USGS Volcanoes: Notices released in the last day.

[CORRECTED] The number of earthquakes, intensity of steam emissions, and measured sulfur dioxide emissions beneath Mount Kupreanof have declined. Due to these changes, the Alaska Volcano Observatory is lowering the Aviation Color Code and the Volcano Alert Level to UNASSIGNED. 

Summary of activity and hazards 

• Seismicity was first detected in February 2026 and increased over the following months, with earthquakes as large as magnitude 3.1 recorded. However, seismicity has declined over the past month.
• Sulfur dioxide (SO₂) emissions were detected beginning on April 4 with emission rates of ~100 to 1,000 tons per day, which are well above the background rate of <100 tons per day. These have dropped to background levels since late August.
• Collectively, these data likely indicate the magmatic intrusion beneath Mount Kupreanof has stalled.

Additional information: 

• The Aviation Color Code and the Volcano Alert Level are being changed to UNASSIGNED, rather than GREEN and NORMAL, due to insufficient coverage by ground-based monitoring data.
• An AVO Information Statement from May 8, 2026, gives further details about this activity and interpretations: https://avo.alaska.edu/news/hans/DOI-USGS-AVO-2026-05-08T19:12:14+00:00 
• Learn more about Mount Kupreanof and its current monitoring data on the AVO website: https://avo.alaska.edu/volcano/kupreanof 

The number of earthquakes, intensity of steam emissions, and measured sulfur dioxide emissions beneath Mount Kupreanof have declined. Due to these changes, the Alaska Volcano Observatory is lowering the Aviation Color Code and the Volcano Alert Level to UNASSIGNED. 

Summary of activity and hazards 

• Seismicity was first detected in February 2026 and increased over the following months, with earthquakes as large as magnitude 3.1 recorded. However, seismicity has declined over the past month.
• Sulfur dioxide (SO₂) emissions were detected beginning on April 4 with emission rates of ~100 to 1,000 tons per day, which are well above the background rate of <100 tons per day. These have dropped to background levels since late August.
• Collectively, these data likely indicate the magmatic intrusion beneath Mount Kupreanof has stalled.

Additional information: 

• The Aviation Color Code and the Volcano Alert Level are being changed to UNASSIGNED, rather than GREEN and NORMAL, due to insufficient coverage by ground-based monitoring data.
• An AVO Information Statement from May 8, 2026, gives further details about this activity and interpretations: https://avo.alaska.edu/news/hans/DOI-USGS-AVO-2026-05-08T19:12:14+00:00 
• Learn more about Mount Kupreanof and its current monitoring data on the AVO website: https://avo.alaska.edu/volcano/kupreanof 

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

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.

Unrest continues at Shishaldin Volcano, with minor seismic activity detected in the past day. Webcam and satellite views of the volcano were obscured by clouds. 

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. 

Seismic activity at Kupreanof Volcano over the past day was very low. Cloudy weather obscured satellite views and webcam views of the volcano.

A new temporary monitoring station was installed recently near Mount Kupreanof and is providing seismic data, infrasound data, gas measurements, and web camera images on an intermittent basis. This is by design to conserve battery power, but the frequency of data acquisition can be increased if activity warrants. The closest functioning seismometers that provide continuous data are approximately 10 miles (16 km) to the northeast of the volcano as part of the Mount Veniaminof network. Mount Kupreanof is also monitored by satellite data, remote infrasound and lightning networks, and visual observations from pilots and mariners passing by the volcano.

Monitored CALIFORNIA VOLCANOES
Current Volcano Alert Level: all NORMAL
Current Aviation Color Code: all GREEN

Activity Update: All volcanoes monitored by CalVO show normal background earthquake activity and deformation. Monitored volcanoes include Mount Shasta, Medicine Lake Volcano, Lassen Volcanic Center, Clear Lake Volcanic Field, Long Valley Volcanic Region, Coso Volcanic Field, Ubehebe Craters, and Salton Buttes.

Past Week Observations for August 31 (0000h PDT) to September 06 (2359h PDT):

One earthquake greater than M1 was recorded near Mount Shasta, with a magnitude of M1.9.

Typical seismicity was recorded at The Geysers geothermal field south of the Clear Lake Volcanic Field; 66 earthquakes greater than M1 were recorded, with the largest having a magnitude of M2.3.

Two earthquakes greater than M1 were recorded in the Long Valley Caldera, with the largest having a magnitude of M1.3.

Two earthquakes greater than M1 were recorded in the Sierra Nevada Block, south of Mammoth Mountain and Long Valley, with the largest having a magnitude of M1.7.

Seven earthquakes greater than M1 were recorded in the Coso Volcanic Field, with the largest having a magnitude of M3.1.

Overview:

The summit eruption of Kīlauea in Halemaʻumaʻu is paused. Yesterday at 12:45 p.m. HST precursory overflows started from the north vent, which prompted the alert level to be raised to ORANGE and WATCH. A total of 10 overflows have occurred with the last ending at 1:23 a.m. HST this morning. Their are two lava flow lobes formed during these overflows that have made it around a half a mile (a kilometer) from the north vent. Moderate glow has been seen from the vents since overflows stopped, but heavy rain and steam have obscured most webcam views. Gas piston activity at 5 minute intervals that started around 7:30 p.m. HST Sunday night before the overflows continues this morning. Summit reinflation has been very irregular since lava fountaining episode 54 on August 25. Inflation briefly reached higher than that when episode 54 began but is currently around 0.5 microradians below the episode 54 starting level. A forecast window of September 8-10 is likely for the next episode if inflation resumes and follows the prior patterns.

No significant activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

A detailed summary of lava fountaining episode 54 on August 25, 2026 can be found below.

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

PRECURSORY ALERT LEVEL NOTICE: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2026-09-07T20:09:10+00:00

Summit Observations:

Webcam views have been mostly obscured by heavy rain, clouds, and steam from Hurricane Lowell passing west of the Hawaiian Islands. Precursory overflows from the north vent started yesterday at around 12:45 p.m. HST. There have been 10 overflows from the north vent that have lasted from 16 minutes to 1 hour and 32 minutes long, separated by interludes of 29 to 44 minutes. The last north vent overflow ended at 1:23 a.m. HST this morning. The first overflow produced a very sluggish lava flow with no dome fountain. Subsequent overflows produced more vigorous flows fed by a dome fountain that reached 15-30 ft (5-10 m) tall. Two main lava flows have formed during these overflows with one making it about a half mile (1 kilometer) to the southwest of the north vent, and the other making it less than half a mile (1 kilometer) to the northeast of the north vent. After the overflows ended early this morning, occasion moderate glow was observed from the north vent when it was not obscured by rain and steam. No overflows occurred from the south or west vents, but occasion glow and flames were noted from these vents overnight.

Tremor continues across the summit with regular intervals (about 5 minutes) of gas piston activity. In the absence of views from webcams into the vents during overflow activity, changes in tremor signal were used to time the duration of many of the overflows from the north vent. This was noted as a drop in tremor base level during overflows, with that base level slightly increasing after an overflow ended. Eleven small earthquakes were recorded beneath the summit region, including the south caldera region, over the past 24 hours.

Summit reinflation has been very unsteady since lava fountaining episode 54 on August 25. On Monday around 3:00 p.m. HST, inflation at UWD reached approximately 13.2 microradians of post-episode 54 recovery. Since this inflationary high, UWD has since lost around 1 microradian and subsequently recovered about 0.5 microradians. As of this morning, UWD is at approximately 12.3 out of the 12.7 microradians lost during episode 54.

During inter-episode pauses, the sulfur dioxide (SO₂) emission rate from the summit typically varies between 1,000 and 5,000 tonnes per day. Trade winds continue to be weak this morning and the degassing plume is being pushed towards public overlooks along the north and northeast rims of Kīlauea's summit caldera. South winds are expected to pick up later this morning and could blow volcanic gases as well as fine ash and Peleʻs hair if episode 55 starts, toward the north side of Kaluapele and towards downwind communities.

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:

The abrupt switch from summit deflation to inflation at the end of lava fountaining episode 54 and continued seismic tremor bursts from the Halemaʻumaʻu eruptive vents indicate that another lava fountaining episode may occur in the coming days. Reinflation has been slow and irregular, having been interrupted by multiple deflations of varying magnitude and duration. After inflating over 4 microradians from September 1-3, the summit deflated from Thursday to Friday (September 3-4) morning, after which it stalled for another day. Rapid summit inflation began around 10 a.m. HST on Saturday, September 5 and gained about 9 microradians in the past 2 days. Summit reinflation briefly reached 13.2 microradians at around 3:00 p.m. HST on Monday afternoon, or about 0.5 microradians higher than the 12.7 microradians lost during episode 54. Since this inflationary high, tilt deflated about 1 microradians and then recovered about 0.5 microradians, and is currently at about 12.3 microradians as of this morning. Should summit inflation resume soon, precursory eruptive activity in the form of overflows could also resume with the transition to a lava fountain occurring quickly later today or tomorrow. If tilt remains stalled for a longer period or if a prolonged deflation occurs, then the start of episode 55 could be delayed for several days.

The north vent stopped overflowing at 1:23 a.m. HST this morning, but continued to glow afterwards. Additionally, the west vent and south vent were also observed glowing overnight, when the view was not obscured by rain and steam. This indicates that magma remains high within the vent conduits. Episode 55 activity is likely to start today (Tuesday, September 8) if inflation resumes. If the inflation rate slows or if there are minor periods of stalling or deflation, the onset would be more likely on Wednesday or Thursday, September 9 to 10. Should another significant deflation occur, it could push the forecast for the potential onset of episode 55 fountains back to September 11 to 13.

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.

Precursory low-level activity for episode 55 of the ongoing Halemaʻumaʻu eruption at the summit of Kīlauea began around 12:45 p.m. HST on September 7, 2026 with a sluggish overflow from the north vent. Accordingly, HVO is raising the Alert Level for Kīlauea from ADVISORY to WATCH and the Aviation Color Code from YELLOW to ORANGE. Alert level and aviation color code definitions: https://www.usgs.gov/programs/VHP/alert-level-system. This low-level precursory activity can continue for hours to days before the lava fountaining episode beings. The forecast for episode 55 of lava fountaining to start is between September 7-10. Another VAN will be published when lava fountaining episode 55 begins. Current winds are light from the south and have potential to send volcanic fumes, and possibly tephra during fountaining, northwards past the rim of Kaluapele.

• All eruptive vents and lava flows are confined to Halemaʻumaʻu crater within Hawaiʻi Volcanoes National Park. Tephra fall from volcanic ash clouds is greatest within 3 miles (5 km) of the vents, lighter ash and Pele's Hair may stay suspended for large distances from the vents.
• Support science and community awareness by reporting tephra fall: https://hawaiiash.science/report_form 
• Three Kīlauea summit livestream videos that show eruptive lava fountains are available here: https://youtube.com/@usgs/streams 
• KPcam and MKcam provide views of the plume height for aviation purposes
• Additional short updates as the episode progresses will be posted here: https://www.usgs.gov/observatories/hvo/observatory-messages 
• Timeline of eruptive episodes since December 23, 2024: https://www.usgs.gov/volcanoes/kilauea/science/eruption-information 

Most lava fountaining episodes since December 23, 2024, have continued for a day or less.