Kilauea's Year-Long Episodic Eruption Sequence Concludes with 39th Event

The sustained, episodic eruptive sequence at Kīlauea volcano's summit formally concluded on December 24, 2025, with the abrupt cessation of Episode 39 within the Halemaʻumaʻu crater. This final documented event commenced late on December 23, 2025, and persisted for approximately 5.9 hours before activity ceased at 2:13 a.m. HST on the 24th, according to confirmation from the Hawaiian Volcano Observatory (HVO).

The conclusion of the eruption was signaled by the north vent stopping activity around 2:00 a.m., followed shortly by the south vent, coinciding with a notable decrease in seismic tremor intensity and a rapid transition from summit deflation to inflation. The sequence itself, which began exactly one year prior on December 23, 2024, is characterized by repeated, intense lava fountaining episodes separated by inter-eruptive pauses lasting between one and three weeks. This style of activity is uncommon for Kīlauea, not having been observed in nearly 40 years, with only three other documented precedents, including the 1959 Kīlauea Iki event.

Episode 39 featured dramatic lava fountains originating from the south vent, which reached peak heights of 1,400 feet (420 meters), while the north vent fountains ascended to just under 1,000 feet (280 meters) around 9:30 p.m. HST on December 23. This 39th fountaining event generated an estimated 13 million cubic yards, equivalent to 10 million cubic meters, of molten material, with the combined average eruption rate exceeding 250 cubic yards per second. The resulting lava flows extensively covered an estimated 60% to 70% of the floor within Halemaʻumaʻu crater, which is situated within Kaluapele, the Kīlauea caldera.

Throughout this year-long phase, the U.S. Geological Survey (USGS) maintained the Volcano Alert Level at WATCH, with the Aviation Color Code consistently set to ORANGE, reflecting that all current activity remained confined to the summit caldera within Hawaiʻi Volcanoes National Park. Hazards during these high fountaining events included the deposition of Pele's hair and tephra, though most material landed within closed areas of the park southwest of the vents. The Uēkahuna tiltmeter (UWD) recorded approximately 26.3 microradians of deflationary tilt during the episode, a metric closely tracked by HVO scientists monitoring subsurface magma movement.

The entire sequence, spanning from December 23, 2024, to December 24, 2025, has significantly reshaped the summit landscape. This includes the construction of a new Puʻu (hill) 42 meters tall on the northwest rim and a total raising of the caldera floor by 223 feet (68 meters). While the eruption has paused, HVO noted that residual lava flows on the crater floor may continue to show slow movement or incandescence as they cool and solidify in the days following the event. The volcano's sustained activity confirms Kīlauea's status as one of the world's most active volcanoes, situated on the Hawaiian–Emperor seamount chain.