USGS Volcanoes: Notices released in the last day.

A satellite radar image on May 18 confirmed that lava continues to slowly advance to the east in the summit crater at Great Sitkin Volcano. Other satellite and webcam images were obscured by clouds. Seismic activity remains low, with occasional small volcanic earthquakes and signals from minor rockfalls within the crater.

The current lava eruption began in July 2021 and has filled most of the summit crater and advanced into the 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.

Earthquakes over the last week were generally small (less than magnitude 2.0) and most were not strong enough to determine locations using regional seismometers. Clouds obscured satellite images of the volcano's surface, but sulfur dioxide gas emissions were observed on one day. 

There is no real-time geophysical monitoring network at Mount Kupreanof. The closest functioning seismometer is approximately 17 miles (27 km) to the east of the volcano as part of the Mount Veniaminof network. Mount Kupreanof is also monitored by satellite data, regional infrasound and lightning networks, and visual observations from pilots and mariners passing by the volcano. 

Seismic and infrasound activity remain elevated, as indicated by numerous small earthquakes, frequent infrasound signals, and volcanic tremor recorded during the week. Clouds obscured all satellite and webcam images of the volcano's surface throughout the week.  Elevated sulfur dioxide gas emissions were detected in satellite data on most days.

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

Small earthquakes associated with lava dome growth and rockfalls were detected in seismic data. Other satellite and webcam images of the volcano were obscured by clouds.

The current eruption began in July 2021 and, 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.

Seismic and infrasound sensors continue to detect frequent small events. Satellite and webcam 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. 

A few small earthquakes were detected with regional seismic stations over the last day. Satellite images were obscured by clouds.

There is no real-time geophysical monitoring network at Mount Kupreanof. The closest functioning seismometers are approximately 17 miles (27 km) to the east 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. 

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 (less than or equal to M1.1) were detected at Mount Rainier, Mount St. Helens, and Newberry Volcano. All monitoring data are consistent with background activity levels in the Cascade Range. Crews were out at Mount St. Helens on Wednesday (May 20) conducting maintenance on monitoring stations.

Overview:

The Halemaʻumaʻu eruption of Kīlauea is paused. Glow was visible from both eruptive vents overnight. Summit reinflation has been underway since lava fountaining episode 47 ended on May 15, and forecast models suggest that episode 48 will occur sometime between Sunday, May 24 and Wednesday, May 27. 

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

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

Summit Observations:

Glow was visible from both Halemaʻumaʻu eruptive vents overnight, though it was brighter at the south vent. 

Low-level seismic tremor continues during the current pause, and has fluctuated over the past day. Earthquake activity beneath Kīlauea summit is low at this time.

Kilauea summit inflation continues.  Over the past day, the inflation rate has been steady but at a lower rate compared to a few days ago. Since the end of lava fountaining episode 47 on May 15, the Uēkahuna tiltmeter (UWD) has tracked approximately 11.4 microradians of inflationary tilt. This instrument recorded 15.6 microradians of deflationary tilt during episode 47.

With the eruption now paused, the sulfur dioxide (SO₂) emission rate from the summit is likely now varying within a typical range of 1,000 to 5,000 tonnes per day. Surface winds are steady out of the northeast at the summit this morning.

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 rapid return of inflationary tilt and glow from both Halemaʻumaʻu eruptive vents indicates that another lava fountaining episode is likely. Lava spattering and overflows from one or both of the eruptive vents are expected to precede the next lava fountaining episode. Forecast models based on summit inflation indicate that episode 48 is likely to occur sometime between Sunday, May 24 and Wednesday, May 27. The forecast window may change as more data are incorporated into the models, and possible periods of slowed inflation or even deflation may delay the onset of episode 48.

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 that can be longer than three 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 episode 47:

Episode 47 ended abruptly at 12:27 a.m. HST on May 15 after 9 hours of continuous lava fountaining from the north vent. The eruptive plume sent light tephra into public areas of Hawai'i Volcanoes National Park and surrounding communities to the northeast. UWD tiltmeter recorded 15.6 microradians of deflation during the episode.

A full summary of episode 47 can be found in a Status Report here: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2026-05-15T10:42:06+00:00

Resources:

NOTE: HVO’s monitoring network is mostly recovered from recent power- and storm-related outages. Several summit stations, including the SDH tiltmeter, will remain offline until we are able to re-establish access across the deep tephra field southwest of the caldera.

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.

NORTHERN MARIANAS VOLCANOES
No definitive signs of unrest were detected at any Northern Mariana Island volcanoes during the past week.

Monitoring of Northern Mariana Islands Volcanoes

Typhoon Sinlaku has caused extensive destruction to the infrastructure on the island of Saipan. All data feeds from seismic and acoustic sensors on the island are now unavailable, and there are no ground-based instruments to detect significant explosive activity in the region, should it occur. It is unknown when connections to these sensors will be restored.

The USGS will continue to monitor satellite images and distant hydroacoustic and seismic sensors for any signs of volcanic activity in the CNMI. This level of monitoring can detect significant volcanic activity but cannot provide advance warning of eruptions.

Due to a lack of geophysical monitoring on any of the volcanic islands, the following volcanoes have alert levels of UNASSIGNED: Anatahan, Sarigan, Farallon de Pajaros, Supply Reef, Maug, Asuncion, Agrigan, Pagan, Almagan, and Guguan.