Activity Summary:

Episode 28 of the ongoing Halemaʻumaʻu eruption ended just before 1:30 p.m. HST yesterday, July 9, 2025, after 9 hours of sustained lava fountaining. Summit inflation has resumed, and low-level degassing and seismic tremor persist.

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:

Following days of low-level gas pistoning and occasionally visible spatter and flames, activity at the north vent began to increase just after 4 a.m. HST yesterday (July 9, 2025) with a larger lava overflow, continuous low-level fountaining, weak deflation, and an increase in seismic tremor. An hour later, fountaining increased in height and vigor; at the same time, tilt began to drop sharply. High fountaining with maximum heights near 1,200 feet (365 meters) continued for roughly 8 hours, for a total of 9 hours of fountaining activity. All activity associated with Episode 28 was focused at the north eruptive vent; the south vent did not reactivate during the episode and appears to have been completely buried by the deposits erupted from north vent. Deposits from the episode have also nearly connected the growing eruptive cone with the top of the surrounding cliff in some places.

At present, tremor and degassing persist at lower but still elevated levels. Typical sulfur dioxide (SO₂) emission rates associated with pause periods are 1,200 to 1,500 t/d. Lava flows on the floor of Halemaʻumaʻu within the southern part of Kaluapele (Kīlauea caldera) may continue to exhibit slow movement or incandescence as they cool and solidify over the coming days, and additional new ooze-out lava flows have been observed at the edges of older flows. Slumping of the eruptive cone around the vent may also continue to expose incandescent material over the next hours to days.

At the time of the onset of Episode 28, the tiltmeter near Uēkahuna (UWD) had recorded about 14 microradians of inflationary tilt since the end of episode 27. Fountaining associated with Episode 28 resulted in 15 microradians of deflation. At the time of this update, UWD had re-inflated by nearly 3 microradians.

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. Trade winds are forecast for today and would likely blow both volcanic gases and erupted particles (tephra, ash, and Pele’s hair) to the west and southwest of Kīlauea summit.

• 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: 

Summit inflation has resumed, and low-level degassing and seismic tremor persist, all of which suggest that another episode of fountaining is likely. Additional time is needed to accumulate tiltmeter data before a specific forecast window can be made for episode 29. In the next few days, as post-episode data comes in, we will likely be able to begin to forecast a possible window for the next episode.

However, given that the deflationary tilt during the past several episodes was similar, we would expect a roughly similar pause duration following episode 28. The pauses between the past several recent episodes have ranged from 6 to 10 days.

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 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 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.

General Updates: 

Tilt azimuths for SDH and UWD tiltmeter plots, as displayed on USGS websites, have been updated to optimize showing maximum magnitudes of deformation consistent with the current activity at the summit of Kilauea.

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_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.