USGS Volcano Notice - DOI-USGS-HVO-2025-08-27T17:27:40+00:00

Activity Summary:

The ongoing Halemaʻumaʻu eruption is paused. Episode 31 ended abruptly at 2:52 a.m. HST on August 23 after over 12 hours of continuous lava fountaining. Last night, no glow was observed at the eruptive vents, though minor incandescence persists in lava flows on the crater floor. Summit reinflation is underway at this time, and episode 32 is likely to occur in the middle to late part of next week, or later if there are unexpected changes in the inflation rate.

Summit Observations:

No glow was visible in webcam views of the Halemaʻumaʻu eruptive vents last night, though minor incandescence was evident in lava flows on the crater floor, which are still in the process of cooling after episode 31.

The Uēkahuna tiltmeter (UWD) recorded about 22 microradians of deflationary tilt during episode 31. The end of the episode on Saturday, August 23 coincided with a rapid change from deflation to inflation at the summit, and a decrease in seismic tremor intensity. The rate of tilt change slowed on Sunday, August 24, but steady inflationary tilt resumed midday yesterday, August 26 and continues at this time; in total, UWD has recorded approximately 10.3 microradians of inflationary tilt since the episode ended. Present patterns of seismic tremor indicate that gas pistoning is continuing deep within the eruptive vents, marked by low-frequency bursts every 5–8 minutes.

Elevated degassing continues from the eruptive vents. Average sulfur dioxide (SO₂) emission rates during inter-episode pauses are typically 1,200 to 1,500 tonnes/day, though emission rates vary on short timescales in association with gas pistoning.  

Strands of volcanic glass known as Pele’s hair are present throughout the summit area of Hawaiʻi Volcanoes National Park and surrounding communities, and can be remobilized by wind even after fountaining has ceased.

• 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
• 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 pistoning: https://www.usgs.gov/observatories/hvo/news/volcano-watch-so-what-earth-or-least-kilauea-a-gas-piston

Rift Zone Observations:

Rates of earthquakes and ground deformation remain very low in the East Rift Zone and Southwest Rift Zone, with no significant seismicity in the past 24 hours. Sulfur dioxide (SO₂) emissions from the East Rift Zone remain below the detection limits of nearby monitoring instruments.

Analysis: 

The return of inflation and gas pistoning after the end of episode 31 indicates that another eruptive episode in Halemaʻumaʻu is likely. Based on the present level of reinflation and the prevailing inflationary tilt rate, forecasting models suggest that episode 32 is likely to occur in the middle to late part of next week (the first week in September). However, the inflationary tilt rate may slow at times, as observed between Sunday, August 24 and yesterday, August 26; similar events have occurred during previous inter-episode pauses and they have delayed the onsets of the subsequent eruptive episodes.

The current eruption has been characterized by episodic lava fountaining not seen in any eruptions since the 1983–86 episodic fountains at the beginning of the Puʻuʻōʻō eruption. Lava fountains and flows have erupted from two vents within Halemaʻumaʻu crater that we refer to as the north vent and south vent. Each of the previous fountaining episodes lasted from a few hours to over a week and was accompanied by strong deflation of the summit region. Pauses between the fountaining episodes have been marked by an immediate switch from deflation to inflation as the magma chamber recharges and repressurizes. Fountaining episodes have occurred approximately once per week since the start of the current eruption on December 23, 2024.

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.

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.