Volcano Watch: Kīlauea’s continuing summit eruption

“Volcano Watch” is a weekly article and activity update written by US Geological Survey Hawaiian Volcano Observatory scientists and affiliates.

The episodic summit eruption of Kīlauea in Halemaʻumaʻu Crater has been going on for more than 3 months now, with 16 eruptive episodes displaying lava fountains and lava flows within Kaluapele, the volcano’s summit caldera.

What clues can observations of sparse episodic eruptions in Kīlauea’s past tell us about the ongoing episodic eruption at Kīlauea summit?

Similar episodic eruptions at Kīlauea took place in 1959 (Kīlauea Iki), 1969 (Maunaulu) and from 1983 to 1986 (first 3 years at Puʻuʻōʻō). An understanding of what happened before and after these similar eruptions — as well as how the eruptions themselves progressed — can inform our understanding of this ongoing summit eruption.

An important consideration is how pressurized the magma chambers beneath Kīlauea summit are.

One tool scientists at US Geological Survey Hawaiian Volcano Observatory use to measure pressurization in magma chambers is tiltmeters, which can detect very small changes in how the ground is tilting around Kīlauea summit.

While tiltmeter technology has changed with time, measurements haven’t. As pressure accumulates (inflation), ground surface bulges outward, and tiltmeters track these subtle changes in ground tilting through time.

Leading to the 1959 summit eruption of Kīlauea Iki, the magma chambers beneath Kīlauea’s summit region were refilling and repressurizing for years following the 1955 lower East Rift Zone eruption.

Following the 1959 eruption, which consisted of 17 high fountains every couple of days throughout about a month, pressure within Kīlauea’s summit magma chambers only increased.

The 12 episodic lava fountains at Maunaulu, on the upper East Rift Zone of Kīlauea in 1969, followed several brief summit and East Rift Zone eruptions preceded by rapid inflation of the magma chambers beneath the summit.

Before those events, Kīlauea summit was in a prolonged lava lake eruption from 1967 to 1968 that was accompanied by little ground deformation.

Similar to during the 2025 eruption, the summit magma chambers deflated during Maunaulu lava fountaining episodes, which happened days to weeks apart, and inflated during pauses.

After the episodic lava fountaining phase of Maunaulu ended, the volcano entered a multi-year phase of lava flows, building a shield and traveling downslope toward the ocean.

Prior to the Puʻuʻōʻō eruption on the middle East Rift Zone of Kīlauea, there were several years of summit eruptions and rift zone intrusions with overall inflation of the summit.

Like the Maunaulu eruption, the phase of 44 lava fountains — occurring about once a month throughout about 3 years — was followed by lava flows building a shield and traveling downslope toward the ocean.

Kīlauea summit deflated with the onset of the Puʻuʻōʻō eruption, and that deflation continued for the next 2 decades as the Puʻuʻōʻō eruption continued.

During the current ongoing eruption, tiltmeters have shown inflationary tilt prior to each lava fountaining episode as pressure builds beneath the surface, and a switch to deflationary tilt when a lava fountain episode begins, indicative of the pressure within the magma chambers being released.

This created a saw-tooth pattern in ground tilt records during the past several months; however, Kīlauea summit has shown little net change in pressurization since the eruption began Dec. 23, 2024, indicating the summit has been in some level of equilibrium.

The north and south eruptive vents in Halemaʻumaʻu are able to incrementally release the pressure that accumulates within Kīlauea summit magma chambers with each eruptive episode.

As long as that equilibrium is maintained, the episodic eruption at the summit is likely to continue.

The ongoing eruption patterns have also allowed Hawaiian Volcano Observatory staff to publish windows of probability for when future eruptive episodes could begin.

However, changes such as a decrease in the rate of inflation or a severe blockage of the vents could alter the current pattern of fountaining episodes, including bringing them to an end.

The volcano observatory will continue to closely monitor the activity, especially the amount of pressurization of Kīlauea’s summit magma chambers, for any changes that could herald a potential change in eruptive activity.

Volcano Activity Updates

Kīlauea has been erupting episodically within the summit caldera since Dec. 23, 2024. Its US Geological Survey Volcano Alert Level is at Watch.

The eruption continued during the past week with Episode 16, which began the evening of March 31 and ended the afternoon of April 2. Lava fountains at one point during the most recent episode exceeded more than 1,000 feet in height, the tallest so far of any during this eruption, and north-northwest winds resulted in tephra and Pele’s hair were deposited on parts of Highway 11 in Kaʻū.

Hawaiian Volcano Observatory reported in its daily Kīlauea update April 3 that strong glow, tremor and a sharp rebound in inflation since the end of Episode 16 suggest another episode is very likely.

Preliminary data suggest the onset of the next episode is most likely to be sometime between April 10-13, or 7 to 10 days from now. A new probability window will be calculated when more data is available.

Sulfur dioxide emission rates are elevated in the summit region during active eruption episodes. No unusual activity has been noted along Kīlauea’s East Rift Zone or Southwest Rift Zone.

Maunaloa is not erupting. Its US Geological Survey Volcano Alert Level is at Normal.

Two earthquakes were reported felt in the Hawaiian Islands during the past week:

• Magnitude-3.3 located 12 miles south-southeast of Hōnaunau-Nāpōʻopoʻo at a depth of 5 miles at 4:25 a.m. March 30.
• Magnitude-3 located 13 miles south-southeast of Fern Forest at a depth of 26 miles at 11:45 p.m. March 28.

Hawaiian Volcano Observatory continues to closely monitor Kīlauea and Maunaloa.

Visit the volcano observatory website for past “Volcano Watch” articles, Kīlauea and Maunaloa updates, volcano photos, maps, recent earthquake information and more. Email questions to askHVO@usgs.gov.