USGS Volcanoes: Notices released in the last day.

Lava continues to erupt slowly within the summit crater of Great Sitkin Volcano. Minor earthquakes were detected in the past day. Clouds obscured satellite and webcam images.

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

Slightly elevated seismic and infrasound activity continues. Minor sulfur dioxide emissions were observed in satellite data over the past day, otherwise no other activity was observed in partly cloudy web camera and satellite views.

Local seismic and infrasound sensors, web cameras, and a geodetic network are used to monitor Shishaldin Volcano. In addition to the local monitoring network, AVO uses nearby geophysical networks, regional infrasound and lightning data, and satellite images to detect eruptions. 

Activity Summary: Earthquake activity has increased in the summit region of Kīlauea beneath Halemaʻumaʻu crater and the south caldera region. Ground deformation patterns recorded by summit tiltmeters suggest that magma is intruding beneath the ground in this area, in an east-west orientation, near the western or southern part of Halemaʻumaʻu crater. 

Increased earthquake activity began this afternoon, September 30, 2026, at approximately 2 p.m. HST, underneath Halemaʻumaʻu. Since then, about 40 earthquakes have been detected and activity is still on-going. The largest event, so far, a magnitude 3.4 earthquake, occurred at 9:52 p.m. HST, 1.4 km (0.9 miles) beneath the surface in the northeast part of Halemaʻumaʻu. Starting around 8 p.m. HST., summit tiltmeters began to show extremely rapid changes consistent with crack growth in an east-west orientation possible near the current vent area, suggesting that magma is intruding in this region. 

Historically, east-west trending fissures have erupted in the southeastern part of Halemaʻumaʻu and extending through the Keanakākoʻi crater area all the way to Chain of Craters Road near Lua Manu. The last east-west fissure in this area erupted in September 2023 and extended from the middle of Halemaʻumaʻu to the eastern wall just beneath the Keanakākoʻi overlook. An event of this type is also possible under current conditions. 

Currently, there are no signs of a change at the surface as the existing eruptive vent complex in Halemaʻumaʻu, including the north and south vents, continue to intermittently spatter with strong glow and flames; however, conditions could change quickly. It is possible that this event ends without reaching the surface or it produces a fissure eruption in a new location within the summit caldera region.  

Current activity is restricted to the summit region of Kīlauea. No anomalous activity has been detected in the East Rift Zone or Southwest Rift Zone.  

The USGS Hawaiian Volcano Observatory is monitoring the situation closely and will issue additional messages as needed. 

Kīlauea Volcano Alert Level/Aviation Color Code remains at WATCH/ORANGE. HVO is continuing to closely monitor Kīlauea and is in contact with Hawai‘i Volcanoes National Park and the Hawai‘i County Civil Defense Agency. Please see the Hawaiʻi Volcanoes National Park website for visitor information: https://www.nps.gov/havo/index.htm.     

For more information about the meaning of volcano alert levels and aviation color codes, see https://www.usgs.gov/programs/VHP/volcanic-alert-levels-characterize-conditions-us-volcanoes. 

Overview:

Episode 55 fountaining remains a possibility during the ongoing Kīlauea summit eruption. Overflows from the north vent resumed on the night of September 22. Short, rapid cycles of south vent overflows and lava drainback occurred repeatedly from September 28 through yesterday afternoon. Since yesterday afternoon, both north vent and south vent have had intermittent overflows and spatter, with strong glow overnight. West vent had occasional glow overnight. Summit tiltmeters recorded minor inflation over the past 24 hours. 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.

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:

Overflows from the north vent resumed on the evening of September 22 after about 10 days of quiescence at the vent complex. Overflow activity from the south vent began on September 27. However, the north vent remained dominant until the evening of September 28, when south vent started having short, rapid cycles of overflows and lava drainback that continued through yesterday afternoon. These south vent overflows lasted about 2–5 minutes, with most pauses between each cycle lasting about 5–7 minutes; there were over 100 such overflows. Since yesterday afternoon the frequency of overflow activity has greatly decreased, although intermittent overflows continue at both north and south vents. Since this morning, north vent has had several short-lived overflows with minor dome fountaining. Both north and south vents also spattered overnight and had persistent strong glow, and west vent had occasional glow. 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 20 small and shallow earthquakes located across the summit region in the past day, including a cluster south of Halema'uma'u. 

Summit tiltmeters have recorded minor inflation over the past 24 hours. The Uēkahuna tiltmeter (UWD) recorded approximately 0.8 microradians of inflation. The current total inflation since the end of episode 54 is about 17.4 microradians, which is nearly 5 microradians greater than what 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 forecast from the southeast.

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 overflow activity on September 22. The south vent resumed overflow activity on September 27. The north and south vents continued to have intermittent overflows and spatter, strong glow and emitted flames overnight. Strong continuous tremor dominates the seismic signal within the summit. Forecast windows for a potential episode 55 can no longer be modeled due to the irregular changes in inflation and deflation. Summit tiltmeters recorded net inflation in the past 24 hours, and since the end of episode 54 the total inflation is nearly 5 microradians more than what was lost during episode 54. The north vent has produced the last 11 high fountain events (episodes 44–54). 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.

Yellowstone Caldera activity remains at background levels, with 77 located earthquakes in September (largest = M3.4). Deformation measurements indicate no significant uplift or subsidence of the caldera or north caldera rim for the past several months. A small hydrothermal explosion occurred at Biscuit Basin on September 27.

Recent Work and News

Yellowstone Volcano Observatory scientists spent September in the park conducting geological research, setting up new monitoring stations, and maintaining existing monitoring equipment.  This work included studies of Lower Geyser Basin hydrothermal activity and lakes, recovery of temporary GPS stations, microgravity measurements, maintenance of temperature monitoring stations, establishing a new hydrothermal monitoring station in Upper Geyser Basin, and reestablishing a camera with a view of Yellowstone Lake.

Although there were only sporadic minor eruptions from Steamboat Geyser, in Norris Geyser Basin, during the month (and only 1 major eruption so far in 2026), nearby Echinus Geyser had an eruption on September 15, continuing a trend of occasional eruptions that has persisted throughout most of the year.  In Upper Geyser Basin, Giant Geyser (the second tallest geyser in Yellowstone National Park) erupted on September 10 and 22, its fourth and fifth eruptions of the year.  The geyser appears to be in a new stage of frequent activity for the first time since 2018–2019.

Thermal features in Biscuit Basin, in the Upper Geyser Basin not far from Old Faithful Geyser, remained active in September.  Black Diamond Pool, which was the site of a hydrothermal explosion on July 23, 2024, had several eruptions during the latter half of the month, including one large event that sent water and mud tens of feet (many meters) into the air on the night of September 23.  In addition, the small pool of hot water that formed via collapse after the June 13, 2026, hydrothermal explosion erupted multiple times on September 24 and 27.  Just after 8:12 PM MDT on September 27, the pool was the source of a hydrothermal explosion that threw boiling water, steam, mud, and rocks at least 100 feet (30 meters) into the air—the first such significant explosion from this feature.  The event was well recorded by a nearby seismic, acoustic, and camera monitoring station.

Seismicity

During September 2026, the University of Utah Seismograph Stations, responsible for the operation and analysis of the Yellowstone Seismic Network, located 77 earthquakes in the Yellowstone National Park region. The largest event of the month was a minor earthquake of magnitude 3.4 located about 20 miles northeast of Moran, WY, on September 6 at 10:25 p.m. MDT.

September seismicity in Yellowstone was marked by a small swarm of 24 earthquakes located about 7 miles north-northwest of West Yellowstone, MT, on September 8. The magnitudes ranged from -0.1 to 2.8.

Earthquake activity in Yellowstone is at background levels.

Ground Deformation

Data from continuous GPS stations indicate little net deformation of the caldera or north caldera regions over the past several months.  Subtle variations in ground motion are probably caused by seasonal variations associated with groundwater conditions as summer transitions to fall.

An example of GPS data can be found at http://www.unavco.org/instrumentation/networks/status/pbo/data/NRWY (click on Static Plots / Cleaned)