USGS Volcanoes: Notices released in the last day.

Lava continues to erupt in the summit crater of Great Sitkin Volcano. Seismicity at the volcano was at a very low level over the past day. Satellite and web camera images were mostly obscured by clouds.

The current lava eruption began in July 2021 and since then has 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 and web cameras, and regional infrasound and lightning networks.

Unrest continues at Shishaldin with frequent small earthquakes and infrasound signals, possibly caused by gas bubbles bursting deep within the crater, detected over the past day. Vigorous steam emissions were observed in web camera and satellite data. No evidence of elevated surface temperatures in satellite data. 

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 lighting data, and satellite images to detect eruptions. 

Activity Summary:

Eruptive activity is paused. The inflation of the summit and glow from the south vent indicate that fountaining episode is likely, but at least a week away according to preliminary models.  

Summit Observations:

Eruptive activity is paused following the end of episode 37 lava fountaining on Tuesday, November 25. Overnight moderate glow was observed from the south vent along with tremor spikes suggestive of gas pistoning at depth within the vents.

The lava fountaining on Tuesday was associated with about 16.5 microradians of deflationary tilt on the Uēkahuna (UWD) tiltmeter. As of this morning, about 4.5 microradians of inflationary tilt have been recorded by UWD since the end of the episode. Seismic tremor is low.

Gas emissions continue from vent area, with a white outgassing plume rising vertically above the crater this morning.  Sulfur dioxide (SO₂) gas emissions are typically between 1,200 and 1,500 tonnes per day during eruptive pauses between lava fountaining.  

Rift Zone Observations:

Rates of seismicity and ground deformation remain very low in the East Rift Zone and Southwest Rift Zone. SO₂ emissions from the East Rift Zone remain below the detection limit. 

Analysis:

The resumption of inflationary tilt following the end of episode 37 along with glow and tremor indicates that the summit magma reservoir is repressurizing, suggesting that another eruptive episode is likely in the coming weeks.  Preliminary models indicate that the next episode is a week or more away.

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

Recap of previous episode:

Episode 37 fountaining from the north vent stopped at approximately 11:39 p.m. HST on November 25. The south vent was not active during episode 37. Fountains from the north vent reached maximum heights of 500-600 ft (150-180 m). Fountaining lasted for 9.2 hours at an average rate of rate of about 250 cubic yards per second (190 cubic meters per second). Episode 37 produced an estimated 8.2 million cubic yards (6.3 million cubic meters) of lava and covered about 75% of the floor of Halemaʻumaʻu crater. The Uēkahuna tiltmeter (UWD) recorded about 16.5 microradians of deflationary tilt during episode 37.

The following notices provide more information about episode 37::

• VAN VONA End of Episode 37
• VAN VONA Start of Episode 37

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
• Three Kīlauea summit livestream videos 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. High levels of volcanic gas—primarily water vapor (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂)—are one major hazard of concern, as this hazard can have far-reaching effects downwind. As SO₂ is continuously released from the summit during an eruption, it will react in the atmosphere to create the visible haze known as vog (volcanic smog) downwind of Kīlauea. SO₂ and vog may cause respiratory and other problems at high concentrations. Further information on vog can be found at https://vog.ivhhn.org/

Another major hazard is fallout of Pele's hair and other volcanic fragments from lava fountains. Pele's hair is strands of volcanic glass often produced by lava fountaining activity that can be carried well over 10 miles (15 kilometers) from the vent. Other hot glassy volcanic fragments (tephra) including volcanic ash, pumice, scoria, and reticulite can fall on the ground within 1–3 miles (1–5 kilometers) of the eruptive vent(s), with the highest concentrations immediately downwind of the vent(s). Various volcanic fragments have fallen on Highway 11 west of Hawai'i Volcanoes National Park at times, depending on wind and eruption conditions. Strong winds may waft light particles, including Pele's hair, to greater distances downwind. Once on the ground, Pele's hair can sometimes cluster and tangle together, giving it the appearance of a tumbleweed. The extent of Pele's hair deposition is dependent on lava fountaining activity and wind conditions. Residents and visitors should minimize exposure to Pele's hair and other glassy volcanic fragments, which can cause skin and eye irritation and can also contaminate catchment water supplies. More information about how Pele's hair, its hazards, and what to do is available here: https://www.usgs.gov/observatories/hvo/news/volcano-watch-recent-lava-fountains-highlight-peles-hair-hazards. A recently updated Frequently Asked Questions document that includes information about potential health effects of Pele's hair is available here: https://vog.ivhhn.org/sites/default/files/PelesHair_FAQs_v2.pdf

Hawaiian lava flows generally advance slowly downslope, and during this eruption flows have been confined to Halemaʻumaʻu crater and the southwest side of Kaluapele, Kīlauea's summit caldera.

Other significant hazards also remain around Kīlauea caldera from Halemaʻumaʻu crater wall instability, ground cracking, and rockfalls that can be enhanced by earthquakes within the area closed to the public. 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.

There were no observations of unrest at Ahyi Seamount over the past week, but the availability of high-resolution satellite images was limited. No definitive detections from underwater pressure sensors near Wake Island, located 1,410 miles east of Ahyi. 

There are no local monitoring stations near Ahyi seamount, which limits our ability to detect and characterize volcanic unrest there. 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 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, all volcanoes have alert levels of UNASSIGNED. This includes Ahyi, Anatahan, Sarigan, Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Pagan, Almagan, and Guguan.