HAWAII VOLCANOES NATIONAL PARK, Hawaii — Volcanic activity intensified at the summit of Kīlauea as fresh lava repeatedly overflowed from a vent within Halemaʻumaʻu crater, sending molten rock nearly a half-mile across the crater floor, scientists with the U.S. Geological Survey reported.
Multiple small overflows began late Thursday night at the crater’s south vent, followed early Friday morning by a rapid surge that blanketed ground within 300 feet of the opening in just 10 minutes, according to Big Island Video News. Shortly before 6 a.m. local time, continuous overflows took hold, driven by a small dome fountain inside the vent that fed several streams of pahoehoe lava. Irregular seismic tremor shifted to a steady signal around the same time as drainback events ceased, geologists observed.
Underground Pressures Exceed Typical Levels
The heightened surface activity occurs while the magma reservoir beneath Halemaʻumaʻu remains significantly pressurized. According to the USGS Hawaiian Volcano Observatory, ground deformation instruments show that the reservoir has swollen beyond the levels normally recorded prior to major fountaining events. While episodic fountaining has been a hallmark of Kīlauea since late December 2024, the summit has not seen a full-scale fountaining episode since episode 54 occurred on Aug. 25.
Geologists Heather Winslow and Marco Bagnardi noted in a USGS Volcano Watch report that ground tilt dropped sharply during the August fountaining event but fully recovered by Sept. 7. However, instead of immediately triggering a new fountaining phase, the summit magma system continued to accumulate stress. That pressure eventually forced magma to the surface through six new fissure vents between Sept. 14 and Sept. 16, located just north of the main vent complex.
Laboratory analysis of water-quenched lava samples collected from those mid-September fissures revealed a chemistry matching earlier summit output, containing roughly 6.9 weight percent magnesium oxide, the scientists reported. The low crystal content and chemical signature confirmed that the magma originated from the same shallow reservoir feeding Halemaʻumaʻu rather than a deeper or older source, indicating that high pressure had simply driven magma along preexisting pathways.
Monitoring Risks and Gas Emissions
Summit monitoring stations recorded 21 earthquakes over a 24-hour span, primarily clustered in the southern and eastern parts of the caldera, Big Island Video News reported. GPS instruments positioned across Halemaʻumaʻu have documented a subtle increase in distance between stations since late September, pointing to ongoing, long-term inflation in the shallow magma reservoir.
Despite the active lava and ground swelling, seismic activity and ground deformation along both the East Rift Zone and the Southwest Rift Zone remain low, USGS scientists reported. Sulfur dioxide emissions from the summit have ranged between 1,000 and 5,000 tonnes per day, generating visible gas plumes above the active vents.
The Hawaiian Volcano Observatory maintains the volcano alert level at Watch and the aviation color code at Orange. Geologists cautioned that conditions at the summit remain unpredictable. While another major fountaining phase from the north-south vent system remains possible, magma could instead cause new underground intrusions or quietly seep through existing fracture networks on the caldera floor without advance warning.
