USGS Volcano Notice - DOI-USGS-HVO-2025-08-04T18:18:32+00:00

Activity Summary:

The onset of sporadic precursory activity associated with episode 30 of the Halemaʻumaʻu eruption began at 5:51 a.m. HST on August 4, 2025. A short gas-pistoning event occurred this morning and produced short overflows from the north vent from 5:51 to 5:59 a.m. HST. It was preceded by a weaker gas-piston event with visible lava in the vent from 5:14 to 5:18 a.m. HST, but no lava overflowed the vent.  Low-level seismic tremor and degassing at the summit continues. Summit tiltmeter data continues to fluctuate and has recorded 1.5 microradians of inflation between yesterday morning and this morning, before switching back to slow deflationary tilt around 4:00 a.m. HST that flattened out at 6:00 a.m. HST. Currently, the summit is neither inflating or deflating. Models suggest that episode 30 sustained lava fountaining may start between now and Wednesday.

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

Current hazards include volcanic gas emissions, along with windblown volcanic glass (Pele’s hair) and tephra deposited during earlier eruptive episodes.

Summit Observations:

Lava overflowed from the north vent at 5:51 a.m. HST and drained back with little spattering in the vent by 5:59 a.m. HST in a typical gas-pistoning cycle that produced short overflows. This had been preceded by an earlier gas-pistoning event with lava appearing at 5:14 a.m. HST and draining back with no lava flows and little spattering at 5:18 a.m. HST. Glow was visible from the north vent overnight after re-appearing Thursday evening. Incandescence in other parts of the crater remains very low, with weak, intermittent glow from two areas higher up on the eruptive cone. There has been no movement or incandescent breakouts from lava flows on the floor of Halemaʻumaʻu. Slow slumping of the eruptive cone is possible as it cools.

Elevated degassing continues from the vent. Average sulfur dioxide (SO₂) emission rates during inter-episode pauses are typically 1,200 to 1,500 t/d, though emission rates vary on short time scales in association with gas pistoning. 

Background seismic tremor remains low during the eruption pause. 

Summit tiltmeter records continue to fluctuate over the past several days. UWD recorded 1.5 microradians of deflation between Friday night and Sunday morning, followed by 1.5 microradians of inflation between Sunday morning and this morning around 2:00 a.m. HST. At about 4:00 a.m. this morning slow deflationary tilt began at the summit. Fountaining associated with episode 29 resulted in approximately 19 microradians of deflation. The UWD tiltmeter had re-inflated almost 18 microradians by Friday night, however, fluctuations in tilt since then has dropped the total down to 17.5 microradians since the end of episode 29.  

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 seismicity and ground deformation remain very low in the East Rift Zone and Southwest Rift Zone, with no significant earthquake activity in the past 24 hours. Sulfur dioxide (SO₂) emissions from the East Rift Zone remain below the detection limit.

Analysis: 

Low-level episode 30 precursory activity, along with overall summit inflation, low-level degassing, and seismic tremor, all suggest that episode 30 sustained lava fountaining is likely.  Tilt at the summit has been more variable than usual and has recorded slight deflation at 4:00 a.m. that flattened out at 6:00 a.m. HST with no deflation or inflation since then. Models suggest that sustained lava fountaining may occur between now and Wednesday if inflation resumes. If inflation rates change significantly, the modeled window will change to reflect the new conditions.

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.