USGS Volcano Notice - DOI-USGS-HVO-2026-04-23T19:07:34+00:00

Activity Summary: 

• Episode 45 of the ongoing Halemaʻumaʻu eruption ended abruptly at 10:01 a.m. HST on April 23, 2026, after 8.5 hours of continuous lava fountaining. The eruption is currently paused.
• No significant tephra fallout was reported at visitor areas of Hawaiʻi Volcanoes National Park or on county roads. Winds blew the plume to the south at low altitudes and to the southwest at higher altitudes, with minor amounts of ash fall reported in the community of Pāhala located about 20 miles (32 kilometers) to the southwest of the eruptive vents in Halemaʻumaʻu.

Episode 45 Chronology:

Episode 45 of lava fountaining in Halemaʻumaʻu at the summit of Kīlauea began at 1:34 a.m. on April 23 and stopped at 10.01 a.m. HST the same day, after 8.5 hours of continuous lava fountaining from the north vent. The south vent never fountained during this episode, but it displayed periodic gas jetting and flames. The highest peak of instantaneous effusion rate of just over 390 cubic yards (300 cubic meters) per second occurred around 3:00 a.m. HST on April 23. Episode 45 saw an average effusion rate of 220 cubic yards (170 cubic meters) per second, with an estimated 6.8 million cubic yards (5.2 million cubic meters) of lava erupted and covering about 50% of the Halemaʻumaʻu crater floor. The Uēkahuna tiltmeter (UWD) recorded about 16.0 microradians of deflationary tilt during episode 45.

Episode 45 lava fountaining began at 1:34 a.m. HST on April 23, 2026, just over two days after the onset of precursory lava overflows on the evening of April 20. There were only 3 precursory overflows until about 9:30 p.m. when a series of overflows began from the south vent, accompanied by low dome fountaining. At 1:00 a.m. activity picked up at the north vent, with low fountaining. Over the next half hour, activity continued to increase at the north vent, while decreasing at the south vent. At 1:34, a sharp increase in seismic tremor and deflationary tilt at summit tiltmeters marked the start of the high fountaining episode. North vent fountains grew steadily until their peak at 3:00 a.m. HST. The main body of the fountains reached heights of at least 700 ft (220 meters), however wispy trails at the top of the fountain occasionally reached above 1000ft (300 meters). After their peak, fountain height gradually decreased and were about 330 feet (100 meters) high just before the episode ended abruptly at 10:01 a.m. HST.  

The lava fountain produced significant heat and ash, feeding a plume that reached a maximum height of about 20,000 feet (6,000 meters) above sea level. North to northeastern winds directed the plume and tephra fall to the south and southwest of Halemaʻumaʻu. At 3:22 a.m., the National Weather Service issued an ashfall advisory for communities in the south of the Big Island that has been cancelled with the end of the episode. No significant tephra fallout was reported at visitor areas of Hawai'i Volcanoes National Park or on county roads, but some Pele's hair and fine ash was reported falling in communities at the southern end of the island. 

Earthquake activity during episode 45 was minor, and did not include a repeat of the seismicity observed at the end of episode 44. Levels of seismic tremor rose and fell with fountaining and are now at typical levels for eruption pause. 

Resources:

• Additional short messages during episodes: https://www.usgs.gov/observatories/hvo/observatory-messages   
• Timeline of eruptive episodes since December 23, 2024: https://www.usgs.gov/volcanoes/kilauea/science/eruption-information 
• Three Kīlauea summit livestream videos: https://www.youtube.com/@usgs/streams 
• Report tephra fall: https://hawaiiash.science/report_form 
• Hawaiʻi Volcanoes National Park Information https://www.nps.gov/havo/planyourvisit/conditions.htm
• County of Hawaii Hazard Impact Map: https://www.arcgis.com/apps/dashboards/5865229bcba74020992b372ef18b6f17

Hazard Analysis: 

• Volcanic Gas: Water vapor (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂) are continuously released during an eruption. SO₂ reacts in the atmosphere to create the visible haze known as vog (volcanic smog) downwind, which may cause respiratory and other problems. 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 the links below:
  • https://seagrant.soest.hawaii.edu/resource-and-guidance-for-volcanic-tephra-fall/  
  • https://vog.ivhhn.org/sites/default/files/PelesHair_FAQs_v2.pdf

• 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 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.