Activity Summary:

Episode 21 ended at 08:36 p.m. HST on Sunday, May 11, 2025, after 7 hours and 51 minutes of sustained fountaining from the north vent. The Halema'uma'u eruption is currently paused. Episode 22 is likely to begin in the next 2-3 days.

Both the north and south vents were incandescent last night but overnight glow from the episode 21 lava flows are greatly diminished.

Kīlauea's current eruption in Halemaʻumaʻu crater within Kaluapele (the summit caldera) began on December 23, 2024. There have now been 21 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:

Fountaining from the north vent began at 12:45 p.m. HST and fountains rapidly escalated from 30 feet (10 meters) to over 500 feet (150 meters) high within the first hour.  During this time, seismic tremor also increased.  From about 2:00 p.m. to 4:00 p.m. HST on May 11, fountains cycled from 200 feet to 500 feet (60 to 120 meters) high over about 10-minute intervals, which are also recorded as oscillations in tremor.  Maximum fountain heights reached over 650 feet (200 meters).  After 4 p.m. HST on May 11, fountains from the north vent were more consistent in height and averaged around 400 feet (120 meters) high until they ended at 8:34 p.m. HST.  Minor fountaining (less than 50 feet or 15 meters high) from the south vent began just prior to this and lasted until 8:36 p.m. HST on May 11, marking the end to episode 21.  This late fountaining was the only activity observed from the south vent during episode 21.  Lava flows from episode 21 covered about 50% of the floor of Halema'uma'u crater. 

Orange glow was visible overnight from both vents, and intermittent spatter was observed from the north vent in the evening on May 14, indicating that magma remains close to the surface within the conduits. 

The tiltmeter at Uēkahuna (UWD) recorded just under 8 microradians of deflation during episode 21 fountaining.  Tilt changed from deflation to inflation at 8:36 p.m. HST when lava stopped erupting from the south vent; tremor also declined rapidly at this time.  This morning, tilt at UWD has recorded approximately 5.6 microradians of inflationary tilt since the end of episode 21. Low level tremor continues along with a small number of shallow earthquakes.

Sulfur dioxide (SO₂) emission rates are expected to be similar to rates recorded during prior pauses around 1,200 tonnes per day (t/d).

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 due to eruption impacts. 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 21 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 21 along with strong glow and intermittent spatter overnight indicates that magma remains shallow in both the north and south conduits. Data indicate that episode 22 is likely to occur between Saturday and Sunday or in the next 2-3 days, with a small chance of being delayed until Monday if the inflation rate slows substantially. 

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 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.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.