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HVO/USGS Volcanic Activity Notice

Volcano: Kilauea (VNUM #332010)

Current Volcano Alert Level: WATCH
Current Aviation Color Code: ORANGE

Issued: Tuesday, September 2, 2025, 8:15 PM HST
Source: Hawaiian Volcano Observatory
Notice Number: 2025/H380
Location: N 19 deg 25 min W 155 deg 17 min
Elevation: 4091 ft (1247 m)
Area: Hawaii

Volcanic Activity Summary:

Episode 32 of the ongoing Halemaʻumaʻu eruption ended abruptly at 8:01 p.m. HST on September 2 after 13.4 hours of continuous fountaining.

The north vent stopped erupting at approximately 7:49 p.m. HST. The smaller middle and south vents stopped erupting at approximately 8:01 p.m. HST with a few minutes of jetting, marking the end of episode 32. Lava fountains reached up to 500 ft (150 m) during this episode and averaged more than 250 cubic yards per sec (>200 cubic meters per sec) and produced over 12.5 million cubic yards (9.6 million cubic meters) of lava, the highest output for a short-lived fountain episode. 

Volcanic gas emissions have greatly decreased at the end of the eruption but were probably well in excess of 50,000 tonnes of SO2 per day during the vigorous fountaining. 

Lava flows from this episode covered 40-50% of 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. 

The Uēkahuna tiltmeter (UWD) recorded about 25 microradians of deflationary tilt during this episode. The end of the eruption was coincident with a rapid change from deflation to inflation at the summit and a decrease in seismic tremor intensity.  

More details about the start of this episode can be found in:

The Daily Update for Kīlauea:

USGS Volcano Notice - DOI-USGS-HVO-2025-09-02T18:45:21+00:00

The VOLCANO ACTIVITY NOTICE released this morning at the onset of episode 32:

https://volcanoes.usgs.gov/hans-public/notice/DOI-USGS-HVO-2025-09-02T16:14:39+00:00

The Status Report released early this morning as activity increased prior to the onset of Episode 32 fountains.

USGS Volcano Notice - DOI-USGS-HVO-2025-09-02T13:46:35+00:00

Most episodes of Halemaʻumaʻu lava fountaining since the eruption started on December 23, 2024, have continued for around a day or less and have been separated by pauses in eruptive activity lasting generally at least several days. 

No changes have been detected in the East Rift Zone or Southwest Rift Zone. 

Kīlauea Volcano Alert Level/Aviation Color Code remain at WATCH/ORANGE. All current and recent activity is within Hawaiʻi Volcanoes National Park.

Recent Observations:
[Volcanic cloud height] Maximum height of the convective plume observed was about 10,000 feet above ground level. Extensive clouds precluded observation of plume height later in eruption.
[Other volcanic cloud information] Sulfur dioxide emission rate is typically 1,200-1,500 tonnes/day between eruptive episodes
[Ballistics] N/A
[Lava flow/dome] N/A
[Lava flow] N/A

Hazard Analysis:
[General hazards] Pele's hair and tephra may affect areas downwind of eruptive vents.
[Ash cloud] N/A
[Ashfall] N/A
[Lava flow/dome] N/A
[Pyroclastic flow] N/A
[Mud flow] N/A
[Volcanic gas] Usually 1,200-1,500 tonnes/day SO2 between eruptive episodes.
[Lava flow] May continue to exhibit slow movement or incandescence as the cool and solidify over the coming days.

Remarks:

Hazard Analysis: 

This episodic eruption is occurring within a closed area of Hawai'i Volcanoes National Park. High levels of volcanic gas—primarily water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2)—are one 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/

Another hazard closer to the vent is fallout of Pele's hair and other volcanic fragments from lava fountains. Pele's hair is strands of volcanic glass often produced by lava fountaining activity and can be carried well over 10 miles (15 kilometers) from the vent. Other hot glassy volcanic fragments including Peleʻs hair, volcanic ash, pumice, scoria, and reticulite can fall on the ground within 1-2 miles (1-3 kilometers) of the eruptive vent(s) with the highest concentrations downwind of the vent(s). Pumice and other volcanic fragments have fallen on Highway 11 west of Hawaiʻi Volcanoes National Park depending on wind and eruption conditions.  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 glassy 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 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.



Contacts:

askHVO@usgs.gov



Next Notice:

HVO continues to closely monitor Kīlauea and will issue a VAN/VONA at the start of the next eruptive episode. If possible, HVO will also issue a Status Report beforehand at the onset of low-level precursory activity.  Regularly scheduled daily updates for Kīlauea are posted on the HVO website at https://www.usgs.gov/volcanoes/kilauea/volcano-updates  

More Information:



Subscribe to these messages: https://volcanoes.usgs.gov/vns2/
Summary of volcanic hazards from eruptions: https://www.usgs.gov/observatories/hvo/hazards
Recent earthquakes in Hawaiʻi (map and list): https://www.usgs.gov/observatories/hvo
Explanation of Volcano Alert Levels and Aviation Color Codes: https://www.usgs.gov/programs/VHP/volcanic-alert-levels-characterize-conditions-us-volcanoes