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Kīlauea’s summit swelling gives scientists a useful clue that magma pressure is building, but it is not a countdown to the next lava fountain. U.S. Geological Survey scientists track small changes in ground tilt; when sustained fountains begin, the tilt commonly reverses as pressure is released. That repeating pattern has supported probability windows during more regular phases of the eruption, but it cannot guarantee when an episode will start.
How does summit swelling help forecast an episode?
At Kīlauea’s summit, tiltmeters record subtle changes in the angle of the ground. Scientists interpret those changes as evidence of deformation associated with changing magma pressure beneath the surface. As pressure builds, the summit inflates and the ground tilts; when lava fountains release pressure, the tilt often shifts toward deflation.
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The distinction matters: swelling is a monitoring signal, not proof that a fountain will begin at a particular time. The U.S. Geological Survey’s Hawaiian Volcano Observatory (HVO) says, “The switch to deflationary tilt generally defines an episode start.” In other words, scientists can often identify an episode from the change in the signal, while the preceding inflation helps inform forecasts about what may happen next. USGS HVO’s Kīlauea summit eruption FAQ explains how the episodes are defined and forecast.
What the tilt pattern can—and cannot—tell scientists
| Monitoring pattern | What it suggests | Forecast meaning |
|---|---|---|
| Inflationary tilt | Pressure is accumulating and the summit is deforming. | Fountaining may be approaching, but the signal does not specify an exact start time. |
| Deflationary tilt | Pressure is being released; sustained fountains commonly accompany this reversal. | HVO generally uses the switch toward deflation to define the start of an episode. |
| Irregular or changing tilt | The deformation no longer follows a clear, repeatable pattern. | Probability windows may be unreliable or impossible to model from the earlier pattern. |
During more regular stretches, repeated inflation-and-deflation cycles gave HVO a basis for publishing probability windows for possible episodes. Such a window is conditional: it depends on the monitoring pattern continuing to resemble the behavior on which the forecast was based. If the pattern changes, the forecast can lose usefulness.
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Why the October 2026 forecast windows no longer applied
As of the latest reviewed HVO update, issued October 6, 2026, a lava-fountaining episode 55 remained possible, but HVO said it could no longer model forecast windows because inflation and deflation had become irregular. The update reported minor spattering at both the north and south vents, with strong glow and flaming; the September 30–October 1 summit intrusion had not reactivated. Read the October 6 HVO volcano notice for that dated activity and alert information.
An October 7 status report described a near-surface magma intrusion emplaced September 30 to October 1 along fracture systems associated with the 2018 collapse of Halemaʻumaʻu. USGS said the intrusion changed its interpretation of likely outcomes and that the behavior patterns previously used for forecasting were no longer evident in the monitoring data. The earlier windows should therefore not be treated as current predictions. See HVO’s activity updates for the report and subsequent updates.
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The October 6 notice listed Kīlauea at alert level WATCH and Aviation Color Code ORANGE. Alert levels can change; consult the newest USGS volcano notice for current status rather than relying on this dated report.
How today’s episodes fit Kīlauea’s eruptive history
The current episodic fountaining is occurring in Halemaʻumaʻu within Kīlauea’s summit caldera, Kaluapele. HVO has compared recent cycles with fountaining at Kīlauea Iki in 1959, Maunaulu in 1969, and the early Puʻuʻōʻō eruption from 1983 to 1986. During the 1969 Maunaulu sequence, tilt records likewise showed summit deflation during fountains and inflation during pauses. These comparisons help explain the monitoring pattern, but they do not mean the current eruption will follow the same course. HVO’s April 3, 2025 Volcano Watch discusses the tilt signal and historical episodes.
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Historical measurements also show how much the summit landscape changed during the earlier part of this eruption. In a 2026 account covering activity through fall 2025, the USGS National Civil Applications Center reported 32 fountaining events and a maximum fountain height of 380 meters (1,247 feet). It also reported that the crater floor rose 53 meters (173 feet), from approximately 917 meters (3,008 feet) above sea level in December 2024 to 970 meters (3,182 feet) by fall 2025. These figures describe the period through fall 2025, not totals current to October 2026. Read the USGS account of monitoring Kīlauea’s eruption episodes.
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The active crater area is hazardous and some surrounding areas are closed to the public. USGS lists volcanic gases such as sulfur dioxide, Pele’s hair and other volcanic fragments, unstable crater walls, ground cracks, and rockfalls among the risks; conditions can cause serious injury or death. Follow Hawaiʻi Volcanoes National Park closures and official instructions, and do not enter closed areas to get a closer view.
For remote viewing, HVO provides official summit webcams and livestreams. Its Kīlauea summit eruption FAQ links to viewing options and explains the hazards.
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