At 3:19 a.m. on Saturday, Oct. 17, the north vent in Halemaʻumaʻu doubled its fountain height, and the summit tiltmeter at Uēkahuna started to drop fast. By 5 a.m. the fountain stood about 720 feet tall and the plume had climbed to roughly 25,000 feet. By 9:03 a.m. it was over. At 5:45 that morning, a USGS photographer at the Steam Vents caught the fountain through the mist, with lava streaming down the shield that has built up around the vent.
That was episode 55. It came 53 days after episode 54 on Aug. 25, the longest gap since the eruption began on Dec. 23, 2024. The summit was busier and stranger between August and October than at any point in this eruption. In the process it broke the rhythm that had made Kīlauea something you could plan a morning around. If you live in Volcano, that matters more than the fountain itself.
The old rhythm, and why it was useful
From December 2024 through August 2026, Kīlauea followed a pattern. Fountaining episodes usually lasted under 12 hours, with pauses of two weeks or more between them. The summit swelled steadily between episodes and dropped sharply during each one. That steady swelling let the Hawaiian Volcano Observatory model when the next fountain was likely. For anyone living a few miles from Halemaʻumaʻu, that meant you could check a forecast window and decide whether to set an alarm.
After Aug. 25, the swelling stopped behaving. HVO described the summit as unusually pressurized, rising in irregular steps, and said the changing patterns made it impossible to forecast the next fountain. By Oct. 17, the magma chamber under Halemaʻumaʻu had built up more pressure than HVO typically saw before recent fountains. All that extra pressure didn't produce a bigger fountain on schedule. It went looking for other ways out.
Fifty-three days, in order
Here's what the summit did between episodes 54 and 55, pieced together from HVO's notices:
| Date | What happened at the summit |
|---|---|
| Aug. 25 | Episode 54, the last fountain for 53 days |
| Sept. 7 | Sluggish lava overflows begin at the north vent |
| Sept. 7–12 | 104 intermittent north-vent overflows, with small dome fountains and flows reaching about half a mile |
| Sept. 14–16 | Six new vents open along the base of Halemaʻumaʻu's northwest wall |
| Sept. 30 | Magnitude 3.4 earthquake at 9:52 p.m. shakes loose rockfalls on the caldera's north wall |
| Sept. 30–Oct. 1 | A magma intrusion pushes to within about 1,000 feet of the surface |
| Oct. 16 | Continuous overflows from the south vent, then the north and west vents |
| Oct. 17 | Episode 55, 3:19 to 9:03 a.m. |
The Sept. 7 overflows are the number that shows how far things drifted from normal. HVO counts them as precursory activity: lava reaching the surface ahead of a fountaining episode. They came 39 days before episode 55. The longest lead-up before that was 6 days. In earlier episodes, overflows meant a fountain was hours or days away. This time they meant very little about timing.
Where the pressure went instead
The six vents that opened Sept. 14–16 did so quietly, with little or no fountaining, and fed small pāhoehoe flows across the crater floor. HVO's Sept. 23 map put their output at about 14 hectares of new lava, roughly 35 acres, and about 0.4 million cubic meters. For scale, episode 55 erupted an estimated 7 million cubic meters in under six hours. So the new vents, active over about two days by HVO's count, let out about a seventeenth of what one fountain did. That was enough to show the magma had more than one way up, but nowhere near enough to relieve the pressure.
The intrusion at the end of September is the part with the longest reach. HVO's Oct. 7 status report said the magma followed fracture systems left in Kaluapele, the summit caldera, by the 2018 collapse of Halemaʻumaʻu. It settled just north of the crater, very close to the surface, and left a narrow band of deformed ground and small new fractures. The National Park Service said the new cracks run between Uēkahuna and Wahinekapu, also called Steaming Bluff. That's a stretch of caldera floor below two of the overlooks people visit most.
The 2018 cracks are old and weak, and magma can now use them. HVO's list of possible outcomes was wide. Fountaining could resume. Lava could seep out of the cracks. Magma could intrude into new parts of the summit or move toward a rift zone, or the eruption could stop. HVO said these changes could happen with little warning.
How episode 55 finally started
HVO's explanation of the trigger is the most interesting line in its Oct. 17 update. From the morning of Oct. 16, the south vent overflowed without stopping. The north vent joined that evening, and the west vent, which rarely overflows, started late that night. In its Oct. 17 update, HVO said these vigorous overflows "appear to have purged the system of older degassed magma and allowed more water-rich magma into the conduit to trigger episode 55."
Put simply, gas-poor magma had been sitting in the pipe. A fountain needs gas to drive it, so the volcano had to clear out the flat magma first. That helps explain how the summit could be more pressurized than ever and still go weeks without fountaining.
By 8:30 a.m. on Oct. 17, lava covered about 75 percent of the Halemaʻumaʻu crater floor. Once the fountain stopped, the tiltmeter went straight back to inflating. Big Island Now reported that all vents and flows stayed inside Halemaʻumaʻu.
Gas and fallout went southwest this time
During fountaining, summit sulfur dioxide output usually runs around 100,000 tonnes per day. HVO expected it to fall back to 1,000 to 5,000 tonnes per day afterward. On Oct. 17, winds below 20,000 feet blew from the northeast and pushed the plume southwest. HVO expected most tephra to land in the closed part of the park, with traces of fine ash and Pele's hair possible in Pāhala and other Kaʻū communities. HVO also warns that sulfur dioxide and vog can cause breathing problems even when the vents are not erupting. Where the gas goes during the next episode depends on the wind that day.
What the outlook says, and what it leaves out
Just before 10 a.m. on Oct. 17, HVO lowered Kīlauea from WATCH/ORANGE to ADVISORY/YELLOW. Its aviation notice that morning gave the only timing guidance available:
"Fountain activity in this area unlikely for the next several weeks."
That isn't a forecast window, and HVO hasn't offered one. Irregular ground movement since Aug. 25 still prevents forecast modeling. By Thursday, Oct. 29, 12 days will have passed since episode 55. The last gap ran 53 days, and the ones before it were usually about two weeks. Either could be the guide for episode 56, and HVO's own data doesn't yet say which.
The viewing map is smaller than it was in summer
The closures from the pause still shape where you can stand. The Keanakākoʻi side closed first. Big Island Video News reported on Oct. 1 that the closure covered old Crater Rim Drive, the overlooks near Keanakākoʻi crater, and Crater Rim Trail to Keanakākoʻi, while the Devastation parking area stayed open. On Oct. 7, the park also closed Halemaʻumaʻu Trail and part of Byron Ledge Trail, 1.3 miles in all, because both descend to the caldera floor and have had dangerous rockfalls before. The NPS release noted that the nearest parking on the Keanakākoʻi side is about a mile from the overlooks, which makes the area hard to evacuate quickly. Treat all of those areas as closed until the park's alerts and conditions page says they've reopened.
On the west side of the caldera, the park's eruption viewing guide lists Uēkahuna, Kīlauea Overlook, Wahinekapu and the Steam Vents, and the overlooks near the Welcome Center, all reached by Crater Rim Drive West. It says the Welcome Center, Kīlauea Overlook and Uēkahuna usually have more parking. The Kīlauea Overlook page suggests skipping 5 to 9 p.m., when traffic is heaviest, and going before sunrise instead. Episode 55 hit its peak around 5 a.m., so going before sunrise also happened to be the right call this time.
Without a forecast, here's a short list of what to check:
- HVO's Kīlauea volcano updates for the alert level and any new notice. A return to WATCH/ORANGE is the clearest sign that something is building.
- The NPS alerts and conditions page before you drive in, for closures on the Keanakākoʻi side and the caldera trails.
- The wind direction on the morning of any episode, because it decides which communities get the gas and Pele's hair.
- Event notices if your weekend plans are near the crater rim. Volcano Art Center's Hula Kahiko with Stacy Kaʻauʻa and Unuokeahi is set for Nov. 14 at the kahua hula near the gallery, and the art center says performances can be canceled for eruption activity.
Closer to home, the Cooper Center's Sunday market at 19-4030 Wright Road runs 6 to 10 a.m., and its Thursday market runs 3 to 6 p.m.
If you're thinking about what the summit's changes mean for your property or your next move in East Hawaiʻi, Tessie Fontes is happy to talk story. Let's connect for local guidance or a home valuation.
