USGS Volcanoes: Notices released in the last day.

Lava continues to erupt slowly within the summit crater of Great Sitkin Volcano.  Nothing unusual was observed in partly cloudy satellite and webcam views. Seismicity was mostly quiet over the past day. 

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.

Shishaldin Volcano continues to experience unrest with occasional small earthquakes detected throughout the day yesterday. Nothing unusual was observed in mostly clear satellite and webcam views. Lenticular clouds over the summit prevented any view of potential weak steaming.

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. 

The Alaska Volcano Observatory (AVO) is no longer receiving data from seismic stations on Aniakchak Volcano due to an ongoing power outage at the receive facility in Port Heiden. As a result AVO unable to (1) assess whether the volcano may be building towards an eruption and (2) quickly confirm or dismiss reports of activity.  

Because this volcano is no longer seismically monitored at adequate levels, the Aviation Color Code and Volcano Alert Level are changed to UNASSIGNED/UNASSIGNED.  As at other volcanoes without real-time seismic networks, AVO will continue to use satellite data, regional seismic, infrasound and lightning networks, and reports from pilots and ground observers to detect signs of eruptive activity.

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 December 15 (0000h PST) to December 21 (2359h PST):

Typical seismicity was recorded at The Geysers geothermal field south of the Clear Lake Volcanic Field; 122 earthquakes greater than M1 were recorded, with the largest having a magnitude of M2.9.

Five 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 M1.9.

Two earthquakes greater than M1 were recorded in the Coso Volcanic Field, with the largest having a magnitude of M1.2.

Six earthquakes greater than M1 were recorded near the Salton Buttes, with the largest having a magnitude of M1.9.

Activity Summary:

Glow and intermittent spatter were observed overnight from the north and south vents. Low level tremor has continued over the last 24 hours. The rate of summit inflation remained steady for the past 24 hours. We have entered the forecast window of December 23-26 for the onset of episode 39 lava fountaining. Models indicate episode 39 will most likely begin between December 24 and 25, based on current rates of summit inflation. 

Summit Observations:

Similar to the previous night, continuous glow was observed at the north and south vents overnight. At the north vent, glow was present only on the right hand side of the vents where near continuous spattering over the past two days has built a small inner cone. Spattering continued to be intermittent at the south vent. The presence of low-level, continuous volcanic tremor signals that have marked the past few days continued over the last 24 hours. No gas pistoning has been observed since spattering became visible. 

Since the end of episode 38, Kīlauea has inflated 31.6 microradians as recorded on the UWD tiltmeter this morning with an increase of 1.5 microradians in the last 24 hours. The rate of inflation increased in the last 24 hours.

Volcanic gas emission rates were measured on December 17 at 3,400 tonnes per day of SO2. This rate is somewhat elevated relative to emission rates of 1,200 to 1,500 tonnes per day typically observed during previous eruptive pauses. In addition, this rate is elevated relative to non-eruptive background levels (around 100 tonnes per day).

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 rapid rebound of inflationary tilt, presence of glow and spatter from the north and south vents, and presence of low level volcanic tremor indicate another fountain episode will occur soon. We have entered the forecast window for the onset of episode 39, which is between today, December 23, and Friday, December 26. Inflation models indicate the most likely fountaining onset is between December 24 and 25.

Kīlauea has been erupting episodically since December 23, 2024, primarily from two vents (north and south) in Halema‘uma‘u. Eruptive episodes, which can last up to 12 hours, are separated by pauses that can be as long as over two 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

Recap of previous episode:

Episode 38 fountaining from the south vent stopped at approximately 8:52 p.m. HST on December 6 after 12.1 hours of sustained fountaining. The two vents within the north cone both stopped much earlier at 11:50 a.m. HST.  Sustained fountaining began at 8:45 a.m. HST from the two vents in the north cone after about 5 hours of precursory overflows.  The south vent fountain began at 8:49 a.m. HST and within 10-20 minutes all three fountains were about 500 (150 m) high creating a rare triple fountain.  By 9:40 a.m. HST the south vent fountain grew to about twice as high as the north vent fountains. The highest peak or instantaneous effusion rate of 1,300 cubic yards per second (1,000 cubic meters per second) occurred just before 10 a.m. when the south vent exploded. The enlarged south vent produced an inclined fountain over 1,000 feet (300 meters) tall that sprayed the south wall of Halemaʻumaʻu crater. Hot pumice and molten spatter from this fountain destroyed the HVO "V3" streaming camera site. The south fountain gradually dropped in height throughout the afternoon to about 500 feet (150 meters) high along with declining effusion rates. Episode 38 ended with an average effusion rate of 250 cubic yards per second (190 cubic meters per second). An estimated 16.5 million cubic yards (12.6 million cubic meters) of lava erupted and covered about 50-60% of the floor of Halemaʻumaʻu crater. The Uēkahuna tiltmeter (UWD) recorded about 33.1 microradians of deflationary tilt during episode 38.

The following notices from December 6 provide more information about episode 38:

• Volcano Activity Notice for End of Eruption (9:08 PM HST)
• Status Report on Fountain Height and Loss of V3 camera (10:41 AM HST)
• Volcano Activity Notice for Start of Eruption (8:48 AM HST)
• Kīlauea Update for December 6 (8:25 AM HST)

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
• Two 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.