USGS Volcanoes: Notices released in the last day.

Lava continues to erupt slowly within the summit crater of Great Sitkin Volcano. Small earthquakes and rockfall events were detected but the volcano was seismically quiet over the past day. Clouds obscured the volcano in satellite and webcam images 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, webcams, and regional infrasound and lightning networks.

Low-level unrest continues at the Atka volcanic complex characterized by weak seismic tremor and sulfur dioxide emissions. Satellite views of the volcano were obscured by clouds.

The Atka volcanic complex includes several vents, including Korovin Volcano, Mount Kliuchef and Sarichef Volcano. Korovin has been the site of most historical eruptions that typically produce minor amounts of ash and occasional but small lava flows. The Atka volcanic complex is monitored by local seismic and infrasound sensors and webcam, satellite data, and regional lightning detection instruments.

Unrest continues at Shishaldin Volcano. Seismic and infrasound activity remains elevated, with seismic tremor, and infrasound signals observed over the past day. Sulfur dioxide emissions were detected in satellite data. Satellite and web camera views of the volcano were obscured by clouds over the past day. 

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. 

On Sunday, April 5, 11:41 a.m. HST, a magnitude-3.9 earthquake occurred 2 mi (4 km) east-northeast of Pāhala on the Island of Hawaiʻi at a depth of 2 mi (2 km) below sea level. The earthquake had no apparent impact on either Mauna Loa or Kīlauea volcanoes.

This earthquake is likley related to the seismic swarm under the Pāhala area, which has been going on since 2019. Earthquakes in this region have been observed at least as far back as the 1960s. See https://www.usgs.gov/news/volcano-watch-why-do-so-many-deep-earthquakes-happen-around-pahala for more information. 

The USGS Hawaiian Volcano Observatory continues to monitor Hawaiian volcanoes for any changes. 

EARTHQUAKE DESCRIPTION

• Magnitude: 3.9
• Date and Time: April 5, 2026, at 11:41 a.m. HST
• Location: 2 mi (4 km) ENE of Pāhala
• Depth: 2 mi (2 km) below sea level
• Aftershocks are possible in the coming days to weeks

EARTHQUAKE INTENSITY AND AFFECTED AREA

• Potential Damage: No damage to buildings or infrastructure expected based on earthquake intensity
• Maximum Intensity, Modified Mercalli Scale (https://www.usgs.gov/natural-hazards/earthquake-hazards/science/modified-mercalli-intensity-scale)
• Community-reported: III - weak shaking
• Instrument-derived: IV - light shaking
• Felt Reports: More than 50 within the first half an hour of the event (http://earthquake.usgs.gov/dyfi/)
• Felt Area: Around the Island of Hawaiʻi
• Visit NOAA’s Tsunami Warning Center website for updated information: https://www.tsunami.gov/

EARTHQUAKE MAPS AND ADDITIONAL INFORMATION

• USGS National Earthquake Information Center Maps and Reports for this Event: https://earthquake.usgs.gov/earthquakes/eventpage/hv74931967
• USGS-HVO Interactive Earthquake Map of Hawaiʻi: https://www.usgs.gov/observatories/hawaiian-volcano-observatory/earthquakes

Activity Summary:

Small precursory overflows continue this morning from the south vent. The summit inflated for most of the past 24 hours, with a brief change to deflation at around 6 a.m. HST this morning during the latter duration of a swarm of small earthquakes below Kīlauea summit between 1:50-7 a.m. HST.   Additional overflows and associated spattering are likely to continue until the start of episode 44 fountaining. The current forecast window for episode 44 is April 6-14.

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

NOTE: The National Weather Service (NWS) issued a Special Weather Statement yesterday about the potential for tephra fall from episode 44 in downwind communities especially if it begins in the middle to end of next week when the NWS has forecast possible southerly winds. 

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

Summit Observations:                                                                                                                       

Precursory spattering and lava flows from the south vent began the morning of April 3 and continued over the past 24 hours. In total, more than 30 overflows have occurred from the south vent since the morning of April 3, with accompanying small dome fountains about 3-6 feet (1-2 meters) high. These events were followed by more vigorous spattering when lava drains back into the south vent.  The north vents continued to glow strongly and continuously overnight.

Seismic tremor is continuous with frequent small, poorly-defined bursts possibly related to rise and fall of magma in the vents. Seventy-four small-magnitude earthquakes were recorded at the summit during the past day. Most were smaller than magnitude-2 and occurred between 1:50-7 a.m. this morning, at depths of 3.7-5 miles (6-8 km) below sea level. This activity does not appear to have had an effect on the episode 44 precursory activity, and HVO will continue to closely monitor it.  

Summit tiltmeters UWD and SMC continue to record mostly inflation since the end of episode 43. The UWD tiltmeter has recorded an estimated 24.4 microradians of inflationary tilt since the end of episode 43, with a switch to deflation around 6 a.m. HST this morning. 

During eruptive pauses, like the current conditions, the SO₂ emission rate from the summit has varied within a typical range of 1,000 to 5,000 tonnes of SO₂ per day. Winds remain steady at around 10-15 miles per hour out of the northeast.

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:

Rapid rebound of tilt following episode 43 fountaining, continued tremor, visible glow, and precursory overflows from the vents suggest that another fountaining episode is likely soon. Continued overflows and associated spattering are expected to continue as the start of episode 44 of lava fountaining approaches. Models based on summit inflation indicate that episode 44 fountains are likely to start between April 6 and April 14 with April 6-10 most likely.  Models may change if summit deflation continues for a prolonged period of time.

Kīlauea has been erupting episodically since December 23, 2024, from two vents (north and south) in Halema‘uma‘u. Fountaining episodes, which generally last for less than 12 hours, are separated by pauses that can be longer than 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 episode 43:

Episode 43 ended at 6:21 p.m. HST on March 10 after fountaining for just over 9 hours from both vents and sending tephra into surrounding communities. A complete summary of activity can be found here. 

Resources:

NOTE: HVO’s monitoring network is mostly recovered from 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 south 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 fountains and eruptive activity can be found here: https://www.usgs.gov/observatories/hvo/observatory-messages

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 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 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.