USGS Volcanoes: Notices released in the last day.

Activity Update: All volcanoes in the Cascade Range of Oregon and Washington are at normal background activity levels. These include Mount Baker, Glacier Peak, Mount Rainier, Mount St. Helens, and Mount Adams in Washington State and Mount Hood, Mount Jefferson, Three Sisters, Newberry, and Crater Lake in Oregon.

Past Week Observations: During the past week, small earthquakes were detected at Mount St. Helens and Mount Rainier. All monitoring data are consistent with background levels of activity in the Cascade Range. 

Activity Summary:

The ongoing summit eruption at Kīlauea is paused. Intermittent glow was observed overnight at both the north and south vents. Low level tremor has continued over the last 24 hours. The onset of episode 39 is likely to occur between December 22 and 27.

Summit Observations:

In contrast to the previous 24-hour reporting period, glow was observed at both the north and south vents overnight. Also, continuous, low level volcanic tremor signals were observed. 

Since the end of episode 38, Kīlauea has inflated 26.6 microradians as recorded on the UWD tiltmeter this morning with an increase of 1.6 microradians in the last 24 hours.

Volcanic gas emission rates were measured on 12/17/25 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 and presence of low level volcanic tremor indicate another fountain episode will occur. There are some discrepancies between the inflation models, but the onset of episode 39 is most likely between December 22 and 27. The forecast interval may change if the inflation rate varies.

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.

There were no definitive indications that unrest at Ahyi seamount continued over the past week, although it cannot be ruled out. One low-confidence detection from Ahyi's direction at underwater pressure sensors near Wake Island, located 1,410 miles east of Ahyi, was observed on December 17. Satellite views were mostly cloudy, preventing observations of discolored water over the seamount that have been frequently observed over the past several months. The discolored water could be related to degassing from the active vent. The last view of discolored water was on November 30.

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 definitive signs of unrest were detected at 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.