USGS Volcano Notice - DOI-USGS-HVO-2026-04-21T18:14:55+00:00

Overview:

Lava flowed from the north vent in Halemaʻumaʻu last night, marking the start of lava fountaining episode 45 precursory activity at the summit of Kīlauea. The Kīlauea Alert Level and Aviation Color Code were raised from ADVISORY/YELLOW to WATCH/ORANGE last night reflecting this change in activity. Overall summit region inflation has continued since the end of episode 44 on April 9, with continued inflation over the past 24 hours. Forecast models currently suggest that lava fountaining episode 45 will start sometime between today, April 21, and Sunday, April 26, with tomorrow, April 22, or Thursday, April 23, most likely. 

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:

Lava flowed from the north vent three times between 7:46 p.m. and midnight last night. Strong glow was consistently visible at both vents in Halemaʻumaʻu overnight, along with prolonged periods of intense flaming visible in the south vent—likely caused by the ignition of volcanic gases escaping the vent. 

Low-level seismic tremor continues during the ongoing eruptive pause, and 15 small-magnitude earthquakes were recorded in Kīlauea summit region in the past 24 hours. Since the end of lava fountaining episode 44 on April 9, the Uēkahuna tiltmeter (UWD) has tracked approximately 16.5 microradians of inflationary tilt, with about 1.5 microradians of inflationary tilt in the past 24 hours. This instrument recorded 17.6 microradians of deflationary tilt in total during episode 44.

During periods of low-level activity precusory to lava fountaining episodes, the sulfur dioxide (SO₂) emission rate from Halemaʻumaʻu likely varies within a typical range of 1,000 to 5,000 tonnes per day. The National Weather Service reports that winds near the eruptive vents will be light today and tomorrow, southerly during the day and northerly overnight and into the early morning hours. 

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, glow from the Halemaʻumaʻu eruptive vents, and lava flowing from the north vent last night indicates that another lava fountaining episode is likely. Additional overflows from one or both of the eruptive vents are expected prior to the start of the next lava fountaining episode. This precursory activity may continue for days and could include low-level spatter and small dome fountains visible within one or both vents. Prolonged precursory activity may delay the onset of episode 45 and forecast models may be adjusted moving forward depending on how activity progresses. Forecast models based on summit inflation currently indicate that episode 45 lava fountains are likely to occur sometime between today April 21, and Sunday, April 26, with April 22 or 23 most likely based on current data.

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 44:

Episode 44 ended at 7:41 p.m. HST on April 9 after 8.5 hours of continuous lava fountaining from the north vent, sending tephra to the north into public areas of Hawai'i Volcanoes National Park and into surrounding communities. UWD tiltmeter recorded 17.6 microradians of deflationary tilt during the episode.

A full summary of episode 44 can be found in a Status Report here: https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2026-04-10T06:25:16+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 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 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.