USGS Volcanoes: Notices released in the last day.

Minor growth of the active lava dome within the summit crater was observed in satellite imagery over the past week. The south flank of the dome is moving slowly southward and generating occasional small rockfalls. While clouds obscured most satellite views of the volcano, minor steaming from the lava dome was observed in clear webcam views. Seismic activity remains low with occasional small volcanic earthquakes and signals from minor rockfalls caused by lava flow growth. 

The current lava eruption began in July 2021 and has filled most of the summit crater and advanced into the valleys below. There have been no explosions at Great Sitkin Volcano since an event in May 2021. The volcano is monitored using local seismic, geodetic, and infrasound sensors, satellite data, and web cameras, and regional infrasound and lightning networks. 

Volcanic activity remains slightly elevated. Small earthquakes, ongoing tremor, and occasional infrasound signals have continued over the past week. During periods of clear weather, webcam views showed steaming from the summit area. Overall, the frequency and magnitude of earthquakes, infrasound signals, and gas emissions have declined over recent months, indicating a gradual decrease in activity. 

Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. In addition to the local monitoring network, the Alaska Volcano Observatory uses nearby geophysical networks, regional infrasound and lightning data, and satellite data to monitor the volcano. 

Activity Update: All volcanoes in the Cascade Range of Washington and Oregon are at normal background activity levels. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State and Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake in Oregon.

Over the past week, small earthquakes were detected at Mount Rainier, Mount St. Helens, and Mount Hood. All monitoring data remain consistent with background activity levels throughout the Cascade Range. Field crews installed a new station at Crater Lake and performed station maintenance at Newberry.

At Mount Hood, winter conditions have arrived, and the melt pond near Coalman Glacier has begun to freeze over. 

Overview:

The summit eruption of Kīlauea in Halemaʻumaʻu remains paused following episode 55 fountaining on October 17, 2026. Slow, steady inflation continues at the summit. 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 2–9, 2026.

Summit Observations:

Intermittent moderate to strong glow was seen from the west vent overnight, with weaker intermittent glow from the north vent. The south vent remains dark after being buried during episode 55.

Seismic tremor continued yesterday and overnight, with relatively steady background amplitudes interrupted by occasional stronger pulses. These fluctuations are characteristic of the pauses between fountaining episodes, with pulses typically associated with increased glow and gas emissions. Four earthquakes less than M1.5 were recorded in and around Kaluapele (Kīlauea caldera) in the past 24 hours.

Summit tiltmeters have recorded an overall positive trend since the end of episode 55, with several small, short-term oscillations. Though slow, the general pattern remains consistent with post-fountaining re-inflation observed during previous inter-episode pauses. The Uēkahuna tiltmeter (UWD) has recorded an increase of approximately 0.5 microradians in the past 24 hours for a total of 15.4 microradians of tilt recovered since the end of episode 55. 

Sulfur dioxide (SO₂) emission rates during inter-episode pauses typically range from 1,000 to 5,000 tonnes per day. Light and variable winds have volcanic gases lingering around the summit this morning and possibly toward Kaʻū later 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. 

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.

Small plumes of discolored water were seen in the ocean above Ahyi on October 16 and 21 this past week. Discolored greenish water was visible drifting several hundred meters from the summit of Ahyi. These plumes are likely associated with degassing and hydrothermal activity at the summit of the underwater volcano. No notable activity was detected in distal geophysical monitoring data over the past week. 

Eruptive activity at Ahyi seamount may present a hazard to mariners in the water above and near the volcano. The summit has shallowed over the course of previous eruptions to 180 feet (55 m) below sea level, but the lack of local real-time data means we are unable to forecast or warn of impending eruptions. We will continue to monitor satellite and distal hydroacoustic data for additional evidence for, or escalation of, volcanic activity.

NORTHERN MARIANAS VOLCANOES
No signs of unrest were detected at any Northern Mariana Island volcanoes besides Ahyi Seamount during the past week. 

Monitoring of Northern Mariana Islands Volcanoes

Northern Mariana Island volcanoes are monitored using seismo-acoustic sensors on Saipan, and by examining satellite imagery. We also use distant seismic stations in Guam and Chichijima, Japan, and hydroacoustic data from Wake Island, when available.

This level of monitoring can detect significant volcanic activity in the CNMI but cannot provide advanced warning of eruptions.

Due to a lack of geophysical monitoring on any of the volcanic islands, the following volcanoes have alert levels of UNASSIGNED: Anatahan, Sarigan, Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Pagan, Almagan, and Guguan.