USGS Volcano Notice - DOI-USGS-HVO-2025-05-06T20:28:26+00:00

Activity Summary:

Episode 20 of the ongoing Halemaʻumaʻu eruption ended on May 6 at 9:58 p.m. HST after 4.5 hours of sustained fountaining. The eruption is currently paused. The rapid rebound of recorded summit tilt from deflation to inflation at the end of episode 20 suggests another episode is likely.

The sustained lava fountaining phase of episode 20 began at 5:28 p.m. and ended at 9:58 p.m. on May 6, 2025. Fountains from the north vent reached heights of more than 500 feet (150 meters). Fountains from the south vent reached heights of up to about 65 feet (20 meters). Lava flows covered approximately half of Halema'uma'u crater floor. Approximately 3 million cubic yards (2.5 million cubic meters) of lava erupted during the sustained fountaining phase of episode 20, with an average effusion rate of about 153 cubic yards (140 cubic meters) per second. The effusion rate during the first 30 minutes of sustained fountaining was on the order of 262 cubic yards (200 cubic meters) per second.

Kīlauea's current eruption in Halemaʻumaʻu crater within Kaluapele (the summit caldera) began on December 23, 2024. There have now been 20 episodes separated by pauses in activity. All eruptive activity remains within Hawaiʻi Volcanoes National Park. No significant activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone. Current hazards include volcanic gas emissions and windblown volcanic glass (Pele’s hair) and tephra that have impacted Hawaiʻi Volcanoes National Park and nearby communities.

Summit Observations:

Lava fountains and flows erupted from both vents, but the north vent was much more active than the south vent during all phases of episode 20. The sustained fountaining phase lasted 4.5 hours and was preceded by almost 31 hours of precursory low-level activity. Strong glow was visible overnight from both vents after episode 20 ended, indicating that magma remains close to the surface. Strong glow was also visible across Halema'uma'u crater floor as lava flows continued to cool, overturn and solidify after episode 20 ended.

The end of episode 20 fountaining activity was accompanied by a rapid change in summit tilt from deflation to inflation, along with a rapid decrease in tremor. The Uēkahuna tiltmeter (UWD) recorded approximately 6 microradians of deflationary tilt between the start and end of episode 20 sustained fountaining. The Sand Hill tiltmeter (SDH) recorded approximately 5 microradians of tilt for the same period. UWD and SDH have both recorded approximately 1 microradian of inflation since the end of episode 20.

A sulfur dioxide (SO₂) emission rate of approximately 1,750 tonnes per day (t/d) was measured on May 2 during the pause between episodes 19 and 20. SO₂ emission rates of 4,000 to 6,000 t/d were measured during gas-pistoning events during episode 20 precursory low-level activity on May 5-6. SO₂ emission rates during episode 20 sustained fountaining were likely up to 50,000 t/d based on measurements recorded during previous episodes.

Strands of volcanic glass known as Pele’s hair from previous episodes are still present throughout the summit area of Hawaiʻi Volcanoes National Park and surrounding communities, and can be remobilized by wind.

• 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 
• Two Kīlauea summit livestream videos are available here: Kīlauea Volcano, Hawaii (West Halemaʻumaʻu crater) v1cam and Kīlauea Volcano, Hawaii (East Halemaʻumaʻu crater) v2cam
• Summit eruption webcams: https://www.usgs.gov/volcanoes/kilauea/summit-webcams 

The B2, KW, and F1 summit webcams are currently offline. Other HVO summit webcams are functioning and online.

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: 

The current eruption has been characterized by episodic fountaining not seen in any eruptions since the 1983-86 episodic fountains at the beginning of the Puʻuʻōʻō eruption. Fountains and lava flows have erupted from two vents that we refer to as the north vent and south vent. Each of the previous 19 fountaining episodes lasted from a few hours to over a week and have been accompanied by strong deflation of the summit region. Pauses between the fountaining episodes have been marked by an immediate change from deflation to inflation as the magma chamber recharges and repressurizes.

The rapid rebound of recorded UWD and SDH tilt from deflation to inflation at the end of episode 19, along with ongoing cycles of low-level fountaining, indicate that another episode of sustained fountaining is likely. Data indicate that episode 20 is likely to start between now and tomorrow, Tuesday to Wednesday this week.  As more data becomes available, the window may be adjusted.

• Volcano Watch article about Pele's hair from this eruption: https://www.usgs.gov/observatories/hvo/news/volcano-watch-recent-lava-fountains-highlight-peles-hair-hazards

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 Hawaiʻi Volcanoes National Park. High levels of volcanic gas—primarily water vapor (H₂O), carbon dioxide (CO₂), and sulfur dioxide (SO₂)—are the primary 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/

Additional hazards include Pele's hair and other volcanic fragments from lava fountains. Pele's hair is strands of volcanic glass often produced by lava fountaining activity. Volcanic fragments can fall on the ground within a few hundred yards (meters) of the eruptive vent(s), or downwind of the vent(s). Strong winds may waft light particles, including Pele's hair, to greater distances downwind. Once they are 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 current wind conditions. Residents and visitors should minimize exposure to Pele's hair and other volcanic fragments, which can cause skin and eye irritation. More information about how Pele's hair forms, 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 Frequently Asked Questions document developed for the 2022 Mauna Loa eruption includes information about potential health effects of Pele's hair and is available here: https://vog.ivhhn.org/sites/default/files/FAQ_on_air_quality_and_health_during_Mauna_Loa_eruption_v1.6.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.

For discussion of Kīlauea hazards, please see: https://www.usgs.gov/observatories/hawaiian-volcano-observatory/hazards.