Episode 23 precursory activity continues but summit inflation has slowed significantly. Sustained fountaining is likely to start between today and Sunday. The notable decrease in the rate of summit inflation has likely delayed the onset of sustained fountaining compared to previous episodes.
Kīlauea's current eruption in Halemaʻumaʻu crater within Kaluapele (the summit caldera) began on December 23, 2024. There have now been 22 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:
Strong glow and intermittent spatter was visible in both vents overnight with occasional flames seen in the north vent. This is similar to activity seen in the lead up to previous sustained fountaining episodes. Precursory activity is expected to increase further before the onset of sustained fountains.
The rate of summit inflation has slowed significantly, with tiltmeters at Uēkahuna (UWD) and Sandhill (SDH) recording net zero inflation since Wednesday. Small variations in summit tilt rates are not uncommon, but this represents a departure from previous inter-episode trends. Total inflationary tilt recorded at UWD is approximately 9 microradians since the end of episode 22 on May 16. Low level tremor continues beneath Halemaʻumaʻu crater.
The average sulfur dioxide (SO) emission rate remains around 1,200 tonnes per day (t/d), similar to rates recorded during prior pauses.
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.
An HVO field crew will be adjusting the V3 streaming cam today; there could be short interruptions in the video stream during this work. 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 (SO) 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 within Halema'um'a'u 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 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.
Episode 22 ended on May 16. The rapid rebound of tilt at the end of episode 22 from deflation to inflation, along with persistent strong glow from the vents, indicates that magma remains shallow in both the north and south conduits. Based on current rates of inflation, episode 23 is likely to begin in the next 1-3 days, between today and Sunday. This estimate will be refined as more data become available.
The notable decrease in the rate of summit inflation has likely delayed the onset of sustained fountaining compared to previous episodes. UWD recorded a less significant slowing of inflation prior to episode 15, but SDH did not, whereas the current reduction in summit inflation is being recorded by both UWD and SDH as well as IKI. Time will tell if this is a temporary variation in precursory activity or a possible change in the current eruption.
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 (HO), carbon dioxide (CO), and sulfur dioxide (SO) -- are the primary hazard of concern, as this hazard can have far-reaching effects downwind. As SO 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. SO 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.