Indonesia Says Anak Krakatau’s 25-Hour Continuous Eruption Has Ended

A 25-hour episode of continuous eruption at Mount Anak Krakatau has ended, but Indonesia’s Geological Agency says the volcano could erupt again soon.

The episode began at 11:07 p.m. local time on Sept. 4 and ended at 12:04 a.m. on Sept. 6, according to an evaluation report cited by the agency. Lana Saria, head of the Geological Agency, said the volcano had since returned to Strombolian-style eruptions, with three earthquakes of that type recorded.

The agency interpreted the shift as evidence that the prolonged continuous eruption had stopped. But the danger has not passed. Observations from Sept. 6 to 7 recorded three eruption earthquakes, nine emission earthquakes, 93 low-frequency earthquakes, 98 hybrid or multiphase earthquakes, four periods of continuous tremor and one shallow volcanic earthquake.

The RSAM seismic-amplitude graph, which spiked on Sept. 5, has declined since Sept. 6. Deformation data from the Tanjung monitoring station showed slight inflation beginning in early August, while the Lava93 station recorded a steady pattern.

The Geological Agency has kept Anak Krakatau at Level III, or Alert. It advised residents, tourists and hikers not to enter the three-kilometer danger zone around the active crater because of possible incandescent rock, pyroclastic flows, lava flows and heavy ashfall. Coastal communities in Banten and Lampung were urged to remain calm and reject rumors of a possible eruption-related tsunami. The agency also advised people to wear masks outdoors to reduce exposure to volcanic ash.

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Following the end of that episode, Mount Anak Krakatau's volcanic activity has transitioned back to Strombolian eruption characteristics, marked by the recording of three Strombolian-type eruption earthquakes.