(BIVN) – The shallow intrusion of magma that occurred overnight at the Kīlauea summit region appears to be over, for now, as low level eruptive activity continues within Halemaʻmumaʻu.
“At this stage, it appears that intrusive activity is complete,” the USGS Hawaiian Volcano Observatory stated on Thursday, “although conditions can change rapidly including eruption from a new vent with little or no seismicity or deformation.”
The north and south vents at the summit caldera continue to have intermittent overflows, spatter, and strong glow. The Observatory says there is no anomalous activity outside of the summit.
The Observatory issued a status report overnight, describing the shallow intrusion of magma with an east-west orientation. The intrusive activity was strongest between 8 p.m. Wednesday night (September 30) and Thursday morning around 3 a.m. HST.
“The intrusive activity was recorded by large rapid displacements on the summit tiltmeters, increased earthquake activity in summit region, and increased tremor,” the Observatory said. “There is no evidence that magma associated with this intrusion erupted in a new location.”
Due to increased volcanic unrest, Hawaiʻi Volcanoes National Park temporarily closed the Keanakākoʻi area for safety. This includes old Crater Rim Drive, the overlooks near Keanakākoʻi crater and Crater Rim Trail to Keanakākoʻi. Devastation parking lot remains open.
From the USGS HVO activity update issued on Thursday:
Summit Observations:
Overflows from the north vent resumed on the evening of September 22 after about 10 days of quiescence at the vent complex. Overflow activity from the south vent began on September 27. However, the north vent remained dominant until the evening of September 28, when south vent started having short, rapid cycles of overflows and lava drainback that continued through yesterday afternoon. These south vent overflows lasted about 2–5 minutes, with most pauses between each cycle lasting about 5–7 minutes; there were over 100 such overflows. Since September 29, the frequency of overflow activity has greatly decreased, although intermittent overflows continue at both north and south vents. Since yesterday September 30, north vent has had several overflows with minor dome fountaining. Eruptions from the north and south vents stopped during the early stages of dike emplaced yesterday afternoon, but the north vent resumed later during continued intrusive activity. The south vent had at least one overflow this morning after intrusive activity quieted down. In total, there were at least 10 overflows during and after the main intrusive event. Both north and south vents also spattered overnight and had persistent strong glow, and west vent had occasional glow. No other areas of incandescence were observed across the summit region last night.
Increased earthquake activity began yesterday, September 30, 2026, at approximately 2 p.m. HST, underneath Halemaʻumaʻu. In the past 24 hours, there were 98 shallow earthquakes located across the summit region, primarily underneath Halemaʻumaʻu, the largest of which was a magnitude (M) 3.4 earthquake at 9:52 p.m. H.S.T. Starting around 8 p.m. HST., summit tiltmeters began to show extremely rapid changes consistent with crack growth in an east-west orientation near the current vent area, suggesting that magma was intruding in this region. Most of the seismicity was confined to the western part of Halemaʻumaʻu and the northwestern part of Kaluapele, the summit caldera. Between 8 p.m. H.S.T. last night and 3 a.m. this morning, Uēkahuna tiltmeter (UWD) recorded approximately 38.5 microradians of inflation (this value has been corrected for a spike in the signal caused by the M3.4 earthquake). Since 3 a.m. H.S.T. this morning, summit inflation has flattened out and earthquake activity has decreased. A comparison of webcam imagery before and after the intrusion does not show any new ground cracking or eruption of lava in a new location.
During inter-episode pauses, the sulfur dioxide (SO2) emission rate from the summit typically varies between 1,000 and 5,000 tonnes per day. Winds are currently forecast from the southeast.
Rift Zone Observations:
Rates of seismicity and ground deformation remain low in the East Rift Zone and Southwest Rift Zone. SO2 emissions from the East Rift Zone remain below the detection limit. No significant ground deformation was recorded in either rift zone.
Analysis:
Monitoring data indicate that a shallow intrusion occurred overnight underneath Halemaʻumaʻu. Intrusive activity was strongest between 8 p.m. H.S.T. last night (September 30, 2026) and this morning around 3 a.m. H.S.T. Throughout the intrusion, eruptive activity similar to that observed since September 28 continued at north and south vents. At this stage, it appears that intrusive activity is complete, although conditions can change rapidly including eruption from a new vent with little or no seismicity or deformation.
The north vent resumed overflow activity on September 22. The south vent resumed overflow activity on September 27. The north and south vents continued to have intermittent overflows and spatter, strong glow and emitted flames overnight. Forecast windows for a potential episode 55 can no longer be modeled due to the irregular changes in inflation and deflation. The north vent has produced the last 11 high fountain events (episodes 44–54). It is not possible to say with certainty that this activity will lead to the onset of another fountain event at this time, although conditions remain favorable.
Because the summit system remains active and highly pressurized, the two most likely possibilities are that activity continues at the north-south-west vent complex, or it activates another existing weak crack system in the summit region. Neither of these events are likely to produce a strong seismic precursor, so the alert levels have been left at ORANGE/WATCH as the volcano continues to “exhibit heightened unrest with an increased potential for eruption”.
