Volcano Watch: 20 episodes and counting — lava fountains continue in Kaluapele

“Volcano Watch” is a weekly article and activity update written by U.S. Geological Survey Hawaiian Volcano Observatory scientists and affiliates. This week’s article was written by Hawaiian Volcano Observatory geologists Drew Downs and Natalia Deligne.

Eruptive activity at Kīlauea’s summit began again Dec. 23, 2024, with the first in what has become 20 discrete lava fountaining episodes. Many episodes have had dual fountains — two erupting at the same time — which is a rare occurrence at Kīlauea on the Big Island in Hawaiʻi and worldwide.

The most recent Episode 20 concluded at 9:28 p.m. May 6 after just 4.5 hours of lava fountaining.

Sustained fountains, sometimes to impressive heights, have awed crowds that flocked to Hawaiʻi Volcanoes National Park to view the eruptive activity — along with those watching from home on two U.S. Geological Survey Hawaiian Volcano Observatory livestreams (V1cam and V2cam).

The duration of semi-regular lava fountaining has ranged from Episode 20’s 4.5 hours to as long as Episode 3’s 8.5 days. However, many — 11 of the 20 — fountaining periods lasted less than 24 hours.

Once sustained lava fountains begin, they usually reach heights of between 100 and 350 feet above the vents. The highest fountains measured yet since the eruption started reached to more than 1,000 feet during Episodes 15 and 16 in March and April.

These lava fountains fed lava flows, some more extensive than others, that collectively continued to fill the crater formed during the 2018 summit collapse. In some places near the vents, the lava flows are nearly 200 feet thick, and they have covered 816 acres.

Repose intervals — or the pause times between episodes — have ranged from 16 hours to 12 days. Intermittent spattering and occasional lava flows have occurred between episodes, as happened twice during Episode 18, when lava flows issued from the vents for a few hours a few days before the onset of sustained lava fountains.

These impressively high lava fountains have produced tephra (fragments of lava) and Pele’s hair (fibers of volcanic glass). The distribution of tephra is controlled by prevailing wind patterns, with fallout zones downwind of the vents.

Trade winds blowing to the southwest are most common, and this resulted in tephra accumulating in the closed area of Hawaiʻi Volcanoes National Park to thicknesses that can reach greater than 6.5 feet.

During slack and Kona winds, tephra and Pele’s hair have fallen on the summit region, around Volcano Village, the Volcano Golf Course and along Highway 11 near Nāmakanipaio Campground.

Almost all eruptive activity has been sourced from two vents at the base of the western wall of Halemaʻumaʻu Crater within Kaluapele, the volcano’s summit caldera. These are referred to as the north and south vents, and they have alternated in dominance during episodes.

At times, the south vent has generated spectacular lava fountains that have reached more than 1,000 feet tall; whereas, the north vent has primarily exhibited low‑level spattering or lava ponding, but there have been reversals of this pattern.

Since Episode 14, gas pistoning — the rhythmic rise and fall of the lava column — has been observed within both vents hours to a full day prior to fountaining, and it is usually visible in the V1cam livestream.

Each episode of high lava fountaining also coincides with the onset of sharp deflation at the summit.

Pre-fountaining inflation recorded by summit tiltmeters, used to measure inflationary and deflationary signals near Uēkahuna and to the south of Kaluapele, gives way to rapid deflation. At the same time, seismic tremor increases rapidly as more fluid moves through the conduits to erupt from the vents.

A rapid turnaround from deflation to inflation and drop in seismic tremor typically marks the end of an eruptive episode.

These spectacular lava fountains have been easily visible from many of the publicly accessible overlooks within Hawaiʻi Volcanoes National Park. Even so, hazards persist during volcanic activity for those visiting to enjoy the sights.

Shifting winds blow around elevated concentrations of volcanic gases, particularly strong-smelling sulfur dioxide, and tephra and Pele’s hair that are mostly comprised of volcanic glass.

The gases and small glassy particles can irritate respiratory systems, and Pele’s hair can form splinters under the skin.

Hawaiian Volcano Observatory remains steadfast and vigilant as lava fountaining episodes continue at the summit of Kīlauea, maintaining its monitoring and livestreaming of the volcano to document the eruption’s evolution, inform hazard assessments and apprise the public of ongoing volcanic activity.

Volcano Activity Updates

Kīlauea has been erupting episodically since Dec. 23, 2024, within the summit caldera. Its U.S. Geological Survey Volcano Alert level remains at Watch.

Episode 20 of the Kīlauea summit eruption in Halemaʻumaʻu Crater ended May 6 after just 4.5 hours of fountaining, with lava geisers reaching maximum heights of about 500 feet at the north vent.

Strong glow has been visible in both the north and south vents, with summit region inflation since the end of Episode 20 suggesting another episode is possible.

Sulfur dioxide emission rates also 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.

Mauna Loa is not erupting. Its Volcano Alert Level remains at Normal.

One earthquake was reported felt during the past week in the Hawaiian Islands:

• MAGNITUDE-3.6 earthquake located 3 miles west-southwest of Laupāhoehoe at at depth of 19 miles at 12:59 p.m. May 2.

Hawaiian Volcano Observatory continues to closely monitor Kīlauea and Mauna Loa.

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