Anak Krakatau activity rose from July before September eruptions, Indonesia’s Geological Agency says

Indonesia’s Geological Agency has traced Anak Krakatau’s renewed eruption to rising activity that began in July 2026, following a series of small eruptions that continued until Dec. 16, 2023.

Geological Agency chief Lana Saria said the volcano’s latest development remained connected to the major eruption of Dec. 22, 2018. That eruption caused part of the volcano’s body to collapse and triggered a tsunami in the Sunda Strait. “The eruption on Dec. 22, 2018 produced a landslide and a tsunami wave,” Lana said at a press conference on Sept. 6, 2026.

Anak Krakatau erupted again on July 2, prompting authorities to raise its activity status from Level II, Alert, to Level III, Standby. Activity continued to build until the volcano entered an eruptive period in September.

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The eruption on Dec. 22, 2018 produced a landslide and a tsunami wave.

At 11 p.m. local time on Sept. 4, the volcano began erupting continuously. The eruption produced lava fountains, rumbling sounds and explosions. Lana said lava fountains were a characteristic feature of Krakatau volcanoes and a common phenomenon at volcanoes with relatively low magma viscosity. Activity reached its highest level on Sept. 5, marked by repeated and continuous eruptions.

The agency said the pattern showed that magma and gas were still being supplied inside the volcano, but cautioned that frequent eruptions did not automatically mean a larger eruption would follow. It continues to assess seismic activity, visual observations, deformation, gas emissions, satellite imagery and field reports. Residents and tourists have been told not to enter the area within three kilometers of the activity center because of potential hot clouds, lava, incandescent rocks, ashfall and heavy volcanic ash.

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This lava fountain is one of the characteristics of Krakatau volcano and is a common phenomenon at volcanoes with relatively low magma viscosity.