Indonesia raised Anak Krakatau to its second-highest alert after at least 13 eruptions in a day

Indonesia’s Geological Agency raised Anak Krakatau to Level III, the second-highest of its four alert tiers, at 9pm local time on October 9, up from Level II. The decision followed at least 13 eruptions logged at the volcano in the Sunda Strait during that single day. Level III is a step short of the maximum, but it brings a formal exclusion zone and a warning to coastal communities on both sides of the strait.

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The first eruption of the day came at 4:17pm and sent an ash column 250 metres above the summit, and a second followed at 4:30pm with a 150-metre column. Eleven more eruptions were logged between 6:28pm and 9:20pm, though their ash columns could not be observed. Seismic monitoring recorded 26 eruption earthquakes across the full day, while the agency noted no significant overall rise in volcanic earthquakes, which means the escalation rests on what was seen and logged at the surface rather than on a surge in earthquakes. Earlier in October the agency had already recorded at least five more eruptions, four on October 5 and one on October 8, so the documented minimum since October 1 stands at 18.

Level III and the five-kilometre exclusion zone

The alert came from the Geological Agency through PVMBG, the Volcanology and Geological Hazard Mitigation Centre, according to a Bernama report republished by Malay Mail. Under the agency’s four-tier scale, Level III is the second-highest rung, and the agency said it would re-evaluate the volcano periodically or after any significant change. Nobody may enter a five-kilometre radius around the eruption centre, nor the area within one kilometre of two newly formed islands, which sit northwest and southeast of the main cone. The agency warned of volcanic rocks, heavy ashfall, lava flows and secondary eruptions, and said the restrictions apply to residents, visitors and climbers alike, with no activity permitted inside the zone until the next evaluation changes it.

Lana Saria, head of the Geological Agency, said the rise in activity was marked by 14 eruptions between October 6 and 9, and that residents, visitors and climbers were barred from the five-kilometre zone, as reported by iNews on RCTI+. Coastal residents of Banten and Lampung provinces were asked to stay calm, ignore unverified tsunami claims and follow the local disaster agency, BPBD, a point IDN Times also carried.

Eruption tallies from the agency and the Smithsonian

The “at least 13” figure comes from the agency’s assessment as relayed by Bernama, and it counts individually reported eruptions, including the eleven whose columns went unseen. The Smithsonian Global Volcanism Program, which compiles PVMBG data into its weekly volcanic activity report for October 8 to 14, lists five eruptive events on October 6 to 8 and nine on October 9, with minor plumes up to 50 metres above the crater. The Malay Mail account separately counts at least 18 since the start of October.

The gap is a matter of what is counted and when, and the Malay Mail tally is the agency’s own count of reported events, since observed plumes, seismic signals and satellite detections each log different events. All of the accounts agree on the part that drives the alert: low-level eruptive activity increased in early October and the alert rose at 2100 local time on October 9, with the exclusion zone and public advisory announced at the same time. The agency’s own assessment said signs of increased activity on a low scale began to emerge in early October 2026.

Ash, gas and a volcano that has been here before

The Darwin Volcanic Ash Advisory Centre reported ash at about 1.8 kilometres above sea level at 10:50pm on October 9, drifting west over the Sunda Strait toward the Indian Ocean at about 9 kilometres an hour and forecast to dissipate within six to twelve hours. Satellite monitoring detected sulphur dioxide emissions of 71 to 237.5 tonnes per day between September 21 and October 9, and incandescence has been observed at the volcano since October 6. The Smithsonian entry for Krakatau records low sulphur dioxide and low-level thermal anomalies.

The earlier episode shows how disruptive a Level III volcano in this strait can be even when individual plumes are small.

The volcano has now reached this level twice since early September. It was at Level III from early September until it was lowered to Level II on September 21, and the early-September eruptions sent ash into the atmosphere, forced temporary airport closures and disrupted about 2,961 flights affecting roughly 341,000 passengers. The agency has said Level III remains in force until its next evaluation, and the Smithsonian’s Krakatau volcano page is the place to follow any change in status. Readers in Banten and Lampung are directed by the agency to local disaster-agency instructions rather than unofficial disaster information online, and the agency asked residents not to spread unverified tsunami claims.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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