The Hawaii Volcanological Observatory (HVO) has provided detailed explanations of Kilauea volcano’s recent outburst, clarifying the crucial technical distinction between an “eruption” and an “episode” of lava flows. The objective of this communication is to elucidate the nature of the events observed in the Halemaʻumaʻu crater, which has exhibited continuous and cyclical behavior. The information disclosed is based on rigorous monitoring work and the analysis of seismic and soil deformation data.
Reports on June 14th emphasized the origin of the material expelled during the 49th episode, with images captured at 11:01am showing the release of lava and, later, at 5:59pm, the scene after the activity stopped. During this specific period, only the northern opening released jets of lava, while the southern opening presented only spatters and flows of lesser intensity. During idle times, the fissures exude water vapor and volcanic gases, resulting in a dense white plume, as documented by the USGS’s V2cam camera.
Over the past eighteen months, the recurring and striking eruption in the Kilauea summit area has already seen 49 episodes of lava release, with the 50th expected next week. This frequency raises the discussion about appropriate terminology: why are these phenomena categorized as episodes and not isolated eruptions? The explanation lies in the continuity of underground magmatic activity, even with interruptions on the surface of the volcano.
Since December 23, 2024, the volcano has followed a regular and cyclical pattern of behavior. Each sequence begins with precursor splashes and overflows from one or both craters on Halemaʻumaʻu, which can last from a few hours to several days, preceding almost every episode. The activity then evolves into lava jets coming from one or both craters, operating for periods ranging from 4.5 hours to more than 8 days, and then ending with a pause in the release of lava onto the surface.
Delving deeper into the difference between an eruption and volcanic episodes
A volcanic eruption occurs when magma accumulated underground rises and reaches the surface, manifesting itself through effusive lava flows, jets of incandescent material or explosive eruptive columns. In certain situations, an eruption may experience brief interruptions or pauses in the outflow of lava, even though the magma continues to move or accumulate internally. Because lava jets have consistently repeated from the same two main vents (north and south) since December 2024, the USGS Hawaii Volcanological Observatory designates these intervals as episodes within a continuous eruption unfolding at Halemaʻumaʻu volcano.
In Kilauea’s activity history, when breaks exceeded 90 days, it was common to see a longer period of inactivity or the emergence of a new eruption in another part of the volcano. However, despite temporary interruptions in Kilauea’s current summit eruption, monitoring data indicates that the volcano remains in a state of heightened activity, and the eruption has not come to an end, even when lava is not visible on the surface. The ongoing episodic eruption maintains moderate to high activity levels during lulls, which includes ground deformation, seismic shaking, and the constant release of volcanic gases.
Hawaii Observatory forecasting methods for volcano activity
Inclinometers installed on Kilauea’s summit record a deflationary slope during eruptive events, indicating the exit of magma from the chamber towards the surface. After each episode ends, there is a rapid shift from deflation to inflation as pressure in the summit region is reestablished. This recurring cycle of deflation during episodes and inflation during pause periods is the main tool used by the Hawaii Volcanological Observatory (HVO) to estimate the proximity of a new event, based on the volume expelled and the speed of repressurization.
During periods of lava jets, seismic stations located at the summit of Kilauea and in adjacent areas detect intense volcanic tremors, which signal the movement of internal fluids. During pauses, the tremor generally decreases, but does not cease completely, persisting with varying intensities, influenced by the emission of volcanic gases, the depth of the magma in the openings and other geological features.
Gas emission rates in Kilauea’s summit region also remain elevated in the intervals between eruption episodes, with sulfur dioxide releases often ranging between 1,000 and 5,000 tons per day. These values are considerably higher than those recorded before the start of the current eruption, when sulfur dioxide emissions were below 120 tonnes per day.
The pattern of episodes with pauses is not unique to this current eruption. For example, in the first three and a half years of the Kilauea Middle East Rift Zone eruption at Puʻuʻōʻō, episodic gusher events similar to those currently occurring at the summit were also observed. At that time, interruptions or rest periods between episodes were, on average, longer than today, with the longest reaching 65 days, offering a significant historical parallel to understanding current dynamics.
To date, these short interruptions between episodes, which typically last days to weeks, have been accompanied by intense seismic shaking, volcanic gases, and ground deformation. These indicators often evolve into low-level eruptive activity before the continued emission of lava jets, all signaling the high probability that another gushing event is near.
The Hawaii Volcanological Observatory (HVO) closely monitors the data to identify any signs of magma movement to another part of the volcano, which could indicate a change in the ongoing eruption or possibly the start of a new eruption in a different location. Although it is not possible to predict the end or manner in which this eruption will end, the observation of consistent patterns in monitoring data following the end of a gushing episode suggests a high probability that another gushing event will occur at the northern and/or southern vents of Halemaʻumaʻu volcano.
Current condition and alert levels of Kilauea and Mauna Loa volcanoes
Kilauea has been experiencing episodic eruption from its summit caldera since December 23, 2024. The United States Geological Survey (USGS) maintains its volcanic alert level classified as WARNING.
The 49th lava eruption episode at the summit lasted 7.5 hours on June 14. Inflation in the summit region, detected since the end of this event, suggests the imminence of a new occurrence. Current models predict that the 50th episode is most likely to occur between June 23 and 27.
No anomalies were recorded in Kilauea’s East or Southwest Rift Zones. Mauna Loa does not exhibit eruptive activity and its volcanic alert level, according to the USGS, is at NORMAL.
In the last week, four earthquakes were recorded in the Hawaiian Islands: a 2.5 magnitude earthquake, which occurred 15 km south of Honokaʻa and 27 km deep, on June 18, at 2:11 am; another of magnitude 4.5, 17 km southeast of Pahala and 33 km deep, on June 17, at 2:14 am; a third, of magnitude 2.8, 8 km south of Honaunau-Napoopoo and 22 km deep, on June 14, at 11:16 am; and finally, a 3.1 magnitude earthquake, 6 km west of Kahaluu-Keauhou and 5 km deep, on June 12, at 9:48 pm.