This Week
in Fire

Episode 48 of the Halemaʻumaʻu eruption fired in the early hours of 1 June — and in doing so crossed a threshold that had stood since the 1980s. With 48 episodes, the current eruption has surpassed the 47 high-fountaining episodes of the Puʻuʻōʻō eruption from 1983–1986, making it the most episodic-fountaining eruption ever recorded at Kīlauea. Episode 49 is now expected in 10–15 days. Meanwhile Piton de la Fournaise's monitoring data delivered a brief but significant dual inflation signal on 29 May — both shallow and deep sources pressurising simultaneously — before falling quiet again by 1 June.

🇺🇸 Kīlauea Advisory · Yellow

After days of irregular deflation-inflation events that repeatedly pushed the Episode 48 forecast window back, precursory south vent overflows finally began at 5:41 PM HST on 30 May. HVO raised the alert level from Advisory/Yellow to Watch/Orange at that point. This was an unusually extended precursory sequence — 95 south vent overflow events were recorded between 5:41 PM on 30 May and the onset of fountaining at 4:40 AM HST on 1 June, a gap of approximately 11 hours. HVO issued a VONA during the overflow phase noting that low-level eruption had begun and that fountain episode 48 was forecast to start between 30 May and 1 June.

Sustained lava fountaining began at 4:40 AM HST from the north vent — the south vent did not fountain. The north vent fountain reached approximately 200 metres (650 feet) by 5:50 AM HST, at which point HVO estimated a peak effusion rate of around 320 cubic metres per second. The average effusion rate across the episode was approximately 185 cubic metres per second. The plume reached 25,000 feet (7,600 metres) above sea level. Low-altitude winds from the northeast directed tephra and gases to the southwest; higher-altitude winds from the south directed material to the north and northeast. An ashfall advisory was issued for communities north of Hawaiʻi Volcanoes National Park — Mountain View, Pāhoa, and surrounding areas — though most tephra fell within the crater and immediately adjacent rim areas. Episode 48 ended abruptly at 1:37 PM HST after approximately nine hours. HVO lowered the alert level back to Advisory/Yellow at 1:47 PM.

The episode erupted an estimated 5.6 million cubic metres (7.3 million cubic yards) of lava, covering approximately 40% of the Halemaʻumaʻu crater floor. Summit deflationary tilt totalled 17.1 microradians during the episode — the largest deflationary signal yet in this eruption series. Approximately 50 small earthquakes were recorded at the south rim of Halemaʻumaʻu as the episode ended, at depths of less than 1.5 km and mostly below magnitude 2. A small residual lava flow was visible in the V3cam overnight following the episode. As of the 4 June HVO update, both vents are glowing and robust degassing plumes are visible from both vents during daylight. Summit inflation has been underway since Episode 48 ended. Episode 49 is forecast approximately 10–15 days from 1 June — that is, between 11 and 16 June.

🇷🇪 Piton de la Fournaise Vigilance · Watching

A brief but significant geodetic signal at Piton de la Fournaise on 29 May. OVPF's daily bulletin for that date reported that both the summit GNSS stations — indicating pressurisation of a shallow source — and the far-field GNSS stations — indicating a pressurised deep source — were simultaneously recording inflation. This was the first time since the fourth 2026 eruption ended on 12 April that both shallow and deep sources were inflating at the same time; previously each had returned and faded independently. The OVPF May monthly bulletin (published 2 June) confirms that throughout May, a pressurisation of the deep magmatic system was observed, with deep seismic activity and edifice inflation recorded across the month.

However, as of 1–4 June, OVPF's daily bulletins report that neither summit nor far-field GNSS stations are recording any particular signals. The dual inflation of 29 May was short-lived. What has changed is the CO₂ flux picture: the 4 June bulletin notes that both the PCRN (Plaine des Cafres) and GITN (volcano lodge) monitoring stations have been recording high CO₂ fluxes since the end of the February–April eruption — whereas previous weeks had described this as a "decreasing trend." High CO₂ ground flux, even in the absence of GNSS inflation, is a meaningful pre-eruptive indicator at Piton. The alert level was downgraded from Alert 2-2 to Vigilance on 7 May, reflecting the inter-eruptive resting phase. OVPF continue to monitor around the clock.

🇵🇭 Mayon Alert 3 · 150+ days

Mayon's effusive eruption has now been running for more than 150 consecutive days — a five-month eruption with no indication of imminent cessation. Per the GVP/Smithsonian WVAR for the week ending 27 May (the most recent at time of writing), the eruption during 20–27 May continued with lava effusion, pyroclastic density currents, incandescent rockfalls, and ash-and-gas plumes rising as high as 900 m above the summit. The seismic network recorded 286–351 daily rockfalls, 0–8 daily PDCs, and 27–57 daily volcanic earthquakes with 4–20 periods of volcanic tremor per day. Daily SO₂ emissions averaged 988–2,615 tonnes per day. The Mi-isi Gully flow continued its trend of advancing, reaching 1.8 km by 24 May — the second consecutive weekly advance in that drainage from a starting point of 1.3 km at the start of May. The Basud (3.8 km) and Bonga (3.2 km) flows remain unchanged. Alert Level 3 and the 6 km Permanent Danger Zone remain in force.