Following a 25-hour eruption in September 2026, the Anak Krakatau volcano in Indonesia expanded by 81 acres (33 hectares) while satellite imagery detected two new land formations nearby, the country’s Geology Agency stated.
Satellite Imagery Reveals Land Growth Around Sunda Strait Caldera
Comparison photos from satellite imagery taken on August 8 and September 15 showed new lava deposits following the volcanic activity, according to a social media post by the Geology Agency. Sentinel satellite imagery captured on September 20 showed one new formation approximately 760 metres northwest of Anak Krakatau’s coastline and another about 495 metres to the southeast.
Rita Susilawati of the Center for Volcanology and Geological Hazard Mitigation (PVMBG) told AFP that the features were spotted in images of the water-filled caldera in the Sunda Strait between Java and Sumatra islands. While some media reports described the formations as islands, experts stated it remains too early to know if the features will become permanent or wash away due to ocean tides and erosion.
Did You Know? Anak Krakatau, which translates to “child of Krakatau” in Bahasa Indonesia, began emerging a century ago from the area previously occupied by the older Krakatau volcano. That predecessor destroyed itself in massive 1883 eruptions that killed more than 36,000 people and sent ash as far as 6,100 kilometres away.
Volcanic Ash Closes Regional Airports and Cancels Flights
The intense eruptions, which occurred continuously from September 4 to 6, sent volcanic ash over Jakarta and surrounding areas. The resulting ash clouds forced the closure of several regional airports, affecting more than 340,000 travellers and leading to 2,961 flights being cancelled, delayed, or diverted.
Rita Susilawati noted that Anak Krakatau currently sits at alert Level 2, the second lowest out of four danger categories, with officials advising the public not to approach within three kilometres of the eruption center. The September activity followed a pattern of Strombolian and Surtseyan eruptions driven by interactions between magma and seawater within the active zone of the Pacific Ring of Fire.
Expert Insight: Volcanologists monitoring the Sunda Strait highlight that the primary long-term hazard extends beyond active eruption phases. Scientific modeling by international research teams highlights ongoing concerns about potential slope collapses and underwater landslides within the caldera, similar to the event that triggered a fatal tsunami in 2018.
Frequently Asked Questions
How large is the expansion of Anak Krakatau following the recent eruptions?
The country’s Geology Agency reported that the volcano expanded by 81 acres (33 hectares) based on a comparison of satellite images taken on August 8 and September 15, 2026.
Where are the two new land formations located relative to the volcano?
Sentinel satellite imagery from September 20 showed one formation located about 760 metres northwest of Anak Krakatau’s coastline and another about 495 metres to the southeast, situated on either side of the volcano’s crater.
What is the current alert level for Mount Anak Krakatau?
The volcano monitoring agency placed Anak Krakatau at alert Level 2, which is the second lowest out of four danger categories, while strongly advising people to stay at least three kilometres away from the eruption center.
How will shifting ocean tides and coastal erosion ultimately impact the persistence of the newly detected land formations near Anak Krakatau?
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