Kilauea has been erupting -episodically for the past two months in Halema'uma'u, nested within the south end of Kaluapele, the summit caldera. Captivating lava fountains burst from the vent(s) during each eruption episode. Fascinating as those episodes are, scientists at the USGS Hawaiian Volcano Observatory are equally as interested in what's happening beneath the surface between episodes.
Ten lava fountaining episodes have taken place in Halema'uma'u since Dec. 23, 2024, from two vents: the north vent and the south vent. Most fountaining episodes have been active for less than a day (16 hours on average), though a couple were longer duration (up to 8 days).
HVO staff rely on several key monitoring datasets to track the status of Kilauea using a network of instruments across the volcano. A variety of seismoacoustic instruments record earthquakes and other ground vibrations, as well as low-frequency sound. Gas sensors sniff the volcanic gas emissions in areas downwind. Webcams, including the livestream camera, provide near real-time visual and thermal views. Ground deformation is documented using GPS units and tiltmeters. Together, these datasets can be used by scientists to analyze the processes occurring within Kilauea.
In between each lava fountaining episode, monitoring datasets, like tilt, seismicity, and gas emissions, have shown similar behaviors. This repeating nature of activity has allowed HVO scientists to identify patterns that can be used to estimate windows of probability for future eruptive episodes in Halema'uma'u.
When lava fountains are erupting in Halema'uma'u, ground deformation instruments -- tiltmeters, in particular -- show deflation as magma that was stored in the volcano is erupted on the surface. In between lava fountaining episodes, those sensors show inflation as magma again accumulates beneath the surface and repressurizes the magma chambers. The amount of repressurization required for a new episode to start has ranged from 2-10 microradians, taking anywhere from a day to nearly two weeks. This range of repressurization is what informs HVO's probability estimates for when a new episode most likely will begin. The rate of inflation can vary, though, which causes the probability window for the start of the next episode to be shifted in time.
While deformation shows us how magma is behaving underground between episodes, we also have data telling us that surface activity continues even while fountaining is paused. During episodes of lava fountaining, the rumblings of magma making its way out of the conduit produce an intense tremor signal seen on seismic stations across Kilauea. The tremor rumbles at lower frequencies, caused by rapid expansion and contraction of magma within the vents. These continuous vibrations result from the formation and release of gas bubbles that drive the fountains high into the air.
Yet even between eruptive episodes, tremor has remained present. The intensity drops significantly between episodes but continues to exist until the next episode. This indicates that gas is continuing to be released by the vents and magma continues to stir near surface even when lava is not visibly erupting. As the weak tremor churns in the background, other seismic signals are also observable. Low frequency signals that range in size are seen on the seismic network around the summit area and suggest complex patterns of magma migration, bubble formation, and transport within the volcano.
The observation of continuing tremor between episodes is corroborated by volcanic gas measurements and persisting glow at the vents. When an episode of lava fountaining is occurring, sulfur dioxide (SO2) emission rates are highly elevated, in the range of 10,000 tonnes per day (t/d). Even when lava is not actively fountaining, SO2 emission rates have remained moderately elevated, in the range of 1,000 t/d. If Kilauea were truly quiet, we would expect only about 100 t/d of SO2. Likewise, in between eruptive episodes, glow remains visible at night at the north, and sometimes south, vent. This incandescence is another clue that magma is just beneath the surface, continuing to gurgle, glow, and degas.
New episodes of lava fountaining have been brief and impressive, but the build up to them is an exciting glimpse into how Kilauea volcano works. If you happen to visit Kilauea in between Halema'uma'u lava fountaining episodes, know that the degassing and glow are evidence of the continuous activity that is happening, hidden just beneath the surface.
Volcano activity updates
Kilauea has been erupting intermittently within the summit caldera since Dec. 23, 2024. Its USGS Volcano Alert level is WATCH.
The summit eruption at Kilauea volcano that began in Halema'uma'u crater on Dec. 23 continued over the past week, with one eruptive episode. Episode 10 was active from the night of February 19 until the morning of February 20. Kilauea summit has been inflating since episode 10 ended, suggesting that another eruptive episode is possible. Sulfur dioxide emission rates are elevated in the summit region during active eruption episodes. No unusual activity has been noted along Kilauea's East Rift Zone or Southwest Rift Zone.
Mauna Loa is not erupting. Its USGS Volcano Alert Level is at NORMAL.
Three earthquakes were reported felt in the Hawaiian Islands during the past week: a M3.5 earthquake 15 km (9 mi) ESE of Na'alehu at 36 km (22 mi) depth on Feb. 18 at 6:10 p.m. HST, a M3.8 earthquake 18 km (11 mi) ESE of Na'alehu at 34 km (21 mi) depth on Feb. 14 at 5:04 a.m. HST, and a M3.1 earthquake 8 km (4 mi) S of Kapa'au at 23 km (14 mi) depth on Feb. 13 at 6:31 a.m. HST.
Please visit HVO's website for past Volcano Watch articles, Kilauea and Mauna Loa updates, volcano photos, maps, recent earthquake information, and more. Email questions to [email protected].