USGS: “A broader view of the activity at Kīlauea summit. The lava fountaining has produced a large pyroclastic cone against the western wall, with deposits draped on the walls. Lava pours out of the vents into a large ponded area in the southwest portion of Halema‘uma‘u crater. A chunk of the cone has been rafted out in the lava stream towards the east, and is visible in the lower right portion of the photo. The broad Northeast Rift Zone of Mauna Loa is visible along the top of the image.” (USGS photo by M. Patrick)

(BIVN) – The eruption of Kīlauea continues on Hawaiʻi island, and the USGS Volcano Alert Level remains at WATCH.

Eruptive activity has been confined to Halemaʻumaʻu and the down-dropped block within the caldera. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

Scientists and affiliates of the USGS Hawaiian Volcano Observatory write about the latest eruption in this week’s Volcano Watch article:

People around the world greet the New Year with fireworks and other celebrations. This year, Hawaiʻi Volcanoes National Park visitors greeted the New Year with displays of lava fountaining from the southwest part of Kaluapele, the summit caldera of Kīlauea volcano.

The eruption is currently in its third episode, with pauses and resumptions of eruptive activity correlating with the level of pressurization within the magma chambers beneath the summit region of Kīlauea. Two important instruments for monitoring the level of pressurization are the UWD and SDH tiltmeters, which measure how the ground is tilting as magma chambers beneath the summit inflate or deflate.

Magma chambers beneath Kīlauea summit region showed increasing pressurization in the months leading up to the current eruption. Fountains of lava burst from the floor of Halemaʻumaʻu at 2:20 a.m. HST on December 23, rapidly reaching heights up to nearly 300 feet (91 meters). These vigorous lava fountains fed lava flows that covered most of the floor of Halemaʻumaʻu crater within Kaluapele that dropped during the 2018 caldera collapse, referred to informally as the “downdropped block.”

Lava being erupted on the surface rapidly relieved some of the pressure that had built up in the magma storage areas below Kīlauea summit. The summit tiltmeters showed strong deflationary tilt immediately after the eruption began, until about 4 p.m. on December 23, when the lava fountains ceased erupting. At this point, lava began flowing back into the vent, in a phenomenon called “drainback,” and tilting direction at UWE and SDH switched to inflationary. This indicated that pressure was again building in the magma chambers beneath Kīlauea summit.

Graph of tilting at the summit of Kīlauea recorded by the UWD tiltmeter, located near Uēkahuna bluff on the north side of the caldera and the SDH tiltmeter located south of the caldera. An increase at these tiltmeter orientations indicates tilting away from the caldera, which is consistent with inflation of the Halemaʻumaʻu magma chamber. While a decrease at these tiltmeter orientations indicates ground tilt towards the caldera, which is consistent with Halemaʻumaʻu magma chamber deflation. The duration of episodes 1, 2, and 3 of eruptive activity between December 23, 2024, and January 2, 2025, are shown in the highlighted areas. USGS plot.

Inflationary tilt continued overnight, and lava began slowly erupting again around 8 a.m. HST on Christmas Eve, December 24. At about 11 a.m. HST, lava fountaining resumed and tiltmeters once again began measuring rapid deflationary tilt during this second episode of the eruption, which continued for the next 24 hours. Lava flows again covered most of the lower elevation southwest portion of Kaluapele floor and the eruption abruptly stopped again around 11 a.m. on Christmas Day, December 25.

Just as they did during the earlier pause, summit tiltmeters began measuring inflationary tilt, indicating that pressure was again accumulating in the magma chambers. Inflation continued through the following night until the eruption resumed at 8 a.m. HST on December 26. Slow lava flows remained close to the vent until the evening of December 27, when low-level lava fountaining resumed. Lava fountaining gradually increased in vigor as slow inflation continued until the afternoon of December 29. Since then, Kīlauea summit tiltmeters have continued to measure deflationary tilt with lava fountaining feeding lava flows in the southwest portion of Halemaʻumaʻu.

This interplay of eruption episodes and variations in magma chamber pressure leads to lots of questions. Most of all: “Why has the eruption been stopping and starting so dramatically?” The association of drainback with magma chamber inflation is puzzling; one would expect increased eruption rate if pressure is increasing.

The answer may lie in the gas content of lava and extent to which gas bubbles also drive eruption. Like releasing the cap off a soda, opening a eruptive vent can result in a combination of pressure- and bubble-driven flow. Erupted lava that “drains back” into the vent is much denser than the fresh gas-rich lava. The drainback lava forms a plug, like putting a cork back into a champagne bottle, that allows the magma chamber to repressurize. The dense lava is slowly pushed out at the beginning of the next episode until new, gas-rich lava gets close enough to the surface to vesiculate and restart fountaining.

The third episode of the eruption is ongoing as of this writing. The USGS Hawaiian Volcano Observatory (HVO) continues to closely monitor the activity, and views of the activity are available on HVO webcams, including a livestream camera.

The recent eruption is a reminder that in Hawaii we live on the flanks of volcanoes, some of which are active. Volcano Awareness Month is a great opportunity for you to increase your knowledge of volcanic activity in Hawaii—join us at one of the many events being offered on the Island of Hawaiʻi throughout the month of January and don’t forget to submit your art or poetry to our contest! Learn more here (USGS.gov)