USGS Volcano Notice - DOI-USGS-HVO-2025-09-02T18:45:21+00:00

Activity Summary:

Episode 32 of the ongoing Halemaʻumaʻu eruption is underway. Vigorous north vent lava fountains started around 6:35 a.m. HST this morning and grew to exceed 330 feet (100 meters) in height, inclined to the northeast and feeding lava flows on the western half of the crater floor. Lava fountaining continues at this time and is likely to continue until the late afternoon or evening today. All lava activity is confined to within Halemaʻumaʻu crater, though tephra and Pele's hair may be deposited to the southwest based on prevailing wind conditions.

Summit Observations:

Around 8:30 p.m. HST on September 1, gas pistoning cycles started filling the Halemaʻumaʻu north vent with lava. The first overflow from the north vent occurred at 12:43 a.m. HST this morning.  Two hours later, closely spaced cyclic overflows began and continued until overflows became continuous at 5:31 a.m. HST, being fed by low dome fountain at the vent. The dome fountains escalated in vigor until 6:35 a.m. HST, when tremor and deflation increased significantly marking the onset of lava fountaining episode 32. Afterwards, lava fountains grew to exceed 330 feet (100 meters) in height, inclined at an angle of 45 degrees to the northeast. Around 8:20 a.m. HST, the fountain turned slightly counterclockwise to the north-northeast, and it presently remains pointed this direction. So far, lava flows from the north vent have covered an estimated 40% of the Halemaʻumaʻu crater floor, entirely on its western side.

By the time vigorous lava fountaining started, the Uēkahuna tiltmeter (UWD) had recorded approximately 19.3 microradians of inflationary tilt since the end of episode 31, during which the instrument recorded about 22 microradians of deflationary tilt. As episode 32 lava fountains strengthened, UWD recorded the onset of rapid summit deflation; as of 9:30 a.m. HST, the instrument has recorded nearly 9 microradians of deflationary tilt.

Since the time vigorous lava fountaining started, seismic data streams around Kīlauea summit have been dominated by eruptive tremor. Sulfur dioxide (SO₂) emission rates during lava fountaining episodes are typically around 50,000 tonnes/day.

Strands of volcanic glass known as Pele’s hair are produced during lava fountaining episodes, and deposits have been left throughout the summit area of Hawaiʻi Volcanoes National Park and surrounding communities. These deposits can be remobilized by wind even after lava 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 
• Other 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 notable 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 prevailing deflationary tilt rate and observations of past eruptive episodes suggest that lava fountains are likely to continue until the late afternoon or evening today.

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.