Halemaʻumaʻu Eruption Reaches New Heights as HVO Updates Volcano Alert Notifications — USGS Volcano Watch

Episode 23 of Kīlauea's ongoing eruption within Halemaʻumaʻu occurred on Sunday, May 25, 2025. Record-setting lava fountain and plume heights were reached quickly for this eruption, less than one hour after episode 23 started. Given the increasing airborne volcanic hazards associated with this eruption, the USGS Hawaiian Volcano Observatory will change episode notification types moving forward.

Episode 23 lava fountains erupted continuously for six hours and reached heights of about 1,150 feet (350 meters). These were the highest lava fountains observed so far during the current eruption, which began on December 23, 2024. 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. 

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High lava fountains erupted from the north and south vents during episode 23 of the ongoing Kīlauea summit eruption in Halema’uma’u. Fountains reached heights of about 1,150 feet (350 meters) above the vent about an hour after the episode began. These were the highest lava fountains observed so far during the current eruption. The tall narrow finger of lava shown here, as well as the lower fountain to the right, are both sourced from the south vent, while the wider fountain in the foreground originates from the north vent. The USGS Hawaiian Volcano Observatory will start issuing “Volcano Activity Notice (VAN)” / “Volcano Observatory Notice for Aviation (VONA)” notifications, with no change in Volcano Alert Level or Aviation Color Code, to announce the beginning and end of future sustained fountaining episodes. USGS photo by M. Patrick.

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 (6,100 meters)—and likely over 25,000 feet (7,600 meters)—above Kīlauea’s summit, which is at an elevation of about 4,000 feet (1,200 meters) above sea level. The plume contained high levels of water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2).

These record-setting fountain and plume heights were reached quickly, less than one 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 around 4:25 and then escalated quickly and dramatically around 4:36 p.m. as tremor intensified and gradual inflation switched to rapid deflation. North vent fountains approached 1,000 feet (300 meters) in height by 5:00 p.m. and peaked just after 5:30 p.m. South vent fountaining began at 5:20 p.m. and reached heights of 600–800 feet (180–250 meters) 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 on May 28, USGS Hawaiian Volcano Observatory (HVO) scientists could see lava churning away at a depth of a few tens of yards (meters) within the north vent conduit. Strong orange glow from the vents is visible at night on HVO webcams and from public viewing areas in Hawai’i Volcanoes National Park. 

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

Starting with episode 24, HVO will issue a paired “Volcano Activity Notice (VAN)” and “Volcano Observatory Notice for Aviation (VONA)” (VAN/VONA) to announce the beginning and end of fountaining episodes. Our use of VAN/VONA will replace the Status Report notifications we have been issuing to announce the beginning and end of eruptive episodes. When possible, VAN/VONA notifications will also be issued to announce the onset of confirmed precursory activity.

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The Kīlauea plume from episode 23 reached heights of more than 20,000 feet (6,100 meters)— likely over 25,000 feet (7,600 meters)—above Kīlauea’s summit, which is at an elevation of about 4,000 feet (1,200 meters) above sea level. This photo, taken from Mauna Kea and looking south, shows Mauna Loa in the right side of the photo and the Kīlauea plume rising above the clouds in the left side of the photo. The plume contained high levels of water vapor (H2O), carbon dioxide (CO2), and sulfur dioxide (SO2). USGS webcam photo.

HVO 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 like volcanic gas emissions and tephra that, depending on wind conditions, can impact Hawaiʻi Volcanoes National Park, nearby communities, and the aviation sector.

If you have signed up to receive volcano updates using the USGS Volcano Notification Service (VNS), then the terms VAN and VONA probably look familiar to you. That’s because HVO always issues VAN/VONA notifications when we change Volcano Alert Level and/or Aviation Color Code. For example, HVO issued a VAN/VONA on December 23, 2024, at 2:41 a.m. to announce the start of the current eruption and raised Kilauea’s Volcano Alert Level / Aviation Color Code from ADVISORY/YELLOW to WARNING/RED.

HVO issued another VAN/VONA on December 23, 2024, at 6:43 a.m. to go from WARNING/RED to WATCH/ORANGE. Kīlauea has remained at WATCH/ORANGE since then. 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 VAN/VONAs are issued. 

Visit the Volcano Notification Service website to check your volcano notification subscriptions: https://volcanoes.usgs.gov/vns/.

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