USGS Volcanoes: Notices released in the last day.

Lava continues to slowly erupt within the summit crater at Great Sitkin Volcano. High-resolution satellite images show that lava flows have advanced slightly to the south, and rockfalls from these flows are ongoing. Weakly elevated surface temperatures were observed in satellite views on Saturday. For most of the week, clouds obscured the volcano, but occasional clear views showed no unusual activity. Seismic activity remains low, with only occasional small earthquakes and rockfalls detected.

The current lava eruption began in July 2021 and 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. 

Signs of volcanic unrest at Shishaldin Volcano continued this week. Web camera images, when clear, showed a plume of gas rising from the summit crater. Low-level seismic activity has persisted, with small earthquakes occurring daily. Infrasound signals, likely caused by gas bubbles bursting deep within the volcanic vent, were also detected throughout the week when the conditions were not too windy. At this time, there is no evidence of lava at or near the surface.

Shishaldin Volcano is monitored by local seismic and infrasound sensors, web cameras, and a telemetered geodetic network. In addition to the local monitoring network, AVO uses nearby geophysical networks, regional infrasound and lighting data, and satellite data to monitor the volcano.  

Activity Summary:

Lava overflowed intermittently from the north and south vents in Halemaʻumaʻu overnight with only short breaks between flows. Dome fountaining and spattering have increased this morning along with tremor. Kīlauea summit region showed some overnight inflation on tiltmeter UWD but changed to a slight deflation with the onset of dual overflows this morning. Forecasting models suggest the window for episode 40 sustained lava fountaining is between January 10 and 14 but current activity suggests that episode 40 fountaining could begin anytime. Kīlauea’s East Rift Zone and Southwest Rift Zone remain quiet.

A VAN/VONA notice will be issued at the onset of episode 40 sustained lava fountaining. Short messages tracking the evolution of the fountains and eruptive activity can be found here: HVO - Observatory Messages | U.S. Geological Survey. 

Summit Observations:

The four lava overflows that began on the afternoon of January 8 from the south vent transitioned to nearly continuous overflows from the north vent most of last night and this morning. At 5:12 a.m. HST this morning overflows began again from the south vent fed by 10 foot (3 meter) dome fountains while north vent flows diminished but spattering continued. Both vents began overflowing together around 7:00 a.m. with intermittent pauses of 5-10 minutes. Activity increased just before 7:30 a.m. and fountains roughly doubled in size to 20 feet (6 meters) and have remained constant since then. Seismic tremor increased around 7:00 a.m. when both fountains became active and again at 7:30 a.m. HST as fountaining intensity increased. Fountain heights and tremor have remained relatively constant since then.

Since the end of episode 39, the Uēkahuna tiltmeter (UWD) has recorded 23 microradians of re-inflation beneath Kīlauea summit, an increase of 1.3 microradians in the past 24 hours. Slight deflation began around 5:00 a.m. when the south vent overflowed. The deflation rate on UWD increased slightly at 7:00 a.m. HST when both vents became active and continues to deflate at that rate. The SMC tiltmeter mirrors the UWD tiltmeter, but SDH shows continued inflation, possibly influenced by the deeper south caldera magma chamber.

Volcanic gas emission rates have dropped significantly since the end of episode 39 but probably remain in the range of 1,000 to 5,000 tonnes of sulfur dioxide (SO₂) per day, as typically observed during previous eruptive pauses.  Winds are light out of the north (less than 10 mph or 2 m/sec) and are forecast to become more easterly as the morning progresses. The plume is moving to the south-southwest of Halema'uma'u.

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 and presence of low-level volcanic tremor after episode 39 indicate that another lava fountaining episode is likely to occur.  Nearly continuous overflows of the north vent overnight coupled with overflows from both vents this morning suggest the onset of episode 40 is close.  The increased intensity of fountaining not associated with drainbacks, indicates the magma is becoming progressively more gas rich. Forecast models suggest the window for onset of episode 40 fountaining is between January 10 and 14, but the activity suggests it could start anytime and is highly likely to begin no later than the next 12--24 at the most.

Kīlauea has been erupting episodically since December 23, 2024, primarily from two vents (north and south) in Halema‘uma‘u. Eruptive episodes, which generally last for less than 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 Last Episode:

Episode 39 lava fountaining from the south vent stopped at approximately 2:13 a.m. HST on December 24 after 5.9 hours of sustained fountaining. The two vents within the north cone both stopped slightly earlier at 2:00 a.m. HST. Sustained fountaining began at 8:20 p.m. HST from the north and south vents after just under 2 hours of precursory overflows. Fountains rapidly grew to several hundred feet high and by 9:30 p.m. HST had reach maximum estimated heights of 1,400 feet (425 meters) for the south fountain and 900 feet for the north fountain. The main fountain from the north cone came from the "right hand" vent (as viewed from V1cam, which is pointed south), but a much smaller fountain, 100-200 feet (30–60 meters) high, began at about 8:45 p.m. HST and lasted until the north vent stopped fountaining. This "triple" fountain lasted through most of the eruption, with the south fountain highest followed by the "right hand" north vent (about 65–70% of the south fountain height) and the much smaller "left hand" north vent (about 10–20% of the south fountain height). The highest peak or instantaneous effusion rate of 960 cubic yards per second (800 cubic meters per second) occurred about 9:00 p.m. HST just before the south and north vents reached their maximum heights. Episode 39 ended with an average effusion rate of 250 cubic yards per second (190 cubic meters per second). An estimated 12 million cubic yards (9.3 million cubic meters) of lava erupted and covered about 50–60% of the floor of Halemaʻumaʻu crater. The Uēkahuna tiltmeter (UWD) recorded about 26.8 microradians of deflationary tilt during episode 39.

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. 

• 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 polution) 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, and reticulite—are created by the lava fountains. 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 and eye irritation. More information is available here: https://vog.ivhhn.org/sites/default/files/PelesHair_FAQs_v2.pdf. Close to the vents, the tephra material on the crater rim is prone to cracking, slumping, and small landslides that sometimes expose hot and molten material within. 
• Lava flows: on the floor of Halemaʻumaʻu crater and the southwest side of Kaluapele, Kīlauea's summit caldera, remain hot and may slowly move in the days immediately following an eruptive episode. 

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