USGS Volcanoes: Notices released in the last day.

Cloudy conditions for the past week prevented most satellite and webcam observations. Satellite data from September 22, however, showed minor continued growth of the eastern lava flow in the summit crater. Seismic activity remains low, with only occasional minor volcanic earthquakes and signals from small rockfalls related to growth of the lava flow. 

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. Stormy conditions obscured seismic and infrasound signals for parts of the week, but small earthquakes, ongoing tremor, and occasional infrasound signals could be seen during calmer conditions. While clouds obscured most satellite and webcam views, steam plumes were visible in web camera images during clear weather. Satellite data occasionally detected minor sulfur dioxide gas emissions. The frequency and magnitude of earthquakes, infrasound signals, and gas emissions all have declined over recent months.

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. 

Satellite data showed slightly elevated surface temperatures at the volcano on a few days during the week. Steaming from the summit lava flow was visible in webcam and high-resolution satellite images when clear. Seismic activity remains low, with only occasional minor volcanic earthquakes and signals from small rockfalls.

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, with small earthquakes, ongoing tremor, and occasional infrasound signals from minor explosions deep within the conduit. While clouds obscured most satellite and webcam views, steam plumes were visible in web camera images during clear weather. Satellite data occasionally detected minor sulfur dioxide gas emissions. The frequency and magnitude of earthquakes, infrasound signals, and gas emissions all have declined over recent months.

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.

Past Week Observations: During the past week, small earthquakes were detected at Mount Rainier, Mount Hood, and Mount St. Helens. All monitoring data remain consistent with background activity levels throughout the Cascade Range. This week, field crews conducted routine maintenance of monitoring stations at Mount St. Helens and GPS surveys at Mount Rainier.

Overview:

Precursory overflows from the north vent resumed on the night of September 22 and continue this morning. Glow and flames were observed from the north-south-west vent complex throughout the night, with intermittent overflows and spatter bursts from the north vent. There are currently no signs of reactivation of the recent vents 1-6. The summit has inflated slightly over the past 24 hours, and continuous tremor remains the dominant seismic signal across the summit. 

No anomalous seismic activity or deformation has occurred outside of the summit region, and no significant activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone. 

Hurricane Nolo is forecast to impact the Island of Hawaiʻi today and tomorrow with heavy rain and possible high winds.  HVO will continue to monitor volcanic and seismic activity across the island. Poor weather may greatly reduce visibility on streaming cams and webcams available to the public. Monitoring will continue using a variety of geophysical tools.

NOTICE: Hawaiʻi Volcanoes National Park remains closed today during the arrival of Hurricane Nolo

STATUS REPORT on changes in activity and implications for this eruption: USGS Volcano Notice - DOI-USGS-HVO-2026-09-15T03:18:09+00:00

NOTE: Significant changes in activity between Daily Updates are posted here: https://www.usgs.gov/observatories/hvo/observatory-messages

Summit Observations:

Precursory overflows from the north vent resumed on Tuesday night, September 22, beginning at 10:10 p.m. HST. Since then, there have been 26 overflows from the north vent with the last ending at 7:44 a.m. HST this morning. Most of the overflows have lasted about 10-35 minutes and produced lava flows that traveled a few hundred meters (yards) from the vent. Many of the overflows were fed by vigorous fountains that rise 15-30 feet (5-10 meters) above the small 30-50 foot (10-15 meter) cone that has built up at the north vent. The north, south, and west vents continued to glow overnight, and the north and south vent emitted nearly continuous flames. Intermittent spatter bursts were also observed from the north vent last night between overflows. No other areas of incandescence were observed across the summit region last night.

Continuous tremor is the dominant seismic signal across the summit. There were eight small and shallow earthquakes located across the summit region in the past day, but they did not form clusters in time or location. 

Summit tilt has slowly inflated over the past day, with about 0.2 microradians of inflation recorded. The current total inflation since the end of episode 54 is about 16 microradians, which is the previous maximum of inflation that was reached on September 16 and about 3 microradians greater than was lost during episode 54 fountaining.

During inter-episode pauses, the sulfur dioxide (SO₂) emission rate from the summit typically varies between 1,000 and 5,000 tonnes per day. Winds are currently from the northeast but may shift in the days ahead as Hurricane Nolo approaches Hawaiʻi Island.

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:

The north vent resumed precursory overflow activity on Tuesday night, September 22. In addition, the north, south, and west vents continued to glow, and the south and north vent emitted nearly continuous flames. Intermittent spatter was visible from the north vent during pauses in overflow activity. Strong continuous tremor dominates the seismic signal within the summit. Forecast windows for this episode can no longer be modeled due to the irregular changes in inflation and deflation. Since reaching a peak inflation of 16 microradians (UWD tilt post episode 54) on Wednesday September 16, the summit deflated about 2.3 microradians as the new lava flows from vents 1-6 ceased. Slow inflation (recorded on the UWD tiltmeter) started Thursday September 17 and has now recovered the 2.3 microradians lost to the deflation event. Slow inflation of 0.2 microradians was recorded at the summit over the past day equaling the previous maximum total inflation of 16 microradians. Current eruptive activity is focused on the north vent, which has produced the last 11 high fountain events (episodes 44-54). However, it is not possible to say with certainty that this activity will lead to the onset of another fountain event at this time although conditions remain favorable.

Because the summit system remains active and highly pressurized, the two most likely possibilities are that activity continues at the north-south-west vent complex, or it activates another existing weak crack system in the summit region. Neither of these events are likely to produce a strong seismic precursor, so the alert levels have been left at ORANGE/WATCH as the volcano continues to "exhibit heightened unrest with an increased potential for eruption". For further details about potential scenarios see the September 15 Status Report.

Kīlauea has been erupting episodically since December 23, 2024, from two vents (north and south) in Halema‘uma‘u. Lava fountaining episodes, which generally last for less than 12 hours, are separated by pauses of two or more weeks.

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

Summary of episode 54:

A detailed account of episode 54 is given in the HVO Status Report issued on August 25: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2026-08-26T05:56:38+00:00

• Episode 54 of the ongoing Halemaʻumaʻu eruption began around 10:30 a.m. HST and ended at 7:33 p.m. HST on August 25, 2026, after 9 hours of continuous lava fountaining. 
• The maximum lava fountain height from the north vent was approximately 500 feet (150 meters) above ground level, reached between 12:15 p.m. and 1:00 p.m. HST. Neither the south vent nor the new west vent (formerly the collapse pit) fountained during this episode.
• The maximum plume height was approximately 17,000 feet (5,200 meters) above sea level.
• Most tephra fall was restricted to the closed area of Hawaiʻi Volcanoes National Park, southwest of the active eruptive vents in Halemaʻumaʻu. However, HVO did also receive a report of trace Pele’s hair falling in the Ka‘ū district of the Island of Hawaiʻi.

Resources:

NOTE: HVO’s monitoring network is mostly recovered from recent power- and storm-related outages. Several summit stations will remain offline as we continue working to repair instruments and re-establish connections in our monitoring network.

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
• Short messages tracking the evolution of the lava fountains and eruptive activity can be found here: https://www.usgs.gov/observatories/hvo/observatory-messages
• Three Kīlauea summit livestream cameras 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

Hazards:

This episodic eruption is occurring within a closed area of Hawai'i Volcanoes National Park.

• 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/
• Lava flows: Lava on the floor of Halemaʻumaʻu crater and the southwest side of Kaluapele, Kīlauea's summit caldera, remains hot and may slowly move in the days immediately following an eruptive episode.

Other significant hazards exist around Kīlauea caldera from Halemaʻumaʻu crater wall instability, ground cracking, and rockfalls that can be enhanced by earthquakes. 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.

No notable activity was detected in distal geophysical monitoring data or satellite images 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.