrusion beneath the northwestern part of Kaluapele September 30 to October 1. 

Lava flows flooded the western part of Halema'uma'u crater and by 8:30 a.m. HST were covering 75% of the crater floor. Fountaining was preceded by continuous overflows from the south vent that began at 5:56 a.m. HST on October 16 and continued until the start of fountaining from the north vent early this morning. Intermittent overflows began from the north vent at 6:11 p.m. HST on October 16 and after 6 small flows started to erupt continuously at 11:35 p.m. last night. Rare overflows from the west vent began at 10:49 p.m. HST last night, with three small overflows preceding the onset of continuous eruption of lava at 2:23 a.m. HST. The north vent fountains doubled in size right around 3:19 a.m. HST at the onset of episode 55, while the south and west vents had small dome fountains that continued to feed flows. The south vent overflows ended at 3:55 a.m. HST while the west vent fountains and overflows were drowned by the north vent at 4:13 a.m. HST.

Tremor had been continuous and steady throughout most of yesterday but began to increase around 2:45 a.m. HST this morning. By 3:19 a.m. HST background tremor measured by RSAM indicate that the intensity of tremor had doubled at the same time rapid deflationary tilt started at the summit. This along with the doubling of the north vent fountain height defined the onset of episode 55 fountaining even though the fountain was less than 100 feet (30 m) high at the time. Tremor rapidly increased to about 10 times background by 4:30 a.m. HST about 20 minutes prior to the fountain reaching its maximum height of 720 feet. Tremor slowly dropped since that time, until the end of fountaining at 9:03 a.m., when it decreased to lower values typical of the immediate post-fountaining period. There were 22 small earthquakes beneath the summit region in the last 24 hours, but only 3 of those occurred in the last 8 hours.

The Uēkahuna (UWD) tiltmeter recorded gradual inflationary tilt throughout the day yesterday until it plateaued around midnight. The tiltmeter recorded minor deflationary tilt beginning around 1:30 a.m. HST. Rapid deflationary tilt began at 3:19 a.m. when the summit magma chamber began to rapidly deflate at the onset of episode 55 fountaining. This quickly turned to inflationary tilt once again with the end of fountaining at 9:03 a.m., as is typically observed following fountaining episodes.

During fountain episodes, the sulfur dioxide (SO₂) emission rate from the summit typically 100,000 tonnes per day. Plumes of volcanic gas and tephra reached as high as 25,000 feet (7000 m) above sea level but dropped rapidly to under 20,000 feet above sea level. Winds below 20,000 feet were out of the northeast, pushing the plume to the southwest. Most tephra fall is expected to occur southwest of the vent area within the closed area of Hawaiʻī Volcanoes National Park, but traces of fine ash and Peleʻs hair in Pāhala and possibly other communities to the southwest in Kaʻū. Sulfur dioxide (SO₂) emission rates from the summit are expected to drop back to 1,000-5,000 tonnes per day. 

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:

Kīlauea had been erupting episodically between December 23, 2024, and August 25, 2026, from two vents (north and south) in Halema‘uma‘u at the summit. Lava fountaining episodes generally lasted for less than 12 hours and were separated by pauses of two or more weeks. Irregular patterns of ground deformation at Kīlauea summit since the previous lava fountaining episode, number 54 on August 25, 2026, prevent forecast modeling for when the next fountaining episode can occur. Ground deformation patterns indicate the magma chamber beneath Halemaʻumaʻu became pressurized beyond the level typically seen before recent fountaining events. This pattern was disrupted by the dike intrusion on September 30-October 1 and since then tiltmeters have recorded inflationary tilt interspersed with periods of deflationary or flat tilt. The vigorous overflows from the south vent starting yesterday morning and joined by the north and west vents late last night appear to have purged the system of older degassed magma and allowed more water-rich magma into the conduit to trigger episode 55 fountaining from the north vent. 

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. Kīlauea volcano alert level and aviation color code remain at WATCH/ORANGE and conditions could change rapidly. For further details, see the recent official notices listed below. 

• 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
• October 7 Status Report summarizing recent intrusive activity and implications: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2026-10-08T01:00:28+00:00 
• October 7 Hawaiʻi Volcanoes National Park News Release announcing closures related to recent activity: https://www.nps.gov/havo/learn/news/20261007-nr-trail-closures.htm 
• October 1 Volcano Watch summarizing recent intrusive activity: https://www.usgs.gov/observatories/hvo/news/volcano-watch-intrusion-during-eruption-summit-kilauea 
• October 1 Status Report published during recent intrusive activity: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2026-10-01T08:14:21+00:00
• September 15 Status Report on changes in activity and implications for this eruption: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2026-09-15T03:18:09+00:00 

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.