Activity Summary: The current eruption of Kīlauea volcano has paused this morning.  The large channels and lava falls crusted over between 9 and 10 PM HST last night, September 19. Glow from the vent had decreased significantly by 2:30 AM HST this morning.  Field crews reported minor spattering and small fountains at one end of the vent as of 8:30 AM HST, but this had ended by 10 AM HST.  This is the fourth phase of fissure activity during the current eruption that began on Sunday night, September 15.  The eruption is occurring within a closed and remote area of Hawaiʻi Volcanoes National Park. There is no immediate threat to life or infrastructure. Residents of nearby subdivisions may experience volcanic gas emissions related to this activity which may increase and decrease over the coming hours and days. The Volcano Alert Level/Aviation Color Code remains at WATCH/ORANGE. No changes have been detected in the lower East Rift Zone or Southwest Rift Zone. 

Summit Observations:  Six small, shallow earthquakes were detected beneath the Kīlauea summit region over the past 24 hours. The tiltmeter at Uēkahuna transitioned sharply from deflation to minor inflation yesterday at about 4:15 PM HST. The summit tiltmeter at Sandhill continues to record strong deflation. This pattern suggests that only the deeper, southern summit magma body is continuing to supply magma to the middle East Rift Zone. The most recent measurement of SO₂ emission rate at the summit was 60 tonnes per day on September 17, 2024.   

Rift Zone Observations: The eruptive fissure west of Nāpau Crater diminished greatly overnight.  Beginning around 8 PM HST last night the lava channels and falls began to crust over suggesting diminished lava supply.  All of the open channels completely crusted over between 9 and 10 PM HST last night.  Strong glow from the vent began to diminish around 2:30 AM HST and continued waning until daylight.  Mapping this morning shows that lava flows cover about 2/3 of the floor of Nāpau Crater and aren’t significantly larger than they were yesterday. Field crews reported small fountains and lava flows erupting from one of the earlier western fissures this morning at 8:50 AM HST but had stopped by 10:00 AM HST.  Effusion rates of roughly 5-15 cubic meters per second (6-16 cubic yards) were estimated during the most active part of yesterday’s fissure eruption.  In total, this eruption has covered more than 630,000 square meters (156 acres) of Nāpau Crater and areas to the west since Sunday night. 

Shallow earthquake counts remain very low in the MERZ with about 10 in the past 24 hours. Tremor recorded on the MERZ seismometers close to the eruption site decreased significantly late yesterday and early this morning as eruptive activity died down by 2:30 AM HST.  Tiltmeters in the MERZ continue to show no significant shallow deformation, but GPS instruments continue to show inflation at deeper levels beneath the area between Maunaulu and Nāpau Crater. 

Sulfur Dioxide (SO₂) emission rates measured yesterday, September 19, were 30,000 tonnes per day for the new vent that opened in the afternoon. 

All activity is currently confined to the middle East Rift Zone between Makaopuhi Crater and Puʻuʻōʻō and there are no indications of any changes further downrift in the MERZ or in the LERZ. 

Additional Resources 

• New S2cam, viewing the eruption from the east: https://www.usgs.gov/observatories/hvo/s2cam-view-napau-crater-east-rift-zone-kilauea-view-southwest 
• Webpage with eruption-related resources: Eruption on Kīlauea middle East Rift Zone | U.S. Geological Survey (usgs.gov) 
• Rapidly updated eruption monitoring map showing lava flow coverage and vent locations is available on the HVO home page: www.usgs.gov/hvo  
• Mapping data and a fully zoomable version of eruption monitoring map are available here: USGS Hawaii eruption map - preliminary (arcgis.com) 

Analysis: The fourth phase of activity in ongoing MERZ eruption appears to be over. Tremor remains low indicating eruptive activity is minimal at this time.  Each eruption has increased in volume compared to the prior eruption so far in this sequence.  Additional eruptions, if there are any, might continue to increase in size as well.  Multi-day fissure eruptions are not unusual and current eruptive activity appears to be linked to the continuing supply of magma from the summit.  

Updates: HVO is continuing to closely monitor the middle East Rift Zone and is in contact with Hawai‘i Volcanoes National Park and the Hawai‘i County Civil Defense Agency. Please see the Hawaiʻi Volcanoes National Park website for visitor information: https://www.nps.gov/havo/index.htm. HVO will continue to provide daily updates for Kīlauea volcano. Should volcanic activity change significantly, a Volcanic Activity Notice will be issued.  

Hazards: High level of volcanic gas—primarily water vapor (H₂O), and sulfur dioxide (SO₂)—are emitted during eruptions and can have far-reaching effects downwind. As SO₂ is released from lava, it reacts in the atmosphere to create the visible haze known as vog (volcanic smog) that has been observed downwind of eruptive vents. Vog creates the potential for airborne health hazards to residents and visitors, damages agricultural crops and other plants, and affects livestock. For more information on gas hazards at the summit of Kīlauea, please see: https://pubs.er.usgs.gov/publication/fs20173017. Vog information can be found at https://vog.ivhhn.org.    

Shallow magma movement and eruptions can produce minor to severe ground fractures and subsidence features, which can affect the landscape, human activity, and infrastructure. These ground cracks can continue to widen and offset as magma migration continues, may have unstable overhanging edges, and should be avoided.  

Additional ground cracking and outbreaks of lava around the active fissures are possible at any time, or existing fissures can be reactivated. Hawaiian lava flows generally advance slowly downslope and can be avoided by people. They can destroy everything in their paths including vegetation and infrastructure—which can cut off road access and utilities. Hazards associated with active or recent lava flows include hot and glassy (sharp) surfaces that can cause serious burns, abrasions, and lacerations upon contact with unprotected or exposed skin; uneven and rough terrain can lead to falls and other injuries; hot temperatures that can cause heat exhaustion or dehydration, or in heavy rain can produce steamy ground-fog that can be acidic, severely limiting visibility and sometimes causing difficulty breathing.   

If new lava flows cover and burn vegetation and soil, they can ignite natural gas pockets in the subsurface, which can cause methane explosions. These explosions can blast lava fragments up to several meters (yards) away and can be hazardous to observers. 

Pele's hair and other lightweight volcanic glass fragments from lava fountains and spattering will fall downwind, dusting the ground within a few hundred meters (yards) of the vent. High winds may waft lighter particles and transport them greater distances downwind. Exposure to these volcanic particles can cause skin and eye irritation. 

Hazards 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 the rim surrounding Halemaʻumaʻu crater, an area that has been closed to the public since early 2008.  

For discussion of Kīlauea hazards, please see: https://www.usgs.gov/observatories/hawaiian-volcano-observatory/hazards.