Activity Summary:  

Episode 18 precursory activity began on the evening of April 16, 2025, with spattering bursts every 10–20 seconds from the north vent starting at 9:10 p.m. HST and strong glow from the south vent. Lava began overflowing from the north vent around 10:01 p.m. HST on April 16 marking the start of episode 18; lava flows made it about a hundred meters (several hundred feet) from the north vent before this activity ended at approximately 11:21 p.m. HST. The main lava fountaining phase of episode 18 is most likely to start sometime between today and this weekend, with the possibility of more lava flows preceding the fountaining phase.

Kīlauea's current eruption in Halemaʻumaʻu crater within Kaluapele (the summit caldera) began on December 23, 2024. There have now been 18 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:

The south and north vents had significant glow for most of last night, along with north vent minor spattering and vent overflows. Strong degassing is currently occurring from both vents.

Low level activity began around 9:10 p.m. HST on April 16, with bursts of spatter every 10-20 seconds from the north vent, reaching up to a few meters (several feet) high. Spatter bursts continued to increase in size and frequency until about 9:30 p.m. HST when 10-15 foot high (3-5 meters high) dome fountains began. Lava overflowed from the north vent around 10:01 p.m. HST and fed a small lava flow that reached about 100 meters (a few hundred feet) from the vent. This activity ended abruptly at 11:21 p.m. HST. Glow from south vent disappeared when north vent had overflows but returned once north vent flows ceased. This is considered precursory activity to the main fountaining phase of episode 18 and there could be more lava flows preceding the fountaining phase.

The UWD and SDH tiltmeters continue to show an inflationary signal that has been persistent since the end of episode 17. The main fountaining phase of episode 18 is not expected to begin until deflation starts at the UWD and SDH tiltmeters. As of this morning, UWD has measured more than 11 microradians of inflationary tilt since 9:45 a.m. HST April 9. Seismic tremor rapidly increased in intensity on April 16 with the north vent spattering and lava overflows but has since dropped to pre-overflow levels. Cyclic tremor patterns with 30-60 minute periods began at this time and continue to the present. These tremor patterns are reminiscent of cyclic patterns due to gas pistoning seen prior to episodes 14 and 15 but are longer period.

Volcanic gas emissions remain elevated and at heightened levels due to lava fountaining. The last sulfur dioxide (SO₂) emission rate measured on April 10 was approximately 1,200 tonnes per day. Typical levels of Sulfur dioxide (SO₂) emission have been about 1,000 tonnes per day during previous pauses. This morning, the plume is being carried towards the south to southwest.

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.

• 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 

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 detection limit.

Analysis: 

The current eruption has been characterized by episodic fountaining not seen in any of the other Halemaʻumaʻu eruptions since 2020. Fountains and lava flows have erupted from two vents that we refer to as the north vent and south vent. Each of the previous 17 fountaining episodes lasted from a few hours to over a week and has 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.

Analysis of inflationary tilt patterns prior to the onset of each fountaining episode allows a time window of probability for the onset of new episodes to be estimated. These are calculated using both minimum inflation necessary to start a new eruption and the rate of inflation fit to data derived from past eruptive episodes. The precursory activity of episode 18 occurred as forecast, although deflation and the onset of the main phase of fountaining has yet to start for episode 18. This main fountaining phase could start today to sometime over the weekend, with the possibilities of more lava flows preceding the fountaining phase. This window may be adjusted if inflation rates change significantly. Based upon prior cycles of fountaining and deflation, episode 18 fountaining is likely to be less than 24 hours long.

• Timeline of eruptive episodes since December 23, 2024: https://www.usgs.gov/volcanoes/kilauea/science/eruption-information
• Summit eruption reference map: January 15, 2025—Kīlauea summit eruption reference map | U.S. Geological Survey
• 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.

General Updates: 

The power system that supplies power to the KWcam webcam, the F1cam thermal camera, and the laser rangefinder sustained damage during the high fountaining on March 26, 2025. Both cameras and the rangefinder are currently offline. Other HVO webcams are still functioning and online.

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, 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.