USGS Volcano Notice - DOI-USGS-HVO-2023-09-17T12:12:13-07:00

Activity Summary: The Kīlauea summit eruption that began on September 10th stopped yesterday, September 16th, and is unlikely to restart. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone. 

Summit Eruption Observations: Eruption of lava from the fissure vents on the downdropped block of Kīlauea's summit caldera stopped around noon yesterday, September 16, and there was no observable activity anywhere overnight or this morning.  Yesterday morning, HVO field crews reported that active lava was no longer flowing onto Halemaʻumaʻu crater floor and was restricted to a ponded area north of the vents on the downdropped block. They observed lava spattering at the vents cease at approximately 11:15 am September 16. Overnight webcam views showed some incandescence across the eruption area as lava erupted over the past week continues to cool. Field observations are supported by geophysical data, which show that eruptive tremor (a signal associated with fluid movement) in the summit region decreased over September 15 and 16 and returned to pre-eruption levels by 5 p.m. HST on September 16. Information on the recent Kīlauea summit eruption is available at: https://www.usgs.gov/volcanoes/kilauea/recent-eruption. 

Summit Observations: Summit tilt was mildly inflationary most of the past 24 hours. Summit seismic activity is low with very few volcano tectonic earthquakes and tremor at background levels. Sulfur dioxide (SO2) emissions have also decreased to near background levels based upon the very weak plume visible this morning.  Sulfur dioxide levels were measured at a rate of 800 tonnes per day yesterday, September 16, while the eruption was waning. This value is down dramatically from the 190,000 tonnes per day measured just after the onset of the eruption on Sunday, September 10th, and is only slightly above the 100-200 tonnes typical of non-eruptive periods.

Rift Zone Observations: No unusual activity has been noted along the East Rift Zone or Southwest Rift Zone; steady rates of ground deformation and seismicity continue along both. Measurements from continuous gas monitoring stations downwind of Puʻuʻōʻō in the middle East Rift Zone—the site of 1983–2018 eruptive activity—remain below detection limits for SO₂, indicating that SO₂ emissions from Puʻuʻōʻō are negligible.

Hazard Analysis: Levels of volcanic gas (sulfur dioxide and carbon dioxide) can remain locally hazardous even though Kīlauea is no longer erupting. Sulfur dioxide (SO₂) gas emissions have greatly decreased; however, local concentrations of sulfur dioxide (SO₂) or hydrogen sulfide (H₂S) may persist in downwind areas, and residents may notice odors of these gases occasionally. Significant hazards also remain around Halemaʻumaʻu from crater wall instability, ground cracking, and rockfalls that can be enhanced by earthquakes within the area closed to the public. For discussion of Kīlauea hazards, please see: https://www.usgs.gov/observatories/hawaiian-volcano-observatory/hazards.

The Hawaiian Volcano Observatory (HVO) continues to closely monitor Kīlauea volcano.

Next Notice: HVO will issue daily Kīlauea updates. Additional messages will be issued as needed.