Volcano Watch: Halemaʻumaʻu eruption reaches new heights as HVO updates Volcano Alert Notifications

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

Episode 23 of Kīlauea’s ongoing eruption within Halemaʻumaʻu occurred May 25, 2025.

Record-setting lava fountain and plume heights were reached quickly during this eruptive phase, less than 1 hour after the start of the most recent episode of the summit caldera eruption that began Dec. 23, 2024.

Given the increasing airborne volcanic hazards associated with each new eruptive episode, Hawaiian Volcano Observatory is changing its episode notification types moving forward.

Episode 23 lava fountains erupted continuously for 6 hours and reached heights of about 1,150 feet. These were the highest lava fountains observed so far during the current eruption.

An impressive blanket of tephra — volcanic rock fragments carried into the air — was deposited beneath and downwind of these fountains, primarily in the upper part of Kīlauea’s Southwest Rift Zone in the closed area of Hawaiʻi Volcanoes National Park.

This episode also had the highest gas plume seen thus far in this eruption sequence.

The plume reached heights of more than 20,000 feet — and likely more than 25,000 feet — above Kīlauea’s summit, which is at an elevation of about 4,000 feet above sea level. The plume contained high levels of water vapor, carbon dioxide and sulfur dioxide.

These record-setting fountain and plume heights were reached quickly, less than 1 hour after Episode 23 started.

Following an extended period of gradual inflation and precursory low-level activity, Episode 23 began at 4:15 p.m., with thin jets of lava erupting from the north vent. Fountaining became more vigorous about 4:25 p.m. and then escalated quickly and dramatically about 4:36 p.m. as tremor intensified and gradual inflation switched to rapid deflation.

North vent fountains approached 1,000 feet in height by 5 p.m. and peaked just after 5:30 p.m. South vent fountaining began at 5:20 p.m. and reached heights of 600 to 800 feet by 6:30 p.m. that were sustained until the final hour of the episode.

Episode 24 will likely begin within the coming week.

Kīlauea’s summit is currently reinflating and magma remains close to the surface within the north and south vent conduits.

During a helicopter overflight May 28, Hawaiian Volcano Observatory scientists could see lava churning away at a depth of a few tens of yards within the north vent. Strong orange glow from the vents is visible at night on observatory webcams and from public viewing areas in Hawaiʻi Volcanoes National Park.

As the eruption transitions from Episode 23 to 24, Hawaiian Volcano Observatory is also transitioning to a different type of volcano alert notification to announce significant changes in activity such as lava fountaining episodes.

Starting with Episode 24, a paired Volcano Activity Notice, or VAN, and Volcano Observatory Notice for Aviation, or VONA, will be issued to announce the beginning and end of fountaining episodes, replacing the status report notifications we have been issuing to announce the beginning and end of eruptive episodes.

When possible, the paired notifications will also be issued to announce the onset of confirmed precursory activity.

Hawaiian Volcano Observatory is making this transition because of the increased fountain and plume heights during recent episodes and their rapid onset.

The goal is to more effectively communicate the presence or anticipated presence of airborne hazards such as volcanic gas emissions and tephra that, depending on wind conditions, can impact Hawaiʻi Volcanoes National Park, nearby communities and aviation sector.

If you signed up to receive volcano updates using the U.S. Geological Survey Volcano Notification Service, then the terms VAN and VONA probably look familiar to you. That’s because the observatory always issues VAN/VONA notifications when we change Volcano Alert Level and/or Aviation Color Code.

For example, Hawaiian Volcano Observatory issued a VAN/VONA at 2:41 a.m. Dec. 23, 2024, to announce the start of the current eruption and raised Kilauea’s Volcano Alert Level/Aviation Color Code from Advisory/Yellow to Warning/Red.

Another VAN/VONA was issued at 6:43 a.m. Dec. 23, 2024, to go from Warning/Red to Watch/Orange, the level at which Kīlauea has remained since.

If future activity remains similar to the past 23 episodes, there will be no change in Volcano Alert Level or Aviation Color Code at Kīlauea even though new paired notifications are issued.

Visit the Volcano Notification Service website to check your volcano notification subscriptions.

High lava fountains and eruptive plumes are significant airborne hazards.

Recent fountaining episodes in Halemaʻumaʻu escalated quickly and literally reached new heights. VAN/VONA notifications will more clearly inform island residents, visitors and aviators when these hazards are occurring or expected to occur.

Volcano Activity Updates

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

Episode 23 of the Kīlauea summit eruption in Halemaʻumaʻu Crater occurred May 25, with approximately 6 hours of sustained high lava fountaining from the north and south vents. Fountains reached a record height for this eruption — an estimated 1,150 feet — at about 5:30 p.m. May 25.

Strong glow visible in the north and south vents and summit region inflation since the end of Episode 23 suggests another episode is possible.

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.

Mauna Loa is not erupting. Its U.S. Geological Survey Volcano Alert Level is at Normal.

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

• MAGNITUDE 3.9 located 34 miles west-southwest from Captain Cook at a depth of 23 miles at 9:36 p.m. May 26.
• MAGNITUDE 3.1 located 9 miles west-southwest from Kailua-Kona at a depth of 2 miles at 4:19 p.m. May 25.

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.